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Analysis of the sawmilling practices in the state of Durango, Mexico Zavala Zavala, David 1981

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ANALYSIS OF THE SAWMILLING PRACTICES IN THE STATE OF DURANGO, MEXICO  by  B.Sc.  DAVID ZAVALA ZAVALA E s c u e l a N a c i o n a l de A g r i c u l t u r a Chapingo, Mexico, 1972  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  in THE FACULTY OF GRADUATE  STUDIES  Department of F o r e s t r y  We accept t h i s t h e s i s as conforming to the r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1981 © David  Z a v a l a Z a v a l a , 1981  In p r e s e n t i n g  this thesis in p a r t i a l  f u l f i l m e n t of  requirements f o r an advanced degree a t the  the  University  o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e for reference  and  study.  I  further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may  be  department o r by h i s o r her  g r a n t e d by  the head o f  representatives.  my  It is  understood t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l not  be  allowed without my  permission.  Department of  PAXtTs T 2y  The U n i v e r s i t y of B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5  Date  DE-6  (2/79)  April  /?f/  Columbia  written  i  ABSTRACT  C o n t r o l of s a w m i l l i n g o p e r a t i o n s , i n c l u d i n g l o g bucking and  sawing p r o c e s s e s , i s one reasonable  shortage  problem.  This i s p a r t i c u l a r l y  practices  s o l u t i o n to the Mexican lumber so i f a v a i l a b l e techniques  improve sawmill e f f i c i e n c y can be i n c l u d e d i n normal  to  manufacturing  processes. S a w m i l l i n g a n a l y s e s were c a r r i e d out to assess the r e l a t i o n s h i p of l o g volume i n p u t to lumber volume r e c o v e r y , e v a l u a t e d i n a c t u a l nominal  dimensions.  S i x sawmills were s e l e c t e d , based  f r e q u e n t type of band h e a d r i g i n the S t a t e of Durango. r e p r e s e n t a t i v e sample s i z e of sawlogs was to a t o t a l of 870 The  used  on the most A  statistically  i n each s a w m i l l , amounting  logs.  p r o p o r t i o n of l o g volume breakdown i n t o lumber and  volumes was  analyzed.  r e s i d u e accounted T h i s suggests  and  I t was  found  byproduct  t h a t the p r o p o r t i o n of c h i p p a b l e  f o r 26 per cent of the t o t a l l o g volume  throughput.  the p o s s i b i l i t y of a l l o c a t i n g a l a r g e amount of t h i s volume  to pulp m i l l s , r a t h e r than c o n t i n u i n g present p r a c t i c e of burning  as  waste w i t h no economic r e t u r n . Sawlog types and manufacturing  lumber r e c o v e r y c h a r a c t e r i s t i c s under normal  p r o c e s s e s were i n c l u d e d i n the study.  d i f f e r e n c e of 10.32  per cent was  lumber r e c o v e r y percentages  based  Major emphasis, however, was p r a c t i c e s , lumber dimensions,  found  A  between the two  on a c t u a l and  significant e x p r e s s i o n s of  on nominal  dimensions.  g i v e n to the a n a l y s i s of l o g bucking and  sawing v a r i a t i o n ,  i n r e s p e c t to t h e i r  ii  e f f e c t on both p o t e n t i a l lumber recovery percentage and p o t e n t i a l revenue to the sawmill industry. I t was found that excessive log trim allowance resulted i n a 4.34 per cent wastage of the t o t a l l o g volume input at the trim saw.  Over  allowance i n lumber thickness dimension resulted i n a 3.55 per cent loss of the t o t a l lumber volume recovered, and sawing v a r i a t i o n accounted for a 2.76 per cent l o s s .  I t was concluded that closer c o n t r o l of sawmilling  operations to minimize poor bucking p r a c t i c e s and sawing v a r i a t i o n has s i g n i f i c a n t p o t e n t i a l f o r lumber recovery increment.  I t was also  concluded from t h i s study, that future sawmill analysis would require i n c l u s i o n of log length and sawing v a r i a t i o n i n an assessment of sawmill performance.  iii TABLE OF CONTENTS Page  ABSTRACT  i  TABLE OF CONTENTS  i i i  LIST OF TABLES  vi  LIST OF FIGURES  viii  ACKNOWLEDGEMENTS  ix  1.  INTRODUCTION  1  2.  LITERATURE SURVEY  4  2.1  Lumber Recovery  4  2.1.1  Definition  4  2.1.2  Log C h a r a c t e r i s t i c s  5  2.1.2.1  Sweepy Logs  7  2.1.2.2  Taper Logs  7  2.1.2.3  I n f e s t e d Logs  8  2.1.2.4  Logs from Dead Trees  9  2.1.2.5  C u l l Logs  9  2.1.2.6  Log Diameter  2.2  10  2.1.3  Type o f Sawmill  10  2.1.4  Cutting Patterns  13  2.1.5  Log S c a l i n g  14  2.1.6  L o g Sample S i z e  16  Log-Lumber and Byproduct P r o p o r t i o n  18  2.2.1  Volume and Weight Method  19  2.2.2  Saw K e r f  and C u t t i n g P a t t e r n s  Method  21  iv  Page  2.3  3.  4.  Quality Control  25  2.3.1  L o g Length Allowance  25  2.3.2  Lumber Dimension Allowance  26  MATERIALS AND METHODS  33  3.1  Lumber Recovery  33  3.1.1  Sawmill S e l e c t i o n  33  3.1.2  Log Sample S i z e  34  3.1.3  Log S c a l i n g  34  3.1.4  Log and Lumber G r a d i n g  35  3.1.5  S a w m i l l i n g Procedure  36  3.1.6  Lumber Y i e l d E v a l u a t i o n  36  3.2  Log-Lumber and Byproduct P r o p o r t i o n  37  3.3.  Quality Control  38  3.3.1  Log-Length Allowance  38  3.3.2  Lumber Dimension Allowance  38  3.3.2.1  Board T h i c k n e s s S e l e c t i o n  38  3.3.2.2  Sample S i z e and Board Measurements  3.3.2.3  Board Sawing. V a r i a t i o n  40  3.3.2.4  Target Size Determination  40  ...  39  RESULTS AND DISCUSSIONS  42  4.1  Raw M a t e r i a l C h a r a c t e r i s t i c s  42  4.1.1  Raw M a t e r i a l  42  4.1.2  Log Sample S i z e  43  V Page 4.2  4.3  4.4  4.5 5.  C h a r a c t e r i s t i c s of Lumber Recovery  44  4.2.1  44  Lumber Thickness  4.2.2 Lumber Grades  44  Log Volume and Lumber Volume Relationship  45  4.3.1  Lumber Recovery Percentage  45  4.3.2  Lumber Volume Allowance  46  4.3.3  Log-Lumber and Byproduct Proportion  47  Quality Control  49  4.4.1  Log Length  49  4.4.2  Sawing V a r i a t i o n  50  4.4.3  P o t e n t i a l Lumber Recovery Increment by Cutting to Target Thickness  50  4.4.4  P o t e n t i a l Lumber Recovery Increment by Reducing Sawing V a r i a t i o n  52  Economic Analysis  53  CONCLUSIONS AND RECOMMENDATIONS  55  5.1  Conclusions  55  5.2  Recommendations  57  BIBLIOGRAPHY  58  TABLES  67  FIGURES  87  vi  LIST OF TABLES Table  1  Page  P r o p o r t i o n of lumber, c h i p p a b l e r e s i d u e and sawdust by l o g diameter range and sawmill type (18, 29, 35, 37,  39, 41) 2  67  Summary of r e f e r e n c e s relationship  i n log-lumber and  byproduct 68  3  Type and number of sawmills  4  Log  5  Sawlog d i s t r i b u t i o n by l e n g t h and diameter c a t e g o r i e s  71  6  Number of l o g s and  72  7  Number of l o g s sampled to g i v e 95 per cent i n t e r v a l about the p o p u l a t i o n mean  8  9  10  i n the State of Durango  ..  grades  69 70  volumes by g r a d i n g  classes confidence  73  Volume and percentage of p i e c e s of lumber recovered thickness classes Lumber volume r e c o v e r y by grade c a t e g o r i e s (based l o g volume)  by 74  on 75  D i s t r i b u t i o n of lumber y i e l d by nominal and a c t u a l dimension of t h i c k n e s s , width, l e n g t h and volume  76  Allowance and over-allowance i n volume f o r d i f f e r e n t board t h i c k n e s s  77  Nominal, a c t u a l , and allowance volumes r e l a t e d to lumber r e c o v e r y based on a c t u a l and nominal dimension  79  13  Log-lumber and  80  14  Over-length  15  Log volume l o s t by over l e n g t h w i t h 4 and  11  12  16  17  byproducts p r o p o r t i o n s  allowance volume by l o g l e n g t h c a t e g o r i e s 6  81  inches  nominal allowance  82  Thickness boards  83  v a r i a t i o n d i s t r i b u t i o n f o r nominal 3/4-inch  Mean t h i c k n e s s - sawing v a r i a t i o n and f o r nominal 3/4 i n c h boards  target  thickness 84  vii  Table 18  19  Page Potential lumber volume recovery i n 3/4 inch nominal lumber by cutting to target thickness and by reducing sawing v a r i a t i o n  85  Potential lumber recovery i n different nominal thickness by cutting to target thickness and by reducing sawing variation  86  viii  LIST OF FIGURES Page  1  D i s t r i b u t i o n o f l o g s by diameter c l a s s e s  87  2  D i s t r i b u t i o n of l o g s by l e n g t h c l a s s e s  88  3  D i s t r i b u t i o n o f l o g s by grades and volumes  89  4  Proportion  5  of d i f f e r e n t lumber  thicknesses  produced  under nominal manufacturing c o n d i t i o n s  90  T h i c k n e s s v a r i a t i o n i n 3/4  91  i n c h nominal lumber  ix  ACKNOWLEDGEMENT  I am g r e a t l y i n debt to the Consejo N a c i o n a l (CONACYT) f o r the s c h o l a r s h i p granted U n i v e r s i t y o f B r i t i s h Columbia. of the I n s t i t u t o N a c i o n a l  de C i e n c i a y T e c n o l o g i a  d u r i n g the study  p e r i o d a t the  G r a t e f u l l y acknowledged i s the support  de I n v e s t i g a c i o n e s F o r e s t a l e s ( I N I F ) , which  allowed working time to c o l l e c t and analyze S p e c i a l thanks a r e due t o Dr. N.C. Franz  the data used i n t h i s  for directing  thesis.  the w r i t e - u p , f o r  h i s constant  a s s i s t a n c e and encouragement d u r i n g  the most d i f f i c u l t  part  of my t a s k .  Thanks a r e a l s o due t o Dr. R.W. Kennedy f o r h i s v a l u a b l e  comments and to Dr. L. Paszner f o r h i s a d v i c e and comments. Appreciated  a l s o i s the h e l p o f Mr. J . Rocha i n c o l l e c t i n g and  a n a l y z i n g the d a t a . t h e i r constant  S p e c i a l thanks a r e due to Tom and D o b r i e l a , f o r  encouragement.  1  1.  The  INTRODUCTION  sawmill i n d u s t r y i n the S t a t e of Durango, w i t h 124  represents approximately Mexico (16,  mills,  12 per cent of the t o t a l number of sawmills i n  103).  Some of the most o u t s t a n d i n g c h a r a c t e r i s t i c s  of the sawmill i n d u s t r y  are: (1)  the l a r g e number of s m a l l s i z e d m i l l s with n e a r l y 70 per cent of  them p r o c e s s i n g l e s s  s p e c i e s per (2)  than 20,000 board  f e e t of mixed pine  shift;  h i g h manpower requirements, w i t h almost 2 men f e e t o f lumber produced,  per 1000  board  or w i t h an average  o f 28 workers per  which i s r e f l e c t e d  i n the h i g h number  mill; (3)  low l e v e l of automation, of employees and  (4)  i n the equipment  low c a p i t a l investment  characteristics;  with most of the m i l l s having  just  r e q u i r e d equipment to breakdown the l o g s i n the s i m p l e s t i.e. a single single  trim  saw  (114,  have a d i r e c t e f f e c t on lumber volume  e f f i c i e n c y i s measured as the percentage from the l o g volume throughput.  a  115).  of time and on sawmill e f f i c i e n c y .  Sawmill  affecting  i n most sawmill  produced  utilization  of sawn lumber volume  Many f a c t o r s  e f f i c i e n c y are not taken i n t o account  produced  sawmill assessments,  although they have a d e f i n i t e i n f l u e n c e on lumber volume r e c o v e r e d l o g volume i n p u t , and  way,  h e a d r i g , an edger w i t h three c i r c u l a r saws and  These c h a r a c t e r i s t i c s per u n i t  the  thus, on the net revenue to the  enterprises.  from  2 Some of these factors are: (1)  the characteristics and working conditions of the equipment, particularly the headrig;  (2)  characteristics of raw material, such as log grade and log size;  (3)  characteristics of the output defined by lumber grades and lumber dimensions;  (4)  log length allowance practices and log volume lost by bucking errors;  (5)  lumber dimension allowance and excessive oversizing to avoid skip during dressing due to sawing variation (2, 4, 12, 14, 29, 30, 41, 43, 95, 101).  Log length variation and over-thickness allowance analyses generally are not included in evaluating sawmill efficiency.  It has been pointed  out by some researchers that these two factors are of great importance due to their effect on lumber volume recovery, and thus, on the revenue to the enterprises. However, lumber recovery analyses have shown the benefits from adaption of quality control programs to monitor log length and sawing variation (2, 4, 11, 13, 30, 56, 68, 76, 102, 106, 107, 115). The main purpose of this study was to determine the dimensions and volume of lumber that is produced under current industrial manufacturing practices from the various grades and sizes of logs available to sawmills in the State of Durango. A major emphasis was given to evaluate log bucking practices and their effect on lumber wasted at the trim saw.  To  cope with the lack of information on lumber thickness variation and lumber over-dimension effects on lumber recovery variation, analysis of  3 these factors was also Included as the main objective.  With the r e s u l t s  of the a n a l y s i s i t i s expected to i d e n t i f y the main sources of errors under normal sawmilling p r a c t i c e s and suggest the c o r r e c t i n g actions to increase lumber y i e l d .  4  2.  2.1  Lumber  Recovery  2.1.1  Definition  LITERATURE SURVEY  The e v a l u a t i o n of a s a w m i l l o p e r a t i o n , c o n s i d e r i n g equipment, raw m a t e r i a l c h a r a c t e r i s t i c s and lumber y i e l d , i n terms of  lumber-log  r e l a t i o n s h i p , u s u a l l y has been expressed i n t h r e e d i f f e r e n t ways: Recovery F a c t o r (LRF), Overrun, and Lumber Recovery R a t i o  Lumber  (LRR).  Lumber Recovery F a c t o r i s d e f i n e d as the nominal board f e e t of lumber r e c o v e r e d per c u b i c f o o t of l o g i n p u t to a s a w m i l l (22,  105).  Thus, LRF i s the r a t i o of nominal lumber r e c o v e r y (N) to the c u b i c of a l o g (V).  A n y t h i n g t h a t e f f e c t s N or V w i l l  i n f l u e n c e LRF  scale  (43).  Overrun i s d e f i n e d as the d i f f e r e n c e between board f o o t volume, e s t i m a t e d by v a r i o u s ( 5 1 , 55, 5 9 ) .  l o g s c a l i n g r u l e s , and the a c t u a l lumber  Overrun i s u s u a l l y expressed as a percentage  from the e q u a t i o n (61, Overrun % =  recovery  determined  110):  Lumber t a l l y - n e t s c a l e Net s c a l e  Lumber Recovery R a t i o (LRR)  x  100  [1]  i s d e f i n e d as the r a t i o of c u b i c volume  of lumber r e c o v e r e d to the c u b i c volume of l o g s sawn.  I t may,  for  c o n v e n i e n c e , be based on l o g and lumber weights w h i c h p r o v i d e an i n d i r e c t i n d i c a t i o n of volume s u b j e c t to e r r o r s due to d e n s i t y v a r i a t i o n s It  i s sometimes e x p r e s s e d as Per Cent Recovery I r r e s p e c t i v e of the way e x p r e s s e d ,  lumber-log r e l a t i o n s h i p values  (51).  (84).  the lumber r e c o v e r y or the  obtained w i l l  change a c c o r d i n g to the  5  following factors: log diameter, log length, log taper, type and number of defects, sawmill types, sawmill recovery practices or product mix, dimension of lumber produced, saw kerf, sawing variation, condition and maintenace of m i l l equipment, and the a b i l i t y , conscientiousness and fatigue level of the sawyer or other m i l l personnel (43, 101). Many studies have been carried out to determine lumber recovery associated with some of the variables l i s t e d .  The selection of the  variables mostly depend on the study objectives. Type and number of defects i n logs, combined with log diameters, log length, and taper have been used i n lumber recovery studies to formulate log grading rules. Analysis of sawmilling processes associated with equipment, cutting patterns and log characterisics, has become increasingly important i n the last 15 years.  Small logs i n particular have received much attention  recently i n lumber recovery evaluations. 2.1.2 Log Characteristics The size and volume of lumber that i s produced under current manufacturing  practices has a direct relationship with the various grades  and sizes of logs (75).  The relationship between log surface character-  i s t i c s and the lumber yield produced, usually has been used to develop log grading and tree evaluation systems (113).  In some instances, i f log  grading rules have already been developed, the lumber grade yields and recovery ratios obtained from various log types are used to update grade and volume recovery when u t i l i z a t i o n standards, manufacturing practices, quality or marketing requirements have changed (89, 93).  Lane et a l .  (75) determined the relationship between the size and volume of lumber that would be produced from various grades and sizes of Sitka spruce with  6 the  purpose of d e v e l o p i n g a t r e e g r a d i n g system.  merchantable l o g s was mix;  sample  s i z e of l o n g  not i n t e n d e d to be r e p r e s e n t a t i v e of a t y p i c a l l o g  r a t h e r , the o b j e c t i v e was  mation f o r the f u l l  The  to o b t a i n adequate  saw l o g r e c o v e r y i n f o r -  range of s i z e and q u a l i t y of timber a v a i l a b l e .  Woodfin ej: a l . (113) used lumber y i e l d v a l u e s and l o g s u r f a c e c h a r a c t e r i s t i c s to develop a l o g g r a d i n g and t r e e e v a l u a t i o n system f o r western hemlock.  The sample o f 1165  sawn l o g s y i e l d e d a c u b i c lumber  r e c o v e r y of  48 per cent of the g r o s s c u b i c volume.  Kerbes and M c i n t o s h  developed a l o g and t r e e c l a s s i f i c a t i o n  system as a g u i d e l i n e i n  p r e d i c t i n g optimum end-use  (70)  v a l u e s from spruce, based on e x t e r i o r l o g  c h a r a c t e r i s t i c s and end-product v a l u e s . i s t i c s i n the samples examined  The most important c h a r a c t e r -  were top diameter, the number of c l e a r  s i d e s and the percentage of d e f e c t due to r o t and sweep. Dobie (6) concluded a lumber  q u a l i t y study of 1086  Bailey  and  t r e m b l i n g aspen  logs  and 428 balsam p o p l a r l o g s , and developed a f o u r grade q u a l i t y system f o r both s p e c i e s a c c o r d i n g to l o g top diameter, percentage of decay and l o g sweep. net  The LRF  e f f e c t was  increased.  i n c r e a s e d w i t h diameter a t b r e a s t h e i g h t (dbh), and the i n c r e a s i n g v a l u e per c u b i c f o o t of t r e e as t r e e  To e v a l u a t e a l o g g r a d i n g system a l r e a d y  D i c k i n s o n and Prestemon  (22) e s t i m a t e d the y i e l d  (23),  established,  of hardwood  lumber grades which were expected from tanoak l o g s .  size  factory  D i c k i n s o n et^ a l .  