David Truscott Posted March 4, 2016 Author Report Share Posted March 4, 2016 Desirable for what? I speculate that 300 years can do a lot to 1mm thick wood. If someone ever wanted to do a bench copy of a 300 year old violin, I would imagine. It's subtle, but personally, I think it's a nice effect. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 4, 2016 Author Report Share Posted March 4, 2016 What about instruments with the conical hole in the center of the back, does anyone know if the plate balances there? I've been wanting to experiment with graduating a plate to balance on a spike that would fit such a hole, but can't bring myself to drill an unsightly hole in the center of the back. There are definitely nice instruments that have a pretty deep pinprick in the back center. (I know that's not what you're talking about.) I've known makers who've subscribed to the idea that the plate should balance around that point, and could actually balance the plate on the point of their scratch awl and spin it around! Quote Link to comment Share on other sites More sharing options...
David Burgess Posted March 4, 2016 Report Share Posted March 4, 2016 I'm interested if anyone has a good technique to being able to get the ribs convex from top to bottom. I've seen this effect on some nice Cremonese instruments, and have heard others talk about this phenomenon as being desireable. Interestingly enough, using the wedge clamp method on the c-bouts can get this effect, but I often find that the ribs for the upper and lower bouts always end up a little bit concave with my current construction methods. No problem. Glue the ribs to the blocks when the ribs are slightly moist, or scrape them to the profile you want after installation. Not that I'm in any way recommending either. When we see convex ribs on the upper and lower bouts of historical instruments, I think that's mostly due to contraction of the plates on each side of the rib, over time. Quote Link to comment Share on other sites More sharing options...
nathan slobodkin Posted March 4, 2016 Report Share Posted March 4, 2016 5/6 hrs minimum ,it will still be tender though, I tried speeding up the process once with some added heat ....not good[/quote James, What kind of glue are you using that requires that much clamp time? I routinely take clamps off after two hours except for center joints and neck sets when I might give it an extra hour .On large patches I leave them for days but that is a special situation. Quote Link to comment Share on other sites More sharing options...
James M. Jones Posted March 5, 2016 Report Share Posted March 5, 2016 5/6 hrs minimum ,it will still be tender though, I tried speeding up the process once with some added heat ....not good[/quote James, What kind of glue are you using that requires that much clamp time? I routinely take clamps off after two hours except for center joints and neck sets when I might give it an extra hour .On large patches I leave them for days but that is a special situation. probably the same sort of stuff you use, I don't know that I do need that much time , just playing it safe before applying stress. I am comfortable pulling the clamps sooner , it's the working with it and stressing things that makes me nervous, I've had a few blow outs from pushing the limits. Quote Link to comment Share on other sites More sharing options...
Johnmasters Posted March 5, 2016 Report Share Posted March 5, 2016 Nathan, thanks for the correction. I disagree with John above, and i bet he hasn't even tried the dowel and string method. No, I started making decades before the re-discovery of the old dowel and string method. If YOU disagree with the end-clamping of the perimeter... have YOU ever tried it? You may have to wiggle things to get them to seat. It may not work well with thin moulds. I always use full-thickness moulds. I could never understand why it was not common practice. Probably too many people trying to copy old methods too slavishly. Quote Link to comment Share on other sites More sharing options...
Johnmasters Posted March 5, 2016 Report Share Posted March 5, 2016 "... That C bout clamping block method is the prescribed one at Newark, and as I said to P.Bowers 22 years ago, it doesn't work. Sure, some people insist on doing exactly what they were told, but it really doesn't work effectively. The clamping forces are not directed to the glue line, but into the middle of the c bout, and if you are doing corner shapes like Da Salo it will work even less well. If you've made it work, then fine. I'd suggest using the dowels and string method. ...." It works just fine if you add ridges (very small steps) to the slant sides of the trapezoid. This is easily done with a bandsaw. Then the trapezoidal block can 'lock' on the rib and only one central clamp is needed. Also you can adjust for more pressure by sanding the rib if it is not square. You can also shape the trapezoid so that the ends are perpendicular to the rib. Quote Link to comment Share on other sites More sharing options...
Johnmasters Posted March 5, 2016 Report Share Posted March 5, 2016 How long would you let this clamp if you're eager to move on? I'm planning on a couple hours until I start the linings. I used to make three at a time to make best use of various clamps and methods. Quote Link to comment Share on other sites More sharing options...
