A more durable Foamie?

[rruff]

Wow, lots of replies! I thought I'd be notified. Looks like I came to the right place, you people aren't shy about thinking outside the box!

dancam: I did find a place to get 40 psi EPS semi local (only 150 miles away, Insufoam, Mexican company) but haven't gotten there and I need to see it. I've heard reports that there is a huge variation in structural integrity and QC with EPS, even the heavier stuff. Of the foam I've seen, XPS just seems a lot better.

Spraying fiberglass resin... no. Maybe I'd consider rolling it on. But I think if I wanted to deal with that toxic stuff I'd lay up fiberglass and epoxy over the foam, or polyester resin over plywood over foam. And then you still need a UV layer.

Plastics are interesting, but need their own durable coating for UV that will stick. Unless you pay for Filon. There are reasons why it is expensive.

GPW: How exactly do dents in PMF self-heal in the sun? Does the glue soften that much when it gets hot, and does the foam spring back? Softening might not be a good feature if the "denting objects" (mostly rocks and tree branches in my case) are encountered on a hot day. Or I need to climb on the roof to deal with solar panels. BTW I do want to be able to stand on the roof without damaging the surface or leaving an impression, even on a hot day!

Pmullun503: I looked at Styrospray awhile back and decided against it. Too finicky and not for long UV exposure. Also, I never have humidity over 50% here during the day unless it's raining.

I priced out the materials to build my shell using okoume 3mm ply, wood stringers, XPS from Home Depot, and fiberglass, polyester resin, and gelcoat, and came up with ~$3500. So I'm comfortable with that level of expense, even a little more if it's worth it. The plywood was the biggest expense, ~$1900 shipped. But oddly 400 lb of plywood sheets cost half as much to ship (from a farther distance) as an 18" high stack of foam sheets would have!

I want this thing to be durable and last at least 15 years with minimal maintenance. And it's going to get a lot of use. I don't mind doing experiments before I build, but I don't want the camper itself to be an experiment, ie a "lets see if it falls apart or not". I'm going to take it into the back country, so washboard and pounding over rough roads. And squeezing through tree branches. And twisting through ditches and ravines. I kinda settled on the materials I listed above because I felt comfortable with them, and it's similar to what I've done before. I trust wood bonding to wood a lot more than anything bonding to foam. Even though I love the idea of using little or no wood. This XPS isn't designed for a structural sandwich (even the heavier stuff), and based on reports I've heard from camper and surfboard builders a lot of people have had bubbling and delamination issues when skinning with epoxy fiberglass. Though most of that may be lack of properly texturing the foam.

Anyway I might as well give you a visual of what I'm thinking, with my crappy Paint and Sketchup files. The bottom of the camper bolts directly to the frame. I *am* going to use familiar materials for that! 1/4" plywood sandwich, foam and stringers, fiberglass on both sides.

[Pmullen503]

I don't think it would work in a female mold. It needs atmospheric moisture to cure so there is a limit to how thick you can lay it on in one coat. It stays somewhat flexible too. Which is good if you have a rigid structure underneath.

The big advantage for a tear is that there would be no seams; you can get a monolithic coating. You never have to worry about leaks at the seams. You could also do nice rounded shapes that might be hard to cover with PMF. You'd have to have all the gutters and door jambs in place when you coat it. Any gaps need filling. Give the foam a coat of latex primer and a light sanding before application and it will flow out to a smooth surface.

Having done PMF, I can say that this would be easier in some ways and certainly better as far as finish is concerned. I've never tried to actually spray it however, only brush on with a foam brush and it works well like that but would be very time consuming on a tear. A cheap hopper gun might be worth a try.

[Pmullen503]

................

I want this thing to be durable and last at least 15 years with minimal maintenance. And it's going to get a lot of use. I don't mind doing experiments before I build, but I don't want the camper itself to be an experiment, ie a "lets see if it falls apart or not". ...........

My thoughts exactly. No need to reinvent the wheel when there is so much collective experience with conventional materials. But a smaller project like a tongue box or cooler would be a good place to try it out.

BTW, UV concerns are handled the same way you would with epoxy: paint!

[dancam]

While pmf is not the strongest thing out there i believe it is a lot more durable than you think it is. Plese do a lot of skimming and reading before you start, i didnt do enough myself. Please look at post #2 in my build thread here: http://tnttt.com/viewtopic.php?t=66816 at the strength testing i did. I was impressed.
If you want no rot, use no wood. If you want more strength than foam use plastic, aluminum composite- acrylite...
Sounds to me like what you want is foamwith acrylite on the outside. Ill see if i can find that thread, just hang on.

Here: http://tnttt.com/viewtopic.php?t=67211

What about this idea? Make it using foam and minimal wood framing. Treat all the wood framing with the mixture reccomended here. Glue the foam and frame togeather. Then instead of canvass and glue just screw 1/8 or 1/4in plywood to the outside. Waterproof the seams, treat it all, paint it good, then in 10 years when it starts to rot just take the screws out and put new outer plywood on.
Sent from my SM-G920W8 using Tapatalk

[rruff]

Having done PMF, I can say that this would be easier in some ways and certainly better as far as finish is concerned.

