How-to coat insulation foam to make it stronger?

[NoCO2]

Ok, this isn't a how-to, but it's a how-to quetion that hopefully will help other people out once I get an answer.

I bought a HUGE piece of pink insulation foam the other day to start making aeromods for my car. However, it has one downfall. When using it to make a large surface, it's flexes...A LOT and that might ultimately lead to it breaking. It seems to work fine as a grill block material since there is structural re-enforcement behind it from the bumper pieces, but I want to make wheel skirts out of it and I'm concerned that making it as such a large piece with little, or no, support except on the edges, it might just break. Is there some kind of stuff I can spray on it, or coat it with to make it have sort of a plastic like shell on the outside? That might give it just enough structural re-enforcement that it won't snap with the wind hitting it and also might be able to give it a smoother shell so the paint looks better on it as well.

[JohnnyGrey]

You could use fiberglass (though I suspect a high concentration of hardener may eat at the foam). But then, why are you using pink foam insulation in the first place?

[NoCO2]

I thought about it for the front because the way the holes in my front bumper are, in order to be able to easily mount them and have it be relatively flush with the front of the bumper, I needed something with a good bit of depth to it and insulation boards seemed to be the best solution because my bumper isn't exactly flat so I needed to be able to get it to be one shape on the back and another on the front, I wanted it to be as clean as possible, so not just cardboard stuck on the front of the car. As for using it as a wheel skirt material, it's mainly just because I have a TON left over from the bumper and want to use it up. If there's an economical way of doing this then I want to do it, otherwise I'll just move to plan B which was this plastic sheet stuff I found at home depot that's used to cover overhead florescent lights.

[Bror Jace]

DO NOT use "Goop" to join pieces of styrefoam together ... eats it right up!

[Red]

Sprayable 3M adhesive?

[ebacherville]

fiberglass resin works, actually if you have small amounts of hardener it eats it up, make it a fast setting mix of resin, the faster it sets the less it will eat away.. ray non hardened resin eats foam, quick hardening doesnt have a chance to eat it..

And the resin hardens and melds with the foam making for a even stronger bond in the end.. works good, add fiberglass or even cloth to make it really strong.. the nose on my CRX project is all fiberglass and foam with a thin layer of bondo to smooth it out.. to make it look perty

[NoCO2]

Sweet, thanks for the suggestions.

I've done a very little bit of fiber glass work in the past, when I was 15 I fixed my grandparents golf cart that had some body work damage and I used some fiber glass to patch up the holes. I'll go to home depot this weekend and see what they have in the way of fast setting resin fiber glass stuff.

[metroschultz]

Originally Posted by NoCO2

otherwise I'll just move to plan B which was this plastic sheet stuff I found at home depot that's used to cover overhead florescent lights.

I used the semi clear plastic light lens material (styrene) in Barbs car.
It looks great at first, it is easy to work with, but it won't hold up to road use. It cracks and breaks too easily.
I haven't posted any more on her car since we got back from Tennessee, but I would not recommend using that particular style of plastic. Lucky for me it was cheap, or I could be really mad about the loss.
Go with your first plan or formulate plan C.
S.

[fshagan]

Fiberglass resins come in at least three formulations, polyester, vinylester and epoxy. Polyester is the least expensive, but also has the least amount of adhesion and can delaminate easily. Both vinylester, used in a lot of kit airplanes, and epoxy (used in boat building) can be used as resins for fiberglass cloth to coat the foam.

There's a method using foam to make kit cars at http://www.rqriley.com/frp-foam.htm that shows some of the process.

[ebacherville]

I was misinformed and mis nformed you .. sorry hiope you get this.. fiberglass resin works on the yellowish white foam.. the pink stuff gets eaten..

I was told the pink was fine but never tried it till yesterday.. tride it and yep the pink stuff melts with fiberglass resin.. spray paint too..

The white/yellowish foam in the foil backed sheets doesn't melt also spray foam doesn't either..

Some one talked about blue foam and i cant test that becuase here i cant find it anywhere..

THe white yellowingt foam in the foil sheets if you peal the foil off is very nice and flexable.. even 1" gets semi flexible with the foil removed.. been working with the stuff all day today .. great stuff to work with but its not reall strong enough unless you coat it with resin with some other fiber like fiberglass or cloth.. something to add some fixed strength.. fleece works great but end up being really thick when done..if you need a nice thin coating use fiber glass or t-shirt material from the fabric store.. many options play around and see what you come up with.

many people have had great success with just cardboard and fiberglass.

[ebacherville]

Originally Posted by fshagan

Fiberglass resins come in at least three formulations, polyester, vinylester and epoxy. Polyester is the least expensive, but also has the least amount of adhesion and can delaminate easily. Both vinylester, used in a lot of kit airplanes, and epoxy (used in boat building) can be used as resins for fiberglass cloth to coat the foam.

There's a method using foam to make kit cars at http://www.rqriley.com/frp-foam.htm that shows some of the process.

I always wanted to build one of those 3 wheeled cars like in that link.. now build it with a 125cc scooter rear end and you got a 100mpg car.. so so tempting..

