wood species question

"Gordon Arnaut" wrote in message
...
Ha, ha, ha...another chestnut from the avionics Hemingway of Kitplanes.

Regards,

Gordon.

PS: For anyone out there that might still be interested in serious
discussion of wood, I want to just add a little about compressive strength
and tensile strength as it relates to wood species substitution.

Using the same FPL data I used earlier, we see that spruce has a maximum
crushing strenght of 5,650 psi, while pine is 4840 psi, which makes pine
exactly 85 percent as strong in compression. This is nearly the same
difference as in bending -- and as I noted earlier, most of the other
measures will be similarly in line.

But just to see if my statement that 7/8' pine will adequately substitute
for 3/4 spruce, let's calculate. Since stress is force per area, we can
see
that a 3/4" spruce member will be able to withstand a maximum compressive
stress of 0.75(squared) x 5650 = 3178 psi.

How big would our pine member have to be? Well by rearranging the formula
3178 divided by 4840 will give us the dimension squared, which is 0.81
inch,
again somewhat less than 7/8".

So just as in the bending moment calculation we see that substituting 7/8'
pine for 3/4" spruce gives us a member that is actually a little bit
stronger. It is also a tiny bit heavier, but this is negligible.

However I should point out that going through the exercise we just did is
not proper methodology. I am only doing it to prove a point.

The proper method is to first identify the structural member we are
interested in analyzing, like I did with the wing spar. Next we have to
know
how much load this member is expected to carry. Only then does it make
sense
to determine the size of the member.

But like I said, let's see if Mouth-Foamer can tell us which pieces of the
plane are under pure compression or tension. (Since he is so concerned
aobut
that and is basing his whole character assassination on me on that stupid
notion).

In the meantime, I hope Mr. Personality is getting the couch-time he so
desperately needs. And I hope he doesn't forget to remind his analyst,
"first do no harm."

And,,,,,, who gives a f***ck