Violin Forum/Message Board

[John Cadd]

First impressions of two videos about fitting a bass bar was horror that so much heavy metal was being used to torture an innocent violin belly. Both videos showed half a dozen chunky metal screw clamps pressing the life out of a new bass bar . I thought about the stresses being left in the belly wood with so much pressure .Even chalk fitting will not give you a perfect matching surface.Something much gentler than big metal clamps would do the job and leave the belly and bar free of built in tensions . Sometimes you see glass window reflections where the fixings had pressed the glass and distorted it`s pure flatness . The edges of ribs , before back and belly are attached , should be in flat planes. Any unevenness would be a target for criticism . Why? Because the back and belly would suffer from tensions . That would restrict the freedom to vibrate and make music . A violin bridge is left loose .If it was glued down there would be a build up of tensions. That makes me think about the question of fitting the ends of a bass bar. Some say to make them stand off the surface before fitting permanently ,and then clamping the ends down -to add some tension ?? But most makers advocate using seasoned wood ---to avoid tension build up if unseasoned wood is used . Something to think about .

[Michael Darnton]

Clamps are there to hold wood to wood, not to tighten to torture level. Corks under the middle of the clamp at the balance points will minimize distortion from the weight. Bars are often sprung to counter the distortion of bridge pressure. Bridge presses down and bar presses up. Ideally the wood is then sitting at neutral between two opposing forces.
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[John Cadd]

I made some plywood clamps to hold the bassbar in position . I don`t think I invented them .The idea was thap no matter which way you cut plywood it will have the same flexibility . About 1/2 inch thick ply to fit right around the widest parts .At the side is a section to touch the bent middle finger for the lowest section and the highest section has a hook for the forefinger . All shaped in the plywood. Over the bassbar is a cork cushion. The clamp is opened and closed with the right hand .The left hand holds the plate and steadies the end of the clamp . The clamps don`t weigh all that much . Each one needs to fit in it`s correct position .
I shaped the bassbar by using your triangular beam idea from your excellent book .
I think it`s in your book .A straight line plus two shorter lines to the highest point.That gave plenty of measurements to achieve the subtle curves on the actual bassbar.
Cutting the curve after numerous pencil marks I used a 2 inch wide bladed Japanese chisel . Slicing sideways with my left thumb doing all the sideways pressure was much nicer then any planing . A lot of videos show gouges and chisels being pushed and jumping out past the cut .It just looks dangerous and out of control .

[Michael Darnton]

It sounds like you made traditional bar clamps, which are like clothespins:

https://m.media-amazon.com/images/I/71DY+0nC3+L._AC_SL1500_.jpg

Yes, they worked fine for a couple of hundered years!
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[John Cadd]

I had not seen those clothes pegs photos . I must have invented mine then .If you take a top plate and draw right around to leave two ends on one side. The prising apart ,vertically one handed ,will keep it free to move until allowing the spring to close on the bassbar. The pegs arrangement would need both hands to hold the peg. That seemed very awkward .

[Michael Darnton]

Here's an ancient Maestronet thread with some good examples:
https://maestronet.com/forum/index.php?/topic/321397-bass-bar-clamps/

Not like my literal clothespin pic. :-)
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