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I decided to go the plywood (3/8") and rigid foamboard (1/2") route for my tabletop. My question is; since I will have a two level design (elevated so the main passes over itself in a 'J' shape figure eight pattern), should I adhere the foamboard to the plywood first, then cut for the elevated portion, or cut one or the other first, then cut the other before gluing? This is cookie cutter design.
My concern is; if together, the mess of sawing through both the foamboard & the plywood then supporting with the levels afterwards from the grid work underneath. I'm using the Lynn Westcott method. The room/layout is 9'x19', the layout is N scale and it is a double track main with a hump yard.
Interesting. Ok, then I styarted to layout my layout on the plywood, which is primed white. Problems are, the grain raised and the surface is like sandpaper, making short work of the pencil. Anyway, by doing so, I'm basically doing double work since all the layout will be covered by the foam after I figure out where the cuts are in the plywood.
As popular as this appears to be, I'm surprised I haven't see anything on this.
I glued the foam to my benchwork first (only the tabletop portion) and then used a sawzaw with a fine tooth metal blade and trimmed it using the edge of the table as a guide, makes a surprisingly nice cut and after all when it's said and done the foam edges will be covered by your trim or fascia.
For my N-scale layout, I also used the cookie cutter method, with foam on top of a plywood base. However, I made all of the raised areas from foam alone, no plywood. The big advantage is that I only had to cut the foam, not the plywood.
I have two layers of foam. One is glued to the plywood and forms the base of the layout. The second layer of foam is the cookie cutter layer and is glued the the underlying layer of foam only in selected spots.
A photo or two will help.
I used foam blocks as risers to support the raised portions of the cookie cutter layer. The foam seems very flimsy until you start adding the risers. Then it is quite stable.
Here is another photo showing some of the foam risers.
I used 3/4" foam for the two layers, and it's plenty strong enough. I think 1/2" would work if well supported.
