Easy Mount for GPS Antenna on Firewall

Here's a convenient and inexpensive way to mount your GPS antenna on the firewall. We somehow ended up with a spare RV-8 aileron trim servo bracket that mounts on the fuselage floor. It's just about the right size to mount a GPS antenna. We had to modify it by making a top out of .040 aluminum, bent the sides down 90? and match drilled the holes in the antenna and riveted it to mount.

Here's the trim motor mount on the firewall:





And here with the top riveted on:



When I've done this previously, it's usually necessary to support the front end with a small strut attached by an adel clamp to the top engine mount tube, so we'll do this later in the build.

Other piece of hardware

The mount looks great Pat. Can I ask what the other piece of hardware is to the left of the mount, I'm guessing it's to mount the various fluid sensors to, just not familiar with it.
Many thanks.

Simon, yes, it's the standard sensor manifold for oil, fuel, manifold pressure sensors (usually).

oil filter

Seems to me that the mount would make it hard to get to your oil filter

Tooch said:

Seems to me that the mount would make it hard to get to your oil filter

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This is true to some extent but it is still accessible.

For me personally, I wish I had mounted my GTN antenna exterior to the skin someplace. While the performance seems to be just fine the way I have mine mounted under the hood, Garmin actually frowns upon it being mounted in this location. There have been several reports of these antennas failing and I had one of them that did. Who knows if this location contributed to the failure or not but it sure is something to consider.

I sure like the clean look and no drag of a hidden antenna however!

I too have my 650 antenna mounted under the cowl and have had no issues now for over 300 hrs. Since I have read about others issues with that location, I now mount the antenna on the turtle deck next to the slide and rear seatback bulkhead under the canopy on the RV8. I do like Pats solution though.

I've had my RV-8's antenna mounted pretty much like that for almost ten years of flying (this is a 430W antenna), and it works fine. The only problem is something that you don't discover until later - if you use standard Van's hinges and pins, the antenna is always in the way reaching through the oil door to put the right side hinge pin back in place. It's the law of unintended consequences when it comes to design modifications......

That location has worked well for me on several builds, but there are a couple of things to think about.
If you are using hinge pin mounting for the cowling, be sure the mount doesn't get in the way
Also consider the oil cooler location
Get the antenna as close to the cowling as possible without rubbing.
I make a mount out of two pieces of aluminum, similar to a tent made from two cards, using a hinge to connect them at the forward Edge and hinges on the firewall for the other two edges. You can determine length of the pieces when fabbing. This allows you to pull the pins and let the antenna drop flush to the firewall for maintenance. Also, adding a bend to the sides makes it stronger but I don't that is really required, since I have done them without bends with no issues.
My advice is to run the antenna cable to the engine compartment, make the mount, but wait till the engine is mounted to install the antenna mount. You can save yourself the trouble of maybe having to move it later.
Good luck

Brantel said:

This is true to some extent but it is still accessible.

For me personally, I wish I had mounted my GTN antenna exterior to the skin someplace. While the performance seems to be just fine the way I have mine mounted under the hood, Garmin actually frowns upon it being mounted in this location. There have been several reports of these antennas failing and I had one of them that did. Who knows if this location contributed to the failure or not but it sure is something to consider.

I sure like the clean look and no drag of a hidden antenna however!

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Hi Brian, I mounted the GTN650 antenna on my -6 externally behind the canopy (slider) and this would have been my first choice, but considering all of the possible locations on the -8, this just seemed like the best way to go. I think you're right that a dorsal mount is probably best on your airplane (and all -6's and -7s). I did mount my G3X antenna (GA56) under the cowl and so far it's been flawless for almost two years. Here's the -6 mount:

Can anyone give me the Vans part number for the bracket?

This looks like a good idea but I'm building a -10 and don't have the RV-8 part numbers. I'd also appreciate knowing if two GPS antennae can fit on this bracket (hard to tell from the photo).

bob888 said:

This looks like a good idea but I'm building a -10 and don't have the RV-8 part numbers. I'd also appreciate knowing if two GPS antennae can fit on this bracket (hard to tell from the photo).

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I don't believe there is a part number for these as the builders have designed and fabricated their own brackets.

jthocker said:

I too have my 650 antenna mounted under the cowl and have had no issues now for over 300 hrs. Since I have read about others issues with that location, I now mount the antenna on the turtle deck next to the slide and rear seatback bulkhead under the canopy on the RV8. I do like Pats solution though.

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Any pics of the rear mount? How did you deal with the curvature of the rear fuselage mating with the flat antenna base?

"Can anyone give me the Vans part number for the bracket? "

The P/No. for the bracket in the first two pics in post #1 is F-8111 "Support Bracket"
It's shown on the RV-8/8A Electric Aileron Trim Drawing # OP-01
Currently $9.50 on Vans "The List".
Cheers,
Paul.

I thought I would update this thread now that the airplane is flying. The RV-8 part number for the aileron trim bracket is indeed F-8111 and available from Vans on "the List." There was some concern voiced about interference with the oil filter. This has not been the case:



We have 9 hours on the airplane to date and as others have said, this location for the GPS antenna has worked out very well. As for mounting two GPS antennas at this location, it would be possible with the same mount, but you would have to make up a larger "top" and match drill it to the mount.

We have not seen the need to support the front of the bracket.