wood-less PMF foamie can handle boys?

[iamroot]

If I build my trailer about 4 feet tall on the interior, do you think a pure 2" foam+canvas assembly can withstand two boisterous boys (<9yr) or is it going to break? What about just woodless walls+ceiling?

I plan to build with 2-3" radiused edges (for aerodynamics) and will gusset the interior of all edges with additional foam. I plan to use non-expanding foam adhesive. Thickness is TBD; ideally I can laminate two pieces of 1" foamular 250 for a total thickness of 2"; but getting 1" of foamular 250 may be too hard, then my next is 2 sheets of 1" foamular 150 or 2" of foamular 250, if the latter can do my gentle curves sufficiently. I don't think I'll bother putting thinner on just to save 2".

If the answer's "no" to above, I'm considering 1/2" CGF polyiso coverboard laminated to the inside of 1" foamular 150 for walls. I don't think anyone has used this for foamies before, so I don't think I can get feedback. Another thought would be laminating 5mm luan underlayment plywood to the interior only.

I'm also thinking of a hi-lo style (I've already found Teardrops & Tiny Travel Trailers w/ Lifting Roofs on 1st pg ), I'd reinforce the lower half with wood and the top half solely foam+PMF. I think that would be fine, but let me know if you think I'm wrong.

 

[Pmullen503]

Forget bending 2" foam without kerfing. You can bend 2 layers of 1" foam to a reasonable radius by kerfing both and glueing them kerfed sides together.

Check the thermal expansion coefficients before laminating dissimilar materials.

9 Y.O. boys? 1/4" steel plate should work.

 

[Tony Latham]

I think you mea

do you think a pure 2" foam+canvas assembly can withstand two boisterous boys?

I think you need to define what you mean by "boisterous". Roughhousing? Elbowing the walls? Jumping?

Tony

 

[iamroot]

Forget bending 2" foam without kerfing. You can bend 2 layers of 1" foam to a reasonable radius by kerfing both and glueing them kerfed sides together.

I should have qualified this: I'm only going for a couple inches over 8 feet. I don't have any 2" on hand, but not even as much as its own weight bends a 1" sheet over that length, so not preposterous (though with the cube law...)

Check the thermal expansion coefficients before laminating dissimilar materials.

Polystyrene is 10x higher CLTE, but 50F and over 4 feet it's a difference of 0.100". Given the flexibility of foam, I think it will be okay? SIPs are also bonded EPS to OSB and in wider temperature swings than I'll face here. I'm okay with some bowing. Appearance isn't critical.

9 Y.O. boys? 1/4" steel plate should work.

They're not 9 yet, but, yeah... I'm sitting here looking at some drywall that needs patching (but that's from picking/scraping and not concussive force).

I think you need to define what you mean by "boisterous". Roughhousing? Elbowing the walls? Jumping?

Sure, all those. I know an elbow to the walls will dent it, so I'm more worried about functional destruction. Imagine a boxy camper of solely luan plywood and small epoxy fillets, boys falling into the sides would blow out the corner (my friends expediently built a lightweight stitch&glue pirogue out of a single sheet of luan for 350 lbs combined weight, it mostly worked until it very suddenly didn't).

I'm hoping somebody's like "I fell hard against the side of my 1" pure-foam foamie and it was fine" or "I fell against the side and it split the seams to the roof" or "I backed my PMF no-wood foamie into something sticking out and the damage was only localized".

 

[Tony Latham]

Imagine a boxy camper of solely luan plywood

Someone once included this in a book about building teardrops:

'The box stores sell thin, generic plywood called luan (or lauan) produced in several Asian countries. The term typically refers to plywood that is 1/4” or, less commonly, 1/8” thick. Historically, it was made for interior door sheathing. It’s a mystery from one bunk to the next what the wood is, what glue was used, and how many internal voids it has. I can’t recommend such an unknown.'

Tony

 

[iamroot]

Someone once included this in a book about building teardrops:

'The box stores sell thin, generic plywood called luan (or lauan) produced in several Asian countries. The term typically refers to plywood that is 1/4” or, less commonly, 1/8” thick. Historically, it was made for interior door sheathing. It’s a mystery from one bunk to the next what the wood is, what glue was used, and how many internal voids it has. I can’t recommend such an unknown.'

