Intro

Like a lot of model railroaders, I like the concept of trains that run quietly. That is, a layout that doesn't make the noise of the engines louder because of the hollow chamber effect of the area under the layout. At first, for my S-scale layout, I thought about using insulation styrofoam as the base of the layout. That didn't work out for two reasons. One, I tried a bunch of glues and none of them worked well. There is no air between two sheets of styrofoam so the glue, if it dries at all, takes "forever" to dry. The second reason why I decided not to use styrofoam sheets for the layout base was that once I did manage to glue a couple of sheets together, they were not flat. Even though I took care to glue them on a flat surface, for some reason the glue must have pulled them at an angle. I put many weights on them while they cured. I finally decided to forget about styrofoam sheets as a layout/track base. I decided to go back to the old favorite, the cookie-cutter method for the subroadbed.

IMPORTANT: Please note warning at the bottom of the article!

The Foam

My plan was to cover the subroadbed with cork. However, the only cork I could find was 3/32 of an inch thick. That was just too thin for my tastes. Then one day I was wandering through Hobby Lobby when I saw Woodlands Scenics' Track-bed (shown below). The company makes it for N, HO, and O-scale, but not for S (of course!). As you can see, I decided on the O-scale version, with the intent of trimming it down to fit S-scale. The box contains a continuous roll of 24 feet of this lightweight foam. After I got it home, I measured it and its thickness comes out to about one scale foot. That is more what I had in mind for S-scale. The company makes other variations on this product. As far as price, I bought two boxes at a Hobby Lobby near us for $12.99 each and another one for $14.99 at another location. Both were running a sale of 40% off, so I was happy with that.

The Glue

Since I was back at dealing with foam, I had to once again face the issue of how to glue this foam to the painted MDF subroadbed. Woodland Scenics recommends their own Foam Tack Glue. Generally I find their products too expensive, but still I checked Hobby Lobby and they didn't have the glue in stock. I spent some time doing research on the Web and found that many web sites referred to Pliobond. The advantage of that glue was that it should work with foam and that it is rubber-based, which means it adds to the sound absorption. I found a 1/2-pint container at my local Ace Hardware store for $6.99. I cut a piece of foam off and glued it (per the instructions) to a left-over piece of MDF. I put some weights on it and waited about 45 minutes. The results were promising. It had enough hold and it didn't eat away at the foam, but I could pull it off with some effort. I figured that with the larger sheets of foam on the subroadbed that it would work just fine. The downside was the incredible, horrible stench! This is the nastiest stuff I have ever used. I did use it to lay about 8 feet of the foam on my layout, but I just couldn't take it any more. Days later we could still smell it in the house. I threw it away. I will never use that product again! I highly recommend a respirator and using it only outdoors, if you have to use it.

I also tried Elmers wood glue, because I read on some websites where people had used that to glue foam. After 30 minutes of drying time, the foam pulled right off. That didn't work.

I went back to Lowes to find some other glue. I had used PL Foam Board Adhesive when I tried to glue the layout base's insulation styrofoam sheets, but it just didn't work. It provides no initial tack, so the sheets moved around on me while I was trying to put weights on them. It took days to dry, and even then I could easily pull the sheets apart.

When I was at Lowes I saw Loctite Power Grab Foamboard Adhesive. It was about a dollar more at $4.20, but it worked great. You get about 15 minutes of working time, so during that time you will need to hold the foam in place with pins and/or weights. After that time it is dry (I usually give it about 30 minutes). It does indeed provide quite a bit of initial tack. It takes a full 24 hours to fully cure. It doesn't eat at the foam, and it holds it in place after it dries. I highly recommend that. And, best of all, it only has a very faint, pleasant odor.

The Installation

With the glue issue resolved, I could get back to laying the foam roadbed. I measure out a section of subroadbed to cover with the foam and cut a piece of it off.

The roll of foam has a slit down the middle on the bottom. You can ignore that if you are laying O-scale straight track, but for any other application, you will need to cut the foam in half. I bend it open (as shown in the photo) and then carefully cut it down the slit using a utility knife. Using a pair of scissors I trimmed any excess.

Then I use one piece to mark off, with a pencil, where to place the glue on the subroadbed.

For using the Pliobond it wasn't that big of a deal, but the Loctite Foamboard glue dries hard, so any glue that oozes out will have an impact on the next piece of foam that is butted up against this piece. In other words, to avoid spending time cleaning up hard glue later on, keep the glue inside the pencil lines. I place a bead of glue down the area and then use a popsicle stick to spread it out thin. If it is too thick, it may raise up a section of the foam.

After I place the foam piece on the glue, making sure that there are no gaps between it and the previous piece, I use a piece of flat board to really press down on the foam to make it adhere to the subroadbed.

Then I place some flat boards on the foam, followed by some random weights. I let this sit for about 30 minutes. The foam is then fairly secure.

For this particular piece I was at the edge of a module. My modules need to be removable, so I will trim the loose foam off at the module's edge. The foam is now ready for the next piece.

It does take a bit of time. If you are in a hurry, you can glue several sections at different locations around the layout. For me, I enjoy taking a break from my work every so often and gluing a piece. The turnout areas require some special cutting and careful measuring. Also, I decided to make the top of the foam roadbed a scale 10' 6" wide. This allows for about a foot of roadbed outside the ties. Since the O-scale foam is too wide for S-scale, the other half of the foam piece is trimmed to size before it is installed.

So far I like this product. I think it will be easy to glue the wooden ties to the top of the foam. And I do think that it will aid the sound absorption of trains running on the layout.

Important Update

After two weeks when I was laying ties on the foam, I discovered that the foam was coming loose from the subroadbed. I had tested the Loctite glue with a sample piece of foam and MDF before I started using this combination on the layout. The day after the test the foam was very solidly attached. I experienced the same thing on the actual layout. However, now, after two weeks, the foam could be easily pulled off of the MDF. I have, therefore, decided to abandon this method. I will now use ceiling tiles glued to the MDF subroadbed.

I also decided to completely replace the MDF in those sections of the layout where I used the Pliobond glue, because after two weeks that glue was still stinking up the room, and it was starting to give me a headache. Now that the subroadbed that had that glue on it is out of the room, the room smells a lot better again.

The other observation I made was that the wooden ties couldn't be glued to the foam. I tried the same Loctite glue, Elmers wood glue, superglue, 5-minute epoxy, and 90-minute epoxy. The 90-minute epoxy showed the most promising results. However, that is a rather expensive and time-consuming method for attaching thousands of ties.

Your mileage may vary, as they say, but I will never use the foam again. The other lesson I learned was that I should have only done one section of my layout at a time, that way I wouldn't have wasted time and money putting foam down on the entire layout.