After building my plywood and 2x4 framed table I now have to decide if covering the whole top with 1" rigid insulation is the right way to go. My LHS says to do it, but I’ve also got several books that show just using a good plywood base as the starting point. If the top is level, and it is, what are the benefits of the insulation? If you have put down insulation would you do it again? If you did not put it down, and had to start over, would you insulate?
Many people like to use it as it is simple to create below rail details like culverts and drainage canals. I personly use the cooky cutter with plywood and design it in ahead of time, but thats the catch. Look ahead at what needs to be done. How will you attach ground throws, under table switch machines,wiring,etc… There are solutions out there and I am sure many will chime in on this.
if i was doing it over again and i was in ho i would use two layers of 2" foam over the plywood top. this way i would have space to tunnel under the track for roadways, rivers, track and anything else that would normally pass under the tracks. i model in n scale and use 2 and 1/2 inches of foam and have several areas to tunnel under or carve out valleys and rivers as my layout is level with no grades. if you use under track switch machines like peco’s it’s easy to carve out for them to fit. if you use hand throws like caboose industries i glue in a 1/4" thick piece of wood like from a paint stirrer or a wooden yard stick near the throw bar level with the foam and then add a piece of cork.
The real advantage of the foam insulation, is the ability to easily add below grade terrain features.
All you need is a surform tool and a shop vac to grind out a pond, a river bed or a few ditches. I used a large half round file to cut ditches along my mainline. Depending on the area you’re modelling, you might consider 2" foam for deeper cuts in the surface for more varied terrain.
Holding the shop vac hose near the tools as you’re grinding out the shapes keeps the area clean and minimizes final cleanup.
As many will tell you, the foam isn’t as quiet as homasote, but it is much easier to work with. Cutting homasote with a power saw produces fine powder that gets everywhere.
The primary benefit of adding foam insulation board at this point is to provide a relatively easy way to get scenery that is below track level. Often, the foam insulation will be installed in thicknesses up to 4" (2 - 2" sheets glued together) to provide more depth for carving down. The foam is easily carved out for features like ditches, ravines, stream and creek beds, and so on.
If you were starting from the beginning, the blue and pink foam has quite a bit of rigidity on its own, especially in 2" thickness, and can allow you to reduce the plywood to 1/4" or eliminate it altogether for a lot of weight savings. Note that reduced weight has no benefit until you go to move your layout.
An alternative way to get below track level scenery with plywood table tops is called “cookie cutter”. When you have your track locations established, whip out your handy jig saw, and cut away the plywood where it is not supporting track or structures. Raise the remaining plywood on risers and cleats, and now you have space between the top of the framework and the plywood subroadbed for your below track scenery. Westcott’s book on model railroad benchwork (available on this web site) shows this tried-and true approach to layout construction in great detail. I’ve used cookie cutter in conjunction with plaster over window screen scenery, and found it very easy to create the mountainous and water front scenery that I wanted. It’s just not lightweight.
I did use foam for a Christmas 3 rail O layout. I framed 1.5" foam with 1x3 lumber, and kept the foam flush with the bottom of the 1x3 rails. I glued 1/4" plywood on top of the foam to enable the tree to stand on the layout, and allow the Lionel track screws to work. The result was a very light, easily handled layout that could be set anywhere, and could be walked on if need be.
The next time around - and I’m in the planning stages of my new
I have used foam…And would do it again!
The simplicity of creating topography (cuts, fills, ditches and so on) has been great! Every area of my pike has at least one layer (one inch) of foam, with hills cuts and grades, with as much as an additional six to eight inches in places. I have cork roadbed glued to the foam and the track glued to the cork…Before ballasting. It has all worked really well.
I have had no problems with wiring feeders, just making a hole through the foam, a lot of the time right under the track.
OTOH, “spidge” is correct in his statement regarding under table switch machines. I don’t have any, relying on ground throws and a “chock cable” method on some of the “farther away” turnouts, but I would suspect they would be VERY difficult to install and make work properly.
