Using 3/8" plywood with 1/2" rigid foamboard over it on a around the wall layout in N scale (34" table depth) using cookie cutter construction, is this a problem with the flexing, expansion & contraction of the plywood in a non temperature controlled basement? Temperature varies from 55 to 75 degrees, but humidity has varied from 45 to sometimes close to 100%, but there is a dehumidifier, so high humidity will probably be 75 to 80%. I was concerned with overall weight of the plywood and thickness of the foamboard when it comes to work with linkage of turnouts. I also have no plans to 'dig down' below the top of the foam for scenery reasons which is why I choose 1/2" over 1".
Why dont you just make your benchwork with L-girder construction and then use 2" foam directly on the L-girder. It is lightweight and no worries about flexing either.
I did use L girder construction, but I had/had no intention of using just foam, especially 2" due to it's thickness and possible issues with turnout control.
You can get away with 1/2" foam over 3/8" plywood providing that the plywood is Birch. Normal pine plywood will eventually deform and warp. My best advice would be to us !/2" Birch. As to the 1/2" foam. Why so little? How will you build underneath your track level? Streams, creeks, rivers, etc. In real life are not almost all railroads built above the surrounding land levels? Go with at least 2" of foam and this will go along way toward achieving something a kin to realism. Jim:eh-smiloe:
Another option is 20" shelf brackets screwed to studs through sheetrock, topped with 1x2s for length and support, then 2 sheets of 3/4" foam board on top. No worries with expansion from temperature or humidity because the foamboard just lays on top of the 1x2s, allowing the brackets and 1x2s to move as they wish.
You are the 1st to state this. I did prime the wood, won't that solve that problem? I don't and never planned on doing so. Also, the price was right; $7.50 per panel. Hytec; I have seen your photos, what I did is more than sufficient due to the depth of the table. I did a push-up between each support pair with no or little issue. 200 lbs between the pairs tells me I don't have to worry about that aspect.
I haven't used 3/8" I did use 1/4" on a couple of modules and they transfer sound like a drum. I think thicker materials help deaden the sound, but your foam may help. I generally like to use 1/2" or greater ply because it gives me something that I can screw into for mounting switch macines, terminal blocks, etc. BTW, great looking brackets and I like that panelling on the lower half of the wall. What is it?
Deformation of plywood sheeting also depends upon the spacing of your support pieces. The further apart, the greater a chance of warp.
I measured my "T" risers and they average around 12" apart from end of the T to end of the adjoining T.
Here are pics of the risers. Some will have to move due to turnout placement. (Great way of using up scrap wood.)
Twelve inches is plenty close together for strength. Chance of any real deformation is very minimal. As long as both lumber and ply are well dried and room humidity is low, I'd not worry much at all.
I'm also hopeful 1/2" ridged foamboard on top will help. Humidity in the spring and after it rains approaches 100% w/o the humidifier and 70-80% (highest amount) with, depending on how much I want to spin my electric meter.
The reason I didn't go with just 2" foamboard (seems to be the popular thing to do) is I have no plans on sunken scenery (streams etc.). If I need to raise any area, I can always add a piece of 1/2" to the existing base.
I think the other issue with just using foam is that it makes attaching any sort of switch machine exponentiallly harder. I am using 3/8" plywood with 1 1/2" foam amd Bluepoint controllers. They are easily able to deal with this thickness even set for minimum throw.
Which is why I wanted to at least use plywood. The solution I have read was glueing small pieces of thin wood like material (Wucaboard in my case) to the foam just to mount the motors. Unfortunately, I wish I didn't choose common pine due to warpage. I realize 2" is strong, but I can't imaging a large layout with only foamboard.
