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05-18-2019, 11:15 AM
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Join Date: May 2006
Location: Sammamish, WA
Posts: 654
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GPS Antenna Doubler?
I'm installing my ADS-B GPS Antenna on the top of the fuselage in front of the vertical stabilizer. I'm questioning whether or not I need a doubler. The skin is very rigid back there and the antenna very flat. There's no leverage to generate a bending motion. I'd rather not put rivets in my nice paint job.
Michael-
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Michael Burbidge
Sammamish, WA
RV-14A Empennage
RV-9A Flying?340 hours!
Last Donation: December 2019
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05-18-2019, 01:18 PM
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Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 829
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I made a backing plate that was roughly 1/3 larger than the antenna. I put rivet nuts on it and screwed the antenna into it such that it and the antenna sandwiched the skin.
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05-18-2019, 10:20 PM
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Join Date: Nov 2007
Location: Waukesha, Wisconsin
Posts: 554
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Me to
I am switching my GPS from inside mount to on top in back same as you and also plan to use a piece of aluminum as a backing plate without riveting it to the skin. Kind of like a big washer held in place with lock nuts.
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Paul 'Bugsy' Gardetto, Col, USAF (ret)
Milwaukee, Wisconsin (Timmerman Field)
N377KG - Flying (250 hrs)
RV-7A, Aerosport O-360, WW200RV
Advanced Flight 5400
Avidyne IFD440
Paint by planeschemer.com
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05-19-2019, 04:23 AM
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Join Date: Sep 2006
Location: Defiance, MO
Posts: 1,674
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Quote:
Originally Posted by Bugsy
I am switching my GPS from inside mount to on top in back same as you and also plan to use a piece of aluminum as a backing plate without riveting it to the skin. Kind of like a big washer held in place with lock nuts.
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Do you have a sliding canopy? If so, are You putting it on centerline behind slider track or off to one side and the canopy slides over the top of it?
To OP, I would use a doubler plate as skins are thin and any point mass attached locally will work on them with high potential of skin crack at the fasteners. Plus you potentially get a better ground plane for better antenna performance.
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Philip
RV-6A - 14+ years, 950+ hours
Based at 1H0 (Creve Coeur)
Paid dues yearly since 2007
Last edited by plehrke : 05-19-2019 at 04:27 AM.
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05-19-2019, 04:54 AM
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Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 996
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Glue
Glue the doubler on with 3m 2216 or equivalent. You will get some vibration damping in the process 👍
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Larry DeCamp
RV-3B flying w/7:1 0320 / carb / Pmags / Catto 3b / digital steam
RV-4 fastback w/ Superior roller 360/AFP/G3X/CPI/Catto3b
Clinton, IN
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05-19-2019, 05:42 AM
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Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 1,474
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Quote:
Originally Posted by pa38112
I made a backing plate that was roughly 1/3 larger than the antenna. I put rivet nuts on it and screwed the antenna into it such that it and the antenna sandwiched the skin.
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I did the same except used nutplates, and backing plate roughly same size as antenna (squared off corners and added space for nutplates) - see here: https://turnerb14a.blogspot.com/2018...-antennas.html
When I paint the airplane I'll bond antenna and doubler but for now just held in place with screws - torqued to Garmin specs of course.
Last edited by mturnerb : 05-19-2019 at 05:47 AM.
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05-19-2019, 07:40 AM
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Join Date: Jan 2018
Location: Golden, Colorado
Posts: 41
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I made my own. Garmin sells one for $50. I will rivet it in today. On the question of nutplates vs nuts, once I finally get my window installed the GPS will still be removable by one person.

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RV-14 N303XC : Flying
Last edited by mountainride : 05-19-2019 at 12:48 PM.
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05-19-2019, 07:41 AM
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Join Date: Jul 2017
Location: Carson City, NV
Posts: 120
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i promised myself not to do this but
PLEASE go read 43.13. The nut plate method described does not transfer the loads, resulting in local stresses in the skin - which in your case is a STRUCTURAL MEMBER. The bonding method MAY be sufficient: how were the surfaces prepared? Was there a test model? Was that article tested to failure? Was the application methodology tested [temperature/ compression/ clamping]?
There are some metal to metal bonding methods that work, obviously, and have been for some time. BUT -- I have seen some otherwise great systems fail when used in the field.
Sorry, but this would not pass my inspection. Touch up paint is a lot cheaper than replacing a fuselage skin that cracks - or fails.
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Ben K.
A&P; RLSA - A,G,W/S Falco F-8L
50 yrs of flight and counting
Dues paid 2017 thru 2020
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05-19-2019, 10:08 AM
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Join Date: Jan 2005
Location: NC25
Posts: 3,507
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How about a different GPS antenna
How about using a different GPS antenna to save on installation work?
This GPS antenna works with the Stratus ES/ESG. I spent a little money using this GPS antenna to save installation work.
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Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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05-19-2019, 11:14 AM
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Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 1,474
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Quote:
Originally Posted by Red Mtn flyer
PLEASE go read 43.13. The nut plate method described does not transfer the loads, resulting in local stresses in the skin - which in your case is a STRUCTURAL MEMBER. The bonding method MAY be sufficient: how were the surfaces prepared? Was there a test model? Was that article tested to failure? Was the application methodology tested [temperature/ compression/ clamping]?
There are some metal to metal bonding methods that work, obviously, and have been for some time. BUT -- I have seen some otherwise great systems fail when used in the field.
Sorry, but this would not pass my inspection. Touch up paint is a lot cheaper than replacing a fuselage skin that cracks - or fails.
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I very much appreciate this commentary but find it hard to understand in the context of the discussion in this thread. What loads need to be transferred, and to where? Does the antenna itself create a significant load that needs to be transferred to structure? If the skin is clamped between antenna and a backing plate, where is the load going? Those of us who are not engineers may not really understand what you're trying to say.
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