Page 1 of 1

How strong is PMF?

PostPosted: Mon Sep 02, 2019 6:32 pm
by 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?

Re: How strong is PMF?

PostPosted: Mon Sep 02, 2019 7:07 pm
by 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?

Re: How strong is PMF?

PostPosted: Tue Sep 03, 2019 6:36 am
by 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.

Re: How strong is PMF?

PostPosted: Tue Sep 03, 2019 8:34 am
by 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.

Re: How strong is PMF?

PostPosted: Tue Sep 03, 2019 7:34 pm
by 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

123715

Re: How strong is PMF?

PostPosted: Fri Sep 06, 2019 7:16 pm
by WalkersDad
Wow, what did you use for a chassis?

Re: How strong is PMF?

PostPosted: Fri Sep 06, 2019 8:01 pm
by 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 123623 135629


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

145117 145203

Re: How strong is PMF?

PostPosted: Fri Sep 13, 2019 8:55 pm
by 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.

Re: How strong is PMF?

PostPosted: Sat Sep 21, 2019 8:11 am
by 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?

Re: How strong is PMF?

PostPosted: Sat Sep 21, 2019 8:20 am
by theskyking123
Is anyone for hire for Consulting?

Re: How strong is PMF?

PostPosted: Sat Sep 21, 2019 11:16 am
by RJ Howell
theskyking123 wrote:Is anyone for hire for Consulting?


Me thinks you just hired quite a few! :D 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!