Ratio of solid to airspace in stacked firewood cord calculation?

[Snap]

Calculating the volume of wood in a tree trunk is a straightforward undertaking, but when defining a cord of stacked firewood is there a standard ratio of solid to air space used in the calculation?
I am trying to guestimate the number of stacked cords I might end up with based on the trunk dimensions that I have on the ground but the airspace variable is the unknown. All of the references I've found seem to be based on standing trees, limbs and all and don't seem to define a trunk length.

 

[ChoppyChoppy]

In the area of 25-30% air, so around 90 cu ft of wood in a cord.

 

[LondonNeil]

if the wood is straight and smooth maybe, but if its a bit irregular i think the air is more like 30-35%

 

[JeffHK454]

Back in the day when my dad and I sold firewood he gave every customer of his a printed copy of the definition of a “stacked cord” from the Dept. of weights and measures...75% wood - 25% air. This ratio works in conjunction with the 128 cu.ft of space that a stacked cord should displace.

I sold 4”x6”x16” Oak skid runners in “cords”and it took some convincing that people where getting the same amount of wood in a smaller space when the ratio was 98% wood and 2% air...they where sure I was screwing them.

 

[Snap]

Thanks all. I think I can estimate how much room I need from the answers of 70% to 75% solid as stacked.
Unfortunately the tree trunks are scattered over an acre so it's going to take some time getting it split and stacked in one place.
Job seems too big for an old die hard with a splitting maul, atleast at my age now. On to find a splitter.

 

[svk]

Oh man. Whitespider had a great post on this a few years back. Basically the smaller the splits, the more airspace. Wish I remembered the name of the thread to reference.

 

[Snap]

Oh man. Whitespider had a great post on this a few years back. Basically the smaller the splits, the more airspace. Wish I remembered the name of the thread to reference.

That's odd. In soil, the smaller the grains the less the airspace and more dense the material.

 

[Ted Jenkins]

California Dept of Weights and Measures states 30%. I am not sure what it means any more because what I went through a number of years ago does not seem to be relevant today. Most folks deliberately cut sloppy so more space is evident. Thanks

 

[svk]

That's odd. In soil, the smaller the grains the less the airspace and more dense the material.

Understandable as soil can be compacted.

I believe the only exception to the rule is when cutting from tree length to bolts. Then you gain wood as it eliminates lost space between full length logs.

 

[Wood Doctor]

Oh man. Whitespider had a great post on this a few years back. Basically the smaller the splits, the more airspace. Wish I remembered the name of the thread to reference.

That is correct. The more splits that you have the more air that will be present and the less mass and weight that your truck will be hauling.

One time I packed my truck with big dry rounds already cut to length that I split immediately and set aside as I unloaded. Then I tried to load the splits back into the truck. At least 20% of them could not be packed right back into the truck along with the scree that the log splitter generated. I saved those splits for my next delivery and saved the scree for kindling.

I showed my wife a simulation using raw carrots and a mason jar. We packed the jar tight with large carrots, unpacked them, and then sliced them up with a food processor. It was impossible for her to get all the sliced carrots back into the jar.

 

[LondonNeil]

Is that the thread where someone got load of dowels, packed a box to full, then re packed with smaller diameter dowels and showed less wood fitted in the box? that's the opposite of my experience when i pile bucked rounds up at the end of my plle, and then go at the splitting and stacking, the stack of splits is always considerably shorter/denser. there are so many factors though...are all the rounds the same size or is there variation? do you stack carefully, using small ones to fill the gpas? are they straight? are they all the same length or does variation cause more gaps? however, if we take a regular shape like the dowel, a triangle (rough approximation for a split) will tessellate much more densely than circles. I guess what I'm saying is, it varies loads and your experience may not match my own or anyone else's

 

[Wood Doctor]

Is that the thread where someone got load of dowels, packed a box to full, then re packed with smaller diameter dowels and showed less wood fitted in the box? that's the opposite of my experience when i pile bucked rounds up at the end of my plle, and then go at the splitting and stacking, the stack of splits is always considerably shorter/denser. there are so many factors though...are all the rounds the same size or is there variation? do you stack carefully, using small ones to fill the gpas? are they straight? are they all the same length or does variation cause more gaps? however, if we take a regular shape like the dowel, a triangle (rough approximation for a split) will tessellate much more densely than circles. I guess what I'm saying is, it varies loads and your experience may not match my own or anyone else's

A solid block of wood takes up the minimal volume. Take it from there.

 

[stratton]

Oh man. Whitespider had a great post on this a few years back. Basically the smaller the splits, the more airspace. Wish I remembered the name of the thread to reference.

