Violin bow flexibility

Edited: March 8, 2021, 12:41 PM · Is it helpful to know a bow's flexibility and/or stiffness? Is there any type of measurement that is made for comparison purposes? Would wood bows be more flexible than carbon fiber ones?

Replies (12)

March 8, 2021, 1:23 PM · Maybe.

Much depends on the technique and instrument of the player. So there are some great 19c bows that will be too soft for some, and other good examples of, say, Sartorys that will be too firm for others. I don't doubt that you could make a carbon fiber stick to match any of those in that one variable. Whether you'd want to is another question.

Edited: March 9, 2021, 9:09 AM · You can balance the flexibility or stiffness of the stick to some extent by the amount of hair used to rehair the bow.

As far as stiffness vs. maker and material of construction, measurements I made 20 years ago range all over the map (but not randomly). Makers of carbon fiber bows have produced bows that match the most flexible pernambuco bows made by the greatest makers all the way up to (and beyond) the stiffest wood bows made by great makers.

March 8, 2021, 9:21 PM · You might be able to get an idea of the stiffness/flexibility of a stick if you know its weight, thickness, and density. You can tell most easily by playing.

The time period in which the bow was made can be an indicator. A century ago, the trend was toward lighter and more flexible sticks. The preference has changed over the decades, and many of the older bows that appealed to players of another era come across as weak to current players. Sartory experimented with making stronger, bolder sticks, and the modern market trend reflects an appreciation of his efforts.

If you compare carbon fiber and wood bows made to the same specifications, wood will be more flexible. Keep in mind that carbon fiber has higher tensile strength than steel. If a bow maker considers the different properties of carbon fiber, it’s possible to make a bow that has the desired flexibility. Many of the bows available are not made that way and tend to be too rigid. At the entry level, though, carbon fiber bows are often hard to beat. There are some rather interesting upscale carbon fiber bows.

March 10, 2021, 1:11 PM · Andrew-- less hair for flexible bows? How much did you find yourself changing the amounts?
March 10, 2021, 4:40 PM · Stephen, if you send me your email address I can send you the spreadsheet with everything I did back then (20+ bows).

I tended to "pluck" hairs about 5 at a time. Used a pointed, straight edge Xacto knife to cut evenly across the hair "band" at the frog and at the tip to get to what my calculations indicated was an appropriate number of hairs for the bow stiffness.

I measured the stiffness of each stick by holding the "top" of the stick firmly down against a hard surface and hanging a known weight a short distance from the tip (same distance for all the bows). I listd the "stiffness" in units of "bending force per unit of deflection" e.g. newtons/meter. There are also many other parameters in the table for each bow. Stiffness for different violin, viola and cello bows varied from 61 to 333.

March 10, 2021, 5:32 PM · Thanks. I am at stephen[dot]symchych[at]sant[dot]ox[dot]ac[dot]uk


Edited: March 10, 2021, 6:37 PM · Unless the stick is way too hard or way too soft, I don't think the player has any business fretting about the stiffness of the bow stick. You'll feel it if it isn't right, anyway---I played on a cruddy German factory bow for a while that could be pulled totally straight with the absolute minimum of force. I hate that bow! Using it feels like trying to hammer a nail with a pillow.
March 10, 2021, 6:40 PM · I'm finding that there are a few borderline cases. Many 19c sticks, whether because they were designed that way, or because they have too many miles on them, are much softer than what is considered normal now. If rehairing correctly can get more use out of them, that is all to the good. And even with bows of a more conventional spec, it doesn't follow that the same wad of hair will do equally well for all.
March 10, 2021, 7:01 PM · All (maybe almost) the bows I worked with had a range of hair diameters so any numbers I came up with and worked with were averages over the "hank" of hair.
Edited: March 12, 2021, 10:20 AM · Stephen, it's my understanding that some 19th C bows were designed that way. You might notice in my EXCEL "bow calculator" the first two bows (F.N. Voirin and R. Weichold) are both 19th C bows one soft (63n/m) and one stiff (90n/m). but the 20th C (~1950) Holzapfel bow that we bought new in 1952 is also soft (63n/m) - by design. It is my understanding that Tourte made soft bows too.

The H.R. Pfretschner bow falls between those other two in stiffness (80). He spent 2/3 of his career in the 19th C.

March 12, 2021, 8:34 PM · It's not uncommon for bow makers to measure deflection when making a bow, comparing bows, or evaluating a bow. A 1lb weight is used for violin/viola bows, which is hung in the middle of the stick and the deflection is measured in thousandths of an inch. Violin bows fall between 160 - 220. Scroll down to the bottom of my article on bow making tools to see the deflection jig I use:
March 13, 2021, 12:18 PM · JUST SAW THIS:
March 2021 issue of "the STRAD" magazine, page 68-69, an article "Secrets of the Sticks" by Nelly Poidevin. All about this subject and modern measurements and PAFI software.

Nelly Poidevin, the author, is described in the Contributors section thus:
"Nelly Poidevin has worked as a bow maker almost 40 years, first in Paris and since 2000 in Dinan, Brittany. Since the late 1980s she has specialized in the reconstruction of historical bows. She regularly gives lectures and writes papers on the history of bows in Europe."

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