Gary
I am back again, those doors are my own design, I cheat a little here, I own a steal fabricating company, and I design everything we build, these doors swing up into the tunnel and lock in the up position, living in the country doors are a must. The roadbed for the track in the tunnel is a steel trough, just wide enough for my widest engine to clear by 1/2". I also have a long set of grabbers that I can grab what is loose from either end. Most anything can be pushed out, so far I have never lost anything YET. The sides are seven inches tall so nothing can fall out or off the track road bed.
Rabbit mountain is hollow so there is lots of room, that is the reason for the doors to close easily, I know how I am, if it is not quick I will do it later and it would not happen. /DesktopModules/NTForums/themes/mls/emoticons/crazy.gif
The doors are made for cement to bond to, with big holes.
As far as the radius,the curve in the tunnel is at 8 ft. radius or 16ft diameter.All my track except for switches are soldered together, and all the track is bought straight, and I use the rail bender to roll the track where I want it. that makes the transition between the straight and curves gradual which results in less track problems.
STYRAFOAM, or ESP. this system has some advantages

and disadvantages/DesktopModules/NTForums/themes/mls/emoticons/cry.gif
I bought big blocks 24x24x48, I used a lot of the spray foam to bond together and filling in places I needed to. I used the hot knife tools sold in the garden railroad mag. this technique is simple but very much a time consumer. You can really create some very authenic looking spires. You carve out or burn away everything you don't want. I coated the ESP with the vinyl patch cement, I tryed brushing it on with a paint brush/DesktopModules/NTForums/themes/mls/emoticons/crying.gif

what a failure, that process does not work and it would take a massive time to cover a small area with no crevises. so you just as well not be using something that is easy to shape, I really recomend DO NOT try brushing on the cement. I bought a 20 dollar sheet rock sprayer at HARBOR FRT.mix the vinyl patch cement VPC thin and sprayed on to the ESP, I spray on 3or4 coats from all directions and it is still difficult to cover all it. I try to end up with 1/8-1/4" thick, some places will be thinner some thicker.
I paint to color just like I do regular cement, in fact I have mixed the two together and you can not tell where the ESP stops and the cement starts. The ESP works well where it is not exposed to foot traffic or possible rough hand exposure, like leaning on it or over it. Background works great. The back half of my over 8ft mountain is ESP and the front half where the water fall is cement, can't tell the difference.
I have learned new cement tecniques, I will probably not use ESP again. To get the large effects of the tall spires it is easier than cement.
If I missed any questions or did not address it far enough let me know.
Dennis/DesktopModules/NTForums/themes/mls/emoticons/hehe.gif