CHAPTER 30 - LOG DEFECTS AND DEDUCTIONS
Contents
31 General --------------------------------------- 47
32 Defect types and applicable deduction methods - 48
33 Defect types and deduction procedures --------- 50
Barber chair ---------------------------------- 50
Bark seam ------------------------------------- 50
Breaks and splits ----------------------------- 50
Burls ----------------------------------------- 54
Catface --------------------------------------- 54
Check, heart ---------------------------------- 55
Check, weather
-------------------------------- 55
Crack,
frost ---------------------------------- 58
Crook
----------------------------------------- 58
Crotch ---------------------------------------- 60
Fire scar ------------------------------------- 61
Knots, large ---------------------------------- 62
Knot clusters and burls ----------------------- 63
Knots, rotten --------------------------------- 65
Lightning scar -------------------------------- 66
Multiple defects ------------------------------ 68
Pitch, massed --------------------------------- 69
Pitch seam, heart check, frost cracks --------- 69
Pitch spangle --------------------------------- 74
Pull, stump or sliver ------------------------- 76
Rings, pitch and shake ------------------------ 76
Rot, conk
------------------------------------- 81
Rot, heart ------------------------------------ 82
Rot, sap -------------------------------------- 84
Rot, stump ------------------------------------ 86
Stain ----------------------------------------- 88
Sweep ----------------------------------------- 88
Wormholes ------------------------------------- 89
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CHAPTER 30 LOG DEFECTS
AND DEDUCTIONS
31 General
A scaling defect is defined as any unsound material or abnormal shape in a log that reduces its net volume. Defects are grouped in two common classes:
1. Natural Defects. Natural defects are those which exist in the log before the tree is felled. These may include all kinds of interior rot, rotten knots fire scars, catfaces, massed pitch, pitch rings and shake, pitch seams and checks, lightning scars, sweep, crook, massed grubworm holes, crotch, sap rot, weather checks (snags and windfalls), knot clusters, burls, and some types of large knots.
2. Logging Defects. Logging defects are those generally occurring after the tree is felled. They include mechanical defects, such as breakage, brooming, tractor damage, and loading damage. They also include other defects caused by poor logging practices, such as sap rot, weather checks, and damage caused by borers after trees have been cut.
Forest Service scaling considers deductions for all defects, natural and mechanical. All logs shall be scaled as presented, unless otherwise instructed by the Contracting Officer. The Contracting Officer must make the decision concerning permissive deductions for defects caused by the purchaser allowing logs to remain in the woods.
*-Some defects in logs are caused by abnormal delay in scaling due to the fault of the purchaser. Deductions made for sap rot, weather checks, or other defect resulting from abnormal delay in scaling are chargeable at contract rates. Therefore, these deductions must be separately identified.-*
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32 Defect Types and Applicable Deduction Methods
Following is a tabulation of common types of defect and the defect-deduction method most applicable to each type. The types of defect and applicable procedures are discussed in code 33. Deduction methods are described in chapter 20.
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33 Defect Types and Deduction Procedures
Descriptions of common defect types, with applicable deduction procedures, follow in alphabetical order. The Scribner Decimal C rule is used in examples. The same general scaling practices apply to the International rule.
Barber Chair. See Breaks and Splits.
Bark Seam. See Pitch Seam.
Breaks and Splits. Breaks and splits are mechanical defects which require special consideration. Modern-day logging, much of it in steep country, will generally result in some damage to the logs when felled, bucked, transported, and handled by various mechanical devices. In many instances this damage may result in a considerable loss of sound timber. Refer to codes 17.5 and 42 if abnormal amounts occur. Broken-end logs (shatter breaks) caused by falling, split or slabbed ends caused by poor bucking or falling, and slivers (stump pull) pulled from logs in falling are the most common types.
Breakage may occur regardless of what precautions are taken; or may result from improper bedding, felling trees across stumps, logs, rocks, or ridges. Accurate determination of the extent of lengthwise shattering is often difficult as it may be hidden by bark. Remove enough bark to insure inclusion of all of the defect in the deduction.
Buckers should usually leave some breakage in a log to avoid waste.
Lengths of broken-end logs are determined as follows:
1. Where the broken end is wholly or partly bucked, measure the log from saw cut to saw cut and make any required deduction (fig. 15).
2. When only one end is bucked, determine the most applicable scaling length and make the required deduction (fig. 16).
3. When neither end is bucked, determine the applicable scaling length and make any required deduction for defect (fig. 17).
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*-4. When applicable scaling length is determined and the length due to breakage is less than the minimum length stated in the contract, the log is considered unmerchantable due to size. It shall be considered as substandard. Refer to section 55.63 for recording.-*
.
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The following deduction procedure should be used to simplify and standardize treatment of broken-end logs:
1. Logs under 16 inches. If a quarter to a half of the end section within the scaling cylinder is gone, deduct half the length affected (fig. 18). If more than half the end section is gone, consider the entire end lost and deduct for the full length affected (fig. 19).
2. Logs 16 inches and over. When any portion of the end section is broken, use a combination of pie-cut and length deduction. See figures 20 and 21.
