Aluminum fuselage skins under doors (4-place)

[Zzz]

I'm one of those guys who raised their door sills with the intent to build gullwing seaplane doors. Because of the new shape of my door sills, I'm having to make new patterns for the aluminum skin that covers between the sill and the lower longeron, around the strut attach and aileron pulley.

First, a few questions about using this method at all: I'm assuming it's to provide a stronger kicking surface than fabric for a high-traffic area getting in and out of the aircraft? Makes sense to me. Super Cubs have a bi-fold door that protects this area when loading. Eric Newton's manual just shows fabric used, so I suppose others are doing that too.

Since the skins only extend about halfway back, there's no obvious vertical tube to terminate the fabric. Page 43 of the quickbuild manual shows a piece of aluminum angle should be adel-clamped to the fuselage to provide this vertical fabric terminus. But, this is the only source for guidance on the task, and those photos are not that good.

Anyone have some better guidance? Pics?

I really dislike adel clamps for something that's a fixed point for fabric. I can weld tabs on, but I'd like to see some better detail of house others have accomplished this.

Another question: It appears that the lower edge of these skins is broken around the longeron, then the portion that folds under the belly screws to the belly skin that covers around the shocks. If one does not used the side skins, do you then weld tabs to the longeron to secure the belly skin?

[jaredyates]

http://bearhawkblue.com/optional-aluminum-panel/

[jaredyates]

If you'd like to share photos and directions of how you do it, we'll add them to the manual.

[22LD]

I ended up welding light steel angle between the bottom door former and bottom tube. Then installed three plate nuts in the angle.

[rodsmith]

I ended up welding light steel angle between the bottom door former and bottom tube. Then installed three plate nuts in the angle.

That's what I did also.

[nichzimmerman]

I wanted to cover the area in fabric but wanted to have some structure around the aileron pulley and strut fitting, so I made a small aluminum piece that attaches only to the lower longeron (by welded tabs) and forward door former.
The idea is that the fabric will span the entire space between the lower door and longeron, and will be glued to this piece. Then I can cut the required holes in it. I can attach a pic when I get home this weekend.

[whee]

I don't see a need for AL to be used under the door in normal conditions. The plane I flew for a summer had fabric under the door and it was fine. When I raised my door sills I decided to use an AL panel under the doors to help stiffen the sill. I didn't see a reason to end the fabric part way so mine extends to the door post.

Untitled by Jon Whee, on Flickr

[Zzz]

Thanks all for the replies. On one hand, I like the idea of saving some weight with pure fabric, one the other hand I figure why not just do aluminum from door post to door post. What's to gain by only going halfway, then needing the angle? The angle is extra weight added anyway so it's a wash vs a little extra sheet alum.

The only thing I don't like is how to mate aluminum over fabric and I wrap the aluminum around the lower longeron and overlap the fabric. Screws would have to penetrate through fabric to get to the attach tabs I would add, unless I added those tabs outerward and vertically. Perhaps doing that, then edge rolling the panel to get it to tuck in nicely would work.

[Battson]

Since the skins only extend about halfway back, there's no obvious vertical tube to terminate the fabric. Page 43 of the quickbuild manual shows a piece of aluminum angle should be adel-clamped to the fuselage to provide this vertical fabric terminus. But, this is the only source for guidance on the task, and those photos are not that good.

Anyone have some better guidance? Pics?

I really dislike adel clamps for something that's a fixed point for fabric. I can weld tabs on, but I'd like to see some better detail of house others have accomplished this.

That method (adel clamp) is not good. The thing can move if you have a heavy landing, then your fabric goes slack.
I've been there, done that. Landed on a wad of tussock grass which was the size of a sheep, hooray for bushwheels.