PMF and foam

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PMF and foam

Postby badgerkeeb » Sat Feb 03, 2018 6:44 pm

I'm getting ready to build me a teardrop out of foam and skin it with PMF. I have found videos about pmf on plywood and it looks like a pretty solid surface. I have also found videos on using fiberglass on foam. But I cannot seem to find any videos the tell me what kind of surface I should expect using PMF on foam.
I did an experiment applying PMF on a small piece of foam. I believe I did it correctly as when the glue dried the canvas was hard enough to sand smooth. I haven't used any paint on it yet because I want to make sure I haven't done something wrong. My question is. How solid should the surface be on the foam after the glue dries?
Can someone please enlighten me on this?
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Re: PMF and foam

Postby ghcoe » Sun Feb 04, 2018 11:59 am

Not sure what you are asking. Texture, strength or both?

Texture depends on a lot of things as does strength such as cloth weight, layers of cloth and or glue/paint coatings.

In my builds I have diluted the TBII 50/50 and applied to both the foam and 10oz. canvas in the skin glue up. I apply full strength TBII at the corner overlaps. Then I apply a coat of primer with two coats of latex paint. Texture has a nice canvas patterned look and strength is good enough for me to push on the trailer with my finger tips and cause the trailer to rock without fear of dimples. I have caused dimples with my elbows working on the roof, but a day in the sun usually takes them out.

Hope that helps. Good luck, George
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Re: PMF and foam

Postby badgerkeeb » Sun Feb 04, 2018 3:43 pm

Thank you for your reply. That is exactly what I needed to know.

When I did my test piece I used straight TB II then laid out the 8 oz. canvas and went over it with more TB II. When it dried I was able to sand down the high spots. I guess I was expecting some kind of hard shell like finish.

I have been looking into using STYROPLAST from Hotwire Foam Factory as a final coat for the outside. From what I've seen. It looks promising.
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Re: PMF and foam

Postby badgerkeeb » Sun Feb 04, 2018 3:51 pm

BTW George, loved the thread you posted on using flashing in your build. I plan to use some of those techniques myself.
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Re: PMF and foam

Postby ghcoe » Sun Feb 04, 2018 5:32 pm

Thanks!

As far as a hard shell I don't really know if you need it. I have owned aluminum and metal sided travel trailers and I can push harder on the sides of the foamie than I would dare on those metal sided trailers. The nice thing about a foamie is that if you do scrape against something it will usually push back out with time. A hard shell once cracked is in need of repair.
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Working with flashing for foamie construction viewtopic.php?f=55&t=60303
Making a hot wire http://tnttt.com/viewtopic.php?f=55&t=55323
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Re: PMF and foam

Postby GPW » Mon Feb 05, 2018 5:36 am

" I guess I was expecting some kind of hard shell like finish. “

Everybody at first expects this , But the canvas finish is actually really nice and holds up Great ( mine has lived outside , no cover for 4 years now :thumbsup: ) … Just a wash now and then , and like George said , any dents go away in the Sun… “self-healing"… ;)
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Re: PMF and foam

Postby John61CT » Mon Feb 05, 2018 10:11 am

But is there a coating thick enough that eliminates the weave showing through?

Or has anyone used the stuctural foam + PMF for strength and primary waterproofing, and then skinned the outside with something more mainstream?
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Re: PMF and foam

Postby badgerkeeb » Mon Feb 05, 2018 2:10 pm

That's the reason I'm looking into Hot Wire Foam Factory's Styroplast. https://hotwirefoamfactory.com/ I have seen videos of this stuff and it looks promising.
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Re: PMF and foam

Postby GPW » Tue Feb 06, 2018 6:43 am

"But is there a coating thick enough that eliminates the weave showing through? “ That question again … NO !!!! The weave is all Part of it … It’s a “SYSTEM” that has proven to work , repairs itself ,and is inexpensive and easy to do … ( read the Big thread to understand the LOGIC )

If you want a mirror smooth finish , I’d suggest looking elsewhere … You won’t be happy here … :roll:
Just trying to be Honest here … A real Foamie is more a “Hard tent” … Easy to make , Cheap, Durable , self healing , pragmatic … but not the Prom Queen eh … :R :lol:
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Re: PMF and foam

