PMF experiment

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PMF experiment

Postby sockdoc » Wed Nov 10, 2021 10:57 am

I am starting the process of building a teardrop (in the next few years). In the interim I want to build a pull out kitchen that will go on the front of my gear hauler (the eventual trailer for the future teardrop). I want to use the pull out kitchen as an experiment with different building processes. As one of the first steps I will need to build a waterproof box approx 18"Wx44"Lx23"H. I want to experiment with foam, plywood, fiberglass/epoxy and PMF. Here are my thoughts and appreciate feedback.

Base and 2" railing/skirt around the side will be 1/2 plywood with the underside coated with bedliner. On top of the railing/skirt (needed to affix heavy duty sliders) will be the 1/2" foam board (pink stuff). I plan on using PMF on the inside to give structural integrity (apply this to the panels before joining and then adding reinforcement at the joints). Rather than using bedsheets/canvas I was looking at using window screen material with titebond II, followed by a coat of paint. For the exterior my plan was to use fiberglass (likely 6oz) with epoxy, coating that with bedliner.

Anyone used window screen material in place of the canvas? (I will do a few test strips before fully going this route If I proceed in this direction). My thought would be to compare PMF with window screen with the fiberglass for durability and lasting adhesion (obviously not apples to apples comparison since one will be interior the other exterior). Am I overthinking and should just use canvas instead (I just like the idea of tinkering with something new!)

WIll PMF in the inside and fiberglass on the epoxy outside give enough structural integrity to the foam board as to not collapse. I obviously don't plan on using it for standing on but likely a water jug will sit on it at some point. Thanks for any thoughts, encouragements, and redirections =)
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Re: PMF experiment

Postby twisted lines » Wed Nov 10, 2021 3:51 pm

I have played with some scraps and have a simmular plan using foam :lol:
1/2" pink is like 3/4" (Another) Wish in in my area.
The White snow balls are; I think I can get 4' Blocks of that. :NC
My lifting ability is long gone so Light, Transferable, Removable, & more still :thinking:
Foam with 1/8 ply both side's; may fake the ends

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Re: PMF experiment

Postby RJ Howell » Thu Nov 11, 2021 7:55 am

I did a test using fiberglass tape thinking this would be an easy system for joining. I wasn't happy with the results and Figure it's do to the spacing of the weave, much like screen would have. To me, density & thickness are key to PMF and to quite some point FG as well.

I've done canvas, duck-cloth and bed sheet with PMF. Canvas for me was the strongest, duck-cloth 2nd then bedsheet. Bedsheet was the smoothest and ended up using it as the interior.
On edge, tinsel strength, you'll find XPS foam to be very good! One my 1st build (truck cap) I bend (stressed) the foam to increase this on he sides and roof. Worked very well and gave it a unique look! Roof span on that one was only 4ft so not much deflection (~1/4"). My current build I'm one 6ft roof span and requires support. Both handles a snow load, me leaning over/on to reach a spot, yet no standing on either.. I use 1.5" xps on both. truck cap was bedsheet interior/canvas exterior, Truck camper is bedsheet interior FG exterior. Both systems of exterior are equal in my mind and cost me about the same (PMF being a slight bit cheaper).

Hope some of this helps. Enjoy the build and the rewards once done! :beer:
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Re: PMF experiment

Postby Pmullen503 » Thu Nov 11, 2021 11:24 am

Someone here used window screen with mastic and that worked. Not so sure about screen with glue or paint.

I guess I'd do some tests with various systems and see. The thicker the foam, the stiffer you box will be. If I had to guess, 1/2" might be marginal depending on the load but it might be enough too.

If there is any wood framing involved, I would go with epoxy and glass cloth as the most waterproof.
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Re: PMF experiment

Postby sockdoc » Thu Nov 11, 2021 3:12 pm

That’s really helpful. As I think about using window screen it may not be the best use. The interior PMF really is to add stability to the foam. I could just add plywood on the interior instead and probably save a lot of mucking around with glue and canvas in a small enclosed space that nobody will ever really see.

The more I price out fiberglass vs PMF the cost difference really isn’t worth it for the added reassurance that fiberglass brings.

Any value in plywood + fiberglass + Berliner vs skipping the fiberglass all together if just going with plywood construction?
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Re: PMF experiment

Postby Pmullen503 » Thu Nov 11, 2021 6:05 pm

Wood rots unless you can keep it from staying wet for any length of time or it's encapsulated. It also expands and contracts with changes in humidity. That makes the joints move and any non reinforced coating gets cracks and can let moisture in. If it was mine, I'd spent the money on glass and epoxy now so I wouldn't have to fix it in the future if I used plywood.

PMF works over foam because even though latex paint is moisture permeable, the foam doesn't expand and contract like wood does. And doesn't rot.

I've got 30 year old cedar strip boats (epoxy/glass) that are as sound as the day they were made. But the wood trim needs to be revarnished every 3 to 5 years.
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Re: PMF experiment

Postby JasenC » Thu Nov 11, 2021 8:35 pm

Just out of curiosity, have you thought about screen and one of the thicker bedliners like Huculiner, Raptor liner.
I'll be done when I'm finished, if that's not fast enough, take a number.

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Re: PMF experiment

Postby sockdoc » Fri Nov 12, 2021 11:16 am

JasenC wrote:Just out of curiosity, have you thought about screen and one of the thicker bedliners like Huculiner, Raptor liner.


Umm not until now! You thinking impregnating the screen with the huculiner?
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Re: PMF experiment

Postby twisted lines » Fri Nov 12, 2021 3:17 pm

I'm kinda building something like this and planning #2 with a lot more foam :twisted:
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Re: PMF experiment

Postby JasenC » Fri Nov 12, 2021 10:16 pm

sockdoc wrote:
JasenC wrote:Just out of curiosity, have you thought about screen and one of the thicker bedliners like Huculiner, Raptor liner.


Umm not until now! You thinking impregnating the screen with the huculiner?


That is exactly what I'm thinking.

You would need to stretch the mesh tight and maybe use some crown staples where needed to keep it against the panel.
I'll be done when I'm finished, if that's not fast enough, take a number.

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