Indeed Dennis, sorry for the typo!
This is my understanding as well. Even fortepianos by Stein and Walter had no gap spacers until well in the 1780s.
As for iron gap spacers, I believe there is one Zell 1741 harpsichord with them. It’s very rare, though, and I don’t know if the metal gap spacers were installed during a restoration. I don’t know any other harpsichord with metal gap spacers.
As for wooden gap spacers, I agree there shouldn’t be any need to install them in order to avoid the implosion of the harpsichord (in that case, there is a problem with the design), but I wonder if they could help with the tuning stability.
While I’m logged in, might as well chime in, just to agree with some of you:
Release the tension totally before installing spacers. I can’t imagine that forcing them in somehow will counteract the cumulative tension of a tuned harpsichord. Stuck registers often move right away by detuning the middle two octaves, that’s where they bend, the ends are generally still correctly spaced. And yes; put pressure plates on each extremity of the wood or metal spacers. I use metal as it is thinner and will less likely interfere with jacks. I’ve done this a few times : mostly on Heugel kits, all XLF, some Hubbard doubles, (perhaps earlier ones?), all Bizzis where the UBR is usually rather soft, most homemade contraptions. I put at least two in my own instruments, also to keep the registers up. It doesn’t really affect tuning stability as bending the case is a slow process.
Actually it depends a little on what is giving way: on a CMY assembled Hubbard (40 years old) it was the wrestplank that had folded up from the front, just sitting on supports, not inserted into the case sides. Still, there was severe cheek disease. So the register gap itself became wedge shaped : narrower at the top than at the bottom. I applied total string release, waited a week for it to unbend, the tuning went up day by day, yes indeed, reinforced the bottom with oak longitudinals going well past the register gap, the skirted stand hides these, carriage bolted the wp in the front right through to the bottom reinforcements, and installed -still wedge shaped- metal spacers. The original oak wooden spacers had cracked or bent. CMY himself suggested bolting it straight to the stand, but this impedes transport…and it was made of softwood anyway. I think I didn’t quite desribe the amplitude of the situation…The front legs would’na touched the ground anymore.
On light cases of wrestplank roll, and on-site where time is of the essence, I’ll sometimes put cut-to-length 4 or 5mm threaded metal rods just under the upper register, the flanged end bolts serve as pressure distribution and adjust to the actual space. No hammering or levering in from underneath required. So yes, the van contains a hacksaw, a small vice and a selection of steel rods, perhaps not so wonderful for a Carey Beebe airplane style maintenance tour! And no, I don’t recommend this for an actual historical and ancient museum piece!!
Then one has the case where the entire wrestplank is curved inwards at the middle, sight along the nameboard to see this, more common than one might imagine. This is usually found in beech wrestplanks, they actually bend laterally on themselves. I’ve stopped using beech long ago. It is and was not considered suitable for structural house carpentry, ie roof beams, as not pressure resistant enough under weight, according to construction guidelines. Why is it used in harpsichords? Tradition? Ease of availabitly? So this symptom isn’t just a problem of case construction as such, if one considers this to be the arrangement of braces etc under the soundboard cavity, bottom thickness or material, etc. These can be fine in themselves, but the string pressure might just push the soundboard forward and thus bend the upper belly rail inwards especially if its open to the cavity and not attached to the Lower BR, or again, pull the wrestplank back. Hope it doesn’t happen to any of you! Cheers anyway, Thomas
Very interesting Jacques. In my Hubbard 1973 kit, the wrestplank is made of maple, not beech, and to this day the register end of it is perfectly straight. What had bent and required new metal spacers was the birch-plywood upper belly rail.
Hi: Jacques Réelle is a ‘trying to be funny’ pseudo. Really je suis Thomas Murach! I have a Jackrail account on another computer with my actual identity.
More on 'www.my sitelamaisonduclavecin.fr 'That’s enough about me…Bye! And yes, plywood, even marine which has much glue in it, is not as stiff as the woods it’s made from.
During the recent and extensive discussion on gap spacers several contributors referred to the observation that the gap was not rectangular in cross section (e.g TwMurach), but rather that the side of the wrest plank was not strictly vertical but receded towards the instrument’s front as one followed the plank’s side downward (as I understood the descriptions).
That surface orientation would indicate that the wrest plank rotated (along its length across the instrument as a result of the plank being twisted. That appearance would also be consistent with the gap being reduced more in the middle rather than uniformly along its length, which I recall as being also mentioned (TwMurach again, e.g.).
If that understanding was/is correct, does anyone have a numerical estimate of the angle by which the plank’s “up-and-down” side at the gap is oriented with respect to vertical? I would like to know whether that angular (re-)orientation is consistent with the twist exerted by the moment (as mechanicians would call it: twisting force?) of the strings on the wrest plank.
The 1974 drawing that Grant O’Brien made of the 1769 Taskin in the Russell Collection shows three gap spacers, mortised directly into the wrest plank and upper belly rail.
It also shows the register thickness to be only 8 mm, exclusive of the leather, whereas my 1974 Hubbard registers are about 9.75 mm thick. The rigidity difference might explain why Hubbard used only two.
O’Brien left no footnote to indicate whether the spacers were original or had been added at a later date.
Thanks, James.
I’d like to thank everyone who posted to this thread, because you have all unknowingly performed a differential diagnosis on the health of my instrument. It appears the patient is terminal, having just about every malady mentioned, including, in no particular order: cupped and cracked wrest plank, in addition to being curved inwards to the gap in the center, cheek disease, Titebond creep of the soundboard into the gap, along with a bent UBR, also into the gap, soundboard splits, large near the cheek, and almost full length in the bass, but fortunately along the glue joints, and a key well whose sides are neither parallel to each other, nor perpendicular to the bottom. My gut instinct is to save the bentside and soundboard, and start over. Maybe not the best course of action, but it has become a matter of principle.
And I thought my Burton was in sad shape!