“Ruminations” by Geert Karman

The Dutch — but Portugal-based — harpsichord maker Geert Karman (PIPARTE — Home) has published 5 essays on various aspects of harpsichord making. These 5 essays, along with other 6 unpublished essays, will form a book due in 2022.
Karman’s approach is a scientific one and doesn’t immediately translate in guidelines for harpsichord making. More so the last one, titled “The case”, which deals withthe complex forces and distorsions attached to the case of an harpsichord. Pictures of Hemsch and Taskin harpsichords (of which we discussed not along ago) close the essay.
In the essay I didn’t notice connections between frame, forces and tonal implications. Maybe in the upcoming book.
I am just not able to understand — let alone to object — to all this (there are even math formulas!), maybe any of the makers or the engineer- or math-inclined of the users can comment?

The Case: https://www.piparte.com/wp-content/uploads/2021/01/5.case_.pdf

A list of the 5 parts with their links: PIPARTE — Publications

Dom

Thank you for showing us this publication. Being both a musicologist and a physicist I feel tempted to break the silence evoked by your message.
The great value of physical laws (even math formulas!) is that these are equally valid now as centuries ago. To the contrary wood, musical taste and even the meaning of written words change over time. Physical laws did stay unaltered and provide us with a unique link with the past. We should cherish this link.
Personally I use formulas a lot when calculating stringing options for historical instruments and advice on stringing strategies fitting the goals chosen for a restoration. Formulas can easily predict or exclude certain stringing choices.
Geert Karman made the commendable effort to do the same for harpsichord cases. Given the complexity of the structure and the material of a case we should not expect the same practical value which simpler string calculations can provide. He is the first one to admit this in his text. Formulas will not predict how much a case will warp, nor when the wrestpin block will break. Still his formulas express correctly what all restorers in our forum already know: the sides will come up at the high side, go down in the corner, etcetera.
We also know that historical sources didn’t use similar calculations. Eg. Dom Bedos used proportions, Maffei in his piano drawing indicated shapes not forces. Builders just evaluated their own and other’s work and applied gradual changes to their design in order to find an ideal. Eg different bracing strategies in harpsichords by JD Dulcken.
In my opinion there isn’t much practical use in these calculations, perhaps it could be helpful when designing a brand new instrumenttype. But should all things be useful? It is great fun for those who like calculations (which are relatively simple to follow) and the author can be praised for sharing it with the community.

Pieter Kuipers