Supporting the Scenery
The track work on your model railway needs to be adequately supported and the edge of your layout needs to be strong enough to survive the occasional knock. Both of these objectives are normally achieved by constructing suitable baseboards. It is not the purpose of this article to discuss baseboard construction but rather to discuss the various means of creating a supporting base for that part of the layout not covered by track - the scenery.
Baseboard construction can be either solid or open top. Each of these has advantages and disadvantages when it comes to the scenic base. With solid top boards, you cover the entire surface of the baseboard with the same sheet of material that you are using to support the track (perhaps pineboard or ply). This has the advantages of providing an overall support for the scenery and also allows for the track plan to be modified to put tracks onto any part of the baseboard. The disadvantages are increased weight and the inability of having any of the scenery go below track level. With open top, the track support only goes below those areas that will actually be covered by track, the rest of the board remains uncovered by this material (hence the term open top). This method of construction has the advantages of decreased weight and the ability of having the scenery extend below track level (by raising the trackbed on suitable blocks above the main baseboard level). The main disadvantage from a scenic viewpoint is that with the baseboard being open, there is nothing there (yet) to support the scenery. Of course you can combine the open and solid top approaches to suit your layout, using solid top where there are lots of tracks and open top where you want lots of scenic features.
So lets move on to considering our various options when it comes to supporting the scenery. First we will consider the simplest way of producing a scenic support where we require flat areas.
If we want to model a flat scenic area at the same level as our baseboard, then the solution is simple. By using solid top baseboards when constructing those parts of the layout where you want this type of scenic effect, your scenic base is supplied by the board surface and no further support is necessary.
Constructing a scenic base for a flat area at a higher level than that of the track is best done by building a frame around the intended area supported on blocks (possibly with cross supports if a very large area is to be covered, perhaps with just the blocks and no frame at all if the area is small enough). This frame need not be made of as heavy a material as the main baseboard frame, and need not completely surround all sides of the area - particularly where it would get in the way of tracks tunnelling under the area. This frame is then attached to the main baseboard (whether open or solid top) using blocks of scrap timber. The surface of this area can be of much thinner material than the trackbed (eg. Masonite or 1/4 inch ply). If access to tracks passing under this area is required then the surface board can be left removable otherwise it should be securely fixed down. If a removable surface is required then you should consider using a slightly thicker board.
To construct a flat scenic area below track level is similar except that a frame will not be required regardless of the size of the area if the level is close to that of the baseboard frame. In this case the surface material should definitely be fixed down.
Of course none of these flat areas that you have created should be covered with completely flat scenery. You will still need to have some minor variations in the height of your landscape in these 'flat' areas. One easy way to provide slight variations in the height of the scenery in these areas is to cover the board with a layer of plaster in those areas where you want to increase the height of the scenic base slightly.
The vast majority of countryside isn't completely flat (or even nearly flat) and even where we do have these nearly flat areas at various heights on our layout we will still require a means of providing a base for the scenery linking them together. The approach that we have used so far of providing a flat board at an appropriate height does not work where we want scenery to move between different levels rather than being almost flat. We'll need to consider some different ways in which we can provide a base for this part of the scenery. In part the method to use depends on how big an area we need to cover. We'll start by considering the situation where there is a large area between our 'flat' sections.
There are a number of ways of supporting the scenery in this instance which give a variety of different effects. These can be broken down into two basic groups. You can either have a solid support under the scenery to hold it in place or you can manufacture a hard shell that only needs occasional supports. In either case the main concern is to produce a useable scenic base while keeping the overall weight to a minimum.
In many cases, the rolling scenery will go right up to the edge of our baseboard so the first thing that we need to do is to cut a scenic profile from masonite or thin ply to finish off the edge of the scenery. If we are going to use a hard shell method of completing the scenery then we will also need to provide scenic profiles at intervals through the entire scenic area. These additional profiles can either be from the same material as the edge profile (as illustrated in figure one) or you can just use timber offcuts. You then fill the space between the profiles with crumpled newspaper to hold up the shell until it sets. This newspaper can be removed afterwards if there is access to the underside of the scenery in order to do so or it can be left there where there is no access to remove it. If we are going to use a solid support under the scenery then these interior profiles are unnecessary and where we are filling in the scenic support between two flat areas at different levels we will not have an edge profile to worry about.
There are two main methods of producing a hard shell to go over the scenic profiles that we have constructed. The more modern way is to place fly wire over the supports and then fix this into place either using layers of plaster bandage or plaster with a thick consistency. Once this has set in place you can then use a finer plaster mix to finish shaping your scenery and finally once this is dry place the scatter material that forms your true scenic base over this.
The more traditional method of hard shell construction uses a coarser wire (usually chicken wire or similar) as the reinforcing material which is then covered by a number of layers of papier mache. This is a long slow process but builds very strong, very light, and reasonably cheap scenery. Papier mache is formed by tearing newspaper into small pieces and soaking it in a glue that is made from a flour and water mix. These small pieces of glue soaked paper are then laid over the chicken wire so that they overlap one another. Once the material in covered a couple of layers of paper deep it is then allowed to dry. The process is then repeated a number of times until a solid shell has been formed. You may need to add further papier mache in some places to get the exact scenic shape that you require. Once this final application of papier mache is dry you can then cover it with the scatter material that forms your true scenic base.
The hard shell produced by either of the above methods is relatively light because the shell either has crumpled newspaper under it or even nothing at all. If instead we go for a solid support then we need to find an extremely light material that we can use as our support. We do have the advantage if we use a solid support than we will not need any interior profile supports. One possible material that we can use is polystyrene sheeting. This material is light and can be easily cut either using a hot wire (which produces a neat cut and no mess) or using a knife or saw (which produces a jagged edge and is an extremely messy process). If you use a hot wire then you can actually cut the polystyrene to the contour that you want your scenery to have. If you use a knife or saw then you will not be able to produce the exact profile but you can get closer by gluing small polystyrene offcuts onto the low spots and then finish off with a thin layer of plaster. You will probably want to finish off with a layer of plaster anyway as polystyrene is soluble in some paints and you don't want your scenic base dissolving under you. Another thing to remember is that polystyrene is a flammable material and is also rather fragile so you will want to make sure that it is completely enclosed by your scenic profiles and plaster coating. Again, once the plaster is dry you then cover it with the scatter material that forms your true scenic base.
These methods are fine where there is a reasonable space between the sections of your layout that are at different levels. Where they are close together a different approach is needed. You either need to create the type of countryside that can support itself when it is nearly vertical (such as a rock face) or design the scenery so as to incorporate man made structures (such as retaining walls). As the different levels are close together we can use a sheet of thin ply or similar as the scenic base. In this case rather than laying the board flat we will place it on an appropriate angle so as to fill the space between the different levels.
A retaining wall can be easily created by covering this with brick paper. If a more contoured finish is required then a layer of plaster can be applied which can be carved to shape with a craft knife just before it sets.
You don't just have to use one of the methods that I have described here to produce the base to support your scenery. You can use a combination of these methods using whichever seems most appropriate to support the particular scenic effect you are trying to achieve. There are also other methods of producing a base for your scenery that you may want to use. The most important thing about the scenic base is that it be as light as possible while still providing a solid support upon which to place your scenery. Any method of construction that you find that achieves these goals and provides the desired scenic contours (provided that it doesn't use hazardous materials) will do the job.