Bench Part 2 (Torsion Box Construction)

Where I left off last time with this project was making the top of a bench (Please refer to "Ultimate Guide to Torsion Box Construction - Bench Part 1, previous blog).  Almost twenty years separated this project from the first one - above left.  Both are approximately the same light weight but more stable and rigid than one made of solid boards.  Lots of pictures for clarity.

This solid looking top is all air inside, as in an air plane wing, as torsion boxes go.

The challenge was to make the four legs without adding much weight.  A sketch helped.

I cut a template for a 1/4 inch oak plywood as a frame support for the splayed leg design.

A scroll saw made quick work of cutting the 1/4 inch sheet.

The inside grooves in the legs and rail cut at the table saw will sandwich the plywood as they are assembled with glue and clamps (next photo)

Two wedges of wood cut to the same angle insured good clamping action during glue up.

Inside of each of the four legs are pieces of solid oak for reinforcement with a slight taper but not adding a lot of weight. Glue up shown in next photo.

Safest way to cut the 1-inch dowel is with a sled at the table saw.  These dowels will serve as connecting pins between the legs and the top.

Why go through all of this type of leg construction when a rail and leg design would have been easier by running two rails along the bottom length of the bench top connected to the four legs to support the entire under-carriage?  Yes, that was going to be easier but it would take away from the allure of the torsion box's rigidity and lightness in weight.  That's like putting up more posts on a suspension bridge.

An offset chuck on the drill made possible to drive screws in a tight vertical.

Note the four (black) walnut dowel pins on the legs.  More than decorative the pins secure the 1/4 inch plywood panel to the legs.  Although the assembly is well fastened with glue the pins are insurance against separation because the legs are splayed.  Probably not needed but it is for good measure.

This bench is so light weight that it can be carried with one hand tucked to one side as one would carry a bundled newspaper.

The new bench is about 1-1/2 inches taller than the old one.