Johnmasters Posted March 5, 2016 Report Share Posted March 5, 2016 I'm interested if anyone has a good technique to being able to get the ribs convex from top to bottom. I've seen this effect on some nice Cremonese instruments, and have heard others talk about this phenomenon as being desireable. I may have misread or misunderstood you, David. I thought at first that you meant rib height. As for the rib depth having a convex curve, I thought that clamping while wet, and using a thin mould was supposed to do this as the wood shrank. But .. as said above, I use a full-thickness mould, one piece only and does not disassemble. It works fine. Also, I glue it up with sheets of plywood. I did a couple of violas once as you say. Just make the first sheets total half an inch thinner than the end rib heights. Then take quarter-inch plywood and bend over whatever central spacers you wish. Gorrilla glue works well to glue the ends as it has gap-filling properties. Then shim the ends and cut it out. I showed my two violas to Carl Becker Jr when I did it. He looked with interest but made no comments. It certainly does not create a tone issue. The bend helps the longitudinal arch in part, the centes of the ribs were quite high without making the chinrest end unmanageable. I agree with Mr. Truscott. They looked handsome in profile. Quote Link to comment Share on other sites More sharing options...
Nick Allen Posted March 5, 2016 Report Share Posted March 5, 2016 I too used the end caul trapeziod method and it worked great. The ribs made full contact, even though they weren't bent to exact shape beforehand. I don't really see why this is such a hot topic. Very simple concept, very simple execution. If someone thinks that one method is superior, despite the same results, they may have problems outside of luthery that they should address. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 6, 2016 Author Report Share Posted March 6, 2016 But .. as said above, I use a full-thickness mould, one piece only and does not disassemble. It works fine. Also, I glue it up with sheets of plywood. I did a couple of violas once as you say. Just make the first sheets total half an inch thinner than the end rib heights. Then take quarter-inch plywood and bend over whatever central spacers you wish. Gorrilla glue works well to glue the ends as it has gap-filling properties. Then shim the ends and cut it out. I'm having trouble visualizing this.. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 6, 2016 Author Report Share Posted March 6, 2016 No problem. Glue the ribs to the blocks when the ribs are slightly moist, or scrape them to the profile you want after installation. Not that I'm in any way recommending either. When we see convex ribs on the upper and lower bouts of historical instruments, I think that's mostly due to contraction of the plates on each side of the rib, over time. Thanks David! Since I had already glued the ribs, I went for the latter to good results. Quote Link to comment Share on other sites More sharing options...
Johnmasters Posted March 6, 2016 Report Share Posted March 6, 2016 I'm having trouble visualizing this.. I mean that the surface of the mould is flush with the rib edges. And you can make the mould have the profile of a double-convex lens. You can do the same for just the top-upper-bout for a violin. When the ribs are finished and before the blocks are cut away, one can lay a medium coarse file on the surface of the mould and smooth the excess ribs flush with the mould surface. It is very fast and percise. (Why go to all the trouble to try to plane a particular taper? The bent upper quarter inch plywood piece bends pretty close to a parabola, Those eager to contradict can look up "the cantileaver beam" and see that it is a cubic equation, I believe.) Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 17, 2016 Author Report Share Posted March 17, 2016 Progress Pics Update: Rough Gouging I've still yet to find a way to hold the plates that I'm completely happy with. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 17, 2016 Author Report Share Posted March 17, 2016 Progress Pics: Starting the outline. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 17, 2016 Author Report Share Posted March 17, 2016 I know its not customary, but I like to remove the mould before I start the outline . I don't mind if the ribs lose their exact shape. I mark the corners, length, and c-bouts, so that I can get a very close approximation of where everything should be. This way, I can release any tension, if any, and it's much easier to get the ribs to register properly with my finished plates. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 17, 2016 Author Report Share Posted March 17, 2016 Purfling progress pics: I thought the light shining through the purfling channel was a cool picture. Quote Link to comment Share on other sites More sharing options...
~ Ben Conover Posted March 17, 2016 Report Share Posted March 17, 2016 David, I see those lining clamps were 'New Zealand made', got a link to them ?If so perhaps you could PM me, I'm trying to use this site less.Thanks. Quote Link to comment Share on other sites More sharing options...
Nick Allen Posted March 17, 2016 Report Share Posted March 17, 2016 Yeah. I was curious aboot those lining clamps as well. Quote Link to comment Share on other sites More sharing options...
David Truscott Posted March 17, 2016 Author Report Share Posted March 17, 2016 I've been getting a lot of PM's about the clamps, so here's a link for everybody that's interested: http://www.nelsonhobby.com/miniature_c_clamps.php Very reasonable in price I might add. This is the only place I've found them. (After a LONG exhaustive search.) Quote Link to comment Share on other sites More sharing options...
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