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Log Scaling References

1. 1905 - US Forest Service, Use of National Forests Here is the PDF
First requires Scribner. No mention of Decimal C

2. 1908 - US Forest Service, The Use Book Here is the PDF

- Requires Scribner Decimal C.
- Maximum Scaling Length set at 16 feet
- No exception for West of Cascades; no "Long Log" rule
- First Scriber Decimal C Table that I know of
- Multi-segment logs scaled at top end and then allow 1" taper per 8 feet

3. 1911 - US Forest Service, Henry S. Graves, The National Forest Manual Here is the PDF

- Requires Scribner Decimal C.
- Maximum Scaling Length set at 16 feet
- Specific Exception added for Timber West of Cascades; Maximum scaling length set at 32 feet for "Westside Scriber"
- Scriber Decimal C Table contains entries up to 32 feet and 120" in diameter
- Multi-segment logs scaled at top end and then allow 1" taper per 8 feet
- Mechantability rule introduced at a minimum of 33 1/3 percent

4. 1916 - US Forest Service, Henry S. Graves, Instructions for the Scaling and Measurement of National Forest Timber Here is the PDF

- Same as 1911: Scribner Decimal C, Scaling Length set at 16 feet, Westside Scaling Length 32 feet; Mechantability minimum of 33 1/3 percent.
- Added Taper Table for 32 foot Logs
- Added Cubic Foor Measurement for Pulpwood (and Firewood)

5. 1928 - US Forest Service, William B. Greeley, Instructions for the Scaling and Measurement of National Forest Timber Here is the PDF

- Same as 1916: Scribner Decimal C, Scaling Length set at 16 feet, Mechantability minimum of 33 1/3 percent.
- Westside Scaling Length increased from 32 to 40 feet;
- Decimal C Table extended to cover 40 foot logs
- Taper Table adjusted to cover 40 foot logs

The following excerpt seems to require the measurement of the diameters at both ends long logs (42'+) and then apply the taper evenly over the length to determine the diameters of the segments other than the top segment. The language seems to allow for an exception for butt logs (logs flared at the butt); in this case, the Taper table can be used.

6. 1935 - US Forest Service, F.A. Silcox, Instructions for the Scaling and Measurement of National Forest Timber Here is the PDF

- Same as 1928: Scribner Decimal C, Scaling Length set at 16 feet, Mechantability minimum of 33 1/3 percent, Westside exception of 40' maximum scaling length.
- Specifically defined the Cubic Scaling rule as the average of the top and butt diameters, divided by two and squared, and multiplied by pi (this is the area of a circle with radius of the average diameter divided by two). This product is then multiplied by the length of the log.

7. 1941 - US Forest Service, National Forest Scaling Handbook Here is the PDF
Reprinted in 1951

- Same as 1935: Scribner Decimal C, Scaling Length set at 16 feet, Mechantability minimum of 33 1/3 percent, Westside exception of 40' maximum scaling length.
- International 1/4" Scale authorized for use in Scaling. Volume rounded to the nearest 5 BF.

8. 1973 - US Forest Service, National Forest Log Scaling Handbook Here is the PDF
This edition was a major rewrite of many rules

- Maximum scaling length changed to 20 feet for both East and West of the Cascades. Local Regions were allowed some authority to modify this general rule: "variation from the above standards may be authorized by the Regional Forester by special instructions included in Regional Supplements."
- Decimal C Scale Volume Table only goes up to 20 feet in length
- Logs over 20' need to be scaled at both ends. The taper is apportioned over the length of the log.
"When logs exceed the maximum scaling length, scale them as two or more segments as nearly the same 2-foot length as practicable. When it is necessary to divide a log into unequal lengths, make the butt segment(s) the longest."
Odd-Even Taper Rule:
"Taper is even when it can be apportioned in an equal amount to each segment such as 4-inch taper in a 2-segment log can be apportioned 2-inches to each segment, and uneven when it cannot."
"17.41 - Distribution of Even Taper"
"Divide the taper by the number of segments, and add the taper per segment to the top diameter to obtain the diameter of the second segment. For a 3-segment log, add the taper per segment to the diameter of the middle segment. The resulting diameter should differ from the butt diameter by the taper per segment."
"17.42 - Distribution of Uneven Taper"
"Scale logs with taper in uneven amounts, by applying the excess taper to the top segment(s). Trees naturally grow with increased taper in top logs, as a check of taper tables or of actual taper measurements will demonstrate."
"The rule of distribution of taper in long logs is as follows:"
"1. For two-segment logs with taper not divisible by 2, add an inch and divide by 2. This is the amount of taper assigned to the top segment."
"2. For three-segment logs, raise total taper to a number divisible by 3 and divide. This is the amount of taper assigned to the top segment. Distribute the remainder of the taper as in a two-segment log."
- Butt Logs:
"17.43 - Taper in Butt Logs"
"The taper in long logs which have the butt cut at one end cannot be determined in the same manner as other logs. Average taper can be determined by local studies conducted by species."
"Uniform butt log tapers as determined by studies may be shown in the Long Log Table, Table III in the appendix chapter. Use of this table shall be in accordance with instructions issued by the Regional Forester. In the absence of authorized taper tables, scale on the basis of actual taper."
- International 1/4" Scale was changed to be a "Decimal C" rule, meaning volumes are rounted to 10 BF and the trailing zero is dropped.
- Cubic rule changed to rely on the Samial Log Scale Rule.

9. 1980 - US Forest Service, National Forest Log Scaling Handbook Here is the PDF
This edition was pretty much the same as the 1973 Edition.

10. 1994 - US Forest Service, National Forest Log Scaling Handbook Supplement 10 Here is the PDF
This Supplement provide the Regional Authority to set the maximum scaling length to 40 feet west of the Cascades.

11. 2006 - US Forest Service, National Forest Log Scaling Handbook Here is the PDF
This edition was pretty much the same as the 1973, 1980 Editions.