Russell Miners

Tedswoodworking Plans

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is a chemistry-lab technician in Western Australia and a member of the Grey Company, a historical reenactment group.

Plywood skins and a gridded core make rigid tabletops and shelves by Ian J. Kirby and John Kelsey

Strong, light and stable. Torsion boxes outperform solid wood in many applications. Building a wall shelf like this one is an excellent way to learn alx)ut torsion box design and construction.

Like an airplane wing, a torsion box is made by sandwiching a grid of ribs between two thin skins. The torsion box exploits the bcM qualities of solid wood, plywood and glue, offering amazing strength and rigidity with minimum weight. Torsion boxes make excellent substrates lor veneer, plastic laminate or leather. And they can serve as versatile construction elements for all kinds of furniture, from simple shelves like the one shown here to giant conference tables and case pieces. "T-boxcs" also make good shop furniture, such as flat assembly tables and platens for veneer presses.

I he term "torsion" means twisting, and that s exactly what a properly made torsion box won t do, thanks to the rigidity created by combining its elements. (See Fig. 1.) Covered with veneer, a torsion box can be made to look like solid wood« but it s different in four important ways:

FIG. 1: TORSION BOX ANATOMY

The torsion box is a structural assembly of core pieces, skins and glue. It can be made any width, length and thickness. Softwood, plywood and MDF are excellent core materials. The torsion box shelf featured here has a pocket along one edge to fit over a ledger board. Pockets and ledgers are also used to join separate torsion boxes together, or to join them to other structural elements.

—You get total control over dimensions. The torsion box can be any size, in length, width and chickncss.

— The box is dimensionally stable—it doesn't move in length or width, and only minimally in thickness. (It won't move at all with a plywood core.)

—Once you glue up, you don't want to change your mind about the size of the torsion box. Ripping a completed box in half or trimming a couple of inchcs off an end could compromise the overall strength of the box.

—Torsion boxes can't be joined in any of the usual ways. Generally they require a system of blocking or ledgers that are glued and screwed into built-in pockets.

Torsion boxes can be built quickly and easily, as you'll see on the pages ahead. All you need in the way of tools are a tablcsaw, staple gun, glue roller and some clamps.

The Core

The core is a simple framework of lightweight wood, stapled together without glue. The staples aren't structural; they merely prevent the core

Completing the grid. No glue is necessary here. Outside joints get two staples; inside joints get one. Use a spare core piece to space and align the core pieces. Drive all staples below the wood surface.

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