Table of Contents

What is Spline Roadbed?
Spline is a series of thin strips of wood glued together to form the sub-roadbed. Because the individual strips are thin, they can be bent to follow the curves the track will follow. Once the glue dries, the individual strips become one thick strip that is very strong.

3d Spline Drawing

Spline is a great way to create flowing curves and dramatic scenery. Since the spline is attached to risers, the track is above the table level, this makes it very easy to add scenery elements below track level. The nature of spline also creates natural easements in corners. When you bend a strip of spline, the tightest curve is always in the center with easements to both ends.

What Do I Need?
Spline is very easy to make and can be done quite quickly. It is easiest to build spline on an open grid style of bench work like L-Girder, which is what we are using.

To build spline you will need:

  • wood to build risers, we are using 2″ x 3/4″ plywood cut to length.
  • spline strips, ours are 1″ x 1/4″ x 8′ masonite.
  • spline spacers, ours are 1″ x 1/4″ x 3″ masonite.
  • wood glue, we are using weldbond.
  • lots of clamps, be sure they can open to atleast 2″, 4″ for double track.
  • a level.
  • a hand saw to trim spline strips to length.
  • a drill and screws to secure the risers to the benchwork and the spline to the risers.

Cutting Spline Strips?

We chose to make our spline out of 1/4″ thick masonite. Masonite bends easy and is cheap. Any wood of similar thickness could be used. Just make sure it will bend without cracking. Some people use thin plywood to make spline.

Using a table saw, set the width to 1″ strips length wise. The longer the strip, the easier it is to work with and the less joints there will be in the finished spline. Less joints equals stronger spline. We are able to get 46 1″ x 8′ strips of spline from a 4′ x 8′ sheet of masonite.

To make spacers, take a strip of spline and cut it into roughly 3″ long pieces. These pieces are used to reinforce joints and create solid spaces to screw to the risers. Using spacers saves some material, by using spacers you can make an 8′ section of spline using only 6.5 strips, if you used solid spline you would need 8. Another reason to use spacers is that you don’t need to drill holes through the spline to drop feeder wires, they go down the gap created by the spacers.

Making Risers

We used 3/4″ thick plywood cut into 2″ wide strips to make our risers. You can make them out of any wood you have. Just remember to make them thick enough to screw into. Don’t worry if the risers wobble a little when attached to the bench work. When the spline is attached to the risers, everything works together to create a stable track base.

Risers for single track can be “T” shaped, but risers for double track should be “U” shaped for extra support and stability.

T-Shaped Risers: cut the vertical piece of the “T” to the appropriate length. The top of the “T” should be about 4″ across, this allows for some room to create gentle curves in the track. Screw the top to the vertical to create a “T” shaped riser.

U-Shaped Risers: these offer more support and more room for the track to curve. Cut two vertical pieces the same length and then cut a top piece 6″ wide. screw the legs to either end of the top to create an inverted “U”

Try to keep risers less than 12″ high. The taller the riser, the less stable it is. If you need tall risers, you can reinforce them.

Placing Risers.
When using spline, it is best to have a fairly accurate track plan ahead of time. While you could just lay spline where ever, it is easier to know where it has to go.

Use measurements from your track plan to mark the center line of the track on your bench-work. We tried to have a riser every 12″. Once you have the center line marked, you can attach your riser to the bench work. Use a level to keep the riser tops level. You can also rise or lower the risers to add elevation changes to the track.

We created a rise for run chart that shows the rise needed for a 12″ run for several different grades. This allows us to measure from a level riser up or down to create the grade we need.

Laying Spline
When starting a new section of spline, I like to put a screw into the riser with the head sticking up above the spline so I have something to clamp the first pieces to. If you are building onto existing spline this is not needed, as you just clamp to the existing spline. I also like to build spline from the back to the front.

I also find it easiest to work in as long a section as possible. The more clamps you have the better. An 8′ section of spline will need a minimum of 8 clamps, one every foot or so. Curved track may need more to keep things from bowing out. Longer sections allow the glue to set a bit at the beginning, so when you get to the end and go back to start the next layer, they don’t spring apart as fast, giving you time to clamp the next layer on.

Start by clamping your first piece to the screw head. This is the back and all future spline will be built onto it.

I find it easiest to apply glue to the piece being added, rather then the piece already in place. Always try to stager the joints in the spline sections. I have also found it easiest to make all joints between pieces above the risers. We add the spacers at these points anyway, so it reinforces the joints.

Once we have two solid strips on the outside, we can put a spacer before the next layer. As mentioned above, I place spacers at every riser. This creates a solid width of spline above the riser so we can screw it down onto the riser. This also assures that the gaps in the spline are always between the risers, where you’ll be adding feeder wires. Now you don’t have to drill to add the feeders, just pock them through the cork and into the gap.

I find it easiest to do the spacer and the next full piece at the same time. I put glue on both sides of the spacer and put it in place and stick the next full piece on as well before clamping. This speeds up the process.

Keep building layers onto the spine until you get the desired width. Let the glue dry completely before removing the clamps and moving on.

Drill and counter-sink pilot holes for the screws or they may split the spline when you try to screw it down to the riser. I recommend securing the spline to every riser. Once the spline is secure, you can use a belt sander to smooth the top surface of the spline if needed. (it usually needs some sanding to level it out).

For going around corners I have found it easiest to put screws into the risers at the apex of the corner as a guide to get the radius you want, but let the natural bend of the strips create easements at both ends. Build the spline layer but layer the same way.

The joints in the outside piece of spline may have to be screwed down and/or reinforced around curves so that they don’t peel apart. I have found gluing a 12″ section over these joints secures them well enough that screws are not needed.

Spline Widths
Here are some of the spline widths that we are using. These are based on the use of 1/2″ strips, if your strips are a different width or thickness, you will need to adjust things accordingly.

For single track sections, 8 layers are enough. This gives a total width of 2″, which is plenty for the cork and track.

Straight sections of double track don’t need to be 4″ wide, so we save some spline by leaving one solid section
out and being 3/4″ wide.

Curved double track sections need to be at least 4″ wide to allow the tracks to separate a little more to give more clearance for longer cars.

Spline for Switches.

There are two main ways to transition between single and double track. I call them stub-ended and smooth transitions.

Stub-end transitions are very simple, just start building the spline double thick when you get to the switch. This is the easiest way, but is also wasteful and all that extra spline may get in the way of scenery later on. Or you may need that big flat spot for scenery, so this may be the best option in some cases.

Smooth transitions are made by flaring the single track out into double track by bending half the strips out and inserting more in between to get gradually to the double track width. This is harder to do, but gives a smooth transition with no wasted spline.

To do this method, I usually build the single track spline up to this point and continue the four pieces that are on the straight route beyond the switch. Add layers to the section beyond the switch and extend the strips back into it. Work the other four strips from the single track section in to complete the transition. It never looks as nice as in the picture, so don’t worry about that.

Going from double to single track is easier, as you just have to cut each strip a little shorter and bend the outside ones back together.

Adding on to Existing Spline

One of the nicest things about spline is how easy it is to add onto. If you want to widen a section, just glue more layers on. Need to add some double track sections? Just glue some more layers on.

What if you want to change an existing section of spline? Just cut out the section to be changed. Make you cuts between the risers so that you can glue splices into the gap between layers. Build your new spline section onto the splices and put reinforcing strips on the outsides of the joints and you’ll have a solid, perfect connection.

Making a section of spline narrower involves a lot of cutting, so I’d try to avoid that if possible!