Spray Styrofoam Insulation as Mountains?

Model Railroader General Discussion (Model Railroader)
1

With the exorbitant cost of extruded sheet styrofoam, it seems possible that modelers could realize the benefits of styrofoam, (weight, ease of carving, ease of tearout) while avoiding some of the high cost, by using the expanding spray styrofoam now becoming popular for use in the building trades.

Anyone ever tried this?

How long does the sprayed foam remain pliable enough to shape before hardening?

How messy is the process?

How well does the dried insulation carve?

Is the expansion unmanageable, or can it be controlled well enough to create finished terrain? Rough terrain that can be finished with ground goop? Terrain blocks that can be carved into the desired shape?

It seems to me the process would be similar to creating a mountain out of shaving cream, that eventually dries to shape, able to be shaped to at least some degree before hardening, and the main problems might be poor carvability, liquid mess before curing, or uncontrollable expansion.

If no-one has tried this yet, I have a lift out section of terrain under construction I will volunteer for the process, but if it’s already been tried and failed for whatever reasons, no sense in wasting time.

What does the MR collective have to say on the subject?

2

I saw this within the last year on someone elses layout. It was messy, and hard to control the expansion…by the time it could be molded into various contours, it had to be cut (defeating the original purpose of trying it…easier sculpting)

Only suggestion I can give is keep a dropcloth handy…:slight_smile:

3

Hi,

I just searched this and came up with this link:

http://www.trains.com/TRC/CS/forums/90467/ShowPost.aspx

hope it helps

Frank

4

All future terrain on our layout has to be removable to access staging, and the technique we used so far is carved extruded foam, with overlapped plaster cloth and lightweight spackling compound to hide the joints.

In one area, I’m using luan plywood suspended on drilled dowels friction fit into the main benchwork, and styrofoam scraps for rough terrain structure, which will be covered in additional plaster cloth and goop. Since the entire module is removable, a rough pile of spray styrofoam could be used in place of cut sheet foam,and applied outdoors to get around the mess.

I’ve never used the stuff before, so the obvious questions involve how runny it is before hardening, whether or not it will hold a rough mountain shape when dried, how well it carves after drying, and how the costs stack up per unit volume relative to sheet foam.

I know the stuff expands forcefully and can crush “formwork” if this is not allowed for, but if it will hold general shape enough to achieve a 45 degree slope angle, one or two sides could be “sectioned” with simple cardboard or even fascia if you were willing to make the fascia permanent there.

I’ve held off buying more sheet foam because I either have to cut it, or risk breakage while transporting it long distances on the roof carrier of my truck. If I can find a spray can of the stuff for not too much expense, I might try it just to see what happens, unless of course, someone raises additional problems that would make it a waste of time. Nothing to lose except for time and the cost of one can, if it doesn’t work, I’ll just cut it loose and re-do it with stacked sheet foam.

5

take a look at Bragdon ent. or mountains in minutes

6

Used it in my prior life as a contractor, and tried to use it ONCE on the layout!!

  1. You get a very small amount for the buck[:(!]

  2. It sets up too fast to do anything with it [|(]

  3. It has to wear off anything it gets on - got it on a new pair of jeans - threw them out a couple of years later with the goop still on it[}:)]

[tdn][tdn][tdn]

7

While working at Dunham Studios building large display layouts we used the same type of foam as is used by the building trades. I think the smallest quantity that could be ordered was 50 gallons (2x25). The professional product expands immediatly and can be carved in about 45 minutes. We used a low expanding product, about 2-4 inches - you still have to have some kind of substructure. The higher expanding is less dense (larger air pockets - harder to carve).

It’s great stuff to use, but not very economically practical for small to medium sized layouts.

BTW with any type of spray foam, it has to fully expand and harden before it can be worked (carved). It acts like a suffle and collapses if you try to shape it before it’s fully cured. It will stick to anything in it’s semi-liquid/soft state and it’s very difficult to remove.

