fyoder - Posted - 08/18/2010:  17:48:30

On the old fiddle I'm repairing, there's a sound post patch that has been cracked through. It isn't level, so I thought I might level it before patching the patch, then it occurred to me that doing so might remove it all together, since it may be that it's not level because it's not inset, just stuck on to the surface.

I'll attach a picture. I'll either be patching the patch, or else removing it and patching anew. Does the patch need to be that big? That seems to cover an area beyond that required by the sound post. I would like to remove as little original wood as possible in the process, whatever the minimum is to do a good patch.

Thanks.

old sound post patch

hardykefes - Posted - 08/18/2010:  18:26:42

This crack looks marginal to me. Actually you could get away without a patch on this repair by adding cleats. The soundpost, correctly setup, should not meet the crack. But this depends on how the fiddle sounds. May be it is a very trebly instrument and someone moved the post almost outside the foot of the bridge. If the instrument is quite balanced the post should be at least 4 to 6 mm inwards of the crack and cleats could be sufficient if the glue is strong and also a strong glue is used for the crack itself.

Don't take my word for it, I am judging by the picture. I would of cause see and feel the instrument and tap-test the top for a good judgement.

fyoder - Posted - 08/18/2010:  19:07:10

The instrument was a bit oddly setup judging from the marks. On the top, it appears the feet of the bridge were above the little indents on inner f hole, and the marks on the patch suggest the sound post was right on the crack, just a bit behind where one of the feet would have been, but pretty close to where the foot would be if one set it up with the bridge positioned exactly between the indents.

Higher rez image here: fyoder.com/vp/violin_restorati...ginal.jpg

Here's my crack map: fyoder.com/vp/violin_restorati...kmap2.jpg

From that you can see that the crack running through it is actually the continuation of a much bigger crack right from the bottom.

Edited by - fyoder on 08/18/2010 19:13:20

giannaviolins - Posted - 08/18/2010:  19:52:46

It's pretty bad. If pushed, I'd probably see whether I could open the repairs with flexing. If not, I'd level the entire inside surface, then put a maple patch overlay at the post, put vellum reinforcements at the end and neck blocks, and all along the saddle crack to the post. Bar crack - hmm. Work. Might just put in a strong bar and then lay vellum strips at the contact points, bent to glue onto bar & top. Not very wide, just enough to reduce the stress riser at the bar.

I hope that makes sense. I'm tired and have a bandaged up hand. Nice deep gouge hole, probably should have stitched it but I'm out of sutures.
Superglue will do.

FiddleDoug - Posted - 08/18/2010:  20:43:46

Is that penciled long rectangle at M6 the location of the bass bar? If it is, it's wrong. Wrong angle and size. I'd consider linen patches instead of vellum.

fyoder - Posted - 08/18/2010:  21:51:31

Ouch, hope you're ok voodoo. I guess that one application where super glue is better than hide glue.

Maple? Interesting. I was thinking of offsetting the grain of the patch a bit for a little extra strength. Aligning it certainly didn't seem to do much for strength in the original patch.

I haven't run across reference to use of vellum reinforcements, but I like the sound of it. If you have any tips or can point me in the direction of some, I would appreciate it. Please be sure to disinfect your wound first and get some rest. Obviously I feel concern for you as a fellow human being, but you're too valuable a resource to succumb to infection.

Yes, FiddleDoug, the pencilled in location is for the bass bar. It is non-standard, outlined in a video by a fellow named Mitch Dickson. He used to sell it on ebay, might still. 7" long, centred on the point below the bass side foot of the bridge, with the top tip at the the centre vertical line of the top, thus defining the unusual angle. 3/4" high at centre, sloping to 1/2" at the ends. I wanted to try it, though wasn't planning on it for this project until I realized that the angle would solve a lot of problems with putting a bass bar over cleats.

Linen vs. vellum? This is something I need to learn about. I imagine linen would be easier to aquire than vellum, unless the term means something other in this context than the prepared animal skin monks used to scribe on. Though a search on "vellum parchment" on ebay turns up a couple of sellers of Real Medieval Parchment/Vellum.

Thanks very much, guys, interesting stuff.

Edit: Actually, I have read of people using parchment, that's what you mean by vellum, voodoo? It isn't in the forefront of my brain because I couldn't help but feel sceptical with regard to strength -- but then, I've never seen real, old school vellum/parchment, just fancy paper called that which may be why I have some resistance to the concept.

Edited by - fyoder on 08/18/2010 22:18:50

giannaviolins - Posted - 08/19/2010:  03:55:48

Drafting paper. Long rag fibers, non-acid. Vellum, modern usage. Adds little mass.

