All so calledn"flat top" guitars have a radiused top. This is done for strength reasons. The radius does vary from builder to builder, and can vary from 12 to 30 foot raidus. Guitar backs are also radiused, and the radius for the back is usually larger for the back than the top. A guitar without a radius is either a bad design, or it is an indication of a guitar lacking humidity. On a well designed guitar, some bridge belly is to be expected; if the belly is not there, it indicates an overly thick top, overbracing, or again, lack of humidity.
No argument.
But we're not talking about guitars with a radius built into the design -- or at least that's not where this discussion began.
We were talking about an older guitar (1964) that may have developed bellying beyond the tolerances built into the design, and if so, such a guitar, like this F112, will likely need to be repaired, adjusted -- whatever word you want to use.
Dana acknowldeges in his article that guitars with lighter builds (and Guilds from this era were built light) will sound great for many years, but will need periodic adjustments and will eventually fail. (One boutique luthier makes his guitars with the assumpton that they will not last for much more than 20 years, but will sound amazing during that time.)
Norman Blake, in his "no belly / no tone" comment was referring to his vintage Martin six-string, which has a radiused top built into the design. He wasn't talking about a guitar that had developed a bellying *problem*.
What we often see on older Guilds, and especially on 12-strings, is bellying of the top beyond what is tolerable, which often leads to a depression around the soundhole area and, due to the way Guild designed their bridges, bridge lift. This will affect playability and intonation.
The advice given to "rbrcbr," who was concerned about bellying, was that he needn't worry about it or that any bellying was a good thing.
I'm all for enabling, but I don't consider that good advice! Without actually seeing the guitar it's impossible to know how pronounced, or not, the problem may be.
My advice, rather, is to take those "don't worry about it" / "bellying is good" comments with a grain of salt, and to consider the possibility that if you buy the guitar, you may discover that it needs repair or adjustment.
Considering the age of the guitar, and the fact that it's a 12-string and will have been under 220+ pounds of string tension much of its life, it would be unusual it it didn't need some work.
