Meauring cords of wood in a log?

[sawyerkirk]

I've been buying firewood logs from a guy and so far, it has been small stuff that  I split right there and pay him by the cord, but now I've gotten to some bigger trees that I want as logs for lumber, So, I am trying to figure out how many cords of firewood would be in these logs were I to split them into firewood. Any Idea where I might find a conversion chart? Thanbks, Kirk.

[rcanderson1968]

I'm sure there are tables out there, but you could also try this:  4'x4'x8'=128 cubic feet per cord, but only about 80 to 90 cubic feet is solid wood.  So for estimating bigger logs in cords, I would try to get a measurement of cubic volume for each log and then add them up until you get to 80 to 90 cubic feet.

[Ron Wenrich]

Go to the toolbox and open up the log weight calculator.  It will give you a cubic foot volume for each log.  Logs are measured at mid point and given a length.  Using 90 cu ft per cord is probably a good estimate. 

Can't find the toolbox?  Its under forum extras at the top bar or its the red tool box at the lower left hand corner under the advertisers.

Or you can go right here:  https://forestryforum.com/calcs/log_weight.htm   Find the toolbox or the extras and you'll find all kinds of good info.

[SwampDonkey]

It varies by length of wood. We use 100 ft³ solid wood for 4', 95 ft³  for 8' hardwood. Random length stuff is 89 ft³, tree length is around 82 ft³. I'm going by what our marketing boards and mills use up here.

[captain_crunch]

Don't hold me to it but I was told about 750 bf(scribner) per cord

[bill m]

500 bd ft. international 1/4 scale = 1 cord

[rcanderson1968]

Log scales estimate volume in board feet not in cubic feet.  That's important because depending on log size there may be more (or less) cubic feet in 500 board feet. 

For example, a 9" log (small end diameter) that's 8' long scales 20 board feet (international ¼ scale).  So it would take 25 of those logs to equal 500 board feet.  The cubic volume of a  9" x 8' log is about 3.9 cubic feet (depends on species/taper).  So the 25 logs that measured 500 board feet would contain 96 cubic feet of wood (25 x 3.9). 

On the other hand, a 19" log (small end diameter) that's 8' long scales 125 board feet (international ¼ scale).  So it would take 4 of those logs to equal 500 board feet.  The cubic volume of a 19" x 8' log is about 16.4 cubic feet.  So the 4 logs that measured 500 board feet would equal almost 66 cubic feet of wood (16.4 x 4).

That means a person buying 500 board feet of logs could actually get 96 cubic feet of wood fiber (if they were all 9" x 8'), or get only 66 cubic feet of fiber if they were all 19" x 8'.  In other words, 50% more wood fiber in the small logs.

[SwampDonkey]

That 8 foot 19" top end log would be awfully handy to 24 ft³ , approaching 25, if it were sugar maple at least. That's a large chunk of wood. Just the last foot of the log alone is:

19² x 3.14  = 1.97 ft³ closer to 2 ft³ with taper
4 x 144

The butt end, first foot, would be handy to:

28² x 3.14  = 4.27 ft³ closer to 4 ft³ with taper
4 x 144

,which averages 3 ft³ per foot of length

[rcanderson1968]

SD,

The formula for cubic volume is pi x radius squared x height.  Looks like you were using diameter squared?

You bring up a good point though.  I'm not real familiar with the taper in hardwood logs.  I was figuring a little over 1/10th inch per lineal foot for both sizes of logs.  I was not thinking of a butt log that would have a lot of butt swell/more taper.

If the taper in the larger logs was considerably more than what I figured and the taper in the smaller logs stayed the same,  it would make the cubic volume of the larger logs go up.  That would make the cubic volume difference I pointed out less dramatic.

