Well, compare the numbers for a pipe and box section and you will se my
14% rule of thumb...

Cheers

gonefishiing wrote:

that's what i'm looking for --thanks
although it sounds a higher than i would have suspected and i'll probably
use a more conservative number : something between a pipe section and a box.
if it looks like it approaches anything critical: i'll dig out the actual
moment of interia


gf.

"Nav" wrote in message
...

You can use a simple rule of thumb. If you know the moment of intertia
for a box section of the same wall thickness and outside dimensions the
moment of inertial of the tube or ellipse that has the same dimension is
about 14% less.

Hope this gives you what you want.

Cheers