Foam questions re: framing

[knova]

Hello all,

In my efforts to potentially build a new travel trailer this year (family grew since I built my first one), I am exploring foamies due to their weight savings. I've been reading through the forums, and I have a general sense of what needs to happen to make the build successful, but I do have a few questions about framing out the foam:

1) Do I need a skeleton frame to outline the entire trailer? I've seen both - is there a consensus on what works "best"? It seems like it might be possible to just frame out hard points for windows, doors, and mountable items like lights / fans / vents.

2) How does one attach the foam to the wood frame, or the wood hard points? I've seen people say to 'embed' a piece of wood for something like a light, but is that just embedded into the foam and then secured with glue+canvas? What is to prevent that from coming undone? I know something like an interior light isn't very heavy, so maybe it's never an issue.

Thanks for any advice that can be shared. Once I commit to the insanity that is another build I will probably start up a build log, which is something I didn't do well last time.

[Pmullen503]

Hello all,
...........

1) Do I need a skeleton frame to outline the entire trailer? I've seen both - is there a consensus on what works "best"? It seems like it might be possible to just frame out hard points for windows, doors, and mountable items like lights / fans / vents.

Unless you are planning something much larger than a typical TD, a full frame isn't needed, just hard points.

2) How does one attach the foam to the wood frame, or the wood hard points? I've seen people say to 'embed' a piece of wood for something like a light, but is that just embedded into the foam and then secured with glue+canvas? What is to prevent that from coming undone? I know something like an interior light isn't very heavy, so maybe it's never an issue.

For just a hard point, I used a router to cut a depression for your plywood so it sits flush with the foam and glue it in. On a door or window, a perimeter frame.

Be aware that over time due to differential expansion, the line will telegraph through the canvas. So design the shape and size(and any graphics or paint scheme)to make it less objectionable.

[knova]

Thanks for that reply PMullen. I'm still hemming and hawing over the size. Might try to go 6' wide to accommodate more sleeping area, but I am worried about the increased drag. My tow vehicle isn't great so I need to keep the weight low and aerodynamics high. In my brain right now, 6x9 or 6x10 sounds feasible and would provide everything I want, but those concerns are at the forefront. 5x9 might be more realistic, but then I'd have to figure out a way to cram more sleeping area in for the kids - maybe some kind of bunk situation. I do know that I'm skipping the galley - the wife and I prefer to just cook outside/away from the trailer, so that simplifies things!

[Pmullen503]

If you go 6' wide, and the roof is curved, you should be fine. With a square drop with a flat roof, I'd be tempted to put a wood rafter or two to make sure it doesn't sag so water doesn't pool it that section.

[pchast]

I feel I could have used less framing.
Things have held up well so far.

[knova]

If you go 6' wide, and the roof is curved, you should be fine. With a square drop with a flat roof, I'd be tempted to put a wood rafter or two to make sure it doesn't sag so water doesn't pool it that section.

it truly all depends on what my wife will allow me to keep in the garage. I have a 5x8 currently and it stores nicely in our extra wide 2 car garage. A 6ft wide will mean we lose one of the bays full time, which I can live with. But I only have 50% vote in this.

[knova]

1 more question - how are you guys filling seams between foam pieces? I figure those would be visible through the canvas

[OP827]

1 more question - how are you guys filling seams between foam pieces? I figure those would be visible through the canvas

I used PL Premium glue, Epoxy, Great Stuff to glue xps foam to foam or TB2 for foam to wood. They all seem to work.
I had Great Stuff foam caused bubbles under a finished skin many weeks after it appeared to be cured, so I would avoid it for surface repair purposes because of that.
Seams may be visible if covered by canvas only. I tried to fit the pieces the best I can and then, once glued, sand the surface to make the seams less visible.