Cover a cardboard tunnel with squirt- can foam insulation???

It wont win any awards but....i used cardboard boxes with newspaper wads taped to the top. Then Covered with woodland scenics plaster cloth and tinted with WS diluted pigments:

Knew a guy who used 'Rabbit' wire and spray foam, looked good after painting, and was reuseable?

I used Great Stuff spray foam on a mountain tunnel made out of 3/4" thick hardboard insulation and it stuck well. I would think it would stick pretty well to cardboard, also, but make sure the cardboard is rigid enough to support the weight of the spray foam.  I used the low expansion can.

In my opinion, left raw, it does not look good enough like a mountain for my tastes, even after painting. Too "squiggly" and looks too much like a human brain. I laid plaster sheets over it and then painted earth brown and covered with fine turf. Not that much extra work.

Just mix up some soupy plaster of Paris (or similar), dip some paper towels into it, and drape them over crumpled-up newspaper laid on top of the box. Give it a bit of paint, ground foam, and lichen and it will look almost great.

A little messy, but quick and easy.

Take a cardboard box. You get plenty this time of year.  Cut tunnel openings either end.  Brush on Elmers glue.  Sprinkle on popcorn.  Put diluted green food dye in a spray bottle.  Spray randomly on the popcorn.  Fast, quick, and your grandkids can eat the left over popcorn.  Plus the whole thing is biodegradable

@RickO posted:

It wont win any awards but....i used cardboard boxes with newspaper wads taped to the top. Then Covered with woodland scenics plaster cloth and tinted with WS dilyted pigments:

Nice.  Very nice.

Mike

@RickO posted:

It wont win any awards but....i used cardboard boxes with newspaper wads taped to the top. Then Covered with woodland scenics plaster cloth and tinted with WS dilyted pigments:

Looks like a mountain to me.  Nicely done.

To answer your question, yes this will work.  There is a youtube video demonstrating the merits of three different brands.  Easy to work with, far less messy than plaster.  Make sure you let it cure for several hours, then carve as needed with a serrated knife.

Thanks for all of these great suggestions.

I sure don't want a tunnel that ends up looking like a human brain!

In my youth, we used rabbit wire and paper mache (made with flour, salt and water), but those were the days when you could go into any hardware store and they had rolls of chicken and rabbit wire,  and would just cut a small piece off for you.  Not so today.  :-(

I once made a giant triceratops head to hang on the wall with the home-made mache.   It looked good for about two weeks, but then green mold started growing all over it.  (Not enough salt I guess.)

Being 10 years old, I took a can of Lysol spray (commercials said it kills mold and mildew!) and sprayed the whole thing down.  It took a week to dry, but it killed all of the mold.  I re painted it with a spray can, and it looked great.   

It hung on the wall of my bedroom until I left for college.

Mannyrock

I wouldn't use "chicken wire" or any kind of screen wire for terrain on a layout today.  Allegedly, it can interfere with the all-important TMCC signal.  DCS travels through the rails, so it may not be affected by wire mesh.  But believe me, DCS has its own set of issues!

The impact from loss of command signal could be ameliorated if Lionel gave us a setting such that, when the loco loses its signal, it keeps going at the last commanded speed.  You still wouldn't be able to control it IN the tunnel, but at least it wouldn't get stuck in there!  If Legacy / TMCC actually has a setting like this, I'm not aware of it.  But it should!!

So to avoid signal issues, I would stick to making tunnels out of foam, plaster cloth, etc.  My $.02.

If you are looking for a drop-on tunnel, you might want to try scrap styrofoam. That's what I used to fabricate a small drop-on tunnel for my brother-in-law's seasonal layout:

I used shipping inserts as the base material, but anything of roughly the right size and shape will do. To create the basic structure, I glued together various pieces, then carved the outside to create interesting shapes. For the 'rock faces', I used plaster of paris poured into a mold made from crumpled-then-straightened heavy duty aluminum foil, then before it fully set up, I slapped it over the foam and pressed it in to adhere it to the underlying shape. The portals at each end were my attempt to duplicate commercial portals in styrofoam, and the rest of the structure was created using an outer layer of toilet paper and watered white glue (a technique I refer to as "paper ma'sh*t!), finished with applications of base paint, washes, dry brushing and other landscaping materials I had at hand. The 'stone block' in the tunnel was cardstock printed with a stone wall texture file, and glued in place.

While generally pleased at the result, in hindsight I wish I'd spent some more time carving, to mitigate the somewhat 'boxy' origin of the piece!