and Prestemon e t a l . (94) w i t h s i m i l a r o b j e c t i v e s as the former  a n a l y s i s , p r e d i c t e d the y i e l d s of f a c t o r y lumber grades from P a c i f i c madrone and c h i n k a p i n l o g s . hidden c h a r a c t e r i s t i c s may grades of lumber  The  three s t u d i e s concluded t h a t ,  because  i n f l u e n c e the r e l a t i v e y i e l d of the s e v e r a l  from a l o g , l o g grades should be a p p l i e d only when a  7  l a r g e number of l o g s are being r e s u l t s may The  be  t r e e s p e c i e s and  log c h a r a c t e r i s t i c s .  q u a l i t y of sawn timber  been found that i n g e n e r a l  w i t h l o g q u a l i t y (62, defects increase  The  93)  and  l o g s to  93).  r e t u r n s d i m i n i s h as l o g  of a s p e c i f i c  l o g d e f e c t on lumber r e c o v e r y studies.  length. narrower.  The  (38) analyzed  a l s o been (12),  the e f f e c t of sweepy  In g e n e r a l ,  they found  that  same top  dimensions of lumber from sweepy l o g s were  Sawing time was  almost 40 per cent l o n g e r at  As a g e n e r a l r u l e of thumb, Dobie and M i d d l e t o n that each 0.1  has  Brown and M i l l e r  sweepy l o g s y i e l d e d l e s s lumber than s t r a i g h t l o g s of the  established  90,  (33).  l o g s on lumber grade and volume r e c o v e r e d .  headsaw.  covering  a v a i l a b l e (73,  that c o n v e r s i o n  Dobie (24), and Dobie and M i d d l e t o n  s h o r t e r and  these  the trend of lumber q u a l i t y decreases  through some lumber recovery  diameter and  evaluated  Sweepy Logs  effect  evaluated  90,  been  Some of  a v e r y l a r g e sample of t r e e s and  range of s i z e and  2.1.2.1  varying  obtained.  s t u d i e s have c o n s i d e r e d  I t has  widely  e f f e c t of l o g grades on lumber q u a l i t y y i e l d has  for different  the f u l l  c l a s s i f i e d ; otherwise,  the  (38)  i n c r e a s e i n sweep/diameter r a t i o l e d to a  r e d u c t i o n i n lumber y i e l d of about 7 per cent as compared to  straight  logs. 2.1.2.2  Taper Logs  Y i e l d of lumber per decreased  as l o g taper  c u b i c f o o t of l o g , as  increased.  s t a t e d by Dobie  In a d d i t i o n , sawing time at  headsaw per  thousand board f e e t of lumber i n c r e a s e d with  Large-taper  l o g s r e q u i r e 12 per cent more time and  log  y i e l d 5.7  (25), the  taper. per  cent  8 l e s s lumber than more c y l i n d r i c a l l o g s . (59)  Hallock  (55)  and  e s t a b l i s h e d t h a t , w i t h i n r e a s o n a b l e l i m i t s , when l o g s are  board f o o t r u l e s , the g r e a t e r operator  w i l l get  the  taper  the more lumber the  from h i s l o g investment.  On  the other  et  Hallock  al.  scaled  sawmill  hand, i f cubic  s c a l e i s used, h i s lumber y i e l d decreases per d o l l a r of investment taper  as  increases. 2.1.2.3 The  Wright  I n f e s t e d Logs  lumber y i e l d  (45).  In t h e i r  from b e e t l e - i n f e s t e d l o g s was study, the  s e l e c t i o n of  based on t r e e appearance, which i n t u r n was beetle attack.  Grade 1 t r e e s had  top, grade 3 had w i t h green and  red  bark the  a r e f l e c t i o n of time  returns.  reported  by Dobie and  from the  between sound l o g s and  On  cubic  For  was  red Trees  f e e t of tight  trees  S i m i l a r r e s u l t s were found  lower lumber y i e l d  by  for beetle-infested recovered.  from m i s t l e t o e - i n f e s t e d t r e e s i s  B r i t n e f f ( 3 2 ) , but  former s t u d i e s .  a  f o l i a g e but  at a lower l e v e l .  timber, as w e l l as a decrease i n the grade of lumber An a n a l y s i s o f lumber recovery  100  Those with no  r e t u r n s were n e g a t i v e . reported  per  and  since  grey l o o s e bark.  f o l i a g e y i e l d e d s i m i l a r values  S i n c l a i r et^ a l . (97), who  by Dobie  t r e e s to be e v a l u a t e d  grade 4 had  bark a l s o y i e l d e d p o s i t i v e r e t u r n s but sloughing  analyzed  a green top, grade 2 t r e e s had  grey t i g h t bark and  logs, with p o s i t i v e conversion  trend  by  the  r e s u l t s showed a d i f f e r e n t  the average, no  important  i n f e s t e d l o g s were found, nor  was  differences  any p a r t i c u l a r  d i f f e r e n c e associated with tree s i z e .  Differences  and  pine w i t h severe crown i n f e c t i o n s  recovery  f a c t o r s between lodgepole  of dwarf m i s t l e t o e  and  non-infested  lodgepole  pine  i n lumber grade y i e l d s  t r e e s were not  evident.  9  2.1.2.4 The according  to S n e l l g r o v e  years,  the t o t a l l o s s ranged from 28  to 71 per  T h i s statement i s a l s o confirmed 28 per  years a f t e r m o r t a l i t y .  evident  H i s a n a l y s i s showed that the longer a dead  the g r e a t e r the wood l o s s ;  that a p p r o x i m a t e l y two  (98).  f o r t r e e s dead from 0-2  material.  Trees  e f f e c t on lumber y i e l d from dead t r e e s i s q u i t e  t r e e stands cent  Logs from Dead  cent of the According  cent  f o r o l d e r dead  by Woodfin (111)  t r e e value was  lost  to Dobie and Wright  who  found  i n the  first  (46), only  l a r g e s t diameter c l a s s e s of the b e t t e r l o g q u a l i t y group i s l i k e l y y i e l d p o s i t i v e conversion of f i b e r ,  returns.  t h i s p o t e n t i a l source  the average, to be e c o n o m i c a l l y  Thus, u n l e s s  per  there i s a r e a l  the  to  scarcity  of a d d i t i o n a l supply would not appear,  on  recoverable.  a  Plank (88)  also reported  v e r y h i g h percentage of low q u a l i t y lumber from dead t r e e s as compared that obtained 2.1.2.5  from l i v e  trees.  C u l l Logs  With the o b j e c t i v e to e v a l u a t e  the p o s s i b i l i t y of p r o c e s s i n g  l o g s i n t o sawn lumber, S n e l l g r o v e and (112)  to  s t u d i e d the e f f e c t of c u l l  Darr (99), and Woodfin and  l o g s on lumber y i e l d .  cent of the gross c u b i c volume of c u l l  exceed an estimate merchantable l o g s .  lumber v a l u e s  recovered  Although 47  Both  from c u l l  of the average c o s t of l o g g i n g and The  Plank per  l o g s c o u l d be manufactured i n t o  lumber, the lumber produced would be of low grades. i n d i c a t e t h a t c h i p s and  cull  analyses l o g s would  not  processing  economic f e a s i b i l i t y of u s i n g c u l l  logs f o r  lumber manufacture i s m a r g i n a l  except i n times of extremely h i g h lumber  p r i c e s , according  studies.  to these  two  10  2.1.2.6 Log  diameter  of lumber. diameter  Log  Diameter has a d e f i n i t e r e l a t i o n s h i p w i t h q u a l i t y and  Thus, i t appears i n most g r a d i n g  i n c r e a s e s d e f e c t s g e n e r a l l y decrease  specifications  (72).  As l o g  w i t h a consequent  improvement i n grade r e c o v e r y of lumber (5, 62, 82). cases  quantity  However, i n some  (65) the r e v e r s e i s t r u e , s i n c e f o r any g i v e n grade of l o g , the  l a r g e r l o g s may diminished.  be more d e f e c t i v e and  I t has been found  i n c r e a s e s with l o g diameter,  lumber q u a l i t y recovered i s  t h a t the v o l u m e t r i c lumber y i e l d  r a n g i n g from 40 to 43 per  commonly  cent i n 10 to  12-inch l o g s , and 58 t o 65 per cent from 24 to 28-inch l o g s (19, 21, 86,  87).  A g e n e r a l concept  f o r l o g s of the same grade,  t h a t would work f o r both cases would be t h a t , there i s an i n c r e a s e i n per cent  w i t h an i n c r e a s e i n diameter decrease 2.1.3  and  recovery  f o r l o g s of the same diameter  i n r e c o v e r y w i t h a decrease Type of  85,  i n l o g grade (69,  there i s a  92).  Sawmill  In sawing l a r g e - d i a m e t e r  l o g s with  t r a d i t i o n a l headsaws,  change has o c c u r r e d w i t h r e s p e c t to r e c o v e r y and lumber, sawdust or c h i p p a b l e r e s i d u e (105).  On  product  little  distribution  the other hand, due  as  to  the tendency of d i m i n i s h i n g s u p p l i e s of h i g h q u a l i t y l o g s , a great d e a l of i n n o v a t i o n has resulting  taken p l a c e i n p r o c e s s i n g small-diameter  i n e f f e c t s on both r e c o v e r y and  The most important  product  distribution.  single factor i n successful small-log m i l l i n g i s  h i g h speed p r o c e s s i n g ( 3 5 ) .  Logs are processed  as q u i c k l y as p o s s i b l e  w i t h emphasis on speed r a t h e r than on r e c o v e r y , r e s u l t i n g recovery f o r small logs (80). throughput  estimates  logs,  i n low  lumber  When combining the lumber y i e l d and l o g  i n the c a l c u l a t i o n of volume p r o d u c t i v i t y ,  11  the throughput  has f a r g r e a t e r impact  than lumber y i e l d  (4).  s m a l l - l o g sawing methods which have taken p l a c e i n the l a s t not r e s u l t e d  i n i n c r e a s e d lumber y i e l d s from s m a l l l o g s .  Changes i n  decade have  Rather,  they  have r e s u l t e d i n i n c r e a s e d p r o d u c t i v i t y and i n c r e a s e d y i e l d s of pulp chips (29). The  percentage  class, at least  of lumber y i e l d  f o r c h i p p e r h e a d r i g s and s c r a g m i l l s  quad-band system achieved diameter  i n c r e a s e s w i t h the l o g top diameter  the g r e a t e s t lumber y i e l d  (31, 4 1 ) . The l o g i n 9 to 1 2 - i n c h top  range, whereas the c h i p p e r c a n t e r was most e f f e c t i v e  i n the 6 t o  8 - i n c h range ( 4 ) . Chip y i e l d s v a r y with sawmill p r a c t i c e s (39).  type, l o g s i z e and m i l l  cutting  Comparing band-headsaws, c i r c u l a r round-log  gang, scrag  m i l l and c h i p p e r h e a d r i g , the c h i p p e r h e a d r i g y i e l d e d a much lower percentage  o f sawdust and a c o r r e s p o n d i n g l y h i g h e r percentage  c h i p s (29, 3 5 ) .  of pulp  The average volume of sawdust o b t a i n e d with a c h i p p e r  h e a d r i g was seven per cent o f the l o g volume, or about h a l f of the normal sawdust volume from a band m i l l , and l e s s than one t h i r d of t h a t from a scrag stud m i l l .  The data r e p o r t e d i n Table No.  r e l a t i o n s h i p between sawmill and  1 shows the  type and the p r o p o r t i o n o f lumber, sawdust  c h i p s , from s m a l l l o g s ranging from 4 t o 14 inches top diameter (29,  35, 4 1 ) . The  b i g d i f f e r e n c e s i n y i e l d s a r e of course  i n sawdust and pulp  c h i p s , w i t h c h i p p e r h e a d r i g s y i e l d i n g a much lower and  higher percentage The  percentage  of sawdust  of p u l p c h i p s .  e f f e c t o f l o g l e n g t h on lumber r e c o v e r y with d i f f e r e n t  m i l l s was analyzed by Dobie and P a r r y (39). r a t i o o f board  f e e t o f lumber recovered  types of  They e s t a b l i s h e d that the  per c u b i c f o o t of l o g does not  12  change a p p r e c i a b l y i n l o g s o f 12,  16 and 20  percentage of lumber, sawdust and  solid  these  length classes.  On  McBride (35), t h a t the LRF  feet.  Thus, the same  r e s i d u e c o u l d be expected  the other hand, i t was  from  p o i n t e d out by Dobie  decreases as l o g l e n g t h i n c r e a s e s , whereas the  percentage o f c h i p volume i n c r e a s e s w i t h l o g l e n g t h .  A common  explana-  t i o n i s that the r a t i o of board f e e t to c u b i c f e e t of l o g decreases l o g l e n g t h because taper i n l o g s under 40 foot scale r u l e s . of long tapered  The  l o g s i n c o n v e n t i o n a l m i l l s , i s recovered  double-cutting  of sawmills  chips  Apparently  cubic no  (81).  Without  over a s i n g l e - c u t t i n g band headsaw i s an i n c r e a s e i n  c o s t per u n i t of output s c r a g s and I t was  chipper headrigs,  chipper  out  the p o t e n t i a l advantage of a  p r o d u c t i v i t y , which r e s u l t s i n i n c r e a s e d gross  jammed and  cut  i n s t e a d , as  i n conventional m i l l s .  found among v a r i o u s types  t a k i n g i n t o account the LRF,  log size.  i n board  d i f f e r e n c e i n the percentage of l o g volume made i n t o sawdust  from l a r g e l o g s was  headrigs,  with  Thus, the r a t i o of board f e e t of lumber per  f o o t o f l a r g e l o g s would be h i g h e r significant  f e e t i s not c o n s i d e r e d  p o t e n t i a l lumber volume, which i s normally  by the chip-and-saw m i l l .  and  (90).  log-gangs suggests t h a t throughput should  p o i n t e d out by Dobie (27)  increase  In  processed  In log-gang m i l l s ,  productive  c a p a c i t y i n c r e a s e d and  diminished  w i t h i n c r e a s i n g diameter to a c e r t a i n optimum, whereafter, reversed.  that i n  a tendency to become  c u b i c f e e t of l o g  per u n i t of time i n c r e a s e d as l o g s i z e i n c r e a s e d .  trend i n both  with  as top diameter i n c r e a s e d .  s c r a g m i l l s , however, the  processing  reduced  chipper  and by Dobie e t a l . (41)  sweep or h e a v i l y f l a r e d b u t t s had  and  s h i f t and  Sawing i n s i n g l e pass u n i t s l i k e  i n s c r a g m i l l s feed r a t e decreased  headrigs  revenue per  cost per u n i t of time the  13  In g e n e r a l , f o r any can be saved  type of s a w m i l l , c o n s i d e r a b l e p r o c e s s i n g  at the headsaw by p r o c e s s i n g the l o n g e s t l o g s .  time  However,  lumber l e n g t h s are c o n t r o l l e d by market demand (37). 2.1.4  Cutting Patterns  A l a r g e number of f a c t o r s a f f e c t any g i v e n l o g by the sawing p r o c e s s . The  first,  These f a c t o r s are of two  and  s l a b b i n g and  edging  types.  p r a c t i c e s are commonly r e c o g n i z e d .  second i n c l u d e l o g breakdown procedures  t h a t no l a r g e d i f f e r e n c e i n LRF sawing ( 7 8 ) .  For s i m i l a r q u a l i t y l o g s , LRF  sawing r e s u l t s  value recovery (4).  (56, 60).  It is  apparent  e x i s t s between grade sawing and  exceeds t h a t from grade sawing ( 1 ) . logs; l i v e  from  such as k e r f width, lumber roughness, t a r g e t s i z e , s m a l l e s t  lumber saved, The  the volume of lumber obtained  The  from l i v e  sawing  live  slightly  same r e l a t i o n i s t r u e f o r long  i n a s l i g h t l y higher per cent r e c o v e r y  I t has a l s o been e s t a b l i s h e d that l i v e  and  sawing on  the  headsaw takes 18 t o 32 per cent l e s s time on the average than grade sawing, and y i e l d s c o n s i d e r a b l y h i g h e r p r o d u c t i v i t y (9, 52). According systems may diameter  t o H a l l o c k e t a l . ( 6 0 ) , b a s i c a l l y e i g h t l o g breakdown  be used f o r c o n v e r t i n g s m a l l softwood l o g s from 5 t o  to dimension  lumber.  Short l o g s , l e s s than 16 f e e t , with a  taper of 3 i n c h e s or l e s s per 16 f e e t are best cant taper on the l o g and  20-inch  f u l l - t a p e r on the c a n t .  sawn, u s i n g  full-  Logs longer than 16  feet,  with taper over 3 i n c h e s , are best cant sawn u s i n g s p l i t - t a p e r on the l o g and  f u l l - t a p e r on the c a n t .  0.5  per cent to 6.6 In attempting  f a c e s the d i f f i c u l t  The margin of these advantages can vary  per c e n t , depending on the l o g  from  mix.  to o p t i m i z e the c o n v e r s i o n of each l o g , the sawyer task of choosing  the best of many d i f f e r e n t  sawing  14  patterns smaller  i n a l i m i t e d l e n g t h o f time.  l o g s , t h e c h o i c e of t h e r i g h t p a t t e r n i s even more d i f f i c u l t and  critical the  S i n c e LRF i s i n h e r e n t l y lower f o r  f o r small logs  (77).  sawyer may r u n v a r y i n g  Because o f pressure  for high  production  s i z e s o f l o g s through the u n i t without  changing to the a p p r o p r i a t e  patterns.  Recovery could be c u t i n h a l f by  s e l e c t i n g the wrong p a t t e r n , as f r e q u e n t l y happens f o r 7 - i n c h logs  (3).  The v a r i a b l e opening-face l i v e - s a w i n g method i s shown to be  the b e s t , i n c r e a s i n g the volume recovered cent  over t h a t o f the poorest To  s e l e c t the best  i n the sawing process best r e c o v e r y due  diameter  with  by a p p r o x i m a t e l y 10 t o 14 per  opening-face (57, 6 3 ) .  a l t e r n a t i v e cutting patterns,  the use of computer  has been u s e f u l to o b t a i n h i g h p r o d u c t i o n  small logs.  This trend w i l l  continue  and the  i n the f u t u r e  t o the i n c r e a s i n g s c a r c i t y of l a r g e q u a l i t y l o g s and the c o n t i n u a l l y  r i s i n g c o s t o f roundwood.  The investment to cover the c o s t of purchasing  computer c o n t r o l l e d equipment may be recovered  in a relatively  short  time  (63). 2.1.5 Log and  Log S c a l i n g volume i s expressed i n two common ways:  by c u b i c  of e s t i m a t i n g  s c a l i n g procedures. lumber r e c o v e r y  by board f o o t r u l e s ,  Log r u l e s a r e one of the o l d e s t means  from l o g s .  They have been used by the  lumber i n d u s t r y i n l o g t r a n s a c t i o n s by both buyers and s e l l e r s to epxress the volume o f a l o g i n terms o f the board f e e t of lumber i t i s expected to y i e l d .  There a r e more than 100 l o g r u l e s and f o r most of them  allowance must be made f o r shrinkage of boards t h a t c o u l d be recovered r u l e s estimate  and waste i n e s t i m a t i n g  (15, 65).  the volume  Most of the board f o o t s c a l e  volume somewhat lower than the a c t u a l t a l l y of lumber  resulting The  from sawing the l o g , even i n the most i n e f f i c i e n t m i l l s  d i f f e r e n c e i s commonly r e f e r r e d to as A method expected to r e p l a c e  overrun.  the board f o o t r u l e s , as a mean of  s c a l i n g l o g s , i s t h a t based on l o g volume, u s u a l l y expressed f e e t or c u b i c meters.  The  most w i d e l y  used c u b i c  formula assumes the c u b i c volume of a l o g can be the average area  of the  two  i n cubic  s c a l i n g method f o r  c a l c u l a t i n g the volume of l o g s i s the Smalian formula (55,  multiplying  (59).  59).  This  c l o s e l y estimated  by  ends of the l o g , by the l e n g t h  of  the l o g i n the same u n i t s . There i s a fundamental d i f f e r e n c e between the measurement.  B a s i c a l l y , any  s m a l l end  the o n l y v a r i a b l e s c o n s i d e r e d .  s c a l e d , both end  diameters are c o n s i d e r e d  i n c a l c u l a t i n g the volume of l o g s .  