Replies to This Discussion

Permalink Reply by Bob McDonald on May 14, 2013 at 8:41pm

There are pictures of backing plates & locations on my page in the Bob's CH750 build or Can-Zac Spycam photo albums. so many pictures I can't remember which other than I posted some.

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Permalink Reply by Peter Autenried on May 14, 2013 at 8:46pm

http://www.eaavideo.org/video.aspx?v=1136841468001

http://www.deltapopaviation.com/FAQ.html

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Permalink Reply by Jim B Belcher on May 15, 2013 at 7:53am

Many aircraft wih sheet aluminum skins don't have skins thick/rigid enough to do a good job of supporting the antenna. The FAA's approved way of solving this on certificated aircraft is contained in Chapter 3 of AC43.13-2A It works just as well on homebuilts.

Basically, it uses a reinforcing doubler of sufficient thickness to reinforce the aircraft skin; i.e. another piece of sheet aluminum. I realize you are saying you don't have that, but it may be the best and simplest way.That's what I did on my 601XLB.

Aircraft Spruce and others sell sheet aluminum.If shipping weren't so high, I'd offer to send you a scrap that would do the job. You can likely find a copy of AC43.13-2A (or the current revision letter) on line, probably at an FAA site.

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Permalink Reply by John Austin on May 15, 2013 at 9:34am

Paul,

I scored a bargain price on a Comant VHF antenna on Ebay and it needed a substantial mount. I made a backing plate of .050, drilled-out a few rivets of a transverse L stiffener on the top fuselage, and riveted the backing plate to the stiffener and skin on the forward edge. This eliminated lateral vibration and whipping since the stiffener ran transversely. The anntenna's base was much longer in the fore-aft direction, so no problem there as far as stability:

John

N750A

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Permalink Reply by Paul Sanders on May 15, 2013 at 12:59pm

Turns out I do have some spare skins from when I upgraded the wings from Edition 2 to Edition 3, just don't know if they are thick enough. Will have to take a look when I am back home at the weekend. I suppose my real question is how thick should any backing plates be?

Thanks all for the links.... I thought I had all of your pictures committed to memory Bob, I've used them so much for inspiration. I will take another look.

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Permalink Reply by Mark Maltais on May 17, 2013 at 1:00pm

I put a simple alum plate under the skin (opposite side) where the antenna goes.  In the case of my pitot tube though, since it's a bit more heavy, I put a plate AND a couple of "L" angles above it.  If the area is closed off, I'd put the "L"s on it regardless, but if has to stay neat, like the com antenna which is in my cockpit just behind and over my head, a backing plate of aluminum seems to work fine.

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