I've been wanting to put a hill/tunnel at the far end of the layout for a long time...finally decided to take a crack at it this year. In the past I've used the framework/screenwire/plaster or the cardboard/crumpled-newspaper/plaster-soaked-papertowel method for building hills...this time I'm going to try using foam insulation board. I've noticed that a lot of folks use it, and read a few articles on how to do it. There are also a number of useful YouTube videos on construction/painting. Still, this is new to me so don't think I'm an expert or that this is the optimal method. I'll show my progress here.
One thing to know is that there are two types of foam board - "extruded" and "expanded". "Extruded" is the pink or green sheets you can find at the local building supply store, typically sold in 4X8 sheets in varying thicknesses. This stuff is pretty rigid, relatively strong, and is what you want to use for foam scenery. "Expanded" is the white sheet/block stuff you frequently find used as packing material, comprised of billions of small white pellets bonded together by a heat process. "Expanded" is brittle, relatively weak, and doesn't handle chemical bonding agents well...for these reasons I am told one should not use "expanded" foam for scenery projects. I'm going to buck that advice and use a bit of it underneath as a backer, but the face and top of the hill will be built exclusively of "extruded".
The first thing I did was make a couple of tunnel portals out of pine lumber. I painted them with some textured spray-paint, then oversprayed that with various colors to give them a concrete-look. Then I printed some brick paper from the Building Textures section of the website and used that to make a few panels that I cemented inside the portals to give the illusion of a lining. Here's a few pic's:
One critical thing to do before going any further is to make sure your trains will negotiate the portals without hitting the sides. I had to move them around a bit to be sure my largest locomotives would safely pass through with enough clearance. It turns out that I have some scale passenger cars that are much too big to handle the curves and the position of the portals...they rarely get run so no big deal. Everything else clears.
With the portals anchored to the table I started boxing in the hill. I used four blocks of "expanded" foam as supports. and made a top out of 1-1/2 inch "extruded" foam. I used Gorilla Glue as a bonding agent...it seems to work okay with the foam when I tested it on some scraps.
I'm going to build the front slope/face separately, sculpt/paint it, then mount it to the front of the hill. The front slope will be built by piling up multiple layers of 1-1/2 inch foam, like rock strata. I think I'm going to use bits of foam and some HydroCal plaster to fill in any gaps...we'll see, this is a bit of an experiment. Across the back I'm going to attach a 2X4 1/4-inch section of masonite as a back-drop.
Here's where I am:
The pic is a bit dark...need some more light. I'll post more pic's as I proceed.