Log weight

      Locating a chart and doing the calculations. September 2, 2002

Q.
I am looking for a chart of typical weights / cord (or any other volume measure) of fresh cut logs of various types. I know that weights will vary due to log size, but average is fine. I have found a chart showing this for 1000 board feet of lumber at different moisture contents. In our neck of the woods, white spruce stud wood is very close to 4400 pounds / cord.

Forum Responses
From contributor R:
I wanted the same thing to help with determining a legal load on my trailer. I made the assumption that a log was a perfect cylinder (false!) and used the following formula in Excel to calculate the total number of board feet in the log.

PI()*(($A12/24)^2)*C$2*12

Column A contains the diameter of the tree in inches. Row 2 contains the length of the log in feet. I then filled in the table for the max log sizes I was apt to come upon. By measuring the larger end of the log and the larger diameter on oval logs I make sure I am estimating high.

I then used the lumber weight calculators in the Resources area to calculate the weights for various species per 1000BF at a high moisture content. I again used Excel to build a table with each species in a column. I used a row for 10, 20, 30, 40, 50 60, 70, 80, 90, 100, 200, 300, 400 and 500 BF.

Most of the logs I obtain are less than 1000BF, so by adding at most 3 numbers, I can come up with an approximate weight of the log.

I printed both sheets out, reduced to a wallet sized photo, and keep them in my wallet for ready reference.



From contributor J:
A more accurate way might be to measure both ends of the log and then halve it to get the volume of a perfect cone. Of course, you would probably over-estimate most of the time, due to the swell at the base of a butt log. You could also measure the center of the log, assuming you could get your tape around it, but this way you would come up short of the true weight.


There are a bunch of tables in ULTILIZATION OF HARDWOODS Vol. 3 by Peter Koch, US Dept of Agriculture Handbook No. 605. Any library can get this through interlibrary loan.

Gene Wengert, forum technical advisor



From contributor R:
Contributor J, I know that my method really over-estimates the weight of the logs. However, I would rather be safe and not get a ticket than try to optimize my trailer load.

I also wanted something very simple to look up. I thought about using both end diameters of the log, but that would have either required many tables or quite a bit of calculation. I guess I haven't got a good enough feel for the log weights just by looking at the log, so I want a little extra help. I don't necessarily even use a tape to get the log size. I just measure the diameter with my hand and step off the length. It is close enough for what I am trying to do. If I was in this commercially, I would do something much different.



The log weights in KOCH that I mentioned are based on 4800 logs. Some sample values are for a 16" x 12' log of ash, 1010 pounds, hickory 1267 pounds, soft (red) maple 1059 pounds, red oak 1323 pounds, white oak 1262 pounds and yellow poplar 1262 pounds. Of course, there are numbers for other diameters and lengths. As the volume of such logs in this example are 130 BF (Int.), 120 BF (Scribner) and 108 BF (Doyle), you can figure out weights per MBF log scale too. For example, for 1000 BF of y-p logs, the weight is 9707 pounds Int 1/4", 10,500 pounds Scribner, and 11,6700 pounds Doyle. Compare these to the table values of 6750, 8100, and 10,000 pounds respectively. Wow! What a big difference! (Another study shows the weight for y-p 16"x12' to be 1094 (instead of 1057) pounds if the bark is on, but 934 pounds if the bark is first removed.)

Let's try red oak: Actual weights based on 4800 logs are 10,200(Int), 11,000 (S), and 12,250 (D), compared to the table values of 9100, 11,000 and 13,550.

Ash: 7800, 8400 and 9400 pounds compared to 6900, 8300, 10,250!

Gene Wengert, forum technical advisor



Something I did with my log trailer by experimentation was to scale a few loads, save scale tickets, and count the logs on each load. Came up with my own rule of thumb. Also adjusted my bolster heights so that when I'm loaded, even with the bolsters, I have a 12 ton load max. This puts me just under my legal load. If I haul pulpwood, itís usually off a little because of lengths, but works out good on saw logs. Once you get a feel for it you can also look at how your truck and trailer are sitting and know whether you've got a load or a load-and-a-half.

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