Shelf Layout near ceiling

What is the best way to build a shelf to support an HO train to run around the ceiling in a family room. Plywood, foam-board? Also, what is the tightest curve I can make. I am planning on using flex-track and figure its about 150ft of track around the room. Any help would be appreciated.Also what about shelf brackets?

Tightest curve: will depend on what you’re running. A train set will tolerate 18" radius, but you may find that later add-ons require something larger. If you draw it out, you’ll find that wider radii don’t require much more space on an inside corner (the usual corner in a 4-walls room). Outside corners are another matter.
I would avoid foamboard for the shelf; it doesn’t have the support. Plywood by itself (at least 3/8", preferably 1/2") would be stiff enough, but you can’t put track spikes into it without damaging the track; you need a softer material like cork or rubber roadbed or homasote™.
Aim for supports every foot or 18"; look at how much your plywood bends. I’ll let others suggest what to use for supports. Does it have to look good in the family room?
I built my layout about shoulder-high supported on IKEA book shelving. (width 12" to 18")
–David

Ive seen "L" brackets used to hold up 1/2" plywood(find the studs!)and then 3/4" blue or pink foam board on top of your plywood base.The thick foam board gives you the media in which to cutout ditches,gullies,drainage pipes under tracks,etc.Carve out anything that makes you grin!It also deadens the sound you really dont want.I`m now installing foam on my benchwork with 3/4"(approx $8.00 for a 4X8 sheet)and have decided to install another 1/2" on top of that,which really is not necessary but will allow me too cut deeper into the foam layer and create deeper gullies or whatever. Jerry

Thanks Jerry,
I will take your advice and use some blue board on top of the plywood. My wife asked me about the sound and the foam and cork road bed should probably help.

Thanks David,
I’m going around corners in the room so I will try an 18" radius, I won’t be running a real long train probably 8 to 10 cars. My studs are 2ft on center so probably the 1/2" plywood would be better. Oh yes it has to look good says the wife!