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Antenna doubler plate - prime or not

 
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recapen(at)earthlink.net
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PostPosted: Sun Jun 17, 2007 4:59 pm    Post subject: Antenna doubler plate - prime or not Reply with quote

Fellow tron chasers,

I'm putting a comant bent whip on the underside of my RV6A. I have a good
doubler plate (derived from the AC43.13) - pictures if anyone wants to see.
My question is should I prime it?

My initial thoughts are that the existence of the metal structure will
provide the ground plane even if it is not bonded electrically to the
structure - meaning prime on......
Otherwise, how is bonding effected as there is a cork gasket that is to be
installed? Do the four antenna mounting screws provide sufficient bonding?

Thanks,
Ralph


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douglist(at)macnauchtan.c
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PostPosted: Sun Jun 17, 2007 7:19 pm    Post subject: Antenna doubler plate - prime or not Reply with quote

At 20:55 -0400 6/17/07, Ralph E. Capen wrote:
Quote:
I'm putting a comant bent whip on the underside of my RV6A. I have a good doubler plate (derived from the AC43.13) - pictures if anyone wants to see.
My question is should I prime it?

My initial thoughts are that the existence of the metal structure will provide the ground plane even if it is not bonded electrically to the structure - meaning prime on......
Otherwise, how is bonding effected as there is a cork gasket that is to be installed? Do the four antenna mounting screws provide sufficient bonding?

Back in ancient history - about 1980 - Narco put out an installation note that said not to use those cork gaskets but rather to assure conductive contact of the metal of the antenna base with the skin of the aircraft. They said to seal, after torquing the screws, with silicone rubber from a tube - bathtub caulk.

As for the doubler, I doubt if it makes any electrical difference and priming would be good if corrosion is a consideration. You do want the BNC connector to be well grounded to the aircraft skin at the antenna site.

Oh oh. . . RV6A? Is that fiberglass? If so I may be all wet.
--

--> From the U S of A, the only socialist country that refuses to admit it. <--


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recapen(at)earthlink.net
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PostPosted: Sun Jun 17, 2007 7:32 pm    Post subject: Antenna doubler plate - prime or not Reply with quote

The 6A is aluminum....thanks...
---


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reichec



Joined: 23 Apr 2007
Posts: 26

PostPosted: Mon Jun 18, 2007 2:34 am    Post subject: Antenna doubler plate - prime or not Reply with quote

You can prime it but I would spot face the holes where they pass thru the
doubler on both sides and on the external skin from the inside, use the cork
gasket. Comant wouldnt include it if they didnt want you to use it. The
screws passing thru the antenna provide the connection to the ground plane
thru the double and back to the skin if you use a spot facing brush. Make
sure to seal the antenna with fuel sealant (if you want a long lasting seal
that wont be affected by most anything) or use some RTV type bath caulk.
The secret to smooth lines for taping the sealant line is to use 1/2"
electrical tape of a good grade and leave 1/8" gap or greater. Tape down
around using one hand to unroll it and your index finger on the other hand
to get the spacing right as you bend the tape around the curve of the
antenna, around the base your tape should look like a fish when you are
done looking down... and at the back point, I just cut a 1" piece and square
off the pointy part. This whole procedure takes some practice, work quickly
with the glue as the 1/2 hour working time fuel sealant or RTV really cures
fast in the summer heat. Have paper towel on hand or a helper with some to
hand to you, use your fingertip to make the glue fillet, the edges should
end at the edge of the tape lines so you make it pretty. As soon as the
fillet looks good, peel off the tape so you dont get rtv curing to the tape.
If you get ribbons of glue that fall down back onto the paint, its easiest
to let them stay and cut them off after it cures.

If you have not yet painted your airplane, DO NOT USE SILICONE RTV!!! Use
fuel sealant, it can be painted over and up onto the antenna for a
professional looking finish like the OEMs do.

Good luck,

Charles Reiche
---


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