Falling and bucking breaks are generally avoidable, but may be caused by rot, by heavy leaning trees
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on steep slopes, or by some factor not readily apparent to the scaler. Deductions for these defects are generally made by the squared-defect method (fig. 22). Refer to code 41.2 for scaling of chunks and slabs.
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Burls. See Knot Clusters and Burls.
Catface. Scars or wounds, often caused by falling objects scraping against a tree, are generally called catfaces. When shallow in depth and removable with the slab, they need no deduction. When they penetrate deeper into the log, use the pie-cut method.
For catfaces similar to sap rot, determine how much of the surface of the scaling cylinder is affected and apply a diameter cut.
Figure 23 illustrates a 16-foot log with a deep and partially grown-over catface. The defect is 10 feet long and is confined to a quarter section of the log. The diameter at the small end of the log is 17 inches. The gross scale of a 10-foot log, 17 inches in diameter, is 120 or 12 Decimal. The deduction for defect would be 1/4 of 12 or 3.
.
Figure 24 illustrates a 16-foot log with a catface extending the entire length. The catface is 2 inches deep and covers 1/3 the circumference. The small diameter of the log is 15 inches and the gross scale 140 or 14. The defect is determined by subtracting the scale of an 11-inch log (diameter of core) from the gross scale and dividing by 3. (14-7) ÷ 3 = 2.
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Watch for massed pitch, wormholes, and rot in conjunction with catface. If ants are present, they are usually an indication of a deep dry rot somewhere within the log.
Check, Heart. See Pitch Seam, Heart Check, Frost Crack.
Check, Weather. Also known as wind and sun checks. They occur (1) in logs left in the woods or cold decks for an extended period before scaling and (2) in dead trees (snags). Make no deductions for logs that weather check when left in the woods (by the option of the purchaser) or in cold decks. However, make deductions for such logs if the purchaser was not responsible for the condition of the logs as in sales of right-of-way logs already piled, or logs resold to a new purchaser. Instructions to scalers should cover proper procedures when this condition occurs.
Figure 25 illustrates a 32-foot log cut from a live tree. End dimensions are 24 and 28 inches, respectively. Weather checks occurred after the tree was felled and bucked in a right-of-way clearing. Such checks usually are about twice the depth at the ends of a log than elsewhere. If these weather checks are deductible (that is, not due to delay in removal by the purchaser), deduct as follows:
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1. For top segment.
a. Measure the small end diameter of the 32-foot log (24 inches in the illustration).
b. Measure one-half of the depth of the checks on the small end (3 inches) and multiply by 2 for both sides of the segment (6 inches); this is the gross diameter deduction.
c. Reduce the diameter of the segment (24 inches) by 6 inches to obtain a net diameter of 18 inches. The net scale then is that of a 16-foot log 18 inches in diameter, 210 board feet or 21.
2. For butt segment. In the top segment the gross diameter deduction was 6 inches or a net scale of a log 6 inches less than the diameter at the small end. Do the same thing with the butt segment, but use the midpoint diameter of the long log.
a. Find the midpoint diameter by use of the taper in the long log. In the illustration the taper is 4 inches from butt to top. Thus the midpoint diameter is 26 inches.
b. Reduce the segment diameter by 6 inches for a net diameter of 20 inches. The net scale then is that of a 16-foot log 20 inches in diameter, 280 board feet or 28.
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Where only a fraction of the log surface or end is affected and the checks are deep, use the pie cut method, as shown in figure 14. Where (1) only a fraction of the log surface or end is affected and (2) the checks are confined to the outer surface and are deductible use a percentage or fraction of a diameter deducted for the length affected (fig. 24).
Weather checks found in logs cut from dead trees often are different from those described previously. These checks usually occur before a tree is felled. The depth of the checks in the sides of logs and at midpoint are about as deep as those in the ends. However, because of moisture retained in butts of standing trees, checks in the large end of a butt log may not be as deep as those in the top.
*-Weather checks often penetrate deep into the center of dead logs. If spiral grained, the log may be cull for sawtimber. However, if the log is straight grained, or the spiral is not severe, consider the possibility of cutting merchantable length lumber between the checks. By mill visits, determine the seriousness of weather checks. The statements above are guides to help in making deductions. To be merchantable, the log must meet net percent of gross stated in the contract. Figures 25a and 25b illustrate the recovery of merchantable length lumber from spiral-checked logs.-*
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*-
Crack, Frost. (See Pitch Seam, Heart Check, Frost Cracks.)
Crook. A crook in a log is a sudden curve or bend from a straight line. One type is found in logs from upper portions of trees. Snow or falling trees that break off tops of other trees can cause this defect. Before a new leader starts, rot and black massed pitch may enter the wound. The new leader may die, leaving a large sucker-type dead knot (fig. 26). Breakage may occur at this point due to weakness caused by cross grain. Normal deduction for the log illustrated should be a 2-foot-length cut, since 6-foot lumber can be recovered from the small end of the log. Had the section been less than 6 feet in length, a deduction for this complete portion of log would be necessary.
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Another type of crook occurs in the large end of butt logs. It may locally be called "churn" or "pistol butt." This is caused by young trees having been pushed over by snow or forced to grow outward from steep slopes. Later these trees assume a natural position and grow upward but retain a crook or "hook" in the butt. Loss caused by this defect often is confined to a 2- or 4-foot section.
