foamie x vintage tin cross?

[Ranestorm]

So I've been reading and absorbing as fast as I can and while the idea of a Foamie is new to me I can see it's an excellent way of creating a teardrop (and many other things). But I'm not working on a teardrop.

I have a 1972 scotty that I purchased partially rebuilt. The previous owner stripped it down to frame and built a new floor and studded it out in aluminum so it's super light. He skinned it in hardboard and there it sat for 5 years waiting for me to find it

So, I'm in the process of taking the hardboard off and raising the entire frame up 12 inches so a normal sized person can stand inside. (are you wondering why I posted this in the foamie section yet??)

So, here's my question. I want to put foam on the outside of the aluminum studs like a normal trailer and then canvas(and glue) the foam like a regular foamie. But..here's where I'm getting stuck - after I do that I want to put the original aluminum skin back on the outside of the camper, but not sure how to be able to do this and attach it properly. Would I skin it in canvas and let it dry and then run a small rib (maybe 1/2 x 2) of wood screwed through the foam into the aluminum frame so I have a place to screw the original skin to? I can't really wrap my mind around this particular part and the vast internets have been no help with an idea like this.

Why do I want to do it this way? Because here's my thinking on re-skinning it the traditional way. so I skin the outside at say $35-40 a sheet for 1/2" ply (haven't been able to find it cheaper), then insulation at $20 a sheet. Seems to me if I use the 'foamie method' i'm saving myself $35-40 a sheet (and that doesn't even count the weight savings there). Also, I'm really drawn to the waterproofness Down here where I live it can be a desert or it can be a rainforest. Sometimes both in the same day. Help me out here - what are your thoughts?

[KCStudly]

Foam, canvas, glue and paint aren't free. Also, not sure your price estimate on 1/2 ply is current. So your cost comparison is far off. There is plenty of labor in PMF, as well that can be as much or more than ply.

Canvas needs a bit of a radius to wrap over an edge, whereas aluminum skin likes to run up to an edge and be capped with trim molding.

Can you describe the aluminum framing better? Is it Z-bends or channel formed from sheet? Thickness and depth of section? Will the studs be exposed on the inside? If not what will the inside skin be?

If you plan to have a thin ply inner skin, like 1/8 inch laid over the foam, I'd do the same on the outside with a frame of wood hard edging; fiberglass/epoxy reinforce the corners; neat epoxy (or "the mix") everything; then aluminum skin taking extra care to seal every screw hole.

[Ranestorm]

Labor is free (it's me doing the work) so I don't mind. so 1/2" ply is $39/sheet today at my local big box store. Foam (1" thick) is $20/sheet. The cost of canvas is negligible at this point. I have some here already from previous projects and can pick up the remainder of what I need.

So the frame is made from a C channel aluminum. I haven't ever built anything from aluminum like that but it's very well done and sturdy. It's about 1 1/2" studs (c channel)

I am planning to skin the inside with 1/8" ply or something along those lines. This trailer will become a beverage trailer when it's done - it won't be a sleeping quarters, but basically a mini kitchen on wheels without a stove. I am looking for it to be insulated well against the heat down here.

So if I didn't 'skin' it in foam, but just put the foam in between the studs and then coated them in glue/canvas then attached the thin ply to the outside then the aluminum skin to that it might work better according to your reply. I'm attaching a pic of the scotty in it's current state now.

20220618_091541.jpg (632.36 KiB) Viewed 422 times

[Pmullen503]

Skinning the outside with foam may change the dimensions enough so the old skin wouldn't fit.

I'd go with foam between the studs and a thinner ply skin; 1/8 or 1/4" and 1/8 ply or paneling inside.

[KCStudly]

That looks like galvanized steel stud to me. Try a magnet on it.

I guess if you are scraping it all anyway to go taller you could pretty much start over anyway you please.

The thing is, with aluminum skin you need hard edges around the perimeter to fasten at least the trim into (the aluminum can be glued or VHB taped in place long enough to get the trim and other fittings in place... doors, windows, etc). And you don't want moisture getting under the aluminum or trim, regardless of how the inner wall is built; so using PMF under the aluminum seems like extra material, labor and cost to me.

See how your existing ply is buckled even though it is relatively thick material? Don't count on foam being perfectly flat either, but it will be better than that. I am struggling to get epoxy/FG layup to be flat enough for finish paint, so I can imagine how unflat PMF might be, and getting aluminum to lay flat and bond well to an uneven surface seems like a chance for water to get in. In hind sight I sometimes wish I had clad my foam with thin ply before doing the glass layup (in your case aluminum skinning) because I think it would have been easier getting a more fair surface.

But maybe that's not as important to you. If you are going to operate a business and want signage on the sides to look professional, you probably need a pretty flat and fair surface. Just $0.02.

[Ranestorm]

Skinning the outside with foam may change the dimensions enough so the old skin wouldn't fit.

I'd go with foam between the studs and a thinner ply skin; 1/8 or 1/4" and 1/8 ply or paneling inside.

so he didn't keep the original skin (i have NO IDEA why not) but i do have a TON of leftover skin from another camper that was bigger than this one - still vintage so it keeps with the 'look' of the whole thing. Lots of holes to patch and a giant puzzle to put together but it will work out (i hope) with moving windows etc so adding width isn't really an issue at this point.

[Ranestorm]

That looks like galvanized steel stud to me. Try a magnet on it.

I guess if you are scraping it all anyway to go taller you could pretty much start over anyway you please.

I'll check it out and report back. I have zero plans to scrap it all - my idea is to unscrew the existing frame from the floor and give it a 12" lift (working on the how for that still) then reattach it. should be interesting at least.

The thing is, with aluminum skin you need hard edges around the perimeter to fasten at least the trim into (the aluminum can be glued or VHB taped in place long enough to get the trim and other fittings in place... doors, windows, etc). And you don't want moisture getting under the aluminum or trim, regardless of how the inner wall is built; so using PMF under the aluminum seems like extra material, labor and cost to me.

my thoughts on doing it this way were two fold - 1) it's cheaper - i have to use foam regardless for insulation so if i can create a waterproof exterior using the foam and just attach the skin to it (somehow) and adding the j-rail along the edge then i can maintain that 'vintage look'. 2) i really want it to be watertight. i don't want to have to pull this thing apart in a couple years to waterproof it and kick myself all the way to the curb because i knew a way to make sure it would be from the get go.

See how your existing ply is buckled even though it is relatively thick material? Don't count on foam being perfectly flat either, but it will be better than that. I am struggling to get epoxy/FG layup to be flat enough for finish paint, so I can imagine how unflat PMF might be, and getting aluminum to lay flat and bond well to an uneven surface seems like a chance for water to get in. In hind sight I sometimes wish I had clad my foam with thin ply before doing the glass layup (in your case aluminum skinning) because I think it would have been easier getting a more fair surface.

the 'ply' that's on there is actually 1/8" eucaboard, and it's 6 years old, with no waterproofing of any kind. it was mostly kept in a garage/shed, but i can tell by looking at it that some rain did get on it a couple of times. i believe when he did it originally it was smooth and flat.

But maybe that's not as important to you. If you are going to operate a business and want signage on the sides to look professional, you probably need a pretty flat and fair surface. Just $0.02.

i have given some thought to signage, but i was thinking it would be cool to have a 3D sign of some kind - maybe even cut out of foam and then painted so it isn't like a flat vinyl sticker.


still trying to plan all this out in my head is pretty interesting to say the least. especially since it seems i'm wanting to do something that hasn't been done before and might be just a tiny bit crazy.