used the lumber y i e l d decreases as  (62) used the I n t e r n a t i o n a l 1/4-inch and  r u l e , and  the Smalian formula.  Snellgrove  f o r gross  c u b i c volume the  V = 0.00181 L (D Where D^  et a l . (100)  2  + D D X  2  and  the  taper  i s accounted f o r  s c a l e d by l o g r u l e s , If cubic  scale i s  increases.  l o g volume by both systems i n  s t u d i e s where the p r e c i s i o n of e s t i m a t o r s  ( 7 3 ) , and  log  When l o g s are c u b i c a l l y  increases.  taper  I t i s a l s o common to express the  al.  and  ignored  diameter of the  When l o g s are  the lumber y i e l d i n c r e a s e s as the taper  as c u b i c s c a l i n g by  systems of volume  d i f f e r e n c e s i n taper of l o g s are  when board f o o t r u l e s are used, as the i t s l e n g t h are  two  i s desired. the S c r i b n e r  Hanks and  Brisbin  l o g r u l e s , as  well  Henley and P l a n k (65), Lane ejt  used the S c r i b n e r Decimal C l o g equation:  2 + D >  [2]  2  i s the l o g s c a l i n g diameter, s m a l l end;  D  2  i s the  diameter,  16  l a r g e end,  and  L i s the l o g l e n g t h .  ( 4 8 ) , used the S c r i b n e r (65, 73, British using  100).  l o g r u l e and  Dobie and Wright  Columbia:  Woodfin (110),  the Smalian formula and  compared two  s c a l e , and  inaccuracy  c o n s e q u e n t l y the LRF  LRF,  sweep, f l a r e ,  w i l l vary  and  i t was  between s c a l e s .  defects w i l l  tend  s c a l e r s , so 2.1.6 The  Log  and  increase  effect.  of volume f o r a g i v e n  there  l o g as  there  accordingly.  Sample S i z e  105).  Commonly, to l o g s s e l e c t e d at  These l o g s are processed  f o r the r e q u i r e d data  Plank and Henley ( 8 9 ) , i n t h e i r  r e l a t e timber c h a r a c t e r i s t i c s to end  needed  in  When more p r e c i s e i n f o r m a t i o n i s  needed and more v a r i a b l e s are analyzed size usually i s increased.  the  type of i n f o r m a t i o n  a sample of 100  been used.  batches i n a normal manner (17,  the  depends on  study o b j e c t i v e s .  i n a sawing process,  random from the l o g y a r d has  s i z e of 1009  defect,  For  the s c a l e used,  f o r the same l o g c o u l d vary  the requirements of the  the LRF  the degree of  to decrease volume and  p r e c i s i o n d e s i r e d , c o s t l i m i t a t i o n s , and  evaluate  Inadequate  concluded by Dobie and Wright (43), t h a t  that the LRF  scale,  Over-generous allowances  sample s i z e r e q u i r e d f o r a n a l y s i s of LRF  to s a t i s f y  factor.  deductions w i l l have the o p p o s i t e  c o u l d be as many d i f f e r e n t e s t i m a t e s are  s c a l e s used i n  firmwood c u b i c  i n assessing  of volume w i l l vary with  whereas c o n s e r v a t i v e In g e n e r a l  cubic  Martin  listed  i n measurement were the main l i m i t a t i o n s found.  d e f e c t i v e logs estimates  for  the  the lumber r e c o v e r y  deductions f o r b u t t - f l a r e , d i f f i c u l t i e s and  Fahey and  the c u b i c volume equation  (43)  the lumber c u b i c  and  product y i e l d v a l u e s ,  merchantable l o g s to cover the  full  the  sample  study to used a  range of l o g  sample  size  a v a i l a b l e even when samples were not r e p r e s e n t a t i v e of a t y p i c a l l o g  mix.  17  With s i m i l a r purpose Henley and P l a n k (65)  s e l e c t e d a sample s i z e of  428  l o g s t h a t were r e p r e s e n t a t i v e of the a v a i l a b l e t r e e c h a r a c t e r i s t i c s . Pong and  Fahey (93) used a sample s i z e of 1126  r e p r e s e n t a t i v e of the  full  range of s i z e and  ( 5 ) , w i t h a sample s i z e of 609 diameter, o b t a i n e d  aspen l o g s , w h i l e M u e l l e r i n diameter from 7 to 24  and  was  q u a l i t y of the  l o g s , ranging  a representative  l o g s which  from 7 to 17  logs.  inches  sample s i z e of s t r a i g h t  in  trembling  Bager (82), f o r merchantable l o g s  i n c h e s , needed 675  Bailey  ranging  logs.  Dobie e t a l . (34), w i t h a sample s i z e of 2585, r e p r e s e n t a t i v e of major commercial s p e c i e s , compared the d i f f e r e n c e between the c u b i c s c a l e and  the firmwood c u b i c s c a l e .  the lumber y i e l d and  recovery  two  l o g s c a l i n g and  and  4974 sawn-length l o g s .  (74)  lumber to determine  r a t i o s f o r old-growth D o u g l a s - f i r , u s i n g  p r a c t i c e s , processed  2980 woods-length l o g s  With d i f f e r e n t o b j e c t i v e s Lane and  Woodfin  s e l e c t e d a sample s i z e of 4009 commercial sawlogs to e v a l u a t e  yield  by To  lumber  grade. satisfy statistical  selected according The  grading  Lane et: a l . (73),  the  requirements, the  sample s i z e should  to the v a r i a t i o n of the q u a n t i t y estimated  r e q u i r e d number of l o g s i s determined by the  be  (26,  54).  formula:  2 2 N -  [3]  E o  Where N i s the  sample s i z e , s  the a p p r o p r i a t e v a l u e  i s the p o p u l a t i o n v a r i a n c e ,  of Student's t , and E i s the a l l o w a b l e  the volume v a r i a t i o n of the l o g p o p u l a t i o n  i s unknown, then a  t is  error.  If  preliminary  18 sample of 60 l o g s should the  be  taken at random to determine the v a r i a n c e  formula  v 2 .  Where Z x ments, (£x)  lExl  i s the  z  2  sum  of squared v a l u e s  i s the square of the sum  interior  l o g m i l l s ranges from 249  ranges from 210  to 779.  of a l l i n d i v i d u a l measure  of a l l measurements.  procedure Dobie (26) found that i n B.C.  For 95 per cent  to 343  l o g s and  Dobie and Warren (42)  confidence  mean LRF,  about 100  should be  sampled.  Log-Lumber and  Using  this  for coastal  reported  sawmills  that the number  as diameter  increased.  l i m i t s , w i t h h a l f - w i d t h of 5 per cent of  l o g s of the 4 - i n c h  Byproduct  c l a s s and  60 of the 10-inch  the class  Proportion  Sawmill r e s i d u e s such as s l a b s , edgings, that were once wasted, are now  -  the sample s i z e f o r s m a l l  of l o g s i n two-inch diameter c l a s s e s d i m i n i s h e d  2.2  by  being  t r i m s , sawdust and  s o l d f o r pulp c h i p s , f i b e r  p a r t i c l e wood p r o d u c t s , mulches, s o i l amenders and  bark, and  ground c o v e r s .  Wood-  c h i p s are s o l d to pulp m i l l s , f i b e r or p a r t i c l e board p l a n t s f o r processing  i n t o paper or boards; bark r e s i d u e i s screened,  marketed as s o i l amenders, mulch and mulching and 85,  86,  ground c o v e r s ,  washed  and  sawdust i s s o l d f o r  l i v e s t o c k bedding or burned at the m i l l as f u e l  (19, 20,  21,  87).  Because of the i n c r e a s i n g value a t t e n t i o n has  been g i v e n  Factors a f f e c t i n g  of sawmill  to e s t i m a t i n g  the lumber y i e l d  residues,  increased  the amount of each byproduct.  of l o g input a l s o a f f e c t  the y i e l d  of  19  sawmill r e s i d u e s : l o g diameter, type, saw k e r f , dimension  log quality,  scaling practices,  of lumber produced and  sawmill  sawmill  recovery  p r a c t i c e s , among o t h e r s . 2.2.1  Volume and Weight Method  U s i n g a band headsaw to process diameter  from 9 to 20.4-inch,  y i e l d of lumber and byproduct with and without  bark,  and  P h i l l i p s and  The  Schroeder  from the sawlogs.  scaled p r i o r  band headsaw i n t o lumber of unusual inches, f o r export.  s h o r t l e a f pine l o g s , ranging i n (87) determined  Each l o g was  to sawing i n a 3/16  dimension,  weighed  inch kerf  1 by 5 i n c h e s and  p r o p o r t i o n of the d i f f e r e n t  10 per cent sawdust.  i n small t r e e s to 58 were determined weight was  Lumber y i e l d  per cent i n l a r g e diameter  by weighing  determined  l o g s v a r y i n g i n diameter  from 11.9  a band headsaw i n t o grade y i e l d of wane, and  i n c r e a s e d from 43 per trees.  The  to 25.6  of 4/4  and  (85, 86)  studied  inches.  He  5/4  s c a l i n g diameter  i n c r e a s e d lumber y i e l d  c e n t ; 25 per cent of s m a l l diameter compared to o n l y 16.4  10 per cent  i n c r e a s e d from 46.3  them on  cent sawdust. to 61  As  per  l o g s went i n t o c h i p p a b l e r e s i d u e  per cent f o r l a r g e diameter  logs.  The  of  C l a r k (19) and C l a r k e t a l . (21), sampled 230 to 28.4  constant over  percentage  sawdust remained r e l a t i v e l y  p o p l a r sawlogs r a n g i n g from 11.7  and  i n c h lumber with a minimum  of bark r e s i d u e and t r e e diameters.  Sawdust  black-oak  processed  found a r e l a t i o n o f 55 per cent lumber, 20 per  c h i p p a b l e r e s i d u e , 15 per cent bark r e s i d u e and  cent  percentages  by s u b s t r a c t i n g weight of c h i p p a b l e r e s i d u e Phillips  was:  bark  the c h i p p a b l e r e s i d u e from each l o g .  lumber from debarked l o g weight.  1 by 3  l o g components  54 per cent lumber, 26 per cent c h i p p a b l e r e s i d u e , 10 per cent r e s i d u e and  the  i n c h e s i n diameter.  the range  The  yellow logs  20  were weighed w i t h and without  bark and  prior  i n c h lumber, with a 3/16  to sawing them i n t o 4/4  headsaw.  the Smalian  i n c h k e r f band  13 per cent  sawdust was  t h a t c h i p p a b l e r e s i d u e decreased  found.  i n s m a l l l o g s to 12 per cent i n l a r g e l o g s . tree size increased, ranging  Using a c o n v e n t i o n a l 5/16  21 i n c h e s i n t o 4/4  from 17 per  Lumber y i e l d  cent  i n c r e a s e d as trees  trees.  inch kerf c i r c u l a r  saw  h e a d r i g , C l a r k and  s l a s h pine sawlogs ranging i n diameter  and 8/4  per  They a l s o  from 42 per cent i n 12-inch diameter  to 59 per cent i n 2 8 - i n c h diameter  (20) processed  18  from 29 per cent i n small l o g s to  16 per cent i n l a r g e l o g s , w h i l e bark r e s i d u e decreased  Taras  formula  A p r o p o r t i o n o f 54 per cent lumber, 15 per cent bark,  cent c h i p p a b l e r e s i d u e and found  s c a l e d by  i n c h lumber and  determined  from 9.6  to  a r e l a t i o n of 51  per cent lumber, 22 per cent c h i p p a b l e r e s i d u e , 10 per cent bark r e s i d u e and  17 per cent sawdust.  s i z e up to 18 i n c h e s and from 5.3  They a l s o found then decreased  i n 12-inch d.b.h. t r e e s to 6.5  18-inch d.b.h. t r e e s , and  the LRF  slightly. board  the average was  6.1.  i n c r e a s e d with t r e e The  average LRF  f e e t per c u b i c f o o t i n Taras e t a l . (104),  merchantable stems of l o b l o l l y pine r a n g i n g i n diameter 19.4-inch board  d.b.h., and  processed  4/4  per cent bark and  i n c h boards.  Lumber y i e l d  13.6 8/4  decreased,  trees.  Chippable  and  per  per cent sawdust from i n c h dimension  and  12  i n c r e a s e d as t r e e s i z e  i n c r e a s e d , r a n g i n g from about 37 per cent i n 10-inch per cent i n 20-inch  to  per cent lumber, 28.5  the sawlogs; 88 per cent of the lumber cut was per cent was  from 9.8  with  on a c i r c u l a r headsaw i n t o dimension  lumber, r e p o r t e d a p r o p o r t i o n of 50.3  cent c h i p p a b l e r e s i d u e , 7.6  ranged  t r e e s to about  55  r e s i d u e on the other hand,  r a n g i n g from a h i g h of 39 per cent i n 10-inch  t r e e s to 25  per  21  cent i n 20-inch  trees.  Bark y i e l d decreased  ranging from 9 to 7 per c e n t .  as t r e e s i z e i n c r e a s e d  Sawdust weight decreased  i n c r e a s i n g t r e e s i z e r a n g i n g from 14.4  slightly  per cent i n s m a l l t r e e s to  per cent i n l a r g e t r e e s .  Fahey and Hunt (50) s t u d i e d grand  l o g s , r a n g i n g i n diameter  from 4 to 14 inches processed  and  from 4 to 12 i n c h e s a t a c h i p p e r h e a d r i g , producing  b e t t e r grade lumber. and  They found  c h i p p a b l e r e s i d u e was  53.6  used to c o l l e c t  13.3,  the c h i p s and  from the oven-dry w e i g h t s . statement  35.1  solid  Schroeder  t h a t weight- s c a l i n g  f i r thinning  at a band m i l l standard  per cent, and 49.5, An  p r o d u c t s of pine saw  r e s i d u e volume was  et^ al.  headsaw which had  a 5/16  the p r o p o r t i o n was  trees.  Lumber was  i n c h k e r f , i n t o 4/4  f o r 10-inch  Saw  t a b l e s based  primary  produced on a  and 8/4  circular  i n c h t h i c k n e s s and  i n c r e a s e d w i t h diameter  from sawlogs was  the primary  to determine the p r o p o r t i o n  followed.  Regression  equations  the weight or the volume, or both, products.  K e r f and C u t t i n g P a t t e r n s Method  A d i f f e r e n t approach to determine lumber volume and p r o p o r t i o n from sawlogs was  from  f o r 20-inch t r e e s .  to p r e d i c t e i t h e r  merchantable stems and 2.2.2  LRF  s t u d i e s a s i m i l a r procedure  of lumber and byproducts were formulated  other  and  54 per cent lumber, 26 per cent c h i p p a b l e r e s i d u e s , 16  t r e e s t o 6.84  In a l l these  44.1  determined  i s the accepted method of buying  per cent sawdust and 9 per cent bark. 5.80  5.4,  (96), a c c o r d i n g to the  the p r o p o r t i o n of lumber and  timber  and  empty c h i p b i n  s e l l i n g pine l o g s i n the southern U n i t e d S t a t e s , formulated on weights to e s t i m a t e  12.9  t h a t the p r o p o r t i o n of lumber, sawdust  per c e n t , r e s p e c t i v e l y , f o r the two machine c e n t e r s . was  with  byproduct  used i n the f o l l o w i n g s t u d i e s .  Sawdust  from  ,  22 volume was determined by using the average saw kerf and the computed surface area of the rough green lumber from each l o g . Chippable product volume was determined by subtracting the lumber and sawdust volume from the gross cubic l o g volume. Using band headsaws to process old-growth coastal Douglas-fir ranging i n diameter from 5 t o 67 inches, Lane j2t a l . (73) employed an average saw kerf thickness for each m i l l which was producing optimum values of board, dimension, select and shop lumber.  They found that  about 63 to 64 per cent of the cubic content of the log was manufactured i n t o rough green lumber of which approximately 25% was l o s t as planer shavings and shrinkage.  Henley and Plank (65) used a band headsaw with  an assumed average saw kerf of 7/32 inch and computed cross s e c t i o n a l area of the lumber i n each 6 to 34-inch log of Engelmann spruce. When producing nominal 2 by 4, 2 by 6 and 1 inch boards, they found that an average trim allowance of 6 inches would increase the gross cubic volume by 3.3 per cent and there would be a corresponding increase i n the volume of residues.  Pong and Fahey (93), applying a saw kerf of 8/32 inch i n a  band headsaw processed red and white f i r ranging i n diameter from 7 to 50 inches.  They manufactured s e l e c t , shop, common and dimension lumber, i n  a s i m i l a r way to the former studies, and tabulated the varying proportions of lumber, sawdust and chippable residue from d i f f e r e n t log diameter classes.  Snellgrove et a l .  (100) with a band headsaw and an  average saw kerf of 0.25 i n c h , processed low grade coastal Douglas-fir logs into board, dimension, and select items. He found that about 62.5 per cent of the cubic content of the sawn-length logs was manufactured i n t o rough green lumber and about 8 per cent of the volume was sawdust.  23  The  remaining 2 9.5  residue. 6-inch  per cent c u b i c content of the l o g s was  They a l s o found  t r i m allowance,  t h a t the r e s i d u e volume w i l l  considered  i n c r e a s e with a  which i n c r e a s e s the gross c u b i c volume of  average l o g by 24 per c e n t .  mill  the  Lane et^ _ a l . ( 7 5 ) , used a s i n g l e cut bandsaw  w i t h an average saw  k e r f o f 0.25  i n c h , to process  S i t k a spruce  r a n g i n g i n diameter  from 6 to 5 6 - i n c h i n t o rough green c a n t s f o r e x p o r t .  They determined  the p r o p o r t i o n of lumber,. sawdust and  by l o g diameter  class.  chippable residue  Fahey and M a r t i n (48) s t u d i e d 292  D o u g l a s - f i r l o g s r a n g i n g i n diameter  second growth  from 7 to 44 i n c h e s , using a  cut bandsaw produced lumber of which' 49 per cent was  4 i n c h e s or  They r e p o r t e d t h a t the p r o p o r t i o n of lumber, sawdust and r e s i d u e was  to sawdust, 9 per cent, was  cent of 4 - i n c h dimension approximately  thicker.  The  p o r t i o n of  to the high  lumber produced i n t h i s study.  per  Normally  11 to 12 per cent of the l o g volume becomes sawdust.  P r o c e s s i n g s m a l l diameter i n c h k e r f f o r the headsaw and to 14 i n c h e s .  low due  double  chippable  60 per c e n t , 9 and 31 per c e n t , r e s p e c t i v e l y .  the l o g converted  logs  They determined  i n lumber, sawdust and o v e r a l l r e c o v e r y was  l o g s , Kerbes and Mcintosh edger w i t h l o g s ranging  i n diameter  3/8  from 4  the p r o p o r t i o n of sawlog volume converted  s o l i d r e s i d u e f o r each diameter  61,  (69) u s i n g  log class.  19 and 20 per cent of lumber, sawdust  The  and  chippable residue, r e s p e c t i v e l y . * Since c u b i c s c a l i n g  i s becoming more common i n sawmill  (61), i n h i s a n a l y s i s to p r e d i c t  the lumber and  10 s p e c i e s of hardwood t r e e s , c a l c u l a t e d  s t u d i e s Hanks  c h i p p a b l e r e s i d u e s from  sawmill r e s i d u e volume i n  *The p r e v i o u s i n f o r m a t i o n i n c l u d i n g s e c t i o n 2.2.1 T a b l e 2.  has  been summarized i n  24  cubic and  f e e t f o r each t r e e by s u b t r a c t i n g  the c u b i c - f o o t volume of lumber  sawdust from the g r o s s c u b i c - f o o t volume of saw  l o g s ranging  i n c h and  lumber w i t h t h i c k n e s s  10/16  of 4/4,  presented p r e d i c t i o n e q u a t i o n s and  and  (8), i n contrast  Scribner  s l a b s and  to the  6/4  8/4  inch.  t a b l e s to estimate the  gross  s o l i d wood r e s i d u e s .  former study, used the  In t h e i r a n a l y s i s i t was  byproduct v a r i e s a c c o r d i n g  to the l e n g t h of the l o g .  thus,  the p r o p o r t i o n  i n c r e a s e s w i t h l o g l e n g t h by S c r i b n e r Rule.  Rule but  defined  by  proportion as being  of lumber and  from 4 to 15  f o r t r i m saws, 1/8  the  cubic  International  logs,  top diameter, changes a c c o r d i n g  characteristics. 41).  