Figure 27 illustrates a 16-foot log with crook in the butt end. To deduct for this defect. measure the length of the crook and determine what fraction of this length is affected. In the illustration, 1/2 the log will produce 14-foot lumber and 1/2 the log will produce 12-foot lumber. No 16-foot lumber can be obtained. The net scale is determined by deducting 3 feet from the 16-foot log.
In deductions for crook, consider the loss in squaring up the ends of uneven-length lumber. Also consider unmerchantable cross-grained lumber that may result from this defect.
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Crotch. A crotch is the point in a tree where it forks into two or more leaders or stems. Proper bucking can eliminate much of the defect. Usually the loss occurs from a bark seam, split, or cross grain in the end of such logs. Loss may occur from flat sides often characteristics of a crotch condition (fig. 28. A deduction of 1 or 2 feet in length is often made for this type of defect, but the actual deduction
depends on observation of loss during mill visits. It may be sufficient merely to square out the bark seam. Amount of deduction depends on the point of bucking. See figure 29 and code 17.32 for method of measuring diameters of crotched logs.
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Fire Scar. Fire scars are usually found only in butt logs, but occasionally extend into the second 16-foot log. In some species this defect may be accompanied by massed black or red pitch; sometimes by weather checks and wormholes or rot. Part of the scar at the top end may be healed over; consider possible defect here in measuring its length within the scaling cylinder. Mill visits will show how fire scars affect recovery of lumber from local species, timber of different ages, and scars of different ages. Fire scars may also be called catfaces. (See catface.)
Figure 30 illustrates a 16-foot log with fire scar extending 8 feet from the butt. Fire scars of this type always have a part of the defect outside the scaling cylinder (not deductible) and therefore appear more serious than they are actually.
Use a combination of pie cut and length of defect. First, estimate what part of the end of the scaling cylinder is affected, then what length is lost by defect. In the illustration half of the cross section of the scaling cylinder might be affected for 8 feet in length. Deduct 1/2 of the 8 feet or 4 feet in length. Net scale is that of a log 12 feet long.
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Knots, Large.
1. Knots are normally a lumber-grade (quality) defect and will not be considered in scaling. However, on occasion, knots are so large and/or numerous that they will cause weaknesses in the lumber and an actual volume loss. Deductions for knots will only be allowed when this actual volume loss will occur. "Roughness" caused by knots does not automatically create a need for defect deductions.
2. Volume loss is more often the result of conditions created by dead knots than live knots of the same size. Live knots taper internally immediately, whereas dead knots do not taper until they reach the last growth ring before the limb died. Volume loss generally occurs in the outer portion or "collar" of a log (fig. 31).
3. Following are some conditions under which volume loss due to knots may occur:
a. Large knots in whorls.
b. Unusually large knots.
c. Grain distortion caused by adventitious bud swellings around larger knots.
d. Several large knots on the same face.
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4. Actual loss from knots should be ascertained by mill visits. Loss from whorls of large knots as in item 3a above will usually be included in a 1-footlength deduction for each major complete whorl. Loss from unusually large knots can normally be determined by a combination pie cut and length cut, whereas loss from conditions mentioned in item 3c and 3d above will generally occur in the outer portion of the log which might include part, all, or more than the sap ring.
5. Table VIII, Knot Guide to Merchantability and Deductions in the appendix may be used if found to be locally applicable.
Knot Clusters and Burls.
1. Knot clusters grow in two distinct types. One type consists of a group of small limbs developed from adventitious buds. It does not affect the volume of lumber produced and is not treated as a defect. The other type consists of a group of larger limbs, often with a large dead limb in the center that penetrates deeply into the log. It may cause breakage in lumber produced. This second type commonly occurs in Douglas-fir and larch. Often massed pitch and twisted or disrupted grain occur in connection with such knots. When these will cause a loss in the volume of lumber produced, a deduction should be made. The extent of loss from this cause can be best determined by mill visits.
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2. When knot clusters cover about one-fourth of the circumference of a log, make a length deduction to cover the volume loss in the affected portion (one-fourth the length of the cluster within the scaling cylinder). Usually 1 foot per major cluster is sufficient. If the clusters are so close together as to prevent the manufacture of merchantable-length lumber between them, apply the pie-cut method for the portion of the length affected.
Figure 32 illustrates a log where knot clusters are so close to the log end as to prevent the recovery of merchantable-length lumber. When this occurs, increase the deduction accordingly.
3. Burls are dome-shaped growths of various sizes sometimes found on tree trunks. At times they penetrate into logs as far as their height above the log surface. Treat burls the same as item 2 above.
4. Massed pitch, twisted grain, and sometimes a large limb may cause breakage in lumber similar to that caused by knot clusters. If observations during a mill visit so indicate, make the deduction as for knot clusters (fig. 32). Note, however, that defects which prevent recovery of standard-length lumber should be extended.
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5. Numerous small burls or pitch scabs occasionally are found on Douglas-fir and other logs. Massed pitch and pitch rings sometimes occurring beneath these burls may cause a loss in the outer portions of logs. A diameter deduction for this defect equal to the depth and portion affected as for sap rot may be equitable but should be checked, and not applied automatically (fig. 34). The figure shows areas of defect only. Deductions should include all loss of standard-length lumber.
