I am well along the planning phase of a 4' x 8' n-scale layout. The question i need help with is: Can I use a 2" Foamular XPS sheet directly mounted on a 1x3 frame without a plywood sheet? The frame has the cross-pieces on about 18" centers. Comments would be greatly appreciated.
I MIGHT have placed the cross pieces closer together, 16" perhaps but unless you drop something heavy on the foam you'll be okay. 16" is common for wall stud spacing because 3x16"=48" which is the width of a sheet of drywall.
Yes. Extruded foam insulation of any kind is amply rigid, as long as you cross-brace the layout as you've described. A 1/4" x 4 x 8 sheet of plywood to the top of the fame (under the foam) will provide a mounting surface for under-the-layout goodies like switch machines, terminal strips, and the like. It doesn't add much weight and helps square up the frame. There are, of course, other ways to stick stuff under there by attaching direct to the foam or using a small piece of Masonite or plywood glued to the foam where needed.
I think this is a great suggestion. Here I'd go with 3/8" CDX as it is probably cheaper than 1/4". The slightly 'less smooth' surface is no problem with the foam on it. As mentioned it will really stiffen up the layout and give you a place to anchor things to under the layout that you might not think you need now but would like to use later. Just called the lumber yard and with the high prices still up there 3/8" CDX is $49.50 here. At $50 I'd still buy it in a heartbeat to assure options down the road and a stronger layout now. In fact I did spend the big bucks a couple months ago for the layout, Sumner
We should thank out lucky stars that we don't build our layouts out of mushrooms; have you priced them lately! Last week I paid $1.69 for 8oz. Today they were $2.89 for 8oz. Yikes and away!! But seriously folks; there was an article on Yahoo just the other day about lumber prices CRASHING. What planet are they on?
Well put sd90ns! Not much of any price drops here either. I paid up to begin my layout construction a month ago. A family situation caused a 1-1/2 year stoppage and I was happy to finally make a start.
I was going for lightest possible weight, but if it costs way more to save a few pounds, then, yeah, go thick.
USB plywood is the lower price. Here it is about half of what it got to in the spring. I used it to build a 2'x3' box, added an axel and wheels with a hitch. Now I have a trailer for behind my electric bike to haul things. It is rather rough but three coats of paint and a padded bathroom rug make it nicer.
I've done two like this. First was a 6x8 HO, about 20 years ago, double 2" XPS (4" total) inside of a 1x6 box (around the foam) with 1x2s on 12" centers underneath. That held together no problem and actually hung from the ceiling in my uncle's garage for awhile while he used the bay to restore a Mustang. Second was a 4x8 HO I put together this summer with my Dad in his basement. That's 1/2" XPS over 2" XPS over three 1x4s running lengthwise on approximately 20" centers. This has a lot more flex than I'd like, and I worry how well it'll stand up to my now-4-year-old nephew, but it's also super easy to wheel around the basement floor. My current layout (3'4" x 13'6" N) has the 1/4" plywood over 1x3s on 24" centers. This is more than strong enough but it's also a lot heavier than the other two, the two modules are frankly a pain in the ass to lift. My recommendation is that there's probably no cheap way out of this, if you do want the lightweight foam then go with two layers and build a box around it.
All correct, except it's called OSB (Oriented Strand Board), and, technically, it is not plywood, but is similar in form and function except for appearance. Plywood is made of multiple layers of continuous (more or less...) wood veneer sheets, stacked in alternating grain directions. OSB has thin, ~3" wide/long wood chips laid down in random grain directions with resin, then pressed and cured similarly to plywood.
Agreed! And when it breaks, its sharp edges are lethal. I'll never again buy MDF (Medium Density Fiberboard). It weighs a ton, sags when laid horizontally and produces huge volumes of dust when sawn.