[Short Fuse]

Has anyone ever ran into any structural problems when installing a inspection panel. I'm getting ready to put a panel in the tail of the fuselage, in the area where there is no middle stringer down the side. I'm going to mount my battery and ELT in this area and need to be able to get to it for mx. However, since it is of stressed sheet metal construction, I'm slightly concerned about the structural issues of putting a giant hole in the airframe. My suspicions are that it would be fine, provided you use enough nut plates and your edge distances are correct. What does everyone else think? Thanks once again for all the help!

 

[chaskuss]

Do you really need to do this?

Weston,
I can not comment on your proposal with any knowledge. That said, why do you feel you need an access panel? During your annual condition inspection, you will need to remove the panels at the back of the rear baggage compartment to inspect & lubricate the elevator pushrod bellcrank and Heim joints.
By installing these panels with nut plates and screws (preferably flush), you will make this an easy task. Save the wooden panels you made to rivet the turtle deck skin on. They will come in handy for maintenance of the items you are concerned about, as well as condition inspection maintenance. I made a cut out in these panels to clear the elevator bellcrank.
Just a thought.
Charlie Kuss

 

[Kahuna]

Has anyone ever ran into any structural problems when installing a inspection panel. I'm getting ready to put a panel in the tail of the fuselage, in the area where there is no middle stringer down the side. I'm going to mount my battery and ELT in this area and need to be able to get to it for mx. However, since it is of stressed sheet metal construction, I'm slightly concerned about the structural issues of putting a giant hole in the airframe. My suspicions are that it would be fine, provided you use enough nut plates and your edge distances are correct. What does everyone else think? Thanks once again for all the help!

With a reinforcement ring to support the plate, it will be just fine.
I have several throught my 8.
Here and here.
Enjoy,

 

[Short Fuse]

With a reinforcement ring to support the plate, it will be just fine.
I have several throught my 8.
Here and here.
Enjoy,

What do you think about joggling the panel? I modified my joggle tool to go around corners and curves, and to be able to start in the middle of a panel, instead of a corner edge. After a couple practice panels, I'm good enough with it that I think it will do a great job on the plane. Do you think there will be any problems with not having the reinforcement ring? Or is it required for additional strength. Thanks

 

[Kyle Boatright]

What do you think about joggling the panel? I modified my joggle tool to go around corners and curves, and to be able to start in the middle of a panel, instead of a corner edge. After a couple practice panels, I'm good enough with it that I think it will do a great job on the plane. Do you think there will be any problems with not having the reinforcement ring? Or is it required for additional strength. Thanks

I'm an engineer, but don't do aeronautical structures. My opinion is that if you remove a section of skin to provide access to something, you need to go with a reinforcing ring. The larger the opening, the more important the reinforcing ring.

Additionally, you really, really want to avoid inspection panels that result in sharp inside corners once you've made the cut-out. Those are stress concentrations and do very bad things to the structure, both from a strength and longevity standpoint. It is probably better to make slightly larger openings with well radiused corners.

 

[MJarreau]

Haven't seen this... ..primer?

Charlie,

What's with the white interior? Did you epoxy paint the interior of the entire plane?

Curious,
Michael

 

[chaskuss]

Charlie,

What's with the white interior? Did you epoxy paint the interior of the entire plane?

Curious,
Michael

Michael,
Actually it's PPG's Delta (equivalent of DuPont Imron). It's over Sterling U-1201/U-1202 Mil Spec epoxy primer. It's actually Vans gray. The photo was a bit on the dark side. I used a photo editor to lighten it up, that's why it looks white. The Gray doesn't go all the way back, the primer does. Look carefully and you will see the yellow primer on the side skins behind the elevator bellcrank. I did apply the finish paint to the longerons, faying surfaces and the belly skin, all the way to the rear.
I primed and painted all the parts prior to re-assembly and riveting.
Charlie