 The Clarinet BBoard
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Author: perryg114
Date: 2007-10-28 19:52
Attachment: tenon crack with annotations.jpg (85k)
Attachment: Crack cropped and enhanced.jpg (419k)
Ok take a look at this crack. This one was hard to find and I really did not want to find one. It is on the lower tenon joint, the one that holds the bell. The crack extends about .5 in below the tenon cut down into the bore. It is only a through crack in the tenon itself. It is a very small crack and seems to be stable and if the crack got bigger it would not run into a tone hole. The bell compresses this crack so I don't know if it will grow or not. I think it would take a while before it caused a problem even if left alone. The question is what should be done to it if anything? I would think this would be a good one for super glue since the crack is so thin that epoxy would not penetrate. I think the crack is so thin that wood powder would not penetrate into the crack. I did some reading on super glue (cyanoacrylate) and it looks like it will work but it does weaken over time with water exposure. Looks like the crack started at the tip of the tenon where the chip is. The first photo points to the crack and the chip. Here is a link about super glue type adhesives.
http://www.devicelink.com/mddi/archive/99/09/006.html
Perry
Post Edited (2007-10-28 20:11)
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Author: Chris P
Date: 2007-10-28 20:44
The thing is though, once you have superglued it up and it's all tight, how will water penetrate the crack once it's all sealed (and weaken the superglue)?
There seems to be a lot of worry over very little.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: perryg114
Date: 2007-10-28 21:23
I hope you are correct. I figured the glue would be exposed to the spit coming down the bore and eventually weaken. Any particular kind of super glue that you use? At NASA where I work they use the stuff to glue on strain gages to test space hardware but it only lasts about a year before they pop off due to moisture unless they are overcoated. Maybe superglue with some sort of sealer on top. You have more experience with this stuff than me and it sounds like you have had good luck with it. Any tips would be helpful. I have a couple of junk horns to practice on. One is already going to be a lamp for a friend of mine. It has a much worse crack on the lower tenon. I bought it for a lamp and expected it to not be worth fixing. The crack is not the reason for the lamp status though. Someone removed all the tone hole inserts or was in the process of replacing them and abandoned the process. The other is the Martin that I talked about in my last tenon crack post. Maybe I will close the crack with the glue then fab a tenon cap for it.
What is the oldest superglue repair you have made and how is it holding up?
Perry
Post Edited (2007-10-28 21:25)
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Author: Chris P
Date: 2007-10-28 22:32
The oldest superglued cracks on clarinets I did (and still have) were back in 1987 on my old Centered Tone set, all of which have still held up well - especially the Bb which has a split top joint right through to the bore which hasn't opened up since, and is still airtight.
With wood and clarinet joints in particular, the crack will be held closed by the pressure of the wood, and the superglue as a filler will just make sure it's not only airtight, but adheres the crack together and can only fail if the crack is already contaminated with oil or grease prior to glueing.
And as for spit down the bore, the majority of moisture in a clarinet bore is condensation from the breath (which is distilled water) and hardly any saliva.
Though I'd assume if anyone likes a few stiff drinks before or during playing, then there's a certain amount of alcohol which will also condense in the bore and will only act as a degreasing agent.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: BobD
Date: 2007-10-28 22:57
Yes, and alcohol and water are "miscible" (mutually dissolvable) so it will help remove water too.
Bob Draznik
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Author: perryg114
Date: 2007-10-28 23:11
Ok so what is the solvent of choice for getting all the oil out of the crack. I have acetone, MEK, Ethyl Alcohol 200 proof (yes the good stuff), and maybe some freon 113. I suppose I could soak the joint in solvent and put it in an ultrasonic bath.
Perry
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Author: C2thew
Date: 2007-10-29 08:20
wouldn't soaking the joint just make the wood absorb too much water too fast, creating either a new crack or expanding the existing one?
you can always try wax. wax works well
Our inventions are wont to be pretty toys, which distract our attention from serious things. they are but improved means to an unimproved end, an end which was already but too easy to arrive as railroads lead to Boston to New York
-Walden; Henry Thoreau
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Author: clarnibass
Date: 2007-10-29 09:07
No, at least not if it's made of grenadilla, which soaks water so slowly and so little that unless it is soaked for very long it would be meaningless. Also it won't make it crack, since wood will crack from being too dry, or differences in humidity (and maybe tempeture) between the outside and the inside. Play a lot, don't swab and let your clarinet stand in a dry area, and I can almost guarantee it will crack!
But - I wouldn't soak it anyway, because how is that going to help? You only want to clean the crack so why soak the entire joint?
Post Edited (2007-10-29 09:08)
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Author: Chris P
Date: 2007-10-29 10:26
One thing you don't want to use is wax. Glue won't stick to wax, so that's a bad idea.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Gordon (NZ)
Date: 2007-10-29 12:07
For good penetration...
Shove a wooden tool handle in the end, and use it to force the crack apart. While it is apart, wick superglue into the opened crack. Remove the handle. Clean up excess glue. And forget it for the next few decades.
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Author: Chris P
Date: 2007-10-29 13:48
Yep. The pressure of the wood will be enough to keep it all tight once the superglue is in there.
Once the superglue is in and has gone off, it'll be unlikely to open up again as it'll be under compression - unless you get something (such as the wrong stand) jammed in the tenon causing it to split.
If the crack isn't contaminated with grease (though do degrease the surface of the bore and tenon where the crack is) then the glue will run into it (in a capillary action kinda way) and stay there.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: perryg114
Date: 2007-11-01 15:40
I stand corrected and bow to the crack repair experts. I tried the super glue crack fix on a junk horn with a big open crack that went from the lower bell tenon to just south of the lower most tone hole. The crack was about 1mm wide at the end of the tenon with it coming to a close just shy of the lower most tone hole. I put some super glue inside the bore along the length of the crack and pushed it together and it bonded it back together good as new. Later I tried to pull it back apart and could not do it with both my index fingers jammed in the bore and pulling for all I was worth. I did put the bell back on while it cured which held the crack together. I wish I had taken before and after photos.
Perry
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