Bar over cleats a pain, and I'm not convinced it does much. Bar crack much less likely to reopen anyway.

Make sure the saddle is loose at the ends.

I've been known to inlay a piece of spruce with grain at right angles to normal grain across bad saddle cracks. I just put a piece across the whole box.

I know the bar. It's not really that good, gives a deep sound in first position.

My hand will be fine. Nice clean tool, plenty of blood washed out anything, I knocked the scroll away instantly to avoid getting blood stains on it. Checked the cut for proximity to anything important, then applied pressure. Took about 20 minutes to stop profuse bleeding, not too bad. Then butterfly w/superglue and a pressure bandage. Held up fine on way home in spite of clutch use on the motorcycle, will be fine. I'd have done a proper suture if I wasn't out, but that's OK. I find the sensation of driving a needle through my flesh distracting. No biggie.

I'm more concerned about being able to golf and swim than I am about infection.

On the maple patch, I write of just a veneer, as Curtin uses. My suggestions are for rapid repair of a marginal instrument, rather than top-level repair of a fine machine. Something to get it going that will likely make it work well enough.

Have fun

FiddleDoug - Posted - 08/19/2010:  05:05:32

I don't really find it a problem fitting a bass bar over cleats. It's all in the sequence.
1) Glue the crack- no cleats.
2) Fit the new bass bar, but don't glue in.
3) Cleat the crack. Make the cleats long enough to extend under both sides of the bar. Don't put cleats near the ends of the bar where the bar gets low.
4) Mark the bar for the location of the cleats, and cut notches in the bar to fit over the cleats.
5) Glue in the bar.

giannaviolins - Posted - 08/19/2010:  06:08:20

It's not a problem, but it's time. This instrument doesn't rate time.

I'm not convinced that cleats under the bar do anything at all that reinforcing the beam contact points to avoid stress risers won't do. I'm pretty convinced that's a good thing to do anyway, possibly even acoustically.

FiddleDoug - Posted - 08/19/2010:  07:15:45

I totally agree about the time involved, and that this instrument wouldn't rate the time if you were doing it for pay. As a practice exercise, it's the right way to do it.

hardykefes - Posted - 08/19/2010:  07:31:43

The new pictures shed much more light onto the problem.
Now I would use a patch for soundpost, spruce, grain perpendicular to existing, about 1.5 x 1 inch.
Bass bar, don't use this funky bar you are suggesting. It is not that good. Make sure you don't put that much tension onto the top with the bass bar design. The crack than should hold without cleats, although it is not really a problem to put them under the bar. I don't find them really necessary. Good (little thicker) hide glue is actually stronger than the wood itself and the top would crack anywhere but at the glued location.
I don't like vellum or any other similar material to "fix it up". I rather stick to conventional methods, even if it means more time.
Don't use superglue !!! This glue does not belong on a fiddle. Hide glue can always be applied to old hide glue and has enough strength. If the superglue does not hold or breaks open again you can't use anything on this surface anymore that would hold. Superglue would also go into the fibers and make them unusable for any other glue application.

transplant - Posted - 08/19/2010:  08:31:01

Hardy, how do you feel about reinforcing the E notch on a bridge with superglue? It sure is a lot quicker than the traditional little slip of vellum or drum skin. In that application, soaking into the fibers is useful to strengthen the resulting matrix.

About everywhere else, I agree completely. Superglue only damages cracks further, and complicates future repairs beyond belief.

hardykefes - Posted - 08/19/2010:  09:13:23

I have not tried that but used superglue to attach the little piece of parchment for reinforcing the bridge at the e-string.
The bridge will be replaced eventually and there is no structural strength necessary at this location other then holding the parchment in place.
I could not find a tonal influence.

giannaviolins - Posted - 08/19/2010:  10:53:35

"Vellum" is a conventional method. used to parchement. See it all the time on old repairs.

Long organic fibers held together by glue - that's wood or vellum, either one. Same thing, except vellum is consistent & very thin.

I've seen a fair number of people drip a little superglue in the notches on bridges, all the notches.

hardykefes - Posted - 08/19/2010:  11:54:22

I have seen vellum too, but I take the freedom not to like it. For the single reason if it comes loose on the edges for some reason it creates funny noise which can drive you insane if you don't know where it is coming from. It will only happen at certain frequencies / notes.

fyoder - Posted - 08/19/2010:  18:16:56

Interesting article on the history of superglue for wounds

straightdope.com/columns/read/...n-vietnam

Glad to hear your worst concerns are your golf game and swimming, voodoo.

