wrote:


But "lb-ft" are the wrong units. Pound-feet or foot-pounds, are
units of energy or moment or vice versa, there is a convention for
the ordering of the factors, evidently preferred by professors of
engineering who are weak on the concept of the communitive
property of multiplication. Sometimes you will also see lbf-ft
or ft-lbf. In civil engineering "Geodesics" may be defined as lines
of constant energy. I _think_ that means that the moment supported
by a structure along those lines is constant, implying constant
potential energy. R. Buckminster Fuller could no doubt have
explained it far better.

IMHO "lbf" is silly anyhow as "lb" should be understood
to be force unless otherwise specified since pounds-mass is an
obnoxious unit, slugs are far easier to work with when you need
to use honest-to-god ACU mass units.

(Watch out, a linguist might pop up any minute and start a
discussion of how words used to refer to mass and weight have
evolved over the millenia. It is actually quite interesting.)

Or, they might ask what the "communitive property of multiplication"
isg.

You are absolutely right, and as a traditionalist, I applaud you. But
I also have to ask if you really enjoy ****ing into the wind like
this? Sometimes right (technically) can be silly (practically).


I found some that say that too. Few sources give any sort
of range but I expect that there is considerable natural
variation in the material properties of wood, +/- 10% for
most species would not surprise me.

I agree. Some indication of variability would be helpful. I wouldn't
be surprised if a 90% confidence interval was even larger than +/-
10%. Not the same thing as tree-to-tree variation, but look at the
variation by water content, where the compression perpendicular to the
grain (in lbf/in^2) varies for sugar maple from 640 (green) to 1,470
(12%MC). (source
http://www.fpl.fs.fed.us/documnts/fp...tr113/ch04.pdf (cited
earlier in the thread), page 4-10)

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