We had to think about this long mount a long time. It took several days of discussions before we settled on this remote transponder (GTX 23/ES) mount. First, whatever we put here, where the aft battery should go, we need to be able to remove just in case I have to put the battery back here later for CG reasons. We have the big heavy motor up front but this is an 8A and there is going to be a composite prop up front, so, I’m electing to go with an ultra-lightweight battery on the firewall. The aft mounted ELT, Radio and heavy transponder should make up for the lack of aft battery weight.
We purchased some 3/4″ square tubing from Spruce. Two of these span the fuselage and a single standoff angle on each, tied to where the aft battery would go, provides some of the load bearing. Everything is bolted and screwed into nutplates so you only need one hand to remove.
There is plenty of clearance between the case and the elevator tubes. The transponder slides in without any fuss. The case is held on the rails with four AN509 8R14 screws with nutplates on the underside of the rails.
