Mudcat Café message #1688938 The Mudcat Café TM
Thread #89392   Message #1688938
Posted By: JohnInKansas
09-Mar-06 - 04:13 AM
Thread Name: Difference in fiddle bows?
Subject: RE: Difference in fiddle bows?
Bert -

I've found relatively little detailed information on bow making, while looking about in a number of "the usual places" including the web. While looking for the Smithsonian Mag article I mentioned on Pernambuko conservation, I did come across a site called Gaia Way that mentions a fund-raiser project to put together a book of bowmakers' articles on making and repairing instruments and bows.

The link describes the project, but doesn't say how one might be able to get the book - if it's been published. The article came out two or three years ago, so there may, or may not, be a book by now. A link, at the above site, is to the Pau Brazil Conservation Project where there's some more description of the project, but again no info on how/when/where the book might be found, that I found. I expect to look for it, but as a fund-raiser it's likely to be out of range for my budget, and looking isn't high on my todo list.

(Note that pau-brazil is a local and trade name for pernambuko. The country, Brazil, is named after the wood, not the other way around as often assumed.)

Your first difficulty in getting measurements will be in finding someone who has a bow for which there's a consensus opinion that it's "very good." It might not be too difficult to get someone to measure a few parameters like weight and cg. location, or even to let you make simple measurements that can be done quickly "while they watch." Getting detailed "variational measurements" that you'll need may require resorting to black magic and trickery.

I don't know to what extent professional bow crafters use any standardized measurements. It's quite likely that most rely almost exclusively on "it feels right" with a lot of experience.

A technique used by craftsman makers of snob-quality fly rods suggests a method that might be applicable to "charactrizing" a bow. The rod is clamped simulating a typical grip next to a large backboard, and the "curve" is simply traced onto the board. A few "standard loads" are applied at the tip, and the entire curve of the rod is traced for each load. Once the curves are recorded, the flyrod-fixer can bend a damaged rod back to match the original curves if the "action" deteriorates.

Since wooden fiddle bows are made straight, and then steam or other heat is used to "set" the proper curve, I suspect that at least some fiddle-bow crafters do use "standard curves" at least as a reference during the bending; but the curves used are probably "personal to each maker" and so far as I've found only "crude estimates" are published.

With the more complex action needed for a fiddle bow, to develop useful curves you would probably want perpendicular loads at the tip, for the "gross stiffness" and additionally you would need accurate measurements of what happens to the entire bow, and especially at the tip, when loads are applied against the hair, or at least for a couple of differenct loads at the tip in the direction of the hair tension. Since some of the characterstics of a good bow appear to rely on small deflections, your curves will need to be quite accurate.

Once you have an accurate set of "standard deflections," you should be able to "impute by analysis" what specific mechanical properties are needed for a "techno-bow" of your own design.

John