I've done the 'clamp-the bentside-to-the-mold' method, and I've done the
'heat-and-bend-in-place' method. Personally, I prefer the second method. I've
used presoaked wood, and dry wood, and have had success (and split boards) both
ways. I plane the board thinner, where the curve will be the greatest, and use
a HOT iron to heat the wood. Now, my experience to date with bentside
instruments has ONLY been with spinets. I have the bottom, spine, tail, left end
(there's an 'end' between the bass cheek and spine on spinets) and
wrestplank/register assembly all glued together. The whole assembly is put spine side down on
a 4 X 12 plank, which, in turn, straddles a pair of sawhorses. The case bottom
is flush with an edge of the plank (I know...a picture's worth 1000 words),
so that the bentside is up and horizontal. Now, I block each end of the spinet
in place, so that as I clamp the bentside in position (using 1/2" diameter
pipe clamps) the spinet won't slide around. I don't have the little 'case front'
pieces attached yet, as this allows me to be able to use handscrew-style
clamps to pull the forward end of the bentside into position.
As one very well-known builder once told me, "you'll go through every
expletive you know".
He wasn't kidding.
The reason I don't use a mold? Wood varies (duh!); even boards of the same
species will behave differently. To use a mold, one has to calculate
'springback', thus making the curve even more severe than it will ultimately be, and this
springback will vary. To REALLY make a mold correctly, at least IMHO, most
builders couldn't justify the time spent-and this is just for one style of
harpsichord! I clamp/heat the side in place, and it's done, instead of soaking,
heating, clamping...and then -days later- attaching the bentside to the
instrument. Why not just do this once?
I suppose that it comes down to finding what works for us as individuals!
That's part of the joy of building, is it not?