Track subroadbed

[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?

[chateauricher]

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?

[#welcome]

1/4" plywood will suit you quite well. However, it must have additional support or you'll find it starting to sag and droop quickly. You'll need a more substantial support frame for it than you will for the 1/2" or 3/4" ply.

As for bending, you're correct : 1/4" ply is far easier to bend. But that is only critical if you are using the "cookie-cutter" method. Many modelers are now opting for using other techniques to form grades/inclines, so flexible plywood is not as important.

[Jl4624]

Timothy,
Thank you for your reply. You mention that other modelers are using other techniques for building grades and inclines. What do you recommend?
...Jeff

[Tom Bryant_MR]

Jeff, welcome to the forum.

Check out http://www.woodlandscenics.com/. At the top of the page, Foam System -> Risers.

For some layouts, even HO size, some have used 2" pink/blue foam supported on shelf brackets or small 1x2 wood as the roadbed. The foam is amazingly strong.

It all depends on the underside or supporting structure.

[HAZMAT9]

With thin plywood you'll need quite a bit of support, not to mention trying to find a suitable piece which isn't overly warped. My sub-road consists of 5/8" plywood and 2" foam on top of that. Even with thicker plywood, I still had a time leveling out everything due to the warp of the sheet.

[nbrodar]

On my previous layout, I used 1/4" luane plywood and Homasote, supported every 16". Now, I use 2" foam, but have to grades.

Nick

[claycts]

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?

Welcome, I am old school. Using 1/2" OSB, "L" girder with 1x4" on 16"C-C. Cork is my choice on top. All glued construction for the track and cork (latex caulk is more to the point). Using my every popular BOWLING BALL test, I have no problems with sags. Humidity and temp are no problem in my case.
I tested 1/4" and had a deflection of over .0625 so I did not use it.
Take Care
"Got to make more SAWDUST!!"

[JimValle]

It's a misperception to think that the purpose of the subroadbed is to support the trains. It is actually meant to provide a stable platform, one that won't expand and contact too much with temperature and humidity changes and one that won't sag or distort over time. Therefore the heavier plywood is the better choice unless you have some compelling reason to save weight. However, quarter inch plywood can be used for roadbed. I get the stuff free from a local cabinet maker who uses it as back panels for his cabinetry. It is the same thickness as cork and I've saved a lot of cork by using the quarter inch ply under my yard tracks, engine servicing areas and other places like that.

[skimoose]

Sag in subroadbed isn't usually from the load of the train or scenery, its from mostly gravity, and to some degree humidity and temperature changes over a long period of time, and it's not limited to wood. Even double layers of 2" foam will sag over time if it isn't supported at proper intervals. Don't forget that 1/4" ply can also be ripped into splines if you don't want to do cookie cutter roadbed. 1/4" ply has also been used for splines between pieces of 2" foam, similar to the construction of modern surfboards. This gives you the low weight of foam with greater span lengths without sagging.

[Anonymous]

This may be "rude" on a Model Railroader forum, but the most recent issue of Model Railroad Craftsman has a very interesting article about using 1/4" plywood for a stable, lightweight, movable (though not portable) layout.

I plan to use 1/4" plywood on my next (shelf type) layout, as both base and sidewalls. The structure is the thing. A flat sheet with vertical supports will ALWAYS sag a little between the supports, no matter the climate or humidity. It's just whether the amount of sag is objectionable, or if the supports are close enough together, even visible. But it's there for sure!!!

-Steve

[Janafam]

As has already been said, some weight on quarter inch plywood pieces will show the effects of gravity. Paying for the higher cost difference going to half inch will be a wise investment.

[Anonymous]

I have a very large HO railroad. I have used 1/2" plywood with 1/2" Homasote on top and then roadbed on top of this. I had some sagging problems with the 1/2" plywood. I was spanning about two feet between supports. I am now using 3/4" plywood and have not had any problems.

[camarokid]

Welcome Aboard:
I use 1/4" and 3/8" ply for my subroadbed and don't have too much sag because my supports are only 12" apart. Why you ask? Because I want to do it right the first time and not worry about what's going on underneath and out of sight. When I tear down (have already started) my present layout I will use 3/4" ply for my sub on the table top proper and 3/8" ply for all grades since the risers will be 12" apart. Just so I won't have too many problems with warpage in my basement, I'm going to paint all 4 sides before laying cork and track. Just my thoughts on this wonderful, but basic problem we all share. Ain't it great!!
Archie

[Jaakko_Hanson]

In 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

[Janafam]

The quality of the plywood that Hanson mentions is one of the factors to consider. The thinner the plywood and the lower the quality will need to be offset by the amount of support in the under frame. Keep in mind that better grade lumber tends to show less warping also.

[Tilden]

I forget which one of the Old timers said it, but when asked why he used 3/4 inch plywood for his sub-base he replied "Cause they don't make 1 inch".

Nuf said

[CHIPSTRAINS]

ON MY 4'X8' IUSED A 4" FOAM "PINK BOARD". IT DOES GREAT, DUE IN PART, TO THE FRAME WORK. IF YOU HAVE A SOLID FRAME, I WOULD IMAGINE YOU COULD USE THE QUARTER INCH BOARD. [:D][:)][2c]

[chateauricher]

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?

Sorry for taking so long to get back ...

Some modelers (like myself) are opting for extruded foam insulation board (the pink or blue stuff, not the white).

The foam is rigid and lightweight to make any layout easier to transport. Thinner pieces of foam (less than 2") will require the stiffening properties of some sort of support fram (either 1x3 "ladder-type" frame, or a sheet of 3/8" or thicker plywood). Foam can be carved and shaped easily to make your hills and valleys. You must, however, use foam-friendly adhesives (read the labels carefully, and do a test to be sure).

To form inclines or grades, you can cut the foam to match the grade you desire, or you can use commercially available products (such as Woodland Scenics' foam inclines). While more expensive than cutting your own, the Woodland Scenics foam inclines do eliminate the need to do any calculations, and you can bend them to suit any curves you may have. As with anything in model railroading, you have to balance costly convenience with available time and skill.

My layout (currently in the early benchwork construction phase) will have a 1x3 "ladder-style" frame supporting a foam "deck" to which I will glue cork roadbed and flextrack. In some areas where I cannot use the 1x3's on edge, I will use them on the flat with a layer of 1/4" plywood on top, then the foam. This produces a solid and rigid benchwork — like that of a traditional wood frame; but with the workability of foam.

[Anonymous]

I went with a 2X6 framework underneath, with a piece of 1/4" luane plywood on top of that, and then 2" foam board on top of that. In N scale, 2" is almost 27 scale feet, so its more than thick enough to alow me to carve out all my depresions while providing a thermally stable platform to glue roadbed and track to. If you use a steaknife heated with a propane torch its literally like a hot knife through butter as far as carving landforms go. Dont breathe the foam fumes in however, they are toxic.

[WmnMrn]

Jaakko_Hanson

In 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

[peahrens]

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).    

[SilvertonRR]

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.