I think you missed the context, which was using it as an example of something which would not hold up...

 

[dt400]

If I build my trailer about 4 feet tall on the interior, do you think a pure 2" foam+canvas assembly can withstand two boisterous boys (<9yr) or is it going to break? What about just woodless walls+ceiling?

I plan to build with 2-3" radiused edges (for aerodynamics) and will gusset the interior of all edges with additional foam. I plan to use non-expanding foam adhesive. Thickness is TBD; ideally I can laminate two pieces of 1" foamular 250 for a total thickness of 2"; but getting 1" of foamular 250 may be too hard, then my next is 2 sheets of 1" foamular 150 or 2" of foamular 250, if the latter can do my gentle curves sufficiently. I don't think I'll bother putting thinner on just to save 2".

If the answer's "no" to above, I'm considering 1/2" CGF polyiso coverboard laminated to the inside of 1" foamular 150 for walls. I don't think anyone has used this for foamies before, so I don't think I can get feedback. Another thought would be laminating 5mm luan underlayment plywood to the interior only.

I'm also thinking of a hi-lo style (I've already found Teardrops & Tiny Travel Trailers w/ Lifting Roofs on 1st pg ), I'd reinforce the lower half with wood and the top half solely foam+PMF. I think that would be fine, but let me know if you think I'm wrong.

Here's my$0.02.
I don't have any real world experience with a PMF foamie.
BUT wood glue is typically vinyl based (most but not all) and stays relatively flexible as does typical house paint. The foam itself will never really withstand a high point load without compressing and possibly having delamination.
There are paints of a much higher quality such as Alkyd or a good enamel that cure harder. Go to a Sherwinn WIlliams or such and talk to them about your project and expectations.

I am currently building a fiberglass foamie and my main concern is longevity. After several destructive tests I have decided that the typical 1 layer of 6 oz fabric was way way to delicate. I will have 2 layers of 12 oz fabric everywhere except the roof (3 layers) and inside on the floor (4 layers, mainly for high psi loads when kneeling).

One thing going for PMF is it's probably easier to work with and much cheaper than epoxy glass lol.

Darrell

 

[iamroot]

Forget bending 2" foam without kerfing. You can bend 2 layers of 1" foam to a reasonable radius by kerfing both and glueing them kerfed sides together.

I forgot I did have a sheet of 2". It did bend enough for my purposes. Unfortunately it's the kind with the cuts in it already, but I plan to fill those with the non-expanding polyurethane foam adhesive. Still would be ideal to get 1" of foamular 250 without cuts if possible.

Check the thermal expansion coefficients before laminating dissimilar materials.

Seems it worked out for OP827 just fine, but it's good to check.

 

[Pmullen503]

I should have qualified this: I'm only going for a couple inches over 8 feet. I don't have any 2" on hand, but not even as much as its own weight bends a 1" sheet over that length, so not preposterous (though with the cube law...)

If it's that small, 2" over 8 ft *might* work, especially if you weighed the foam board down into a curve over a few days before you actually try to glue it into place (pre bending). Two layers of 1" would almost certainly work without pre bending. Use epoxy or a polyurethane glue to laminate the layers of foam. TB or other water based glue would take weeks or months to fully cure.

Foam/PMF will dent but it's somewhat self healing over time. You can also steam out dents with a wet cloth and hot iron.

 

[iamroot]

I am currently building a fiberglass foamie and my main concern is longevity. After several destructive tests I have decided that the typical 1 layer of 6 oz fabric was way way to delicate. I will have 2 layers of 12 oz fabric everywhere except the roof (3 layers) and inside on the floor (4 layers, mainly for high psi loads when kneeling).

If you're going to spend the money on fiberglass, then you should spend money on a better core that complements the strength of FRP.

 

[dt400]

If you're going to spend the money on fiberglass, then you should spend money on a better core that complements the strength of FRP.

I agree but to get anything more dense was going to cost several thousand dollars because of the minimum order quantity. I am using the NGX 250. And had to drive 170 miles one way just to get the non-scored stuff.

Darrell