Starting to get whole logging area working, and I needed a mountainous area for logging but it should be removable because it would be over several fairly long track tunnel sections. I thought a base of foamcore would work, be light but strong enough with a structural frame above, making it more ridgid.

Foamcore base of mountain

Thinking about how I would do this, I decided to try the new shaper sheet material, but even though Woodland Scenics says it needs no under support, I wanted to visually rough in the mountain and thought a hot glued cardboard strip web would also give it more strength, since it would be movable. Actually I do not think it will have to be moved all that much because even with a derailment under the tunnel, you can pop up inside the mountain enough to retrieve a car or engine.

Web of cardboard strips to support shaper sheets for mountain

The Shaper Sheet material shown is interesting as it has a very heavy foil backing with a fabric adhered to the foil, that mechanically bonds with applied plaster. Woodland Scenics has a Plaster made for it which I believe is lightweight Hydrocal with a retarder to slow the hardening so there is time to work a soupy mix, and get it into all the crevices.

Shaper sheet showing Heavy foil and bonded material on opposite side

Here is the mountain partially covered with the Shaper Sheet material and matching plaster

Mountain partially covered with shaper sheets and shaper sheet plaster