Teardrops n Tiny Travel Trailers

Hi All

I am thinking to build a pure foamie (no wood skeleton, no wood floor) with fiberglass around corner and base as structural componets.

Specific question:
1, I saw a 4x8 box shape trailer using PMF only no wood and springer at all, it seems hold fine, that certainly less strong as 1708 fbgls all around.
For my planned tear-shape 5(w)x8(l)x4(h) body how heavy is the fiberglass cloth needed hold the trailer stable and safe at highway speed.
Or another way to ask the question is how much fbgls weight is equivalent to an average PMF system.

2, I probably want to go 1" wall and 2" roof, 1" floor, all surface assume to be 1708 fbgls covered, and I figure 20 yrd x 4' cloth needed, and I calculated about 7 gal epoxy kit needed.
That's like C$800 in Canada. 7 x gal west system kit, just for the epoxy.
I am wonder I probably either over calculate the require epoxy or the cloth weigh, related to question #1 What is typical $ you spend?

3, is the thickness of foam matter? Foam offer no tensile or shear strength, but a lot of compression strength. Is the thickness matter? I want to reserve space within the 5x8 trailer, but understand thick foam wall separate two layer of structure unit apart help to leverage strength.

4, any magic to mix use PMF on interior and average thick fbgls on surface and very thick 1708 only at corner and edge.
That require a lot of work to plan and sand and smooth down the road, not sure if it worth it than just over build it.

Thx

I have tested and found that 2 plies of 6oz weave and epoxy equals the same weight as canvas and glue. This does not I clude anything to fill the divots in the weave, sealer or paint.

2 plies gave me the puncture resistance I desired.

Why nobody use tite bond and fiberglass cloth? Fiberglass cloth is definitely stronger and no uv degrade

Why nobody use tite bond and fiberglass cloth?

Because it is nothing like epoxy.



Tony

napoleonbot wrote:Specific question:

2, I probably want to go 1" wall and 2" roof, 1" floor, all surface assume to be 1708 fbgls covered, and I figure 20 yrd x 4' cloth needed,

Built as a S.I.P. panels then assembling the panels I figure your 1" could be fine. I used 1.5" on my walls on my first build. The roof I found anything over 4ft wide really wants some structure. My 1.0 truck camper build I went 6'-4" span and had to place angle under it because it bowed. That was also 1.5" yet do expect the same with 2".

3, is the thickness of foam matter? Foam offer no tensile or shear strength, but a lot of compression strength. Is the thickness matter? I want to reserve space within the 5x8 trailer, but understand thick foam wall separate two layer of structure unit apart help to leverage strength.

I've tried the layer system without getting much additional strength. Maybe others have had better success.. On my first build I tested the XPS alone, with a face FG'ed, then both faces FG'ed. Yes both faces won out! I also force bent the roof and curve bent the sides to add strength. It helped but more of a PITA for what it was worth. Will say it looked cool.

4, any magic to mix use PMF on interior and average thick fbgls on surface and very thick 1708 only at corner and edge.
That require a lot of work to plan and sand and smooth down the road, not sure if it worth it than just over build it.

Short answer, No. I've built PMF and FG, I use FG/resin primarily now. I never found PMF to have the strength I wanted to see.

Thx

All of this is my opinion from my experiences in building. I see no end to the possibilities of building with XPS and FG if done as a SIP panel (fully enclosed). Testing I've done as such have far exceeded what I had hoped to see. With that said, I didn't like it as a floor.. and since I now build truck camper style I haven't worked out a supportive cantilevered loft with adding some sort of structure. It's that floor again!
You also need to think about some sort of blocking at windows, vents, hatches & door. Having wood involved doesn't have to be a bad thing, if sealed well!

Look forward to hearing more of your build plans

tony.latham
Because it is nothing like epoxy.

Thanks for posting your reply.
I understand wood glue is different than epoxy, honesty PMF, as the name says, is there only because of high cost of epoxy. - Like I estimate full foam build need 800$+ epoxy.
So I ask my question, maybe silly one, why not switch canvas to fiberglass cloth. Is there any issue for tite bond to bond fiberglass cloth?

RJ Howell
Short answer, No. I've built PMF and FG, I use FG/resin primarily now. I never found PMF to have the strength I wanted to see.

I am worry about both strength and UV degradation of cotton fiber.
The canvas cloth is by no mean best material, it soak in moisture, it breakdown under sunshine, and brittle with age.
I admit lack of experience making PMF build, though, but still quite suspicious on the long time performance of PMF.

Canvas and paint holds up well and has been used for hundreds of years on ships. The paint saturates the canvas fibers making them waterproof and UV resistant. My 11 year old foamy shows no signs of deterioration.

Glues and paints don't bond well with glass. Use epoxy with glass cloth. BTW https://www.uscomposites.com/ has lower cost epoxy. I've used it and it's good. Around $75/gallon for resin + hardener.

That said, epoxy and fiberglass have advantages and do better if you have a leak or just a design that allows water to pool. PMF is cheaper but you do need to make sure you don't have standing water on it, especially if you use latex paint.