Board Ft/ Cord Question

[Tyler]

Have looked and can't find anything on this subject.

If a person had a size of a log and the board ft it produces is there a way to calculate the "waste" that is not being accounted for in the board ft measurement.

Reason I ask is that I spoke with a local logger and asked roughly how many board ft can he fit on a semi load. He said 3500(ash) up to 4500(pinn oak). So I'm trying to calculate roughly how many cords could possibly be in the load.

I realize that:
1 board ft = .0833 cubic feet.
A cord is 128 cu/ft

But of the 128cu/ft what percent is "air." I have seen some figures of 80-90 cu/ft is what you are truly getting. I realize it depends how a person splits there wood.

So 4500 x .0833 = 374.85/128=2.93 cord? Sounds low to me.

OR
4500 x .00833= 374.85/85=4.41 cord?

Any insight would be great. Thank you

 

[Ashful]

No direct answer, but some useful numbers:

Most log trucks are quoted to hold 7 to 10 cords, the most frequently quoted single number being approximately 8 cords.

A typical stacked cord of wood contains 85 cu.ft. of wood.

 

[Tyler]

So with those figures it sounds to me like there could be 40-50% waste?

 

[Jags]

So with those figures it sounds to me like there could be 40-50% waste?

I are cunfuddled. Are you looking to take a logging truck full of logs and cut into boards (hence the bdft question)? Or are you looking to make firewood out of it? If firewood - you are looking (as Joful said) at ~8 cord stacked of which 85-90 cuft per cord is actually wood and the rest being airspace.

A cord is 128 cuft INCLUDING the airspace. 85-90 cuft actually being solid wood.

 

[paul bunion]

I are cunfuddled. Are you looking to take a logging truck full of logs and cut into boards (hence the bdft question)? Or are you looking to make firewood out of it? If firewood - you are looking (as Joful said) at ~8 cord stacked of which 85-90 cuft per cord is actually wood and the rest being airspace.

A cord is 128 cuft INCLUDING the airspace. 85-90 cuft actually being solid wood.

Can you back that statement up with fact? Please show us how there is 85/128=66% wood or 33% airspace to a cord of wood. Please don't repeat something that you read on the Internet so it must be true in your justification. No way is a cord of wood 33% air.

 

[Pellet_Pete]

Can you back that statement up with fact? Please show us how there is 85/128=66% wood or 33% airspace to a cord of wood. Please don't repeat something that you read on the Internet so it must be true in your justification. No way is a cord of wood 33% air.

A cord is a cord is a cord, has been for centuries. 4x4x8, 128 cubic feet including air space. Obviously actual volumes of wood will vary by how you stack, which you can be sure has led to millions of "interesting discussions" between firewood sellers & buyers over said centuries. Jags put out the 85 cubic feet, which sounds fine. I was taught to fall back on 80 cubic feet of solid wood per cord as a rule of thumb if you need to combine volumes of board feet & cords into a single unit of cubic feet. 80 might be conservative, but again depends on how you stack - see lots of different stacking styles just on this forum. If you want proof, start with a few logs, scale their volumes, split & stack - I'm sure there are some folks on here that have done it and have numbers to show.

 

[paul bunion]

A cord is a cord is a cord, has been for centuries. 4x4x8, 128 cubic feet including air space. Obviously actual volumes of wood will vary by how you stack, which you can be sure has led to millions of "interesting discussions" between firewood sellers & buyers over said centuries. Jags put out the 85 cubic feet, which sounds fine. I was taught to fall back on 80 cubic feet of solid wood per cord as a rule of thumb if you need to combine volumes of board feet & cords into a single unit of cubic feet. 80 might be conservative, but again depends on how you stack - see lots of different stacking styles just on this forum. If you want proof, start with a few logs, scale their volumes, split & stack - I'm sure there are some folks on here that have done it and have numbers to show.

I have something to show, and that is why I called BS. Here's a bit of proof as to how far off the 1/3 air estimate is. And your fallback at 80/128 is even worse in my opinion.

Start out with a stack of wood.

1. Cut the wood to exactly 16". Yes neither you nor I can do that but some will be long, some will be short, some will be at an angle because wood will never be be square. But in the end they will average out to 16" and it will average out in the end.
   
2. Stack it up, 4 feet high and 24 feet long.

Correct me if I am wrong but that it a cord, exactly as you said it has been for a centuries. Agree with me? Then continue.

