Folding Foamie Camper a la Casita or Esterel in the Works

[TinkerTailor]

Hi Postal Dave -

I looked at your design a while back. A very cool clamshell idea - nicely done! I'm planning on doing a pretty lightweight construction on the roof and using muscle power to set it up. In the vintage plans there is a photo sequence that shows how it will go. As some have mentioned, the height of my design might make it a little tough to do from the ground, but I plan to stand on the tongue for the higher side and also to make a notched dowel to push the roof up with (the plywood skirt will rest in the notch). I might also have straps on the front/back walls to pull them up more easily. Those are my thoughts as of now. Please weigh in if you have any advice!

What's your plan for lighter construction? Standard foamie approach?

[Postal_Dave]

If you click on and look at the 2nd picture from my build, you will see on the sides of the camper pieces of wood that look like a greater than and less than sign, > <. Then on the 3rd picture you will see them stretched out. The one on the right holds up the roof while I put up the walls, the one on the left holds up the galley door. You could try something like that to hold the roof up while you put up the walls.

As for how I'm making my next one lighter.. No plywood, less framing, and canvas covering the walls. I saw a PVC framed camper on this site. I can't find it now. I'm playing with the idea of framing foam panels in PVC pipe. I have to do some experiments first though.

[Postal_Dave]

I found the PVC camper. It's in the Hall of Fame named "PMF Over PVC".
https://www.icloud.com/sharedalbum/#B0WGrq0zw0Ucr43

[OP827]

Hi TinkerTailor, I have several points:
1. Roof needs to be prevented from undesired moving of its opposite end while lifting. There are several ways to achieve that: small retainers fixed on lower part, metal or nylon webbing geometrically tying wall and roof, or rollers in the wall top with channels in the roof.
2. I think it is good to have a small curvature in the roof to help water run off in storage mode. It looks like Gobur caravan has about 3" of curvature along the roof.
3. I would carefully consider what to use for lifting roof and wall materials. In this case cheaper might not translate into lower cost at the end. It is optimal materials which are lighter and more geometrically stable under temperature and load changes that will help a successful build. I am still looking for an optimal homemade light flat sandwich panels build method.

I enjoy constructive discussion and new ideas here. Please keep them coming.

Oleg

[TinkerTailor]

Postal Dave: I like that mechanism - very nifty. If it's a struggle to get my roof up, then I may well do something similar.

Oleg - good points on all counts. I plan to keep one end of the roof latched down on one side while raising it at the other. I will be storing the trailer inside, generally, but we could definitely hit bad weather in tow mode. Two thoughts occur to me: I could put a bit of bow into the spars I put on the roof, or I could leave an inch or two of slope in the roof when it's down.

My plans for the folding walls and roof are to have 1X timber frames, 2" XPS panels, and PMF, with some extra wood spars in the roof. Skirt will be 1/4" plywood. I will most likely use glass cloth and epoxy on the corners of the skirt, unless I think I need extra play/flexibility, in which case I'll fashion EPDM corner connections. I think the rubber corners are pretty unlikely, however. I know you used epoxy and glass cloth on your build.

What would your materials recommendations for those parts be?

Again, very nicely done on both of your builds. Definitely beyond the level of detail that I'll be able to muster!

[TinkerTailor]

Bit the bullet and paid to have all the foam and most other materials delivered on Wednesday, and I'll be going to hand pick the lumber early that morning, so construction of the floor and static wall assembly should commence shortly.

[OP827]

...
What would your materials recommendations for those parts be?
...

This is a really good question. If I would do it again, I want to come up with a system that has less sanding and body work. Ideally I want just a glue-up of lightweight finished surface panels and simple assembly with a nice looking trim, most likely not made of aluminium, but fiberglass or same material as panel siding so that there is less thermal expansion difference issues that with time may cause leaking. I do not really know what to recommend yet as I am still looking for solutions. When I find a good one I may build another folding trailer I now have in mind. One thing I do want to mention though: if you are going to build with plywood outside I would absolutely cover it with some fibers like glassed epoxy or PMF as you are planing. Plywood is not going to work under the weather without sound protection.

[TinkerTailor]

Oleg: I'll be interested to know what you decide to do in the future!

