Foam insulator on top of plywood

[Steffen1601]

Hi All,

I am starting to build a model railroad again. I have seen some videos and and posts that it is recommended to use a foam insulator sheet on top of the plywood to make scenery easier. Is id indeed recommended to use foam insulator? What are possible negative side effect when adding foam insulator on top of plywood?

Thanks!!! 

[BigDaddy]

I see you are new to the forum, to the forum.  Your posts are delayed for a short while, in moderation.

Is foam available where you live?  Here in the US, it is not available in the warmer states.  We call it foam insulation.

Is it recommended?   Well it is one technique of many.  It's light, in 2" thickness it is sturdy enough for a model railroad, but not so sturdy, that you can crawl across the top.   In the thicker insulation, you can carve it to achieve, what I call negative elevation, rivers, creeks and gullys.  There is a guy on youtube, Ken Patterson, who uses 4-6" of foam insulation.

Even with all that foam, it is still light enough for him to move his modules outside and do his photography.

Creating grades on your track is much easier with a plywood cookie cutter approach.  Patterson is able to create grades with an electric chain saw.  I have no idea how he cleans up that mess of staticly charged foan particles and dust.

I built 2 modules with 2" foam and 1/8" luan plywood.  I was going to use a thicker plywood, topped with what we call Homasote, a manufactured product made out of paper I think.  Home Depot refused to cut it and I had no way to get a 4x8 sheet home so I went with foam

 

[MapGuy42]

Indeed, it is one of the methods of a sub-roadbed.  I have exactly that on my 4x6 layout.  I used 6 24"x24" "craft panels" of 1" foam insulation, which were available at my local Home Depot in the Sacramento, CA area.  Before installing, I cut a creek into the corner of one panel, so that the actual plywood is the creek bed.  After installing and track was laid, I carved drainage ditches into the foam with a rat-tail rasp.  It is quite handy for vertical variation.

Welcome to the forum!

[cowman]

Welcome.

The major derawback I see to foam is the mess it creates when you work with it.  Snap cuts aren't too bad, but sanding or using a rasp type tool, creates a lot of mess.  I like working with foam and have found that using an anti static spray and keeping the shop vac close at  hand, keep the mess managable.

Good luck,

Richard

[PC101]

Steffen1601

Hi All,

I am starting to build a model railroad again. I have seen some videos and and posts that it is recommended to use a foam insulator sheet on top of the plywood to make scenery easier. Is id indeed recommended to use foam insulator? What are possible negative side effect when adding foam insulator on top of plywood?

Thanks!!! 

 

If it is available where you live, good. Negative side effects? Nothing you can't learn to work around. I use 1/2'' blue board under the track and on top of the 3/4'' plywood. I use anything from 1/2'' up to 4'' on surrounding ''low'' land and up to 12+'' in the ''high'' land. Now if you use undertable switch machines, you may need a longer and stiffer throw rod. If you use ground throws, then you will need longer nails to fasten the throws down or install a block of wood under the throws. Keep a vacuum handy. If you use a hot foam tool, it will stink and the vapor is not good for you. Keep a small fan running next to you. You may have ''strings'' when hot cutting foam and will need to pick them off of the work. You can use kitchen utensils to work the foam (+).

I have used over the years of layout building, ceiling tile, Homosote, card board strips, plaster gauze, newpaper in plaster, window screen and I will not go back as long as I can find for free (dumpster diving) or at local big box store. You may need longer drill bits to get down though the foam and sub roadbed to run wires. I do use ''Sculptamold'' over foam (+). I'd say I am 95% sold on foam, it's solid, not hollow like "hard shell". If the mountain is too high, just saw some off, opps to short now, just glue more foam on top (+). Plant trees and brush as fast as you can make them, poke and stick(+). Telephone poles, poke and stick, people with a drilled foot and a wire inserted in that foot, just stick it in the foam. Don't like where you put them, well then pull them up and restick somewhere else(+). Seems like there are more (+'s) then (-'s) with foam for me. I model the PENN CENTRAL so I have valleys, hills, gullys, rivers, creeks, rock out crops, cuts, fills, small towns and industry. There is very little flat ground off the right of way.

Stay away from the foam that is made up of white tiny balls, it is flimsy soft and breaks easly. Extruded foam (blue, pink and now I see green) is the best to work with. Some 1/2'' sheets had a film of plastic wrap on it, remove the film. 

Edit: I do use the ''Woodland Scenics'' foam risers/grades with cork or that black sticky roadbed stuff on top of the foam. 

             

[rrinker]

 2 layouts ago, I used foam, no plywood. Basic dimensional lumber frame, with the foam glued on top. Worked fine. No issue. Last layout, I used 1/4" plywood underneath to give a way to screw switch machines to the bottom. Also worked just fine.

                                      --Randy