Ok, then look at this, a stack of Legos. For every 4 nubs of plastic there are two nubs of air. 4 nubs of plastic and 2 nubs of air come out to 33% air, right?. The same 33% air that Jags and others have told us is what a cord of wood stacks up to. (And you are telling us it is even more than 33% air). Look at your stacks of wood and tell me that it looks like this. No way can you put this much air into a stack of wood if you tried. Never.



Yes, I am using perfectly square pieces of plastic to illustrate my point and it isn't a stack of wood. Wood is crooked and whatever. But in no way does the face of a stack of wood have that much open area. And since we agreed that we are pretty good at cutting wood to a uniform length there is only minimal error on the depth of the stack. Error in depth doesn't come into play so it is a two dimensional problem.

My estimations are that a cord of wood, well stacked and cut consistently will run about 105-110cu feet solid per cord. Prove me wrong and I will gladly admit that I am incorrect.

 

[Hogwildz]

Ya lost me with the Legos., nubs...
I'll wait for the movie to come out.

 

[Pellet_Pete]

I love the lego demonstration - I'll have to remember that when my 7-year-old starts learning percentages in school.

I'm not setting out to prove you wrong, just backing up the numbers that the wood products industry uses, which are probably on the conservative side for dealing with large volumes in an industrial context vs. small volumes stacked carefully in a minimal footprint in our backyards. Found this excellent little bulletin from UMaine, which has some other great firewood info too.

(broken link removed to http://forest.umaine.edu/files/2009/10/Tree-Volume.pdf)

 

[Tyler]

I are cunfuddled. Are you looking to take a logging truck full of logs and cut into boards (hence the bdft question)? Or are you looking to make firewood out of it? If firewood - you are looking (as Joful said) at ~8 cord stacked of which 85-90 cuft per cord is actually wood and the rest being airspace..

I'm just wanting to figure an amount of cord wood from the amount of board ft the logger told me. Therefore in the future if he had a load and he knows the rough board footage I can figure about how many cord of wood is in the load.


I'm figuring that country wide not every log truck load is the same. Longer or shorter trailer, shorter or taller sides, etc

 

[Tyler]

I love the lego demonstration - I'll have to remember that when my 7-year-old starts learning percentages in school.

I'm not setting out to prove you wrong, just backing up the numbers that the wood products industry uses, which are probably on the conservative side for dealing with large volumes in an industrial context vs. small volumes stacked carefully in a minimal footprint in our backyards. Found this excellent little bulletin from UMaine, which has some other great firewood info too.

(broken link removed to http://forest.umaine.edu/files/2009/10/Tree-Volume.pdf)

That is a handy sheet.! Thanks for sharing.!!

 

[Tyler]

My estimations are that a cord of wood, well stacked and cut consistently will run about 105-110cu feet solid per cord. Prove me wrong and I will gladly admit that I am incorrect.

I agree the 80-90 seems a little far off. But it does seem to be a standard thought.

Just another thought. If you look at the Lego pic there are 19 "nubs" across and 8 rows down for a total of 152 "nub spaces" then there are 48 of the 152 that are empty. So 48/152 is 31.5% air. Therefore 68% of a 128 cu ft is 87.7.

Now if you tighten the nub spacing to 1 instead of 2 and still keep the overall dimensions of 19x8 the same. Then you have 24 out of 152 empty. So 24/152 is 15.7% air. Therefore 84.3% of 128cu ft is 108.8.

Just a way to look at it...lol.

 

[JustWood]

Don't overthinx it.
Have him text you a picture of the truck.
Go look at the truck.
Ask him for some customer references . (phone #'s)
The bd/ft capacity vs wood capacity way of looking at it is wonky.
You could fit 4000 bd/ft of lumber on a 20 ft fifth wheel trailer easily. A tractor trailer typically hauls 7-11K bd ft

 

[Tyler]

Attached is a picture of a load.

According to the link above it says that 1000 board ft is between 1.8-2.2 cord. So if you use 2 cord for 1000 brd ft. And he is saying 3500-4500 board ft per load that makes since of the 8 cord per load stated above.

 

[Hogwildz]

Looks like a log truck/trailer semi combo, goof for about 12 cords+/- is my guess.
Why not just measure the loaded rig and do the math, to hell with board feet.
He has it loaded pretty tight, so maybe a little more.

 

[Ash]

No direct answer, but some useful numbers:

Most log trucks are quoted to hold 7 to 10 cords, the most frequently quoted single number being approximately 8 cords.

A typical stacked cord of wood contains 85 cu.ft. of wood.

