Complementary clamping cauls to the rescue.
It’s not uncommon to have to repair furniture with curved parts, such as this Regency-style armchair. In the case of this particular patient, one of its armrests has completely cracked through where it joins to the seat with a couple closely spaced dowels (Photo above). Fortunately, it’s a clean break, and requires nothing more than gluing the sections back together. Unfortunately, it’s not a matter of simply slapping a clamp in place, since it can’t get the purchase necessary to direct clamping pressure perpendicular to the crack. This is a job for complementary clamping cauls.
Although I’ll show you a specific repair here, the basic principle of clamping with complementary cauls applies to the regluing (or new glue-up) of many curved parts. The primary concern is directing clamping pressure perpendicular to the joint line. In some cases–such as when clamping a couple of odd-shaped panels together–it’s an easy matter of creating standard complementary cauls that simply create parallel clamping edges, as shown in the sidebar at top right.
However, standard complement-ary cauls won’t work for this armrest repair because there’s no resistance in the space between the clamping points. This calls for something I refer to as “saddle cauls.” These are simply complementary cauls with a 1⁄4-thick plywood overlay attached to each face to allow fixing the cauls in place onto the workpiece. This keeps them from sliding or racking as you apply the clamping pressure to pull the parts together.
To make saddle cauls, trace the shape of the workpiece, and then draw caul patterns to match the contours (Photo A). Make sure to establish parallel clamp-bearing edges that will direct clamping pressure perpendicular to the break.
Trace the pattern shapes onto stock the same thickness as your workpiece, and bandsaw the cauls to shape. Next, create the plywood overlays, extending them far enough to allow good cross-clamping onto the workpiece. In this case, I extended them completely across the width of the arms (Photo B). Then tack and/or glue the overlays to the cauls.
All that’s left is to clamp the overlays to the workpiece, apply glue to the break, and clamp the parts together, as shown in Photo C.
Basic Complementary Cauls
In addition to repair work, basic complementary cauls (without plywood overlays) are often used for new work, such as joining these two symmetrical panels. If you’re lucky, you’ll be able to use your workpiece offcuts as cauls. If not, simply bandsaw some scrap to the necessary shape. Don’t worry about imperfect cutline travel. A caul doesn’t require glue-line joint tolerances.