Accuracy of Different Log Scales
How many chunks in a dang whack? That depends on how you measure it. (And if you're talking beer, we use hogsheads per hectare.) March 10, 2008
Question
Three standards... buy why? My whack of logs scales out Doyle, 1728; International, 2160; and Scribner, 2040 BF. What's the trick - buy on the Doyle, sell on the International? Is this some racket? I had a little gentlemanly discussion with a guy that insisted I buy on his International scale. What is the best way to accomplish this difference? I was using the Doyle scale. Some folks in the east use one scale, Western USA another, and Canadian folks yet another. Can someone make sense of this?
Forum Responses
(Sawing and Drying Forum)
From contributor P:
I have seen in-depth discussions of the three methods. The surprising part of the discussions, for me, was how inaccurate the Doyle method is. The second big mystery is why they still all remain in use.
International 1/4" seems, on average, to be the most accurate, but the least used in my area. I had a customer call today and list the log sizes he had. I used WOODWEB calculators with the International scale to estimate his yield and give him a ballpark figure. At least that figure will match to some realistic degree what he really has in his logs.
I sometimes think that the Doyle and Scribner scales were designed to favor one party or the other at that time when they were developed. The International seems most even-handed. Please note that this is purely my opinion.
From contributor J:
It really depends on what everyone you deal with uses. If they use Doyle (like my area) and it's the accepted U/M, then that's the way to go. You could go to cubic meters or KG, but nobody could relate to it!
From contributor R:
Three standards can be very tricky... each one is somewhat accurate for certain size logs, but they are all yield estimates. Averaging all factors, International should give the most accurate prediction. If the logs you mentioned were small, I can understand your seller arguing to use International, since Doyle so greatly underestimates small log yield. As a sawmill operator, the best thing you can possibly do is a short yield study. Scale a load with all three rules, saw the logs, and see what your over/under run is for each. On a thin kerf mill, with careful sawing, it is easy to create large overruns on each of the scales. Once you are armed with that information, you can better evaluate your costs, and you can determine fair stumpage prices to offer. If you are a logger or log broker... go figure. It's anyone's guess what's the best one to use.
From the original questioner:
Thanks. I probably need to find out what the others in my area are using. I just want to be fair to him and myself. I will probably go with International - middle of the road until further investigation.
From Professor Gene Wengert, forum technical advisor:
International scale is closer to reality (the yield estimates are close to actual) when using a 1/4" kerf than the other two scales. Actually, there are about 150 scales available for use. As stated, they are estimates of the yield, with some of them accommodating the fact that smaller logs also have more handling time, so the yield estimate will be smaller than reality to adjust the price.
In general, Doyle is used in the East and South; Scribner is used out West. If you buy on International 1/4", then you also need to pay lower prices per BF for smaller logs, or else you will end up paying too much. So that is why International is the largest number in your test.
Note that prices for logs are not the same when comparing the scales. When scaled International, the price will be less than for Doyle. Hence, when you buy Doyle and sell International, you will end up with the same value for the logs. (Psychologically speaking, it is better to pay a certain amount for logs and not tell the supplier that because he has supplied small logs, you are going to lower your price. Therefore, using the Doyle scale will provide you this automatic adjustment for small logs.)
Usually Doyle and Scribner are close, but in your case, your Doyle scale measures to the closest foot and the Scribner has been rounded to the 10 BF. There is an International 1/8" rule too, but it is not used, but would be closer for thin kerf.
From contributor C:
Gene is on the money. I cut grade and only buy on Doyle scale. The pallet guys in the area buy on International scale, but their yield on small logs in very different than when cutting grade. For me, small logs mean a lot of bark and sawdust, but little lumber unless I cut live edge for the rustic furniture (but this is a limited market).
From contributor O:
What is a whack?
From contributor W:
In my area, it's more than three - a pile or a bunch. Maybe even a truckload.
From contributor N:
All 3 scales are in use in my area, and I've used all 3. When the logger asks what scale I use, I tell him I'll use any one he prefers, but the amount of money he's going to get will be the same. I've seen some comments that say International scale is the most accurate, but it really depends on what size logs you are sawing. If I am sawing a bunch of 11" and smaller logs into 4/4 with minimal pallet blocking, I'll be under the scale every time, especially after trimming and cutting off for grade. If I buy on Doyle, my grade lumber comes out to what the log scales and the overrun is the low grade pallet material. But if you are buying logs, you really have to use what your competition is using, or you will get complaints about prices or footage.
