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Author Topic: How many logs does it take to make a cord  (Read 9544 times)

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Offline weirmeister

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How many logs does it take to make a cord
« on: July 16, 2011, 11:42:36 pm »
I'm trying to determine how many logs it takes to make a cord ( for log buying purposes).  A cord is 128 cubic feet.  My thinking takes me to converting cubic feet into board feet.  According to Google 1 cubic foot equals 12 board feet, so it will take 1536 board feet to make a cord.  That is about 7 logs 18 inches on the small end and 16 feet long.

Am I going about this the right way??

Doug

Offline Tom the Sawyer

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Re: How many logs does it take to make a cord
« Reply #1 on: July 16, 2011, 11:50:04 pm »
Remember that a cord is not a solid 128 cubic feet, there is quite a bit of air in there considering how tightly you stack it.  It might be better to figure it on the weight of a cord of a specific wood versus the weight of a log of the same species.  I believe there have been a couple of threads on this topic.

From a University of Nebraska site, the weight of a cord of red oak is just under 5000 lbs.  Using the calculator in the Forum Toolbox, that would be approximately a 16' red oak log that averaged 29" in diameter.  If that log was 28" on the small end it should have 580 bf on the international scale.  That is useable boards, the firewood would include the bark, slabs, etc.

In terms of 18" diameter logs, it would be approximately 43' in total length per cord.
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Offline beenthere

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Re: How many logs does it take to make a cord
« Reply #2 on: July 16, 2011, 11:56:46 pm »
Tom the Sawyer is right.

Here is a thread from the forum
http://www.forestryforum.com/board/index.php?topic=1344.0
south central Wisconsin
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Offline John Mc

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Re: How many logs does it take to make a cord
« Reply #3 on: July 17, 2011, 09:28:03 am »
I've attached a paper from the University of New Hampshire Cooperative Extension. The table at the bottom of the page has estimates of how many cords in a tree given its DBH (Diameter at Breast Height).

I cut would with a community cooperative. We mark a bunch of 3-cord firewood lots each year, and have found this to be pretty accurate once the wood is cut and stacked. We did tend to come up short if the lot had had mostly smaller trees. I can't find the actual table we use right now, but this one is similar.

Also, I don't know if this table would vary from region-to region in the country. It works for us here in Northern-hardwood forest trees.
Small time fire-wooder in a neighborhood cooperative.

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Offline SwampDonkey

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Re: How many logs does it take to make a cord
« Reply #4 on: July 17, 2011, 10:46:10 am »
When doing your figuring keep in mind that if your buying random length your cordage estimates are going to vary somewhat. So if your looking at that load someone drove into the yard and there are sticks of all lengths on the truck, just know that cordage estimation is going to be just as variable. We only based our estimates at the marketing board on 4 and 8 foot wood. And you could actually have 85 ft3 up to 100 ft3 in wood volume because of different diameters. If you look at the green weights of woods, we chose 100 ft3 (cunit) as the standard which meant we had 5500 lbs of wood in a cord of hardwood (maple, beech, yellow birch). Oak is a lot heavier when green, but since we have so little of it up here, we didn't bother factoring it in. As a rough estimate, several folks use 2 cords per thousand as a rule of thumb across all species. The logging contractors used this to pay cutters and landowners. Up here, loggers don't know what a m3 is, and even suggesting MBFM is way over the top. Cords is what they've always cut and there's no changing it. :D

Good luck with your figures. ;)

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Offline weirmeister

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Re: How many logs does it take to make a cord
« Reply #5 on: July 17, 2011, 08:13:10 pm »
Thanks for the input.  I think I will go with 500 bf per cord.  The weight measurement doesn't work since I'm working with Doug Fir and Bay Laurel here in Northern Ca.

Doug

Offline Tom the Sawyer

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Re: How many logs does it take to make a cord
« Reply #6 on: July 17, 2011, 10:53:18 pm »
The weight/species was just to establish a constant.  Weight or species won't make much difference as long as they are the same.  It is all based on the accuracy of the reference charts you use.

If you only want to know how many logs to buy to get a certain number of cords, then introducing board feet into the equation complicates things since there is material left after the board feet are tallied that would be used if firewood.

Calculate the cubic footage of the logs and forget about board feet.  From the same charts used above, green Douglas Fir is estimated at 3319 pounds per cord.  Douglas Fir weighs 38 pounds per cubic foot.  So an accurate cord of Douglas Fir should contain 87.3 cubic feet of solid wood. 

A 15" diameter log (any species) that is 16' long contains 19.6 cubic feet of wood.  So you would need 4.5 of those logs to get a cord of wood.  If they were 20" logs it would only take 2.5 logs, etc.

Tom
07 Timberking B-20, Custom-made log arch, 20' trailer w/ log loading arch, F350 SD flatbed dump.  Princeton piggy-back forklift.  Stihl 025C 16" and a Husqvarna 372XP 24/30" bars.
If you call and my wife says "He's sawin logs", I ain't snorin'.

Offline WH_Conley

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Re: How many logs does it take to make a cord
« Reply #7 on: July 17, 2011, 11:33:11 pm »
I had some junk logs that I measured, just to see. 500 board feet doyle rule per cord, 128 cubic ft was pretty well dead on.
Bill