Saw  f o r twin band saws and  These r e l a t i o n s are  k e r f s used to c a l c u l a t e  i n c h f o r edgers, 7/32  1/4  i n c h f o r scrag  that, for c i r c u l a r  inch  saws.  sawmills,  the  contents t h a t develop from green, debarked l o g s  per c e n t ; k e r f 16  to 21  to  i n c h f o r c i r c u l a r headsaws,  gang saws, 5/16  (105)  the  byproducts from small-diameter  (18, 2 9, 37,  been g e n e r a l i z e d  t o 47  decreases by  Rule.  inches  processing  i n c h f o r band saws and  lumber 37  to lumber  the I n t e r n a t i o n a l Rule, but  the volume of sawdust produced were 11/32  appropriate  variation  allowance f o r such  of l o g volume converted  the S c r i b n e r  c l e a r l y shown i n T a b l e 1,  I t has  International  This  edgings d e c r e a s e s s l i g h t l y with l o g l e n g t h by  the type of sawmill and  3/16  Bennett  Consequently, the percentage of the l o g volume going i n t o  increases  The  He  found that the volume of  r e s u l t s because the I n t e r n a t i o n a l Rule makes no  s l a b s and  and  l o g r u l e s to e s t i m a t e the p o r t i o n of a l o g that goes i n t o  edgings.  increase;  and  inch respectively,  5/4,  c u b i c - f o o t y i e l d s of lumber, sawdust and and L l o y d  The  i n diameter from 10 to 3 0 - i n c h , were sawn i n c i r c u l a r  band m i l l s w i t h k e r f s of 7/16 processing  log material.  per cent;  c h i p s 17  to 35  are: per  25 cent; and planer shavings 12 to 18 per cent. sawing v a r i a t i o n and planning allowance. the same v a r i a b l e s are:  This includes o v e r s i z i n g ,  The f i g u r e s for bandmills with  lumber 44 to 53 per cent, k e r f 12 to 15 per  cent; chips 20 to 29 per cent, and planer shavings 11 to 15 per cent. A general procedure i s described by Dobie (26) to determine sawdust volume according to log breakdown patterns and the various pieces of equipment i n a m i l l .  The saw cuts are recorded and the thickness of  pieces removed at each machine center either measured or estimated.  Over  a period of time s u f f i c i e n t data can be gathered to give sawdust y i e l d for each diameter c l a s s at each machine center for each processing pattern used.  This procedure increases i n complexity as the number of  processing stages and c u t t i n g patterns grow. A d i f f e r e n t approach i s described by Steele and Hallock (101), analyzing the methods used to c a l c u l a t e the volume of byproduct i n the sawing process.  They concluded that most of the methods have one  weakness i n common; r e l a t i v e l y few of the v a r i a b l e s that can a f f e c t residue volumes are considered.  An accurate p r e d i c t i o n of sawmill  residue production requires i n c l u d i n g i n the a n a l y s i s a l l the v a r i a b l e s that can a f f e c t t h i s production. suggested  important  A geometric model i s  to c a l c u l a t e volume of green lumber, dry lumber, green c h i p s ,  green sawdust and dry planer shavings. 2.3  Q u a l i t y Control 2.3.1  Log Length Allowance  The most common lengths for logs processed into sawn lumber are 8, 10, 12, 14, 16, 18 and 20 feet i n nominal dimension, with an a d d i t i o n a l  o v e r - l e n g t h r a n g i n g from 4 t o 12 i n c h e s (95).  Log l e n g t h v a r i a t i o n has  h i g h impact  on l o g volume l o s t and on v a l u e r e t u r n on investment  material.  When the a c t u a l dimension  dimension,  exceeds s i g n i f i c a n t l y  of raw  the nominal  the lumber wasted a t the t r i m saw i s g r e a t l y i n c r e a s e d .  (30), i n h i s a n a l y s i s o f 13 c o a s t a l sawmills i n B.C., found  Dobie  t h a t 3.1 per  cent of the t o t a l l o g volume processed was l o s t  due to an over  allowance  of l o g l e n g t h c o n s i d e r i n g 6-inch  f o r long logs.  Aune and  Lefebvre  t r i m allowance  ( 4 ) , i n t h e i r a n a l y s i s o f 72 s m a l l l o g sawmills i n the i n t e r i o r  of B r i t i s h Columbia, r e p o r t e d a l o g volume l o s t o f 1.8 per cent due to over l e n g t h of the l o g s .  Z a v a l a (115)  i n h i s r e p o r t of the  c h a r a c t e r i z a t i o n o f the s a w m i l l i n g i n d u s t r y i n the S t a t e o f Durango, found  that 3.2 per cent of the l o g volume processed was l o s t  over l e n g t h . an allowance  However, he c o n s i d e r e d , as a common l o g bucking of 4 i n c h e s of the nominal  l o g dimension  2.3.2  Lumber Dimension  logs.  f o r c u t t i n g and s e l l i n g  from 4 t o 12 i n c h e s i n width and from 4 t o 20 f e e t ments of 2 i n c h e s and 2 f e e t , r e s p e c t i v e l y .  f i n i s h machining  ranges  (4) c o n s i d e r e d 6  Allowance  The most common dimensions  i n c h t o 2 i n c h e s i n nominal  practice,  f o r any g i v e n l o g  l e n g t h c a t e g o r y , w h i l e Dobie (30) and Aune and L e f e b v r e inches as a l l o w a b l e l e n g t h f o r l o n g  due to an  dimension.  sawn lumber range  i n length, i n incre-  Thickness ranges  from 1/2  Rough dry lumber allowance f o r  from 1/4 t o 1/8 i n c h i n t h i c k n e s s , a t l e a s t 1/2  i n c h i n width, and 3 i n c h e s i n l e n g t h (95).  27  Among the few s t u d i e s i n lumber dimension a n a l y s i s Rodriquez (95), p r o c e s s i n g 755 l o g s i n 7 s a w m i l l s , r e p o r t e d that the a c t u a l volume l o s t , as a r e s u l t of o v e r - a l l o w a n c e , ranged nominal volume.  from 20 t o 34 per cent of the  Cardenas (17) e s t a b l i s h e d  the minimal t h i c k n e s s  dimension and volume allowance f o r sawn lumber most commonly p r o c e s s e d . For 1/2, 3/4, 4/4, 6/4 and 8/4 i n c h , the c o r r e s p o n d i n g lumber t h i c k n e s s should be 16, 22, 28, 41 and 54 m i l l i m e t e r s , y i e l d i n g a v o l u m e t r i c allowance f o r f i n i s h i n g The allowance  of 40, 30, 22, 15 and 8 per c e n t , r e s p e c t i v e l y .  i n dimension  i s a common p r a c t i c e f o r p r o d u c t i o n and  c o m m e r c i a l i z a t i o n o f sawn lumber, due to the volume l o s t  by sawing  v a r i a t i o n , by p l a n i n g , and by s h r i n k a g e from green t o d r y dimension. Minimum s i z e requirements the r e q u i r e d f i n a l  f o r rough green lumber are determined  d r y - d r e s s e d lumber dimension  p l a n i n g and s h r i n k a g e .  and adding allowances f o r  The t a r g e t lumber s i z e i s determined  t i o n a l allowance which r e p r e s e n t s sawing v a r i a t i o n . sawn lumber to compensate f o r t h i c k n e s s sawing  by t a k i n g  by a d d i -  Over allowance i n  variation, increases  lumber volume l o s t which r e s u l t s i n lower lumber r e c o v e r y . Sawing v a r i a t i o n i s a measure of the mechanical p r e c i s i o n i n manufacturing  lumber t h i c k n e s s and widths  (102).  machine o p e r a t o r s and maintenance of machining  Skill  and t r a i n i n g of  c o n d i t i o n s have a d i r e c t  i n f l u e n c e on sawing v a r i a t i o n and on p l a n i n g v a r i a t i o n of rough I t i s , t h e r e f o r e , p o s s i b l e to c o n t r o l and reduce variations  lumber.  these two types of  (2, 11, 13, 14, 106, 107).  Sawing v a r i a t i o n can be q u i t e s i g n i f i c a n t as i n d i c a t e d M c i n t o s h (69) who r e p o r t e d i n t h e i r  by Kerbes and  study t h a t , i n the a c t u a l c o n v e r s i o n  of t r e e s to f i n i s h e d lumber, o v e r s i z e amounted to 10 per cent of the  28  rough-green lumber volume.  The wasted volume was  a v o l u m e t r i c - s h r i n k a g e f a c t o r of 6.8 obtaining of 1/8  a s i m i l a r allowance lumber l o s t due  was  1/8  used  by a p p l y i n g  per cent to the green lumber volume,  the volume a t 12 per cent m o i s t u r e  i n c h i n t h i c k n e s s and  determined  content.  A sawing  accuracy  i n c h i n width were allowed i n sawing  for planing.  The  potential  and  rough-green  to p l a n e r shavings amounted to 25 per cent of rough  green  lumber volume. In a s i m i l a r study M u e l l e r and Bager ( 8 2 ) , w i t h a sample of boards, 4/4  i n c h i n t h i c k n e s s , t a k i n g three t h i c k n e s s measurements along  the l e n g t h of the boards, most f r e q u e n t l y was accounted  194  found  t h a t the average  thickness that occurred  the t a r g e t t h i c k n e s s o f 1.063  f o r 25 per cent of the lumber sampled.  (34/32) i n c h , which S t e r n et_ al.  t h e i r e v a l u a t i o n of sawing v a r i a t i o n and lumber o v e r s i z i n g  (102) i n  found  tremendous d i f f e r e n c e s between m i l l s ; sawing v a r i a t i o n ranged  from 0.025,  (8/32) t o 0.534, (17/32) i n c h , w i t h a mean v a r i a t i o n of 0.165, (5/32) i n c h . In a study to e v a l u a t e the performance of sawing v a r i a t i o n of 13 sawmills i n B r i t i s h Columbia, V a l g (106) o p e r a t i n g under s t a t i s t i c a l o f 1.536  c o n t r o l and  t o 2.228 i n c h , w i t h an average  c o u l d be reduced  found  t h a t o n l y one m i l l  the r e s t of them had range o f 0.25  was  a variation  (8/32) i n c h which  to 0.094 (3/32) i n c h i n most of the sawmills s t u d i e d .  He a l s o found no c o r r e l a t i o n between m i l l d i d any p a r t i c u l a r h e a d r i g type  s i z e and  sawing p r e c i s i o n ;  seem to dominate over  the o t h e r .  With a sample s i z e of 25 p i e c e s of lumber from each of the sawmills a n a l y z e d , Bramhall v a r i a t i o n from 0.03,  and M c l n t y r e  (11) found  (1/32) t o 0.320, (10/32) i n c h .  the r e l a t i o n between sawing v a r i a t i o n and  nor  22  a range of sawing They a l s o  determined  the p r o p o r t i o n of u n d e r s i z e d  29  p i e c e s among the d i f f e r e n t was  attributed  v a r i a t i o n was  sawmills s t u d i e d .  The between-board  to e r r o r s on the setworks and w i t h i n - b o a r d  r e s p o n s i b l e f o r most of the v a r i a b i l i t y  t h e r e f o r e , the setwork would have been the prime t a r g e t in  controlling  sawing  due to v i b r a t i o n and wandering of the sawblade.  between boards was  sawing  variation  Variation  i n thickness;  for  improvement  variation.  To a n a l y z e the p o s s i b l e e f f e c t on sawing v a r i a t i o n , due to technol o g i c a l changes adopted by the s a w m i l l i n g i n d u s t r y 10 years a f t e r h i s first  study, V a l g  (107) r e p o r t e d a sawing v a r i a t i o n a n a l y s i s i n 8  s a w m i l l s , some of which were covered i n h i s f i r s t significant  improvements  study.  He found no  i n range sawing v a r i a t i o n compared  to h i s f i r s t  a n a l y s i s ; that i s , from 0.063, (2/32) t o 0.437, (14/32) i n c h , w i t h an average range o f 0.2362, (8/32) i n c h ; t h i s range r e p r e s e n t e d 25 per cent of  the t o t a l sawn lumber.  of  0.2206, (7/32) i n c h , which i s an i n s i g n i f i c a n t  found i n h i s f i r s t  In h i s l a t e s t  an average sawing v a r i a t i o n o f 0.146 USA were c o n s i d e r e d t o g e t h e r . best m i l l  change  from the range  analysis.  Compiling i n f o r m a t i o n from d i f f e r e n t  the  study he found a range v a r i a t i o n  s t u d i e s , H a l l o c k (56) r e p o r t e d  i n c h when a l l the sawmills i n the  The range was  from 0.234, (7/32) i n c h i n  s t u d i e d t o 0.496, (16/32) i n c h i n the poorest one.  No  s i g n i f i c a n t d i f f e r e n c e s i n sawing v a r i a t i o n were found between geographic areas. the  D e f i n i n g o v e r s i z i n g i n excess of what i s needed as p o s i t i v e when  boards are l a r g e r than t h e o r e t i c a l l y n e c e s s a r y and n e g a t i v e when the  p i e c e s are s m a l l e r , p o s i t i v e o v e r s i z i n g averaged 0.077 i n c h and v a r i e d from 0 t o 0.545 i n c h . from 0 t o 0.392 i n c h .  N e g a t i v e o v e r s i z i n g averaged 0.085 i n c h and ranged  30  An excess o f sawing v a r i a t i o n or any o v e r s i z i n g w i l l lumber r e c o v e r y . lumber y i e l d LRF  by 0.10.  Reducing unfavourable  significantly  (105).  By r e d u c i n g  excessive  i n c h lumber, LRF w i l l  result  sawing f a c t o r s w i l l  Accurate  bucking  i n c r e a s e the  of logs w i l l  i n c r e a s e by 0.30.  Avoiding  sawing v a r i a t i o n i n  i n c r e a s e LRF by 0.60, while  h o l d i n g o v e r s i z i n g t o 5/32 i n c h on 4/4 lumber w i l l  i n c r e a s e LRF by 0.45.  LRF  can be f u r t h e r i n c r e a s e d by 1.0 through m i n i m i z i n g  and  trimming.  slabbing,  Due to the e f f e c t of sawing v a r i a t i o n on lumber r e c o v e r y , v a r i a t i o n a n a l y s i s , by means o f p e r i o d i c a l o b s e r v a t i o n s i s becoming more common i n the s a w m i l l i n g c o l l e c t and analyze  the data  increase  p l a n i n g allowance to 3/32 i n c h on 4/4  excess o f 1/8 i n c h on 4/4 i n c h lumber w i l l  to  i n lower  industry.  edging  thickness  and measurements,  The a d d i t i o n a l cost  i s w e l l paid f o r once the a s s i g n a b l e  causes of the sawing v a r i a t i o n are e l i m i n a t e d . A procedure to analyze (108),  determining  the sawing v a r i a t i o n i s d e s c r i b e d by Warren  and e v a l u a t i n g t h i c k n e s s v a r i a t i o n between boards and  w i t h i n boards by one-way a n a l y s i s of v a r i a n c e .  He a l s o determined the  r e q u i r e d sample s i z e f o r sawing v a r i a t i o n s t u d i e s , ranging boards, and the t a r g e t t h i c k n e s s f o r s p e c i f i e d v a l u e s  from 50 t o 250  f o r the two  of v a r i a t i o n , to g e t no more than 5 per cent of the p r o d u c t i o n  types  with  skip  values. Using  a d i f f e r e n t approach from Warren, Whitehead  (109) d e s c r i b e d  the procedure to develop a lumber s i z e c o n t r o l program to reduce the sawing v a r i a t i o n .  The d i f f e r e n t  steps needed f o r the a n a l y s i s , i n c l u d i n g  c o l l e c t i o n o f d a t a , e v a l u a t i o n and i n t e r p r e t a t i o n of i n f o r m a t i o n are described.  31  To compute the t h i c k n e s s v a r i a t i o n between boards, boards, he used  Where Sw,  the f o l l o w i n g formulas:  i s the w i t h i n - b o a r d  standard d e v i a t i o n , i t i s a measure of  the s i z e v a r i a t i o n t h a t o c c u r s a l o n g the boards; standard d e v i a t i o n , measures the s i z e v a r i a t i o n boards;  St i s the t o t a l  subgroup s i z e f a c t o r  determined  Sb i s the between-board that occurs between  sawing standard d e v i a t i o n .  of w i t h i n - b o a r d measurements and  Target  and w i t h i n  Rw  and Rb  ranges  between board measurements; d2 i s a  t h a t c o n v e r t s range i n t o standard d e v i a t i o n .  s i z e t h i c k n e s s or optimum t h i c k n e s s dimension by  are  can  be  the f o l l o w i n g formula:  T = (St x K) + SPF  [8]  Where T i s the green t h a t determines s i z e d ; SPF  t a r g e t s i z e ; K i s the s k i p allowance  the amount of lumber t h a t w i l l  i s the sum  In a s i m i l a r way  of s h r i n k a g e , p l a n i n g and to the one  be allowed  to be under-  finished thickness.  d e s c r i b e d by Whitehead to  sawing v a r i a t i o n , Brown (13, 14) a l s o d e s c r i b e d a procedure the sawing v a r i a t i o n . which i s used  factor  A l l the formulas are s i m i l a r except  to c a l c u l a t e the between-board v a r i a t i o n :  determine to a n a l y z e the f o l l o w i n g  32  Sb = f d  2  [9  Where Sb i s the between board standard d e v i a t i o n , Rb i s the range between-board measurements and d2 i s the subgroup f a c t o r .  33  3.  3.1  MATERIALS AND  METHODS  Lumber Recovery 3.1.1  Sawmills  Selection  In the s t a t e of Durango the most frequent band headsaw widths 8 and 10 i n c h e s ( T a b l e 3 ) . per cent have an average 15,000 board  feet.  Of the 84 band headsaw m i l l s  6,  i n the s t a t e ,  60  lumber p r o d u c t i o n per 8 hour s h i f t  of 10,000 t o  From the 40 c i r c u l a r headsaws, 63 per cent have a  p r o d u c t i o n c a p a c i t y of 7000 t o 11,000 (16, 115). tend to d i s a p p e a r due tooth k e r f .  are  C i r c u l a r headsaw m i l l s  to the amount of wood converted  However, a t the present time c i r c u l a r  i n t o sawdust by  sawmills  the  still  r e p r e s e n t a v e r y s i g n i f i c a n t c o n t r i b u t i o n to the i n d u s t r y i n the s t a t e of  ) Durango ( T a b l e 3 ) . i n t h i s a n a l y s i s due  I t was  not p o s s i b l e to i n c l u d e any c i r c u l a r  to f i n a n c i a l l i m i t a t i o n s  to c o l l e c t  sawmill  the r e q u i r e d  data. By p r o d u c t i o n c a p a c i t y , at l e a s t 70 per cent of the sawmills c o u l d be c l a s s i f i e d as s m a l l s a w m i l l s , s i n c e they produce l e s s than 20,000 bd. ft.  of lumber i n 8 hour s h i f t s  (67).  Moreover, the percentage  of small  sawmills would i n c r e a s e perhaps t o 95 per cent a c c o r d i n g to K i r b a c h ' s classification  ( 7 1 ) , s i n c e v e r y few produce more than 50,000 bd. f t . per  shift. S i x sawmills were s e l e c t e d to i n c l u d e two width c l a s s i f i c a t i o n s of 6, 8, and 10 i n c h e s . i n t h e i r l a y - o u t and comparable. saw.  The  each o f the band headsaw A l l sawmills were  the c h a r a c t e r i s i t c s of the edgers  edgers  had  three c i r c u l a r  saws and  P r o d u c t i o n c a p a c i t y of the s i x m i l l s ranged  and  similar  trimmers were  the trimmer a  single  from 10,000 to 18,000  34  bd. f t . per s h i f t .  Thus, the s e l e c t e d m i l l s  c o u l d be regarded  as  r e p r e s e n t a t i v e of the i n d u s t r y i n Durango. P r o d u c t i o n e f f i c i e n c y may board  f e e t of lumber produced  be expressed as the r a t i o of thousands to number of men  s m a l l sawmill would have a r a t i o o f 1:1  per s h i f t .  (52, 67).  The  An  efficient  s i x sawmills  sampled have a r a t i o of 1:1.86 s i n c e they were producing an average 15,000 bd. f t . per s h i f t w i t h 28 workers. r a t i o i s the l a c k of automation 3.1.2 One  Log  of the reasons  of  f o r the  Sample S i z e  of the study o b j e c t i v e s was  determined  to analyze a r e p r e s e n t a t i v e sample of the s e l e c t e d  by the l o g volume v a r i a t i o n and  sawmills.  The  sample  the 95 per  cent  c o n f i d e n c e l i m i t s on the mean c u b i c volume, by use of e q u a t i o n No. 3.1.3  Log  low  i n most of the s a w m i l l s .  from the l o g p o p u l a t i o n i n each one s i z e was  One  of  3.  