Calculation help please.

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ChrisNJ

Feeling the Heat
Sep 25, 2009
380
Burlington County
Long time no see guys, tried the sticky calculators but could not get it to work, what do you think the volume of these would be cord wise ?

The oak logs are approx. 20-28 inch in diameter and approx. ten feet long (9 of them)

Now I would average 24 inches by 10 ft x 9 = 180sq ft ? = 1.4 cords ? How does that look.
 
Long time no see guys, tried the sticky calculators but could not get it to work, what do you think the volume of these would be cord wise ?

The oak logs are approx. 20-28 inch in diameter and approx. ten feet long (9 of them)

Now I would average 24 inches by 10 ft x 9 = 180sq ft ? = 1.4 cords ? How does that look.

Let's lay those logs out. We know a cord is 4' x 4' x 8'. If you grab two of those logs and lay them side by side you are now at a 4' width. And if we take 2 more logs and lay them on top of the other two we are at 4' high (two of the dimensions of a cord).

So we've now used 4 logs and we've got a width of 4', a height of 4', and a length of 10'. A cord is 4'x4'x8' = 128ft3, 4'x4'x10' = 160ft3 and you still have 5 logs left. So let's double those 4 logs, 160 (x2) = 320 ft3 (that is 8 logs). Now you have one log left. So 320/8 = 40ft3 (volume of one 10ft log). So 320ft3 + 40ft3 = 360ft3.

360/128 = just a little less than 3 cords. Cut firewood may contain more air space than logs, so maybe 9 logs is a bit over 3 cords.
 
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I'd do the calcs like this: radius of a log = 12 inches = 1 ft. The area of the end of a log is Pi r^2 = 3.14 x 1^2 = 3.14 square feet. Volume of a log is 10 ft x 3.14 sq ft = 31.4 cubic feet. 31.4 cubic feet per log x 9 logs = 282 cubic feet of solid wood. A cord is about 85 cubic feet of solid wood, so you have 282 cubic feet / 85 cubic feet/cord = 3.3 cords.

Remember a cord is 128 cubic feet of stacked wood and the air between them. It is only about 85 cubic feet of solid wood.
 
Geez I was way off, thanks a lot.
 
+1 to wood duck.

OP, you have a lot of wood on your hands there.
 
Let's lay those logs out. We know a cord is 4' x 4' x 8'. If you grab two of those logs and lay them side by side you are now at a 4' width. And if we take 2 more logs and lay them on top of the other two we are at 4' high (two of the dimensions of a cord).

So we've now used 4 logs and we've got a width of 4', a height of 4', and a length of 10'. A cord is 4'x4'x8' = 128ft3, 4'x4'x10' = 160ft3 and you still have 5 logs left. So let's double those 4 logs, 160 (x2) = 320 ft3 (that is 8 logs). Now you have one log left. So 320/8 = 40ft3 (volume of one 10ft log). So 320ft3 + 40ft3 = 360ft3.

360/128 = just a little less than 3 cords. Cut firewood may contain more air space than logs, so maybe 9 logs is a bit over 3 cords.

I like this method, it gets you a quick estimate that you can do in your head. I look at a 24" log and say at 8' it is 1/4 cord or I need 32 running feet to get a cord. For three cords I need 96 running feet. OP has 90 running feet so he has just under 3 cords. Wood duck's figure that a cord of wood contains only 85 cu feet of solid wood can't be correct in my opinion. As 85/128= .664. I don't think that anybody here is going to tell you that a 'cord' of wood neatly stacked is 2/3 wood and 1/3 air. Mine certainly don't look like that to me and I don't think I could stack that much air into one if I tried without criss/cross stacking.

This method figures automatically that you have about 100 of solid wood/cord or the air within a stack is 21.5%. It is the difference in area between a square and a circle drawn within it.
 
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