(Toss that last "cookbook" message I sent into the bit bucket. Stan
Griffiths was kind enough to point out that I botched the formula
description. Here is what I should have written)
For the folks that enjoy knowing how to do this stuff yourselves:
Section modulus(of a hollow cylinder) = pi*(D**4 - d**4)/32D
Where D is the outer diameter and d is D minus two times the wall thickness,
"*" means multiply and "**" means raise to the power of (and pi is 3.1415).
If you divide the section modulus into the inch-pounds of force on the mast
you get the bending stress which must be less than the yield strength of the
material to avoid damage.
(From pages 3-4 to 3-6 of the Leeson book)
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com