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HongDa

Button patch shape

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I'm  preparing to do a button patch on a violin that was repaired before.
Someone had drilled holes between the block and back surface and inserted a piece of wood to try and secure the neck and previously broken button.
I could fill the  drill hole grooves at the ends only or completely for the one on the left, but am thinking if I make the patch wider at the bottom I'll only need to do the ends that extend beyond where the block will be.

Would you choose to do either of these shapes or something different?
In the 2nd diagram I would adjust the straight lines to curve outwards a little. I calculate it would reveal about 3mm new wood from the outside at the corners of the button.
Thanks for any opinions.

 

Hope the pictures come out right. Havn't uploaded anything for a while accept a test.

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post-4943-0-33305500-1429007061_thumb.jpg
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I think I would use patch #1 (on the left) to keep the patch invisible.

 

Is the reason to use #2 to fill the drill holes?  I don't think these holes are big enough to weaken the glue joint between the back and the block significantly.

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Thanks for the reply Brad.

#2 is kind of an excuse to get rid of the left drill hole (excluding it's end) and possibly also add a little shelf to help in supporting  a replacement piece of wood where someone had cut a little of the edge away just at the corner in this picture:
post-4943-0-51973400-1429062589_thumb.jpg
I'm also considering in another post about this where someone mentioned they make their patch a little wider than the button...(I think for extra strength/patch width to the purfling channel?).
I wonder if an extra few mm on either side would make much difference in strength.

What about pulling the line in just enough so it's still invisible; as in the right side of this drawing vs the original left side? Or would you still go with #1 ?
post-4943-0-51922600-1429063456_thumb.jpg

 

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I think that a problem with this shape, as well as with your original #2, are the little rounded angles that appear at the widest points.  I think it will be hard getting a good patch fit in these spots because the shape of the patch bed will change too abruptly there.  The form of the patch bed surface should be a smooth curve in all directions without any discontinuities or abrupt changes.

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Personally, I think the slightly odd shaped patch would end up being more trouble to fit and offer very little advantage, strength wise.  The areas of the patch that taper upwards toward the glue surface would be rather thin by the time they intersected the button cracks anyway, and the glue edges would be closer to exposure of moisture from the players hand, grime, etc. in that area.

 

If you're considering patch significantly wider than the button, you'll either be in for a complicated bed, or application of an ebony collar.  I'm not seeing the need for that in the photos.

 

edit; I notice Brad pointed the fitting problem out while I was writing.

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I agree with Jeff and Brad.  Bear in mind that the theory of a more complicated patch (and theoretically better), but fit worse (due to harder fit) is worse than a simpler better fit patch.  Holy crap, I can barely follow that!!!    Fit is everything.  It trumphs  larger area if you can't fit it better. Trust me, I'm the kinda guy to overthink things.  Basic patch (well fit) in this situation is plenty good enough.   jeff

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Thanks for the replies Brad, Jeffrey and Jeff.
And so I just did it in the usual way.
While I was working on this one; your comment, Jeffrey ".......would be rather thin by the time they intersected the button cracks anyway" was on my mind and I then I realized if I had made it wider then these button cracks would also have become weaker during the work process.......putting the button at more risk of coming off again. I guess that could be another reason not to widen it.

Jeffrey, could you explain more concerning your comment (below)?  Why a more complicated bed OR an ebony collar?
 

 

If you're considering patch significantly wider than the button, you'll either be in for a complicated bed, or application of an ebony collar.

 

 

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If you made the patch wider than the button with a traditional (easier to fit) shape, it would have exposed the patch at the sides of the button.  To cover the exposure there would have required a collar.

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Thanks Jeffrey, I think I understand now you were referring to my patch and what would have been necessary had I made it wider.
I've seen much wider patches before where I guess they were  reenforcing broken edges and/or  making the edge thicker while at the same time restoring the button. If this is accepted and necesarry to do, would a crown still be advisable and the exposure along the edges be something that just has to be lived with?
I have some people come in who sweat so much they need regular touch up in areas where their sweat just eats away at varnish very fast.
I sometimes wonder if that plastic sheeting some people put in these areas is the only solution, but I've never tried the  stuff.
 

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