My rough benchwork is almost completed. I have never used foam before, and have a question about supporting it. I am in N-scale. The framework members are about 3 feet apart, side to side and front to back. I am planning to cover the frame with 2" blue/pink foam. I do not want to cover with plywood, but prefer to web the top with a series of 1x3's or 1x5's. How much support is required to prevent any sagging? I was going to run a support front to back every foot. Adequate? Or is it overkill? Need more? Any drawbacks to this system?
I used 5/8 inch plywood covered with one inch foam supported every two feet with a 1 x 4 inch board. It still sagged, but not much. However, that is not the question here... I would think that two inch foam, supported every foot, would not sag. I have no first hand experience with that type of construction. IMHO, the properties of the foam make it less subject to sagging than the plywood. I would think that another issue would be attaching things to the bottom of the foam. Switch machines, electrical wire support, barrier strips, etc., are easily attached to plywood.
Thanks, Flash. I should mention, no switch machines. But even then I could hang them on the 1x5s, I'm sure. The wiring can hang from the web, also. Mostly concerned about any sag. Want to keep this lightweight and simple. Also, I'm not building any gigantic mountains (plaster), what I will build will be mostly foam and relatively lightweight.
I didn't use any plywood under my foam. So far (third layout) no problem. If you were going less than 2" either glue up or single piece, then I would use a grid underneath. Foam is strong if it blue or pink. Not the white junk or bead board. Doc
Supports every 18" should do the trick, especially if you aren't using a plywood base, which would weigh things down more.
I have support every 18-24" and I use 1-1/2" foam. No plywood. Works great and does not sag. Remember, once you get your tracks all glued up to the foam, they also become "rebars" and stiffen the foam even more (though I don't think it needs it).
OK, sounds good. I'll look at 18" spans, it just looked a little wimpy to me when I did a mockup. But that will keep it simple and light. And less woodworking!
Here is a view of my _very_ open frame construction. I tried several types of support. The table is constructed of 1x4s. It is 3' deep and 10X10X9. it is also fastened to the walls. There is 2"s of foam all the way around. Most of it is 2" foam. Some is layered. Results: More pics here: http://www.trainboard.com/railimages/showgallery.php?cat=1260
Sagging is one thing- catastrophe is another. The last thing you want is a crack in the foam after the layout is finished due to someone leaning or whatever. I would suggest even the thinnest plywood base that can be purchased.
