How I built the Mt. Lowe layout's trefoil base

Trefoil layout base made from styrofoam. Area is 4 sq. ft..

Last fall I wrote about some notes Bill Schopp published on trefoil planform layouts. I've been intrigued with the shape since then, especially for micro-layouts, and I spent many evenings last winter making drawings in my sketchbook of possible layouts. The shape seems to offer a way to build small layouts with good scene separation since each lobe could host its own scene with vertical elements providing a degree of visual separation in accordance with the design philosophy advocated by Olson and Furlow.

The glued up base is a 2-1/4" thick, 3-layer foam sandwich.

I like to use foam sheets for my layout bases because the results are lightweight as well as quite rigid and strong. Foam sheets are also easy to work with. 

I made the base for the Mt. Lowe micro from 3/4" thick sheets of styrofoam measuring 14-1/2" wide by 4' long that came in a 6-pack from a big box home renovation store. I think the price was around $17 CDN. This isn't the only material you could use to build a base. It just happened to be convenient, and I also had some scraps in the workshop, so that was what I used. 

Paper template; 4 sq. ft., maximum micro-layout size.

You may recall that last fall I also drew a full size template of a 4 sq. ft. trefoil shape so I could physically compare it to a square of the same area. I made use of that template to trace the lobes onto the styrofoam sheets. 

Once again, I'd like to make it clear that you don't have to build up the base in pieces as I'm showing here. If you have a large, thick sheet of foam you can cut the entire shape in one piece from it. In fact, that would be the best way to go, but if all you've got are small pieces, you aren't prevented from making a base, you just have to be a bit more cunning.

Lobe template detail showing interior edge lines.

Do you see those lines radiating from the centre of the template marked by the red arrows in the photo above? Those are the interior edges of the three lobes we're going to cut out. I laid the lobe template on a foam sheet and with a Sharpie pen traced around the lobe's perimeter to where it intersected both those interior edge lines. Then I marked the trefoil's centre with a dot - I had previously punched a small hole in the centre with a compass. After I lifted the template from the sheet I used the Sharpie and a ruler to join the centre dot with the ends of the lobe's perimeter. 

All three lobes laid out on the styrofoam sheets.

I repeated the process two more times to produce three lobes. It was then on to cutting them out.

Checking the fit of the interior edges.

I cut the interior edge lines first so I could check the alignment of the pieces before trimming the lobes' perimeters. I used a razor saw and a metal ruler to make the cuts.

After trimming the lobe perimeters to shape.

The lobe perimeters were then cut to shape freehand with the razor saw. Once the cutting was done, the edges were lightly sanded to smooth them a bit.

Gluing the lobes together. A weight holds the pieces down while drying.

The next thing to do was glue the lobes together. Start by spreading a generous amount of white glue over all the internal edges, then press them together. That metal box in the photo is full of nuts and bolts and is a good weight for holding the lobes in place while the glue dries. The box is an item from the workshop stuff I inherited from my father. I think he made it in high school shop class in the '40s. It's still full of the nuts and bolts it has always contained. That stash comes in handy now and then, not to mention its weight :-)

Filling layer for the styrofoam sandwich that will be the base

Here it is a few hours later after the glue has dried. The pieces fit together quite well. 

At this point the base is quite flimsy and needs careful handling, so be gentle moving it around. What we're going to do next is make a styrofoam sandwich with the above layer as the filling.

Applying the first piece of a 'bread' layer to the centre section.

The top and bottom bread layers of the sandwich are pieces of sheet foam glued to the filling layer we just made. At this stage, the bread pieces don't need to be cut to any particular shape. We'll trim them up once they're glued in place. 

Start by taking a long sheet of foam and laying it on the filling layer so that all three of its edge joints are covered. The sheet can extend well beyond the top and bottom of the filling layer - we'll trim it later. Now apply a generous amount of glue to the area on the filling layer where the bread sheet will go. Place the bread on top and hold it in place with some weights and clamps. Yeah, I've got a second collection of inherited nuts and bolts I keep in a plastic bin, and along with the metal box inside, it makes for a nice weight to hold this half sandwich together while the glue dries. 

Applying a bread layer to a lobe.

When the glue has dried, trim the bread piece's edges so they match those of the filling layer. The next steps are just a repetition of that first application of a piece to the bread layer. You keep gluing on pieces until both sides of the filling layer have bread sheets glued to it. There's nothing special to know other than these two points to keep in mind: 1) make sure you apply a large slab over the centre edges that covers them and as much of the filling layer as possible, and 2) make sure the joints of all the other bread pieces applied to the lobes have the joints staggered with respect to the top and bottom layers. Point 2) helps make the base is as strong as possible. If the joints on the upper and lower bread surfaces line up it makes for a weaker final structure.

Almost done adding pieces of bread :-)

The above photo shows the base when the sandwich is almost done. Over on the left side of the photo you can see the perimeter is rough cut at this stage. Once all the pieces of the bread layers had been glued together and cut to match the filling layer, some final shaping  was done with a rasp and sanding block to smooth out the contours.

All the trimming of the bread layers creates a lot of styrofoam odd cuts. I saved most of them for use when building the mountain scenery.

And here it is. The sandwich is done and awaiting perimeter smoothing.

This way of making the base is fairly easy, although it does take a bit of time. So, if you've got a few pieces of sheet foam lying around, this method allows a layout board to be built up from those scraps.

Before I go for coffee I should mention that when I built this base I wasn't sure if the layout would work, that is, I didn't know if could I successfully install the multilevel track plan with its complex - well, complex for me - grades, easements, and curves. Now that track work is behind me, and the layout appears viable, I think I might add some extra foam layers to the bottom so I can cut in some deep valleys to make the track seem even higher. Well, that's for the future, now is for coffee :-)