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Do Cracks Matter?


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Hi all,

I first thought a crack on a violin is a "No-No" Now I change my mind, if the violin is played Okay, (don't know there is a crack. sound normal, well repaired) why should anyone avoid it?

Now I accept crack as I accept a scratch on a piece of furniture . Your comment please.

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Frederick Castle did an interesting experiment in which he created a number of cracks in a violin top and noted the change in sound from each one.

It's all described in "The Peculiarities of violin Tone" but as I remember it the cracks on the treble side had little effect while the cracks outside the bassbar ruined the low frequency response of the instrument. My personal experiences have largely corroborated this with some stiff instruments sounding better with cracks.

The worst acoustic problem with cracks is usually the cleats used to fix them.

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It is obviously better if a violin has no cracks at all ("mint condition"). Every crack is to a degree a disadvantage, whereby it makes a big difference if they have been well repaired, or if generations of vm's have just massaged glue of varying degrees of dirtyness into them. You should also look to see that the arching hasn't been deformed by the crack, since this normaly means that they are open on the inside.

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Hi all,

I first thought a crack on a violin is a "No-No" Now I change my mind, if the violin is played Okay, (don't know there is a crack. sound normal, well repaired) why should anyone avoid it?

Now I accept crack as I accept a scratch on a piece of furniture . Your comment please.

If that "scratch on a piece of furniture" was a crack that went through one of the legs, would you sit on it? Of course cracks matter! In some cases they aren't very critical. In other cases, they can weaken the structure of the instrument, and affect the sound. One thing about cracks is that they only get bigger, not smaller.

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The worst acoustic problem with cracks is usually the cleats used to fix them.

Very interested to hear more on this subject .... are you talking about good cleats, cleats in general, or brontosaurus-sized dods of wood?

I've seen a lot of parchment used on good fiddles, doesn't seem to do much and is often hanging off. Also seen tiny and beautifully round drops of glue used as cleats.

Does anyone have any strong opinions on cleats for table cracks? I assume it's good to keep size and mass to a minimum, and to get a perfect fit, but is there anything else?

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Hi all,

I first thought a crack on a violin is a "No-No" Now I change my mind, if the violin is played Okay, (don't know there is a crack. sound normal, well repaired) why should anyone avoid it?

Now I accept crack as I accept a scratch on a piece of furniture . Your comment please.

Do cracks matter? Sure, but should you not buy a violin because it has a crack? If the violin sounds good, and the crack is repaired properly, buy it (and the instrument is valuable enough). Every really nice instrument I see of a certain age has cracks. Sometimes a lot of them. Cracks do matter, but they are kind of inevitable sometimes. There are also instruments that are a can of worms and I wouldn't buy them because of all the work they need. You just have to make a case by case decision.

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Very interested to hear more on this subject .... are you talking about good cleats, cleats in general, or brontosaurus-sized dods of wood?

I've seen a lot of parchment used on good fiddles, doesn't seem to do much and is often hanging off. Also seen tiny and beautifully round drops of glue used as cleats.

Does anyone have any strong opinions on cleats for table cracks? I assume it's good to keep size and mass to a minimum, and to get a perfect fit, but is there anything else?

The only problem I see with parchment or linen is that it will probably eventually buzz. I use parchment temporarily if there are arch corrections involved as well, but then will replace them with proper cleats. There is an article in the IPCI books that describes the process well so I won't go into it here.

As far as the shape of cleats, we use a dome shape and make them pretty thin. The dome is a pretty strong shape and keeps the crack from flexing and ultimately coming apart again. We use a parallelogram shape so that there isn't any stress along one specific grain line. We will also stagger the cleats so that the stresses are not caused by multiple cleats lined up on one grain line too. Here is a picture. I probably have a better picture floating around here somewhere, but this is basically what I do. I would love to see others' cleats.

post-29575-0-10088200-1319664966_thumb.jpg

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To return to the matter in hand ....

I can't really see the need for anything more than a sliver of good spruce glued tightly across the grain - the long-grain strength of these fibres is immense, and I would have thought any additional mass (like Matthew's domes) is un-necessary structurally, and would dampen the vibrations of the table.

It's good to have a bit more wood to hold onto when shaping the glueing surface of the cleat, but I've been chiselling off most of this bulk once it's in place until I have something like the thickness of a couple of playing cards. I also try to keep the cleats short, though I think the parallelogram is a good concept and I'll adopt it.

Am I worrying unduly about the acoustic effects?

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Before mass, size, shape and style can be effectively discussed, it might be a good idea to consider what a cleat actually does in various applications. If it just "held a crack closed" like a bandaid, there would be little need for much mass at all, would there be?

I personally use different styles for different applications. It's important to consider where the mass (stiffness) is as it pertains to each application/use.

There are a good number of threads past that discuss, and show, various cleat styles and uses, and one that even discusses how they reinforce.

BTW: Although occasionally parchment does come loose, the problem with it, IMHO, is the distortion it can cause to the plate over time and the lack of ability to actually keep the crack closed at the varnish surface.

I personally think linen, and it's properties, has it's place in some rib repairs.

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To return to the matter in hand ....

I can't really see the need for anything more than a sliver of good spruce glued tightly across the grain - the long-grain strength of these fibres is immense, and I would have thought any additional mass (like Matthew's domes) is un-necessary structurally, and would dampen the vibrations of the table.

Without enough thickness to provide significant bending strength, you are only holding one side together. You have made a hinge.

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Before mass, size, shape and style can be effectively discussed, it might be a good idea to consider what a cleat does in various applications. If it just "held a crack closed", there would be little need for much mass at all.

