Each module that I am building has a layered luann frame and I beam cross members.

Now that I had a design for the cross members it was time to figure out what size the modules should be.  My goal was to create a four module return loop set that made maximum use of a 2’x8’ sheet of foam insulation.  I reached back to my college and high school geometry and decided to sketch some arcs on graph paper.  I ended up with a 36” mainline radius and 18” wide modules.  Since three of the modules would be almost identical, I could layout a template for the construction of a jig. Each arc had to be the same length and width and the curve had to flow easily across the set.

I could then layout the cross members on the template and cut them to fit. 

After everything was laid out, it was dry clamped together into it's final shape.

I haven't talked much about the layout of the modules- I envision the tracks running down a coast line, crossing a river then continuing down the coast. The tracks are along a hillside that slopes down to the water. The water is always exposed along the outside edge. This determined two of the big design elements:

1. there would be a 1/8" reveal of fascia above the foam- this will act as a retainer for the water pour (envirotex or whatever is chosen)

2. the inside radius of the module is the back of the hillside, laying out the elements of the cross section makes the rear fascia 17" tall.

(3. the front fascia conforms to the standard and is 6" tall.)

What you see now is....

The next step is to unclamp the cross members, one at a time, and glue them in place with gorrilla glue or a similar adhesive.

After each cross member is glued in place a second layer of luan is glued to the fascia and keyed into the web of the girder, locking it in place.

Corner blocks will be added to reinforce each crucial joint and a fillet of glue will be placed to reinforce each interlocking joint.

With all the clamps placed what you have looks like this:

- did I mention you need a lot of clamps?

Let it sit for 24hrs then start rotating and installing the fillets. I've learned a couple of important things so far-

Gorilla glue is strong and fast but gravity is still faster. I've got a lot of ugly runs. They scrape off ok after about 2.5 hrs but after that it's alot harder. It's important to give the stuff time to dry. I did both the top and bottom fillets on the beams at the same time and it was a disaster. That's why I'm spacing out the rest.

Also- luann is 3 ply. Grain direction matters. I cut for maximum use of the 4x8 sheet and ended up bending against the grain. I ended up with a few minor cracks but I don't think they will be noticeable when I'm done. I would definitely do it different next time.

I completely framed  the second and third modules (all three of the arc segments) at one time. I left is the entry wye section for later.

The second module came out cleaner than the first and I added some minor improvements- One piece interface cores and larger joint blocks.

The last module was the neatest of the three- design wise there were some differences. The centerpiece of this module will be a large bridge over a river entering the bay. At the mouth of the river I wanted the module to really open up.

I expanded the center module width to 24" in the middle.