I am almost to the lumber purchasing phase in building my new HO layout and have a question about plywood widths. I'm sure the question has been asked before so I apologize in advance if I am being redundant. I was planning to use 3/8 inch plywood with 2 inch foam as my base...building up with more foam where needed. The framework will be 1x4 inch pine with cross braces at least every 2 feet. Legs, again 1x4 pine every 4 feet...more if necessary. On many posts I've seen folks recommend using 1/2 inch plywood and sometimes 3/4 inch. I would think that 3/8 inch should be thick enough. Am I missing something?
Thanks,
Mainetrains
'there's something happening here, what it is ain't exactly clear' Modeling the Hard Knox Valley Railroad in HO scale http://photos.hardknoxvalley.com/
You may be missing that the way they built their early layouts with whatever they used, presumably not 3/4" or somewhat thinner plywood, was a bad experience for them. I used 5/8 ply, "good on one side", and found it to be very heavy and more than I needed...for the way I built. That was one layout ago.
If you are using 2" extruded foam, it will be very stiff...very. So 3/8" plywood sounds like overkill to me. You will want a light, but robust, frame around the periphery of your foam base to prevent damage, and cross-members below the foam here and there for support. All you'd need the bottom surfacing of ply for is perhaps to keep wiring up out of the way and to fasten switch motors and such. There really would be no other need with 2" foam.
For outer framing, 1X4 is okay. For legs, they're too heavy. Use 1X2 as I did and provide responsible swaybraces at angles going from near the bottom of the legs (stilts, really), to a point near the mid-point of your base framing. I say this expecting that you are not going to heave yourself atop a wide shelf and work there to extend your reach. If you are, and are a big person, then maybe something more substantial, including not using foam at all.
I got up on my recycled sheet of 5/8" ply that comprises my yard surface on my current layout because I had a lot to do outside my reach. I use no foam on this section, just tracks adhered to a thin vinyl underlay to keep it all quiet covered by sifted garden soil. But while I was building, I had to erect hills and a high by-passing part of my rail circuit way at the back. That module, of sorts, is supported by 1X2 with bracing, and the whole is bolted securely to the modules on either end. In fact, my layout comprises four open grid modules in a rectangle, with the duckunder entrance module supported only by bolts to the two on either side. All modules are sway-braced 1X2. Rock solid.
-Crandell
Some just use foam with no plywood under it. I would think 3/8" would be fine and it would give you something to anchor your switch machines and wires to. As long as your using cross braces like you said, you shouldn't get any sagging from 3/8".
I agree with Crandell. Assuming you will be using supports on the usual 16 inch centers (the universal recommendation for open grid or L-girder joists) the plywood under thick foam needs to be able to hold screws - and not much else.
I personally cookie-cut my plywood. As long as it is supported on 16" centers or less, 3/8" ply will support itself, thin foam (fan-fold underlayment,) a cardstock template, flex track and my heaviest rolling stock without strain or pain. If I was using thicker foam, I wouldn't hesitate to use thinner plywood.
Unless you model in 1:12 live steam or are building a raised floor masquerading as a layout, 3/4" plywood is gross overkill.
Chuck (modeling Central Japan in September, 1964)
I can think of only 2 reasons to put plywood beneath the foam:
1) You need to climb on top of the layout during construction. If this is the case, you're going to have trouble later, because you can NOT climb on top of the foam, even with plywood beneath. It won't hold much weight. You'll find footprints or kneeprints in your scenery. But, there may be cases where this is important.
2) You want to mount switch machines beneath the foam. I use Atlas and Peco machines, so I don't personally have this issue. For this, though, I would assume that 1/2-inch or even 1/4-inch plywood would be enough. Some modellers glue a small piece of plywood under the foam where they want the switch machine, since all you really need is something to take a few screws.
I'm assuming HO or N-gauge here. Larger trains will have more weight, and you may want the plywood to reduce sagging from the train weight, but foam alone is stiff enough for HO or, of course, N.
Are there other reasons? Always looking to learn, you know.
