Sub-roadbed

Model Railroader Layouts and layout building
1

Hey guys!!! I recently came into some 2X8 plywood but it is 3/4 inch. It is not big enough for my curves but it willdo for all the rest. Is it too thick to deal with or should I just get the 1/2 inch LMK Joseph

2

3/4 inch is the thickness of choice for many for subroadbed because it will resist sagging over time.

What grade is it? It needs to be sanded on at least one side (both is fine). If it is, use it. You can always get more of it for your curves.

3

3/4" plywood is the subroadbed of choice for most non-foam users. It’s stable, and resists sagging. It’s also stiff enough to make smooth grade transitions. If it’s a lesser grade, it may need some filling and sanded to make it smooth.

Nick

4

HI all,

I have been wondering about choices of roadbed and subroadbed. I have decided that it will be wood of some type. Foam is not an option here in South Africa due to availability problems. Plus I like working with wood.

Here in South Africa the terminology at the local hardware store is different. So I have a few questions :

  1. Yes I accept that 3/4" ply is the norm. Is this preferable to MDF (medium density fibre board)? Here what we call MDF is a reddish brown product something like a thick version of masonite. (I would say it is a little less dense than masonite though). MDF is generally available here in 1/2" and 3/4" thicknesses?

I can also get pretty decent 3/4" plywood, but I am worried about warpage.

OK then for the roadbed. I see a lot of references on this site to homasote. What is this stuff? Chances are it may be available here but just called something different.

We also have a product called softboard. Basically this is looks and feels like shredded and recompressed toilet rolls and cardboard. Is this anything like homasote?

Many thanks in advance,

5

You can always piece pieces of 2x8 plywood together to form an area large enough for your curves. Just be sure your joints line up well with no bumps.

  • First… MDF will not warp, regardless of the thickness you use. However, thinner sheets of MDF can sag if you don’t support it underneath.

  • Second… Use a mask when cutting or sanding it. Cutting and sanding MDF makes a lot (and I mean a lot) of very fine dust – not so good for the lungs.

  • Third… It is very hard, and has a very smooth surface, so nailing track or cork roadbed to it is a very noisy endeavour.

  • Fourth… MDF is pourous so you’ll need to paint it with a good primer and then a finish coat of paint.

  • Fifth… MDF is heavy.

  • Sixth… Use screws designed for MDF or particle board to attach any legs or other support structure. Also, be sure to drill a pilot hole (particularly on the edge or near the edges) to prevent splitting.

If you’re worried about plywood warping, you can do what several others have done…

  • use 3/4" plywood ripped to 3" wide strips (most home renovation centers or lumber yards
6

Timothy,

thanks for the time you have taken to reply. However it has made me think that perhaps my terminology is wrong. I will be using pine 1x2 and 1x3 for the framing. Yes they will all be modular sections. What I meant by subroadbed is what you are calling decking I think. THis is what I will cut my splines from - either in MDF or plywood.

As I understand it, this will have a layer of homasote (or similar) on top, which follows the track contour, and preferably has bevelled edges to aid with the ballasting process.

Thanks, Ryan

7

Thanks Guys Joseph

8

Homasote is a grey, pressed paperboard, usually 1/2" thick. Hold nail well, although it does swell went wet, so it best to seal it.

MDF does not hold nails well and sagges far worse then plywood.

Before I switched to foam, I used laminated 1/4" plywood and 1/2" Homasote with supports every 16".

Nick

9

Homasote may well not be available in South Africa, but here’s a link to explain what it is:
http://www.homasote.com/sb.html

The manufacturer makes a lot of different things, but the “440” is what many modelers use.

Some poepel even cut splines from it and use the splines glued together as roadbed.

Many people have found that MDF is not a suitable substitute for plywood in model railroading due to the many limitations mentioned earlier. I think it would be especially unsuitable for splines.

10

Ryan,

From your description, the product you have is similar to Homasote. Homasote will hold track nails very well, which is why so many modelers prefer it. MDF is too hard to drive track nails into without frequent damage to your track. I would avoid it’s use.

Plywood is a great material to use since you can do so much with it. Used flat for sub-roadbed, the thicker the plywood, the less support it will need. The trade-off is that thicker plywood is harder to cut and heavier than thinner plywood. Thinner plywood is easier to cut but needs more support.

If you are using plywood to make splined sub-roadbed, thinner plywood is better. It is more flexible to work with. Once the splines are glued together, they are much stronger than a single piece of plywood used flat, and also won’t require as much support.

Hope these comments help. Post some pictures when you’ve made some progress. Everyone likes to see what other modelers are doing.

Darrell, quiet…for now

11

I use 3/8 and 1/2 inch plywood for a subroadbed - my joists are pretty close together (12-14 inches on center).

I used some homasote as a roadbed, then switched to cork.

12

Mark, which is the more quiet?

13

Crandell -

The homasote is a little quieter than cork, but I had some expansion/contraction problems with homasote, so I stopped using it. On most of the completed trackwork, I used small flathead nails to attach the hidden track, and spikes to attach the visible stuff. On both the homasote and cork, I can clearly hear my BLI Mikes’ sound effects. On one hidden yard I decided to try adhesive caulk to attach the track, and if I run a twenty car train over those tracks at sixty or so SMPH, the rumble is pretty impressive! I can’t hear the loco at all (the locos are turned down to about 1/3 maximum volume). Sixty is pretty fast for a freight, but I’m still testing the track. At lower speeds, 30 to 40 smph, the rumble is much less obvious.

14

Thanks, Mark. This is one area where I expect to spend some serious experimentation when I next design a layout. I have found my 5/8" ply with 1" foam to be okay, but just okay. I am thinking that hollow plastic ballasted EZ-Track is not the way to go; the ballast acts like a sound-box.

My bridges do not have the tracks adhered; in fact, they are almost suspended slightly above the decks, and my trains go dead quiet…a pleasant effect, to me.

15

That sounds like a good description of homasote. It does have one other good quality in that it is very flame retardant. The first sheet we purchased was for a stained glass class my wife took. They layout the glass and the lead U channel they assemble it with right on the homasote and solder it in place. Not burning is a nice feature for a layout.

16

Paul Mallery unfairly badmouthed Homasore in his Carstens book of a few years ago because of its dimensional instability under changes in temperature and, especially, humidity.

But Homasote is a superb material when laminated to 1/2" plywood to stabilize it against contraction/expansion. I have some 24 years old that is still as new. The lamination has to be done well, though.

My lamination technique: paint the bottom of the Homasote with a heavy coating of contact cement (I use Weldwood brand) using a disposable 3 inch paintbrush, then paint the top of the plywood with the same cement. By this time the Homasote will have absorbed the contact cement, so I give it another heavy coat. Then without delay I lay the Homasote on the plywood and weight it heavily – with sacks of mortar or sand – and leave it for a day or two. The Homasote is now stable and the lamination is permanent.

17

THanks so much to you guys - from what you say the homasote is very similar to softboard. I have seen (heard?) layouts with the track laid directly on plywood and the noise is terrible. Some people here use cork - I suppose the softboard is an alternative?

18

I have had good luck so far with Masonite for splined subroadbed, but I did have to learn a limitation: you cannot drill a hole in it through the section and expect the strip not to break when you bend it. Ince I realized that, I’ve had good going. My technique is a modification of Joe Fugate’s, suitably enlarged for O.

And despite claims, I’m not willing to trust die cast or brass O scale engines to foam/thin plywood laminations, especially over the kinds of distance in question here.