Knots, Rotten. In some species and areas, rotten knots indicate interior rot. Rot may follow the knot into the log, then spread out one or both ways. The length of this spread varies with species, age, and
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locality. When rot shows on one or both ends, make deductions using the pie cut method for the length affected (fig. 35). Logs with rotten knots and no end indications are a challenge to any scaler. Visit local mills to establish a pattern for making deductions for this defect.
Lightning Scar. The spiral effect of lightning scars, sometimes with shatter, massed pitch, wormholes, and weather checks, presents a difficult scaling problem. The degree of spiral and volume loss varies. Give consideration to short-length lumber the log will produce.
The following alternate method may be used for the more difficult problems:
1. Determine degree of spiral over the entire log (as 1/4, 1/3, 1/2, 2/3). Consider recovery of short-length lumber and taper.
2. Obtain gross scale of the log.
3. Measure depth of scar. Include massed pitch and other defects if present.
4. Double the scar depth (for both sides, sec. A) and subtract from log diameter (fig. 36). This result is diameter of section B.
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5. Obtain volume of section B and subtract from gross volume of the log for the gross deduction if the entire collar, section A, were lost.
6. Judge how much of this collar is lost. If the spiral went 1/3 the way around the log, only 1/3 would be affected in some way. Short-length-lumber recovery might also reduce the amount lost.
7. Subtract net deduction from gross scale for net scale. Figure 36 illustrates a 16-foot by 26-inch log with lightning scar spiral of 1/3 and 6 inches in depth. When the above formula is applied to these figures, the results are:
a. Gross log scale of 16-foot by 26-inch log = 50
b. Depth of scar doubled = 6 plus 6 inches = 12
c. Diameter of unaffected section B = 26 minus 12 inches or 14
d. Volume of section B = (16 feet by 14 inches) = 11
e. Gross deduction = 50 minus 11 = 39
f. Scar affects 1/3 of this "collar" 1/3 of 39 = 13
g. If short-length-lumber recovery and taper allowance in that 1/3 is about 25 percent, reduce the amount of loss 25 percent or about 3.
13 minus 3 = 10
h. Net log scale = 50 minus 10 (Decimal) = 40
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Some logs have shallow scars on all sides that are deep enough to cause some loss in the scaling cylinder. Treat this defect the same as sap rot by making a diameter deduction.
Use the pie cut method (fig. 14) when lightning scars are deep and affect one face.
Multiple Defects. More than two types of defect may occur in ends and sides of logs. To apply one or more deduction methods to each defect is often difficult and time consuming, and may result in erroneous deductions. The best method is usually to combine a pie cut with the length of defect method on such logs. In some cases, the squared-defect method may be applicable.
Figure 37 illustrates a 16-foot, 24-inch butt log with multiple defects in the large end. First estimate what fraction of the scaling cylinder is affected. About two-thirds is affected to some extent. Next. estimate the average length of the defects.
Example: Fire scar 10 feet, rot 6 feet, heart check 8 feet, making an average of 8 feet. The deduction then is 2/3 of 8 feet, or a 6-foot-length deduction.
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Pitch, Massed. Often massed pitch occurs in connection with fire scars and may extend beyond the scar at the top end. It is considered in the deduction *-for this defect. Occasionally logs show such-* a heavy accumulation of pitch in the large ends that it makes the wood unmerchantable. Make a deduction for this only when mill visits show that it causes an actual volume loss. Make a length cut if most of the log end is affected. Use the pie-cut method or the squared-defect method if only a portion is affected.
Pitch Seam, Heart Check, Frost Cracks.
1. A heart check is an opening or separation across the log heart at right angles to the annual rings. When filled with pitch, it is called a pitch seam. Frost cracks are similar to heart checks, except that they are usually visible in the bark and extend from the outside of the log to the heart. Often these defects run farther lengthwise than do pitch rings. Normally make deductions for seams, checks, and frost cracks by the squared-defect method.
A word of caution in measuring the width of this type of defect; Search for "breakouts" or branches from the main check or seam. These are sometimes difficult to see, especially when log ends are wet. *-The minimum width of a check is 1 inch. This results in a width of 2 inches for squared defect calculations when the inch is added for waste.-*
Figure 38 illustrates a 16-foot butt log with a heart check in the large end.
Top diameter of the log is 21 inches. The actual height of
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the check is 23 inches, but do not add an inch for waste to this dimension. Use 21 inches (the diameter of the scaling cylinder) for the height and 3 inches for the width. The width measurement includes the 1 inch allowed for waste. The estimated depth of penetration in the log is 8 feet. The squared-defect method (code 22.4) then gives 3 by 21 = 63 or a deduction of 7 for a 16-foot length. One-half of this gives 4 (Decimal), the deduction for 8 feet of penetration.
2. When the check shows on both ends and apparently extends straight through the log without twisting, deduct as for heart rot: For 16- to 20-foot logs, average the end defect dimensions. For logs shorter than 16 feet, use the large end dimensions unless the Regional Forester prescribes otherwise. For logs longer than 20 feet, follow the deduction rules described under code 22.5. This includes the use of the alternative method explained under code 22.5, item 3c.