[COMP]

Originally Posted by ebacherville

I was misinformed and mis nformed you .. sorry hiope you get this.. fiberglass resin works on the yellowish white foam.. the pink stuff gets eaten..

I was told the pink was fine but never tried it till yesterday.. tride it and yep the pink stuff melts with fiberglass resin.. spray paint too..

The white/yellowish foam in the foil backed sheets doesn't melt also spray foam doesn't either..

Some one talked about blue foam and i cant test that becuase here i cant find it anywhere..

THe white yellowingt foam in the foil sheets if you peal the foil off is very nice and flexable.. even 1" gets semi flexible with the foil removed.. been working with the stuff all day today .. great stuff to work with but its not reall strong enough unless you coat it with resin with some other fiber like fiberglass or cloth.. something to add some fixed strength.. fleece works great but end up being really thick when done..if you need a nice thin coating use fiber glass or t-shirt material from the fabric store.. many options play around and see what you come up with.

many people have had great success with just cardboard and fiberglass.

the blue board is the higher dencity (sp)

[fshagan]

Originally Posted by ebacherville

I always wanted to build one of those 3 wheeled cars like in that link.. now build it with a 125cc scooter rear end and you got a 100mpg car.. so so tempting..

I'd love to do that. But I'm also attracted to Riley's idea of using a small diesel engine in front and an electric motor in back, and just using a manual switch over when you run out of electrons. Running the diesel on biodiesel would be ideal. The only problem is that he is looking at a Kubota tractor engine, which I'm sure doesn't pass California emission standards.

As far as top-coating polystyrene foam, epoxy resin does not melt it, but the polyester resin does (I'm not sure about vinylester). You could try epoxy resin over the blue foam; it may work well.

[Chris D.]

Originally Posted by fshagan

I'd love to do that. But I'm also attracted to Riley's idea of using a small diesel engine in front and an electric motor in back, and just using a manual switch over when you run out of electrons. Running the diesel on biodiesel would be ideal. The only problem is that he is looking at a Kubota tractor engine, which I'm sure doesn't pass California emission standards.

As far as top-coating polystyrene foam, epoxy resin does not melt it, but the polyester resin does (I'm not sure about vinylester). You could try epoxy resin over the blue foam; it may work well.

Originally Posted by fshagan

I'd love to do that. But I'm also attracted to Riley's idea of using a small diesel engine in front and an electric motor in back, and just using a manual switch over when you run out of electrons. Running the diesel on biodiesel would be ideal. The only problem is that he is looking at a Kubota tractor engine, which I'm sure doesn't pass California emission standards.

As far as top-coating polystyrene foam, epoxy resin does not melt it, but the polyester resin does (I'm not sure about vinylester). You could try epoxy resin over the blue foam; it may work well.

Fill your eyes.....with that double vision

[NoCO2]

Well, we must be talking about something slightly different then because I have been spray painting the pink stuff for the last 2 or so days with white spray paint to make the grill blocks for my bumper (works rather well actually, fits like a glove when molded properly) and if I spray on a REALLY heavey coat, it doesn't melt, but the air in the foam comes through and causes some bubbling, so you just have to make sure you put really thin coats on, lots of times. I ended up doing about 10 really thin coats per piece I think and it came out really great (just wish I had a camera to take pictures with).

[elhigh]

Originally Posted by NoCO2

otherwise I'll just move to plan B which was this plastic sheet stuff I found at home depot that's used to cover overhead florescent lights.

That stuff has next to no integrity - just installing them in light fixtures is a crapshoot. Sure it's light, but it's really brittle. A little too much flexure or one pebble, and there goes your wheelskirt. If that takes place on the road and a fragment causes damage to another car, you're liable.

I've been wondering about foamboard myself. Coroplast requires I find a sign shop, but foamboard is at every Staples and Office Max. It's a little pricier, but I have experience working foamboard. Break out the X-Acto!

[adam728]

Skim coat it with bondo, then put fiberglass/resin on top of the bondo.

Of course, by that point you might as well just do a few more coats of fiberglass cloth, then remove the foam/bondo (which was now just a mold). I've helped make some molds for carbon fiber parts that way. Male foam form, bondo, smooth it all out, add release agent, spray fiberglass chop to make a female mold.

[NoCO2]

OOOO!!

Great call there adam728 on the making a mold for a fiberglass piece...I might just do that and make fiberglass molds out of bondo. I'll let you guys know how that goes!!!

[3wheeled]

We built an entire car body out of foam and then covered both sides with fiberglass and polyester resin. EXTREAMLY strong. I weigh 175 lbs and can stand on the front end with no cracking etc. The reason for the strength is due to covering both sides. Think about a steel I-Beam. The reason that is so strong is because steel is hard to stretch or compress. It bends easily but not so easy to stretch/compress. The I-Beam forces the outside lays to stretch and compress in order to bend the beam in two. Having foam covered in fiberglass (both sides) is like making a continuous I-Beam through out your body. Want to have some fun? Make a sample and see how hard it is to break.

Here is our car body. Don't laugh, we are not autobody engineers and autobody technicians Just an electrical engineer looking for something different to do.

http://picasaweb.google.com/stinger3wheel/Stinger