Re-Engineering Skin/Belly/Frame/Floor Connection

[skyclad]

how can the connection between the shell-skin, the belly-skin, the floor, and the frame be redesigned so these are all de-coupled?

ideally a re-engineered solution would allow:

1. removal/replacement/repair of dented belly-skins and banana peels without having to remove the interior skin and all the buck rivets around the waste-line.
2. removal/replacement/repair of sub-floor without wedging it into the gap between the c-channel and the frame
3. removal/replacement/repair of external shell skins without affecting the belly skin
4. anything else?

i have some ideas, which i will share, but for now i just wanted to get this thread started and start the conversation.


btw, i've heard rumors of this topic being addressed on the forum but haven't been able to find a dedicated thread yet. apologies if i'm duplicating information! (links to existing posts would be much appreciated)

[rugjenkins]

Look at headroom epiphany- darkspeeds thread. Good stuff.

[skyclad]

Thanks for the tip. Can you clarify how you guys attached the belly skin w/out trapping it under the exterior skin?

[rugjenkins]

Most belly pans overlap on the shell right at the floor connection (no wonder they rot). I jacked mine up 3 inches and plan to underlap and rivet them in. The center pan will be screwed into the main frame rails. The part that is riveted to the skin is 2 ft wide and will wrap to the main rail.
Here is a pic of how I reengineered the floor and shell connection. It's 1.5 square stock welded to the edge of the outriggers. The floor can be removed/replaced without lifting shell again. Hope this helps

[skyclad]

Awesome thanks for the pics. So you're not trying to decouple the exterior and belly skin? (My ideal arrangement would allow the belly pan to be removed without messing w buck rivets not exterior skin)

[Belegedhel]

You could always modify the belly skin connection the way it is done in the 70's vintage trailers, in which the shell is bucked to the C-channels, which are bolted to the floor/frame, and then the edges of the bellypan are brought up to overlap the shell by about 3/4" and pop riveted in place. There is then a piece of beltline trim that is installed over the juncture in order to hide all the ugly.

The obvious shortcoming of this setup is that every pop rivet you put in there is another opportunity for a leak, and with the bellypan overlapping and looking up, it will likely funnel water into the bellypan. Judicious amount of vulkem might help get things sealed up.

On a more radical line of reasoning, why not eliminate the undereath part of the bellypan so that only the banana wraps and other visible curved side parts are there. That would give you complete access to the frame and tanks underneath, and if a wrap gets damaged, it is just some pop rivets to correct it. I'm sure someone will opine that the belly skin is a structural component, but as long as you are re-engineering, don't let existing paradigms slow you down!

There was also another thread that discussed pretty much this same topic. I think the conclusion that one came to was that by building a metal frame around (and on top of) the perimeter of the existing frame, and then bolting the shell on top of that, you could eliminate the plywood trapped under the walls. The floor would then be installed completely on the interior. I don't know how to tell you to even search for that thread, though.

Having done a shell-off, and completely replaced my bellypan once, I have no interest in doing it a second time (ever)--even if I had devised an easier means of doing it. Therefore I focused more on keeping water out and rendering my floor rot-resistant than trying to make up for the shortcomings in the original design.

good luck!

[skyclad]

ok so here are some rough sketches of what i have gathered so far...

first pic- Airstream's original connection

second pic- darkspeed/rugjenkins solution (as i understand it):
weld a 1.5" steel tube to the frame all along the perimeter. this decouples the floor from the the other connections but the banana and exterior skin are still buck riveted together.

third pic- my proposed solution v1.0
as you'll see this relies on the creation of a custom connection profile. the end result allows the floor, belly pan, and exterior skin to each be removed without affecting the other components.

fourth pic- how i imagine assembling my proposed solution.


i'd love to hear any thoughts you guys might have.

[truckasaurus]

Awesome drawings but I'm not sure how it will work in the corners.. You could just make the perimeter belly pan from light gauge steel and weld it all the way around it might be easier.

[Belegedhel]

I like your design for the custom extrusion that will act as the "C" channel and support the floor at the edges--It would be hard to execute in the curves of the corners, but there are solutions.

Similarly, getting your banana wraps (on the corners) to wrap and to extend up under the wall like on the straight sections would be a challenge.

As I look at your design, it looks like there are blind rivets in a vertical position connecting the "C" channel of the wall to the frame. So the only thing holding your shell to your frame will be some (a bunch) of blind rivets in axial tension? Are there any bolts involved?

[skyclad]

Yes the curves at the corners need to looked at more closely. In terms of connection to the frame I propose bolting the new profile to the outriggers (see step 2 in the last image)

[Belegedhel]

So, in step 2, I see that you are bolting the extrusion to the ends of the outriggers, which I would expect will close up the space. How do you insert the belly-wrap then in step 3?

[skyclad]

Originally Posted by Belegedhel

So, in step 2, I see that you are bolting the extrusion to the ends of the outriggers, which I would expect will close up the space. How do you insert the belly-wrap then in step 3?

good question! that's the key point of the design...

not sure i can illustrate it better, but the new banana skin will only be riveted to the bottom of the new profile between the outriggers. the banana skin pieces will be notched around the outrigger connections so they can slip in between the outriggers after the new profile has been bolted down. does that make sense?

i'll see if i can draw something up to make this clearer...

[Belegedhel]

Ok, I see what you have in mind.

[skyclad]

btw, i don't mean to get off-topic, but while we're talking about structure... around the ceiling curve there seem to be several ribs running fore-aft that are not riveted to the exterior skin (pictured below). do you know what those are for? seems like the interior skin makes them redundant. can they be removed and discarded?

[Atomic_13]

Neat thread and ideas... I have two questions:

1) What prevents water from following the blue line? The factory extended the banana wraps along the inside of the outer skin as a flashing (red line).

2) This would require you extend your banana wraps by one vertical inch and one horizontal inch (so going from 5" to 7"). I've yet to come up with an easy solution to make custom corner banana wraps that are higher than stock. Any ideas?

[skyclad]

another good question. the water path you point out is my main concern with the design. i'm hoping that a good sealant would do the trick if placed between the new banana skin and the new profile. for good measure i'd also consider caulking the seam at the bottom of the exterior skin.

i should also note that i plan to replace my subfloor with something like CoosaBoard which doesn't rot, but a good redesign wouldn't depend on fancy materials like that.

in terms of the new wraps, i'll see if i can illustrate my idea better. i think i have a solution that uses well tailored sheet stock with rivets.

[Belegedhel]

Originally Posted by skyclad

btw, i don't mean to get off-topic, but while we're talking about structure... around the ceiling curve there seem to be several ribs running fore-aft that are not riveted to the exterior skin (pictured below). do you know what those are for? seems like the interior skin makes them redundant. can they be removed and discarded?

I had some like this in my trailer as well. They appear to be there just to help maintain the separation of the interior and exterior skins, and probably also to firm up the interior in places where you have a large panel that otherwise will get wavy looking without something to firm it up. I left them where they were.

[skyclad]

Originally Posted by Belegedhel

I had some like this in my trailer as well. They appear to be there just to help maintain the separation of the interior and exterior skins, and probably also to firm up the interior in places where you have a large panel that otherwise will get wavy looking without something to firm it up. I left them where they were.

ok thanks! i was thinking maybe they were just there to hold the insulation and wiring in while the interior skins went on.

[skyclad]

Making progress on the re-engineered connection....

Spacers welded to each outrigger:

New stretched outriggers compared to old outrigger:

[cephalobot]

Looking good!