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May 27, 2013 Fixing Paper Mache Problems

If you have read my About Me page you know that I have been a HO model railroader for well over 50 years.  I designed my current layout in 1989 and construction began in early 1990.  The design stage took several months and it is still under construction.  This is only my third layout since 1951.  Model railroads are never finished or complete, they are an ongoing project.

I decided to use blocks of packing foam for the basic mountainous areas because of it's high strength, light weight and it's also easily carved into any shape.  I used Expanded Polystyrene (EPS), also called beadboard, it is often referred to as Styrofoam.

I covered the Styrofoam with premixed Celluclay Instant Paper Mache that I purchased from Toys"Я"Us in 1992, Toys"Я"Us no longer sells Paper Mache. 

During the early 1990s through the early 2000s the premix Paper Mache was stocked in local craft stores, last summer I was unable to find any locally. I finally ended up purchasing a 5 lbs. bag of Activa Products Paper Mache off E-Bay.

The Picture below was taken in 2001, it shows my rock mountain built with Plaster of Paris castings attached to ¼" thick Paper Mache that covers approximately 25 blocks of 2"x12"x16" Styrofoam packing material glued in place with Loctite Foamboard Construction Adhesive. Regular adhesives will melt the Styrofoam blocks.
The foam blocks are very strong when stacked on top of each other, they would easily support several hundred pounds of weight. The left side of this early picture shows the Styrofoam blocks covered with Paper Mache.
The rock formations were made using Plaster of Paris in various Woodland Scenics Rock Molds and then attached to the Paper Mache by applying thinned Plaster of Paris with a brush as an adhesive.
The most important thing to remember about using Paper Mache is that it shrinks as it drys.  The thicker you apply it the more it shrinks.  The shrinkage causes stress cracks if applied too thin and if applied too thick on Styrofoam it will warp the foam badly.  Paper Mache is very strong for it's weight and very durable, it makes a very nice base to work from.  I tried to apply the Paper Mache an even ¼" thick and that was a mistake, ⅛" would have been much better and caused less warping.

My layout is located in our garage and it was not climate controlled for 20 years so the temperature would vary from the upper 30° to over 105° before I had R-30 insulation installed in the roof.  The temperature variations caused stress on the Paper Mache as well as the track.  I built several removable scenery modules from two inch thick Styrofoam for ease of construction and future maintenance in my hobby room that is temperature controlled.  After I moved the modules on to my layout the severe heat and cold took it's toll.

This post is about my repairs to a badly damaged module.  I have put this task off for ten years because of the nasty cleanup of the foam beads. The 2 foot by 4 foot Styrofoam warped ½" on all four sides so I need to cut or plane ½" from the bottom center and square up the sides. When the bottom is true I will glue it firmly to a ½" thick 2' x4' piece of plywood with Loctite Foamboard Adhesive to prevent it from warping.

This is what the removable section looks like before repairs.
The house to the right of the arrow head in the picture above is also on a removable section and needs repair.  It will be much easier due to it's smaller size.  The house, swimming pool,cars and figures are on a 2" x 12" x 18" piece of Styrofoam that also warped badly.
While I have the modules removed I'm going to do some modifications to the scenery.  I'm going to replace both of the Walthers Cornerstone two story houses with two of my scratch built Catalog Homes.  A third Catalog Home will replace the Cemetery on the other side of the gravel road.

At this point I removed the section as seen in the picture below.
Next I built a base unit from plywood shown in the picture below that will slide into place on my layout .

I used ¾" square glue blocks to strengthen the thin plywood walls.
The picture above shows the base unit in place. I marked both of the plywood sides so that I can use a jigsaw to trim them so that they will mate up to the existing scenery. I will cut a 4" hole in the end wall for easy power access to the removable section.
With the help of my wife and my grandson we managed to remove a half inch of the bottom piece of Styrofoam leveling the section to fit into the new plywood frame. We used my table saw as a planer and I ended up looking like a snowman. We ended up with the biggest mess I've ever made in my entire life with foam BBs everywhere. The cleanup took over two hours.

The picture below is the bottom of the section after the planing.

The next step was to pre wire the 1/16" brass tubing connectors to power the lighting on the module.

The Red/White wire in the picture above will power the 12 volt lamps in my houses with 8 volts and the vehicle lamps will be powered through Blue/White wire with 1¼ volts.  The lower voltage extends the lamp life and looks much more realistic.

I use #24 awg telephone main frame wire for powering low current circuits on my layout.  My normal low current lighting current doesn't exceed 150 ma. per circuit, #24 awg wire is rated at 500 ma,  I use 12 volt 35 ma. lamps in buildings and 1½ volt 15 ma. lamps in vehicles.

  When I originally built my layout I established a wire color code scheme for the various voltages to prevent errors.  I use Red/White for 12 volt (actually 8 Volts) lighting, Blue/White for 1½ volt (actually 1¼ volts) lighting, Orange/White for 4½ volts to power LED lighting and Green/White for regulated 5 volts circuit boards.

I used Foam Board Adhesive to glue the foam module to the plywood frame.  I put four gallon containers full of liquid to help hold the foam in place along with 8 clamps until the glue was dry.

With the adhesive dry I removed all the clamps and weights.
My removable section is now ready for it's makeover. 

I put the module back in my layout while I ready my hobby room so that I can work on it in the comfort of my comfortable computer chair. I need to move my Magnifying lamp to make room on my workbench for the large module.
I expect the remodel to take most of the summer.  As you can see from the picture above the module needs a lot of detail work.  I will have to replace all 55 of the tall pines and widen the gravel road to match the layout.  I'm going to make up some new rock castings to blend in to the layout mountains.  

I really enjoy working on scenery so it will be a pleasant project.

I will update my blog on the remodel and construction on this project with pictures as my work continues.