---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Mon 04/18/05:1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:50 AM - Re: Antenna doubler plates (Mike Larkin) ________________________________ Message 1 _____________________________________ Time: 11:50:22 AM PST US From: "Mike Larkin" Subject: RE: Avionics-List: Antenna doubler plates --> Avionics-List message posted by: "Mike Larkin" I could not have said it better myself.... Mike Larkin -----Original Message----- From: owner-avionics-list-server@matronics.com [mailto:owner-avionics-list-server@matronics.com] On Behalf Of bakerocb@cox.net Subject: Avionics-List: Antenna doubler plates --> Avionics-List message posted by: Avionics-List message previously posted by: "Ralph E. Capen" > Fellow listers, I am starting the installation of my Comant CI122 com > antenna on the underbelly > of my RV6A. All I can find in the archives is Eric Newton's post on a 3" x > 6" x .040 doubler > along with a couple of others that indicate that one is required/has been > used > - check the 43.13. No mention of the basis for the dimensions used. > Obviously, the AC 43.13 should have info on the determination of the > appropriate > dimensions - but I have not learned to read that mumbo jumbo well enough > to > get any usable information from it. If someone could point out the correct > paragraph or how >they arrived at their specific numbers, I would greatly > appreciate it. Ralph Capen RV6AQB N822AR 4/13/2005 Hello Ralph, Since you are putting this antenna on a relatively large metal surface you are not concerned with providing a ground plane for electro magnetic performance purposes, but just providing some additional strength for structural purposes. The dimensions are therefore not very critical assuming that the only holes through the aircraft skin are for the center coax connection and the antenna mounting screws. The trade off then becomes one of adding sufficient additional strength to carry the bending forces on the skin from the antenna,but not adding excessive unneeded weight. You could go to Figure 4-16 of AC 43.13 and use those samples to crunch some numbers if you wish, but that is not really necessary. Cut a doubler plate in a square or rectangular shape (easier to make than a round doubler plate) that is comfortably larger than the antenna base (at least two inches larger all around should do it). Take into account the nearness of any bulkheads or other structure that would interfere with drilling and riveting. Round off the corners. Use a rivet spacing (no greater than that used in the surrounding sturcture) that works out nicely for each side of the double plate. OC -- --