Sprayable foam

[MetroMPG]

Can of high expansion urethane foam.

[VetteOwner]

stuff is awesome and expands a whole lot. you can carve like a block of foam. i guarantee it wont be smooth tho. the stuff does adhere really good to vertical and underside surfaces and also your skin so for the love of whoever, WEAR LONG GLOVES otherwise you will have blobs of yellow foam on your skin for weeks.and it will hurt to peel off. (worse than super glue)

[MetroMPG]

guarantee it wont be smooth

You mean after carving it? Lots of air bubbles exposed when shaping it?

I don't mind if it's lumpy & uneven when applying it, if it can be shaped reasonably easily after it sets up.

Thanks for the tips.

[Silveredwings]

Originally Posted by VetteOwner

stuff is awesome and expands a whole lot. you can carve like a block of foam. i guarantee it wont be smooth tho. the stuff does adhere really good to vertical and underside surfaces and also your skin so for the love of whoever, WEAR LONG GLOVES otherwise you will have blobs of yellow foam on your skin for weeks.and it will hurt to peel off. (worse than super glue)

I found this out once, but I took it off my fingers with sandpaper.

BTW, can this stuff be hot-wire cut?

[JanGeo]

The stuff is carcenogenic so don't be inhaling the dust from sanding it. You can't hot wire cut it either and watch out for getting it too hot. You can coat your exposed skin with some lotion and it may keep it from sticking but vinyl gloves is better - it also gets into cloth and will not come out. Got a bunch on my sleaves of nylon winter jacket a few years ago insulating the basement ceiling joices and the stuff is still on the sleaves. It will not spray upwards very well either from those cans making it useless in doing ceilings. Use a vacuum cleaner running slowly when sanding to take up the dust. Use a coarse file to shaping and then fill with microballoons then cover with glass and epoxy or polyester resin. Adding heat and moisture will increase the expansion rate and yield a lower density and for small usage get some elmers urethane glue i.e. gorrella glue and hit it with some steem or hot water to set it up and expand it.

[MetroMPG]

Thanks for the tips, Jan.

What are microballoons??

(And don't say, "party favours for microchildren!" )

[JanGeo]

Very very light small bubbles of glass a trash bag weighs almost nothing - I purchased a 5 quart bucket of the stuff - it is vary static prone and likes to cling to the plastic container it is in. You can mix it with the resin and make a very light paste like body filler but it is very light. When used with superglue it sets the superglue up instantly and can be used to build up a surface rapidly or fill in voids. I got my stuff from Smooth-On in PA - turned out I drive right by the place on 78 after the NJ-PA toll. They also have two part expanding urethane foam with hard foam and soft foam curing with different densities for filling and structural usages. Got my glass and CF from US Composites - great prices but they killed me on the shipping from FLA.

[Silveredwings]

I bought some from Tower many years ago in a small jar made into a paste with something like aliphatic resin (elmer's). Here is a small quantity as they sell it now.

[trebuchet03]

Originally Posted by MetroMPG

Tin foil taped/pressed in the area that will serve as the base of the object being created makes a decent non-reactive "release agent", and will protect the paint.

Skip the foil - go for plastic wrap That was an alternative plastic film release suggested for vacuum bagging - it should work as a substitute for a mold release.

I second the vote for microballoons - very cool stuff - it also adds a lattice matrix to the resin structure (making it stronger). Just remember how much resin you originally started with as the MBs will increase the volume AND don't mix with the hardener - mix in the MBs then add hardener. I'm getting ahead of myself though :P

I think that foam will melt if you expose it directly to polyester resins (you may have better luck with epoxy resin though - but that's more expensive). A cheap way to fill in holes after it has been shaped is wax - a nice thick wax (a mold release paste wax would be best That could, in theory, protect the foam too.

Lastly, to make your part a bit smoother -- before layup, coat with some form of gellcoat. A thick resin (microballons won't work here) first - and then use thin resin for your glass. Or, mix a thickening agent (like fumed silica - cabosil OR a fairing filler) to make the resin thixotropic.

Once done, you can use a fairing putty to help get a very smooth part that will paint nicely.

SmoothOn is a great Supplier (sometimes a bit expensive, you need to price it out
I've used US Composites myself, and our HPV team has used them for the past three years because of cost and they are a somewhat local company (Ha! I just noticed Jan mentioned them too :P)

I'm just throwing a whole bunch of stuff out there - the route (and there's more) you take will be dictated by budget, availability (most of the stuff you can get online though) and how ambitious you want to be with the project


-------
Lastly - that is a GREAT idea Now I have more to think about :P

[lunarhighway]

would it be possible to use this kind of foam in a mold?

it would be easy enough to create a negative mold that can be filled with foam. one could set up a littele production line in case something like a front wheel fairing is damaged by the curb.

however "high expantion" may not be an advantage for such applications? or would a strong enough mold simply be required for the foam to force itself into the right shape?