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Rick Turner knows a little about soundboard distortion and guitar restoration

http://www.acguitar.com/Gear/advice/neckresets.shtml

Ray, from your first post I assumed that you really wanted to know the radius of a guitar - maybe to try to duplicate it or something. Builders are always trying to measure things on existing guitars (try duplicating a neck profile some time). I only mentioned Autocad because many people do have it and it is a quick and dirty way to do these calcs (if you wanted to give me the measurements I could run it thru mine).

The others have given you some really good specifications and "seat of the pants" evaluations to tell if you have a problem. I will say that my old D12-28 was developing a noticable bulge in the lower bout (and my wife says I am too, but thats a different subject) - I farted around with a bridge doctor which didn't really fix anything, and ended up getting the neck reset and bridge reglued (which did). Lots of times a good experienced repair person is better than any measurement or calculation

Last thing that I'll add, on an older guitar the top will probably be pulling up slightly, but also you'll probably have some rotation of the neck block. There are good seat of the pants indicators of this, and if so, having the neck reset will help correct all of the geometry.

Freeman wrote:Ray, from your first post I assumed that you really wanted to know the radius of a guitar - maybe to try to duplicate it or something. Builders are always trying to measure things on existing guitars (try duplicating a neck profile some time). I only mentioned Autocad because many people do have it and it is a quick and dirty way to do these calcs (if you wanted to give me the measurements I could run it thru mine).

The others have given you some really good specifications and "seat of the pants" evaluations to tell if you have a problem. I will say that my old D12-28 was developing a noticable bulge in the lower bout (and my wife says I am too, but thats a different subject) - I farted around with a bridge doctor which didn't really fix anything, and ended up getting the neck reset and bridge reglued (which did). Lots of times a good experienced repair person is better than any measurement or calculation

Last thing that I'll add, on an older guitar the top will probably be pulling up slightly, but also you'll probably have some rotation of the neck block. There are good seat of the pants indicators of this, and if so, having the neck reset will help correct all of the geometry.

Thanks for the info. Actually I was trying to help someone else and I succeeded in convincing them there actually was a problem and getting them to take it to a Martin repair shop berfore they lost it.. that was my goal, and I was sucessful :)

Cool. Humidity has a big effect on the top too, but usually what you see is a dry guitar with a shrunken top and cracks, not a belly.

edit to add, while lurking around at UMGF I saw this. Look at post 29

http://theunofficialmartinguitarforum.y ... pic/103395

I know little about the issue but I feel certain there's is a bridge plate failure on the way..even though you can't see physical damage or loose braces or gaps...I think he
will come away happy that his old Martin was saved with a new plate and a neck set. Sometimes it's wise to go see the Doctor before there are obvious symptoms :)
Thanks again.

Ray

rgogo65 wrote:

Freeman wrote:..... I will say that my old D12-28 was developing a noticable bulge in the lower bout (and my wife says I am too, but thats a different subject) .....

I've visited with several luthiers about a similar problem I have with this, and none of them seem to have an GOOD suggestions. (They all want to talk about diets and exercise and crap like that.)