Doyle or International

Jeff · May 12, 2005, 08:55:29 AM

Actually, I dont know what happened there. Must of got click happy.

Ron Wenrich · May 12, 2005, 07:01:21 PM

I've found one that is (0.22*D^2-.71D)*.904762 per 4' section. Then it figures a 1/2" taper per 4' section. It also said to add about 10.5% to get the 1/8 scale. Source: Forestry Handbook

Mike_Barcaskey · May 13, 2005, 10:05:39 AM

ok, now I'm really corn-fused

let's figure the bf in a log 10 foot long, 12 inches dia

the Forestry Forum calculator gives these totals
International 61
Doyle 40
Scribner 54

My pocket Wood-Mizer Log Rule and Lumber Scale gives these
International 55
Doyle 40
Scribner 50

why the difference in International and Scribner?
various log dimensions are all different

Ron Wenrich · May 13, 2005, 11:35:52 AM

For starters, the calculators use formulas that were developed by the USDA. We developed the log calculators first, which later developed into the tree volume calculator. In order to get figures that are consistent with tree volume charts, you have to use those formulas for the logs.

There are several different formulas for International scale. Here's another one. 0.049762*L*D^2+0.006220*L^2*D-.185476*L*D+0.000259*L^3-0.011592*L^2+0.042222*L That forumla gives you 55 bf.

I used the one that is accepted by the industry as a standard, and it was easier to program. Wood-mizer may be using the 1/8 scale. Usually you will see it listed as Int 1/4 or Int 1/8.

For Scribner, there are 2 ways of comupting that. Here in the east, we use the Scribner as it computes. But, there is a Scribner Decimal C. It is used mostly on the West Coast. It basically rounds the Scribner computation to the closest 10, then they drop the last 0. It must fit on the scale sticks better. :D You just have to multiply the Scribner Decimal C scale by 10 to get to a rounded version of of Scribner. Are all of there Scribner figures ending in "0"?

In the end, it really doesn't matter what scale you use. A log is worth so much money. Whatever scale you use, you should come up with a dollar value that is pretty close. The $/Mbf changes with each scale.

Here's a calculator we have on the Timberbuyers.net site. It compares the difference in log values under different scales. I don't see it on this site.

http://www.timberbuyer.net/logvalue.htm

Jeff · May 13, 2005, 11:47:59 AM

Its here, I must have over looked it.

https://forestryforum.com/calcs/logvalue.htm

I have added it to the tool box

https://forestryforum.com/board/index.php?action=toolbox

beenthere · May 13, 2005, 11:52:29 AM

Quote from: Ron Wenrich on May 12, 2005, 07:01:21 PM
I've found one that is (0.22*D^2-.71D)*.904762 per 4' section. Then it figures a 1/2" taper per 4' section. It also said to add about 10.5% to get the 1/8 scale. Source: Forestry Handbook

Ron
I found that formula also in the Freese publication "A Collection of Log Rules" under the 1/4" Int'l rule.

It is attributed to Judson Clark in 1917 to appease the band mills that couldn't quite get the yields predicted by the 1/8" Int'l rule (which was also set up for 1/2" taper and for 4' log sections).

Log rules are good for just giving one an estimate of what is in a log. When deciding what to pay for a log, or what to sell a log for, having a general idea of the bf in the log (or tree) helps one to make the decision. Getting the estimated bf from the log depends on many things, of which the accuracy of the rule used is but one of them.

Ron
Good response on the log calculators and explanation of the rules. At least the surface of what all has been involved and revolved over the years has been scratched. For those interested in what the mathematicians and forest mensurationists and statisticians have struggled with over the last 100 years, the Collection of Log Rules is a pretty good summary, IMO.