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what is "fbm/acre"?

Started by jeff, March 11, 2001, 03:33:17 AM

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Jeff

I received this question from "Bill". I answered it to the best of my ability. I told him I would also post it here for you guys to follow up on in case I am, as my wife says, "Not quite right"
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Bill's question
Hello Jeff--

Thanks for the "heads up".  I read the log rule page.  Equipped with new
knowledge, let me refine my question.

In "Silvics of North America", the article on Noble Fir stated a max volume
like this:  "5752 m^3/ha (82,200 ft^3/acre or 407,950 fbm/acre)"

I'm trying to figure out what an "fbm/acre" is.  The glossary to "Silvics"
defines "fbm" as "foot board measure", which apparently isn't the same as
"mfb" (i.e., 1000 X board feet).  But if "fbm" refers to board feet, then is
it according to the Doyle rule, Int'l rule, Scribner's rule, or some other
rule?

If you or any of the foresters on Timber Buyers could me, I would appreciate
it.

Thank you very much.

Bill
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My answer
Hi Bill,

     Lumber and Log volumes are such a wonderful thing to try to explain! As stated I am not a forester, but I am a sawyer in a sawmill and Have been for 22 years so I can give you my take on the answer, then I will post this on our forum, and you will still get a direct response from our forester (who appears to be out of town since he has not answered yet)

First, 5752 m^3/ha  is the metric measure, (5753 cubic meters per hectare).
Then,  82,200 ft^3/acre refers to the imperial unit,(82,200 cubic feet per acre)
Followed by, 407,950 fbm/acre, (407,950 Board feet per acre)

fbm=144 cubic inches of volume (1 board foot). Doyle, scribner,international, are formulas to, and this is important, estimate the volume, but once a volume is determined, fbm is always=144 cubic inches

The above volume statement may very well have been made using direct mathematical conversions of one volume measure using conversion tables to achieve the different measures. Which log rule did they use? Who knows. They may actually have been conversions from weight, which is a whole new ball game!

Hope I have been of some help,
Jeff...

Bill, here are some conversions:


1 FBM  = 1board foot 12"x12"x1"
1 MFBM = 1,000 fbm
1 MSF  = 1000 square feet (veneer or panel board)
1 cunit  = 100ft3
1 cord  =128ft3 4'x'4x8' (85ft3 solid wood, 15ft3 air, and 28ft3 of bark)
1 tonne =1000kilograms=1.1023 tons
1 ton  =2000lbs=0.9072 tonnes

#of imperial units X conversion factor = metric units    #of metric units/conversion factor =imperial units

Round wood
1MFBM =5.1282m3
1Cord  =2.4070m3
1Cunit  =2.8317m3

Lumber
1MFBM =2.3598m3
1Cord  =1.1075m3
1Cunit  =1.3029m3

Wood Residues (includes chips, shavings, sawdust and bark)
1 Bone Dry Tonne =2.6525m3
1 Bone Dry Ton =2.4067m3
1 Green Tonne =1.3262m3
1 Green Ton  =1.2035m3
1 Cunit  =2.8321m3

Dense Hardwood Residues (for chips, shavings, sawdust only)
1 Bone Dry Tonne =1.8488m3
1 Bone Dry Ton =1.6775m3
1 Green Tonne =0.9233m3
1 Green Ton  =0.8388m3
1 Cunit  =1.9740m3

Roundwood Weight    
1 metric tonne =m3    1 Imperial Ton =m3
White Pine  =1.1198m3   White Pine  =1.2344m3
Red Pine  =1.1820m3   Red Pine  =1.3030m3
Spruce  =1.3004m3   Spruce  =1.4334.m3
Jack Pine  =1.2376m3   Jack Pine  =1.3642m3
Balsam Fir  =1.0870m3   Balsam Fir  =1.1982m3
Hemlock  =1.1273m3   Hemlock  =1.2426m3
Birch   =0.8873m3   Birch   =0.9781m3
Poplar   =1.0091m3   Poplar   =1.1123m3
Mixed Hardwood =0.8929m3   Mixed Hardwood =0.9842m3

 Length
1 mile =1.60934 kilometres
1 km =0.621371 miles
1 inch =2.54 centimetres
1 cm =.3937 inches
1 metre =3.28084 feet
1 foot =.3048metres

Area
1 acre =0.404686 hectares
1 hectare=2.47105 acres
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Ron Scott

Well done! Save for future reference.

It gets quite confusing when terms are reversed in cubic foot, board foot, mbf, cords etc. and then the different volume and yield tables are included plus weight factors.

I like to keep it simple and stay with the standards of MBF, Cunit, and International 1/4 rule. Those that use other rules can then convert for their specific need and use for whatever rule they are comfortable with.
~Ron

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