[SwampDonkey]

rcAnderson1968

It's also pi x diameter² divided by 4

diameter² divided by 4 is the same as radius²

And we are dealing with feet, so we have to divide inches² by 12² (is 144) to get ft²

[SwampDonkey]

I know from measuring many samples of trees and keeping a tally of diameter at stump height and breast height per tree that a hardwood/aspen up here with a 25 in butt will average out to 20 in at DBH (4.5 feet). When you graph the numbers it's an R² of almost 1, which indicated a very good fit. I forget the slope, I do have the table of values that I can get the formula computed if I want to. But that's only for my area. I think you'll find a good fit in your area to, what ever the slope turns out to be. Anyway, I did mine by grouping good sites and then not so good sites, got two different slopes but still good fit in each. Did it separate for ceder, then for hemlock, then spruce/fir/pine. It's an interesting exercise. What made me do it was for trespass instances and had to measure in neighboring stands to get a good estimate of what was stole from the same site type. I just kept pooling the data for similar  sites, increasing the sample size so to speak. After awhile it became pointless to add more samples. I went up to a 20" breast diameter as not much around here, if any, above that when I was sampling. ;)

[rcanderson1968]

I don't doubt that butt logs taper at the rates indicated by your measurements.  However, if the whole tree tapered at the same rate, the stem would have a 5" diameter at 16' in height. 

I have a book called "The Measurement of Roundwood" that gives some background on the development of the International 1/4 scale.  According to that book, the scale is widely used in eastern North America.  It was published in 1917 by Judson F. Clark who was researching lumber recovery while working for the Province of Ontario.  The scale assumes 1/4" saw kerf, allows for 6.25% shrinkage, and assumes a taper rate of 0.125" per lineal foot. 

Given that information, I think the point I was making in my other post holds true.  If the exchange of wood is based on a measurement of 500 BF as measured by the International 1/4 scale.  A person could get significantly more cubic volume of wood fiber when buying 500 BF smaller diameter logs versus buying 500 BF of larger diameter logs.

[SwampDonkey]

I don't doubt that butt logs taper at the rates indicated by your measurements.  However, if the whole tree tapered at the same rate, the stem would have a 5" diameter at 16' in height.

Don't be confused by my post back there a couple when I stated it averaged 3 ft³ of volume per foot. By no means am I suggesting the log tapers the same throughout the log. But in my measurements, and you can try it yourself, I found the first 4.5 feet very consistent in taper. It's a pretty short length compared to 16'. On a 40" but end it's harder to detect a difference compared to a 6" butt end up to breast height. Now if we were in the jungle with Jim, there is some whicked buttressing. :D Up here mills require severely flared but to be trimmed off. It's worst when wood is cut by processor, some inexperienced operators go into the root collar. I've seen guys on the yard bucking all that flare off. I could imagine what the guy was saying under his breath. :D

You can actually estimate that top diameter (outside bark) on a standing tree with an angle gauge, Suunto and tape. Stand at a distance that shows 100 % in your Suunto on the level. Tan(45 deg) =1, distance from tree is 16 feet minus distance from ground up to eye level (@ 0 degrees-level) plus 1 foot for stump height. Adjust string length of gauge to fit the tree image on the inside edges of the gauge site, find new gauge constant (gauge width divide gauge string length) to get diameter (which is min diameter). Your at the limiting distance. Everything is kind of backwards to using the angle gauge the regular way as a sampling tool at DBH. There are electronic gadgets to do this with a click of a button, but that's cheating. :D

[Ron Wenrich]

Cubic foot volume formulas for logs:

Huber's   Vol=0.005454*(midpoint dia)^2 * length

Smalian's   Vol=0.002727*((small end dia)^2+(lg end dia)^2)) * length

Newton's  Vol=0.000909*((sm end dia)^2+(4*midpt dia)^2+(lg end dia)^2) * length

The calculator uses Huber's since its a lot easier to measure.  Diameters are inside bark.  

[SwampDonkey]

Yup as Ron says, I was just lazy and didn't want to use the standard formulas because we were dealing with just a top diameter in the 19" example and no other details except length. However, I'm sure your not going to loose volume with increased log size in the comparison your trying to make with board footage. Not possible. Your gaining waste or loosing footage at the but end with log length and tapering small end, but not ft³ volume. Assuming you want lumber to full length of the log. Your gaining ft³ from the bottom end of the log, plus there is slab volume under the bark. It would be great if we could take a 19" log and stretch it from 8' to 16' and not loose top diameter. ;)

[arojay]

I had an issue with a buyer a couple of years ago where we couldn't agree on the volume of wood on a load.  We were hauling with a super B.  Anyway I hired a government certified scaler and she stick scaled 5 loads.  I was pleasantly surprised to find out that we were averaging even more than I thought.  Anyway the logs were scaled to solid wood volume.  To convert to stacked cord multiply by .625.

