View Full Version : No Welding Required Lower Inspection Cover

Jim Miller
04-01-2011, 08:55 AM
I got this idea several years ago from a SWP owner, which I modified slightly. The panel
is .025 2024-T3 and the Z-channels is same except .032. The rear and pilot side Z-channel
is riveted on with 3/32 flush rivets and the forward and right side is held in place by
#8 SS screws and nutplates. A round inspection cover is placed in the fabric just anterior
to the panel so you can get your hand inside to hold the two nutplated Z-channels to
start the #8 screws. The Z channels are made just tall enough to grip the longeron's
and if too short aluminum strips can be riveted to them for a higher standoff above the
panel to give more space for the longeron tubes. I have one I made on my Colt and it
works great.

mike mcs repair
04-01-2011, 10:55 AM
that's neat! (will have to remember that for planes just being worked on that are covered already)

yours looks plenty strong, but for others, just make sure that front lip & Z is big and strong if it might someday be used on skis in deep snow... or it might become a snow shovel and fill fuselage...

Jim Miller
04-01-2011, 12:36 PM
It is a little tedious to make, getting the Z-channels just the right height, but is very strong. The channels
give a lot of rigidity to the thin panel. It makes a good place to put a flasher, which I did on my Colt.

bob turner
04-01-2011, 01:01 PM
If you do not need to crawl in there, a smaller plate can be attached just like the ones on the wing for pulley installation. I have one in the brake area that allows me to change the brakes with straight-on wrenches. Looks lots better than those original inspection rings. I always use aluminum for all inspection plate and ring grommets. Piper used some kind of flimsoid plastic.

04-01-2011, 02:25 PM
Bob, I agree with you. I am planning on using the aluminum rings from Steve Pierce. Being the nut plate junkie that I am, I plan on screwing the covers to the rings/rectangles under the jackscrew and master cylinders. I suppose one could make their own ring/rectangle/grommet in the shape of the triangular fuselage under the jackscrew too.

04-01-2011, 05:53 PM
Made a similar inspection cover for my project. I didn't want to weld on it either since the fuselage was already powder coated. I use three #85 Southco's and the clips are 4130 riveted to the .030" aluminum triangle. The Southco retainer brackets are 'glued' on with a special adhesive I can't pronounce or spell.


04-01-2011, 06:54 PM
Spinner, I like that. how tight does this fit with only 3 fasteners being used? Also, can you share further about this special glue? Is it an epoxy? How strong is it? Does it keep the Southco retaining brackets tight?

04-02-2011, 12:25 PM
Kevin, it fits very snug because I have the clips fitting tight. The adhesive is from Cub Crafters. I'll have to check the name again. It is a two-partgray colored stuff that is used in quite a few applications on the Carbon Cub including attaching the CF stringers and flap and aileron skins to their ribs.

04-02-2011, 05:04 PM
Spinner, Those Southco retaining clips that are glued to the longerons...how did you make those up? They look to me to be all one piece. I really like this idea. I am now considering doing this to mine.

On a seperate note, I have been following your progress on your blog. You are doing quite a job!


Fat Kid
04-02-2011, 11:37 PM
Sorry first time trying to post pics. Hopefully it will work this time.

This is a snow removal panel I fabricated for a PA 12 resently. I used wing style 85 Southco fasters so you don't need any tools or have to take off your gloves to remove the panel to get at the snow build up in the tail.

04-02-2011, 11:51 PM
The link didn't come thru...

Jim Miller
04-03-2011, 11:34 AM
Another alternative I may consider myself is to use steel straps MS27405-6. Wicks sells them and they could be used
to hold some aluminum angle paralleling the longerons for nut plates. This would take the dependance on the magical
properties of glue out of the equation. They are .050 steel and wrap the longeron but should not be noticeable under
the fabric.

04-03-2011, 06:51 PM
Fat Kid, That panel looks good. What are you using to hold the Southco fasteners to the longerons? Do you have a photo of the inside of the panel with the fasteners attached to the longerons?

Jim, How hard is it to open those steel straps enough to get them around the longerons?

Fat Kid
04-03-2011, 08:16 PM
Kevin I welded some simple .040'' 4130 tabs along the longerons. I bent up some brackets out of the same 4130 for the end pieces. The southco receptacles are held in place with standard AD rivets. I epoxy primed the tabs and receptacles prior to riveting them in place1907.

mike mcs repair
04-03-2011, 10:51 PM
Another alternative I may consider myself is to use steel straps MS27405-6. Wicks sells them and they could be used
to hold some aluminum angle paralleling the longerons for nut plates. This would take the dependance on the magical
properties of glue out of the equation. They are .050 steel and wrap the longeron but should not be noticeable under
the fabric.

why not weld tabs on since fabric is off? atlee's sells some real pretty ones...

this all seems allot of extra work.... I can see justifying the messing around on a covered fuselage.....