And thanks, all for the interesting comments. You are, of course, correct FiddleDoug, I shouldn't be lazy and should do a proper bass bar, given that this is primarily an educational exercise, and one aimed in large part at gaining experience to work on another fiddle I have which I wouldn't in a million years put a non-standard bass bar on.

And thanks, voodoo, for the comment regarding its performance. Mitch Dickson is quite a character, and I wouldn't be at all surprised if he is delighted with a bass bar that turned the bass up to 11 in first position while not giving a tinker's cuss about what it did to performance in higher positions. I've got a violin kit that I may still try it out on just to see. Maybe finish it with sparkles, or do as Mitch does and inlay tailpiece and fingerboard with mother of pearl from oyster shells, and, as he says "put some lipstick on this pig."

With regards to how to do it, I think without cleats and using strips of either linen or vellum along the sides of the bar over the cracks. I can see how FiddleDoug's approach would work, but getting a perfect fit over the cleats would be difficult, and a less than perfect fit would leave the bar in uneven contact with the surface. It's possible that doesn't make a bit of difference in reality, but if I can avoid it and still do a good repair, I will.

Not adding any reinforcement, as hardykefes suggests, would also make me feel a bit uncomfortable. You can't argue that the join is stronger than the wood, but that's only true to the depth the glue penetrates. If the same stresses apply that created the cracks initially it might be good to have some reinforcement in that area. It's hard to say, since it isn't going to be the same bass bar, and it will be different in type as well, since the original was carved from the top.

And thanks Hardy for your points on superglue. Handy maybe for bridge notches and when you stab yourself, but it can't be posted in enough places to avoid using it for violin repair. I believe the fingerboard on this fiddle was glued on with it, and it was a ***** to get off.

With regard to linen vs. vellum, am I right in thinking that linen, having an inherent structure, is stronger than vellum, whereas the advantage of vellum is that it's lighter? Keeping in mind Hardy's concern for loose edges being a potential source of annoying noises.

With regard to the patch, I'm inclined in the direction Hardy mentions, though does it make a difference the angle of the offset? For some reason I'm partial to 45 degrees, perhaps because I have been orienting my cleats that way (though some of these will have to be removed for the bass bar if I do as I'm thinking -- no loss, as these were amongst my first and worst cleats).

Thanks again for your input, it's very helpful and much appreciated.

Edited by - fyoder on 08/19/2010 18:19:40

FiddleDoug - Posted - 08/19/2010:  19:11:55

Always an interesting exercise in getting different opinions from different luthiers on solving a problem. Much of my learning has been through Hans Nebel, at summer workshops for the past 5 summers. He was very good friends with Hans Weisshaar, and also worked with Saconni for many years. Some of his opinions on restoration vary a bit from those in the Weisshaar. To paraphrase the way he puts it -"Weisshaar wrote the book many years ago, and some things can change a bit as we learn more."
Some people still use animal parchment (different from vegetable vellum) for reinforcements. Weissharr warns against using it. Linen is also a historic reinforcement material (Strad used it on some cello ribs). Lots of opinions and slightly different ways of doing things.

giannaviolins - Posted - 08/19/2010:  19:16:40

I always use very strong fresh glue on vellum.

I knew a fellow, very well trained, who preferred brown paper bag material. I don't know how that holds up, but it soaks up bunches of glue!!!

Just tack the top on for experiments. Glue stick will hold for long enough to play and see what something does!

Search the patent office files for amazing bass bars.

fyoder - Posted - 09/08/2010:  02:22:07

I've done an eyebrow patch, and am starting on the sound post patch. The thought occurred to me that I could patch the bass bar cracks as well, maybe one patch in the upper bout and two in the lower.

I was thinking about going the linen strip route, but it occurs to me that I could put cleats under the bass bar rather easily by making them part of the bass bar, fitted exactly, and attached at the same time, sort of a bass bar with feet.

Which would sound better? Are patches worse for the sound of the fiddle than cleats? Or vice versa?

FiddleDoug - Posted - 09/08/2010:  05:22:28

Patches imply removing original wood, which is only done when absolutely necessary. Trying to fit a "bassbar with feet" would be a nightmare. And fitting a bassbar than gluing cleats onto it wouldn't be any better. It's very likely that the ends of the cleats wouldn't fit correctly. See my earlier post on this subject for the correct sequence.

Edited by - FiddleDoug on 09/08/2010 05:24:23

fyoder - Posted - 09/08/2010:  15:45:41

Thanks, Doug. Perhaps I will become less patch-happy once I'm done the sound post patch. I'm sure the novelty wears off.

