My layout is 1/2" plywood over 2’ x 4’ framing, plenty strong to support locos and rolling stock.
In a remote portion of the layout, I have a 24" x 24" pop up hole, also framed by 2’ x 4’ lumber. Currently, I have a 24" x 24" piece of particle board covering the pop up hole, and a three track back shop sits on top of the particle boaerd, again plenty strong.
But the pop up cover is too heavy for my liking, so I would like to replace it with a 24" x 24" piece of 1/2" thick of rigid foam insulation board. Do you think this would be strong enough to support as many as three steam locomotives?
Yeah, I am thinking that you are right about 1/2" foam board flexing. Maybe 1/2" plywood is the answer, as it is lighter than particle board. I chose particle board originally, thinking that it would lay flatter than plywood. But, particle board sure is heavy.
No. I have almost the same layout as you do…1/2" plywood with 2" foamboard and then 1" blue board (St…foam.) It completely holds me up without even a dent in the top piece. The weight of 4 locos is considerable and without the plywood base the locos might/would be disasterous. A suggestion here…take a 2" piece of foamboard the same size as the opening or the piece you are actually going to need in its place and add one loco. Keep adding until you feel it is unsafe. My guess would be 3 locos. If 4 locos make the foamboard sag you have gone too far. But what exactly do you want? Being safe and still using the plywood and foam? If your answer is safety and the possibility of locos falling off the layout you have your answer. Plus a 2 x 2 ft piece of plywood is cheap and light.[C):-)]
Build a grid of 1x2’s that will fit into the hole, then glue and screw (use some big washers) your 1/2" foam to the top of it. A 1x2 box with a cross member (or even 2) with the foam on top will be more rigid and lighter than a 2’ square of plywood.
And btw, I think over time 1/2" plywood will sag with a 2’ span.
Why not start with a 24x24 2" thick piece of foam. You can cut a lip around the edge that’s only 1/2" thick. That way, you’d have the full rigidity of 2" foam over the expanse of the opening and the flush height of 1/2" you’re looking for.
I would use this…Birch Plywood, cut off two ft. I would rather use Baltic Birch, much stronger and it is 9ply, but Home Depot don’t carry Baltic. What they carry, I believe is 7ply, lightweight also…the heck with foam.
My high school HO layout (6’x6’), and; later N Christmas layout (4’x4’). Each used 2’x4’ open grid benchwork on 1"x4". The base was on 1/2" homasote, not foam, and each layout was plenty strong to lean on – I wouldn’t attempt “any lean” on foam.
Frame your lift-out with (nominal) 2x3 steel stud, and put the last part of the 10 footer (bought at Home Depot) across the center. Put just enough 1/2 inch ply ‘cut cookie’ in place to support the track and building, then fill the rest of the space with foam.
Believe it or not, the steel is lighter than equivalent wood. It also comes without checks, splits and knots and simply disregards humidity. Finally, all your fastener needs can be handled with the tiny screws normally used for steel stud assembly - no long wood screws into end grain.
Tools required? Tin snips, vice grips and a power drill with crosspoint bit. Lacking tin snips, you can do your cutting with a hacksaw.
Chuck (Modeling Central Japan in September, 1964 - on steel stud benchwork)
I have never used it, but how about Gatorfoam (sp)? I have seen it at shows, seems quite strong, is lightweight and comes in 1/2" as well as other thicknesses.
I can order it at my local sign shop, some things can be ordered in 1/2 sheets if he uses it for other things.
I used 1/2" Gatorboard for a view block. I believe it may be slightly stiffer than 1/2 foam insulation board but I would be reluctant to trust it with three steam locomotives.
What about using millwork strips as stiffeners to either Gatorboard or extruded foam? I suggest gluing something like 1/2" by 2" strips on edge–one single piece diagonally from two opposite corners and two half pieces from the other corners to the center point. Where the strips meet I would attach (glue & screws) a 6+/-" circle of 1/4" plywood or hardboard to eliminate buckling of the two half strips of millwork. I think this would still be fairly light weight and wouild provide something to grip when removing the cover.
LION does lots of things because he doesn’t know better. After all, what does a LION know?
If works, is fine, If works not, fine too, him will change it…
LION made many small table-lets and then could locate them in the right place and support them in the corners, instead of supporting something every 16 inches or so.
Don’t make your supports any closer together than 16". That is what it takes to get a drill inbetween the supports, just incase you need more holes in your wood.