In theory the Baldwin soundboards were crowned using what I would call a hybrid system. The 72' crown radius on the ribs was chosen for reasons having nothing to do with the piano or its acoustics (look in the archives--I've gone into this before) and so, yes, they were lightly crowned. Too light, as it turns out. So it was also supposed to be ribbed at a moisture content of 5% which, in most climates, would give it just a bit of compression crown. Assuming the MC in the panel was held to the right amount at the time it board was ribbed. Which it probably was at least some of the time. These boards were never intended to be heavily loaded. Nor was it ever expected that they would be continuously field adjusted to "reset" string bearing. Of course it was also expected that string bearing would be "properly" set by the factory. Which probably did happen some of the time. As may be, if the field technician continually resets string bearing the board will (sooner rather than later) go flat and then negative. You are all free to do this with your pianos if you wish but I'd not if it were mine. Keep those bearing settings light or it will go negative. Actually, if it were mine I'd just put a new board in the thing, crown it a bit more and be done with it. As Ron points out, the possibility of field setting the string bearing was never the intent of the system. It was a manufacturing expediency. It made possible the planing of the bridges to a preset height. With a preset bridge height the plate could also be set to some predetermined height and initial string bearing then set to the bridge with small elevation variations of the plate being relatively irrelevant. Still not a bad idea. The fact that the vertical hitch also has certain acoustical benefits through the low bass is simply an extra, if unintended, bonus. ddf Delwin D Fandrich Piano Design & Manufacturing Consultant 620 South Tower Avenue Centralia, Washington 98531 USA Phone 360.736.7563 Cell 360.388.6525 Fax 360.736.5239 E-mail 1: del at fandrichpiano.com E-mail 2: ddfandrich at gmail.com
This PTG archive page provided courtesy of Moy Piano Service, LLC