South Mountain is located on one of two peninsulas near the entrance to the railroad room and the southern tunnel portal is very close to the edge of the layout. Being just a little beneath eye level for many folks it is common for people walking by to peer into the tunnel especially if they are expecting to see a train emerge. Well, before this project, here is what they saw...
The supplies arrived, and it was time to get started. Because my mountain was already built, I was not going to attempt to build a liner that would go from one tunnel portal to the other as Eric had done, but rather a liner that would go just beyond what one could see when peering into the tunnel portal. I used a tape measure set inside the tunnel to measure the distance and settled on 14 inches.
This is probably a good time to mention that although I did not know how to build a liner at the time I built my mountain, I did appreciate the importance of including an access hole underneath the mountain. This allows me to stand up in the mountain to perform routine maintenance duties and to fix a derailment if one would occur.
For the first stage of the project, along with the jig, I used a piece of thick plastic to lay down on your work surface. I also used fiberglass screen material, polyurethane foam, plastic mixing cups, stir sticks, wax paper (omitted from photo), and latex type gloves. Mixing equal amounts of polyurethane foam I covered strips of fiberglass window screen with the mixture and covered it with wax paper until it had partially cured. I had to experiment a little with how much of the polyurethane foam to use and how much time to allow for the mixture to cure before handling. After the foam-covered window screen was no longer tacky, I took the "window screen foam" strip and placed it in my jig to harden in the desired shape. After about 30 minutes I removed the formed strip and repeated the process to make additional liner strips. I made a total of five liner pieces. I could have made multiple jigs, but for my small project I did not really believe it was necessary. The second photo below shows a larger piece of fiberglass screen material covered with the foam and then wax paper. Once it was no longer tacky the material was cut into strips to cover the gaps between the liner pieces as seen in the first photo. I also used the material to stregthen the liner and to provide a lip along the bottom of both sides.