Another popular approach to building model railroad benchwork is the L-girder system. This design uses wooden strips that are screwed together laterally to form a long L-shaped girder. These L-girders are supported by a wooden frame. The roadbed rests on the L-girders, which can then be moved, raised or lowered in accordance with the track plan. The roadbed might be a simple cookie-cutter strip of plywood or plywood bonded to homosote; or it might be a series of “splines” made of thin wood strips, separated by spacers, which then support a roadbed of Homosote. The splines can be treated with steam or hot water to create elegant sweeping curves. The advantages of the L-girder design are its strength and flexibility. Although the second incarnation of the Blacklog Valley was not technically L-girder construction, it did incorporate risers and splines, as shown below.
A third common method of constructing the benchwork is the so-called open grid design. The grid is built of 1 x 3 or 1 x 4 boards, cut and joined to form a grid of supports. Plywood and Homosote sheets can then be laid on top of the grid. This was the type of benchwork I chose; but instead of using the grid to support plywood and Homosote, as is usually done, I decided to try a new approach.
I had for some time been intrigued by the possibility of using panels of extruded foam insulation to support a model railroad. These sheets come in one and two inch thicknesses, and in various sizes, most commonly 4 x 8 and 2 x 8 feet. There are two primary manufacturers – Dow Chemical and Owens Corning – and the two brands of foam insulation come in either pink or blue.
Foam insulation can be easily cut with a serrated or hot knife; it is light in weight but strong; and it can be bonded in layers for building scenery. It does present some challenges for the model railroader, which I will cover in future postings. But its advantages were such that I decided to build the latest incarnation of the Blacklog Valley Railroad on an extruded foam base.
The foam was bonded to the wooden grid with Liquid Nails. Latex adhesive was used to affix the roadbed to the top of the foam. In order to increase the elevation, it was a simple matter to bond two or more pieces of foam with latex adhesive. One of the advantages of using 2- inch foam is that four sections of Woodland Scenics styrofoam incline raise the track elevation exactly 2 inches.
Having designed a satisfactory track plan and set the parameters for my model railroad, it was time to begin construction of the benchwork. The standard gauge Blacklog Valley Railroad would loop through Blacklog, curve and descend under the highest elevation of the narrow gauge track, make a second loop and climb back into Blacklog in a “folded dogbone”. The narrow gauge EBT would meet the BVRR at Blacklog, where there would be a dual gauge interchange and wye. The narrow gauge tracks would climb a 2% grade up to Rockhill Furnace and the EBT shop complex, then continue on through a tunnel and scenic divider, up to Robertsdale and the coal mines on Broad Top Mountain. All this would be supported by an open grid of 1 x 4 boards and covered with slabs of 2-inch extruded foam insulation. Track would be laid on cork roadbed – or in the yards on sheets of 1/8 inch cork – cemented to the foam with latex caulk.
Having made the decision to use an open grid with foam insulation, building the layout moved from theory to carpentry! At this point the railroad consisted of a pile of boards, boxes of screws and slabs of foam. In my next post, I will explain how I went about constructing the benchwork, as well as some of the unique problems encountered in using extruded foam as a base for the layout.