profile of violin bridge

[chanot]

Maybe I've been shaping my bridges wrong thru the years? I usually develop a 1.3- 1.5 mm thickness straight across the top by working on the surface facing the finger board. Then when viewing the finished bridge from the side,my thickness on the surface facing the finger board gradually increases in a uniform taper towards the waist- of course resulting in the usual convex appearance on that surface- While the back of bridge is left alone and maintains a right angle with the plane of the ribs.I thought I just saw in an article by the late Ms.Hutchings, a photo of her drawing of a profile of a bridge that appeared to show the top 5 mm facing the finger board to have no taper-- as if the 1.5 mm top thickness would still measure 1.5 mm thick all the way down that first 5 mm or so.This would seem to leave a ridge at that point and doesn't seem right..Any advice would be appreciated Dale/Chanot

[Jeffrey Holmes]

There is a lengthy thread on this subject which is available to you. Please check the "Reference Thread Links" topic pinned at the top of the pegbox page. You'll find a link for the bridge profile thread.

[chanot]

Hi Jeffrey: Yes I had seen it before and it helps.. but the drawing in Hutchings' paper seemed to show the thickness of the top equal for first few mm down towards the heart then flaring to the remainder of the rest of the face..however Michael Darnton's chapter says the first 5 mm of the bridge on the fb facing surface should not be convex when looking from the side(if I am reading it correctly) only lower on the fb side just above the waist it would show the covexity where there is a little belly( i think you mentioned that in your contribution to the thread) so i'm still not absolutely clear but understand that the lower 1/3 is planed to about 4.6 mm initially and then the top edge reduced to 1.3-1.5 mm even across the top and tapers down with I assume no noticeable ridge or facet where the two angles merge?

PS To Michael if he's on the forums these days... your book is going to be an amazing bible for us makers..how would we order? is that wrong to ask?

Chanot/Dale

[reedman]

Perhaps this might help also--Borman on bridges

[Michael Darnton]

It would be interesting to see the drawing to see what you're talking about. I can't envision how it would work. I suspect I'm going to say you have it wrong. What you want is a comfortable change, considering that if you get the face of the bridge too flat, it will appear to be hollow, which you don't want. Also it can't be flat from side to side and still have the appropriate top widths.

The shape of the face has been called a shell, which is a good description, but it had better be a flatter shell than the ones you see on the beach. Notice, though, how a shell has a straight mouth opening, and one side is curved more than the other. Just flatten that out until you barely can see it, and you're there.

One place where amateurs often mess up is making all the taper near the top, because they're afraid to get in there and thin the whole thing. The thinning, and the curving, should be evenly distributed and barely visible.

The book is a long-term project. Once it's written, it will need photos. I started putting up bits of it against the possibility that I'd die before all that happens. :-)

[chanot]

Michael: its an honor to receive your advice. We corresponded years ago when I purchased a violin with a cleverly forged repair label allegedly by Stradivari( label fooled the people at Strad magazine as it was almost the same as his signature on his will..but it turned out the violin was not old enough)

I copied the article by Hutchins some years ago from the web.it is entitled A NOTE ON PRACTICAL BRIDGE TUNING FOR THE VIOLIN MAKER...going to the web today I have found two listings as to its publication..ACOUSTICS FOR THE VIOLIN MAKER VOL II J42 Page 41 and CATGUT ACOUSTICAL SOCIETY LIBRARY issue 42 page 15-18 NOV.1984..they were only references and I couldn't bring the article to the screen. Don't know how to send scanned material to Maestronet but could fax to you.. I'm at dalepalko@shaw.ca.

I looked at a number of my bridges..20 years worth.. and all have the gentle TRANSVERSE convexity on the fb side with perfectly flat top edge.. but I note that the transverse convexity is greater on some and less then others.Of course this varies with the bridge height somewhat.

If you look at a completed and mounted bridge from the side and compare the slope facing fb to a steep ski hill ( note Padah hound) my earlier bridges have no convexity in the vertical axis (ie down the fall line) That always concerned me(but I guess it was correct) because this usually reduced the thickness of the transitional area below heart and between kidneys to less then the recommended 4mm...

I carved a bridge yesterday following the guidelines in your book (stay healthy..Antonio lived to about 90- maybe longevity from exposure to the woods and the continued mental challenges)I started with reducing the lower 1/3 to a thickness of 4.6 mm working on both faces 2/3 to 1/3.. then created a straight top of 1.5 mm. The top 1/3 of bridge showed the maximal transverse convexity on fb side and a tiny bit on other side.

Here is where I need your help. I didn't follow your final step of placing the bridge on 220 sandpaper over a flat surface and removing the vertical axis transitional convexity where the 4.6 mm thickness meets the tapering from the top.If I did that(as I used to do before getting worried recently about Hutchins' article) I would remove any vertical axis but would reduce the thickness in the transitional area just below the heart and between the kidneys, which I had been told to keep at 4mm.(however not by much.. about 3.75-3.80)

One could reduce the tranverse convexity somewhat a bit below top without losing straightness of top but as you say may tend to look sunken..So I think you will likely say its OK to follow your final step and that the slight reduction of thickness at transitional area from final flat sanding is OK..

Thanks to you and Maestronet for your continuing support

Dale/Chanot

[Addie]

The book is a long-term project. Once it's written, it will need photos. I started putting up bits of it against the possibility that I'd die before all that happens. :-)

I think a lot of people would pay to see your adjustments chapter. Me included.

I know you're not hugely into bridge tuning, but there are surely some corrective measures that can be employed? I have often wondered about the artistic vs acoustic side of things like changing kidney shape, for instance.

Any thoughts would be greatly appreciated.