One thing I'm concerned about is that Styrospray is typically used for temporary props. Does the material degrade with time even if it's UV protected? What have you used it on, and what is your impression? Does it take impacts well? Can it be pulled off the foam? How stiff is it? Also, what paint sticks to it?

What I'd like to do is take a decent size foam sheet (say 1' x 4' x 1") and skin it, then compare stiffness, strength, puncture resistance, and weight to... whatever. PMF, luan, epoxy fiberglass, Styrospray, etc. Actually maybe it should be made narrower than 1' or thinner than 1", because I made a panel like that with luan skins and supporting it on the ends it easily supports my 180 lbs. Even with a little light jumping!

[rruff]

What about this idea? Make it using foam and minimal wood framing. Treat all the wood framing with the mixture reccomended here. Glue the foam and frame togeather. Then instead of canvass and glue just screw 1/8 or 1/4in plywood to the outside. Waterproof the seams, treat it all, paint it good, then in 10 years when it starts to rot just take the screws out and put new outer plywood on.

My initial thought is that I'd be losing the strength of the structural sandwich. Maybe that would be ok on walls, but the floor and top need to be more solid.

[linuxmanxxx]

I did a floor with 3/4" from Lowe's with 1x2 framing and Luan both sides with water based contact cement and wood glue tb3 on wood and could walk on it all day long. Same for walls and flip the 1x2 vertical and double foam for roof zero sag. 3 build like this and it's way lighter than plywood and stronger and more rigid. Here's some specs on the styrospray hardness flex and strength. Pretty impressive if you combine it with the sandwich above and replace the outer Luan with the plastic. Can paint with oil or water based paints.

Sent from my Nexus 6P using Tapatalk

[linuxmanxxx]

http://www.industrialpolymers.com/image ... _Chart.pdf

Sent from my Nexus 6P using Tapatalk

[rruff]

Pretty impressive if you combine it with the sandwich above and replace the outer Luan with the plastic. Can paint with oil or water based paints.

Thanks for the info, sounds like it paints easily.

Have you made any test pieces with Styrospray?

I've decided to go with 4' x 6" x 1" test pieces. I'll cut down my luan skinned piece so it's 6" wide. I'm working on one the same size with 2x 10oz PMF skins. I'll probably get some Styrospray and epoxy fiberglass to compare.

When I get them done, I'll compare bending stiffness, puncture and dent resistance, and weight (I'll try to keep weight reasonably close to the luan). If anybody wants to play along, it would be most welcome!

[linuxmanxxx]

They have a sample small kit to order and try it. I haven't gotten any yet because I'm just getting fired up to go build mode. Miss the thrill of creating.

Sent from my Nexus 6P using Tapatalk

[linuxmanxxx]

The hardness scale shows it's harder than a semi truck tire that's pretty hard.

Sent from my Nexus 6P using Tapatalk

[ghcoe]

Your design looks as though you are into Overlanding/Expedition style travel.

[linuxmanxxx]

Your design looks as though you are into Overlanding/Expedition style travel.

And that needs weight reduction and strength increase which a sandwich with total adhesion would give you. The glue and adhered wall and shell do that in spades. Use cedar and it's even lighter.

Sent from my Nexus 6P using Tapatalk

[rruff]

Your design looks as though you are into Overlanding/Expedition style travel.

I like going places where I won't see another human. I lived this way for 13 years in campers I built on a '84 Toyota. That ended in 2003 though. A woman civilized me and made me live in a house and work for a living. We're still together and now she wants to vagabond again!

My biggest concern with PMF is puncture and dent resistance. I know I'm going to be hitting tree branches. PMF does seem to be quite stiff and light but it's such a thin layer. Particularly with this light foam, you need an outer skin that will spread the load out. Which is why I went with fiberglass-plywood-foam. Stiffest and hardest layer, then a thicker and less stiff layer, then the foam. But maybe a thicker PMF layer with a harder shell (Styrospray? Monstaliner? epoxy?) would be just as good, and I could get rid of the outer wood layer?

[ghcoe]

Every build technique is going to be a compromise. It just depends on what you want to compromise. They don't build tanks like airplanes, and they don't build airplanes like tanks. If you are snapping off branches and making sharp poky things then you are going to need the extra skin strength. If you are just pushing branches then the lighter skins will probably be fine. I find the canvas (10oz) over foam to be a lot stronger than I anticipated. Would it stand up to a sharp poky thing? Probably not. Would it hold up to pushing light branches? I think so.

I also just was reading up where some people are using plastic and metal screen as skin covering. I use flashing and dry wall beading to harden up the outside corners for just such issues. You could use aluminum diamond plate to harden frontal areas and leave sides and roof and back lighter.

Good luck