I'm not sure what log trucks hold out by you but a typical tri-axle load here is approximately 12 cords cut at 8ft lengths

 

[weatherguy]

I'm not sure what log trucks hold out by you but a typical tri-axle load here is approximately 12 cords cut at 8ft lengths

Around here they're also advertised at 8 cords, never bought one or saw one up close so can't ascertain the validity.

 

[Ncountry]

I averaged 8-12 cord from most of the tt loads I have bought . Most were closer to 10+-

 

[nrford]

Attached is a picture of a load.

According to the link above it says that 1000 board ft is between 1.8-2.2 cord. So if you use 2 cord for 1000 brd ft. And he is saying 3500-4500 board ft per load that makes since of the 8 cord per load stated above.

Ding,ding,ding winner! winner! chicken dinner!

 

[Bret Chase]

Have looked and can't find anything on this subject.

If a person had a size of a log and the board ft it produces is there a way to calculate the "waste" that is not being accounted for in the board ft measurement.

<snip>
Any insight would be great. Thank you

I guess I am as confused as everyone else... there is no "real" way to calculate waste, as the waste is determined by the sawyer... Whether it's your neighbor half in the bag running his Wood Miser or one of Irving's laser guided/sorted industrial scale saw mills.. or if it's plain, quarter or rift sawn...

 

[nrford]

I guess I am as confused as everyone else... there is no "real" way to calculate waste, as the waste is determined by the sawyer... Whether it's your neighbor half in the bag running his Wood Miser or one of Irving's laser guided/sorted industrial scale saw mills.. or if it's plain, quarter or rift sawn...

Also which log scale is used; Doyle, Scribner, Scribner Decimal C, International, etc.....

 

[Ashful]

Can you back that statement up with fact? Please show us how there is 85/128=66% wood or 33% airspace to a cord of wood. Please don't repeat something that you read on the Internet so it must be true in your justification. No way is a cord of wood 33% air.

There are countless sources to back up that number, if you'd spend half as much time just reading as arguing and typing. Here's the first two that pop up in a three-second Google search:

http://extension.oregonstate.edu/lincoln/sites/default/files/home_heating_fuels_ec1628-e.pdf

http://extension.missouri.edu/p/G5450

 

[Poindexter]

The way I heard it from a forester at a university sponsored symposium was a "cord" of wood provided by a competitive retailer will have about 75cf of wood in the 128cf box. Engineering tables are based on 80-85cf of wood per cord, but these are folks that measure the moisture content, weigh an empty truck, fill the truck with a front end loader and then weight the filled dump truck.

When a forester stacks a cord there are no crisscross pieces, the stack looks like this (first pic), and should have about 95cf of wood in each 128cf box. Second pic is a log truck delivery I got last month. I have it all bucked now and am looking for 6 or maybe 7 cords at 95cf each once it's split- but i am going to split pretty small because I need it all to season in one summer. The smaller you split wood, the more space it takes up when you stack it.

I think the semi load Tyler pictured above should split out to 8-10 cords easy.

PS: When I got done bucking all those logs into rounds I had two _heaping_ loads of saw dust to take to the dump in my short bed/ extended cab Ford Ranger.

 

[paul bunion]

There are countless sources to back up that number, if you'd spend half as much time just reading as arguing and typing. Here's the first two that pop up in a three-second Google search:

http://extension.oregonstate.edu/lincoln/sites/default/files/home_heating_fuels_ec1628-e.pdf

http://extension.missouri.edu/p/G5450

I've looked through the countless sources and I am unable to fine a single one that can back up the 'fact', zero. They all regurgitate the fact like it is a fact and offer me no way to understand how they arrived at their conclusion. And you also seem to be unable to find one that explains how they determined this seemingly true 85 cu foot number. The UMO document has no foot notes for me to follow, nor does your Oregon one. Sorry, they might be a place to start researching facts, but as a definitive source they are useless.

So neither of your references offer a splinter of information to back up their 'facts'. Your Missouri reference even says "Actual volume of solid wood in a cord varies from 65 cubic feet for small, crooked sticks, increasing with the size and straightness of the sticks up to about 90 cubic feet. Average for the Midwest region is about 80 cubic feet". So again we must look at the information offered, and then ourselves decide if they are plausible, or at least if the they are worth the bits that Google used to index them. Isn't that one of the basic things that about the Internet?