Figure 39 illustrates a 32-foot butt log with heart check showing on both ends
and in the same position. Small diameter of the 32-foot log is 23 inches, and
midpoint diameter 25 inches. End dimensions of the defect in the 32-foot log
are 2 by 15 inches and 3 by 25 inches, respectively, including waste. When
dimensions of 15 and 25 inches are averaged the midpoint dimension is 20
inches.
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Use 3 inches for the estimated width at the midpoint. For the butt segment, average 3 by 20 inches and 3 by 25 inches; result, 3 by 23 inches. For the top segment, average 2 by 15 inches and 3 by 20 inches; result, 3 by 18 inches. The squared-defect method (code 22.5) then gives the following deductions: Butt segment, 3 x 23 = 69 or 70 or 7. Top segment, 3 x 18 = 54 or 60 board feet (6 Decimal).
3. Deductions for two cross-checks are made as explained in item 2 preceding.
In measuring height *-of the second check, do not include the width of the
first check measured (fig. 40). Diagram at right angles (figs. 40 and 40a). The
"give and take" procedure explained in item 4 may also be used in
determining the deduction for two cross-checks (fig. 40b). Use the "give
and take" procedure when diagramming at right angles creates a loss of
recoverable material in the squared defect area of the checks.
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Figure 42 illustrates a 16-foot log with a 2- by 20-inch heart check showing on the butt end. The same check at the top end is 1 by 16 inches, but shows a 90° twist. After adding 1 inch for waste and averaging the defects (3 by 21 and 2 by 17), the squared-defect method (code 22.5) gives 3 x 19=57, or a deduction of 6 for a 16-foot log with a straight check. Adjusting for the 90° twist, the actual deduction for the log will be 6 x 2 or 12.
*-Figure 43 illustrates a 32-foot log with a heart-* check showing on both ends. End measurements of the defect are 3 by 21 inches and 2 by 12 inches, including waste. The check on the top end indicates a 90° twist from that showing on the butt end. By using the squared-defect method (code 22.5), the defect is computed as follows:
Average end defects (3 by 21 and 2 by 12 inches) to obtain dimensions of defect in the center of the log (3 by 17 inches).
Determine defect for each scaling length by averaging end defects and adjusting for twist (45 degrees in each segment).
3 by 21 and 3 by 17 average 3 by 19 inches.
3 x 19=57 or a deduction of 6 for the 16-foot length for the butt segment if the check was straight.
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Adjusting for the twist, the actual deduction for the butt segment will be 6 x 1.5, or 9.
3 by 17 and 2 by 12 average 3 by 15 inches.
3 x 15=45 or a deduction of 5 for the 16-foot length of the top segment if the check was straight. Adjusting for the twist, the deduction for the top segment will be 5 x 1.5 or
8. The total defect deduction for the 32-foot log is 17.
6. When logs are exposed to the sun and wind for an extended period, weather or seasoning checks often occur in the ends. The scaler must learn to detect this type because he makes no deduction for them (see Checks, Weather). Such checks often increase in length due to weather. Use a thin wire or knife blade on doubtful checks to determine the type. Look for sawdust in checks. Sometimes this is an indication of a natural heart check.
7. For multiple frost cracks, see Pitch Spangle.
Pitch Spangle. When more than two pitch seams occur in the large ends of butt logs, the defect is called a pitch spangle. Douglas-fir and western larch are species commonly affected. Breakouts from the seams often occur. Sometimes pitch rings occur in connection with pitch seams. Defect of this type causes heavy loss in lumber manufacture. Sometimes a part of the defect extends into the second log.
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Make length-cut deductions for pitch spangles in the butt 16-foot log when the size of the spangle approaches the scaling diameter. For other logs, use the squared-defect method, as you would for multiple checks. See figures 41 and 44.
Figure 44 illustrates a 32-foot, 20-inch log with pitch spangle. The entire scaling cylinder is affected because the seams extend beyond its edges. Some defect shows on the small end of the 32-foot log indicating the defect is greater at the 16-foot point but not so great as in the butt end. In the illustration the butt 16-foot segment is highly defective, more than 50 percent. If the contract merchantability clause specifies 50 percent, this log is cull. If 33 1/3 percent, this log may be marginally merchantable.
If mill visits indicate that pitch spangle cuts out this way, treat the top 16-foot log as follows: Judge the large end defect as 50 percent of the scaling cylinder and the length of penetration as 8 feet. Deduct half of the 8 feet affected or 4 feet for the large end. For the small end, apply the squared-defect method and use 8 feet for the length. Compute the deduction for each, add, and then compute the net scale of the log.
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Refer to examples included under Pitch Seam, Heart Check, Frost Cracks for alternate procedures for determining the volume of a top log.
Pull, Stump or Sliver. (See Breaks and Splits.)
Rings, Pitch and Shake.
1. Ring shake defect is the separation of one or more annual rings sufficient to cause a volume loss in manufacture. This separation is known as a pitch ring when it becomes filled with pitch, often a characteristics of species like Douglas-fir and larch.
