Sprayable foam - Gas Savers

MetroMPG · 04-04-2007, 05:56 PM

Can of high expansion urethane foam.

VetteOwner · 04-04-2007, 06:22 PM

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 · 04-04-2007, 06:32 PM

Quote:

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 · 04-04-2007, 07:18 PM

Quote:

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 · 04-04-2007, 07:29 PM

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 · 04-04-2007, 07:33 PM

Thanks for the tips, Jan.

What are microballoons??

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

)

JanGeo · 04-04-2007, 07:42 PM

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 · 04-04-2007, 08:08 PM

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 · 04-04-2007, 10:43 PM

Quote:

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 · 04-05-2007, 02:07 AM

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?

Bill in Houston · 04-05-2007, 07:06 AM

Quote:

Originally Posted by trebuchet03

I think that foam will melt if you expose it directly to polyester resins

I think that this urethane form is impervious to polyester resins. It is impervious to everything else, for sure.

Wear gloves, cause it won't wash off, like everyone has already told you.

This should be a lot of fun for you.

MetroMPG · 04-05-2007, 07:34 AM

Yeah - I'm looking forward to trying this. Now I just have to wait until winter goes away again. (Snow on the ground this morning.)

Quote:

Originally Posted by lunarhighway

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

Should be - you can get foams with different expansion rates (so you don't bust your mold).

Or - just leave an opening so the foam can expand out if it needs to.

Maillemann · 04-05-2007, 08:52 AM

Quote:

Originally Posted by lunarhighway

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

Not effectively. While it depends on the size of the mould, these types of foams require contact with air to cure. If it's a large piece (and by large, I mean larger than intended application) the outside will crust over but the interior will remain gooey. It can be cured by cutting through the exterior skin, but then the uncured foam will spew out as it expands and cures, often collapsing the shape of the object as it does so.

If you want to use foam in moulds, use the proper products. Check taxidermy catalogues, SFX suppliers, and marine (as in boat) outfitters for urethane or polyester casting foams. They're available in both rigid and flexible types, of varying densities.

http://www.tapplastics.com/shop/product.php?pid=79&
http://www.smoothonsecure.com/store/...7d82dc70d7c203
http://www.vandykestaxidermy.com/product/01352499/

trebuchet03 · 04-05-2007, 11:23 AM

Quote:

Originally Posted by lunarhighway

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

This stuff probably isn't the best (as mentioned). And if you're casting - it would probably be beneficial to get a foam that skins

Quote:

Or - just leave an opening so the foam can expand out if it needs to.

Yep, that's the best way when you don't know exactly what volume the stuff will expand too

It's much easier to sand off a nub than to add on a chunk :P

Quote:

I think that this urethane form is impervious to polyester resins. It is impervious to everything else, for sure.

Good to know

Of course, it's always recommended to test :P

Bill in Houston · 04-05-2007, 11:45 AM

Quote:

Originally Posted by 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.

You could use an open-topped mold to mold "blanks" that you could then shape. For example, to make a deflector for in front of the tire, you could mold a triangular prism shape, let it cure, and then file/sand it to final shape. Like others have said, if you really want to mold parts, you can buy foam especially for that purpose and get better results.

cfg83 · 04-05-2007, 12:20 PM

Bill -

Quote:

Originally Posted by Bill in Houston

You could use an open-topped mold to mold "blanks" that you could then shape. For example, to make a deflector for in front of the tire, you could mold a triangular prism shape, let it cure, and then file/sand it to final shape. Like others have said, if you really want to mold parts, you can buy foam especially for that purpose and get better results.

Would a "paint roller tray" make a good triangular mold? I ask because I have been looking at them as being good wheel-well deflectors, but I could never find a good one to work with.

Question : From all of the examples posted in this thread, which one is the "foam especially for that purpose" that you are talking about?

CarloSW2

Bill in Houston · 04-05-2007, 12:42 PM

Quote:

Originally Posted by cfg83

Would a "paint roller tray" make a good triangular mold? I ask because I have been looking at them as being good wheel-well deflectors, but I could never find a good one to work with.