SVK, Where is that Mr Spidey. He is the best. I loved his old post on the efficiency of his his older hot air furnace compared to the new era models. Spidey Spider come out where ever you are.!!!!

 

[LondonNeil]

Yes wood doctor, but place that next to another solid block and what determines the ratio of wood to gaps? For every shape it's the shape itself, not the size that determined the ratio.

 

[svk]

SVK, Where is that Mr Spidey. He is the best. I loved his old post on the efficiency of his his older hot air furnace compared to the new era models. Spidey Spider come out where ever you are.!!!!

He’s around but unfortunately for us chose to move operations into the political forum.

 

[LondonNeil]

Didn't spidey give up burning wood after a house move? Can't talk **** with authority when just stood on the sidelines.... Then again!

 

[svk]

Didn't spidey give up burning wood after a house move? Can't talk **** with authority when just stood on the sidelines.... Then again!

I didn’t know he moved for sure?

 

[Sandhill Crane]

If you picture 1/3 cord, 4' high x 8' long x 16", filled with eight round 2' dia. rounds. Lots of air space.
Now picture 1/3 cord, filled with 32 round 12" dia. rounds. Lots of air space.
They are equal percentages of air to wood volume.
I did a real world test a few years ago, since buried in another thread of a forgotten name.
I filled two 1/3 cord racks as a cradle for 8' logs. 8' long x 8' wide x 4' high. Two cord of logs.
Cut into rounds and stacked in racks I got 1 1/2 cord or something close to that, a bit more if I remember right.
Split into stove wood size I gained volume going from rounds to splits, but not all that much. 1 2/3 cord approx.
Again, this is all from memory, but the gain in minimal from rounds to splits, maybe a sixth of a cord gain in two cord volume test. The loss from logs to rounds is far more, and logs to splits was a loss of approx. 1/3 cord.
This also check consistently with the twenty cord loads of logs I've been buying for six or more years now, approx. twenty loads.
I get about fifteen to sixteen cord of good wood, and a cord plus of junk wood (punky, hollow, feather weight airy crap, and good burning short cut-offs that don't stack)
If anyone knows the old thread I'd love to see it again, as I spend a bit of time playing with it. Curly Cherry did the dowels on the work bench thread years before that, and I always questioned if it translated to real world results.
Some university project broke stacked firewood volume down into three categories with percentages of wood, bark and air.
Again, going from memory, bark was approaching ten percent volume in a cord of stacked wood. That of course would be heavily dependent on species and size of rounds, and seems it would also factor in figuring charting the weights of a cord. Maybe the difference in bark for limb wood and trunk wood cancels out.
In the end, who cares.

 

[svk]

If you picture 1/3 cord, 4' high x 8' long x 16", filled with eight round 2' dia. rounds. Lots of air space.
Now picture 1/3 cord, filled with 32 round 12" dia. rounds. Lots of air space.
They are equal percentages of air to wood volume.
I did a real world test a few years ago, since buried in another thread of a forgotten name.
I filled two 1/3 cord racks as a cradle for 8' logs. 8' long x 8' wide x 4' high. Two cord of logs.
Cut into rounds and stacked in racks I got 1 1/2 cord or something close to that, a bit more if I remember right.
Split into stove wood size I gained volume going from rounds to splits, but not all that much. 1 2/3 cord approx.
Again, this is all from memory, but the gain in minimal from rounds to splits, maybe a sixth of a cord gain in two cord volume test. The loss from logs to rounds is far more, and logs to splits was a loss of approx. 1/3 cord.
This also check consistently with the twenty cord loads of logs I've been buying for six or more years now, approx. twenty loads.
I get about fifteen to sixteen cord of good wood, and a cord plus of junk wood (punky, hollow, feather weight airy crap, and good burning short cut-offs that don't stack)
If anyone knows the old thread I'd love to see it again, as I spend a bit of time playing with it. Curly Cherry did the dowels on the work bench thread years before that, and I always questioned if it translated to real world results.
Some university project broke stacked firewood volume down into three categories with percentages of wood, bark and air.
Again, going from memory, bark was approaching ten percent volume in a cord of stacked wood. That of course would be heavily dependent on species and size of rounds, and seems it would also factor in figuring charting the weights of a cord. Maybe the difference in bark for limb wood and trunk wood cancels out.
In the end, who cares.

Since you did such a nice write up on this I will try to find the old thread.

 

[Snap]

Understandable as soil can be compacted.

No, I was writing about uncompacted material. Think of 2" stone vs 1/2" stone. The small stuff naturally falls in close whereas a pile of the big stuff is full of voids.