quick question on general layout scenary construction

[worldrailboy]

go with foam layers of some sort and hack it down to rough shape wanted then clean up any loose foam shavings afterward...or build the needed profiles out of wood and use cardboard stripes to hold all the plasterings...or does anyone have other ways to suggest?

it'll be woodland scenic for the ground as far as I've decided. other scenary items including poke-down-in-ground trees might come from other brands instead naturally tho

not much of the layout is really going to be level at all except for the coastline water itself so thats why I had to ask this so I could make up my mind which way to go.  I'll try it on top of a scrap 2x2ft-or-something board to be sure before buying big amount of supplies for the actual layout construction itself

[cteno4]

other option with the foam is to also use hot knifes, smelly, but gives you other shaping options that are not as messy, but you usually end up doing some rasping or sanding eventually and getting foam fuzz.

ive been converted to foam as it gives you a strong but light weight base to support things. with plaster on cardboard you do have to be careful about making sure your plaster has not gone off or later wetting for scenery application can cause it to weaken (see aaron's plaster cloth mountain thread). this comes up from time to time on boards.

the jrm layout has a mountain on it thats like 3' x 3' and about 2' tall, all foam with plaster on top of it. works great and it gets picked up and set on the layout all the time as transported to shows on its own palette. its shown no evidence of cracking or other structural issues.

foam is also nice as its easy to plant trees into or if you want to later excavate a new area you have something to dig into. plaster cloth on cardboard you have to glue trees in their holes and you have to try to make a new structure inside to support your newly excavated area and a bit harder to fare your excavation into the existing contour.

also i think the foam gives you the chance to sculpt interesting features and play a lot. its harder to do this with contours and then layering plastercloth on that as then you need to do more building up to get the finer features which can be a lot harder than with sculpting foam.

great tools for working foam detail shapes

http://www.widgetsupply.com/page/WS/PROD/file-rasp/BCT46

cheers

jeff

[worldrailboy]

I've been thinking about the foam option more too so thank you jeff.

does beg a silly question, does the foam colour matter for this kind of case?

[cteno4]

nope color does not matter. ive heard different reasons for the color differences: density (R factor), thickness, brand, not sure which is right!

but they all work just as good as long as its the extruded styrene. dont use the beaded or its a surpurb mess! also the polyurethane foam board (brown usually between two layers of foil) does not work so well. some folks have used expanding polyurethane foam to make hills, but there are some issues with outgassing that might not make this a great choice.

you can get some cheap, simple hot foam cutters at craft stores (like acmoore and use a 50% off coupon there) and easily adapt them to a low voltage wall wart to replace the batteries. there are fancy ones that get expensive fast. you can also easily roll your own with a little electrical and hardware skills. you can use hack saws or hand scroll saws as the frame and some nicrome wire and a good solid dc power source.

cheers

jeff

[quinntopia]

I'll second everything Jeff said (why I feel the need to make a redundant post escapes me at the moment).

I've used some of the 'expanding foam in a can stuff', and while it appears to be fast, easy and convenient, I've found it to be quite unstable and have actually seen areas I've applied it expand and contract substantially...so definetly not stable!

Avoid the 'traditional' white beaded foam...as Jeff states, a huge mess.  I originally chose this as it was more convenient given its all the local hardware store had, but I definitely go out of my way for the 'nice' pink stuff now!

[KenS]

I'm a fan of foam too.  I prefer to use a knife and rasp (a Stanley Surform Shaver) to shape foam, rather than a hot wire cutter, but that's a matter of taste. Just keep a vacuum cleaner handy if you carve it that way (I wear a dust mask too; don't want that stuff in my lungs). And while hot wires are fine, don't light it on fire, the gases it produces are really toxic. 

Jeff said most of this, but I'll add my two cents:

The "stuff in a can" is expanded polyurethane. Some older types would emit formaldehyde when curing, which isn't good for your lungs, but the modern stuff is supposed to just outgas a fluorocarbon gas; bad for the ozone layer, but irrelevant to your lungs unless there's enough to displace oxygen.

The difference between the white sheet foam and the others is that white foam is usually Expanded Polystyrene (EPS), which is basicaly small bubbles of PS that contain gas and form beads (which leads to the term "beadboard").  There's little structural strength between adjacent beads so the foam breaks or crumbles easily.  That makes it a good shock-absorbing packing material (packing peanuts are made from it), but not a great structural material.

The good stuff (which is often pink or blue, I believe for branding purposes rather than any functional reason; it can be white) is Extruded Polystyrene (XPS), which are basically threads of foamed PS extruded into sheets.  The threads are stronger (along their length) than beads, which makes this version a better structural material.  It also makes it hard to cut "across the grain", which is important to consider when using it. According to this site, "styrofoam" is actually XPS, but I've heard the term used more generally for any of these.

I think the recommendation against white foam comes from the fact that it's hard to tell if white foam is EPS or XPS.  Woodland Scenics foam, for example, is white but isn't "beadboard" and appears to be XPS.

[Martijn Meerts]

When doing my first layouts, I used foam quite a lot, but at the time the only thing easily available was the "beadboard" stuff, which I started to hate after a while. These days I use mainly wire mesh and plaster (cloth).

I'm still not sure they have any of the good XPS at the local hardware story, but I'd definitely like to try it. It's likely a lot easier to get nice shapes than using some wood frame with wire mesh on it :)

[Bernard]

I also like using foam board. I will say that it does matter which brand you buy. I found that the "Corning" brand foam board is a not as thick as another brand I used....local Hardware store had a green foam I used which was a little thicker and wound up having to buy the same foam board when I did future expansions. What I do like about the Corning brand is that it has an interlocking groove in it so it is easy to line up a layout if you decide to expand in the future.