Jim Miller
04-04-2011, 07:59 AM
I forgot and the fuselage is painted. Those short piper tabs that univar sells that I used in many other places would have worked great.


Jim Miller
04-04-2011, 08:05 AM
Its not hard, they are .050 steel. The hole is perfect for a #10 flat head screw to hold the channel. When
tightened they will grip the tube very tightly and correct any distortion from prying them open.

04-04-2011, 09:42 AM
Mike, I'm not covered yet but I'm kinda past the stage of doing any more welding. I also have a wood center stringer that tapers down into the area that would be the front of the aluminum cover. This stringer is attached to the small cross tube between the lower longerons. I might be able to role a groove into the cover to clear this stringer????????

I've got some tabs that Darrel Star told me about that I welded to my frame when I was in the welding stage. These tabs are drilled for nut plates and the rivet holes are dimpled. They would have been perfect for this area.

Also, I'm not a good welder and if I did decide to weld, I'd have to have someone come over and do it for me. Could be costly for what little work that needs to be done.


04-04-2011, 03:33 PM
why not weld tabs on since fabric is off? atlee's sells some real pretty ones...

Mike, Do you have a picture of these tabs? I might consider doing something like this but unsure yet. Also, how much extra weight does adding an aluminum pan add?

04-04-2011, 03:43 PM
Spinner, I sent you a PM.


04-04-2011, 04:12 PM
Kevin, I got your PM and here's the answers:

Here's a couple of images of what the #85 Southco bracket looks like.



It is made from two parts welded together. The part that wraps around the longeron is a section of tubing that slips over the longeron and is the part that is glued. Welded to that section is a piece of flat bar with appropriate holes for a riveted Southco fastener.

You can see a little of the glue - it is gray colored.

The reason for the bend down the middle is to match the lower stringer angle up to lower longerons. Slightly different in this area than a PA18 fuselage. Too add a little confusion the second image is not from the traingle pan area, its part of my extended baggage door area, but the identical bracket. Easier to photo this one from this angle.

04-04-2011, 04:29 PM
I got it. Thanks Spinner. I'm going to talk to my I.A. to see if he will allow me to do this on my -12.

Steve's Aircraft (Brian)
04-04-2011, 10:58 PM
I prefer welded tabs....
On this one I welded on the tabs and build up the front piece out of mild steel....Just use clip nuts with #8 sheet metal screws to hold on the bottom.



Dave Calkins
04-05-2011, 11:41 AM
I'm surprised no one has mentioned a very common, and my favorite way of treating the front edge of this tail "cleanout" panel.

Have you guys seen this method?.........a piece of folded-over channel (like the fueselage "D" window channel, but straight, not curved or bent, except for the "V" at the center stringer is formed in it) is welded to the fuselage where the front edge of the lower panel will rest. The channel opening faces aft and receives the front edge of the panel.

This keeps the propwash, airblast, snow, dirt, and water out of the front edge of the panel and precludes the necessity for fasteners at the front edge.

Also, when I make these panels, I usually form the outside edges 'up' by breaking the edge over in a sheet metal brake.(just like Brian did above). This gives the panel plenty of rigidity (which, again, reduces the number of fasteners necessary), is very simple and quick to do, and adds no weight or expense to the part. I also add a strip of cessna trim to this edge as a seal/anti-chafe/finishing touch. (I, like Brian, also like to use Tinnerman clip nuts and sheet metal screws. They are easy to replace, and sheet metal screws are pretty quick to remove)

Please, No offense JIM.... or anyone :)

04-05-2011, 12:42 PM

I have pictures of that from a fellow member's plane. It is a very nice, clean, professional installation. It was welded to the frame. I could still do that. It will require some extra work to build the bracket.

Because of my center stringer hangs about 6" past the cross tube, I would need to add this to my frame.

On the flip side, I'm not going to be in the rough and be on rock beds, off field work. I might just glue one of Steve Pierce's access panels in and nut plate a cover to it. This will still give me some access to the jackscrew and trim pulley. I'm still undecided at this point.

Jim Miller
04-05-2011, 12:47 PM
That is a good idea for the front. If I was starting from a unpainted fuselage I would use that idea and 4 to 6
of the short piper tabs that have the bent sides and rear contoured round/concave to weld around longeron.
I am in process now of just using 4 to 6 of those MS27405-6 clamps to hold some 3/4 by 3/4 aluminum angle
for nutplates. The MS27405-X clamps are very handy if you don't want to weld a tab. When tightened the
edges don't come together all the way so you can really tighten for a nice fit.