There are a good number of threads past that discuss, and show, various cleat styles and uses.

Also;

I believe that a number of prominent makers and repairmen do not mount cleats with the grain going opposite the direction of the grain of the table.

Due primarily to the difference in expansion/contraction rates.

?

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Also;

I believe that a number of prominent makers and repairmen do not mount cleats with the grain going opposite the direction of the grain of the table.

Due primarily to the difference in expansion/contraction rates.

?

See David's post above and consider the grain orientation pertaining to bending resistance.

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I was specifically asking for advice on cleats to support tidy cracks in the table, (and not in areas which are dangerous structurally). Most of what I see seems far too heavy for the job, and I'd welcome people's twopence ha'porth on this particular issue.

I have a good violin right now with 2 longish but neat cracks in the lower belly - the sound is beautiful and delicate and I don't want to ruin it!

David, at what point does the hinge turn into a support? I would really appreciate a nominal thickness (as it were!)

CT - I can't see how any support can be derived from a cleat that runs in the same orientation as the table grain, unless it's a couple of ml thick ....... I understand the problem of differential shrinkage, and was wondering about a diagonal approach!

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I was specifically asking for advice on cleats to support tidy cracks in the table, (and not in areas which are dangerous structurally). Most of what I see seems far too heavy for the job, and I'd welcome people's twopence ha'porth on this particular issue.

I was addressing that issue (and other issues). Even in the flanks, the wood moves (humidity cycles, vibrations, when someone puts their mitts in the wrong place when grabbing the instrument, etc.). There are certain locations that little reinforcement is required, and I do let some cracks go with little or no reinforcement (if the joint is strong, they are in a stable location, and they have nowhere to spread; like relatively close the edge in the flank).

So, as the wood moves, the top of the crack often opens (unless there is enough resistance to bending). To prevent the "hinging", how thick, and the span, depends a little on where the crack is located, how many cleats are being used, and what the shape of the cleat is (rectangle, diamond, etc.).

It's a good idea to remember cleats are relatively reversible. Yes, I've seen them over-used (too many). "Thinning them out" (removal and replacment of fewer of them) isn't a terrible undertaking.

I probably allow for fewer in certain areas than I once did.

Personally, I'd rather make sure an appropriate amount of reinforcement is applied, rather than having to re-repair the crack.

Personally, I think you may be giving well installed cleats effect on the tone a bit too much consideration.

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See David's post above and consider the grain orientation pertaining to bending resistance.

Yes, I have considered that, I'm making this statement based on what different makers and repairmen have stated here in the past.

A cleat with the proper thickness actually won't hinge along the crack if it isn't broken prior to being installed, plus the fact that most tables that have been glued first, aren't then bent along the crack. A series of cleats along a glued crack - even with the grain going the same direction, will not act as hinges - even though the theoretical strength against bending is way less - unless a similar force that caused the original crack is repeated.

Then too, some repairmen prefer to skew the grain line of the cleat, across a single grain line (or two) from exactly parallel, rather than either exactly parallel, or at 90...

Believe me, I've had to do some soul searching, with regard to this question. It's an interesting one.

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Sorry, there's obviously something wrong with my "TONE" - or is it because there are other rather confrontational threads going on?

I'm not contradicting anyone - I'm asking for advice. I was asking David for a specific guideline - I accept the hinge concept, but I want to ask what would be too thin (hinge) and what would be OK (support).

I feel that it can't take much wood to prevent the crack from opening up due to normal shrinkage (assuming the glue's solid) because there's no long grain shrinkage in the cleat and the fibres are very strong. However I can see that if the top tries to buckle for some reason, then a paper-thin cleat isn't going to provide any resistance. I would just like to know how thin I can go! Matthew's cleats (general purpose I assumed) looked pretty meaty to my eyes ....

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CT - I can't see how any support can be derived from a cleat that runs in the same orientation as the table grain, unless it's a couple of ml thick ....... I understand the problem of differential shrinkage, and was wondering about a diagonal approach!

Well, this is truly a philosophical issue at heart.

Yes, diagonal - about like the bass bar, maybe just a tad less - is another alternative.

The thing you have to think about, though, in my opinion, is what amount of reinforcement is required?

When I first started using cleats, I was taught that 90 degrees to the crack was the strongest possible configuration, which, of course, from a structural standpoint, I believe is correct.

Listening to a another poster, whose opinion I respect, (who will perhaps enter in here and then again, perhaps not) convinced me that this consideration might just take a secondary place behind the consideration of longevity vs strength. And also, you have to factor in, what is the need for that much additional strength for a properly repaired crack?

It's not like in ordinary use the plate will be bending back and forth like a hinge.

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Yes I have wondered about this too ... if the crack is well repaired and sits perfectly, why does it need cleats? A shock which would stress the cleats would surely be just as likely to create another crack.

If the cleat is across the grain and serious expansion/contraction occurs, it's going to prevent proper movement or fall off one side of the crack. If it's with the grain then it's not adding any significant strength to the repaired crack unless it's almost as thick as the table.

Should we revisit the whole idea of cleats ...?

I use linen on ribs for cracks and patches, not sure why I don't use it on the table!

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Sorry, there's obviously something wrong with my "TONE" - or is it because there are other rather confrontational threads going on?

I can't see anything at all wrong with your tone, Martin.

It is ok to disagree, without being confrontational.

Who knows, perhaps if we all just ignore the "confrontational" people, eventually, they may learn to argue without becoming emotionally involved - personally, I enjoy genuine disagreement, It's the only time I ever seem to really learn anything new - providing that neither party gets "butt hurt" that everyone doesn't automatically cede to their all knowing wisdom...

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