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Re: [TowerTalk] Aluminum mast

 To: "Bruce Ferratt" , kd4e@verizon.net Re: [TowerTalk] Aluminum mast Jim Lux Wed, 15 Mar 2006 13:56:13 -0800
 ```At 12:49 PM 3/15/2006, Bruce Ferratt wrote: >Doc- >Hello. >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. _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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