I might as well throw in my 2 cents worth. I also have been away from the hobby for many years and just finished my layout base. I built my frame using 1"x4" rough cut cedar boards, (which are actually larger than the milled 1"x4". The top joists are spaced 16"apart on center. The layout is only 4'x11'. Instead of putting any plywood directly on the top frame work, I have access to 4'x8' extruded styrofoam boards that are 3 ½ “ thick, so that went directly on the frame. This allows my enough depth to be able to carve all that I need, in the way of rivers, creeks, etc.I did use 1/4" mahogany plywood (which is actually thinner than that) for my inclines. I took some of the styrofoam scrapes, and made supports under the plywood and placed them about every 4" to 6" under the plywood inclines. Above the styrofoam base, I used acrylic caulking for the “glue” on everything.My layout is inside the house, not in a basement or garage. So therefore I don’t anticipate much if any fluctuations in humidity or expansion.
I'm late in the benchwork phase and certainly no expert.
I decided on 5/8" grade 1 B/C plywood with 1x4 main framing, most joists at 16" or so. I saw that the current MR Virginian project used 1/2" plywood and many here like the 3/4", so I decided on at least 1/2".
I was, and still am. confused about plywood! At the box stores, they had 1/2. 5/8, 3/4 and others, in various grades. The A/C grade wood "type" plywoods (e.g., birch, oak), I assumed are not all oak, just a very thin veneer on cheaper inner layers (unknown types to me). The store reps did not seem sure about that but I assumed that. HD also featured some 3/4" B/C "cabinet grade" stacks. I passed on them as I read on another forum that some folks were unhappy with those: too much warping after cutting, a low enough price to create concern on the (perhaps imported) wood type, etc.
I finalized on a B/C plywood from a Louisiana plant...I knew what it was (local pine), a modern plant,. etc. Withoput special ordering, I presumed that pine was the standard in Texas/Louisiana (e.g., versus fir), so I had the choice of B/C pine or the "birch, oak, etc types (only readily available in 3/4") where I had no idea what the innerds were. Maybe someone with more woodworking insight can clarify some ot these points (and what matters).
I picked through the stack carefully, quite a few sheets in the same stack had a fair amount of warpage but the nice ones I picked have not seemed to do anything too radical (in the home).
Paul
Modeling HO with a transition era UP bent
Jaakko_HansonIn my estimation, the qualiity of the plywood is the key to the thickness required. I use 4mm birch plyood, which is about the same thickness as 1/4 (I guess). This is a high quality, very smooth plywood. Unlike fir or spruce, birch will not absorb moisture during the numid months and then dry out during the dryer months. We have extremes where I live with 80-90 percent humidity and temperatures in the mid to upper 80s in July and August and very low (15-20 percent) humidity in the winter months. I live in East Finland about 19 km from the Russian border. I have no humidity control devices or air conditioning installed. I have noticed when living in the States (Oregon, California, North Carolina and Washington DC Area) that the plywood quality in the USA varies greatly. Part of this is due to the type of wood used by the plywood mills and part of this is that the customer always wants the cheapest he can get without regard to quality. If one insists, the supplier can get a higher quality product (and birch also). Jaakko Hanson Jaakko
QUOTE: Originally posted by Jl4624 Thank you for your reply. You mention that other modelers are using other techniques for building grades and inclines. What do you recommend?
QUOTE: Originally posted by Jl4624 I'm planning my new layout after a long time away from the hobby. I'm designing the table and I have a question about the subroadbed for the track. I've noticed that most articles suggest either 1/2" or 3/4" plywood. Why such a thick material? Wouldn't 1/4" do just as well and be easier to cut and bend?
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Tom