2. Shake ring defects follow the annual rings. Sometimes they stop where knots start, for knots tend to hold the annual rings together. On some logs the length of pitch rings is shown by a narrow scar or pitchy seam running lengthwise in the bark. A scaler must look closely at log ends to locate rings and determine their size and shape. He should bear in mind that a ring that opens wide may have deep penetration into the log and that numerous rings may penetrate deeper than one or two rings. Make no deductions for rings outside the scaling cylinder, but rings in the large end of logs that enter the scaling cylinder will need defect deductions. It is important for the scaler to make sawmill visits to develop judgment in making ring shake deductions.
3. The need for considering the number of rings, ring location, ring class, ring taper, and the scale of any solid core often makes pitch and shake rings a complex scaling problem.
4. The basic procedure for scaling pitch and shake rings is to square the defect and replace a sound core. Rings are measured and averaged for size in the same manner as log diameters (code 17.3).
This rule in formula is:
Logs to 14 feet inclusive: (large ring +1)2 -(core ring scale)
Logs 16 to 20 feet inclusive: (average ring + 1)2 -(core ring scale)
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Example 1: A 14-foot log 21 inches in diameter has an 8-inch shake ring showing in the large end (fig. 45). The defect extends an estimated 8 feet.
Using the shortcut procedure (code 22.4), deduct as follows:
9 x 9 = 81 to the next higher 10 = 90 board feet
90 x 8/16 = 45 to the nearest 10 = 50 board feet
Replace 7-inch core (allow 1-inch taper), 8 feet long
Deduction = 50 - 10 or 40 board feet (4 Decimal)
(This is easy to compute with the Coconino scale stick.)
Example 2: A 16-foot log (fig. 46) has a 6-inch shake ring showing at the small end and an 8-inch shake ring showing at the large end. Adding 1 inch for waste and averaging the defect (code 22.5): 8 x 8=64 to the next higher 10=70 board feet
Replaced 6-inch log = 20 board feet
Deduction = 70 - 20 or 50 board feet (5 Decimal)
(This is easy to compute with the Coconino scale stick.)
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5. Following are instructions for varying the above procedure in accordance with the circumstances encountered.
a. For one-quarter rings, use the squared-defect method as for checks and do not consider core.
b. For a half ring, take half the deduction for a full ring for the length affected.
c. For a three-quarter ring, take three-quarters of the deduction for a full ring for the length affected.
d. When 2 full rings are not more than 2.5 inches apart, measure diameter of the outside ring. Add 1 inch. Apply squared-defect method for gross deduction. Reduce this by the scale of a log with a diameter of the inner ring.
e. When 2 full rings are over 2.5 inches apart, measure diameters of both rings. Compute separately as per preceding examples and add deductions together.
Example 3: A 16-foot log (fig. 47) has 6-inch and 16-inch shake rings showing at the small end and 8-inch and 18-inch rings showing at the large end. Adding 1 inch for waste and averaging the defect (code 22.5):
18 x 18 = 324 + (Code 22.2) to the next higher 10 =
330 + 20 (For 17" to 21" squares) = 350
Replaced 16-inch log = 160
Deduction for large ring = 350 - 160 or 190 (19 Decimal)
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8 x 8 = 64 to the next higher 10 = 70
Replaced 6-inch log = 20
Deduction for small ring 70 - 20 or 50 (5 Decimal)
Total deduction 240 board feet or 24
(This is easy to compute with the Coconino scale stick.)
f. When multiple rings occur with no recovery between them, square the overall defect and allow for the scale of any inside log surrounded by the rings.
g. For a full or partial ring 2.5 inches or less from the outside at the top end, a perimeter ring, deduct by the diameter deduction method for the portion of the circumference and length affected.
Example 4: A 16-foot log 21 inches in diameter (fig. 48) has a 22-inch shake ring showing in the large end. The defect extends an estimated 8 feet to where the estimated ring diameter is 19 inches. It is thus a perimeter ring at this point and a diameter reduction is used. An 8-foot log 21 inches in diameter scales 150 board feet; an 8-foot log 19 inches in diameter scales 120 board feet. The deduction is 30 board feet or 3.
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h. Make a length deduction if deductions by the squared-defect method exceed the log scale of the part affected.
i. Do not replace the core in determining the defect when the core is too small (normally less than 6 inches) to yield standard-sized lumber.
6. The scaler must remember to follow instructions for application of the squared-defect method (code 22.3) in determining which measurements to use. He should also be aware that ring defects follow annual rings and taper, and remember to treat each core as a new scaling cylinder.
7. A Pitch and Shake Ring Deduction Table for 16-, 18-, and 20-foot logs with rings showing on both ends (table VI in the appendix) can be used instead of making the several calculations normally required. The table is for use in scaling with the Scribner Decimal C rule and provides for taper up to 8 inches.
8. Breakouts from a shake ring sometimes occur. These numerous short radial seams usually are found in a "collar" on the outside of the ring. Obtain the average length of the seams. If 2.5 inches or less (the collar thickness) follow the deduction rule as explained in the preceding item 5. If seams are over 2.5 inches long, determine how much of the collar is affected-a third, half, or all-and use the multiple-ring rule as explained in item 5.