Scaling  A l t h o u g h board  f e e t measurement i s w i d e l y used  by the lumber  i n d u s t r y , e s p e c i a l l y the Doyle Rule, l o g s c a l i n g r u l e s are not recognized.  In t h i s  the Smalian  formula:  study the gross c u b i c l o g volume was  v =  officially  determined  0L+Jl).  L  Where V i s the volume i n c u b i c meters,  [io]  B and  b are b u t t and  areas i n square meters and L i s l o g l e n g t h i n meters.  Two  nearest centimeter.  Log l e n g t h was  top  diameters were  taken at each end-surface area with a l l measurements made i n s i d e bark, to the n e a r e s t c e n t i m e t e r .  by  the  a l s o r e c o r d e d to the  35  The ranging  sampled l o g s were grouped by diameter and l e n g t h  from 3.05 to 6.09 meters (10 t o 20 f e e t ) i n l e n g t h , w i t h 61 cm (2  f e e t ) d i f f e r e n c e between c o n s e c u t i v e from 20 t o 70 cm w i t h 3.1.4 Log Mexico.  categories  categories.  Diameter c l a s s e s ranged  5 cm i n t e r v a l s (Table 4 ) .  Log and Lumber Grading grading  p r a c t i c e s a r e not common i n the sawmill  industry i n  Very few e n t e r p r i s e s use l o g q u a l i t y e v a l u a t i o n to determine the  raw m a t e r i a l v a l u e  and the p o t e n t i a l lumber volume and q u a l i t y  recovery.  P r a c t i c a l l y no l o g t r a d i n g system e x i s t s i n the f o r e s t i n d u s t r y . When e n t e r p r i s e s do not have t h e i r own f o r e s t r e s o u r c e s , m a t e r i a l i s purchased as s t a n d i n g seldom taken i n t o account.  u s u a l l y the raw  t r e e s on a volume b a s i s and q u a l i t y i s  When t h i s i s not the case, l o g t r a d i n g takes  p l a c e u s u a l l y on volume b a s i s o n l y .  T h i s p r a c t i c e of t r a d i n g l o g s by  volume b a s i s i s changing to i n c l u d e l o g grades, as the s c a r c i t y of h i g h q u a l i t y l o g s and the p r i c e of raw m a t e r i a l become more For  this  study a s c a l e of 5 grades was used to c l a s s i f y  q u a l i t y according in  the n o r t h e r n  first  to the most common l o g - g r a d i n g  p a r t of the country.  grade and the poorest  The  ones as f i f t h  i r r e s p e c t i v e o f the end use, grade to the poorest For  i n sawmilling  and marketing takes  the grading  practices, place.  lumber encompasses 5 lumber c l a s s e s  ranging  from d e f e c t  f r e e or f i r s t q u a l i t y  lumber grade.  t h i s study, l o g s and lumber were graded by t r a i n e d  f a m i l i a r with Mexico.  or f i f t h  practices for conifers  grade (Table 5 ) .  common when c o m m e r c i a l i z a t i o n  most common system f o r g r a d i n g  the l o g  D e f e c t - f r e e l o g s were c l a s s i f i e d as  Standard lumber grades, a l t h o u g h r e c o g n i z e d are not v e r y  critical.  personnel  p r a c t i c e s f o r c o n i f e r s i n the n o r t h e r n  part of  36  3.1.5 As  Sawmilling  Procedure  the sample l o g s entered the m i l l s they were a s s i g n e d a sawing  order number. to i d e n t i f y  These numbers were c r o s s r e f e r e n c e d w i t h s c a l e l o g number  s c a l e and grade o f l o g .  Because o f the d i f f i c u l t y i n t r y i n g to keep t r a c k o f lumber from a g i v e n l o g , the sample l o g s were f e d i n t o the m i l l mixed w i t h m i l l - r u n l o g s , u s u a l l y on the b a s i s of one sample l o g to three m i l l - r u n  logs.  A l l m a t e r i a l c u t from a g i v e n l o g was p r o p e r l y i d e n t i f i e d with the m i l l - l o g number by a worker p o s i t i o n e d a t the headsaw as the l o g was i n i t i a l l y broken down. The  study l o g s were sawn f o r q u a l i t y r e c o v e r y a c c o r d i n g to normal  manufacturing  procedure  i n each  sawmill.  I n d i v i d u a l l o g i d e n t i t y was maintained through  the manufacturing  tallying.  Visual  t h i c k n e s s , grade 3.1.6  on each p i e c e of lumber  process to the f i n a l  p o i n t f o r g r a d i n g and  t a l l y data f o r each rough green board  i n c l u d e d width,  and l o g sawing number.  Lumber Y i e l d E v a l u a t i o n  To determine sawmill, f o l l o w i n g and e f f i c i e n c y ,  the lumber y i e l d  from  the common p r a c t i c e  the lumber-log  the processed l o g s a t each to analyze sawmill  r e l a t i o n s h i p was expressed  of l o g i n p u t r e c o v e r y as sawn lumber, measuring  productivity as a  percentage  both volumes i n m e t r i c  units.  Lumber Recovery J  Percentage °  =  Lumber Volume , — : — x 100 Log Volume  r  , [11]  37 Two types of lumber recovery r a t i o s were determined.  The nominal  lumber recovery percentage, which i s the r e l a t i o n s h i p of lumber volume i n nominal dimension divided by the actual log volume, and the actual lumber recovery, which was expressed as the percentage of actual lumber volume by the actual l o g volume. To determine the actual lumber volume, the average dimensions from each of the boards recovered from 10 logs of the most common diameter classes were used.  On each board the actual thickness was c a l c u l a t e d by  averaging s i x measurements, three at each edge equally spaced along the board.  The a c t u a l width was obtained by the average of four measure-  ments.  The two dimensions were taken to the nearest m i l l i m e t e r .  For the  actual length one measurement was taken to the nearest centimeter. The data c o l l e c t e d were used to compute the average actual dimension for each of the nominal dimensions produced by the s i x sawmills. 3.2 Log-Lumber and Byproduct Proportion At each of the s i x sawmills lumber, chippable residue and sawdust were determined from 10 logs of the most common diameter c l a s s e s .  Prior  to sawing, the logs were peeled by hand. The average diameters were measured small end and large end.  to the nearest centimeter at the  Length was also measured to the nearest  centimeter. A worker was placed at each machine centre to gather every piece of lumber from each of the logs.  The rough green lumber was marked with the  o r i g i n a t i n g l o g number to i d e n t i f y each component of log volume.  As soon  as the boards l e f t the trim saw they were measured as described i n  38  S e c t i o n 3.1.6  and weighed.  Lumber and c h i p p a b l e r e s i d u e s ( s l a b s ,  and end t r i m ) from each l o g were c o l l e c t e d s e p a r a t e l y and weighed p l a t f o r m - t y p e b a l a n c e to the n e a r e s t 0.010 s h i p was  kilogram.  assumed between lumber volume and lumber  A direct  edgings on a  relation-  weight, which was  used  to determine the volume of c h i p p a b l e products once t h e i r weights were known by d i r e c t measurement. s u b t r a c t i n g lumber  The amount of sawdust  was  determined  by  and s o l i d r e s i d u e volume from the gross c u b i c l o g  volume.  3.3  Quality 3.3.1  Control L o g - l e n g t h Allowance  To e v a l u a t e the volume l o s t due sampled  to over l e n g t h a l l o w a n c e , the  l o g s were grouped by a c t u a l l e n g t h i n c a t e g o r i e s o f 2 - i n c h  intervals.  The volume of the l o g s e c t i o n exceeding the c o r r e s p o n d i n g  nominal l e n g t h c a t e g o r y was  determined u s i n g the c o r r e s p o n d i n g diameter  class. Log volume l o s t  due  to o v e r l e n g t h allowance was  determined  f o r 4-  i n c h l e n g t h allowance a c c o r d i n g to the accepted l o g - b u c k i n g p r a c t i c e s i n the S t a t e of Durango (115). was  a l s o determined, assuming  The volume l o s t  f o r 6 - i n c h l e n g t h allowance  that the processed l o g s c o u l d be c o n s i d e r e d  as l o n g l o g s (4, 3 0 ) .  3.3.2  Lumber Dimension 3.3.2.1 Due  Allowance  Board T h i c k n e s s S e l e c t i o n  to the wide v a r i a t i o n of lumber  the market  dimension commonly produced f o r  and, s i n c e the t h i c k n e s s dimension has the g r e a t e s t e f f e c t  on  39 lumber volume determination (95), i t was necessary to select the most representative lumber thickness f o r sawing v a r i a t i o n a n a l y s i s . Data c o l l e c t e d on lumber thickness from each of the boards produced by sawing the logs sampled i n each sawmill were used to select the most representative thickness measurement i n nominal production.  I t was found  that 3/4 inch nominal thickness accounted f o r most of the lumber volume produced under normal manufacturing conditions and obviously i t should also account f o r the most of the volume l o s t due to sawing v a r i a t i o n (Figure 4 ) . 3.3.2.2  Sample Size and Board Measurements  According to the method described by Whitehead (109) and Brown (13, 14), a sample s i z e of 100 boards i n rough green dimension was taken at random by s e l e c t i n g subgroups of 5 boards each, keeping the feed d i r e c t i o n constant at the headrig.  On each of the sampled boards, 6  measurements of the thickness were taken to the nearest m i l l i m e t e r , 3 on each edge equally spaced along the board, avoiding the ends of the board as w e l l as r o t , knots or other defects.  The following c a l c u l a t i o n s were  then performed. For each board, the range of within-board measurements (Rw), (the largest board measurement minus the smallest from the s i x measurements), and the average board thickness ( X ) , (the s i x measurement averaged) were computed. The range between boards (Rb) was c a l c u l a t e d f o r each measurement point ( a , b, c, d, e and f ) among the f i v e boards i n the subgroup by subtracting the smallest thickness from the largest thickness of the corresponding measurement points.  40  The average range of within-board measurements (Rw) and the average thickness (X) f o r the subgroup were determined by the average of the corresponding 5 ranges and averages from the boards i n each subgroup. The average range between boards (Rb) was calculated by the average of the s i x measurement points of the f i v e boards i n each subgroup. Overall average range w i t h i n boards (Rw) f o r the 100 boards was c a l c u l a t e d from the average range w i t h i n boards (Rw) of each one of the 20 subgroups. O v e r a l l average range between boards (Rb) f o r the 100 boards was c a l c u l a t e d by averaging the 20 ranges between averages (Rb) of each subgroup. O v e r a l l average thickness (X) f o r the 100 boards was determined by averaging the 20 average thicknesses (X) of each subgroup. 3.3.2.3  Board Sawing V a r i a t i o n  Within-board sawing v a r i a t i o n was determined by Equation No. 5. Between-board sawing v a r i a t i o n was calculated by Equation No. 6.  From  the between-board v a r i a t i o n and within-board v a r i a t i o n the t o t a l sawing v a r i a t i o n was c a l c u l a t e d by use of Equation No. 7. 3.3.2.4  Target Size Determination  Target s i z e i s the smallest size the machine center can be set to cut without developing an excessive amount of undersized lumber.  The  target s i z e of rough green lumber was determined by Equation No. 8, which i s repeated here f o r convenience: T = (S .K) + SPF t  41  The v a l u e f o r K was determined allowable l i m i t ;  by assuming 5 per cent as the  t h a t i s , o n l y 5 per cent of the p r o d u c t i o n should have a  t h i c k n e s s dimension  below the t a r g e t s i z e ,  d e v i a t i o n s f o r a normal frequency  distribution.  For the v a l u e of F, the f i n i s h e d nominal  dimension  then K = 1.650 standard  t h i c k n e s s , i t was assumed that the  should be equal to the a c t u a l dimension.  i n c h boards the d r y f i n i s h e d  Thus, f o r 3/4  t h i c k n e s s would be 0.75 i n c h = 19.05  millimeters. S, s h r i n k a g e , was determined  assuming t h a t a nominal  4/4 i n c h green  board, when p l a n e d , measured 25/32 i n c h and when d r y planed measures 3/4 i n c h , by d i f f e r e n c e i t would have 25/32-3/4 o r 0.78125 - 0.75 = 0.03125 i n c h shrinkage  (44, 83).  P, f o r p l a n i n g l o s s , was c o n s i d e r e d to be 0.05 i n c h as the minimum volume o f wood l o s t d u r i n g p l a n i n g ( 1 1 ) . The  t a r g e t s i z e was f i n a l l y determined  by T = (1.65 S ) + 21.114  i n m i l l i m e t e r s , w i t h the c o r r e s p o n d i n g v a l u e s of S sawmills. sawmill  t  t  f o r each one of the  T h i s t a r g e t s i z e would be the t h i c k n e s s dimension  should be c u t t i n g  that the  the lumber to get o n l y 5 per cent of the  p r o d u c t i o n o f the 3/4 i n c h nominal 3/4 i n c h i n a c t u a l dimension  t h i c k n e s s w i t h v a l u e s lower  than the  when d r i e d and planed.  Comparing the t a r g e t s i z e w i t h the o v e r a l l mean t h i c k n e s s v a l u e of the 100 sampled boards (X - T ) represented e x c e s s i v e t h i c k n e s s . The  lumber volume l o s t by e x c e s s i v e t h i c k n e s s allowance  f o r each of  the sawmills, was c a l c u l a t e d by the f o l l o w i n g r e l a t i o n : X — T — - — x volume produced [12], X Where X i s the o v e r a l l average t h i c k n e s s and T i s the t a r g e t v a l u e . Volume l o s t =  42  4.  4.1  Raw  RESULTS AND  DISCUSSION  Material Characteristics  4.1.1  Raw  Material  From the a n a l y s i s of data c o l l e c t e d from the l o g s sampled at m i l l s yards,  i t was  determined t h a t the most frequent  ranged from 30 t o 35 cm to the s i x s a w m i l l s .  and  accounted  Nearly  diameter range from 25  f o r 33.8  per  diameter c l a s s  cent  of the l o g s input  80 per cent of the l o g s were w i t h i n  to 40 cm  (Table 5, F i g u r e 1 ) .  From t h i s  t i o n i t c o u l d be concluded  that sawlogs have a very uniform  distribution.  to the f a c t  T h i s i s due  already depleted official  and  l o g l e n g t h c l a s s was  almost 80 per cent of the processed w e l l - d e f i n e d length-bucking  diameter are  16 f e e t and  l o g s (Table 5,  by  processes.  accounted f o r  Figure 2).  This i s a  p r a c t i c e f o r sawlogs i n the S t a t e of Durango.  S i m i l a r c o n c l u s i o n s are r e p o r t e d frequent diameter range was  observa-  which once were not cut  r e g u l a t i o n s , are u s u a l l y a l l o c a t e d to some other  The most f r e q u e n t  the  that l a r g e r diameter l o g s  the s m a l l e r diameters,  the  by Z a v a l a  from 40  (115) who  to 45 c e n t i m e t e r s  found and  that the most the l e n g t h  was  16 f e e t . A l t h o u g h t h e r e i s not attempt to e v a l u a t e  a w e l l - d e f i n e d l o g grading  l o g q u a l i t y i t was  found that the 4 and  c o n s t i t u t e d 80 per cent of the l o g s processed, cent of l o g volume ( T a b l e 6, F i g u r e 3 ) . the No.  system, i n the  accounting  With the g r a d i n g  5 grades  f o r 78.5  system a p p l i e d ,  1 grade l o g s c o u l d have been a l l o c a t e d to a p e e l i n g process  veneer p r o d u c t i o n ,  but  i n general  per  t h i s does not happen because very  for few  43  e n t e r p r i s e s are h o r i z o n t a l l y i n t e g r a t e d , and  log grading  i s not a common  practice. 4.1.2 The  Log  Sample S i z e  number of l o g s sampled f o r each sawmill  volume-variation confidence  i n t e r v a l about the mean v a l u e  i n l e n g t h and use  a n a l y s i s of l o g p o p u l a t i o n  diameter of l o g p o p u l a t i o n  of a r e l a t i v e l y  (Table  small  was  being  determined from  the 95 per  f o r each m i l l .  the  cent  Small v a r i a t i o n  as shown i n T a b l e  sample s i z e to analyze  5 enables  sawmilling  the  study o b j e c t i v e was  f o r each diameter c l a s s , but  rather  not  to have f a i r l y  m a n u f a c t u r i n g c o n d i t i o n s , a t t e n t i o n was l o g s that f e l l w i t h one  or three l o g s w i t h  representative  these l o g s were not  The  p a i d to the  to 250  or even 300  logs.  confidence  When t h i s was  the  case  size  ranged from 131  l o g s s e l e c t e d at random from the  six  to  from the ones of t h i s study.  150,  sawmills.  objectives  s t u d i e s , the number of sampled l o g s was  the o b j e c t i v e s d i f f e r e d  purpose was  cent  s i m i l a r to those s t u d i e s w i t h i d e n t i c a l  In other  that,  to a v o i d p r o h i b i t i v e expenses.  making up a t o t a l of 879  83).  found  r a t h e r unusual diameters, e s p e c i a l l y l a r g e  number of l o g s s t u d i e d at each sawmill  sample s i z e was  values  s m a l l number of  i n c l u d e d i n the computation of sample  i n order  logs  under normal  Moreover, i t was  sample s i z e to o b t a i n the 95 per  i n t e r v a l would i n c r e a s e  determination  not  under the extreme c a t e g o r i e s .  ones, the r e q u i r e d  but  process  to cover a f i x e d number of  of the most common c h a r a c t e r i s i t c s of raw m a t e r i a l processed  (5, 65,  the  7).  Since  The  the  larger,  In some the  to have a r e p r e s e n t a t i v e number of l o g s by diameter c l a s s e s  or a r e p r e s e n t a t i v e  sample of a v a i l a b l e tree c h a r a c t e r i s t i c s to  44  cover the range of l o g s i z e s , even when they were not r e p r e s e n t a t i v e of a t y p i c a l l o g mix.  I n o t h e r cases the main o b j e c t i v e was  to generate  i n f o r m a t i o n to compare l o g g r a d i n g r u l e s or l o g s c a l i n g r u l e s 73, 75, 89,  4.2  93).  C h a r a c t e r i s t i c s of Lumber 4.2.1  (34, 42,  Recovery  Lumber T h i c k n e s s  From the sampled  l o g s processed i n each s a w m i l l , the boards were  r e c o r d e d a c c o r d i n g to t h e i r nominal t h i c k n e s s ; i t was  found t h a t 3/4  boards accounted f o r 52 per c e n t of the lumber volume produced. number, t h i s t h i c k n e s s dimension accounted p r o d u c t i o n ( T a b l e 8, F i g u r e 4 ) . lumber volume i n 1-1/2  Only one  By  f o r almost 80 per cent of sawmill was  i n c h t h i c k n e s s boards.  lumber dimension i s d i f f e r e n t  inch  producing a l a r g e  T h i s d i s t r i b u t i o n of  from the common lumber t h i c k n e s s e s produced  i n o t h e r s a w m i l l s t u d i e s (20, 66, 85, 86, 87), and r e f l e c t s market demand for  final  end uses of lumber.  In Mexico  the use of lumber f o r s t r u c t u r a l  framing i s minimal, w h i l e i n other c o u n t r i e s t h i s end use accounts f o r the  h i g h e s t lumber demand. 