I've wondered the answer to this question. I've used the "most reliable" place to get information, AKA the Internet to research the answer and the usual answer is that a cord of wood is really only 80-85 cu feet of wood. If you do a small amount of math you will realize that all the experts are telling us that a neatly stacked cord of wood is really 1/3 air and 2/3 wood because 85/128=.664. I think about that a while and I reason that if a row of wood is 1/3 air and I shoot some bullets at it, the bullets will pass directly through the row 1/3 of the time. (Which is a little off because of the diameter of the bullet but we can ignore that.) A quick look at my stacks and any other picture that I can find tells me that that isn't possible. There isn't that much space. There is no way that a cord of wood cantains only 85 cu feet of wood. So how much does it contain? How to figure it out? Build a box that measures 4x4x8, stack a cord within, then see how much water you can pour in around it? Doesn't sound to practical, especially when the the top row floats away. After some more thought I realized that I could figure it out if I thought of the wood stack as being 2 dimensional and measuring the face. Splits might have an irregular face, but their shape through the stack is somewhat regular. Splits do have taper, but odds are 50/50 that I put the fat end out so I discount taper also. So all I need to look at is the face. How to measure it? If I pick enough points on a stack and count the number of times I find air vs. wood I'll have a pretty good idea of what the real number is. So I took a piece of garden fence, stapled it to my stack and counted. I did it on 2 different rows. The first sample was 243 points, of which 35 were air, or 14.4% The second sample was 162 points of which 28 were air or 17.3% So I'll go with a cord of wood being 15% air and 85% solid wood. That means a cord of wood contains 108.8 cu feet of wood, bark and all and 19.2 cu feet of air. I did a little more follow up with by examining some of your stacks. Looking at your photos I held a ruler up to the screen, counting on the 1/4" mark the number of times I found air vs. wood and got about the same results, 85% wood, 15% air +-. I did a little more Google research and found that the 80-85 cu feet figure that gets repeated so much that it is true probably came from studies done by the pulpwood industry. Bark doesn't count at the pulp mill, it does for firewood. With some species bark can figure in at 10 percentage points. Mills don't deal with short lengths. One of the studies was looking at 20+' logs so taper will also figure in quite a bit if you are measuring the big ends. Irregularities such as crooked logs or bulges will further skew it.
However there were some short bursts of inspiration. It took a few 'cups' of beer to figure that I could hold a ruler up to peoples photos and double check my results.
And so it shall be decreed that this shall forever more be Known as the Paul bunion Theorem, as noted on this 29th day of the 3rd. month of the year 2014. Gary
It's an interesting topic. If you're dealing in logs, say you bought a semi-load of logs, that will have more wood in a "cord" than if you have a whole tree. Trees have bumps and lumps and lots of odd pieces that open up more air in a stack than logs will. The local guy with the processor who sells 1000+ cords of wood a year is using only logs. But, a freebie scrounger like me will take what he gets. Sometimes that's sweetgum or beech which doesn't split and stack as nicely as white oak. There's a lot of variability in a cord of wood. Drink a few more, Paul bunion. This thread is a worthy thought.
Good job. I've wondered where that 1/3 air number was coming from because it seems high. Nice job of figuring this out. Wonder if we could all take pics of a face cord and get a bigger sample with photos and a grid system. I do think you've probably nailed it, though. 15% air seems more appropriate.
Only way to prove your theory is to build a 4x4x8 box with a lid fill it with wood. then add water & measure the water before any soaks into the wood. I go with the 85 to 90 cubic feet, seems to be a good standard. Not saying you can't stack it tighter, but on average, 85 to 90 is pretty close. Of course it's shrinking as it sets there, so hurry. (or swelling up, if you fill the box with water) you need all perfect 16" splits with perfect square ends so 3 rows equal 4' I cut mine wood to 17", so I can't do the 4 x 4 x 8 box & water test . LOL
After a few more beers and a look at the brick fireplace it made me wonder how it would look if I took out a few bricks. Then my childhood came back to me, I had a sudden urge to play with legos. This stack is 33% air or the 85 cu feet solid cord. I had to use the yellow pieces to hold it together. Without cribbing I don't think anybody can show me a stack of wood that has that much air in it. Made me wonder if you could even stack wood at 33% if you tried. Maybe if you split your wood like planks, the same 33% stacked a bit different. At 25% (which would be 96 cu solid per cord) it tightens up a bit, but still no face on a stack of wood is that open. Back to this. Defiant Brewing Coompany Porter.
As PB has said in his first post, and a few others behind him, water displacement would be the only way to get a true measure of what's solid and what is air. Stacked wood, unless it was some sort of processed wood, will always be odd shaped. Now that FHC has it's own Newton of sorts, we can direct questions like these his way.
Im not sure if you have to much time on your hands or maybe you drink to muchI can honestly say though that I have never considered this and its actually pretty interesting I will follow along here and see how this study goes you may be on to something groundbreaking and I would like to be able to say I was there when it happened.
I guess in all honesty it comes down to who stacks it. dishonest sellers will stack a lot of air. I try to stack mine as tight as possible. I think i'll stay along for the ride its pretty interesting.
Use a scaled down model and test that. Take dowel pins cut them to the appropriate scaled length, split them like you would firewood. Build a small crib to hold the equal of 1/3 cord, stack the pieces in that. Then, stack them in a water tight box, pour the water in there and measure how much it took. You could do this like 10 different times to get an average. Only a suggestion for you to do. This sort of hard core thinking is a spectator sport in my world! Ted
