Attaching Blue Foam to Plywood

Todd, I have used Liquid Nails for Foam to glue foam to plywood. Just read the labels - there are a bunch of different products. I think another is Liquid nails for Projects. Again, read and head the labels,

Gene

To fill holes or cracks, Woodland Scenics has a foam fill that when dry is supposed to simulate foam.  It does take awhile to dry and I let it set over night for large gaps.  But in all honesty I'm not sure its any different than a Red Devil light weight white wood fill.  I couldn't tell the difference between the two (and its cheaper and easier to get).  The Red Devil product is designed for smaller holes and gaps in drywall and is my preference although I've used both just recently.  When you put the two next to each other its hard to tell them apart.  I'm talking cracks here and not big 50 cent size holes.   

For gluing foam risers and other small pieces of foam to foamboard surfaces, I used the white glue with great results.  But white glue will take a very long time to dry when used between large sheets or pieces of foam layered over each other...the air can't get in to dry the glue.

   Well Todd what I have used is Gorilla Glue, for me it holds quite well. GG also foams as it sets up and will fill a gap with a cream colored foam. I am using Kato Uni-Track and a spot of white glue on each side of the roadbed keeps the track in place. Welcome aboard by the way............

Jacko

All, gap filling could also be done with the spray foam insulation.  I saw a layout where they used this to form the actual roadbed - had track supported by foam risers and just started squirting the foam into the gap between layout board and track.

For what it's worth,

gene

I've seen long skinny nails with oversized plastic washers but I believe that the washers and nail heads would be above the surface? I like the idea that you can remove or reposition the foam...

Gene

A crucial point.  I had that very issue come up recently when I was modifying my trackplan.  The offending screw was removed in a flash, and I drove a new one in out of harms way.

Purists might feel the plastic washers are useful, and I suspect they are.  Still, my approach is to buy as few things as needed, and the prospect of ending up with a half empty package of plastic washers convincing me to try the screw-only approach.

Cheers,

Scott

I have preferred to paint the foam AFTER the roadbed. I have no good reason other then I like to think the adhesion between the roadbed and the foam is better when glued if there is no paint.

Just being fussy...

Ok I have a question as long as we are on the subject of blue foam. I am in the process of still designing a new layout and will be using 1x4 for framework. What I would like to do is do away with a plywood top and am trying to decide if the 2" blue foam will be strong enough not to sag if I place cross braces appx. 16" apart.

The width will be 30' wide except the very ends that will be appx 4 feet.

Jack

The beauty about model railroading is that you have a variety of options of how you design and construct your layout.   Much depends on what you plan to have on your layout.  I constructed my 30" x 48" base module from two inch pine and placed cross pieces every 12 inches.  I elected to use a 3/8 plywood base over the frame (and under the foam).   This worked well for me as I had foam rising about 8 inches on each side of the table to simulate a rock cliff.  But since the rock cliff was only 3/4" wide running the length of the table, I had to insert 3/8" "L" shaped home-made hardwood brackets to hold it in place. 

I was glad I had the plywood base to secure these brackets to so when I turned the table on its side to work on the wiring, the narrow cliff siding would not collapse from the weight.  I also needed the "L" shaped brackets to fasten protective masonite to the sides of the foam cliffs and table.  Rising 8 inches above the table the foam had no strength and couldn't support itself.  But the hardwood L shaped "risers" I fastened to the table served as a skeleton to hold the foam upwards as well secure the masonite siding.   The plywood base made this job easier for me as I could cut through the foam and screw the hardwood brackets down to the plywood base from the top of the table or up from the bottom of the table.   In this case I was glad I had the added strength of the plywood.  I could have come up with a similar system had I not used the plywood but in my case it probably would have been more work and jerry-rigging.  I'll look for some photos and post later.