Question : From all of the examples posted in this thread, which one is the "foam especially for that purpose" that you are talking about?

Sure, a paint roller tray could be a good mold. For large voids, the directions may give you specific guidance to help avoid some of the problems others have mentioned, like spraying with water. See http://greatstuff.dow.com/index.htm
Whatever you use for a mold, make sure that you line it with something like foil or plastic wrap.

Maillemann suggested some foams that might be more appropriate for molding a couple of posts up... I do not have experience with them. I have only used Great Stuff and Gorilla Glue.

lunarhighway · 04-05-2007, 03:23 PM

perhaps using an open mold and building up the shape with layers could solve certain curing problems?... something like that paint roller tray will not be all that deep to fill ... and perhaps drilling a few holes in the bottom might allow the foam at the bottom to dry. more appropriate foams would be preferable but they'd have to be available...

firmly attaching the foam to metal or plastic could be another problem...

i supose it won't support screws directly but perhaps plastic wall plugs or even a full armature can be molded in.

i really want to do some serious aeromods but i'm having a hard time finding any usable material this thread sparks new hope....

Bill in Houston · 04-05-2007, 03:58 PM

Quote:

Originally Posted by lunarhighway

perhaps using an open mold and building up the shape with layers could solve certain curing problems?... something like that paint roller tray will not be all that deep to fill ... and perhaps drilling a few holes in the bottom might allow the foam at the bottom to dry. more appropriate foams would be preferable but they'd have to be available...

firmly attaching the foam to metal or plastic could be another problem...

i supose it won't support screws directly but perhaps plastic wall plugs or even a full armature can be molded in.

i really want to do some serious aeromods but i'm having a hard time finding any usable material this thread sparks new hope....

The paint roller tray could be lined with damp paper towels or damp brown paper bags, or something like that. A layer of foam could be put in, spritzed with water and another layer put in. Maybe? Jangeo said something about steam...

As far as attaching, something like the expanding anchors for sheetrock might work. Or a simple armature. Or T-nuts inserted through expanded metal, and then foamed in place. Of course, you put something like shortening on the screw threads and thread them into the nuts or anchors before you put the foam in, and then unscrew them once the foam sets.

trebuchet03 · 04-05-2007, 04:20 PM

Quote:

Originally Posted by lunarhighway

firmly attaching the foam to metal or plastic could be another problem...

If you know where your attachment points are... You can include a sheet of steel or aluminum (pre-drilled and pre-tapped) into your mold before adding foam

The same goes for composites - you can add a metal core if you know there's going to be a support attachment in that area

Just make sure to make the plate big enough to get a good surface area to bond with the foam.

Compound curves make it a little more difficult - but not impossible

Lastly, if you're using the foam directly on your car -- you can attach the mounting brackets exactly where you want them - fastener and all

Ryland · 04-05-2007, 10:48 PM

I have used this kind of foam alot in houses, and a little in building molds, and so on, you can normaly get it about 3 inches thick befor it gets to thick to cure, if you have an inclosed mold then yes, it will take much much longer, as much as a month or more if it's a compleatly inclosed mold, open top like a paint pan should cure in a matter of a few hours, to a day depending on the foam you get.
if you want to do an inclosed mold, get the two part foam, it comes in two tanks, and can be sparyed as thick as you want, the two parts react with each other and cure fully, it's commenly used in houses, the kind of stuff they would use to spray all of your wall cavitys full, only you can get it in smaller quanitys, altho I think for the two part stuff the cheapest set up is around $50, but I haven't personaly bought one, so I might be wrong.
another thing to think about is regular fiberglass, I recently made a fiberglass mold of a metal tractor seat, so that I could make copies for putting on recombent bicycles, useing foam as a core in a piece made from fiberglass works really well.

VetteOwner · 04-08-2007, 06:58 PM

patches holes quite nicely:

MetroMPG · 04-08-2007, 07:56 PM

Nice!