9. Sometimes pockets occur in annual rings. In some softwood species they are called pitch pockets.
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In some hardwood species they are referred to as gum pockets. Usually there is a separation present but the pockets are too short to cause a volume loss. Make no deduction for these pockets unless they are long enough to square out for a deduction of 10 board feet or are so numerous as to cause an actual loss in lumber recovery.
10. In white fir and hemlock a combination of ring and radial shake is common in some areas. The combination often requires a length deduction. Frost cracks, splits, or seams on the outside of the log often indicate the extent or condition.
Rot, Conk. Sometimes this rot is called red ring or honeycomb rot. In eastern species it is known as red rot. (Should not be confused with red rot of ponderosa pine-Polyporus anceps. See table IX, appendix.) In incipient stages it is commonly referred to as "firm red heart." This defect varies in color from purple and light red in early stages to dark brown in mature stages. In the early stages the wood is only stained and requires no deduction. In later stages, the wood breaks down to form a honeycomb appearance. Patches of white substance called "white pocket" appear. These white pockets indicate that the wood is broken down and that a deduction is required.
Deductions for conk rot are particularly difficult. Any one of several methods may apply. Effects of the fungus appear to vary with species, soil, altitude, and climatic conditions. Mill visits and experience are essential for a scaler to interpret what conk indicators mean in the timber he is scaling. Record guides applicable to timber from specific areas.
Generally the point of deepest penetration of conk rot is where a fruiting body or conk enters the log. Here the rot most commonly takes the shape of a crescent. Occasionally it may be in the form of one or more full rings. These may roughly parallel growth rings. When conk stain or conk rot shows in log ends, look with care for conks on the log. Use
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a spud to dig into swollen spots, punk knots, and black limbs. Size of conks is sometimes helpful in determining the extent of rot in some species. Recognize where conks have broken away from logs by punky, yellowish-brown material in the holes where the conks were attached.
Make deductions for white pocket (conk) using the squared-defect method if the defect occurs as a spot in one end. If 1/4 to 1/2 of one end is defective, make a pie-cut deduction of the scaling cylinder affected for the estimated length.
A good plan while on a mill visit is to make a rough chart guide such as that shown in exhibit A (appendix) for conk rot deductions. Use such a chart only for areas and species where it is proved to be applicable by repeated mill visits. Note the average length of rot spread from the last visible indicator.
WARNING: The effects of conk rot are variable. Widespread or uniform use of one chart without essential local modifications and repeated checks could- result in erroneous scaling.
Rot, Heart. Sometimes called center, circular, dry, or red, this rot is found in logs cut from any position in trees. In color it ranges from light brown in early stages to reddish brown in its advanced stage. Fruiting bodies are usually missing by the time the log is ready to scale. This decay is characterized as brittle, dry, crumbly, sometimes with cubical patches and usually with white felt like layers between the patches.
Use the full estimated length of heart rot because it does not taper like stump rot. Make deductions by the squared-defect method for most heart rot.
Example 1: Figure 49 illustrates a 16-foot log with a heart rot extending full length through the log. The defect including allowance for waste
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measures 12 by 12 inches on one end, 6 by 6 inches on the other. Average of these end dimensions is 9 by 9 inches. Using the squared-defect method (code 22.5), deduct as follows: 9 x 9 = 81 to the next 10 = 90 (9 Decimal).
Example 2: Figure 50 illustrates a 16-foot log with heart rot extending 8 feet into the log. The defect including waste allowance measures 10 by 10 inches on the end showing. The squared-defect method gives 10 x 10 = 100 to the next 10 = 110 (11 Decimal). Take 1/2 of 11 or a 6 deduction for this log.
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Use the length-deduction method where the diameter of heart rot equals or approaches the diameter of the scaling cylinder (code 24). Any regional variance from the instructions above should be based on a local guide developed during mill visits. Refer to Rot, Conk, and exhibit A, appendix.
Rot, Sap.
1. Sapwood on logs cut from dead trees, either snags or windfalls, often is in advanced stages of decay. If rotten sap extends over both the length and circumference of the log and the sapwood is still in place, the gross or outside diameter will be measured directly and the average diameter determined just as for green logs. When the rotten sapwood has sloughed away, the gross or outside diameter will be determined by measuring the sound wood within the sapwood and adding thereto the estimated thickness of the rotten sapwood.
To obtain net scale, determine the average diameter of the sound cylinder inside the rotten sapwood (or surface checks) and treat it as a special scaling cylinder, considering any other defects that may be present. The difference between the gross scale of the outer scaling diameter and the net scale of the inner scaling diameter will be the deduction if no other defects are present.
Example: A 16-foot log, 24 inches in diameter at the small end, has a gross scale of 40. If the average thickness of rotten sapwood is 2 inches (fig. 51), the net scale of the log will be that of a 16-foot log 20 inches in diameter, or 28.
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2. When portions of the length or circumference of the sap are sound, the full log diameter including sap will be the scaling diameter and the defect deduction will be treated as follows:
Example: A 16-foot log, 24 inches in diameter at the small end, has a gross scale of 40. If the rotten sapwood is confined to the side which was lying on the ground and averaged 2 inches rotten sapwood for 1/3 the circumference for the full length of the log (fig. 52) the net scale of the log would be 36, derived as
3. Examine logs with dead sapwood carefully. Rot may extend into the heart in the form of pockets. In fire-killed or down timber these pockets may be on one side only. This material should be looked over with care. Use the Hallin hammer or other type of spud to help determine the extent of rot. Deductions for these associated rots should usually be determined by the pie-cut method. See code 23 and figure 14.
