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Tree + cord count

Discussion in 'Firewood, Heating and Wood Burning Equipment' started by jhoff310, Apr 26, 2010.

  1. jhoff310

    jhoff310 AboristSite Guru

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    My neighbors friend wants me to come out and cut up some trees for the wood. Is there some type of formula for figuring out the number of cords per tree? I am not really worried about how much wood I drag home I was just curious?

    Jeff
     
  2. Steve NW WI

    Steve NW WI Unwanted Riff Raff.

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    From a U of Neb firewood publication:

    Table II. Firewood cutter’s rule of thumb.
    Tree Size Number of Trees
    (diameter at breast height) Per Cord
    5------------------------------46-55
    6------------------------------21-33
    7------------------------------14-18
    8-------------------------------9-14
    9-------------------------------6-9
    10------------------------------4-6
    16------------------------------2
    22------------------------------1

    Pretty handy .pdf file on firewood. I have it saved on my computer. Link here: LINK
     
  3. Wife'nHubby

    Wife'nHubby Addicted to ArboristSite

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    Steve,

    Is there a formula to figure how many cu ft in a log? Yeah, it's probably pi something - but I can't seem to find a formula nor remember how to do it. Reason is: A CL ad had 8' logs: one @ 7", one @ 8", one @ 9" and two at 10". I was trying to figure out cu ft. The best I could figure is about 1/2 of a face cord. I passed on the deal but would like to know how to figure out cu ft of a log if needed in the future.

    Shari
     
  4. Steve NW WI

    Steve NW WI Unwanted Riff Raff.

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    Shari, google volume of a cylinder calculator, and plug your numbers in. Someone posted a more accurate method using small and large end diameters, but I can't find it right now. Just use average dia and it will get close. Make sure to enter everything in feet, IE 6"=.5, 8"=.67 you get the idea

    Here's one I found: link note that it uses radius, which is half the diameter.

    Also remember that you'll be getting solid wood volume, figure 80cf or so of solid wood for a cord.
     
  5. mickeyd

    mickeyd ArboristSite Operative

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    how do you take into count the height of the tree and how many usable branches
    MD
     
  6. Dalmatian90

    Dalmatian90 Addicted to ArboristSite

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    You don't.

    It's only a rule-of-thumb to give you a quick estimate.

    It's a not a timber cruise where you're measuring multiple dimensions of the tree to get an more accurate estimate.
     
  7. bayard

    bayard AboristSite Guru

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    24 inch maple

    i have gotten 2-2.5 cords per tree,thats with a good crown.k
     
  8. Steve NW WI

    Steve NW WI Unwanted Riff Raff.

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    Yup, just a quick guesstimate. Note the wide swings in trees/cord in the smaller diameter trees.

    I've often wondered how much difference there is between say, a 24" oak growing tall and straight with a minimal top in the forest, and a same sized (DBH) oak out in the middle of a pasture, generally only 40' or so high, but with a huge mass in the tops? I'm personally betting on that short stout pasture tree, but it's gonna be a lot more of a pain to cut up.
     
  9. Gunther274

    Gunther274 ArboristSite Operative

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    Scribners chart. Takes you from a height measurement and diameter to cords.
     
  10. Gunther274

    Gunther274 ArboristSite Operative

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    A 24" oak that is tall if you want tall, 64 feet, is 1.28 cords.

    64 feet of 30" wood is just over 2 cords.

    8 feet of 12" wood is .07 cords

    8 feet of 15" wood is .107 cords

    8 feet of 18" wood is .155 cords

    8 feet of 20" wood is .194 cords

    8 feet of 24" wood is .288 cords

    8 feet of 30" wood is .43 cords



    I have a chart with heights of trees right in front of me now, if any of you want to know some cord amounts I can figure them out in a second.
     
  11. Wife'nHubby

    Wife'nHubby Addicted to ArboristSite

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    Gunther - What you posted helps me alot! Thanks!

    Shari
     
  12. Gunther274

    Gunther274 ArboristSite Operative

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    Just ask I got everything up to 30 inches on this chart, and I can do a short bit of math to figure out bigger stuff. I can do tree length too, it was just easy to give 8 foot lengths because its more common for folks to use that are not actually doing a timber cruise...
     
  13. Gunther274

    Gunther274 ArboristSite Operative

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    I can tell you how to find the volume in cubic feet of a log. This is assuming the diameter is close to uniform for the length. This will not work for heavily tapering logs, or long tapering logs. For simple work, its best to measure short logs with uniform diameters. Its a simple bit of forest mathematics.

    First you take your diameter times itself. (inches)

    Ex. 12 x 12=144

    Then you multiply that by the "foresters constant" which is .005454

    144 x .005454= .785376 This is your cross sectional area(basal area) in square feet. Dont ask me how it works, but the math magically converts one number into something useful.

    Then to finish off you multiply your square footage by your length in feet.

    .785376 x 8' =6.28 cubic feet.


    The cord numbers I gave in the above post are figured with air space already. If you do the math with the 6.28 cubic feet listed above you will get a lower number.

    Ex. 6.28 cube foot log divide by 128 cubic feet (cord) you get the exact percent of volume of a cord without air space. So you get .049086.

    The chart is figured with air space because the mills buy the air space in a cord when they buy wood, so its pre figured.

    Whew!
     
  14. Gunther274

    Gunther274 ArboristSite Operative

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    Hey wifenhub, you have .192 cord with them logs you listed there. The guy selling it is a real clown. Just curious what is the $ he is asking????
     
  15. DJ4wd

    DJ4wd ArboristSite Operative

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    Im a tactile learner so please excuse my overly simple questions. I just fell an hickory that was 22" wide and 70 ft tall, how would I figure it out? Would I need to measure around the base?
     
  16. slowp

    slowp Tree Freak

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    Make sure you measure diameter and not circumference.

    Also another thing to know is if the method of computing the volume requires you to only measure the height to the top of the usable wood.

    An example? I use a conifer for an example tree. The entire tree is 140 feet high to the tippy top of the tree. That entire tree is not usable for lumber so I better have a program on the computer that will adjust it for local conditions.

    The old method was to measure the height to the top of the Merchantable wood, say 115 feet on that 140 foot tree to a 5 inch top. Or, in the case of a large old growth, where you figured the tree was going to bust up when felled.

    Confused yet? :confused:
     
  17. Wife'nHubby

    Wife'nHubby Addicted to ArboristSite

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    Well, first of all I passed on the deal so that is over. Second he was saying it was a face cord - which, according to my rudimentary figuring at the time it was not. He was asking $50 - unseasoned, in log form.

    Edit: Around here, a face cord = 1/3 of a full cord with a full cord equaling 128 cu ft. So he was saying he had 42 cu ft.

    Shari
     
    Last edited: Apr 28, 2010
  18. 1harlowr

    1harlowr ArboristSite Operative

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    Pi x radius squared x height Then divide by 128 (volume of a cord in feet) Then add about 10% to account for increase in volume due to splitting. Gives a pretty easy rough estimate.

    The example of the 22" diameter hickory by 70' long:
    22" diameter is a radius of 11" is a radius in feet of 0.917
    3.14 x 0.917squared x 70= 186.59 186.59/128=1.46 1.46 x 1.1= 1.6
    That's assuming a butt end of a log that has very little taper. If it tapers much, you have much less wood.

    Make sure everything is in feet. Sorry I'm not smart enough to make my computer use the Pi, squared, times, and divide symbols :dizzy:
     
    Last edited: Apr 28, 2010

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