by Hendrik Broekman
Upon occasion, one comes across the odd wrestplank that has
decided to leave home and run off with the bentside. In polite harpsichord society, such
notions of independence are to be deplored. Only if the wrestplank stays in its place will
the instrument be functional. This sheet will outline some steps that can be taken to
restore the wrestplank to its proper place in life.
First it is necessary to make distinctions between degrees of
waywardness. The symptoms displayed by a loose wrestplank, aside from tuning instability,
can range from a barely perceptible lifting of the cap moulding to full-blown loosening at
both ends with the forward edge grossly tipped up. Attention should be paid to the glue
joints at either end of the wrestplank to be certain that they have not failed. In some
cases, the wrestplank and the sides were not adequately clamped together to begin with. In
some plywood cases, the glue joint between the wrestplank and sides is just fine, but the
plywood itself is delaminating. If the wrestplank has warped over time, this movement
added to the constant stress from the strings may have been sufficient to break the glue
joints at the ends. In others, for whatever reason, the joints have simply failed.
Having determined the degree of failure, it becomes necessary to decide
what to do about it. If the wrestplank has come totally adrift or nearly so, then the
decision is a no-brainer. The wrestplank must be removed, the joints cleaned and the
wrestplank replaced. In our experience, this is seldom the case. For a wrestplank to fail
so completely, it must have been installed very poorly. In this case, either a new
wrestplank should be fitted or the ends of the wrestplank shimmed so that there will be
tight joints where it counts. If there is only a slight bit of movement evident, one can
either enter watchful waiting mode or try to arrest the movement. Between these two poles,
there is a large gray area in which factors such as the worth of the instrument if
restored to function, available shop facilities, or even one's own squeamishness (cosmetic
or otherwise) enter into the resulting decision.
Consider the problem. In a five octave instrument with three sets of
strings and depending on the pitch and stringing schedule, the wrestplank joints must be
secure enough to resist approximately a ton of pull. At each end, the wrestplank has
approximately 16 square inches of endgrain-to-edgegrain glue joint as well as
approximately 8 square inches of edgegrain-to-edgegrain joint underneath. But in both
cases, there are large discrepancies in the amount of expansion of abutting surfaces to be
expected. Further, the stress of the strings is way off center, attempting to tip the
wrestplank up and out of its seat. Neither type of joint is well suited to resisting this
pull. The joints at the ends of the wrestplank are weak by virtue of a large endgrain
component coupled to a shear joint. The joints underneath are weak since they are under
tension, wood's great weakness. If one wished to play to wood's strength, one would
arrange the wrestplank with a compression joint overhead. This is our current practice.
Three possibilities come to mind to simply stabilize the wrestplank. Our
favorite is to glue a 1" w x 1/4" th x 71/2" or 8" long (depending on
the width of the wrestplank) piece of hard wood (maple or such) to the
(cleaned-to-bare-wood) insides of the spine and cheek bearing directly on the wrestplank.
The 71/2 or 8 square inch parallel-grain glue joint is quite sufficient to resist the
shear forces exerted by the wrestplank. Two other cheaper and dirtier possibilities
involve drilling through the case sides into the ends of the wrestplank (attempting to
miss the wrestpins) and doweling or screwing the wrestplank in place. Obviously this
general approach raises cosmetic issues for those who were not planning on repainting
their instruments in any case.
Otherwise, it is probably best if the wrestplank is removed and either
refurbished or a replacement piece fashioned (or bought from us) before reinstallation.
Avoid the poor initial repair. It is likely to result in more work in the long run. It
would be difficult in a sheet such as this to cover all possibilities since it is likely
that the range exceeds the powers of imagination. We are, of course willing to consider
specific cases individually by mail or phone.