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Tip up forward skin access panels or not

agirard7a

Well Known Member
I am ready to rivet my forward top skin for my tip up RV-9.
I am contemplating cutting in access panels to better service
Electrical forward of the sub panel. My question is should I bother?
Have any of you regretted not putting them in and having to crawl under the panel when (not if) something needs to be serviced. Those that have, what did you do to keep them from leaking?
 
I have done a lot of re-work under there since building, including a new panel. While I dislike crawling under there, it is not the end of the world. I honestly don't think that an access panel would have helped that much, as you probably couldn't get two hands in there and still be able to see what you are doing with your arms stuck in the hole.

I do wish that I had spent more time creating a more organized routing system for the wiring though. That would have been time well spent.

Larry
 
It's all in the design

While I've got to say that I detest getting in there upside down. I did a fair amount of planning so that everything would be accessible from beneath. It's all quite straight forwards and doable. It's not fun though but I wanted to keep the exterior smooth and simple.

External access panels arent necessary.

IMG_1886.png
 
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You will be glad you put the access panels in

I have done modifications/upgrades to my -6A at least 4 times since I purchased the airplane about 5 yrs ago. The access panels I put in have meant not once have I had to get on my back, under the panel. I could not have done the upgrades (77yrs old) if I had to get under the panel. (Now, if I had just cut panels in the side of the fuselage so the autopilot and adahrs installs would have been easier)!!


Ron
 
Remember an access panel is between 0 and 75% effective in carrying the skin loads depending on how much doubling around the panel you add and the number and type of fasteners you use to attach the access panel. There are places where skin sheer loads can be pretty high.
 
The best access panels are large, glass cockpit displays. The 10" G3X touchscreens are wonderful in that regard, although connectors on the radio stack are still only accessible from under the panel.

Second the idea on planning your wiring, and make sure that you have service loops so that you can work on the connector plugs. Color code and label your wires -- you can get a wire labeling machine for less than $200, either as a chapter purchase or you can resell it or rent it out afterwards or... Use real wires, too, not automotive wires.

In addition, make sure that you can replace any components that are bolted down. My RV-9A is carrying around one abandoned piece of equipment that was too hard to get loose.

Also, document your work so that anybody else (mechanic, new owner) can work on the plane. Easy to do, adds value.
 
The VAF Search is your friend

Al,
Do a titles-only search for 'access panel', and you'll see several good approaches to installing access panels on the forward skin. However, be cautioned: The forward skin is a very important structural part of the airplane's design.

When I called the Vans engineers asking how to go about this correctly, their immediate reply was "do not do it." At the time, I intended to make the entire forward skin removable by installing platenuts on the ribs, and to drill and tap #6/32 holes through the longerons. They vehemently urged me not to do that, because they had NEVER run an engineering study of how such a mod might change the forward fuselage's structural strength.

Having said all that, one of the engineers told me that if I'm going to install access panels anyway, then please be sure to make the edge doubler AT LEAST the same area as the panel hole, preferably larger. Then use plenty of rivets to affix the doubler to the forward skin. Same for the screws that hold the panel to the doubler.

Click on my Kitlog link below, and browse the "Fuselage" section entries from Dec 2014. That set of entries gives the whole story of how I added access panels to each side.

You can see one of my panels in this photo:
IMG_3743-X2.jpg


As for how I made it watertight: I used non-paper gasket material from O'Reilly's Auto/Aviation Supply, trimmed to fit between the panel and the doubler. Each panel's 24 #8 screws has a #8 thin nylon washer. I have flown through IFR rain with this....zero leaks.

Note that I initially tried the Pro-Seal technique others have used. That didn't work for me, but you may have better luck. My gasket approach works fine.

Am I glad I did it? Most definitely, and Randy Richmond (my A&P) and Walt Aranow (my avionics miracle-worker) both expressed their gratitude as well. It made access to my forward electronics much easier.
 
If I had to do things over again I would have made the entire forward canopy deck skin removable.

Ben,
Read my post just above. I'm not sure how you would have approached the removable skin, but I was going to use #6 flat-head screws in platenuts (ribs) and tapped holes (longerons). The Vans engineers waved my off wildly. They've never run a structural engineering study to see how this approach might compromise the forward fuselage's strength.
 
Just make the panel removable

With some planning, you need never crawl under the panel. All panel components inter connections come out with the panel, all panel external connections are via D plugs (non-power), large pin Molex for power, or coax connectors for antennas.

The RV-8A and RV-10 panels come out of the planes in less than 15 minutes.

Carl
 
Forward Access Panels

There is a lot of very useful space forward of the subpanel if you need it and have access to it. I installed access panels on both my RV-9A, tip up and on my RV-7A, slider. In both cases I used .040 for the doublers and lots of screws.

To see the access panels on the -7A click here and scroll down to post #40.

I agree that the removable big EFIS screens provide great access aft of the subpanel, but there was no way I could get access to everything from below. For example the backup battery, the remote com, and the VPX Sport are located between the firewall and the subpanel.

The panels also gave me access to the wiring connections on the back of the GTN 750 which protrudes through the subpanel.
 
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I am ready to rivet my forward top skin for my tip up RV-9.
I am contemplating cutting in access panels to better service
Electrical forward of the sub panel. My question is should I bother?
Have any of you regretted not putting them in and having to crawl under the panel when (not if) something needs to be serviced. Those that have, what did you do to keep them from leaking?

I guess my question is...How often do you think you're going to need to get in there to service anything? I think in 5 years now of flying (not much by some standards, but not an insignificant amount of time, either), I've had to get to the forward section once, maybe twice. I think one was to run a couple of extra wires forward when I switched to Kavlico transducers, but that's about it.

Not worth the effort, IMO, if you're installing new, modern glass panel stuff and plan the layout properly.

Granted, it *does* mean more work initially when installing all the wiring and components during the build, but after that, I think you'll generally find that you don't need to get back up in there very often, if at all.
 
Wait until you need them.

I decided to wait. Figured I'd cut access panels if I ever needed them.
 
You don't need them if you leave yourself LOTS and LOTS of extra wire, aka service loops for each connection. Like a foot (or two).
Getting under the panel isn't a big deal. You'll do it at least for every annual to make sure everything under there is torqued and tightened.
 
One option is to make some sort of mounting panel or rails under the forward area between the firewall and the sub-panel.

The misc. boxes you need can be mounted upside down into nut plates and will be easier to change from below.
 
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