Hollowing the Underside of the Fingerboard


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Addie’s Stupid Question of the Week #3:

 

For hollowing the underside of a (violin) fingerboard, how far do you make the hollow from the neck root?

 

I’ve seen numbers from 6mm to about 15mm, with a “blank” typically ~25mm from the neck root.

 

What distance do you use, and why?  Taught that way?  Acoustic reasons?  Other?

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~40mm from neck root for acoustic reasons. Leaving the fingerboard strong here keeps the B0 well above the A0. I don't want the two of them bumping into each other.

 

Interesting.  I should try something much larger than 6mm next time.  I have been taught to hollow quite a bit of the fingerboard but it seems like doing so makes the fingerboard somewhat flabby which seems to have an effect on body resonance.

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I leave it as it is most of the time,,,

I put carbon fiber in the neck so the B0 is high enough already,

but the added strength and hz's give room for adjustment if it is necessary

 

As I have looked through the available ct scans, (there are a few on the net).

I have noticed that the boards are not scooped out very far, if at all.

 

If you would measure a known distance and time it,,,, you could figure out how far they are actually scooped.

I haven't because I'm not that concerned,,,,, but if you are...........

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Take a  look at Schleske's work on this. As I recall, if you want the B0 mode to be just above A0 - 270Hz, then you make the frequency of the free fingerboard according to the formula F = 1.67*A0  where F is the frequency of the free fingerboard. 

 

Here is the link.

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Interesting.  I should try something much larger than 6mm next time.  I have been taught to hollow quite a bit of the fingerboard but it seems like doing so makes the fingerboard somewhat flabby which seems to have an effect on body resonance.

Darn tootin' it will have an effect. (That's how we talked in Wyoming.) See the Schleske link.

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~40mm from neck root for acoustic reasons. Leaving the fingerboard strong here keeps the B0 well above the A0.

 

Please say some more about how you keep the weight of the FB within acceptable limits, the amount of thinning of  the board beyond the 40mm, and any other tidbits you might care to share.

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Curious1,

I have no opinion here, just an observation. Your comment about A0 and B0 goes against plate tuning doctrine that matches them.

This was never an issue for me because I could never get them to match even if I tried. :D

Mike

If you tune the B0 either above or below the A0 (so that the B0 is outside of the A0's Q) the two won't interact or interfere with one another.

:^)

If you tune them and somebody untunes them, say by planning the fingerboard, the A0 and B0 will now interfere with each other destructively.

:^(

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You might consider something Roy interestingly shows:  He gives 5mm with a very flat shape to the end to the scoop, but farther down with a more rounded shape.  He doesn't give a specific number for the latter.  It seems he is taking into consideration strength and weight.

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I think you can definitely make the scoop too big in an attempt to loose weight, if the the area gets too "hollow". I feel that the fingerboard, neck and scroll areas are very important to subtle differences in feel of power, a certain level of strength can be lost to the over all tone if too scooped, particularly when playing close to the bridge. I do feel that some "guitar" acoustic science crosses over when we talk about these area's and that a certain level of mass at the lower area must transition to a smaller lighter "tip" or top of the flagpole so to speak. Thinking of this in terms of structural engineering as it related to top heavy design, what does no function well from a structural standpoint often translates to sound quality somehow.

 

If you had a hollow'ish narrow tall cone that you were using for a flagpole, you would want any mass added to the base in order to anchor the pole and allow the upper area to be more light and flexible. It's simmiliar when thinking of the neck and fingerboard. You don't want a top heavy setup where you have taken too much scoop away, thus making the upper area top heavy, or an imbalance of mass.

 

 To hear the dramatic effect that the scroll area has on tone, simply have a friend grab it a lightly squeeze while you play, even how hard they clamp down on it can effect the sound in a very negative way. You can fill the hollow with blue tack and start pinching off bits at a time and start to hear the difference, a too thin/much scoop may sound better with some of the blue tack still in there.

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It seems to me that if you tune the FB resonance to A0 you might well get a sympathetic vibration that feels pleasing to the player and gives an impression of liveliness. But in effect aren't you transferring energy from a radiative body mode to a non radiative fingerboard mode?  Which surely can't be a good thing?

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It seems to me that if you tune the FB resonance to A0 you might well get a sympathetic vibration that feels pleasing to the player and gives an impression of liveliness. But in effect aren't you transferring energy from a radiative body mode to a non radiative fingerboard mode?  Which surely can't be a good thing?

I think this is an interesting observation, but it raises a big question about violin design.

 

It seems to me that too many players choose a violin on the basis of what their desk partner says it sounds like at the back of a hall rather than because they enjoy playing it. 

 

The energy which returns to the player as "feedback" is crucial to the function of the instrument, and you can afford to divert a bit in that direction!

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I think this is an interesting observation, but it raises a big question about violin design.

 

It seems to me that too many players choose a violin on the basis of what their desk partner says it sounds like at the back of a hall rather than because they enjoy playing it. 

 

The energy which returns to the player as "feedback" is crucial to the function of the instrument, and you can afford to divert a bit in that direction!

Excellent point, Martin.

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It seems to me that if you tune the FB resonance to A0 you might well get a sympathetic vibration that feels pleasing to the player and gives an impression of liveliness. But in effect aren't you transferring energy from a radiative body mode to a non radiative fingerboard mode?  Which surely can't be a good thing?

I don't know. When we had tuning to A0 demonstrated at one of the Oberlin Workshops, listeners perceived an improvement in sound when they were matched. But of course, this would be thrown off the first time the fingerboard is planed. Also, we didn't test any other fingerboard frequency targets or theories, so there might be something better out there. I also can't rule out that the improvement in sound was due to an increase in player enjoyment. Stuff like that happens.

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Please say some more about how you keep the weight of the FB within acceptable limits, the amount of thinning of the board beyond the 40mm, and any other tidbits you might care to share.

I make the shape elliptical. The "rails" diminish to ~1mm at the end of the fingerboard (I'll post a photo if I can find one). This gives maximum stiffness where things are bending and least amount of mass at the end of the fingerboard (this helps keep the frequency of the B0 up).

The fingerboard is 7mm at the nut end, 11 at bridge end and 5-5.5 thick at the underside.

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