Installing Foam Board - Tips & Tricks

Matt - I'm guessing you mean blue or pink extruded foam. I think of "foam board" as 1/4" foam between two sheets of cardboard.

I use a "box cutter" with break off blades for most cuts. I only try to cut straight and perfect when I have to. Most of the time the cuts are crude. You may want to try using a rasp to finish forming a piece or to smooth / refine the shape.

 

I cut blue/pink board up to 1" with a razor type knife (box cutter, other type) Make the cut and then snap off the piece like cutting tile.
For 2"/4" I use a saber saw with a tile blade or a fine tooth blade, especially when I want a curved piece. I also cut pieces with a hand saw with a short blade or cut with a steak knife.
Use some scrap and experiment.
Doc

 

On gaps, use plaster cloth or Sculptamold or something over the foam board to cover the spaces and give the surface a more natural look. Don't worry so much about cutting straight lines as the only truly straight lines in nature are man made. A little variation in your cuts for scenery will only help to make it look better.

 

Matt, foam insulation (the blue or the pink) is quite easy to cut like these guys said. I use a sharp box cutter with interchangeable blades and then use my metal ruler to get straight lines while making my cut, then snap in half. Foamcore, I do the same way.

Another way to fill cuts is joint compound, (you've seen it in the Home Depot by the bucket for a $5) and that makes great fills. Like Sean said, if you're creating rocks and hills, nature doesn't create straight lines.

 

Matt

I use a box cutter or a pairing knife to cut the foam. Like others have said I don't worry about straight lines. Nature is random so straight lines ususally are not prototypical.

Here are several topics I have posted that show how I have used foam for various parts of my layout:

What I've Been Up to Latelyassenger Station Diorama

The Building of the RK&M: The Cement Distributor

Building the RK&M II: Hillside & Grain Elevator Extension

Building the RK&M III: The Mountain

 

I use a steak knife and a vertical sawing motion with a large drywall square to guide the cut.

I used to use a linoleum knife (curved blade with the sharp edge on the inside of the curve) but the blade got dull surprisingly quickly so I had some "tearing" at the bottom of the cuts.

I wouldn't worry about the gaps - just fill 'em in as written above. Now if you are butting two foam modules together, you have to be more careful to keep the cuts as square as possible. (That is foam modules with no exterior edging.)

 

In addition to the above, I've also used Great stuff to fill in the gaps.

 

Ya, what they said. It's important to remember that the foam is a rough layer in the scenery proccess. As the scenery evolves the gaps may become runoff streams or other natural features.
I have seen layouts with the foam perfectly filled, all shapes sanded smooth and rounded. At that point it is ready for paint and ground foam and call it done. This is all part of personal preference and what finish look you desire.
I would recommend trying a practice rock or two to get an idea of shaping and how much you will build up ontop of the foam. I had always assumed that there would be all these layers ontop of the foam but I have areas that are rough cut foam that has been painted and drybrushed that turned out incredibly realistic. It proved to me that with scenery sometimes less is more.:shade:
​

 

Matt, if you haven't already, check out the new book, "Mountain to Desert" by Pelle Soeborg, published by Model Railroader. It has some great ideas on this subject. Pages 44-51 are full of insight. Not sure what hot knife you're using, but the hotwire foam factory knives have worked well for me (check Micro Mark for them), and as for straight lines, like others in the thread stated, use a metal straight edge, but one noted poster said nothing is straight in nature. MRH

Here is a link to the MR outline of the book: http://kalmbachcatalog.stores.yahoo.net/12416.html

 

I have a foam related question. When I put it to plywood and cut it out to the shapes and sizes I want, do I paint it ground colors?

Also, what do I do when forming water? Do I just pour it onto the foam? Are there any steps taken before adding water?

 

MJC,

First off, go down to your hobby store and get the Dec '06 issue of MR. Pages 76-82 have everything you would ever want to know about creating realistic scenery from the foam up. But to generically answer your question, I first sand the edges smooth, then use spackle compound to lightly cover the remaining gaps in the foam. Once dried, I apply earth colored latex paint. Now the article has an interesting add at this point, the author, Pelle Soeborg, adds fine grain sand while the paint is wet. He states in his writings that this give a nice base for the next several layers of scenery materials. I have not done this in the past, but will try it next time.

As for your riverbed, I would not put the foam down as the base for the river, but rather use your plywood as the river bottom and work the scenery materials and the water product of your choice up from there. Use the foam to create the river bank.

M

 

Smooth cut foam

If you can imagine a layout the size of your HOUSE inside a huge building.

Now, look at the quality of the foam work. They use 'some' foam in a spray can but there is little if any drywall mud or spackling on this monster, yet. :angel:

 

MJC,
Joe Daddy's bottom pic illustrates my riverbed thought. M

 

:thumbs_up:

That's some good looking foam work!​

 

i just purchaced a hot wire foam cutter, it works great & was worth the investment, no mess,just wear a respirator when using one, also i cover the foam with woodland scence flex paste,2 coats then piant &ground foam.