On my home layout, I have used foam-in-a-can, (like Great Stuff), mostly to blend the pink and blue extruded styrofoam layers or build up some smaller areas. A can can cover an area about 2x3’ 3 or 4" thick. To carve rock formations, the extruded foam carves better than the foam-in-a-can. Any carved areas of spray foam still has to be coated with something to close up the exposed air cells, (I use thinned vinyl spackeling compound).

I’ll add some pics.

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Jeffers wrote-With the exorbitant cost of extruded sheet styrofoam,

Home Depot, last week-4x8x1"-$10, 4x8x2" $22.
That works out to 32 cents and 68 cents/sq/ft.[%-)]

I’ve used can foam for insulation. Bought 3 cans. 2 of them plugged up before they were half used. They don’t seem to like it when you use them, let them sit, use them, let them sit. Seemed like the kind of thing that once you open it, you should use it all.
IIRC, the cans were $7 each.

9

I tried the stuff and it wasn’t worth the time and money.Personally I have had better luck with foam( the white kind"Yes") And better luck with plaster cloth.The spray foam stuff is everything that everyone has already stated…Very Messy, hard to control, and the work time is not worth the effort in my opinion.

C.c

10

Last time I priced extruded foam here, it was $35 per 2" sheet. I’ve got about 50 square feet of new layout, three quarters of which will be mountainous, call it 40 square feet. Call the ridgelines two feet high, divide by half because they are triangular in cross section, 40 cubic feet of foam, times 1.5 for waste, 60 cubic feet needed, 4 feet by 8 feet by 1/6th foot thick per sheet, 60 cuft total divided by 5.3 cuft per sheet, 11 sheets needed, times $35 per sheet, $380 give or take, plus tax, a round four hundred bucks.

Not a problem for a labor of love, however…

Each of 11 sheets has to be sliced lengthwise to fit in the truck, then spliced back together, most assuredly in the least convenient way to reassemble as mountains, plus the styro-grommets all over the house, hey, the spray foam SEEMED like a good idea, at least worth looking into.

Okay, so it’s gooey, bubbly, sticky, messy, hard to carve, and WAY more expensive than sheet foam, exploration over, extruded foam wins by a landslide, nothing to see here, move along please.

How solid does Fix-a-Flat get inside a spare tire?

Readi-whip?

Cheese Whiz?

(Mmmm, mistakes can be EATEN…)

11

I’ve been experimenting with “Great Stuff” window insulation foam, and it’s cheaper knock-offs (Red Devil). The benefits of this “polyfoam” is that it is more durable and flexible than extruded foam insulation, which I’m also using. That’s the fundamental difference, it’s polyfoam, with polyurethane.

My experiments - right now, it’s just that, I’m playing with a small “diorama” section before committing it to my layout - have revealed a couple of things about Great Stuff-

  1. You have to carve it. It’s not mountains from a can, unless you want you mountains to look like whipped cream. And it expands considerably and unpredictably, so you really can’t control it into shape. But if you lay it on lightly, in rows and layers, you can learn to control it in depth. Lay it in a depth of about 4 inches, and then carve to suit. It does not carve well into final rock shapes, for there are serious air pockets; hence it needs sealing. It does, however, make a nice scenery base, especially for access hatches and tunnel coverings because of its flexibility and durability. It sprays in place and stays and flexes in place.

  2. You need a good structure base underneath it…window screening works, and I’m also using cardboard strips with shelf liner covering that. Because the stuff, you don’t want it to get on any track underneath the tunnel, and it will fall and seep through anything with large netting…so keep the sub structure something with tight netting that prevents it from seeping through.

  3. I will then glue foam rock formations on it, as I am concentrating on the Great Stuff for removable access hatches where the merits of the polyfoam’s durability and flexibility will be made use of. I don’t want to use hydrocal cast rocks there because of the abuse the area will inevitable get. I think the foam r

12

$35/sheet![:O] Where are you located? I was kind of surprised to see it hasn’t gone up in price in the last 2 years where I live.

