Techniques

Everything below exists to solve one of three problems: cutting many identical pieces, making a joint that holds, or stopping the whole thing from twisting as it dries.

The cutting jig

Build this first. A strip of scrap with a fence and an end stop, so a stick drops in and gets cut to the same length every time. Cut with a fresh blade in one pressing motion rather than sawing; sawing crushes the fibres and the piece ends up short and fuzzy.

The failure mode nobody warns you about is drift. Every cut takes a shaving off the end stop, so after a couple of hundred pieces the length has crept. Check the jig against a steel rule every hundred cuts, and glue a strip of brass or hard plastic to the stop face if you are cutting thousands. I lost most of a truss span to a jig that had drifted 0.4 mm.

Lamination

Two sticks glued face to face are far more than twice as stiff as one, and stiffness is usually what you are short of. Glue them on a flat board, under a weight, with waxed paper underneath, and leave them longer than you think — PVA is handleable in twenty minutes and not really done for several hours. A lamination lifted early keeps a memory of the curve it was lifted into.

Alternating the direction of the sticks helps: put the bow of one against the bow of another and they argue each other straight.

Box beams

The most useful single idea in the hobby. Instead of bundling sticks together, arrange them as the walls of a hollow square. The material is doing far more work because it sits further from the centre line, so a box beam of twelve sticks will comfortably out-perform a solid bundle of the same weight.

Build box beams over a former — a length of square stock, waxed so the glue does not grab — and pull the sticks against it with elastic bands. Cap the ends before you remove the former or the section will lozenge.

Bracing

A glued square is a hinge. Four sticks in a rectangle with glued corners will rack over under its own weight given a week, and the joint will not break, it will simply creep. Triangulate everything: a diagonal, or a small gusset of splint across the corner.

Gussets are also how you hide bad joinery, which is worth saying out loud. A neatly cut gusset over a slightly gappy corner is stronger and better looking than a heroic attempt at a perfect mitre.

Curves

Three approaches, in increasing order of effort. Kerf the inside face with shallow cuts and the stick will take a gentle curve — quick, but weak at the kerfs, so laminate over it. Soak in warm water for twenty minutes and clamp over a former; slow, and the piece will spring back some, so over-bend. Or build the curve out of short straight chords, which is what most bridges and roofs are doing anyway if you look closely.

Staying flat

Large flat assemblies twist as glue dries unevenly. Three habits fix most of it: glue in stages rather than all at once, weight the assembly to the board while it dries, and work symmetrically outwards from the centre so shrinkage pulls evenly. If something has already twisted, damp the concave face lightly and weight it flat overnight; wood that moved with moisture will usually move back with it.

Working time

Fifty pieces per session, cut and sorted before any glue comes out, is a rhythm that survives contact with real life. Cutting and gluing in the same sitting is how mistakes get glued in — you are tired from cutting and stop checking.