It's great for making RC

It's great for making RC electric airplanes fast and cheap. They call it FFF (Fan Fold Foam).

If you're looking for strength, ... it's not very good for that. If you have to put a load on it, laminate it vertically, not horizontally. I wouldn't use if for anything bearing weight, especially across a span.

On the other hand, it's wonderful for shaping subtle land contours. Much less shaping and sanding to do. there's no excuse for a "plywood prairie" when you can use that stuff for rolling hills. You can also use it to build "egg crate" style frames under larger landforms, and then cover them with foam too. Faster, lighter, easier, and less messy than dealing with plaster.

I wouldn't give up on the thicker foam yet, though. Look at a real builder's supply instead of one of the big box home centers. It's still out there.

Fan Fold Foam

Back when I sold it, granted, that was 15 years ago, I thought it had a cellophane type material on both sides that allowed to to be bendable?  Which would not work for what we do in model railroading.  Check it.

I could only find 1/2"

I could only find 1/2" (closer to 5/8") Pink two weeks ago at my local Home Depot and it had a very thin cellophane membrane on both sides, but it peeled off quite easily. 

Thanks

Sounds like it may accomplish my main purpose, since I am not looking for strength, that's where the 1/2" plywood comes in under it. My only other concern is if it is too 'spongy' under the cork under the tracks.  I am guessing it will be fine - but nothing some experimentation with a small section can;t help me answer.

-Ed

"if it is too 'spongy' under the cork under the tracks?"

     I've heard of foam roadbed being too soft to clean the rails without bending them and disturbing the ballast but I've never tried it myself. If you plan to use cork why add any foam under it, just cut another layer of plywood to roadbed width and glue it under the tracks instead of foam? Foam is great for shaping contours but I see no reason to extend it under the tracks if you already have plywood under there. The best argument for foam under the tracks would be a layout using thick foam sheets for the benchwork and no wood roadbed under the tracks but that's another story. ...DaveBranum

I used it for a portion of my

The reason I want the foam is

The reason I want the foam is so I have some depth I can leverage in yards and trackside along the line as well as being easy to carve transitions going into and coming out of grade changes. The 3/4 inch I wanted amounts to 10 scale feet which would be plenty for ditches and culverts or by road crossings. It also gives me more wiggle room on the plywood cuts for the plywood to be a bit wider whereas if I use plywood directly under the cork then to get the trackside features I have to be far more precise.  My woodworking skills/tools are not the best so the foam is my fudge factor.  

I will play a bit with what I got on my first section where the benchwork is already built, but I may shift to the thicker foam for the remainder of the layout.  

Thanks,

-Ed

Rigid sandwich?

For those who know more than I do, here's a question:

If I were to take this 1/4" foam and bond a layer of heavy craft paper (the thick brown stuff that comes in a roll) to one surface using a foam-compatible adhesive, and then bond 3 of these layers together, would the resulting 3/4" thick composite sandwich be significantly stronger than a solid piece of 3/4" foam, while still retaining comparable light weight properties?  In other words, could I use it as the top surface for a layout without fear of it sagging or flexing,as might happen with foam?  Or would it just be a lot of work for no real benefit?

"The reason I want the foam is so I have some depth"

    Yeah, you definitely want to have some depth for scenery so you can dig out ditches etc.  My suggestion was to cut 3/4 plywood to one inch wide or whatever width would fit under the track and glue it to the 1/2 inch plywood roadbed you already have installed. One the roadbed is elevated you can fit foam along side it to fill in the scenic areas. I built a layout this way a few years ago and it was not too hard, the foam doesn't have to be a great fit to the edge of the roadbed as the gaps can be filled with putty. The other way to go would be to just use the available 3/4 inch beaded foam like you had originally planned. I've used it before and it's pretty strong if it has wood backing and the beads are not a problem when shaping if one just covers the surface with sculptamold to fill in the roughness after shaping the foam ...... .Dave Branum

There was recently an article

There was recently an article about Tony Koester using 2 layers of HO cork roadbed under track on his NKP and FFF for bringing contours up and cutting ditch profiles.

Having struggled recently with trying to decide what to use for roadbed, etc on HCDs, this sounds like it might be a good thing to try.

I used it for roadbed.

I used it on my HO layout for roadbed. It is glued on the OSB base and has worked great for over 7 years now!

I used a trammel and marked my curves with a sharpy marker, making a line every inch. I cut every other line, leaving the skipped line as a track center line for laying track by. For straight I just cut the foam into 1 1/2 wide strips.

I glued it down with Elmers Glue All and attached the track with latex caulk. It went fast and easy.

IF I was going to build again, I would add a layer of 1/2" foam between the OSB and 1/4" foam to make a better ballast profile. Otherwise its worked great and easy to change if needed.

I see no reason why you couldnt use more than one layer but it would become more labor cutting all the strips.