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Old 11-11-2019, 12:06 AM
kaa kaa is offline
Join Date: Dec 2013
Location: Boulder, CO
Posts: 137
Default Subpanel repair question

Hi all,

So, last week my vacuum pump failed and I took it as a hint that I should finally start my panel upgrade. The plan is to go from steam gauges to G3X. Now, I haven't built an airplane, and while I'm pretty comfortable with the electronics and wiring, metal work is fairly new to me. So I'd like to ask a few potentially dumb questions if you don't mind.

In looks like in the course of years the subpanel on my RV-7 (slider) endured some surgery:

I now need to patch at least some of these holes to mount G3X components onto. What would be my best course of action? My current plan is to make a patch out of a 0.040 sheet and rivet it with a combination of AD4 where I can squeeze them and cherry rivets where I can't (I'm not set up for riveting with a rivet gun). Would a single row of rivets be sufficient? Given how decimated the subpanel is, it's probably not very structural?

Also, F-712A-L was also cut for some reason without any reinforcement. Should I do something about it? Maybe add a angle stiffener or something?

Thanks for any advice!
Konstantin Azarov
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Old 11-11-2019, 11:27 AM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,584

I?ve seen much worse. Clean up the edges of the existing cut outs & fashion panels to fill in with, .032 is plenty heavy enough, cherry max or LP4-3 pull rivets would work. Might be good idea to plan component placement first so you end up with flat surfaces where you need them.
I have installed a .040 or .063 angle along the bottom edge, side to side on some to stiffen up the sub panel on some.
built a few RVs, rebuilt a few more, hot rodded more, & maintained/updated a big bunch more
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Old 11-13-2019, 09:42 AM
Raymo's Avatar
Raymo Raymo is offline
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,340

Agree with Ralph. .032 is fine for the patching. See AC 43.13 for proper methods.

Also, consider removing the insulation from the interior firewall; it's been proven to be a bad idea if there is a fire in the engine compartment.
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines (aka Hoser)
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Old 11-13-2019, 08:54 PM
Scott Hersha Scott Hersha is offline
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 2,018

If it is structurally sound now, there’s no need to fill any holes left by the prior owners surgery. However, that bulkhead is structural, so you need to assess if it still is. When you cut big openings in the web of a bulkhead, make sure that the lower cross angle is capable of handling that load in concentrated places that are left. Usually this means reinforcing the lower cross piece angle with a beefier angle. In order for the web to carry the load to the newly reinforced lower angle, it needs to have enough strength (width) to carry that load to the concentrated points that go to the lower structure without buckling because it’s too thin, kind of like a bridge. This is very important in a slider airplane where the center rib with the heavy angle, supports the windshield bow/rollover structure. That section needs to provide vertical and longitudinal support to the roll bar in the unlikely event of a rollover/flip over. You can remove a lot of material from that bulkhead web as long as you support what’s left with heavier/stronger materials, usually angles. The only reason they didn’t do this in the beginning is because a bulkhead with bent edges and almost solid web is lighter and easier to make. It doesn’t work well with the extensive avionics equipment that we are used to using now, but can still be modified safely if done properly.
RV6/2001 built/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019 Flying
RV6/Used kit purchased 2021 building
Cincinnati, OH/KHAO

Last edited by Scott Hersha : 11-13-2019 at 08:58 PM.
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Old 11-16-2019, 11:20 PM
kaa kaa is offline
Join Date: Dec 2013
Location: Boulder, CO
Posts: 137

Thanks everyone for the tips, appreciate it. I've been reading 43.13 and other stuff too.

I removed the firewall insulation since I took the photos, thanks.

Scott, could you clarify your comment about vertical support for the roll bar? I don't quite see how the subpanel can carry much load vertically, given the way it is bent - it seems like it mostly transfers loads from side to side of the fuselage (and maybe torque?).

Speaking of which, the bracket connecting the subpanel to the central rib looks like this: It seems to have cracked around the top right rivet so that one side of the sheet metal is level with the manufactured head. Bottom left rivet looks too short or overdriven as well. Should I try and repair this? It's very tight quarters there, and I don't want to make things worse.
Konstantin Azarov
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