[SwampDonkey]

What units are you converting from? What's the starting length and how long is the target firewood? The conversion factor is variable and not a firm number across the board.

solid m³ of 8 ft hardwood is 0.484 cords and 4 ft is around 0.49 cords. See what I'm getting at? And it's different numbers for softwood. I don't have numbers here for cutting to 16" firewood, but maybe that's what your using Arojay.

But, if you have a stacked m³ and want cords it's 0.276   :D :D

[arojay]

The scaler used 'Yukon Scale'.  I think it was developed by DIAND when the federal government was responsible for forest management here.  It is still used.  Conversion is supposed to be to 4x4x8 stacked cord.  We tested it, practically but not scientifically, by bucking and stacking some of the scaled logs that should have added up and it pretty much works out.  This was beetle killed White Spruce, bucked to 33 feet for trucking.  I realize there are different factors, my point is that hiring a trusted scaler that both parties agree on is good business.

[arojay]

Conversion is from what they call a solid wood cord to a stacked cord.  We have to report harvest in the form of a solid wood cord.  As you know firewood is generally sold as a stacked cord.  The metric conversion for solid volumes is 2.265 m3 per cord.

[SwampDonkey]

We use 2.4  for 4' softwood and 2.265 for 8'. That's the only way you can relate, is to know what the numbers are based on. It's like a moving target when dimensions change. ;D From your statement previous I don't know if it's 8' or 4' bolts. Looks to me like your saying 4', but just guessing. Now I think it's 8', well guessing again. ;)

[arojay]

The government's documentation does not specify piece size for stacked volume.  Simply a stack yielding 128 cubic feet.  I guess that leaves it to your imagination.  I bucked my 'test' cords to 16" firewood length as that is the most common used here and it was the most common size sold by my buyer, but the documentation from the gov. could be in any dimension I guess.  I don't make the rules so I say again, an impartial scaling, agreed to by the buyer and seller worked for us.  I think that variations in "what makes a cord" are probably as old as the selling of wood, as indicated by the variety of scales that can be used in different jurisdictions.

[captain_crunch]

Guys this is driveing me NUTS trying to figure this out but this is what I come up with by the Columbia River scale book(what is used in Western Oregon) a 4' dia log has just over a 100 bf per lin ft so a 4'X8' log just over 800 ft. I am thinking that would split out to over a 4X4X8 stack.  Does this make any sence to you ????
Brian

[SwampDonkey]

Yes, but more than just a bit more, because of the butt diameter and taper. Are you asking about split and piled wood as well? If so, significantly more in stacked volume because your adding air space to split wood and comparing to a solid mass, a log. Well, less saw kerf and slabs. :D

I can't think of pulp and firewood in board feet terms, only cords, tons, and m³. Makes no sense. Board feet should be left to veneer and saw logs and lumber. :D I know I know, we're talking conversions. Trouble is guys up this way think of cords and down your way think footage. ;) Hand a logger a board foot scale, next question is how many cords? ;)

[captain_crunch]

Swmp Donc
Guess this is why Gov can get to us like they do Only thing done in cords out here is firewood. Logs are sold by scale or tonage so guess we are in different worlds ;D ;D But it is interesting to learn just how different things can be from west to east
Brian

[sawyerkirk]

anks for all the replies, I think I can get pretty close now. now if it'll just dry up so I can get to it.

[ickirby]

I've been buying firewood logs from a guy and so far, it has been small stuff that  I split right there and pay him by the cord, but now I've gotten to some bigger trees that I want as logs for lumber, So, I am trying to figure out how many cords of firewood would be in these logs were I to split them into firewood. Any Idea where I might find a conversion chart? Thanbks, Kirk.

Not to addd more confusion to the discussion but if you are looking for this conversion so you can figure out how much to pay the person for the sawlogs based on their value as cut and split firewood then thats ok.

However if you are thinking of making these larger logs into fire wood and trying to figure out if they are more profitable for you as firewood or sawlogs then make sure to take into consideration the added expenst (time/effort) required to process larger logs into firewood.  Even if you have a firewood processor most of them will only handle up to a 14" diameter log and if you are using a splitter or heaven forbid an axe the added effort might make firewood less profitable.

I think the waters are muddied enough with conversion factors on this thread already, so I'll leave mine out but know that in Manitoba we would agree (closely) with both arojay and SwampDonkey.