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Sub Panel Mod for Radios Stack

mfleming

Well Known Member
Patron
-7 Slider sub panel modification to accommodate radio trays.

Because I'm just starting the wiring for the basic system (not avionics), I decided that the GTR-200B and GNX-375 trays should be installed. This will help in deciding wire routes as they are significant obstructions.

Searching VAF shows plenty of photos of the finished product, sub panels cut-out with angles installed to support the trays...
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My conundrum is: How to make the incision in the sub panel accurately?
Can't find any information on this process.

I see many sub panels with the trays fitted precisely. My fear is butchering the sub panel or at least having a gaping hole.

My radio trays are fitted to the instrument panel in a way where the IP can't be fixed in place with the trays installed because the trays hit the sub panel...meaning with the instrument panel in place the trays can't be slid up to the sub panel for marking :confused:

Any hints on this process will be helpful.
 

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Measure 5 times, cut once.
These holes need reinforcement, so you can cheat a bit with the cutout a bit oversize, then make the doubler or aluminum angle opening more precise. Do just one rack at a time. Once you have one correct, measure off it for the other.
 
I haven't reached this stage yet, but looking at your setup, here's how I would approach it. Use a protractor and measure the angle that the trays make with the IP. Remove the trays and install the IP. Measure the distance between the IP and subpanel. Cut a scrap piece of aluminum that's exactly that long and the same height as the tray. Use the protractor and match drill the piece of aluminum where the trays mount at the same angle. Now you have a piece of aluminum the same height as the tray, mounted in the same orientation, that should just touch the subpanel when the IP is put in place. This should give you a good starting point for making the first cuts. If you're an overachiever, you could replicate the entire box shape of the tray, but make it just long enough to touch the subpanel.

Option 2, since your center subpanel piece isn't riveted in yet would be to remove that piece. Install the IP with the tray. Lay a straight edge across the two vertical supports and measure down to the top and bottom of the box. Measure sideways to a repeatable point of your choosing. You can now remove the IP and reinstall the subpanel piece. Do the same measurements and draw your lines on the subpanel. You done even have to measure vertically actually, just lay a long straight edge on the top of the tray and make a line on each side subpanel piece. Once you reinstall the center piece, you should be able to connect the lines you just made on the side pieces to get the exact top and bottom of the trays.
 
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Make a cardboard box the same size as your radios but cut it short enough to fit between the panels.
You could also make a styrofoam plug the same cross section to fit and then trace around it on the sub panel
 
Once you have your cut lines laid out, a multi-tool with a half moon BIM blade does a good job plunge cutting and cutting the lines. I did my sub panel and panel cuts with them off the plane and used an OSB board as a backer. I also two way taped a scrap 3/4" aluminum angle down to use as a straight edge guide. I also two way taped or used screws to fasten the panel being cut to the backer board. Otherwise the aluminum will vibrate too much and the blade wants to skate.
 
So therein lies my confusion....measure what?

From my perspective, I have no frame of reference...must be some tricks...lasers, strings...something :confused:

I installed the panel minus the trays with half of the screws to hold the panel tight. Use a 90* Ruler/square (the kind where the ruler slides inside the angle piece to make the depth adjustable) held against the interior of the panel cutouts to make the marks on the sub-panel.
 
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I did mine incrementally.

I would start though with a square on the surface of the sub panel and try to align with the radio stack opening. Then mark a vertical l line using the bottom of the subpanel as a reference. Then I would move inward a little bit to allow you to adjust it later.

For the horizontal cut lines use the same approach but mark up from the bottom flange of the subpanel and equal distance and mark your lines.

Then do a test fit and adjust a little bit at a time.

Also think about your wiring harness routing. I had a bunch of units sticking through so I decided to have some gap on the side to allow the harness to be attached to the side of the radio stack.
 
A lot of great suggestions.

Another question:

Did you reinforce the sub panel cut-out or were the angles for the radio stack enough?
 
Personally, I wouldn't waste time to get a perfect fit hole, cut it out as best you can with a bit of space around the trays. You don't want to only rely on the panel/angle tray mount to totally support the radio trays, you should stabilize the rear of the tray to the sub panel with some strap bracketry.

Add a crossways reinforcement angle if you think the cutout degrades the subpanel rigidity. Vertical reinforcement not as critical, I usually cut the cutout an inch narrower and bend 1/2" flanges each side for that.

Back to the perfect hole, this is not sufficient support for the trays (as in friction fit into the subpanel) by it's self, you should support/stabilize the back of the trays with a bracket to the sub panel.
 
Well after realizing that a precise fit was not needed due to having angles support the opening, the cut was a non event. Also, I realized that the GTR-200 would fit between the IP and the SP if I removed the backing plate.
This allowed me to tape a piece of angle to the bottom of the tray to keep it square to the IP. Then I used another smaller piece of angle to project the four sides to the SP.

