What is it???, and how is it figured?
It is called a "cunit" and it is equal to 100 cubic feet of volume. Different woods have different weight per cubic foot volume. For instance, for southern pine, the conversion of a cunit to tons is about 3.35 tons of wood per cunit. Spruce, fir, aspen, etc. would be less tons/cunit. Oak and hickory would have more tons/cunit. Back when most wood was scaled, it was a popular unit of measure. Today, most wood is actually weighted not scaled, but folks still want a way to convert that weight back to volume. I guess whether you weigh or scale varies by which part of the continent you are on or, for that matter, which continent you are on as well.
Sorry for the delayed reaction. As already explained, a CCF (also called a cunit) is a unit of 100 ft3. To determine the content of a log via the USFS rules, the formula is: (small-end diameter in inches squared + large-end diameter in inches squared) x length x 0.002727 = cubic feet of the log (or stem in a standing tree). If the log is a butt-cut, measure the large end diameter inside bark 4.0' in from the large-end. diameters are measured via two measurements at each end of the log: narrow and at right angles; round each measurement to the nearest inch and when averaging the two measurement round down, e.g., if the small-end diameter measurements are 12.6 (round to 13) and 12.4 (round to 12) the average small-end is 12.5, which rounds down to 12. Lengths are measured in nominal lengths without trim (a 16'6" log is recorded as 16'). Many agencies (USFS) and larger companies in the US use CCF rather than board feet to track log volumes; Simpson, Pope and Talbot, Weyerheueser, Plum Creek, etc. and virtually all of the Canadian agencies and companies use the Metric variation - m3 (there are 2.83 m3 to a CCF). It does a better job of predicting product recovery, including lumber; and thus is better for determining value. In the US, cubic is measured via the USFS National Cubic Rules and the Northwest Log Advisory Group rules. In Canada BC, Alberta, Yukon, Manitoba, Ontario, Quebec, and New Brunswick have their own provincial methods. All of the above scaling handbooks can be downloaded from the internet.
What is the conversion to board feet. I can usually guestimate, but I just got some info on a sale today for 19000ccf. If I guess on this I could be well over or under in terms of MBF. :o What is the formula? :)
Think about 1 cubic foot of solid wood. That is a block of wood that is 12" tall by 12" inches wide by 12" deep. If you sawed if with no saw kerf, then that block would yield 12 slices each that would be 12" wide by 12" long by 1" thick. That would be 12 board feet per cubic foot. However, in the real world, there is saw kerf. Assume that the saw kerf is 3/16" as on a band mill. 3/16" is .19" (divide 3 by 16). Then, there would be about 20% saw kerf (rounded). So, that is 80% solid wood sawn and 20% sawdust. 80% lumber in a block of wood with 12 board feet would yield 9.6 board feet after allowing for kerf. However, logs are not square. They are round. They are also not perfect cylinders. So, there is additional waste in squaring a round log. To make a long story short, the very best commercial mills can recover about 7 to 8 green board feet per cubic foot of solid wood in log form. That is called the green lumber recovery factor or LRF. Because there is more loss in drying green lumber to dry lumber from shrinkage and trim waste, the number goes down further for a dry bd-ft. That is a key measurement for commercial mills, one that they measure religiously. However, these are the most efficient mills in the business. I would say that a good rule of thumb is that for every cubic foot of solid wood measured in log form, the lumber yield would be about 7 bd-ft per cubic foot on a green lumber basis and 10% less than that or about 6.3 bd-ft/cubic foot on a dry lumber basis. So, if a ccf or cunit is 100 cubic feet, 1 cunit of logs would yield approximately 630 bd-feet of dry lumber. However, that is only a rough rule of thumb. Really big logs have less waste to square than really small logs. If the logs were really small, the dry yield could be more like 5 bd-ft per cubic foot.
Hope that was not too confusing........ :).
WDH
That was a very good explanation of the conversion, including the many variables. And your numbers look good too.
When they invent the kerf-less "saw", and grow square logs, and stop drying shrinkage, etc, there will be higher LRF.
:)
Quote from: beenthere on April 04, 2007, 09:19:00 AM
When they invent the kerf-less "saw", and grow square logs, and stop drying shrinkage, etc, there will be higher LRF.
:)
Beenthere,
A kerf-less saw would be nice. Then there would be not those big piles of sawdust to deal with. The bad things about it is that Miss Scarlet would not have any sawdust piles to lay in ;D.
WDH,
Excellent explantion of the ccf conversion to board feet. Please place it in the
Forum Toolbox Knowlege Base in the Wood and Lumber Section.
This question of ccf conversion comes up perodically and you have expained it well.
Thanks Ron,
I did as you suggested. Hope I did it right!
WDH,
I guess my guessing has always been pretty accurate :D When I saw the details of the sale for 19000 ccf I had figured it to be just under 12 million bf. Figuring your way that 1 cunit of logs would yield approximately 630 bd-feet of dry lumber, the calculation came to 11,970,000bf. ;D I actually just estimated the same formula in my head really, and for very small sales I can guess pretty accurately, but I guess on a sale this size you could be off by a few hundred mbf. :o :D
19,000 cunits is a lot of wood!
I hope we are both right :).
Well, I'm not bidding on it, and I guess no one else is either,cause the notice I just recieved was for a re-offer of the sale. Funny thing though the original sale bid was for 19000 ccf, but now it only reads 17000. ::) Where did the other 2000 cunits go? ???
Who is putting out the sale? They probably revised the sale some to try and make it more appealing to potetial buyers. Is the name of the sale still the same??
It is a USFS sale, and the name is the same. I figured that they probably did revise it. I know the minimum bid was cut in half, but I think the problem with the sale is that several units require helicopter yarding, and there is 4,211cunits of non-saw biomass. Some of the biomass is from the tops of saw logs, but alot is from very small diameter trees. :-\
With those volumes and being in cunits I suspected that it was a USFS sale and that it was revised. That is often done if it doesn't sell the first time around on bids. It may also become a negotiated sale if there is any interest.
Wow, I'm amazed with the amount of timber sales that have come up with members on the forum. The amazing part is the amount of land that is federally controlled. Here in New Brunswick the only federal lands are Camp Gagetown and a couple of small National Parks. I say small in relation to the vastness of this country. In Gagetown, when the army expropriated those farms the army just dozed and burnt any timber in their way back in the 50's. Now they keep those openings with burning. In Fundy National Park, it's pretty much a Nature Preserve with no harvesting. I think these areas account for 2% of the forest land in the province. Too bad our provincial public forest land didn't have the same system of bidding on timberlands. I think we would be getting a better deal for our public wood and allowing many more people to have opportunity to make a living from the forest. I don't think the mills would be suffering for supply. It would be managed according to a provincial plan and cut to a plan to supply mills with a set volume allocation. It would put more foresters to work. The established mills here don't want their supply in the hands of anyone but themselves. Nothing wrong with that if they own the land, but I do as well as any other tax payer. I think the mill owners deserve just as much stress in assuring their source for timber from day to day as the guy knocking on doors looking for his next timber harvest. Pretty nice system we have when you know where, when and how much you will be cutting each year and no one else can have it besides you unless you sell them a share (sub-licensee). ;)