Teardrops n Tiny Travel Trailers

Has anyone done this? If so how did you reinforce the roof to wall joint?

I know once I get started doing this things can go fast so I would welcome any tips. I have searched some threads and not found exactly what I am thinking might work, which is, as the title says, canvas outside, none inside except maybe the roof and ends, and only 1/4" ply on the side walls, no canvas. Is that a mistake?
The plywood would help me hang or attach a lot of things and look good. Just not sure how to glue it to the foam best and help the roof/wall joint on the inside.

Right now I plan to use gorilla glue for the roof/wall joint, mask the plywood. A couple layers of TBII on the outside of the joint.

Here's my basic plan, it will be 90" tall, walls themselves will be 84" +/-

You could glue n screw some spars through the internal wall ply to give the wall floor joint some xtra strength.
KC has a similar serup on his foamie and i used 1/4 ply on the inside of mine but ive also got a minimal stick frame

Yes. I did this on my build. I used a variation of Steve Fredrick's method. The 1-1/2 inch thk foam wall cores were built with a 2x2 cedar sill and door frame surround, then I routed out pockets for 1x pine blocking everywhere a screw would need to go; cabinet face frame ends, bulkhead wall, light switch mounting plates, side mounted dome lights, coat hooks, pillow lights, etc. Those were all glued and weighted in place with GG, GS and sometimes TB2, depending on fit and my experimental mood; all were successful, and almost all of them needed work to clean up and fair.

The inner 5mm ply was laminated to the foam and vacuum bagged with a makeshift shop vac bag setup.

At the wall top I added some more pine blocks for the spars to screw down into, but first I glued all of the spars to the top of the ceiling skin and finished the underside of the ceiling before installing it. The ceiling was glued on top of the walls... IIRC I used PLP... and the spars were screwed down into the blocking. The joint line on the inside of the walls and ceiling is tight and I did not need any trim. Note that my cabinet face frames are a structural part of "The Box". They act like trusses and add to the rigidity of the wall tops. Also, the ceiling skin was glued and screwed all across the front and rear cabinet top rails. Then I infilled the space between spars with the roof foam. On the outside, I held the ceiling panel back from the outside face of the wall about 1/2 inch to help bury the plywood and keep it away from any possibility of moisture intrusion thru the edge. I "chinked" the gap between the top of the wall foam and the roof foam (the thickness of the ceiling ply) by cutting strips of foam and wedging them into the gap. I think I used TB2 for this, but it may have been PL300. Can't recall at the moment.

The profile of the roof was rounded over to a 3/4 inch radius and I am now in the process of preparing the cabin for a wrap in 2 plies of 6oz fiberglass cloth and epoxy. My original plan was to use PMF with cotton canvas, and I still think that would have worked very well. I just got to the point with my build where I had so much time and money invested, it just made sense to me to go all the way. Either way, the strength comes from the unity of the complete structure, which is all tied together with the outer skin, whether it is canvas and glue, or epoxy and FG. My cabin is as rigid as it could be; when I lift, push or pull on any part of it, nothing moves or everything moves as one single part. If I pick up on one corner there is absolutely no twist; and the outer skin isn't even on yet, and the cabin it isn't even mounted to the trailer yet.

Don't be afraid to experiment with the different glues and such. I have tried most of the commonly used ones throughout my build and they each have advantages and disadvantages in different situations.

Follow this advice and you can't screw up so badly that it won't work out in the end: (1) Design as a complete structure (each part does not need to hold the whole camper up, they all work together to be stronger than the individual parts). (2) Build light through out; the weight and the strength will add up and will both be there in the end when you need it. (3) Make tight accurate joints and glue well; sloppy joints are weak. (4) Seal out moisture from the weather, and make provisions for venting out moisture from the occupants.

Look into the "Stitch-and-Glue" boatbuilding method too [just google that term]
and adapt that to your build.

Just thinking , if you’re going to join ply to ply on the inside , what about a tab and slot setup to interlock the pieces together... just a little overlap and the foam and allowing easy alignment... Do we need a drawing ...

OK.. I think this would work great ... Strong , light , not to fiddly to cut out ...

Oops, my walls are 74" not 84" high.

Good ideas, thanks so much. I like the tabs idea! My time is really limited so I want to avoid any stick building. The walls and ceiling will be 2" foam and with some internal cabinet/bulkheads (not sure if that is the right term) attached to the floor firmly I'm counting on that to help with keeping things stout, at least on the middle of the length of the trailer. Maybe at the ends inside I could glue 1/4" ply to the walls to give it some racking strength.

mezmo wrote:Look into the "Stitch-and-Glue" boatbuilding method too [just google that term]
and adapt that to your build.

Yes, consider building the shell with ply in stich-and glue, with fiberglass tape and epoxy ply joints, then simply glue the foam , then fabric as an overlay. This will achieve the maximum strength of the unit, without the need for much stick framing (except maybe around equipment cutouts).

If you would rather decide to fit the ply into a foam shell, you can still achieve the strength benefit of the ply if you pay attention to the edge joints of the ply; in this case I would not suggest fiberglass tape and epoxy for the overhead joints. I'd rather suggest gluing wooden "internal chine logs" (see plywood boatbuilding books).
+++Woes to thems that attempt overhead epoxy-and-taping, it ain't no fun at all!+++

The extra complexity of stitching or tabbing is not required (IMO). It would add unnecessary complexity where none is required. The way I did it is very strong. You would need a sawsall or sledge hammer (or both) to get it to come apart... and I haven't even skinned the outside yet.

Agree. Either method of shell is adequate for strength. Both together are yet another avenue of overbuild.

Lots of choices for different tastes and thought processes ...

I use what I call "glue bolts" shown on the second page of my build thread viewtopic.php?f=55&t=64918 make a hole in the foam, I found the bit holder on my drill was best for drilling these, then pump the hole full of PLpremium, letting the gun push out as the hole fills.
Attach the plywood to the foam with a thin layer of PLpremium. Once cured the "bolts" are locked deep into the foam, and the ply is locked in place.

Link to Rowerwet's demonstration of PLP "bolts".

I like the bolts idea, thanks Row!

There are so many good ideas here. I don't want to get to fixed a complete plan (actually just part of a plan) mainly because I have built so many things in my life, often the plan changes along the way. I'm sure that hasn't happened to anyone here.

I still have one question in my mind that pertains to gluing canvas to foam. That is 'if my wall 11' x 6' is laying flat and I glue canvas to one side, will the wall cup or deform noticeably? '

I have read here somewhere that the canvas shrinks easily a couple of inches, is that as it is drying? That is a lot of shrinking and pulling on a rather flexible foam wall. Does it shrink for everybody? I have heard that canvas can vary so I thought I might order some from the Duck place, I forget the name in case that makes a difference. How about any of y'all using sheets or other natural fibers?