Foam?

[Devin]

I need some foam to work with, something that's easily carved and sanded. I've thought of floral foam (used in flower arrangements) but maybe expanding foam would work better. Does anyone have any recommendations for expanding foam that works easy after setup?

[Johnnycrash]

Get ye to the store of hardware. What you are looking for in the blue (or pink) insulation foam. It usually comes in 2' by 8' sheets, that are up to 2" thick. If you find the section for dock building, they might have the blue foam floats. They come in MUCH thicker sizes, in the 24" range. Ask someone there, they should know for sure.

[Devin]

I had considered that insulation foam, as it seems the train guys love it for terrain modeling. I'd been avoiding it, though, as those sheets are huge and I only need a small piece. I didn't want to store all of the extra in my 2 bedroom condo. But with my search for alternatives running out, I think I'll stop by Home Depot on 6th Avenue on my way home. Thanks.

[Johnnycrash]

When you get there, ask if they have any broke sheets. It happens all the time, and they can't sell it. They may just give you a piece the size you need.

[Andrew Gorman]

Sign foam is urethane, so it holds up to common fillers better than polystyrene insulation. It also doesn't make quite as much of a mess as the insulation. I got a box of useful sized scraps from these folks:
http://atlassignsandplaques.com/signsupplies.aspx
The real pick of the litter for modeling foam is Renshape, but it is expensive and scraps are not super easy to come by. You can get sample sizes of renshape and sign foam, though.

[Devin]

Good idea on asking for the broken sheets. I'll give that a try.

Andrew, thanks for the sign foam suggestion. Another option I had never even heard of. For this project I'm going to destroy the foam during the process -- kind of like the lost wax casting process, but with styrene and foam -- but I'm going to get that sample box of the sign foam to try for other projects.

[Mr. Badwrench]

I would not use the green floral foam. I've tried that before, and it was way more trouble than it's worth. Blue or pink insulation foam is much better.

[Devin]

What types of issues did you run into with it? One of my computer consulting clients is a florist and he gave me a few blocks to try. The one thing I like about it in initial testing is that the Tamiya liquid cement does not attack it.

[Mr. Badwrench]

It is extremely soft and crumbly. It will crush under your fingertips with even the slightest pressure. I tried to skin over it with both sheet styrene and epoxy putty, but it was hard to get anything to stick, even using 5 minute epoxy. The top layer will stick to the epoxy, but everything under that will flake away too easily. When I skinned it with putty, I tried sanding it to final shape, but the foam did not provide enough structural strength, and the cured putty cracked and deformed under the pressure of sanding.

I've heard of other people using floral foam, and with care and practice I imagine it could be made to work. But you can do all the same things with insulation foam, without all the hassles.

[modelnut]

I have used the pink insulation foam a few times and plan tod do so in the very near future.

For one of my most successful sculpts I glued several sheets of the 3/4 inch foam together and cut and sanded them to shape. Then I hit it with a light dusting of Krylon grey primer. This ate the surface to a depth of maybe 1/8 inch. Then I laid on a thin coat of Magic Sculp. The foam and primer kept a good grip on the MS and made for a cheap but good quality project.

I know there are pictures posted somewhere on SSM. But I can't find them in the Gallery. I think it was a Model-in-a-Month entry. I finished it in 28 days --- a personal best!
When I find it I will post it.

- Leelan

[BROCK UPPERCUT]

you could look for a new house being built , when the workers go home for the day raid the dumpster

[Neb]

you could look for a new house being built , when the workers go home for the day raid the dumpster

That's how I got a 4'x8'x2" sheet of the stuff.

Well, it was sitting close to the dumpster....

[Lt. Z0mBe]

you could look for a new house being built , when the workers go home for the day raid the dumpster

That's how I got a 4'x8'x2" sheet of the stuff.

Well, it was sitting close to the dumpster....

...in the wall of a bricked house completed in 2004.

That's how I got most of mine. Building scraps from when my house was built and from scrounging the site of another home site.

Kenny

[bluesman]

The beauty of the blue and punk foam is that it is light, cheap and easily carvable or sculptable.

I have had pretty good luck skinning the foam with rolled out sheets of the Blessed Aves

[Joseph C. Brown]

The costume / prop makers over on the RPF boards often work with foam in quantities *waaay* bigger than most of us will ever tackle, and some of their work is awe inspiring:

http://volpinprops.blogspot.com/2009/09 ... shock.html

I've not tried these yet, but when I eventually do try, I'll post results:

For covering or coating materials:
[Link removed at owner's request - Admin]


http://www.industrialpolymers.com/produ ... tyrospray/

[Devin]

Wow, that makes my work downright puny. Amazing stuff.

I went with the pink insulation foam. You can see my progress Here. I haven't sheeted it yet, as I had to put that project aside for a client build.

Thanks to everyone for the suggestions.

[Joseph C. Brown]

Sweet!

I have always been fascinated with the lesser known river-only ironclads of the Civil War, both Confederate and Union. Nice work!

[Devin]

Thanks, Joe. After building a USS Weehawken resin kit, in which I ended up replacing a lot of kit parts "just because I wanted to", I wanted to do my first scratch-build, and the hull on the City Class gunboats couldn't be simpler (parallel keel, main deck, and casemate roof for the entire length of the ship).