Putting a bass bar over cleats sounds like an ugly solution at first, but I think it's made worse when I imagine trying to do it over my trimmed mutant cleats. Might be at least possible to get the sort of fit I want starting with untrimmed, clean, very geometric cleats, then doing the mutantification (or rather, trimming) as the very last step once everything was in place. Still a PITA, but I can at least conceive of it being successful.

Thinking more on preinstalling the cleats in the bar, I think it is something I could do quite successfully if I were an android with the sort of perception and precision of Data on Star Trek Next Generation, otherwise even slight imperfections could yield very bad results. I'll heed your advice on this one, at least until I can do a sound post patch without chalk just from looking at the negative of the depression and faithfully reproducing the positive of the patch. Perhaps in my next life if I'm reincarnated as an advanced android.

Still interested in the question of which is better with regard to sound quality, patches or cleats though. Theoretically, I'd guess patches with grain oriented in same direction as the top. It should interfere less with resonance, since it becomes a part of the top, not an extraneous stuck on bit, or worse a constellation of extraneous stuck on bits.

I'm orienting the sound post patch off by 45 degrees, but that feels like a compromise in the interests of strength given that this top has a demonstrated propensity towards splitting.

Though I was right, the original 'patch' was just stuck on and not inset at all, so who knows, perhaps if it had been inset properly it might not have failed even oriented same as top. As it was, if no corresponding adjustment had been made to the original sound post, that 'patch' may have made the causal factor worse by making the top thicker, the pressure greater. But who knows, just speculation, and I don't feel like taking chances, so am orienting it at an angle.

Thanks again :-)

Edited by - fyoder on 09/08/2010 15:49:40

FiddleDoug - Posted - 09/08/2010:  19:32:16

It's really not that hard. The ends of the cleats are staggered slightly to avoid any possible stress lines. A slight amount of clearance in the cleat cutouts in the bar is actually necessary, because the bar and the cleats swell slightly with the hot, hide glue. Also, there are no cleats out near the end of the bar where it's only a couple of mm high.

fyoder - Posted - 09/08/2010:  20:00:22

Interesting! And the lack of tight coupling doesn't lead to buzzing or anything like that, nor diminished efficacy of the bass bar? I would have thought that one would want as tight a fit as possible, basically making them all 'of a part' so to speak. But I can see how that would be difficult working to fine tolerances having to account for an uncertain variable like degree of glue swell.

Good to know about the staggering. The aesthetic impulse would be to line them all up neatly. Thanks.

FiddleDoug - Posted - 09/08/2010:  20:26:22

Things only buzz if they are loose, and can move. I don't think that there are any negatives, as long as the rest of the bar is fitted properly. A good application of hide glue during the bass bar gluing fills most of the tiny gaps.

fyoder - Posted - 09/09/2010:  19:40:40

Thanks, Doug, you've saved me some grief down the road, much appreciated.

fyoder - Posted - 09/18/2010:  13:08:33

Sound post patch completed. It's not clear from the before/after image, but I've made the general area of the sound post about a millimetre thicker than the thickness of the top.

Higher rez image here: fyoder.com/vp/violin_restorati...large.jpg

sound post patch before/after

woodwiz - Posted - 09/18/2010:  14:28:16

I haven't been following this thread, or I would have commented on the grain angle earlier.

Most people just angle the patch 2 or 3 grain lines. This reduced the chance of further splitting.

Rotating the patch more presents two problems. First, it stiffens the area substantially. This could be good or bad, but if you are trying to keep the original sound, it probably won't help.

Second problem is that wood expands and contracts approximately ten times as much across the grain as with it. This means that the two pieces of wood with crossed grain will tend to fight each other as the humidity changes. The more the angle, the more tension is created. That's why, in conventional woodworking its axiomatic that cross grain joints always fail, eventually. The movement shears the glue line.

I don't know how much of a problem this is, because I always use the conventional method, and have never seen an old patch with a large difference in grain angle.

fyoder - Posted - 09/18/2010:  14:59:36

Thanks, Michael, good to know.

I'm of two minds at the moment -- dig it out and do it again, or else leave it and see what happens. Though I wouldn't be comfortable with just two or three grain lines. I've come to think of this top as possessed of a suicidal spirit that will take any opportunity to self-destruct, so if I were to redo it, it would probably be with an eighth turn left. I don't know if a difference of 22 1/2 degrees would make that much of a difference. I'll think about it for a couple of days before deciding.