13

I have used Great Stuff in our club layout as a foam glue, between two or more sheets of styrafoam. It doesn’t expand vertically in this manner, but rather horizontially and so a little bit can go a long way. I also use it as a crack filler between the plywood and the stryfoam sheets. As mentioned it is flexible so it very forgiving in moves.

The only type of rock that I can think of that spray foam could easily represent is pahoy-pahoy lava. But I don’t know of a lot of North American railroads that are built on or around that stuff.

It has it’s uses, just not in moutain building.

14

(1) Yes, about 10 years ago and again recently to see if it is still as hopeless… it is…

(2) About 20 seconds or an unknown period headed toward infinity if the stuff decides not to do what it’s supposed to… in this case the soggy mess is a disaster to try to scrape off… and it gets on everything… to which it then sticks permanently and cures rock solid…

(3) If you

15

But we’re paying for the cubic foot - the sheets at least here that I’ve seen are sold as 48"x96"xn" (where n is the thickness). So a 1" thick sheet is (assuming my math is correct) roughly 2.67 cubic feet, and a 2" thick sheet is (again assuming my math is correct) roughly 5.33 cubic feet.

That means they cost $3.75 (rounding up) and $4.13 (rounding up) per cubic foot… assuming yet again that I remember how to do math.

16

Exorbitant? Have you priced quality 3/4" plywood recently? 2" foam seems like a bargain in comparison!

Yes, I have. Keep FAR away from this construction method.

Never. In other words, you can’t work the material, beyond the initial application. It’s extremely tacky, and will aggressively stick to any tool you try to use to shape the goop.

Adding the spray foam isn’t all that messy, so long as you get it exactly where you want it. Don’t try to touch it while it’s wet, and don’t get any where you don’t want it. If you do, you have to wait until it’s dry and carve/sand the material away.

Horribly. You can CUT it, but you essentially can’t effectively carve or sand it. Imaging a giant block of kitchen sponge.

Spray foam expands to 2-4 times it’s initial size when sprayed out of the can, and it expands in pretty puffballs which look absolutely nothing like real terrain. The bottom edge will have an inward curve to it, which is again completely unnatural. And once you start carving the stuff, you quickly realize that the interior of the puffballs looks like Swiss cheese. Again, completely unrealistic.

[quote]
It seems to me the process would be similar to creating a mountain out of shaving cream, that eventually dries t

17

That’s true and more accurate…you and CUT it, but not CARVE it. That’s a good point of distinction I didn’t articulate well.

I do think it has its uses though…when you need a durable, flexible sub structure for scenery, in limited stretches. It is not a final scenery layer, however, and should not be thought of as such.

18

I tried it for rock molds and the result was not good. The air bubbles get trapped between the mold and the foam and you end up with Swiss cheese rocks. Also, the texture was not good. I could have brushed some plaster over the foam rocks to cover up these defects but then would have lost the detail of the molds so I wrote it off as experiment that didn’t work. I can see using expanding foam on a limited basis to give a basic shape but it’s going to have to be carved after it sets up. It would be easy to put on too much as well. As someone pointed out earlier, if you don’t use the whole can at once, it will clog and you have to throw the rest away. It just seems the minuses far outweigh the pluses. There are better ways of contouring your scenery.

19

Are you sure you weren’t looking at 3" foam for that price? My Home Depot has 1", 2" and 3" panels. The 3" ones are $36.

20

I’ve used spray insulation foam as a jetty. It works well, but as someone said, it can get plugged up easily. I learned this the hard way and having to go and buy another can from Ace. As soon as you are done with spraying, immediately clean it out with a acitone (nail polish remover) or stick a wire or pipe cleaner up it and work it around.

As far as carving it goes, it is very simple and is like carving out foam insulation board. Obviously don’t use the foam for the whole mountain, but stick a bunch of recycled foam boards underneath to form the basic shape and contours of the mountain and then later spray on the foam. Then carve out the foam. As far as messiness goes, I didn’t have any trouble with it. Just treat it like spray paint, the harder you push on the nozzle, the more it comes out and the faster. I don’t know too much because my project was relatively simple, but this might help.