Bill in Houston · 04-08-2007, 08:30 PM

So here's another thought I had about the foam. If you can build a prototype out of something easy to work with, you can use this foam to make a mold to mold a more durable final piece. I know that didn't make any sense. I'll use an example.

Say you want some fiberglass wheel skirts. You built prototype wheel skirts out of something easy to work with, like, uhh, floral foam or cardboard or paper mache or whatever. Silly putty, whatever. Then, you cover the prototype with foil or plastic wrap. Then you spray on the foam. While it's goopy you put in some small pieces of wood or plastic or whatever to make it stiffer. Once the foam sets, you remove it from the prototype piece.

Now, you have a really good start on a mold. You fill in the wrinkles, sand it nice and smooth, seal it with something, sand nice and smooth again, and wax it up with some paste wax or whatever you want to use as mold release.

Then, you spray/paint in your gelcoat if you want, and then lay up the fiberglass like you normally would. Keep building until you get to the desired thickness, pop off the mold and voila, your nice pretty fiberglass fender skirt. And maybe you can use the mold again to make a skirt for your buddy with the same kind of car...

trebuchet03 · 04-08-2007, 08:43 PM

Quote:

Originally Posted by Bill in Houston

So here's another thought I had about the foam. If you can build a prototype out of something easy to work with, you can use this foam to make a mold to mold a more durable final piece. I know that didn't make any sense. I'll use an example.

Say you want some fiberglass wheel skirts. You built prototype wheel skirts out of something easy to work with, like, uhh, floral foam or cardboard or paper mache or whatever. Silly putty, whatever. Then, you cover the prototype with foil or plastic wrap. Then you spray on the foam. While it's goopy you put in some small pieces of wood or plastic or whatever to make it stiffer. Once the foam sets, you remove it from the prototype piece.

Now, you have a really good start on a mold. You fill in the wrinkles, sand it nice and smooth, seal it with something, sand nice and smooth again, and wax it up with some paste wax or whatever you want to use as mold release.

Then, you spray/paint in your gelcoat if you want, and then lay up the fiberglass like you normally would. Keep building until you get to the desired thickness, pop off the mold and voila, your nice pretty fiberglass fender skirt. And maybe you can use the mold again to make a skirt for your buddy with the same kind of car...

That's almost EXACTLY how we made our HPV fairing.... Bondo makes a great filler/fixer for any imperfections in your foam cast

Instead of making a second one from your foam negative - which is really a tool... Make a better tool with fiberglass off of your first part. Unless you just want to make one or two more. But if you're going to make 5-10+ a more permanent tool will make a stable platform to work from (plus it can be vacuum bagged)

ArtFox · 06-05-2008, 11:48 AM

1) Which plastic sheeting or wraps will protect the body paint when building up a clump of spray foam for wheel skirts and such?

2) Has anybody combined polystyrene (pink/blue) or urathane home insulation boards (foil backing peeled off) and spray foam to build up contours? Does the spray-on melt the polystyrene?

JanGeo · 06-05-2008, 12:40 PM

stick with the yellow urethan foam because the bondo will attack the polystyrene Probably! but not the urethane and it should also be used with urethane glue i.e. Elmers makes it in various bottle sizes (Home Depot) and if you hit it with steam or hot water it really foams up fast and is a lot harder than the insulating foam and can be used to bond it together. Urethane will not stick to Saran wrap and some plastic shopping bags too.

bowtieguy · 06-05-2008, 01:18 PM

i used the great stuff brand from home depot to make a grill block. after applying black paint, it's not even noticable with the exception of very near viewing.

ArtFox · 06-05-2008, 02:13 PM

Thanks for the advice.

I only have the "minimal expansion" foam around the house. I did not want to distort some window frames I was insulating. Must get the max expanding stuff!

I have rasps, carving tools and dust masks already...

PaleMelanesian · 06-05-2008, 03:06 PM

Acetone will remove it from your hands, while it's still wet. It says so right on the can, and I've verified that it works. Have some on hand! Once it's dried, though, it's too late.