So for starters lets pull out our BS meter and look at the low side of the Missouri document. 65/128 is 50.08. That might describe a matted down brush pile in my observations. Can you show me a stack of firewood that is close to 1/2 air? I don't think this one is worth pursuing. Do you?

Lets think a little more about how a stack of wood would need to appear if it was 85 cu feet of solid wood. It would need to be 1/3 air. Looking at that a bit differently, for every piece of wood there would need to 1/2 of its size in airspace around it. Additionally every piece of wood is next to another piece is next to another is next to another and so on and so forth. So if you look at just one split in a pile, just one that is, you will see around it the 1/2 area of airspace that needs to be for that piece and additionally you will need to see the airspace that every adjacent piece needs. So with the airspace belonging to the adjacent splits it kind of happens that around each piece you will need to see a lot more air than1/2 of each piece. It starts looking like the Lego stack, lots of air around every piece. Wonder why that is? I still don't think you can show me or any other educated reader a stack built like that.

I'll show you another example so maybe you can understand it better. I think we have done this before but without visual aids. Lets look at rounds, the natural state of firewood. Imagine them cut and stacked to look kind of like checkers on every space of a checker board. Kind of like this but it really should be square and tight.



For starters I think you will agree that it is also pretty much of an impossible arrangement for a stack of wood. Can't get wood to stack like that, each piece will settle into the adjacent pieces below. But we will continue so we can calculate the airspace in this hypothetical stack.

Each checker is one unit in diameter. Doesn't matter if it is an inch, a millimeter, a foot or a mile. The area of each checker is .785 of a unit squared. Each checker happens to sit in a square. The area of that square is one square unit. So the ratio off the area of a circle within a square is .785.

So here we have determined that if we stack up rounds (in an impossible fashion) the resultant stack will be .785 wood and 21.5% air. If we want our stack to reach .66% wood and 33% air we will need to add space between every round. Best I can figure to obtain that they can't even be touching each other. For that matter the bottom row might not be on the ground either. Was there a wood stove on Skylab? (imagine getting clocked in the head by that wood stove back on the day Skylab fell from the sky.) Is there one on the ISS? A place with no gravity is about the only place that I think you could make a stack of wood that looks like that. Except just maybe here on earth you could use some rounds with untrimmed branches. Nubs like 1" or so. (Damn I used that word before.) They'll pin up each round apart from the adjacent ones. It might be difficult but with some effort I think it could be done. I personally don't feel like picking up a bunch of Christmas tree carcases to test that theory. But I encourage anybody who is interested to try and the time to do so is coming up.

Yes, my above argument uses perfect shapes, so it isn't 78.5% if we used real rounds on a stacked square. Also bark plating/ridges will add some air. If Beech close to nothing, Black Locust something more. But stacking rounds up square is impossible. So it is plus/minus on those corrections.

So lets again go back to the purported fact that a cord of wood is going to have 33% airspace. I have an easy way to test that. Really easy. Its this statistical analysis crap that I learned back in college a long time ago, About all I remember about that was that if you took enough samples from an unbiased sample base you got very accurate results. The other thing I remember was that 'enough' didn't need to be very many. Once you got into the hundreds you were close to being perfectly accurate if you had an unbiased sample. (I admit here I'm telling you how statistical analysis works without backing it up, it might be bunk.)

So back to figuring your stack's air. Next time you are out measuring your freshly stacked cord of wood leave the tape measure suspended across the face of your stack. Count on even increments if there is wood or open air beneath. Like every inch. Do is diagonal, top to bottom and side to side. Do it a lot of times. Even easier is that you can look at other guys pictures of wood piles on your computer screen and hold a rule to them and start counting. You don't even need to leave your home to get a nationwide or even worldwide sample. Figure out how many times you see air vs. wood/bark and calculate how much air there is.

I think I have shown several ways how the 85/128 per cord is not correct. I'd still like to be shown otherwise but every source I look at doesn't tell me how they figured it out. Every one regurgitates it as fact but they have nothing behind it. I'm stuck with the ways I've tried to figure it out and none of them come close to 85/128. No where near.

I once believed that the 85/128 was true cause I read it on the Internet. But something clued me into the fact that it wasn't possible which made me figure it out what it was for myself. And with all respect, that is why I think you are wrong.

 

[Poindexter]

Paul, if you really want to know, measure your moisture content, weigh and re-stack a face cord of 16" splits.

1/.3 of 128 cf is 42 2/3, 1/3 of 85 is 28 1/3. I think you are going to have to work pretty hard to stack 28.33 cf of wood by weight of known density into a 42.67cf box.