4.2.2  Lumber  Grades  The r e l a t i o n s h i p between l o g grades and lumber grades r e c o v e r e d has been e s t a b l i s h e d the  scope of t h i s  i n many ways (6, 23, 62, 70, 75, 89, 93, 113). study d i d not i n c l u d e any s t a t i s t i c a l  Although  or economic  a n a l y s i s to e v a l u a t e grade r e l a t i o n s h i p s , or to e v a l u a t e the g r a d i n g system a p p l i e d , the data i n T a b l e 9 suggest that the percentage of each lumber grade f o l l o w s a s i m i l a r log  grades.  t r e n d to the percentage d i s t r i b u t i o n o f  The No. 3, 4 and 5 lumber grades accounted  f o r 73 per cent  \  .  45  /  of the lumber volume produced, and the same l o g grades accounted per cent of the l o g volume processed  4.3  (Table 6 ) .  Log Volume and Lumber Volume R e l a t i o n s h i p 4.3.1  Lumber Recovery  Percentage  Lumber r e c o v e r y as a percentage  of l o g volume i n p u t was  f o r each sawmill f o l l o w i n g the normal procedure efficiency.  to e v a l u a t e  The o v e r a l l lumber r e c o v e r y expressed  volume, as a percentage r e c o v e r y percentage  determined sawmill  by nominal lumber  o f a c t u a l l o g volume, was 43 per c e n t .  was a l s o determined  by the a c t u a l l o g volume and expressed The  f o r 95.3  lumber r e c o v e r y by t h i s  procedure  dividing  Lumber  the a c t u a l lumber volume  by the p r o p o r t i o n as a  percentage.  i n c r e a s e d to 53 p e r c e n t , showing a  v e r y s i g n i f i c a n t d i f f e r e n c e between the two e x p r e s s i o n s of lumber r e c o v e r y ( T a b l e 12). These percentages  are f a i r l y  p r a c t i c e s i n the s t a t e o f Durango. extended to the sawmill  r e p r e s e n t a t i v e v a l u e s of the s a w m i l l i n g T h i s c o n c l u s i o n c o u l d even be  i n d u s t r y as a whole f o r the n o r t h e r n part of  Mexico, s i n c e s i m i l a r v a l u e s have been found  i n other s t u d i e s (96, 114,  115). The 23.7  d i f f e r e n c e between the two v a l u e s of lumber r e c o v e r y  represents  per cent o f the nominal lumber volume output by the s i x sawmills.  T h i s v o l u m e t r i c d i f f e r e n c e i s not taken i n t o account  when the f i r s t  phase  of c o m m e r c i a l i z a t i o n takes p l a c e between the sawmill and the warehouse. A c e r t a i n percentage  of t h i s volume r e p r e s e n t s e x t r a revenue to the  warehouse which u s u a l l y s e l l s dimensions.  the lumber to the r e t a i l e r by i t s a c t u a l  46  In g e n e r a l the lumber r e c o v e r y percentage r e p o r t e d i n t h i s  analysis,  compared to the lumber r e c o v e r y from other s t u d i e s , i s lower when the nominal v a l u e i s used.  However, when the a c t u a l lumber v a l u e i s used  r e s u l t s are s i m i l a r , r a n g i n g from 50 t o 60 per cent f o r most of the sawmills (20, 21, 29, 37, 65, 85, 104).  T h i s i s an i n d i c a t i o n of the  v a r i o u s ways to express lumber r e c o v e r y percentage, w h i l e i n other c o u n t r i e s the nominal lumber dimension dimension.  than f o r nominal dimension  Lumber Volume  and  (95).  Allowance  U s u a l l y , a c t u a l lumber dimensions dimensions  than the a c t u a l  In Mexico t h i s p r a c t i c e i s r e v e r s e d , w i t h l a r g e r v a l u e s f o r  a c t u a l lumber dimension 4.3.2  i s larger  are d i f f e r e n t  from  nominal  i n most o f the cases they a l s o d i f f e r  from  the s t a n d a r d  allowance dimensions  (17).  A c c o r d i n g to the standard allowance f o r 3/4  i n c h lumber t h i c k n e s s , the a c t u a l volume should be 30 per cent than the nominal volume, w h i l e f o r 1-1/2  i n c h , 1-3/4  i n c h , and 2 i n c h  lumber t h i c k n e s s the e x t r a volume should be 15 per c e n t , 11.5 and 8 per c e n t , r e s p e c t i v e l y .  larger  per cent  No allowance i s added i n the case of  t h i c k n e s s e s g r e a t e r than 2 i n c h e s . From the a n a l y s i s of the boards produced m i l l and measuring  t h e i r a c t u a l dimensions  by sawing  to compare them w i t h the  nominal dimensions, the t o t a l volume allowance was d i f f e r e n c e between the t o t a l allowance and from one was  sawmill to another  examined to determine  ( T a b l e 10).  the s i x m i l l s , due  The  ( T a b l e 11).  to over allowance  obtained.  The  the standard allowance o v e r a l l allowance  the lumber volume l o s t  t h i c k n e s s i n each sawmill s t u d i e d  10 l o g s i n each  f o r 3/4  f o r each  The  varies  variation  nominal  lumber volume l o s t a t  i n c h , 1-1/2  i n c h , 1-3/4  inch  47  and 2 - i n c h nominal t h i c k n e s s e s was cent and 7.36 3/4  0.96  per cent r e s p e c t i v e l y .  The  i n c h lumber volume over allowance  l a r g e number of 3/4 The  percentage  per cent, 4.47  i s made more s i g n i f i c a n t due  recorded  produced i n t h a t dimension.  An  n e g a t i v e v a l u e i n allowance,  was  of  to the  11).  of lumber volume l o s t v a r i e s among m i l l s .  T h i s sawmill a l s o accounted  per  r e l a t i v e l y s m a l l percentage  i n c h boards produced (Table  i n c h boards the g r e a t e s t l o s s was cent.  per c e n t , 5.33  at MIL  For  DIEZ w i t h 2.43  f o r the h i g h e s t percentage  3/4  per  of lumber  o p p o s i t e t r e n d , w i t h the lowest  and  even  the m i l l - LA VICTORIA - w i t h o n l y 21  per cent of the lumber produced i n 3/4 lowest v a l u e of the s i x s a w m i l l s .  i n c h t h i c k n e s s , which was  the  T h i s m i l l a l s o produced the h i g h e s t  percentage  of lumber volume of 1-1/2  i n c h t h i c k n e s s , 52 per  accounting  f o r the h i g h e s t volume l o s t by over allowance  cent  in this  dimension. The  percentage  of volume of lumber l o s t by over allowance  i n c h t h i c k n e s s i s n e g l i g i b l e f o r the o v e r a l l average.  On  f o r other t h i c k n e s s e s the l o s s c o u l d be v e r y s i g n i f i c a n t , to 7 per cent of the t o t a l lumber volume produced. volume l o s t due  to over allowance  v a r i e s among sawmills, i n c r e a s i n g to almost  4.3.3  the c o n t r a r y ranging from 4  overall  lumber 2.75  T h i s percentage  5 per cent f o r the m i l l  also with  of t h i c k e r lumber - LA VICTORIA.  Log-lumber and  Byproducts  Proportion  The average product volume d i s t r i b u t i o n f o r the s i x sawmills 57.97 per cent lumber, 26 per cent c h i p p a b l e r e s i d u e , and sawdust (Table 13).  3/4  i n volume by the s i x sawmills was  per cent of the nominal volume produced (Table 12).  the h i g h e s t percentage  The  in  16.03  per  was: cent  These r e s u l t s compare w e l l w i t h those d e s c r i b e d i n  48 other studies which report d i s t r i b u t i o n s of 50 to 60 per cent lumber, 18 to 31 per cent chippable residue and 9 to 19 per cent sawdust (19, 20, 21, 48, 69, 73, 85, 86, 87, 96, 100, 104). I t i s p o s s i b l e , by the procedure used i n t h i s study, that the volume of chippable residue and sawdust are biased, because the e f f e c t on weight by moisture  content  differences between the slabs and boards was not taken into account f o r chippable volume determination. The d i f f e r e n c e i n moisture content could introduce error i n weightvolume r e l a t i o n s h i p s when the outer and inner parts of logs are compared. However, the r e l a t i o n s h i p between volume and weight f o r lumber and slabs was found to be s i m i l a r .  This s i m i l a r i t y was confirmed by determining  the volume of slabs from 5 logs by water displacement  when the slabs were  dipped i n a f u l l water container. No doubt more r e l i a b l e data on the proportion of each log component would have been obtained by weighing the logs.  S t i l l a general conclu-  sion can be drawn that 25 to 30 per cent of s o l i d residue i s a large proportion of the log volume that, at present, very few m i l l s a l l o c a t e to secondary processing, such as pulping chips.  A large number of m i l l s  j u s t burn these byproducts without recovering any b e n e f i t .  I t i s urgent  to f i n d an economical s o l u t i o n to the u t i l i z a t i o n of these large volumes of byproducts that are u s u a l l y burned.  Chipped residues could be shipped  to pulp m i l l s to cope with the present d e f i c i t of pulp and paper products.  49  4.4  Quality Control 4.4.1  Log  Length  I t was  found that o n l y 4.55  per cent of the l o g s had  2 inch length  allowance over the nominal l o g l e n g t h c a t e g o r y  (Table 14).  lumber produced from these  not y i e l d  l o g s would probably  r e q u i r e d l e n g t h allowance.  Usually after  allowance i s 3 i n c h e s , a l t h o u g h The  i n some cases  s m a l l percentage o f roundwood w i t h  acceptable  only 2.25  per  percentage of l o g s w i t h On  A general  due  found t h a t f o r 4 i n c h s p e c i f i e d  volume input  considered, cent; but  lumber r e c o v e r y ,  which  c o n c l u s i o n i s that not  14 and  15).  the p r o p o r t i o n of l o g s w i t h  the  significant.  l o g - l e n g t h allowance,  category  practices. 90 per  s t u d i e d were misbucked. per cent of the  over l e n g t h decreased  cent The  When a 6 i n c h allowance  total  was  to 77.7  per  the l o g over l e n g t h volume d i d not change much, accounting  per cent of the s a w m i l l s '  input  (Table  due  to over l e n g t h s i n  study, w i t h v a l u e s r e p o r t e d by Dobie (30) and by Z a v a l a  i s a d i f f e r e n c e of almost 1.5  per cent; they  for  15).  Comparing the percentage of l o g volume l o s t this  the  s h o r t l o g s would amount  l o g s accounted f o r 4.75  (Tables  (95).  allowance.  to the poor bucking  through the sawmills  o v e r - l e n g t h volume of these  4.34  cent  s h o r t e r l e n g t h v a l u e s was  increased d r a s t i c a l l y ,  of the l o g s processed  sawmill  i t i s only 2 inches  from these  the  length  the other hand, the percentage of l o g s w i t h l e n g t h - c l a s s  over 4 i n c h e s I t was  limits.  lumber w i t h  shorter length i s within  c e n t , assuming a 45 per  again i s w i t h i n acceptable  sawn  trimming the board  l i m i t s , assuming a nominal 4 i n c h l o g - l e n g t h  Moreover, the lumber volume recovered to  end  The  found a 3.1  (115),  per cent  there  and  50  3.2  percent of l o g volume l o s t due  to over l e n g t h s , r e s p e c t i v e l y .  When  comparing i t w i t h the v a l u e r e p o r t e d by Aune and L e f e b v r e (4) the d i f f e r e n c e was 4.4.2 The  2.5  per c e n t .  Sawing V a r i a t i o n  average  sawmills ranged  t h i c k n e s s f o r 3/4  i n c h nominal  boards from  the s i x  from 21 t o 34 m i l l i m e t e r s ( T a b l e 16, F i g u r e 5 ) .  Similar  v a l u e s f o r t h i c k n e s s v a r i a t i o n have been r e p o r t e d i n other s t u d i e s which have concluded  that a great p o s s i b i l i t y  e x i s t s i n most sawmills (11, 56, T a b l e 17, i t can be concluded  102,  f o r r e d u c i n g sawing v a r i a t i o n  106,  t h a t o n l y one  107).  From the data shown i n  of the s i x sawmills  o p e r a t i n g w i t h a three standard d e v i a t i o n of 4.269 mm the v a l u e 3/32 statistical  i n c h (0.09375 i n ) d e f i n e d by V a l g  c o n t r o l or a c c e p t a b l e sawing  the t h i c k n e s s v a r i a t i o n .  (0.168 i n ) , c l o s e to  (106) as being under  variation.  In g e n e r a l sawing v a r i a t i o n between boards was of  was  the major component  T h i s type of c u t t i n g v a r i a t i o n i s a f f e c t e d  by setworks t h a t do not set w i t h c o n s i s t e n t accuracy.  Thus, the  setworks  should be the prime t a r g e t f o r improvement i n c o n t r o l of sawing (11, 4.4.3  P o t e n t i a l Lumber Recovery Increment by C u t t i n g to Target Thickness  The minimum f i n i s h e d t h i c k n e s s dimension requirements The  109).  f o r nominal  dry dressed of 3/4  amount of shrinkage f o r green  softwood  i n c h d r e s s e d lumber should be 0.794 mm  f o r lumber to meet the  i n c h i s 19.2 lumber d r i e d  + 0.7937 s h r i n k a g e + 1.27  mm  o r 0.75  to produce  o r 0.0313 i n (44).  amount removed f o r d r e s s i n g i s assumed to be 1.27 Thus, the minimun a c c e p t a b l e green  mm  in. 3/4  The minimum  or 0.05  i n (11).  t h i c k n e s s of sawn p i e c e s would be  d r e s s i n g = 21.264 mm  or 0.8313 i n .  19.2  51  In  order to compensate f o r v a r i a t i o n i n green  i n a c c u r a c y , the average by some s t a t i s t i c a l  green  t h i c k n e s s due  t h i c k n e s s must exceed  value related  the minimum t h i c k n e s s  to the degree of i n a c c u r a c y .  v a l u e s f o r each of the sawmills s t u d i e d are shown i n T a b l e A c c o r d i n g to Cardenas (17), f o r 3/4 the a c t u a l t h i c k n e s s dimension  ness v a l u e s , 22 mm  and 21.2637 mm,  which i s the allowance  lumber volume.  than t h i s v a l u e .  d i e z - w i t h o u t making any adjustment  or an allowance Comparing both  to reduce  of the r e s u l t s of t h i s  o p e r a t i n g c o n d i t i o n s , without  mm,  0.434 mm,  Only one  sawmill -  (Table 18).  mm  to a t a r g e t t h i c k n e s s of 23.461  c e n t , 4.87  any  setworks adjustment t h i c k n e s s by  and 0.953 mm  i n 3/4  mm  was  1.918  mm,  per c e n t , 0.23  2.148  present  mm,  0.06  increasing  skip  i n an i n c r e a s e o f per c e n t , 1.76  per  per cent r e s p e c t i v e l y of the t o t a l lumber  i n c h t h i c k n e s s by the c o r r e s p o n d i n g  o v e r a l l p o t e n t i a l increment  (106).  the s i x sawmills  r e s p e c t i v e l y without  per c e n t , 8.14  per cent and 3.8  volume produced  This value  an i n c r e a s e i n s k i p  T h i s r e d u c t i o n i n t h i c k n e s s would r e s u l t  lumber r e c o v e r y by 7.74  MIL  c o u l d reduce i t s  study i s t h a t , even w i t h the  t h e i r a c t u a l average 1.237  mm,  the a c t u a l t a r g e t t h i c k n e s s v a l u e s  of most of the sawmills s t u d i e d without  c o u l d reduce  thick-  There are i n d i c a t i o n s t h a t i t might be p o s s i b l e to  improve the sawing a c c u r a c y  One  in  Most of the m i l l s s t u d i e d  i n the setworks,  t h i c k n e s s from 25.429 mm  to 22 mm.  17.  lumber t h i c k n e s s ,  and produce l e s s than 5 per cent of the lumber with s k i p . the c l o s e s t  These  there i s a d i f f e r e n c e of 0.7363  for thickness v a r i a t i o n .  had a sawing v a r i a t i o n l a r g e r  a c t u a l average  i n c h nominal  should be e i t h e r 22 mm  volume of 30 per cent of the nominal  to sawing  on lumber r e c o v e r y i n 3/4  c a t e g o r i e s f o r the s i x sawmills would be 4.46  per  sawmills.  inch thickness  cent.  The  52 The  o v e r a l l d i f f e r e n c e between the a c t u a l mean t h i c k n e s s and the  target thickness  f o r the s i x sawmills, X - T, was 1.134 mm.  p o t e n t i a l lumber r e c o v e r y , by a p p l y i n g  The  t h i s f a c t o r to the d i f f e r e n t  lumber  t h i c k n e s s volumes produced, would be 6.4509 c u b i c meters, which would account f o r 3.5 4.4.4  per cent of the lumber volume processed  P o t e n t i a l Lumber Recovery Increment by Reducing Sawing Variation  An a d d i t i o n a l lumber volume c o u l d be recovered accuracy  to reduce the t a r g e t t h i c k n e s s without  by improving  of the sawmills  The  other  (106).  Only one  sampled, MIL DIEZ, was working c l o s e to that v a l u e w i t h 3  deviations =  23.461 mm.  sawing  an i n c r e a s e i n s k i p .  Sawing v a r i a t i o n c o u l d be reduced to 0.12 i n c h or 2.38 mm  standard  (Table 19).  0.1681 i n or 4.269 mm, w i t h a t a r g e t t h i c k n e s s of  T h i s means that even t h i s  sawmill  has room f o r improvement.  f i v e m i l l s w i t h l a r g e r sawing v a r i a t i o n s d e f i n i t e l y should be  a b l e to reduce l o s s e s to a t l e a s t  the same l e v e l as MIL DIEZ.  A d j u s t i n g the setworks i n the f i v e sawmills  and assuming t h a t  their  a c t u a l t a r g e t t h i c k n e s s c o u l d be reduced to the same v a l u e as the t a r g e t t h i c k n e s s of MIL DIEZ, the p o t e n t i a l t h i c k n e s s r e d u c t i o n would be: per c e n t , 8.96 per c e n t ,  2.81 per c e n t , 2.97 per cent,  each o f the r e s p e c t i v e m i l l s ( T a b l e 18).  3.22  2.53 per cent, f o r  The o v e r a l l p o t e n t i a l lumber  increment would be 3.49 per cent o f the lumber volume produced i n 3/4 i n c h thickness, after discounting target  the p o t e n t i a l volume gained  by sawing to the  thickness.  The  o v e r a l l average t h i c k n e s s r e d u c t i o n , by a d j u s t i n g the setworks on  the f i v e m i l l s and a f t e r d i s c o u n t i n g the p o t e n t i a l r e d u c t i o n by sawing to s m a l l e r green t a r g e t s i z e , would be  0.849 mm (Table 18). Assuming that  53 t h i s reduction i s also possible f o r the other board thicknesses produced, an a d d i t i o n a l 2.76 per cent of lumber volume would be recovered (Table 19). 4.5  Economic Analysis During 1980 approximately 1,152,574 cubic meters of logs were  converted to lumber i n the State of Durango (115).  Cubic meter losses of  roundwood assuming nominal 6-inch log length allowance, accounted f o r 4.34 per cent of the l o g volume throughout, which would c o n s t i t u t e 50,021,712 cubic meters of l o g s .  Conservatively assuming 45 per cent  lumber recovery, the p o t e n t i a l lumber volume y i e l d from improved bucking standards would be 22,509.77 cubic meters or nearly 9,544,142.7 board feet, with a conversion factor of 424 board feet per cubic meter. The 1,152,574 cubic meters of roundwood volume a l l o c a t e d to sawm i l l i n g , assuming 45 per cent lumber recovery, would y i e l d 518,658.3 cubic meters of lumber.  The p o t e n t i a l lumber recovery of sawing to  reduced target thickness would be 3.55 per cent of the lumber volume produced, which would c o n s t i t u t e 18,412.37 cubic meters or 7,806,844.7 board feet. I t i s l i k e l y that the p o t e n t i a l lumber volume gained would be recovered without any a d d i t i o n a l equipment adjustment or equipment investment, simply by closer c o n t r o l of the bucking and sawing tolerances. By adjusting the setworks, an a d d i t i o n a l lumber volume could be recovered, which would account f o r 2.7 6 per cent of the remaining lumber volume once the p o t e n t i a l lumber y i e l d increment by sawing to target  54  t h i c k n e s s was d i s c o u n t e d . constitute  T h i s p o t e n t i a l lumber recovery  13,806.788 c u b i c meters or n e a r l y 5,854,078 board f e e t .  