Thanks for bumping this or I might have missed it.
As you know from my thread I am contemplating some changes.
Also recently there was some stir in another blog that basically said to not use foam
(highly contested viewpoint by the way).
As I understand it, Ken Patterson had talked about how his foam sub-roadbed was shrinking (presumably from out-gassing).
A lot of talk about the loose tolerances for foam, etc.
My take? A lot of hog-wash.
I respect Ken Patterson but he uses all kinds of nasty and unusual adhesives in his construction.
I would never use Gorilla Glue on XPS foam for instance.
Personally I think that just because the foam doesn't melt away into a glob doesn't mean the stuff isn't attacking the foam.
He liked the Gorilla Glue because when he tried to separate the two pieces, the foam broke instead of the glue bond.
To me, that means the glue broke down the cellular structure of the foam, not necessarily a good thing.
Anyway, I like foam construction.
My Yellow Creek Western was built on a single sheet of one inch Foamular 150 (the lowest density pink-stuff).
About 90% of the layout has an additional half inch sheet of the same stuff glued on top using Woodland Scenics Foam Tack Glue (what I had on hand).
The "valance" is just light-weight spackle kind of sanded and painted with water-solvent paint.
The only beams or supports are 1x2 pine glued to the bottom with the same glue.
There are three "main" supports. Those supports sit over the screw holes on an old IKEA Gallant desk frame,
and they are affixed by 2 wood screws in each support.
I did add short 1x2 stringers to the ends that are glued on,
but they are just attachment points and really add minimal rigidity to the structure.
Here you can see two of the three main supports.
They are unscrewed from the frame in the photo, as I was removing the layout from the frame when the picture was taken.
I built this seven years ago and it has proven very rigid.
I do think that the paint on the sides and bottom help make it more rigid as well as slowing off-gassing.
I even attached the servo mounts to the board with double-sided tape and added two wood screws for peace of mind.
They have been flawless.
When I was fooling around with various L-Girder benchwork, I smashed one of the servos into the frame.
The plastic servo mount broke but the rest of the mount stayed attached and aligned on the benchwork.
I would not hesitate to use all foam for a layout.
I'm actually considering pulling off the1x2s and just gluing brass screw inserts directly into the foam.
I recently measured the layout and it is level.
If I put a 2 pound weight on the far left edge it deflects down about 1/32" and I'm sure if I tried I could snap it off.
Would I leave it like this at a show? No.
At home or with other MRRs, it's fine.
Interesting comment on the epoxy.
I have been considering epoxy for the valance when it is "all done" making it a kind of DCC surfboard.
I don't mean to say that having the foam break first means it is attacking the cell structure, only that it can be.
There is a reason that Ken Patterson is seeing shrinkage and most other users don't seem to see it, or at least not enough to worry about.
whatever "forum" put down blue or pink foam for layouts...
well...my old Mogollon Railway was built upon 2" blue foam and was outside for years.
My current layout is 2" blue foam and it should last a long time also.
Maybe I am just a newbie, I have only been using the foam for layouts for 20 years now.
I suppose those guys know better than some of us do! LOL
BTW- I use epoxy to bond most everything concerning foam, such as facia on the edge...
I put 'poxy in dabs with titebond yellow glue between the dabs and then tape the masonite to the foam with blue or masking tape until it dries.
Never had any problems.
Matter of fact, I wouldn't build a layout without foam as the base.
Ahhh but what to I know...I have only been building layouts for...mmm...60 plus years.
____________________ It doesn't matter if you win or lose, its' how you rig the game.