Downward Bridge Pressure Archtop Guitar

[Paul Said]

Hi all, I recently completed my first neck reset thanks to some help by individual on this forum. I have just strung up the guitar with a old set of light gauge strings and have discovered that the top of the guitar is slightly depressed at the bridge. I've searched the web to get an understanding if this is "normal" on an archtop guitar but could not really find anything definitive.

When I reset the neck I had 23mm at the bridge when a straight edge was placed on the fretboard with no load on the neck. The top has sunk approximately 3 to 4mm. Is this common.

The guitar is a vintage ibanez archtop and the top is X braced. All bracing is secure.

Regards

Paul.

[Ned Knepp]

My personal experience is that any archtop instrument that is at all responsive will have some deflection/depression under the bridge when the strings are brought to pitch. How much seems to depend on the instrument but 3-4 mm doesn't sound like too much to me on a guitar.  

When I work with archtop instruments, the question I usually ask is; Is the bridge adjustment ( height) reasonable for the instrument. I don't want the saddle to be completely down but I really don't want it to be more than a few turns of the adjustment wheels above the bridge either. In other words, I want to have room to adjust the bridge either up or down if environmental conditions call for a slight adjustment without maxing things out either way.

My limited experience means that I really don't have anything like exact measurements for this.( If it's even possible to have exact measurements for this at all.)  Every archtop instrument I've worked on seems to have it's own range. I'm sure that there are other here with more experience that could give you better advice but I think it comes down to making adjustments that are appropriate for the individual instrument.

A couple of suggestions that I have for you as you got into the "setup" phase of your reset are;

1.) use a new set of strings for the setup and make sure they are the brand and gauge you are committed to using on the instrument.

2.) Leave the instrument strung for a few days with tension before you do the final setup. My limited experience with resets has been that the instrument may need a bit of time to settle in before final adjustment.  

[Matt Dreher]

I second what Ned has to say. I have found on neck resets or bridge replacements on any hollow bodied guitar, there is going to be some deflection or sinking of the top under string tension and it is normal. I have learned after making mistakes that i needed to measure how much the top sinks before i start the repair under the pressure of the exact string gauge that will be used on the guitar after the repair is complete. I measure this "inconsistency" and record it so as i am measuring progress during the repair i can accommodate for it.  

[Paul Said]

Thanks Matt & Ned. Yes, a valuable lesson when resetting a neck. I didn't take into account the deflection to the top under string tension but I am fortunate that there is enough adjustment on the bridge to give me the string clearance I desire. Bridge height is currently at 29mm.

Regards

Paul.