It takes an iron man to play with a toy iron horse.
Personally, I use 1/2" plywood because the sheets are actually a little thinner than 1/2" and I want 4 ply instead of 3 ply. I don't use foam. I have used 1x4 legs in an L without braces and it works well. My current layout, under construction, I am using 1x3's in an L shape with short braces, because I have some on hand and that works well also. I use cross braces every 16" inches and it works well. Legs are 8' apart. I tried ten, but got a little sag.
I suppose it's overkill, but my last benchwork has lasted 15 years with no problems and I plan to reuse it as part of the new layout. The other thing I have found is that in the smaller sizes of lumber it's hard to get decent wood. In fact I had trouble finding decent 1x4's and had to buy 1x8's and rip them into 1x4's.
Enjoy
Paul
MT, We used foam on our first layout and we were disappointed that it was not flat.
You have not stated the size of your layout. The size could greatly affect what you need.
On our present layout we knew that we would have to stand on it so we used 2 x 4's and 3/4 pressed board which was about 1/3 the price of the plywood.
Sue
Anything is possible if you do not know what you are talking about.
I just built my layout using just about that design. 3/8" plywood, 2 inch foamboard and 1*4 framing. I took the trouble of dadoing the frame pieces to accept the plywood. The resulting module of 1*4 and plywood is very strong.
David Starr www.newsnorthwoods.blogspot.com
MisterBeasley2) You want to mount switch machines beneath the foam. I use Atlas and Peco machines, so I don't personally have this issue.
The total of 2 1/2" inches (foam + base) for the switch machine throw wire to travel will be of issue. (I learned this the hard way. Given that distance, it has quite a side-side throw AND given the length the wire bends too easy requiring replacement with thicker gauge.)
If you can, I would recommend cutting a square hole in the foam before you lay down the turnout. Mount the switch machine (turtoise/bluepoint, etc) to a breadboard (found at radioshack) directly beneath the switch, and not because the foam & plywood.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
tomikawaTT Unless you model in 1:12 live steam or are building a raised floor masquerading as a layout, 3/4" plywood is gross overkill.
I know plenty of people with oscale layouts that use 3/4" and we don't regard it as overkill. I have a few scenes that are fairly deep that required me to sit on the benchwork while finishing the scenery. If you are planning on sitting on the layout for any reason I would not go with anything less than 5/8" but 3/4" is preferable.
Check out the Deming Sub by clicking on the pics:
Thanks, El-cap. I do spend hours sitting on the benchwork.
For my previous layout, I constructed bench work out of 1x4 framing with 1x4 legs and 2x2 cross bracing into 4x8 tables. Then laid a 1/2 inch sheet of plywood covered with 1/2 inch sheet of Styrofoam. That construction was fairly easy to perform cutouts, build scenery etc. However, the bench work was not mover friendly.
My current construction is to make the tables into either 4x4 or 4x2 sections bolted together to make 4x8 or 2x8 tables. The framing is 1x4 with 2x2 legs with angle bracing and cross leg bracing and 1x4 bench work cross bracing every 24 inches. I will finish off the top of the bench work, not covered with supports for raised cities or mountains with 3/8 plywood and varying thicknesses of Styrofoam to contour the scenery.
With this bench construction 3/8 plywood is sufficient.
It sounds as if your bench work is similarly constructed so 3/8 plywood and 2 inch foam will work.
I happened to have four old low four drawer dressers, that along with 2"x4" legs, form the surrort for my 24'x24' (around the garage loft) layout. I use 1/2" plywood topping.(without any insulation foam overlay). Although many modelers prefr to use 1" or 2" insulation, I personally don't see the point. Installing above or below table top switch engines, becoms a "bear"! I build large mountains with reinforced plywood arcs, heavy screen wire, covered with plaster cloth and Hydrical plaster. For ravines, I have used old kitchen drawers which slide out for access to the backdrop and hard to reach track. The old dressers not only afford ridgid support, but are also wonderful for storage. Bob Hahn