Oddly enough, while building these ships, I get a very sci-fi feeling from them at times. There's something very steam-punk about the old ironclads.

[modelnutz]

I have a tip for skinning foam with Aves.
To help the Aves adhere to the foam, wipe on a thin layer of 5 min. epoxy to the foam. let the epoxy cure, then skin with Aves/Majic Sculpt

The epoxy acts as an adhesion promoter.
Without it, the Aves can pull away from the foam WAY too easily.

[Chacal]

The beauty of the blue and pink foam is that it is light, cheap and easily carvable or sculptable.

No. The true beauty of pink and blue foam is that you know, at a glance, if it is a boy's foam or a girl's foam.

[modelnut]

I usually give the finished foam a light coat of Krylon primer. It eats a bit of the surface so don't put on a heavy coat. Then I put on a thin layer of Magic Sculp. I've never had the putty pull away. MS adheres to the primer.

- Leelan

[AbsoluteSciFi]

I found some of the green foam at the Dollar Store once, it is so sandy that it is not only useless, but I could almost blow the grit off of it.

My project is made of construction grade polypropylene foam. While the detail is good, I felt that this foam was far harder to use than I wanted for.

http://i943.photobucket.com/albums/ad27 ... erm-31.jpg

I used spray adhesive to get the foam together in a big piece, then carved and sanded it down. I sealed the whole piece with wood glue, then coated it with several layers of resin. Insulation foam is not the greatest thing to use, Urethane foam is much better for several reasons.

First, urethane foam can be sealed with Nitrostain, a bondo product, then hit with resin. For polypropylene foam, you need to totally seal it behind a hard barrier before any resin product hits it. Spray paints are a problem too. Urethane foam is harder than insular foam as well.

Urethane foam comes at a cost, and vendors charge for square footage and shipping is considerable. The good news is that it comes in three grade of density for whatever your needs are. Urethane was developed for use in CAD plotted routers, which can make great things like complicated signage and the like.

Some things to consider when using foam:

Basic shapes that take well to resin. Compound shapes can be problematic if you want to keep them sharp, they tend to round out with thicker applications of resin.
Size of the detail.
The structure of the model. Foam is not a rigid medium it can break if stressed, or bow.

[kerick]

Has anyone ever tried turning a foam shape on a lathe? I want to make a round fuselage shape like the space ark or Mercury 9.

[Mr. Badwrench]

You could probably do it at low speed, using coarse sandpaper.

[Chacal]

I've been rereading the posts in here, and I want to add:

If you can't get a piece of insulation foam, or you don't want to buy a whole 8'x4' slab of it because you only need a tiny piece, the canned foam thing is the way to go: pour a bit of the foam inside a container (old tupperware, cardboard box etc.) and let it harden—afterwards you'll have a block of urethane foam, just like the foam you can buy at Home Depot. Just make sure the container is big enough, because the foam will be rough around the edges and you'll need to discard a great deal of it.

[naoto]

Has anyone ever tried turning a foam shape on a lathe? I want to make a round fuselage shape like the space ark or Mercury 9.

Perhaps you could use hot-wire cutter and rig similar to is described in article titled "How To Make Your Own Custom Foam Nosecones"
http://www.apogeerockets.com/education/ ... tter87.pdf

[kerick]

Has anyone ever tried turning a foam shape on a lathe? I want to make a round fuselage shape like the space ark or Mercury 9.

Perhaps you could use hot-wire cutter and rig similar to is described in article titled "How To Make Your Own Custom Foam Nosecones"
http://www.apogeerockets.com/education/ ... tter87.pdf

Interesting idea. I will look into this method. A coping saw may work in place of the hot wire cutter. I don't have the hot wire but I do have a coping saw. Thanks for the tip.

[seam-filler]

I've been rereading the posts in here, and I want to add:

If you can't get a piece of insulation foam, or you don't want to buy a whole 8'x4' slab of it because you only need a tiny piece, the canned foam thing is the way to go: pour a bit of the foam inside a container (old tupperware, cardboard box etc.) and let it harden—afterwards you'll have a block of urethane foam, just like the foam you can buy at Home Depot. Just make sure the container is big enough, because the foam will be rough around the edges and you'll need to discard a great deal of it.

Give the tub a light coat of vegetable oil. The foam pops out easily with reasonably smooth surfaces and you can use the tub again.

[AbsoluteSciFi]

Has anyone ever tried turning a foam shape on a lathe? I want to make a round fuselage shape like the space ark or Mercury 9.

What I have seen is someone taking a block of foam and wedging it between two blocks of wood, drilled holes into the wood @ center, then simply turned it by hand to sand the block down. This works great for fine sanding the same piece, and scribing too. By making this simple jig, you don't need a lathe or any other complicated piece of hardware, you only need to build a hand guide to make sure of even adjustments to center.

As mentioned earlier, by Naoto, a wire foam cutter could be used in conjunction with this jig, and flawless result achieved.

[Joseph C. Brown]

Kinda like these guys?

http://www.vatsaas.org/rtv/construction ... xture.aspx

And more construction goodnesses:
http://www.vatsaas.org/rtv/construction ... ction.aspx