Bad Fret Buzz On Higher Frets. Please Help!

[202dy]

Some folks have difficulty visualizing the geometry when looking at a problem like this. It seems on the surface that a shim would cause a lift at the butt end of the fretboard causing the notes to choke out on the upper end. But if the cause of the problem is a kink (a.k.a. ski jump) at the end of the board, shim or no shim will not have any effect. Here's why.

In the crude diagram below, I have exaggerated the problem for clarity. In the upper drawing we have the situation where their is a shim at the base of the neck, angling the neck to the body. The blue line represents the string fretted at the 15th fret, and you can see that it is now touching the last fret on the neck. If we remove the shim and adjust the bridge to give the same string height at the 12th fret, the string still frets out at the last fret (blue line again).

View attachment 2827703

Even if the neck had no kink, shimming or not shimming would have no effect on the string clearances if the bridge is adjusted to give the same height at the 12th fret. The body is irrelevant when it comes to notes fretting out, as is the neck-to-body angle. The only effect the shim has on the geometry is to require the bridge to be adjusted to provide the same string height, usually measured at the 12th fret.

Hope this helps.

Your "crude diagram" is excellent.

It would be helpful for most folks if there were another "crude diagram" depicting a neck without a ski jump for comparisons' sake.

 

[prokfrog]

Some folks have difficulty visualizing the geometry when looking at a problem like this. It seems on the surface that a shim would cause a lift at the butt end of the fretboard causing the notes to choke out on the upper end. But if the cause of the problem is a kink (a.k.a. ski jump) at the end of the board, shim or no shim will not have any effect. Here's why.

In the crude diagram below, I have exaggerated the problem for clarity. In the upper drawing we have the situation where their is a shim at the base of the neck, angling the neck to the body. The blue line represents the string fretted at the 15th fret, and you can see that it is now touching the last fret on the neck. If we remove the shim and adjust the bridge to give the same string height at the 12th fret, the string still frets out at the last fret (blue line again).

View attachment 2827703

Even if the neck had no kink, shimming or not shimming would have no effect on the string clearances if the bridge is adjusted to give the same height at the 12th fret. The body is irrelevant when it comes to notes fretting out, as is the neck-to-body angle. The only effect the shim has on the geometry is to require the bridge to be adjusted to provide the same string height, usually measured at the 12th fret.

Hope this helps.

Great info. Thanks. So are the terms "neck kink" and "ski-jump" interchangeable? I've always heard of ski-jump referred to as the condition created by a shimmed neck where the neck area inside the pocket settles into the "gap" created by the shim. So then for that matter, even a neck through could theoretically develop a 12th fret kink?

 

[Turnaround]

Your "crude diagram" is excellent.

It would be helpful for most folks if there were another "crude diagram" depicting a neck without a ski jump for comparisons' sake.

OK. Here's the same thing without a kink. Top = shimmed, lower = no shim:

 

[202dy]

That's pretty.

Anyone who looks at both diagrams should be able to understand why trying to fix a ski jump through a set up doesn't work.

 

[Turnaround]

Great info. Thanks. So are the terms "neck kink" and "ski-jump" interchangeable? I've always heard of ski-jump referred to as the condition created by a shimmed neck where the neck area inside the pocket settles into the "gap" created by the shim. So then for that matter, even a neck through could theoretically develop a 12th fret kink?

Yes - bolt-on, neck through - both can develop a ski jump, kink or whatever you want to call it. And no, ski jumps are not caused by a shim. Check out the entire story here:

Getting the Facts about Ski Jumps