How strong is PMF?

[WalkersDad]

So I’m looking at building an “Ultra light” that will pretty much be all Foam insulation board. ... my wife’s little suv can only tow 1200lbs ... So I’m wondering about the exterior Skin strength. Everyone saids Poormans Fiberglass is rigid, but does it give enough strength to stand up to 65mph highway speeds? Would I be better using actual glass and resign? Weight is top concern and I gather PMF is lighter, but is it strong enough?

[TimC]

My PMF has held up fine with four years and about 5k miles. It is backed up with two layers of 1/8" plywood. I think there are others using it on foam without plywood backing. Their experiences would be helpful if you don't wish to add 1/8" ply. But if you want a tougher area maybe just the windward area up front backed up with ply under the PMF?

[Pmullen503]

Mine is foam and canvas only, five years old and has held up fine. There are many many successful foam builds on this site. They are not blowing up at highway speeds.

They are easy to build, don't rot, and light.

[RJ Howell]

I'm in the process of building my first. Every step it has just become stronger. Just enforcing the seams/joints made a big difference. I've only just started the canvassing of the exterior. The only added structural element I added was a 1x1 aluminum angle on the roof. I'm over 4ft wide and two pieced. Was it required, who really knows, yet I like how it worked out.

My build process is here: http://tnttt.com/viewtopic.php?f=55&t=71879

Several very good foamy builds to read and follow.

[tac422]

The Big Pink is primarily foam, weighs 1000 lbs., and has traveled thousands of miles up to 85+ MPH.

That's fully loaded with the refrigerator, AC unit, spare tire, hydraulic jack, jack stands, loaded cooler, 4 folding chairs, a popup tent ,luggage etc...
viewtopic.php?f=55&t=56441&start=296

[WalkersDad]

Wow, what did you use for a chassis?

[tac422]

It's a Harbor freight 4x8 trailer.
The build is documented here:
http://tnttt.com/viewtopic.php?f=55&t=44091

Mike built it


and I finished it, thread here :
viewtopic.php?f=55&t=56441

[Tyrtill]

Pretty strong!! I'm a 200lb guy standing on ~28" span no obvious damage. The thing you don't see is it flexes down about 3". PMF and XPS seems to be very strong but not very rigid.
This is 2" xps with 10oz harbor freight drop cloth with glidden gripper and behr premium ultra paint.

Here is another test I did with a scrap. Very resilient stuff.

[theskyking123]

I'm new, can someone post links to PMF, and to the canvas people are using?
How are people affixing these to the foam?

[theskyking123]

Is anyone for hire for Consulting?

[RJ Howell]

Is anyone for hire for Consulting?

Me thinks you just hired quite a few! Cost of such?? Pictures and updates of the build!

The bonder of choice (as I read) was Glidden Gripper (the original, not PPG). I start checking your local HD and see if they have any and scoop it up! Several of us are testing other brands of primer to find a good replacement. Key to success, in my mind, it a good bond to the foam to start with. I doubted what I ended up seeing.. They were all right, done right, it is pretty dam strong!