Once you have your cut lines laid out, a multi-tool with a half moon BIM blade does a good job plunge cutting and cutting the lines. I did my sub panel and panel cuts with them off the plane and used an OSB board as a backer. I also two way taped a scrap 3/4" aluminum angle down to use as a straight edge guide. I also two way taped or used screws to fasten the panel being cut to the backer board. Otherwise the aluminum will vibrate too much and the blade wants to skate.

This piece of advice really made cutting out the SP easy
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Now I just have to make some straps to tie the GTR-200 tray to the GNX-375 tray and make some angle supports for the SP and trays.
 

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I'm at about the same stage as you, although I bought my panel prewired and tested from Aerotronics. Trying to "incrementally" cut the real subpanel was not going to work. So I looked on the Vans site and ordered three new longitudinal ribs and the three new subpanel parts. After all I've spent on the panel and the plane so far, this barely made a dent in my budget:D. Then I made a clear 1/16" lexan sheet to simulate the forward top skin (partial) and another to simulate the firewall, the latter mostly to keep things in alignment. Haven't progressed any further, but the next step is to offer this assy up to the prebuilt panel and measure twice and cut once. If I screw it up, I can get another one. Once I know it fits, I can transfer the dimensions onto the riveted in place real subpanel. And yes, I plan to reinforce the cutout with 3/4x3/4x1/16 angle as on mine, the radio stack goes through the lower flange of the subpanel.
 
Just bought my GTR-200 and will be doing what you did soon. Haven't seen any bad reviews on them except they won't connect with my GRT 10.1 and my Sport EX,( new Garmin SW) doesn't matter as they work standalone and will use it as a backup Com/ Intercom and they have 10 watts transceiver. On my last RV7 I did put a brace on the back also as I had a stack like you are using.
 
I’m liking the hinged tray set up you have. How will access be after it’s wired? I like the idea of it though. I cut my opening for the GTN 650 and was just going to use angle on the sides of the hole to support the aft section of the rack. Do I need more?

Should I bolt or rivet the support rack behind the sub panel?
 

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I’m liking the hinged tray set up you have. How will access after it’s wired be? I like the idea of it though. I cut my opening for the GTN 650 and was just going to use angle on the sides of the hole to support the aft section of the rack. Do I need more?

Should I bolt or rivet the support rack behind the sub panel?

So the hinged fuse block tray to the right of the avionics trays will be screwed to the bottom of the IP with three # 8 screws. I'll leave enough of a service loop so the tray can drop down for servicing.

43.13-2B says machine screws are acceptable for avionic tray supports.

I'm thinking of fabbing up a support ring out of 0.025 on the backside of the SP and on the front I'll have an angle support for the avionics trays attach too.
 

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freakshow108, your PM receiving permissions are turned off. Email me at the email in my signature.

The GNX-375 is the top tray and you can see. the tap in the upper right for orientation.
 

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PM

freakshow108, your PM receiving permissions are turned off. Email me at the email in my signature.

The GNX-375 is the top tray and you can see. the tap in the upper right for orientation.

Got that little box unchecked. Thanks for the heads up and the info.
 
Just got my GTR-200 and it came with a Back shell W/hardware 37 pin P/N 011-00950-03 kit for the GTR-200 instead of a standard 37 pin shell. The install manual has the drawings but no mention on why they use it.
The screws that hold the connector to the com have to be unscrewed from inside the mount with the com unit out which would be a pain if you had to(no thumb screws for this one). It looks like you would have to wire it with the mount and shell off also. The Back shell looks like it is suppose to work with other devices as it has 11 holes drilled in the back of the shell. I have sent this to Garmin support hoping I can leave the shell off and just put 2 nuts on the female connector to the com connector. clamp the wires to something close. Anyone having ideas, let me know how they did it, and when I get an answer from Garmin I'll pass it along.
 
The RV-14 configuration is problematic on how to mount radios in a way that makes maintenance easy.

Two thoughts:
- The best approach is to make the radio stack come out of the plane as an assembly. All connections between the stack (radios to audio panel and such) are not disturbed. Connections to the rest of the plane is done via a power plug and D connectors.
- The hole in the forward bulkhead provides a simple way to support the forward end of the trays. On the RV-10 I used a piece of hinge material, one side connected to the bulkhead the other to the bottom of the tray. Pulling the pin allows simple removal of the stack as an assembly.

Builders tend to forget that panel modifications will come down the road. A little extra planning now will make life a lot easier.

Carl
 
Got an email from Garmin on my GTR-200 wiring and he said it would be OK to just install the wire pins with out the Back shell.

That will save a little weight and much easier to do. I also found the Back shell install in the GTR-200 install manual, and there was a Garmin You tube on it also.
 
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