Your layout sounds like mine ( or what mine will look like ). I’m planning on 1" of foam over 1/4" plywood, all ground throws, cork glued directly, etc. I will need alot of elevation change as here in N.H. nothing is flat! Foam seems to be the easiest to model this with.
Thanks.
This is strictly a personal opinion - and, as usual, I’m something of a contrarian.
The usual reason given for using foam over plywood, ability to carve out below-tie-level scenic details, indicates to me that such details were unplanned, afterthought, additions. My planning allows for them, so I have no problem building them in. (I plan in reverse, on the grounds that the mountain, the river and its tributaries and the settlements were there first and the railroad came through later.)
Also, since all of my visible trackage not in station areas (and some that is!) is on grades, I don’t use sheet plywood tabletops. Everything is cookie cut, and every piece of the cut cookie that isn’t going to support track or provide a toehold for scenery is removed.
That said, I DO use foam - in the form of track base (in yards and stations) and ballast-form roadbed (under plain-Jane track.) The foam I use is fan-fold underlayment, thin section material meant for use under vinyl siding. Others use sheet cork and cork roadbed for the same purpose, but I have learned (the hard way) that cork has a finite, rather limited lifetime here in the Dessicated Desert.
I also like thicker foam for scenery, where the scenery doesn’t support trackwork.
Just my [2c]. Other opinions are sure to differ.
Chuck (modeling Central Japan in September, 1964)
There have been some who didn’t use any plywood and just had two sheets of the 2" foam
Plywood by itself is noisy. So is the extruded foam. They are essentially single density materials (I know, plywood has layers of varied density, but its construction still makes it resonate) that can act like sound boards. HOwever, when glued together with caulking, you make a sandwich of two outer densities held together by a third, even if it is a thin third, and the result is usually going to be much more quiet than either of the two outer layers by itself.
That’s one. Secondly, as the others have pointed out, foam can be scored and carved so that it resembles, when painted and with ground foam and trees stuck into it (oops, there’s the third that crept in there) real landscape. The best method, as far as I am concerned, is the much more labour intensive hardshell with lattice underlay, but shaping layers of foam is a close second with skill development.
If I were thinking about a very flat surface and I had no interest in carving out some relief, I would omit the foam and just screen and sprinkle real dirt onto the plywood surface. I would mix it with some plaster of paris and glue it all to the plwyood with a yellow or white glue wash mixed with a few drops of dish detergent. In fact, to be honest, I placed a single layer of yellow 1/8" vinyl underlay against the plywood for my yard, and then glued the dirt mixture to the underlay. It turned out well and is dead quiet.
fwright has raised a very good point about access. I used a 2" sheet as the base of my layout with a 1" sheet over that. This allowed me to incorporate a system of keys to position my above grade scenery.
I have two mainline tracks and six staging tracks behond the scenery as well as a tunnel.
By cutting a square through the 1" foam, I was then able to glue the upper scenery eliment to the squares and create a key to position the scenery in place without having to glue it down.
I applied Sculptamold over my styrafoam. At the joining points, I used plastic wrap to prevent the Sculptamold from fastening the pieces together. Once the Sculptamold starts to set the plastic wrap can be removed.
Here’s a picture of the mountain and tunnel in place.
Here it is removed.
You can just see some of the staging in the second picture. All of the scenery covering staging is removable for maintenance.
Carving all of that Foam? WHY?
I use 3/4 inch plywood sub roadbed on 4 inch risers on L-Girder open bench work. This allows for a scale 30 feet of clearance for underpasses and culverts. If I need more clearance, I use higher risers.
The terrain trackside can thus rise and fall over or under track height in a realistic manner.
No messy carving of foam, not to mention the time and expense to install it. After the track is laid, hard shell scenery accomplishes the terrain without any messy and time consuming carving or sculpting of huge layers of foam.
Rather than a huge panel of foam, I would at least suggest you consider using the cookie cutter method of producing road bed only where you want it from a sheet of plywood and adding cork roadbed.