Violin Forum/Message Board

[williamwalsman]

I have currently made three violins. On two of the three, the fingerboard projection has dropped from 27mm to about 24mm. Both were made in the winter under drier and cooler temps. (60 degrees max.) I live on Cape Cod where it gets fairly humid and about 80- 85 degrees in summer. I've heard of Cellos needing a summer and winter bridge but not violins. Could this 3mm drop be due to seasonal differences or something else? A few months ago I reduced the bridge height to accommodate the fingerboard drop. The violin seems to sound as good as ever but would like to have it be a more conventional height. Anybody out there have similar experience?

[Michael Darnton]

How long ago were these violins finished? It's not unusual for the board to drop a couple of mm within the first six months as the violin becomes accustomed to the string tension.

You should probably pull the necks back to something resembling normal.
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[williamwalsman]

Michael, thanks for the reply. # 3 was finished and strung up in April 2012. # 1 in April 2010. You say pull the neck back; would you do that by inserting a small wedge where the end of the neck meets the block? If I do get the FB extension back to 27mm, any chance the neck will self adjust with cooler, drier temps raising that number higher than I want? One more question, on #4 to be built this winter, should I shoot for a higher initial extension number anticipating a drop once string pressure is applied?

[Michael Darnton]

The neck is pulled back by releasing the top from the ribs from the upper corner blocks up (leave the corner blocks glued), including the upper block, then putting in a strip of veneer between the end of the neck and the bottom of the mortise in the top--that is, a 30mm long strip, about 4mm high, and around 1/2mm thick. Then reglue everything.

That type of distortion usually happens a lot initially, then slows down. Over the years it will continue to happen because of the string tension. It will probably not go back up much when the weather changes, since it's more related to dealing with initial stresses than weather.

Sometimes people will set the neck a mm or less higher, to anticipate the change.

One thing to know about is if you dry your varnish in a UV box. The dryness shrinks the wood quite a bit, and when you put your board on, you'll think the pitch has gone up 2mm. But that's only temporary, and it will come back when the wood re-hydrates, so resist the temptation to correct that error on a violin that's fresh from the drying box.
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[williamwalsman]

Thanks Michael, your prescription sounds good. I'll make the adjustment and let you know the outcome. I'll be curious to see what tone difference there might be with the 3mm taller bridge.

[Michael Darnton]

It's very hard to specify what's going to happen. In a general sort of way, the violin can become less open and responsive if you go too far. If the neck is too low, and you cut the bridge down to match it, the sound can go nasal. Somewhere in the middle there's a balance that you will prefer.
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[polkat]

Michael says to use a shim "...around 1/2mm thick." Mind this! 1/2mm doesn't seem like much but it will quite visibly move the neck. When I do these, I make a few shims of varying thicknesses and try them all (unglued), measuring neck projection each time.

[williamwalsman]

Again, thanks to all for the tips. One last question. Is this procedure best done with or with out fingerboard attached to neck. If I take it off which is easy to do then I have better access to insert the shim. Of course I would need to temporarily clamp it back on the neck to determine projection after the insert. Since there might be a few tries with different size wedges this seems to me the best way. Also it seems like it would be difficult gluing it properly with the fingerboard in the way. Thanks again.

[Michael Darnton]

I do it with the board on. You can put the shim in, and fish it out, with a pin in a handle or a knife tip.

There are special clamps for gluing tops to top blocks with boards in place, and if you're going to be doing this stuff, you should get one.

Gluing without the board isn't horrible--it just gives another path for something to go wrong.
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[actonern]

Michael:

How important is top block dimension to this issue?

It strikes me, in an exaggerated example, that if the top block was 10 mm deep, there would be very little resistance against stress related deflection. If the top block is 30 mm deep, lots of support.

Do you think there's a "happy spot" in block depth that provides optimum support and yet doesn't intrude so far into the plate to affect sound?

Best regards,

Ernie

[Michael Darnton]

I think that the top thickness and shape of the arching coming off the block is the most important. You don't want a big bulge (weak) just in front of the block, and you don't want it too thin there, either. My arch is rising under the board, but with as straight a line as I can make it without being too strange--no puffiness.
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[actonern]

many thanks...

E