At 12:49 PM 3/15/2006, Bruce Ferratt wrote:
>My mast is 1 1/4" OD. It is solid, round.
So, you can apply a bit of simple mechanics..
bending stress is =Moment/section modulus
Section modulus for a solid rod is pi/32 * D^3 or 0.19 inch^3 for your rod.
Yield for 6061 aluminum is probably around 40,000 psi, so rearranging a bit:
40,000 lb/in^2* 0.19in^3 = 7700 in lb.
You've got 8 ft (96 inches) sticking out, so 7700/96 = 80 pounds.
One generally likes to leave a reasonable safety factor to allow for
imperfections in the material, etc. Maybe, a factor of 2 would be
reasonable here? So, your at 40 pounds load at the end of the mast.
I believe you said 70 mi/hr. For air drag, load (lb/ft^2) = V(mph)^2/391..
12 pounds/square foot.
So, you get a total windload area of 40/12 or about 3.3 square
feet. (don't forget to allow for the half square foot or so for the
mast). Doesn't look like you're going to be putting up a full size 80m
yagi on this<grin>.
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