The o v e r a l l p o t e n t i a l lumber volume recovery bucking  would  practices,  sawing to t a r g e t  by the c o n t r o l o f l o g  t h i c k n e s s and reducing  sawing  v a r i a t i o n would account f o r an a d d i t i o n a l 54,728,928 c u b i c meters or 23,205,065 board f e e t of lumber produced d u r i n g 1980 i n the S t a t e of Durango. The p r i c e o f lumber as m i l l - r u n  grade, d u r i n g  1980, was 8,272.15 Mexican pesos per M bd f t (115). r e c o v e r y would r e p r e s e n t  an a d d i t i o n a l  t o r e t a i l e r s by cheaper lumber  The p o t e n t i a l  lumber  revenue of 191,955,780 Mexican  pesos o r 8,345,903 US d o l l a r s to the s a w m i l l i n g savings  the l a s t months of  products.  i n d u s t r y or a p o t e n t i a l  55  5.  5.1  CONCLUSIONS AND RECOMMENDATIONS  Conclusions  5.1.1  I n the S t a t e of Durango l o g bucking distribution  practices yield a log  i n which nominal 16 f e e t l o g s c o n s t i t u t e 78 per  cent o f the l o g p o p u l a t i o n . 5.1.2  Log diameter  by c l a s s d i s t r i b u t i o n was c o n c e n t r a t e d  5-centimeter  range c a t e g o r i e s from 25 t o 40 cm, a c c o u n t i n g  f o r 80 per cent of the processed 5.1.3  Sample s i z e r e q u i r e d to analyze w i t h 95 per cent c o n f i d e n c e  i n three  logs. lumber r e c o v e r y  practices,  i n t e r v a l s on the mean volume, i s  c o n s i d e r e d to be r e l a t i v e l y s m a l l with an average of 150 l o g s per m i l l . 5.1.4  The most common lumber t h i c k n e s s y i e l d under normal manufacturing  p r a c t i c e s i s 3/4 i n c h boards which make up 80  per cent of the t o t a l number of p i e c e s produced and 52 p e r cent o f the t o t a l lumber volume 5.1.5  C a l c u l a t e d r e c o v e r y percentage, dimension,  i s approximately  a c t u a l dimension 5.1.6  recovered. when based on nominal  43 per cent; when based on  the v a l u e i s about 53 p e r c e n t .  26 per cent o f l o g volume i s converted  i n t o s l a b s and end  t r i m r e s i d u e s , from which a t the present v e r y few m i l l s d e r i v e any b e n e f i t .  56  5.1.7  Log over l e n g t h allowance r e p r e s e n t e d l o g volume throughput of the m i l l s .  4.34  T h i s amount could be  reduced by c l o s e c o n t r o l of the bucking r e s u l t i n g p o t e n t i a l f o r higher 5.1.8  per cent of t o t a l  p r a c t i c e s with  lumber volume  A d d i t i o n a l lumber volume can be recovered  recovery.  by d i m i n i s h i n g the  a c t u a l mean lumber t h i c k n e s s to the s t a t i s t i c a l l y target  t h i c k n e s s , which would r e s u l t  volume of 3.55 per cent of the t o t a l reducing  i n a p o t e n t i a l gain i n lumber produced.  By  the a c t u a l sawing v a r i a t i o n a p o t e n t i a l y i e l d  increment of 2.76 per cent of the t o t a l lumber produced c o u l d be 5.1.9  determined  Considerable  volume  achieved.  lumber volume c o u l d be recovered  l o g s to the a p p r o p r i a t e  l e n g t h , by r e d u c i n g  by bucking  the  the a c t u a l  average lumber t h i c k n e s s to the determined t a r g e t t h i c k n e s s , and by k e e p i n g sawing v a r i a t i o n The p o t e n t i a l lumber value Durango r e p r e s e n t e d  to an a p p r o p r i a t e  recovery  level.  i n 1980 i n the S t a t e of  54,728,928 c u b i c meters or 23,205,065 bd  f t which, t r a n s l a t e d to d o l l a r v a l u e s , would be a p o t e n t i a l revenue o f 8.3 m i l l i o n US d o l l a r s industry.  to the  sawmilling  57  5.2  Recommendations  5.2.1  S i n c e c u r r e n t l y 26 per cent of l o g volume i s converted s l a b s and  end  suggested  t h a t an economic a n a l y s i s be c a r r i e d  trims w i t h no f i n a n c i a l r e t u r n , i t i s  determine the f e a s i b i l i t y to 5.2.2  The  pulp  to  of a l l o c a t i n g c h i p p a b l e r e s i d u e s  mills.  by c o n t r o l l i n g exploited. two  the bucking  and  increment,  sawing o p e r a t i o n s , should  P a r t i c u l a r a t t e n t i o n should be d i r e c t e d  be  toward  f a c t o r s by the s a w m i l l i n g i n d u s t r y s i n c e no  a d d i t i o n a l investment 5.2.3  out  s t r o n g i n d i c a t i o n of p o t e n t i a l lumber r e c o v e r y  these  into  i s required.  F u r t h e r work should be conducted c a p a c i t i e s and  with d i f f e r e n t  sawmill  sawmill c h a r a c t e r i s t i c s to determine a more  p r e c i s e o v e r a l l p o t e n t i a l r e c o v e r y w i t h regard to sawing v a r i a t i o n and 5.2.4  bucking  practices.  L o g - l e n g t h v a r i a t i o n and  sawing v a r i a t i o n a n a l y s i s should  be  i n c l u d e d i n s a w m i l l i n g s t u d i e s as a common p r a c t i c e to e v a l u a t e sawmill 5.2.5  efficiency.  Emphasis should be g i v e n to the c o n t r o l of l o g l e n g t h and sawing v a r i a t i o n  i n t r a i n i n g programs r e l a t e d  processes, e s p e c i a l l y personnel.  to s a w m i l l i n g  the ones o f f e r e d to o p e r a t i n g  58  BIBLIOGRAPHY  1.  Adams, J . J . 1976. The sawing of West A f r i c a n hardwood l o g s . I n s t . Wood S c i . 7(4):2-4.  2.  A l l e n , F.E. 1973. H i g h - s t r a i n / t h i n k e r f . 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P r e d i c t e d c u b i c - f o o t y i e l d s of lumber, sawdust, and sawmill r e s i d u e from the saw-timber p o r t i o n s of hardwood t r e e s . USDA For. Serv. Res. Pap. NE-380, 23 pp. N o r t h e a s t e r n F o r . Exp. S t n . Upper Darby, Pa.  62.  Hanks, L e l a n d F. and Robert L. B r i s b i n . 1978. Lumber grade y i e l d s f o r graded aspen l o g s and t r e e s . USDA F o r . Serv. Res. Pap. NE-423, 12 pp. N o r t h e a s t e r n F o r . Exp. Stn., Broomall, P a .  63.  H a r p o l e , George B. and Hiram H a l l o c k . 1977. Investment o p p o r t u n i t y : best opening face sawing. USDA F o r . Serv. Res. Pap. FPL 291, 9 pp. F o r . Prod. Lab. Madison, Wise.  64.  Henley, John W. 1972. Grading sugar pine saw l o g s i n t r e e s . USDA F o r . Serv. Res. Pap. PNW-132, 8 pp. Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore.  65.  Henley, John W. and M a r l i n E . Plank. 1974. Lumber y i e l d from Engelmann spruce i n A r i z o n a . USDA For. Serv. Res. Pap. PNW-170, 11 pp. Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore.  63 66.  Huber Dean, George H. Sisterhenm, Robert L . Mardock, James L. R u s s e l l , Robert W. Mix and Frank John Banducci. 1976. B u i l d i n g a p r a c t i c a l q u a l i t y c o n t r o l program. Modern Sawmill Techniques. P r o c e e d i n g s of the S i x t h Sawmill C l i n i c , P o r t l a n d , Ore. Sawmill C l i n i c L i b r a r y , 6:186-228.  67.  James Shepard, M e r r i l l . 1974. The package m i l l f o r s m a l l o p e r a t i o n s . Modern Sawmill Techniques. P r o c e e d i n g s of the F o u r t h Sawmill C l i n i c New O r l e a n s , L a . Sawmill C l i n i c L i b r a r y 4:143-158.  68.  Kennedy, J o y c e . 1978. Log u t i l i z a t i o n can be improved. Lumberman 62(4):52-53.  69.  Kerbes, E.L. and J.A. M c i n t o s h . 1969. C o n v e r s i o n of t r e e s to f i n i s h e d lumber-the volume l o s s e s . F o r e s t . Chron. (10):348-352.  70.  B.C.  . 1968. Some r e l a t i o n s h i p s between e x t e r i o r l o g c h a r a c t e r i s t i c s and lumber r e c o v e r y v a l u e s f o r samples of B.C. I n t e r i o r spruce. West. F o r . Prod. Lab. I n f . Rep. VP-X-41, 19 pp. Vancouver, B.C.  71.  K i r b a c h , E. 1974. A survey o f sawing technology i n Western Canada, West F o r . Prod. Lab. I n f . Rep. VP-X-124, 21 pp. Vancouver, B.C.  72.  Lane, Paul H. 1963. E v a l u a t i n g l o g and t r e e q u a l i t y f o r wood products. F o r e s t Prod. J . 23(3):89-93.  73.  Lane, P.H., John W. Henley, R i c h a r d 0. Woodfin J r . , and M a r l i n E. Plank. 1973. Lumber r e c o v e r y from old-growth c o a s t Douglas-fir. USDA F o r . Serv. Res. Pap. PNW-154, 44 pp. Pac. Northwest F o r . and Range Exp. Stn., P o r t l a n d , Ore.  74.  Lane, P.H. and R i c h a r d 0. Woodfin J r . 1977. G u i d e l i n e s f o r l o g grading coast D o u g l a s - f i r . USDA For. Serv. Res. Pap. PNW-218, 14 pp. Pac. Northwest F o r . and Range Exp. Stn., P o r t l a n d , Ore.  75.  Lane, P.H., R i c h a r d 0. Woodfin J r . , John W. Henley and M a r l i n E. Plank. 1972. Lumber y i e l d from S i t k a spruce i n s o u t h e a s t e r n A l a s k a . USDA F o r . Serv. Res. Pap. PNW-134, 44 pp. Pac. Northwest F o r . and Range Exp. Stn., P o r t l a n d , Ore.  76.  L e f e b v r e , E. 1978. How improper l o g bucking reduces lumber revenues. Can. F o r . Ind. 98(9):21-25.  77.  Lewis, David W. and Hiram H a l l o c k . 1973. Using computers to i n c r e a s e lumber y i e l d . . . b e s t opening face program. 4 t h Wood Machining Seminar, Dec. 4-6, 1973. Richmond, C a l i f . 16 pp.  64  Malcolm, F r e d B. and Hiram H a l l o c k . 1972. E f f e c t s of three sawing methods on warp o f hard maple dimension c u t t i n g s . Forest Prod. J . 22(4):57-60. Mason, H.C. C a r l . 1976. Ind. 42(7):53-55. McBride, C F . 1963. 39(2):175-182.  A n a l y s i s of BOF sawing  Sawing s m a l l l o g s .  Forest  system.  Aust. For.  Chron.  McEwan, T.K. 1974. A n a l y s i s of the e f f e c t of the lumber r e c o v e r y f a c t o r (LRF) on sawmill c o s t s . F o r e s t Prod. J . 24(3):17-19. M u e l l e r , L i n c o l n A. and Roland L. Bager. 1963. Lumber grade r e c o v e r y from Engelmann spruce i n C o l o r a d o . USDA Res. Pap. RM-1, 23 pp. Rocky Mtn. F o r . and Range Exp. Stn., F o r t Collins, Col. N a t i o n a l Lumber Grades A u t h o r i t y . 1975. Standard g r a d i n g r u l e s f o r Canadian lumber. Vancouver, Canada. 233 pp. P e t r o , F . J . , S.M. Pnevmaticos and R.E. Booth. 1974. B o l t and lumber y i e l d s from white b i r c h . Can. F o r . Ind. 94(10):49-52.  grades  P h i l l i p s , Douglas R. 1975. Lumber and r e s i d u e y i e l d s from b l a c k oak saw l o g s i n western North C a r o l i n a . F o r e s t Prod. J . 25(l):25-33. . 1974. P r e d i c t e d green lumber and r e s i d u e y i e l d s from the merchantable stem of b l a c k oak t r e e s . USDA For. Serv. Res. Pap. SE-120, 10 p. Southeastern F o r . Exp. S t n . , A s h e v i l l e , N.C P h i l l i p s , Douglas R. and James G. Schroeder. 1975. P r e d i c t e d lumber and r e s i d u e y i e l d s from the merchantable stem o f s h o r t l e a f p i n e . USDA F o r . S e r . Res. Pap. SE-128, 12 pp. Southeastern F o r . Exp. S t n . , A s h e v i l l e , N.C.  green  Plank, M a r l i n E. 1979. Lumber r e c o v e r y from l i v e and dead l o d g e p o l e p i n e i n southwestern Wyoming. USDA Res. Note PNW-244, 15 i Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore. Plank, M a r l i n E. and John W. Henley. 1976. Lumber y i e l d s by the new timber c r u i s i n g l o g grades f o r old-growth coast D o u g l a s - f i r . USDA F o r . S e r . Res. Pap. PNW-203, 30 pp. Pac. Northwest F o r . and Range Exp. Stn., P o r t l a n d , Ore. Plank, M a r l i n E. and Thomas A. S n e l l g r o v e . 1973. Lumber y i e l d from western white pine i n n o r t h e r n Idaho. USDA F o r . Serv. Res. Pap. PNW-153, 30 pp. Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore.  65  91.  Pnevmaticos, S.M. 1975. Improving r e c o v e r y from softwood b u c k i n g i n e a s t e r n Canada. Can. F o r . Ind. 95(5):42-47.  92.  Pnevmaticos, S.M., l . B . F l a n n and F . J . P e t r o . c h a r a c t e r i s t i c s r e l a t e to sawing p r o f i t . 91(l):40-43.  93.  Pong, W.Y., and T.D. Fahey. 1973. Lumber r e c o v e r y from red and white f i r i n c e n t r a l C a l i f o r n i a . USDA For. Serv. Res. Pap. PNW-167, 39 pp. Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore.  94.  Prestemon, Dean R., F r e d E . D i c k i n s o n and W i l l i a m A. Dost. 1965. C h i n k a p i n l o g grades and lumber y i e l d . C a l i f . F o r . and F o r . Prod. 42:1-5.  95.  R o d r i q u e z , C a b a l l e r o , R o d o l f o . 1978. C o e f i c i e n t e s de r e f u e r z o y de a s e r r i o en l a p r a c t i c a mexicana de p r o d u c c i o n de maderas a s e r r a d a s de p i n o . Mexico y sus bosques 1 7 ( l ) : 8 - 2 3 .  96.  Schroeder, James G., M i c h a e l A. Taras and Alexander C l a r k I I I . 1975. Stem and primary product weights f o r l o n g l e a f pine sawtimber t r e e s . USDA For. Serv. Res. Pap. SE-139, 15 pp. S o u t h e a s t e r n F o r . Exp. Stn., A s h e v i l l e , N.C.  97.  S i n c l a i r , S.A., G. I f j u and H.J. Heikkenen. 1977. Logging and sawmilling. Bug boards. Lumber y i e l d , and grade r e c o v e r y from timber h a r v e s t e d from southern pine b e e t l e i n f e s t e d f o r e s t s . Southern Lumberman 234(2900):9-11.  98.  S n e l l g r o v e , Thomas A. 1977. White pine y i e l d s - d e c r e a s e as time s i n c e death i n c r e a s e s . F o r e s t I n d . 104(4):26-28.  99.  S n e l l g r o v e , Thomas A. and David R. D a r r . 1976. Lumber p o t e n t i a l f o r c u l l l o g s i n the P a c i f i c Northwest. F o r e s t P r o d . J . 26(7):51-54.  1971. How l o g Can. F o r . Ind.  100.  S n e l l g r o v e , Thomas A., John W. Henley and M a r l i n E. Plank. 1975. Lumber r e c o v e r y from l a r g e , h i g h l y d e f e c t i v e , low grade coast Douglas-fir. USDA F o r . Serv. Res. Pap. PNW-197, 23 pp. P a c . Northwest F o r . and Range Exp. S t . , P o r t l a n d , Ore.  101.  S t e e l e , P h i l i p H. and Hiram H a l l o c k . 1979. A mathematical model to c a l c u l a t e volumes o f lumber and r e s i d u e produced i n s a w m i l l i n g . USDA Res. Pap. FPL-336, 44 pp. F o r . Prod. Lab., Madison, Wise.  102.  S t e r n , A b i g a i l R., Hiram H a l l o c k and David W. Lewis. 1979. Improving sawing a c c u r a c y does h e l p . USDA F o r . Serv. Res. Pap. FPL-320, 13 pp. F o r . Prod. Lab., Madison, Wise.  66  103.  S u b s e c r e t a r i a F o r e s t a l y de l a Fauna. 1980. S i l v i c u l t u r a 78. SARH. Dpto. de D i v u l g a c i o n F o r e s t a l y de l a Fauna, Mexico. 145-147 pp.  104.  T a r a s , M i c h a e l , James G. Schroeder, and Douglas R. P h i l l i p s . 1974. P r e d i c t e d green lumber and r e s i d u e y i e l d s from the merchantable stem of l o b l o l l y p i n e . USDA F o r . Serv. Res. Pap. SE-121, 11 pp. Southeastern For. Exp. Stn., A s h e v i l l e , N.C.  105.  USDA.  106.  V a l g . L. 1965. A n a l y s i s of sawing accuracy control. B.C. Lumberman 56(6):68-72.  107.  1973. I n c r e a s i n g your lumber r e c o v e r y . program. Washington, D.C. 25 pp.  Sawmill  improvement  by s t a t i s t i c a l q u a l i t y  . 1978. P r e c i s i o n c u t t i n g i s not improving. 63(2):41-43.  B.C. Lumberman  108.  Warren, W.G. 1973. How to c a l c u l a t e t a r g e t t h i c k n e s s f o r green lumber. West. F o r . Prod. Lab. I n f . Rep. VP-X-112, 11 pp. Vancouver, B.C.  109.  Whitehead, J.C. 1978. Procedures f o r developing a lumber-size c o n t r o l system. West. F o r . Prod. Lab. I n f . Rep. VP-X-184, 15 pp. Vancouver, B.C.  110.  Woodfin, R i c h a r d 0. J r . 1978. Ponderosa pine lumber r e c o v e r y ... young growth i n n o r t h e r n C a l i f o r n i a . USDA For. Serv. Res. Pap. PNW-237, 13 pp. Pac. Northwest F o r . and Range Exp. S t n . , P o r t l a n d , Ore.  111.  . 1976. P o t e n t i a l s from salvage t i m b e r . USDA Rocky Mountain F o r e s t I n d u s t r i e s Conference i n M i s s o u l a , Mont. A p r i l 26-28, 1976.  112.  Woodfin, R i c h a r d 0. J r . and M a r l i n E. P l a n k . 1973. D o u g l a s - f i r c u l l l o g s and c u l l p e e l e r b l o c k s . USDA F o r . Serv. Res. Pap. PNW-164, 13 pp. Pac. Northwest F o r . and Range Exp. S t n . P o r t l a n d , Ore.  113.  Woodfin, R i c h a r d 0. J r . , M a r l i n E. Plank and Thomas A. S n e l l g r o v e . 1976. Western hemlock i n southeast Alaska ... u t i l i z a t i o n , lumber r e c o v e r y and c h i p y i e l d . USDA F o r . Serv. Res. Pap. PNW-208, 33 pp. Pac. Northwest For. and Range Exp. S t n . P o r t l a n d , Ore.  114.  Z a v a l a , D. 1980. R e n t a b i l i d a d de l a t r o c e r i a de pino de a s e r r i o . In press i n C i e n c i a F o r e s t a l .  115.  Z a v a l a , R. 1981. C a r a c t e r i z a c i o n de l a I n d u s t r i a de A s e r r i o en e l Estado de Durango. In press i n C i e n c i a F o r e s t a l .  en e l proceso  67  TABLE 1:  P r o p o r t i o n of lumber, c h i p p a b l e r e s i d u e and sawdust by l o g diameter range and sawmill type (18, 29, 35, 37, 39, 41)  P r o p o r t i o n i n Percentage Headrig type  Log top diameter (in)  Green lumber  Band, C o n v e n t i o n a l  5 - 15  56  31  13  Band, High  4 - 15  68  20  12  Circular  6 - 15  54  31  13  Log-Gang  6 - 14  55  32  13  Scrag  5 - 14 6 - 14  51 55  26 40  23 5  6 - 14  52  43  Strain  ) Chip-n-saw Chipper Headrig ) ) Beaver c a n t e r  .  Solid residue  Sawdust  4.5  TABLE 2:  Summary of r e f e r e n c e s i n log-lumber  and byproduct  relationship  P r o p o r t i o n i n Percentage  Reference  87  Log diameter (in)  Species  Short l e a f  pine  4-20.4  Head saw type  Band h e a d r i g  Saw kerf (in)  Lumber dimension (in)  3/16  1x5, 1x3  Chippable residue  Sawdust  Bark  54  2.6  10  10  4/4, 5/4  55  20  10  15 15  Lumber  85, 86  B l a c k oak  11.9-25.6  Band  19, 21  Yellow poplar  11.7-28.4  Band  3/16  4/4  54  18  13  5/16  4/4, 8/4  51  22  17  8/4, 4/4  50.3  28.5  13.6  7.6  54  21  16  9  62.5  24.5  8  60  31  9  61  20  19  20 104  S l a s h pine  9.6-21  Circular  Loblolly  9.8-19.4  Circular  pine  96  Pine  65  Engelmann spruce  93  White f i r  100  5/16  4/4, 8/4  6-34  Band  7/32  2x4, 2x6  7-50  Band  8/32  Douglas-fir  75  Sitka  48  Douglas-fir  spruce  69 50  Circular  Band 6-56  Band  4-44  Doublecut  4-14 Grand f i r  band 3/8  4-14  Band  53.6  35.1  13.3  4-14  Chipper  49.9  44.1  5.4  TABLE 3:  BAND  Type and number of sawmills i n the State  HEADSAWS  of Durango  CIRCULAR  Number of M i l l s  Band widths ( i n )  2  4  2  36  4  5  1  46  19  6  4  48  7  7  1  50  33  8  13  54  17  10  16  56  1  11  3  60  1  12  Source:  Caracterizacion  Number of M i l l s  HEADSAWS Headsaw diameter ( i n )  de l a I n d u s t r i a F o r e s t a l en e l Estado de Durango (115).  