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Why you want to cap the x-brace
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Author:  Rod True [ Mon Mar 20, 2006 10:57 am ]
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Well, here is a good example of why we cap the joint of the x-brace.



There could be other reasons why this guitar failed but I would think that most of the reason is a week joint at the cross in the x-joint. I neglected to cap the joint on my first build and well, you can see the difference in height between the front of the bridge and the rear of the bridge, also the bridge has pulled off the top.

So now I have to remove the top (want to try something new anyway) and either fix it, or make a new one.

This guitar is only 3 years old, and I noticed the dip at the front of the bridge start about 6 months after stringing it up. Well, I'll never do that again.Rod True38796.7909953704
Author:  Steve Saville [ Mon Mar 20, 2006 11:47 am ]
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Rod,
I believe that it is best to cap the X brace. There are many old guitars out there without it that have not had the bridge pull up/off.
Dont you think the best explanation of why the bridge came off is that the bridge glue joint was not strong enough, either from poor technique, or bad glue? Poor technique could be too much gap, surface contamination, too much pressure, too little pressure, to short clamping time, etc.
Author:  Rod True [ Mon Mar 20, 2006 11:51 am ]
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Of course there is the fact that this is my first and most probably poor construction and application of the bridge. But.... as the dip at the front of the bridge got deeper, the bridge never showed signs of pulling off. This is why I think there is something to do with the torque of the top in pulling the bridge off, along with the possible poor adhision to of the bridge to the top.
Author:  ecklesweb [ Mon Mar 20, 2006 11:54 am ]
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I'm not familiar with "capping" the x brace joint. Can you explain?

Thanks,

Jay
Author:  Rod True [ Mon Mar 20, 2006 12:00 pm ]
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Jay, when you make your x-brace, most tend to place a small "cap" over the joint. Since a picture is worth a thousand words, I'll save the typing.

I stole this picture from Mario's web site, best example I could find.

Author:  Steve Saville [ Mon Mar 20, 2006 12:11 pm ]
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Rod,
Could the dip at the front also be from a poorly placed bridge plate?
Author:  Pwoolson [ Mon Mar 20, 2006 12:56 pm ]
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Rod, have you gotten in with a mirror to examine the joint at the X. I'm not doubting you but I'm having troubles figuring out why that would make the top cave like that. My logic says that the X is misplaced (maybe too far forward so the front of the bridge is not supported at all) or the bridge plate is misplaced so it doesn't support the torque of the bridge. I'm just not understanding why the cap would offer that much support to a torquing bridge.
Author:  Rod True [ Mon Mar 20, 2006 1:11 pm ]
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Those are all very good posibilities and probabilities. Your all most likly correct, I guess that because I knew I didn't add the cap, I am assuming that was most of the problem, but realistically, I'm thinking there is more wrong with my work than right.

The first guitar was built using Cumpiano, but as I remember the top layout was....well sort of "hold up the thumb, close one eye, stick out the tung" sort of layout.

Thanks folks for some better wisdom.Rod True38796.8863310185
Author:  Steve Saville [ Mon Mar 20, 2006 2:27 pm ]
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Rod,
I'm only on my fourth guitar. My first one has been together about one year. I hope it stays together at least 3 years like yours did.
Author:  tippie53 [ Mon Mar 20, 2006 4:11 pm ]
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Usually when I see this it often is from a failed X brace or poorly place plate. I use a half lap joint and cap with a linen wad.
john hall
blues creek guitar
Author:  Kim [ Mon Mar 20, 2006 8:22 pm ]
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[QUOTE=SteveS] Rod,
Dont you think the best explanation of why the bridge came off is that the bridge glue joint was not strong enough, either from poor technique, or bad glue? Poor technique could be too much gap, surface contamination, too much pressure, too little pressure, to short clamping time, etc.[/QUOTE]

Steve, I think Rods point as to why the glue joint failed has to do with the fact that as the bridge rolled, supposedly as a result of brace failure, more direct pulling stress would have been applied to the very rear of the glue joint as apposed to the shear stress shared over the whole joint had the bridge remained flat.

Just my thoughts.

Cheers

Kim
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