I tried the expanding foam in a can and wasn't totally happy with the results.....you can't control the expansion and if you put a heavy layer, the middle doesn't always cure.

Building a mountain is fairly easy with foam too.....just build up the foam in layers using "Liquid Nails for foam" as an adhesive, and after it set just carve away to form the desired shape of a mountain. When you're finished, use hydrocal cloth to set the mountain, stain or paint it and then add ground cover. Oh...as us cut and/or sculpt the foam I recommend having a vacuum handy....it does get messy.

[KenS]

Something that Inobu mentioned several months ago on the thread about using foam on his layout just caught my eye and reminded me of my own experience: foam dimensions are only approximate.

When I started my current layout, I bought three sheets of 2' wide, 8' long, 2" (5cm) thick foam.  All three were the same brand, bought from the same store within a month of each other. All were stored in the same way (standing in the corner of my basement). More than a year later I ran into clearance problems with the subway line at one point, and discovered that that "two inch" piece of foam was actually 1.75" thick.  I measured the three pieces and found they were three different thicknesses, between 1.75" and 2".  So if you use foam, don't assume the thickness dimension is correct if that's critical to your use.

I haven't had any problems with width, although I think one of the sheets may have been 1/4" (6mm) shorter than 8' (244 cm), a pretty minor error.

For glue, I usually use yellow carpenter's glue although it does form a very weak bond with foam (it can't withstand any significant side impact, so only use it if the foam is protected at the edge).  That's actually been helpful when I needed to remove a chunk to change the layout.  I've used Liquid Nails for other things, but haven't tried the "for foam" formula with foam. Be aware that some glues (and things used in place of glue like silicone caulk) and paints contain solvents that can damage foam, so verifying that glues (and paints) are compatible is important, and can be hard to do sometimes.  If all else fails, test with a scrap of foam.

I usually coat the top level of my foam with plaster (one of the woodland scenics materials, I forget the specific one) or plaster cloth as a base for paint, but I've also used latex interior housepaint (I haven't yet tried gluing scenic materials to the painted bits though, so I don't know how well that's going to work; plaster is more porous, and provides a better surface for typical scenery glues to attach to). The housepaint is particularly nice as "temporary" scenery to get rid of the pink color on areas that aren't ready for final scenery yet. Dark green makes a passable "grass" color.

[cteno4]

inobu's post on his foam covering experiments are also interesting for this thread:

http://www.jnsforum.com/index.php?topic=5518.new;topicseen#new

after his tests i now am going to pick up a tub to play with. always great to have plenty of options!

ive seen some variation in thickness that ken reported, maybe not quite as much but never really carefully measured it. on the 1" we saw about 2mm at most variation in thickness when we used it for the tops of the first jrm layout module boards. i built wood frames the foam set into and they were built with jigs so all the same depth in the frames and some of the modules the foam wanted to poke up 1-2mm and in a couple of place a fraction of a mm low. as soon as i noticed this happening i just gave the ones sticking up a whack with a mallet at those areas w/ a big hunk of 2x8 on top of the area and it pressed the wood blocks behind the foam into the foam enough to get the foam flush before the glue set.

for glues i have used all sorts of stuff over the years from white and carpenters glues to even using some left over polyurethane mixture that has a low amount of catalyst in it when we were bonding some big sheets at the aquarium that had irregular surfaces at the joint (the polyurethane expanded to fill all the void, but was high density (ie low foam/gas) so didnt explode the joint). pva glues do take a bit of time to dry though so you need to let them set a day or so and use some skewers or weight to keep things positioned and the joint tight.

folks have reported that using gorilla glue is a fast way to join pieces. simply spread a thin coat of gorilla glue on one half then give the other half a fine mist and press together. water activates the polyurethane gorilla glue and you get a fast bond thats pretty tough.

ive used the liquid nails and works well, but hard to get an even bond if you need it as the glue is really thick and thus does not spread out well. it also is hard to get it to flatten out with pressure. sets up w/in like 30 min. its meant to slap up foam insulation boards into a wall quickly and only requires a bit of adhesion here and there to hold it in place, thus the thick consistency so its not messy.

folks also use the water based contact cement with good luck (although the first formulations of the water based contact cement i had rotten luck with in other projects, but reported to be better now!) But with contact cement you have one shot at your positioning!

the foam wire company sells a 'special' foam glue that they say does not interfere with cutting thru with the hot wire cutters, but matthew just reported that when he used it it did noticeably cut different than the foam. i did gobs of foam cutting at the aquarium years back (mocking up rock features for tanks and exhibits) and cutting thru the glue layer was never and issue really with any of the varied glues i used.

cheers

jeff

[worldrailboy]

quite a lot for me to read already right now but thanks, I'll try catch up when I can...new replies by then or not :-)

I always did wonder how to be able to carve painfreely when multiply layers of foams were needed, guess I solved my upcoming issue hopefully

[cteno4]

using hotwire foam cutters is one way to quickly carve up extruded polystyrene foam. like i said there are cheap ones to play with or you can get fancy (but expesive) ones from http://hotwirefoamfactory.com, or if you are into it roll your own. also sharp "ginzu" serrated type knifes work well. its messy, but really rough rasps and 40 grit sand paper also work well, just do it in a contained area and be prepared to suck like mad with the vacuum afterwards!

we had a hollywood guy come into the aquarium years ago when we were mocking up rock work with foam. he give us all sorts of fun tips to get cool textures using different methods. sandblasting was one you could get different textures with different sandblasting materials. was fun but really really messy! hollywood folks build huge rock sets in no time with foam and then cover with a gel coat material that creates a hard shell, then paint. was fun to watch him do a bunch of stuff quickly to show us techniques.

cheers

jeff