Very Specific Foamie Construction Question

[Boatguy2]

Hi, my first post. Thank you in advance for reading it.

I have built a 50 foot high performance (light) catamaran out of corecell foam and epoxy fiberglass using resin infusion. I know my way around. Lol

In the process I became highly allergic to epoxy. Just like a kid who will die from peanuts across the lunchroom, same situation. I cannot use epoxy. It has even made me sensitive to other chemicals as well.

I would like to build the interior cabinetry out of foam and I would like to use the nontoxic methods that you guys used to make the teardrop trailers to build my cabinetry inside.

I have already done some of it using Formica as a face, but not all of it needs to be that hard or that heavy. Formica is not light.

Picture building a bathroom vanity for instance.

It will hold up a bathroom sink. It will have a faucet mounted. And a counter and a front face with some opening cabinets and maybe drawers.

To build this in foam I already understand that some wood needs to go in the core to support hinges and what not.

But could you tell me how to go about doing the lamination in a way that comes out as smooth as possible?

I have been picturing nylon. Do you know like a laundry bag? That’s pretty smooth stuff. But I have no idea if it’s appropriate for putting together some cabinetry.

The top face would be xps and Formica anyway for looks/durability.

The vertical faces and drawers and things seem like they could be done out of the techniques that you guys do.

Could you give me a quick introduction to how to make very nice smooth surfaces using these techniques? And strength wise? Do they make sense for vertical walls of a vanity?

Also why is it that you use tight bond 2 and not tight bond 3?

Thank you so much! Looking forward to learning.

[Pmullen503]

For a surface that doesn't need to be super durable, you can use a smoother, lighter fabric than canvas. I would still use cotton or linen since that will take paint or glue better than a synthetic. Then you can fill the weave with something like artist's gesso or even drywall compound. Then sand and paint.

I think people use TB2 because when the "PMF" method was first described, that was what was available. I've used both, it's the paint that makes it waterproof.

Depending how thick the foam is and what kind of weight you want to carry, you may want to edge the foam with wood strips for your vanity. You won't need that much; 1/2" maybe, vertically to hold up the front of the vanity and give a place to screw the hinges to.

The drawers probably should just be made of wood. Thick enough foam would reduce the capacity. Plus, nice natural wood drawer fronts would look nice.

[Boatguy2]

For a surface that doesn't need to be super durable, you can use a smoother, lighter fabric than canvas. I would still use cotton or linen since that will take paint or glue better than a synthetic. Then you can fill the weave with something like artist's gesso or even drywall compound. Then sand and paint.

I think people use TB2 because when the "PMF" method was first described, that was what was available. I've used both, it's the paint that makes it waterproof.

Depending how thick the foam is and what kind of weight you want to carry, you may want to edge the foam with wood strips for your vanity. You won't need that much; 1/2" maybe, vertically to hold up the front of the vanity and give a place to screw the hinges to.

The drawers probably should just be made of wood. Thick enough foam would reduce the capacity. Plus, nice natural wood drawer fronts would look nice.

Thanks for that advice!

I have 1” xps for all the interior cabinetry.

That makes sense about non synthetic fibers working better. The wick up and absorb the liquid at a smaller level and really become part of the matrix. I guess I’ll just try to find a balance between smoothness and fabric thickness/durability?

And wow. You’re right. I didn’t even think of something like joint compound for smoothing. That could make things very easy and allow me to use quite durable fabric.

Learned a ton from one post. Thanks

[Boatguy2]

Also, you know something really cool?

I’m not sure if anyone here is aware of the history, but back in the day, they used your process over wood on boats. Outdoors.

They took sheets of canvas and paint and used that as a protective barrier for the wood on deck.

Apparently it worked quite well in those days of wooden boats.

[Pmullen503]

1" XPS is a probably good size for that application. Make sure you sand the surface of the foam to ensure good adhesion. Just thoroughly scratching it up is enough.

Here's another tip: The printing on the foam is often recessed a bit and that can telegraph through if you don't fill it. Put a wet paper towel over the printing and iron it with an iron hot enough to make steam (too hot or too dry and you'll melt the foam) and the recessed lettering will expand and rise up to almost the surrounding foam surface. That means less sanding to get it flush.

[Boatguy2]

1" XPS is a probably good size for that application. Make sure you sand the surface of the foam to ensure good adhesion. Just thoroughly scratching it up is enough.

Here's another tip: The printing on the foam is often recessed a bit and that can telegraph through if you don't fill it. Put a wet paper towel over the printing and iron it with an iron hot enough to make steam (too hot or too dry and you'll melt the foam) and the recessed lettering will expand and rise up to almost the surrounding foam surface. That means less sanding to get it flush.

Great. Thank you for the tip on the lettering.

I was thinking about getting one of those rollers that pokes some holes into the foam instead of standing. Is that a viable method? I forget exactly what the roller is, but I remember seeing online that somebody was just rolling some kind of roller with a bunch of spikes on it across the foam to make perforations and it would stick nicely because of that.

[Pmullen503]

That roller is used for removing wallpaper. I think it might be called a "Paper Tiger". It does work.

But since you are trying to get a high quality finish with fabric over foam, I would use a sanding block with 80 grit paper. The block will show you high and low spots on the foam.

Again, you don't have to sand all of the hot wired surface off, just a good set of scratches.

[Boatguy2]

That roller is used for removing wallpaper. I think it might be called a "Paper Tiger". It does work.

But since you are trying to get a high quality finish with fabric over foam, I would use a sanding block with 80 grit paper. The block will show you high and low spots on the foam.

Again, you don't have to sand all of the hot wired surface off, just a good set of scratches.

Oh yeah. You’re right. That makes a lot of sense compared to roughing it up with the paper Tiger.

I wasn’t thinking that far ahead and I am so used to working with Fiberglass that I wasn’t considering how much the surface of the foam will matter. it matters a lot. Very thin, soft material between the foam and what you look at.

Thanks for pointing that out.

[GPW]

Boat'... Just a couple points . The Foamie trailers were originally conceived as more of a " Hard tent" rather than a sleek showroom travel trailer . Light , Cheap to make ,really easy to tow , and I'm allergic to Epoxy too so really like the lesser toxic materials used. Although the idea of a car show smooth finish is desirable , it's just not practical for a Foamie as many over the years have attempted it, and found out the difficulties ... ( Have you read the BIG thread ? "Thrifty Alternatives" , that says it all )

What does work is a simple construction , basically a Boat upside down attached to a trailer .. PMF , can look very neat , done right , and now there's no question of it's integrity as my trailer has been sitting outside for 10 years . Just keep it clean and painted and it will be fine ... Keep it in a garage and it will last indefinitely . The whole beauty of a Foamie as described is it's simplicity , ease of use , and simple inexpensive maintenance. A Trailer for Fun camping on the cheap .
Best thing to make PMF look GOOD is to give it a snappy paint job ...

[GPW]

Did anybody mention how Foam covered with PMF heals itself in the Sun ? Well it does !!! Small dents just fill back in with the Sun's heat . Fiberglass doesn't do that ...

[Pmullen503]

The OP was interested in cabin furniture. As we both know from our work with RC airplanes, you can get a decent finish on foam *over a small area* with the right techniques. Not very durable or waterproof but good looking.

That said, if you want a hard, smooth, car body-like surface on the outside of your camper, PMF over foam won't get you there.