Teardrops n Tiny Travel Trailers

My TTT standie will have 6 foot tall walls. I'm going to put my first 4x8 sheet of 2" XPS on it's side (8' on the floor/ 4' standing). So on top of that there will be an additional 2' x8' piece. (like doing drywall sideways instead of vertical).
When I add the extra 2' top piece, I was thinking of inserting some wooden dowel rods vertically in between both of the wall sections for added support. The dowel rods would be inserted into the 2" edge portion of the wall pieces. Sort of like pegged together, along with GG.
Since I've never worked with Foam, not knowing the strength of a glued joint. Would this be a good thing to do ? or just a wasted effort that's not needed ?

All and only foam (with canvas) or foam between plywood skins?

No plywood skins. Just 2" XPS Foam, and 3(per side) vertical 2"x2" supports in notches of the foam walls. And canvas inside and out.

Certainly wooden dowels or any other means of grooving such as shown in my hot wire thread would increase strength. Is it needed? I would think that a canvas covered wall that is hit hard enough to separate the glue line, there is going to be a bigger issue than a failed glue line. Extra work, extra weight, extra complexity as far as I am concerned at least with wooden dowels. Now for long wall stretches with no interior supports, like cabinets, walls, ect. I would probably dado the edge and install a 1"x2" to add strength to the span.

rustytoolss wrote:My TTT standie will have 6 foot tall walls. I'm going to put my first 4x8 sheet of 2" XPS on it's side (8' on the floor/ 4' standing). So on top of that there will be an additional 2' x8' piece. (like doing drywall sideways instead of vertical).
When I add the extra 2' top piece, I was thinking of inserting some wooden dowel rods vertically in between both of the wall sections for added support. The dowel rods would be inserted into the 2" edge portion of the wall pieces. Sort of like pegged together, along with GG.
Since I've never worked with Foam, not knowing the strength of a glued joint. Would this be a good thing to do ? or just a wasted effort that's not needed ?

I initially tried to use dowels to hold my extended panels together, but finally gave it up because it seemed unnecessary. If you have long enough bar clamps to hold the panels together while they're drying, the wall will be very very stiff even before you cover it. Gorilla Glue is amazingly powerful stuff.

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I'm too much of a coward at the moment to build a foamie but were I faced with your question, I think I'd set up my table saw with the dado blades and put in a 3/4" spline of foam, all glued. DOesn't seem hard and seems pretty strong.

Biggest sheets I can find (maybe not available locally) are 4 x 9. Oh well.

I've always thought you foam-guys should consider using dowels on your butt joints. It'd be an easy task to glue and then drill and insert the dowels with glue after the joint is set.

I think this doweled butt joint is a good idea too. Is it needed? Don't all of us DIY-guys over build? Especially us tin-can guys?


Tony

I read somewhere here the use of chop sticks as pins to hold/strengthen the foam joints. It seems like they could be used like nails.

TT

We used chopsticks and bamboo skewers as “nails” to make assembly easier on Foamie #1 .. holds the foam pieces together till the glue dries ... And you don’t remove them , just cut them off flush before covering with a skin ...

GPW wrote:We used chopsticks and bamboo skewers as “nails” to make assembly easier on Foamie #1 .. holds the foam pieces together till the glue dries ... And you don’t remove them , just cut them off flush before covering with a skin ...

Bamboo skewers here. That and packing tape can be amazingly effective as a clamping system.

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Ditto the packing tape. Just use a not too thin of tape so it will peel off easily.

A quick way to glue panels together is position them on a flat floor and tape the joint on one side. Carefully flip it over and prop open the joint and apply the glue. I think I left the panels folded back since the tape n one side its like a hinge.

Anyway, once glue is applied lay down the panel (flat, taped side down) and tape the other side. Packing tape really holds it together, you can move the panels around like it is one piece, stand them up, whatever. I left mine flat and discovered it is best to put some clear plastic underneath the glue joints mostly so the glue doesn't ooze out and stick it to the floor.

My standee is 6'2" inside, horizontal joints like you are planning, and I have not noticed any weakness in the joined parts. You will want some kind of interior stiffening by way of cabinets or ledgers, doorframe or shelves, can be vertical or horizontal. I glued and attached all ledgers, cabinets and backs of cabinets with screw in zinc anchors (glued in w/G-glue). The anchor mostly just pulls things tight until your adhesive sets, I used a lot of adhesive caulking for that.

I used the tape hinge technique as well to good effect.

Usually I laid the panel on my bench and dragged the hinge line to the edge of the bench so the tape was backed up and didn't just peel off. One thing I did notice was that if I did not support the hinge line on a nice sharp bench corner, the tape would tend to pull away from the face of the panel some (my bench has chamfered edges, so depending on the panel one side or the other was not always pressed up against the edge of the bench.) This would allow the glue to ooze onto the face of the panel where the tape had lifted.

To solve this, I would tape the face of both panels separately next to the glue edge first, then butt them and put the hinge piece of tape on. That way if the hinge piece lifted and glue got underneath it would still be on a masked portion. It uses more tape, but protects the face.

I guess this was more important for my inner ply skins where I was trying to protect the wood for the finish to follow, but would also help on foam where sanding the harder glue line can be difficult to avoid the softer foam.

KCStudly wrote:I guess this was more important for my inner ply skins where I was trying to protect the wood for the finish to follow, but would also help on foam where sanding the harder glue line can be difficult to avoid the softer foam.

To help with a glue line like that I use a dremel with a small grinding stone. I grind the glue line below the foam surface just a bit. Then you can sand the foam without dealing with the harder glue line. Then once done I fill the glue line with light weight spackle.

I wish I had that tip long ago. I know I have heard it before, but we all have been doing this for a while now and I think that didn't come up until I was well along.

Good advice!

Curious thing about that light weight spackle .... When we recently removed the top canvas off the FS , the lightweight spackle came off with it ...