Postby Nodrog » Tue Feb 06, 2018 12:37 pm

Hi again, folks! I haven't posted anything for a while, been goofing around with my trailer, though. If you would like to look at my build thread "A Foam Project" (it's here in Foamies) I am using mastic over 2 layers of window screen to achieve a very smooth exterior finish. It is now totally skinned and primered. There are some pretty decent pics in the thread. I tried a sample, looked pretty good, went ahead with it for covering. I was inspired by people who use the mastic over canvas on wooden canoes. I used @ 6 gallons of mastic on the 11' standy trailer. It is under a portable garage cover for construction, but I have no doubt it will withstand the weather as well as painted canvas. The mastic is latex and the primer is latex. Latex is very resistant to weather, I use it on the house!! yuk yuk. There's my $.02 . I need to post on my thread, I am working on the inside.....Later, Dear Trailer Peoples.... Nodrog
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Re: PMF and foam

Postby John61CT » Tue Feb 06, 2018 9:52 pm

I'm thinking stick to Glidden Gripper.

Regular thickness for the adhesion and soaking through the finest weave canvas I can find, lots of coats.

Then stick with the same, but add some Liquitex's Liquithick or Golden's Liquid Thickener (Short Rheology) for a final few coats.

Obviously experimenting a bit to see how it works before using on the actual shell.

Also, I'm planning on going pretty big, standy by say 18 ft, some weight bearing aluminum framing to help with strength and a solar panel roofrack.

Thinking of going with aluminum screening under the canvas, for greater tensile support over these wider areas, should also help with puncture resistance.

Any feedback welcome.
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Re: PMF and foam

Postby GPW » Wed Feb 07, 2018 6:00 am

Take a hint from an old Artist … Try using GESSO to fill the weave … It’s not that expensive , it’s Very Thick , but workable and you can EASILY sand it to get a SMOOTH eggshell finish . We use a yellow plastic Bondo spreader to apply it … Since it’s also a primer , it saves a step … ( being Latex ( just like Gripper) , it’s paint compatable ) .
Applying it with the spreader prevents a huge build up or product , so not only does it fill the weave , it doesn’t affect anything else …. even repairs , should they be necessary …

Like this … ( what I use ) https://www.utrechtart.com/Blick-Profes ... 60.utrecht

Screen if you must for peace of mind , but it really isn’t “necessary" … I love the way everybody throws around the term “Puncture resistance” .. It reality it’s a “No-burger” … In all these years , nobody’s reported even a modest “puncture” , except me and that was through a RV “membrane roof “ of cheap vinyl , thin Plywood , foam and paper … Jayco roof … the limb went through it like it was butter … ( it was $5000.00 to fix the Jayco , a similar repair on a Foamie would be around $20.00 … DIY in 15 min. ;) )

There’s a Logic to all this …
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Re: PMF and foam

Postby GPW » Wed Feb 07, 2018 6:20 am

Check out my Facebook page to see how I GESSO a linen canvas to paint on … https://www.facebook.com/profile.php?id=100009558437222
It’s supposed to be smooth , and it’s made to last hundreds of years … :thumbsup: https://scontent-dft4-3.xx.fbcdn.net/v/ ... e=5B1DC495
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Re: PMF and foam

Postby John61CT » Wed Feb 07, 2018 1:03 pm

GPW wrote:Try using GESSO to fill the weave

I'm hoping because such large areas to do it all with brush and roller, but will definitely keep in mind, thanks.

GPW wrote:“Puncture resistance” .. It reality it’s a “No-burger”
I am looking at going off-road, boondocking off rough tracks, BLM land etc.

But yes, I can see prevention can be overkill when repairs are so easy.
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Re: PMF and foam

Postby GPW » Thu Feb 08, 2018 5:30 am

We tried brushes and rollers and they only ADD their own texture … Applying with a scraper the gesso is forced into the weave , leaving the top surface FLAT … and Smooth . You really must try it at least just to prove to yourself how Good it works … and despite the size of the spreader , it goes quickly ... :thumbsup:

I wouldn’t say it here unless it was absolutely true ... ;)
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