4. Occasionally the top end of a sap-rotted log shows a deep rot penetration for a short length only. Make a length deduction for this portion and a diameter deduction for the remainder.
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5. Check merchantability specifications of the timber sale contract (code 16). Some contracts may state that logs with the sapwood decayed will be scaled inside the sapwood. In such cases the sapwood, like the bark, in disregarded in scaling. Gross scale in such a case refers to the heartwood only. Other contracts may provide for scaling such logs "gross," in which case the gross scale is the only recorded volume.
Rot, Stump. Often called butt or ground rot, it is found only in the butt portion of trees as the name implies. Color varies from light brown to dark reddish brown. Swelling on the outside of a log may be an indication of defect length but not always so. Where swellings do indicate rot, decay seldom extends far beyond such swelling. The rot may be either blunt or conical. Splits on the side of a log, sometimes due to weakness caused by rot, aid in estimating decay length. Mill visits are the best way to find out whether the local stump rot is generally blunt or conical. It may be desirable to develop a local chart guide of the type shown by exhibit A, appendix.
The length of penetration of stump rot seldom exceeds 16 feet and most commonly runs 2 to 8 feet. If mill visits show that the rot is generally blunt at the end, the amount of defect will be determined in the same manner as heart rot. If the rot is conical in shape, the amount of standard-length lumber which will be recovered along the taper of the rot must be considered. See figures 53 and 54. Use the squared-defect method unless the size of the defect is so large as to approach the diameter of the scaling cylinder and a length cut is indicated.
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Example 1: Figure 53 illustrates a 16-foot, 24-inch log with stump rot averaging 14 inches in diameter. Visible swelling in the log indicates total length is 6 feet. Because of the cone shape of stump rot, not all of the 6-foot portion is lost. At the point where the rot penetrates deepest, the log will not produce longer than 10-foot lumber, but along the sides of the rot cone within the scaling cylinder, it should produce 12- and possibly some 14-foot lumber. Average the defect length. In this example use 4 feet as the average length. The squared-defect method (code 22.4) gives 15 x 15 = 225 + 10 raised to the next 10 = 240 (24 Decimal), the deduction if the defect extended 16 feet. The average length, however, is 4 feet, 1 the length of the log, or a deduction of 6.
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Example 2: Figure 54 illustrates a 16-foot, 18-inch log with stump rot averaging 16 inches in diameter. The size of this defect is so large as to approach the diameter of the scaling cylinder and calls for a length deduction. In the type of stump rot illustrated, a 4-foot-length cut should equal the loss from rot. The difference in scale between a log 12 feet in length and 18 inches in diameter and one 16 feet is 5, the proper deduction for this log.
Stain. Stain normally affects quality of lumber recovery rather than quantity. Generally stains are blue or brown. No deduction is made when the stain is firm and light in color, but deduction is made when stain is associated with actual rot and there is a breakdown of the wood. When to make a deduction for stain in some species is difficult to know. Examine dark stain for rot, weather checks, or wormholes. Brown spots are generally an indication of actual rot. See Rot, Sap.
Earlier stages of actual breakdown of wood can be determined frequently by driving the corner of a sharp handax bit, or Hallin hammer, into the end of a log and twisting. If fibers break across, the wood is weakened. Fibers of firm sound wood will cut clean and pull straight out rather than tear or break across.
The significance of mineral stain and firm blackheart varies in different areas. Become familiar with any local guides concerning these indicators.
Sweep. Sweep compared with crook is less abrupt and more continuous. Sweep is often long enough to affect more than one segment. Varying the bucking lengths of logs will often reduce the loss due to sweep. Report poor bucking practices to the District Ranger. Scalers will deduct for sweep in logs by scaling as presented unless otherwise instructed (code 17.5).
Make deductions for sweep as follows:
1. Measure the length of the log affected by sweep.
2. Deduct the fraction of this length lost in sawing, considering standard length lumber recovery.
3. Make a length deduction accordingly.
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Figure 55 illustrates a 16-foot, 20-inch log with sweep affecting 6 feet of the scaling cylinder. It is estimated that one-third of the affected area will be lost in sawing. In this case a 2-foot-length deduction is made.
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Sweep in combination with an interior defect such as rot or shake is likely to cause a cull log (fig. 56).
Wormholes. Wormholes are classed as pin size, not over 1/16 inch in diameter; small, not over 1/4 inch in diameter; and large, over 1/4 inch in diameter. Pin and small wormholes are caused by different kinds of beetles; large wormholes by wood borers or grubs. Wormholes are common in logs cut from
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snags and in some down timber. When found in sap rot, the deduction for rot will also include any deduction for wormholes. When found in connection with catfaces and fire and lightning scars, include wormholes in the measurements of those defects.
Make deductions only for large (grub) wormholes when they are massed and this condition causes an actual loss of volume. Generally use the pie-cut deduction method (fig. 57). The diameter-deduction method may occasionally be applied when wormholes are uniformly distributed around the log.
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