70  TABLE 4:  Log  grades  Log spading p r a c t i c e s i n the S t a t e of Durango v a r y l o c a l l y , making it  i m p o s s i b l e to p r e s e n t a s i n g l e l o g g r a d i n g r u l e .  As noted  T a b l e 6, 95% o f the l o g s were found to grade no b e t t e r  than  Grade 3 which i s d e f i n e d a p p r o x i m a t e l y as:  Diameter:  Minimum 12 unches  Length:  Minimum 12 f e e t  Knots:  L i v e p e r m i t t e d up to 1/6  Dead p e r m i t t e d up to 1/12  One  diameter  knot over maximum s i z e p e r m i t t e d .  of diameter  from  TABLE 5:  Sawlog d i s t r i b u t i o n by length and diameter  Number of logs by length c l a s s e s  1 8  MIL DIEZ  .  LOS BANCOS  '  1  2  '  1  4  '  1  6  '  U'  6  21  7  116  2  6  12  106  5  4  9  90  30  116 2  LA CIUDAD  %  0.9  >25<30  >30<35  >35<40  >40<45  >45<50  >50<55  >55<60  47  26  12  4  0  1  1  19  33  45  13  17  2  1  17  2  26  49  43  26  1  1  1  9  23  1  27  44 "  34  15  11  9  5  117  7  12  13  57  49  21  9  1  2  144  1  3  5  30  66  39  8  2  43  32  689  52  55  17  167  296  236  95  44  13  4.9  3.7  5.9  6.2  1.9  19.0  33.8  26.8  10.8  5.0  1.5  LA VICTORIA  8  >20<25  clas  52  12  No.  Number of logs by diameter  8  CHAVARR1A EL BRILLANTE  20'.  categories  OVERALL  78.4  >60<65  >65<70  8  1  2  0.!9  0.1  0.2  TABLE 6:  Number of l o g s and volumes by g r a d i n g c l a s s e s  Number of l o g s by grade s  Log volumes by grades (nr*)  Sawmills 1  2  3  4  5  1  19  130  17  38  76  32  64  32  17  CHAVARRIA  1  11  44  EL BRILLANTE  3  16  LA VICTORIA  1  5 0.6  5  0.5314  9.6521  53.2845  9.8234  13.7668  38.7550  19.6662  35.6697  17.1110  9.5863  92  1.4816  9.3160  28.4041  51.6792  33  98  1.7530  10.3694  16.5936  54.3393  25  37  87  0.5567  12.2137  18.3560  38.4227  37  134  203  500  23.4575  77.9226  113.8836  246.0371  4.2  15.2  13.1  56.9  LOS BANCOS 5  No.  2  4  MIL DIEZ  LA CIUDAD  1  2.7666  2.7666  3  OVERALL %  0.6  5.0  16.8  25.5  53.0  to  TABLE 7:  Number of l o g s sampled t o g i v e 95 per cent c o n f i d e n c e i n t e r v a l  about the p o p u l a t i o n mean  S a w m i l l s Parameter M i l Diez  P r e l i m i n a r y l o g sample Mean l o g volume  size  (m ) 3  Los Bancos  La Ciudad  Chavarria  80  80  80  80  .453284  .537002  .506059  E l Brillante  La V i c t o r i a  80  80  .516400  .569200  .547814  Standard  d e v i a t i o n (m )  .150552  .149350  .152422  .154327  .159536  .164348  Variance  (m )  .019775  .022305  .023232  .023817  .025452  .027010  3  Student t v a l u e Xr v a l u e Standard  e r r o r o f the mean 2 E  Required  value sample  size  2  2  2  2  2  2  4  4  4  4  4  4  .022664  .026850  .025303  .025820  .028460  .027318  .000514  .000721  .000640  .000667  .000810  .000750  153  123.76  145.15  142.89  125.68  143.99  150  131  150  148  150  150  Sample s i z e s t u d i e d  u>  TABLE 8:  Volume and percentage of pieces of lumber recovered  LUMBER 3/4 In thickness // Pieces  Volume m  MIL DIEZ  92.3% 2198  77.6% 21.4890  LOS BANCOS  78.9% 1528  46.6% 14.9673  LA CIUDAD  77.6% 1342  CHAVARRIA  RECOVERY  BY  1-1/2 i n thickness  1-3/4 i n thickness  // Pieces  // Pieces  1.0% 23  Volume m  Volume m  2.6% .7265  6.8% 161  19.8% 5.4204  13.3% 257  29.8% 9.5718  6.9% 135  16.1% 5.1814  58.1% 20.6184  20.3% 352  33.1% 11.7577  .2% 3  .4% .140  77.7% 1944  48.6% 19.4208  12.3% 307  26.0% 10.3784  8.8% 222  22.5% 8.9841  EL BRILIANTE  88.1% 1974  63.3% 21.8255  LA VICTORIA  59.6% 1045  21.7% 6.5064  79.0%  No.  THICKNESS  by thickness c l a s s e s  CATEGORIES  2 i n thickness // Pieces  Volume m  3 i n thickness // Pieces  -  .8% 16  1.1% .4545  5.4% 1.8661  6.8% 153  20.2% 7.0313  29.2% 498  51.8% 15.5343  9.2% 157  21.2% 6.3446  1.4% 34 .  52.6%  13.1%  24.8%  3.8%  2.7%  7.1%  .3%  1.1%  104.8279  1496  49.8348  521  13.8304  40  2.0278  9.8%  10002  19.7254  327  Volume tn"  -  .2% 6  1.1% .4191  2.5% 2.416  1.9% 34  8.4% 2.992  .2% 4  .7% .264  • 2.5% 55  OVERALL X  Volume ra // Pieces  .7% 17  2.6% 59  Others  10.8% 3.758  5.4% 1.6087  .9% 109  4.6% 9.43  4>  TABLE 9:  Lumber volume r e c o v e r y by grade c a t e g o r i e s (based  LUMBER Lumber volume recovery  Sawmills  (m ) 3  Grade 1  Grade 2  Volume (m )  Volume (m ) J  VOLUME  BY  Grade 3 Volume (m ) J  on l o g volume)  GRADES Grade 4  Grade 5  ^Volume  (m )  -Volume  %  MIL DIEZ  27.6359  2.5260  3.98  2.4120  3.80  10.1180  15.94  12.5799  19.82  LOS BANCOS  32.1368  3.6900  4.99  5.6501  7.81  13.0293  18.01  9.6436  13.33  LA CIUDAD  35.5078  4.1721  4.92  4.2823  5.05  16.1967  19.10  8.4291  9.94  CHAVARRIA  39.9219  6.9069  7.25  7.4976  7.90  14.8752  16.02  10.7693  11.50  EL BRILLANTE  34.4810  5.4069  6.51  3.3554  4.04  12.7739  15.38  12.9400  15.53  LA VICTORIA  29.9940  1.7451  2.51  3.2479  4.69  7.9425  11.42  16.9630  24.39  4.0746  5.02  4.4067  5.54  12.4892  15.97  11.8874  24.4475  12.24  26.4453  12.24  74.9356  37.53  71.3249  Mean OVERALL Total  199.6774  (m )  2.6711  3.15  15.76  0.4451  0.52  35.72  3.1162  1.60  TABLE  10:  Distribution  of of  Thickness Sawmills  Nominal  Actual  it  Widths  of  boards  (in)  (mm)  3/4  .0253  CJ  .0433  4  (.11f>2) ( . 1 6 4 5 ) KIL  DIE2  42  (.2124)  34  13  4  2  2  .C4(:5  7  6  1  .0243  70  17.  46  7  1 1/2 . 0 4 3 2  16  1  7  8  1/2 1 3/;. 1  r  yield  by nominal  width,  length  (in)  8  6  lumber  thickness,  and a c t u a l  Length  8  10  12  (.2745)  (.3295)  (2.46  )  10  dimension  and volume  (ft)  10  12  (3.129)  (3.749)  10  Volume  14  8  16  (4.379) 8  .  1 1  2  Percentages  (m^)  Actual  Nominal  Std.  Actual I ^ ^ ^ I ence e  T  (4.900) 1.4144  .954-,'  30%  32.43  3  .1526  .1205  15*  21.02  6.02  4  .2594  .2257  11.5*  13.92  2.42  45  2.43  2" (.1146)  3/4 LCS  DA'JCC 3  1  3/4 • 051c!  6  2  4  7  5  2  .05711  (.1116) CIUDAD  (3.079) 3  (3.684) 16  1 (.2713)  (.3214)  (2.466)  (3.092)  (3.674)  (4.301)  (4.910)  7  31  1.1340  .7646  30%  30.61  2  14  .6826  .5434  1556  20.«.0  5.40  1  5  .3059  .2370  1 1 . 5%  22.52  11.02  1  5  .3364  .2736  0.0%  T V . 15  11.15  (4.288)  .01%  (4.875)  54  3.0795  2.0991  30%  31.85  1.65  3  2  5  1  9  .5e98  .4763  15%  19.22  4.22  .os'.o  10  3  2  5  1  9  .7324  .6416  6%  12.39  4.39  .0254  55  1 1/2 . 0 4 3 4  10  3/4 .0475  12  1/2 . 0 4  3'.  142  19  33  55  9  19  5  3/4 .0511  1  22 2  n c  .052G  3  3/4  .0255  108  30  1 1/2 . 0 4 5 3  1  1  1  3/4 .C504  7  2  .054?  4  3/4  • 024C  1  1/2 . 0 4 3 7  3 P.  1  3 / 4 .1)464 »3 (-  .0603  (.2131)  Ti  2  10  4  6  5  2  1  •)  1  (.1615) 37  (.2151) 35  (.2716)  (.3132) 3  (2.476) 23  (.3237)  10 1  2  (2.474) 34  6  (3.096)  (3.D91) 0  (3.664)  (4.310)  (.1646)  4  2  3  1  (.2153)  t-C  20  5  1  n  11  3  4  (.2651)  1  (4.928)  9  12  .e738  .6090  30%  30.31  .31  1  1  8  .4014  .3259  15%  16.74  3.74  9  .4579  .3990  11.534  12.90  1.40  3  .1082  . 1760  ex  S.U9  -1.51  2  (3.735) 15  (4.373) 17  1 1  (.3163)  (2.509)  (3.103)  (3.716)  5  3  31  6  5  5  4  <i  1  1  1  1  3  1  a  *  5  (4.950) 1.8239  1.2522  3034  31.33  1.33  .0122  .0094  15%  22.64  7.64  5  .3723  .3028  11.5%  16.79  7.29  3  .2430  ,207b  b%  14.57  6.57  34  1  4  3  (.2625)  22  1  (.1126) 50  (.1649)  £_  (. 1CES)  V I C T O R If.  13  10  1  .0265  (.1142)  LA  (2.464)  30  3/4  CHILLAr.TE  (.2775)  (.3229)  31  c  EL  (.1677)  (.2774)  29  1  CHAVA3RIA  (.2193)  2  3/4 LA  (.1676)  1  (4.346)  (4.33C) 16  .64'. 9  .6033  30/,  26.99  -1.01  3  22  1.4700  1.1'323  15%  19. v5  4.95  1  4  .26i35  .2371  11.5*  11.73  .23  6  .6747  .5315  21.21  13.21  :  C'/a  ON  TABLE 11:  Allowance and over-allowance i n volume f o r d i f f e r e n t  3/4 i n c h Thickness  1-1/2 i n c h T h i c k n e s s  Sawmills Volume  Volume  allowance  (m )  30% 6.4467  32.48% 6.9796  2.48% .5329  14.9673  30% 4.4901  30.81% 4.6114  .81% .1212  9.5718  20.6184  30% 6.1855  31.85% 6.5669  1.85% .3814  19.4208  30% 5.8262  30.31% 5.8864  21.8255  30% 6.5476  6.5064  30% 1.9519  LA CIUDAD  CHAVARRIA  EL BRILLANTE  LA VICTORIA  NOTE:  Over  21.4890 LOS BANCOS  % Vol  Actual  allowance  MIL DIEZ  OVERALL  Standard  (m ) 3  allowance  3  Standard allowance  15% .1089  Actual allowance  Over allowance  21.02% .1527  6.02% .0437  15% 1.435  20.40% 1.9526  5.40% .5168  11.7577  15% 1.7636  19.22% 2.2598  4.22% .4962  .31% .0602  10.3784  15% 1.5567  18.74% 1.9449  3.74% .3881  31.33% 6.8379  1.33% .2902  1.8661  15% .2799  22.64% .4224  7.64% .1425  28.99% 1.8862  -1.01% -.0657  15.5343  15% 2.3301  19.95% 3.099  4.95% .7689  .7265  0.96 104.8274  board t h i c k n e s s  1.3202  5.33 49.8348  2.3562  I n t h i s sample, 1-3/4 and 2 i n c h t h i c k n e s s e s were not produced at e v e r y m i l l . Where no v a l u e s appear f o r volume i n 1-3/4 and 2 i n c h t h i c k n e s s e s , comparative percentage f i g u r e s have been o b t a i n e d from 10 l o g sample data of Table 10.  TABLE  11:  Allowance  and over--allowance i n volume f o r d i f f e r e n t board t h i c k n e s s ( c o n t i n u e d )  1-3/4  i n c h Thickness  2 inch Thickness  Sawmills Volume  Standard  (m )  allowance  5.4204  5.1814  3  MIL DIEZ  LOS BANCOS  Actual  Over  Volume  allowance  allowance  (m )  11.5% .6303  13.92% .7629  2.42% .1326  11.5% . 5958  22.52% 1.1668  11.02% .5709  3  LA CIUDAD CHAVARRIA 8.9841 EL  BRILLANTE  LA VICTORIA  11.5% 1.0331  12.90% 1.1589  1.40% .1257  11.5%  18.79%  7.29%  11.5%  %  11.73%  NOTE:  allowance  8%  19.15%  11.15%  8%  12.39%  4.39%  6.49% .0222  1.51% .0068  7.0313  8% .5625  14.57% 1.0244  6.57% .4619  6.3446  8% .5075  21.21% 1.3456  13.21% .8381  .23%  .8292  allowance  Over  8% .0363  4.47 19.5859  allowance  Actual  .4545  7.36  OVERALL Vol  Standard  13.8304  1.3068  In t h i s sample, 1-3/4 and 2 i n c h t h i c k n e s s e s were not produced at every m i l l . Where no v a l u e s appear f o r volume i n 1-3/4 and 2 i n c h t h i c k n e s s e s , comparative percentage f i g u r e s have been o b t a i n e d from 10 l o g sample data of Table 10.  TABLE 12:  Nominal, a c t u a l , and allowance volumes r e l a t e d a c t u a l and nominal dimension  (1)  (2)  Nominal volume  to lumber r e c o v e r y based on  D i f f e r e n c e between (2) and (1)  D i f f e r e n c e between (2) and (3)  Lumber r e c o v e r y percentage  Actual volume  (3) Nominal volume p l u s allowance volume  Volume  Percentage  Volume  Percentage  Nominal  (m )  (m )  (m )  (m )  MIL DIEZ  27.6359  35.5918  34.8821  7.9559  28.78  0.7097  2.56  43.56  56.10  LOS BANCOS  32.1368  39.8676  38.6585  7.7308  24.05  1.2091  3.76  43.74  55.10  LA CIUDAD  35.5078  44.3624  43.4730  8.8546  24.94  0.8894  2.5  41.87  52.23  CHAVARRIA  39.9219  48.3946  48.3741  8.4727  21.22  0.0205  0.05  44.18  53.25  EL BRILLANTE  34.4810  43.0624  41.8710  8.5814  24.83  1.1914  3.45  41.54  51.85  LA VICTORIA  29.9940  35.7238  34.2760  5.7294  19.10  1.4474  4.83  43.12  51.36  199.6774  297.0022  241.5397  47.3248  23.7  5.4675  2.75  43.00  53.32  Sawmills  3  OVERALL  3  3  Actual  3  .  TABLE 13:  Log-lumber and byproducts  *WEIGHT' (kg) Sawmills  Volume of logs  proportions  VOLUMES (m ) 3  PERCENTAGE DISTRIBUTIONS BY VOLUME  (m )  Large dimension lumber  MIL DIEZ  3.1205  1815.0  7327.0  1.8283  0.1446  0.7434  63.22  23.82  12.96  LOS BANCOS  3.8205  2136.2  1099.3  2.1186  0.1211  1.0847  58.62  28.39  12.99  LA CIUDAD  7.2111  4034.9  1565.3  4.1263  0.3674  1.1605  62.31  22.33  15.36  CHAVARRIA  4.0601  1513.0  906.3  1.8835  0.1757  1.1087  50.72  27.30  21.98  EL BRILLANTE  4.5054  2279.9  1287.2  2.4304  0.0653  1.3756  55.39  30.53  14.08  LA VICTORIA  6.3605  3430.8  1508.3  3.4281  0.2321  1.5051  57.54  23.66  18.80  29.0781  15209.8  7099.1  16.8152  1.1062  6.9780  57.97  26.00  16.03  3  OVERALL  Chippable residues  Large dimension lumber  Short dimension lumber  Chippable residues  All lumber  Chippable residues  Sawdust  * The weight of short boards, i . e . those l e s s than 8 f t i s not i n c l u d e d s i n c e o n l y f u l l l e n g t h lumber used to c a l c u l a t e the weight-volume r e l a t i o n s h i p used to determine volume of c h i p p a b l e r e s i d u e s .  co o  TABLE 14:  O v e r - l e n g t h allowance volume by l o g length c a t e g o r i e s .  •3 T o t a l number of logs and volume (m3)  Sawmill  Number of logs and over length volume (m ) by over l o g l e n g t h c a t e g o r i e s 2-in  4-in  6-in  8-in  10-in  12-in  14-in  16-in  MIL DIEZ  150 63.4G01  3 • .0102  10 .0930 .  27 .4353  39 .6696  32 .6160 •  14 .3324  11 .31614  14 .4734  LOS  131 72.3452  16 .0625  17 .2128  26 .4337  20 .4475  14 .4080  7 .2560  4 . 1341  27 1.0272  LA CIUDAD  150 84.7996  4 .0189-  4 .0374  24 .3705  37 .6025  29 .7673  27 • 1.0034  7 .3010  18 .5734  CHAVARRIA  14& 90.6609  4 .0322  11 .1169  28 .5091  30 .7472  46 1.16B5  15 .5693  5 .2960  5 .2664  EL ERILLAPJTE  150 63.0553  12 .0713  2 .0262  1 .0166  4 .0900  5 .1790  17 -.5496  34 1.2565  75 2.9630  LA VICTORIA  150 69.5491  1 .0020  6 .0355  16 .2940  33 .6650  27 .7572  25 .7463  37 1.2624  eANCCS  No.  %  879 100  40 4.55  5.0  • .2171 .05  1.9863 .10  44  112 12.74  146 16.61  164 18.65  107 12.17  90 10.23  176 20.02  OVERALL Vol.  %  464.0984 100  1.8513 .39  2.9309 .63  4.0038 .86  3.4949 .75  3.1023 .67  6.6208 1.43  TABLE 15:  Log volume l o s t by over l e n g t h with 4 and 6 i n c h e s nominal  4 inches nominal Sawmills  4 inches over l e n g t h  Number of l o g s and volume  Logs m  allowance  6 inches nominal  4-16 inches over l e n g t h  Volume 5  6 inches over l e n g t h  Volume Logs  m  allowance  allowance 6-16 i n c h e s over l e n g t h  Volume  Volume  Logs m  Logs m  m  MIL DIEZ  150 63.4682  13  0.1031  .16  137  2.8481  4.48  40  0.5385  .84  110  2.4128  3.80  LOS BANCOS  131 72.3452  33  0.2953  .40  98  2.7686  3.83  59  0.73 90  1.02  72  2.3249  3.21  LA CIUDAD  150 84.7998  8  0.0563  .06  142  3.7085  4.37  32  0.4272  .50  118  3.3376  3.93  CHAVARRIA  148 90.8809  15  0.1491  .16  133  3.5765  3.93  43  0.6582  .72  105  3.0674  3.37  EL BRILLANTE  150 83.0553  14  0.0975  .12  136  5.0799  6.11  15  0.1143  .14  135  5.0631  6.09  LA VICTORIA  150 69.5491  1  0.0020  .01  149  4.0324  5.79  7  0.0875  .13  143  3.9469  5.67  84  0.7034  .15  795  2.5647  0.55  683  20.1527  4.34  OVERALL  879  22.014  4.75  196  oo  TABLE 16:  Thickness v a r i a t i o n d i s t r i b u t i o n f o r nominal 3/4 i n c h boards  Number of Boards Average T h i c k n e s s i n M i l l i m e t e r s  Sawmills 21  23  24  25  26  27  28  MIL DIEZ  3  18  31  29  18  1  LOS BANCOS  2  6  22  29  19  7  3  16  21  14  LA CIUDAD  22  29  30  31  32  11  4  4  2  1  13  14  4  3  3  1  1  2  1  CHAVARRIA  2  7  13  24  24  22  7  1  EL BRILLANTE  1  3  7  16  17  31  21  4  3  8  24  29  23  10  2  20  36  140  144  148  88  33  8  7  7  3.3  6.0  17.3  24.0  24.7  14.7  5.5  1.3  1.2  1.2  LA VICTORIA  Boards  3  33  34  1  OVERALL Per  cent  co OJ  TABLE 17:  Mean t h i c k n e s s - sawing v a r i a t i o n and t a r g e t t h i c k n e s s  Parameters  M I L L I M E T E R S _____  — M i l Diez  f o r nominal 3/4 i n c h boards  Los Bancos  La Ciudad  Chavarria  E l Brillante  La V i c t o r i a  Average range w i t h i n boards  1.796  1.953  2.64  1.964  2.284  2.193  Average range between boards  2.878  4.109  6.199  3.450  3.873  3.763  25.429  26.390  25.830  24.574  25.417  25.023  0.708  0.771  1.042  6.775  0.901  0.865  1.234  1.733  2.624  1.662  1.624  1.570  1.423  1.896  2.823  1.834  1.857  1.792  23.461  24.242  25.770  24.140  24.180  24.070  1.967  2.148  0.060  0.434  1.237  0.953  20.702  17.361  19.072  19.846  19.647  32.078  34.299  30.072  30.988  30.399  O v e r a l l average Within  thickness  boards standard  deviation  Between boards standard T o t a l sawing standard  deviation  deviation  Green t a r g e t s i z e P o t e n t i a l thickness  reduction  x-3(St) Spread of sawing v a r i a t i o n 5+3(St)  21.160 29.698  oo  -P-  TABLE 18:  Sawmills  Lumber volume 3/4 i n c h  P o t e n t i a l lumber volume recovery i n 3/4 i n c h nominal lumber by c u t t i n g to t a r g e t t h i c k n e s s and by reducing sawing v a r i a t i o n  Actual average thickness  Target thickness  P o t e n t i a l lumber r e c o v e r y by t a r g e t t h i c k n e s s  P o t e n t i a l lumber r e c o v e r y by sawing v a r i a t i o n  (mm)  (mm)  Thickness reduction  Volume  (m )  %  Volume m  Thickness reduction  MIL DIEZ  21.4890  24.429  23.461  1.968  7.74  1.6632  0  0  LOS BANCOS  14.9674  26.390  24.242  2.148  8.14  1.2183  0.781  3.22  0.4472  IA CIUDAD  16.2890  25.830  25.770  0.060  0.23  0.0375  2.309  8.96  1.4561  CHAVARRIA  19.4208  24.574  24.140  0.434  1.76  0.3418  0.679  2.81  0.5361  EL BRILLANTE  21.8256  25.417  24.184  1.237  4.87  1.0629  0.719  2.97  0.5998  6.5065  25.023  24.070  0.953  3.80  0.2472  0.609  2.53  0.1583  100.4983  25.444  24.310  1.134  4.46  4.4822  0.849  3.49  3.3509  LA VICTORIA  OVERALL  3  Volume  %  Volume m 3  0  86  TABLE 19:  Nominal thickness  P o t e n t i a l lumber r e c o v e r y i n d i f f e r e n t nominal t h i c k n e s s by c u t t i n g to t a r g e t t h i c k n e s s and by r e d u c i n g sawing v a r i a t i o n  Actual average thickness  Lumber volume produced  P o t e n t i a l lumber r e c o v e r y by t a r g e t thickness  P o t e n t i a l lumber r e c o v e r y by sawing variation  Volume  Volume  (in)  (mm)  (m )  3/4  25.4  100.4983  4.46  4.4822  3.49  3.3509  1-1/2  43.7  47.5433  2.59  1.2314  1.99  0.9216  1-3/4  48.9  19.6798  2.32  0.4566  1.78  0.3422  2  55.8  13.8305  2.03  0.2807  1.55  0.2100  181.5519  3.55  6.4509  2.76  4.8247  OVERALL  3  %  (m ) 3  %  (m )  FIGURE 1.  D i s t r i b u t i o n o f l o g s by diameter  classes  70-.  36  4 0  4ft  SO  l 70  85  DIAMETER CLASSES IN CENTIMETERS M i l Diez Los Bancos  + - +— H  La Ciudad  Chavarria + + + + + + t  E l Brillante La  Victoria  oo  FIGURE 2.  D i s t r i b u t i o n o f l o g s by l e n g t h  MIL DIEZ  LA  classes  CUIDAD  EL  140-1  I 4 0 i  140-1  120-  120  120-  100-  100-j  100-  8 0 -  80  60-  60  60-|  4 0 -  40  40  2 0 -  20  to  o o  0  JL 10  IX  JL  14  l«  It  20  H  80  H  0  BRILLANTE  20-|  10  IX  14  It  It  20  0  10  JL__ 12  14  16  18  20  O  LOS BANC0S  CHAVARRIA  LA  140-1  I40-.  140-1  120-j  120-  120-  100  100-  100-  80  to-  60-  60-  60-  60  4 0 -  40-  40-  20  20-  20-  J. 10  IX  14  I t  JBL It  20  10  LOG  IX  14  It  JL It  LENGTH " CLASSES  X0  10  VICTORIA  12  14  16  IS  20  oo oo  FIGURE 3.  D i s t r i b u t i o n o f l o g s by  grades and  volumes  FIGURE 4.  100-I  P r o p o r t i o n o f d i f f e r e n t lumber t h i c k n e s s e s produced under normal manufacturing c o n d i t i o n s  x  FIGURE 5.  Thickness v a r i a t i o n i n 3/4 i n c h nominal lumber  

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