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ELT antenna top skin stiffness

EdRv7

Member
I am building an RV-7 slider and am planning on mounting my ACK ELT antenna on the top skin just aft of the F-707 bulkhead (i.e. a few inches aft of the end of the canopy slide track). The ACK antenna instructions say to install a 2 inch diameter doubler plate. I am worried that the skin there isn't very stiff, even with a doubler plate. The instructions say "13 lbs test force applied at base of antenna should cause no appreciable distortion of skin". My question is: what is the definition of "appreciable"? Anybody else mount their ELT antenna there and later have cracking or other issues?

Thanks for any advice!
 
I usually put in about a 5x5" .032 doubler and never had issues.
I've inspected other planes with no doubler, although I'd consider it being a bit light, didn't show any cracking.
My vote would be to install the doubler, to insure that 40 years from now, after avgas is a memory, there still would be no cracking there.
 
Just me

I installed a doubler there for my elt. The curvature makes it very strong. I chose to tie the doubler in to the bulkhead, but not sure if I needed to.
 
I am building an RV-7 slider and am planning on mounting my ACK ELT antenna on the top skin just aft of the F-707 bulkhead (i.e. a few inches aft of the end of the canopy slide track). The ACK antenna instructions say to install a 2 inch diameter doubler plate. I am worried that the skin there isn't very stiff, even with a doubler plate. The instructions say "13 lbs test force applied at base of antenna should cause no appreciable distortion of skin". My question is what is the definition of "appreciable"? Anybody else mount their ELT antenna there and later have cracking or other issues? Thanks for any advice!
I like how you think... Larger douber would be good as suggested. ELT does not have too much drag. If you push on it with a few lbs of force near base. It should not move and skin should not have significant deflection.

Not sure what bay you will be in, how close you will be to a frame, but you will be adequate with a larger doubler. Try and screw closer to one of the frames than mid bay...
 
I am putting in the doubler. But I noticed that the skin still deflects some even with the doubler. Maybe I'll put in a larger one as you suggest.
 
Are you riveting the doubler onto the original skin or is it loose and captivated by the antenna mounting like a big washer?
 
Are you riveting the doubler onto the original skin or is it loose and captivated by the antenna mounting like a big washer?
The doubler has 6 rivets. But it does seem small, just 2 inches diameter (per the mounting instructions from ACK).
 
This is what I did (Artec antenna). It seems very solid, and I?m not concerned about the doubler?s strength.





Disclaimer: Airplane not flying yet.
 
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