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PostPosted: Tue Dec 23, 2008 10:23 pm 
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Cocobolo
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Hey gang -

I have a Taz Blackwood grand concert cutaway in the works. Body is closed, all is good....except for a little surface crack running perpendicular to the grain, just before the "peak" of the cutaway bend. Happened while pipe-bending, but managed to finish the bend without splitting any further. As is, I believe I can sand it out without any trouble...just wondered about preventing that crack from continuing in the future.

Is it a good idea to maybe spritz a light coat of shellac over the area, then flood the crack with CA prior to sealing and finishing? Thanks in advance for any input!

Happy Holidays to all!


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PostPosted: Wed Dec 24, 2008 12:13 am 
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Brazilian Rosewood
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Back it up.

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PostPosted: Wed Dec 24, 2008 1:32 am 
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Cocobolo
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Howard Klepper wrote:
Back it up.


Reinforce from the inside? Did that, probably a little more than I needed to!


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PostPosted: Wed Dec 24, 2008 9:01 am 
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Old Growth Brazilian
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reinforce the outside of the bend. use a slat on the outside while bending to give support to the outside. That is what Howard means by backing up the bend. The pipe will provide support on the inside. it is the outside where the stress will try to relieve at.


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PostPosted: Wed Dec 24, 2008 11:19 am 
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Cocobolo
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Slat? Another piece of bendable wood?


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PostPosted: Wed Dec 24, 2008 11:23 am 
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Old Growth Brazilian
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no a thin piece of spring or stainless steel used to back up the out side of the bend.

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Side_Bending_Strap_Detail2.jpg


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PostPosted: Wed Dec 24, 2008 12:19 pm 
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I like tear-drop dulcimers using one piece sides and because I like to experiment I have used sides up to about .190. The bending needed is roughly equivalent to bending a cutaway.

My point is that I use wood cauls and small c-clamps to clamp the slat to the wood to provide the best possible amount of support(no slippage, keeps slat tight against the wood).

I am not a pro but it works for me.

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PostPosted: Wed Dec 24, 2008 12:31 pm 
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Brazilian Rosewood
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I meant patch it well on the inside of the guitar. Do flood the outside with CA. Then sand the outside to as smooth a curve as you can get.

Are we talking Venetian or Florentine?

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PostPosted: Wed Dec 24, 2008 12:52 pm 
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Cocobolo
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Howard Klepper wrote:
I meant patch it well on the inside of the guitar. Do flood the outside with CA. Then sand the outside to as smooth a curve as you can get.

Are we talking Venetian or Florentine?


Thanks for the reply, Howard. It's a Venetian and I did reinforce the inside. The crack is not that big, more of a separation and only on the outside of the bend, but right in the very middle of the rib. Enough to notice if you look close...I just didn't want a full-fledged SPLIT somewhere down the road. I figured filling with CA would be the solution but wondered if that would turn into a visible spot under the finish, which is why I was asking about a light coat of shellac over the entire area before CA.

Will try on a piece of scrap beforehand. Thanks again!

Jon

PS...do luthiers believe in Santa Cauls?


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PostPosted: Wed Dec 24, 2008 12:58 pm 
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Old Growth Brazilian
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If not vissible on the inside i am guessing that the crack is at the edge of aome curl figure where the direction of the grain changes dramaticly. But that is just a guess.


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PostPosted: Fri Dec 26, 2008 6:42 pm 
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I had a very small, 3/8" crack right at the cutaway on my OMC I built last year. I did just as Howard suggested. I reinforced the inner side of the rim then flooded the crack with CA. Once sanded and finished, the crack is not visible except a very close inspection and even then, one has to know what to look for. In fact, I have never noticed the crack again since I finished the guitar, and I have been playing it almost daily since June this year.

Howard Klepper wrote:
I meant patch it well on the inside of the guitar. Do flood the outside with CA. Then sand the outside to as smooth a curve as you can get.


Ken

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