Module without the top sheet showing details of the plywood beams together with the end box-section (into which the legs slide).

My Venture into the Unknown - Lightweight Plywood Beams

The layout was to be portable and easily transported to exhibitions (who am I kidding? Short of getting Scotty to beam everything up, these things are never easily transportable). The main requirements of my benchwork were strength, durability and lightness of weight.

Benchwork on my previous layouts, some 20 years or so ago were constructed in the traditional manner using 2" x 1" softwood screwed and glued, Sundeala board being screwed over the top. How things have moved on. The thing about softwood / pine is that it is never straight no matter how selective one is at the timber merchants. And it's heavy!

Over the past few years, the lightweight plywood beam system has become more and more popular - at least in England. It is a system that was developed by Barry Norman for his exhibition layouts. Basically, each beam is made of two strips of 4mm ply glued to either side of pine blocks (see photos). Staples can be used to hold the woodwork together while the glue dries. I tried this but found the use of plastic clamps to be much easier. The beams are then assembled in roughly the same way that the 2" x 1" would be assembled to make a basic framework.

	Modules were joined together prior to fixing the plywood beam to the rear of the box-section. Note the plastic clamps which proved to be a God-send.

As this was my first attempt at making this type of benchwork I was a little nervous, particularly as my woodworking skills are not very good. On looking at the 4mm plywood in the store, I decided to play safe in terms of strength and opted for 6mm plywood instead. On reflection this was a mistake and benchwork for the rest of the project will be 4mm as suggested by Barry Norman.

The way I put the beams together to make the basic modules differs from Barry Norman's method. I have formed boxed hollows at each end of the modules for the legs to simply slide in. I used 9mm plywood for the end sections. This was a mistake and I will be using 12mm plywood for the ends of future modules. Benchwork for the staging yard is not open top so I simply glued and screwed 6mm plywood to the tops of the modules. I can't believe how strong and how light these modules are. I can easily carry a module and erect it single-handedly. I was planning to fix 6mm ply to the bottom of each module with cutouts for access to wiring etc. This would have provided extra strength by adding a web to the bottom of the beams thereby creating an 'I' type section and also forming a box type construction. However, the boards seem strong enough without the need for additional support.

Close up of end box-section in which the legs sit (with end piece removed for clarity).
Detail of abutting modules.

The way I have constructed the legs is completely different to the norm for this type of benchwork. I wanted the layout to be exhibited fairly high off the ground. I'm not getting any younger and layouts at exhibitions that are too low simply make my back ache these days. And I hate looking down on models, to me it makes even the best of models seem like toy train sets. Unfortunately, this necessitated legs that were too long to be integrated into the main modules. Legs are lengths of 3" x 1" glued and screwed and these slide into box-sections at the ends of each module.