I got hold of most of my materials today. I already had HF canvas from when I got the trailer, and I selected the lumber in 6', 8', and 12' lengths this morning and then managed to rip it all down to a smidge under 2 inches to match the foam, which was delivered along with glue, screws, etc. I also managed to start on the frame for the floor.





I still have to put in horizontal crossmembers and make the cutouts for the wheels, as well as glue in the foam. Then I'll put the 1/4" ply floor over the top, though I plan to wait to put the polywall on the underside until after the PMF is wrapped under the bottom. Then the polywall will go on over that, with some kind of drip edge eventually placed along the sides at the bottom.

I'm planning to have the axle running across at 4'6" from the back of the camper (that would mean I'd have 1' of overhang off the back of the 4'X8' trailer frame and 2' over the tongue). My rough calculations would put this at between 40/60 and 35/65 of the weight behind/in front of the axle. I plan, at some point in the future, to make a tongue extension/reinforcement, though this will have to be bolted on, since I still want to be able to fold the trailer (the extension would have to be removed to do so, I think).

I put some hefty angle irons I had laying around in the corners to beef them up.



Update: got foam panels fitted in the floor framing.

[TinkerTailor]

Some more work completed since my last post:

1/4 inch ply added to the floor foam & framing/mix applied to all wood:



1X framing for the lower walls added:





Foam glued into the framing:







Next up trimming the glue, mix on the wall framing, spackle, mortises for the wall hinges, and then the PMF. Also have to get down to a metal supplier for some 2 inch square tubing for my tongue extension.

How many attachment points or bolts through the floor to the trailer would you all recommend?

[OP827]

You made a lot of progress, it's looking good!

For my build floor attachment to frame I went with similar idea as original tent trailer frame had. The floor was screwed down on perimeter and in a few places to cross beams with some self taping screws. I did a bit more than original trailer manufacturer did and put one 10-24 x 1-1/4" wafer self drilling screw every foot on perimeter and cross members. I pre-drilled slightly smaller holes to prevent the screws from snapping. I also put a good think bead of this polyurethane caulking on all steel frame to hold it all together and seal the gap as I do not plan to separate the floor and frame and want these pieces work together as one structure and do not rub from vibration against each other.

Your frame steel could be slightly thicker than mine and floor is thick since it is a sandwich, so you can go with lots of longer screws as I did, I would probably go with bigger screw size to avoid issues with self tapping or go with [elevator] bolts. My rule of thumb was to keep frame in full contact with the floor and caulking, not so much of concern of it separating as holding it down does not require a lot of attachment points, check minimalist frame here for some reference.



Oleg

[TinkerTailor]

Thanks for the guidance, Oleg!

I was not familiar with elevator bolts, but they will be perfect. Since I want to be able to take the structure on and off the trailer, the lower profile when compact carriage bolts will be better, since the boat heads will be above the flooring. Wonderful suggestion.

Over the last two days I built the boxes for the wheel wells. Pictures soon.

[TinkerTailor]

Here are the wheel wells. I boxed them out with XPS. On the interior of the cabin I will cover the sides with PMF in the top of the box with quarter inch ply. On the underside, I plan to cover the foam with NRP.

On the arches that I cut, I glued in some 1/8 inch poplar bending ply I have left over from surfboard construction.

[OP827]

What is NRP?

[TinkerTailor]

NRP is polywall, basically FRP without fiberglass strands. I’ll be putting sheets of NRP on the bottom of the floor. I was doing some sanding last night, and started to think, however, that using plywood inside the wheel wells might be easier since it would fill some small gaps satisfactorily.

[OP827]

Oh, NRP is a non-reinforced plastic, I see. I did my wheel wells out of 12mm Russian/Baltic birch plywood and covered it with several layers of epoxy 6oz fibreglass for mechanical protection and then with a spray of rubberised undercoating from a spray can for UV protection. They should hold against a tire blowout, most likely.

I was thinking that since you are planning on removing the trailer from the trailer frame, instead of elevator bolts it could be more convenient to tack weld hex nuts to the frame (or something similar) and use flat head [hex] screws through the floor from the inside. That would eliminate the need to crawl under the trailer ...