Re: Contour placement, recurve and the whole package
Greg have you visited Mandozine's builder questions and answers section? Michael Heiden addresses this subject of recurve placement and top/back graduation and his methods.
Q7
Q - On plate graduations, is there a minimum thickness in the recurve area below which you will not go? (Both for tops and backs). On topwoods, I realize it depends on species and hardness, but is there a maximum thickness in the recurve, above which performance of the plate suffers? And how far in from the rim is the thinnest point of your recurve?
A - I have always like the tone of instruments that have enough wood to sustain and develop sweeter and sweeter tones as the years go by. I don't know if there is a rule one can adhere to, only experience with the different woods. Obviously too much wood in the recurve area will not allow the woof that is so inherently desirable in the mandolin but too thin will not allow the vibrations to get to the edge where all the power is sprung from.
As a ball park figure I would say that for a top of Adirondack spruce the recurve should be no thinner than .060" and no thicker than .22 in the middle. I aim for around .075 and .190.
I have never aimed for immediate volume with a thin top rather leaving enough wood for the instrument to develop tone.
My recurve is thinnest .675" from the rim. One factor that affects this is how wide the kerfing or linings are. I round my kerfing from the side up to the plate leaving only about .125 of surface plus the side for the plate to glue to.
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