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Thread: Top Plate Carving/Graduation Questions

  1. #1
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    Nov 2014
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    Default Top Plate Carving/Graduation Questions

    Hello Cafe,

    I'm working on an F5 build using the Siminoff instructional book as a rough guide. I'm currently at the point where I've shaped and rough sanded the top side of the top plate and now currently carving the inside of the top plate.

    I'm wondering if anyone can offer advice on knowing when to stop carving the inside of the top plate. I've reached a point where according to my ears I've reached a rather resonant E5 (E above A 440hz) via holding the edge of the plate that will reside under the fretboard extension freely in the air and tapping the center of the top with my knuckle. However this is roughly 25% thicker than the Siminoff graduations (if anyone has that as a reference). I know I'd like to leave some extra thickness to accommodate the finish sanding process once the body is assembled, but looking for recommendations from folks if they use a target thickness, a certain fundamental tone, a certain amount of flex, or some combination of all three, to judge when to stop carving/ graduating the inside of the top plate prior to cutting out the F-holes and installing the tone bars.

    I recognize there might be a wide variety of philosophies regarding this topic, but happy to hear all suggestions and approaches. No bad suggestions!...unless you recommend giving up, I've come too far for that

    Thanks!

  2. #2
    Registered User sunburst's Avatar
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    Nov 2003
    Location
    Kentucky
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    15,863

    Default Re: Top Plate Carving/Graduation Questions

    Quote Originally Posted by Greg Pauza View Post
    ...I recognize there might be a wide variety of philosophies regarding this topic, but happy to hear all suggestions and approaches...
    Indeed there are varied philosophies.
    Truth is, I don't know what the suggested grads are in the newer version of the Siminoff book, but the old version had grads that most of us think are too thick.

    As for me, I carve the arch a little higher or a little lower depending on the perceived stiffness and density of the top wood. lower for harder, stiffer, heavier wood and higher for lighter more limber wood. That variation is within 2 mm of total height from a little over 14mm to about 16mm.
    Once the outside is carved and the arch established, I carve the center to under 5mm (somewhere in the upper 4.XX mm) and the minimum area to 3mm. From there I flex the plate, tap and listen, and thin until I think the stiffness is good. I don't look for any specific notes, I'm just looking for a chorus of partials rather than a strong fundamental. That indicates to me that the plate is in the ball park of the flexibility that I want. I judge more by feel and flex and less by sound. I think I just listen mostly out of habit.
    Once I decide my center thickness I graduate from there to the 3mm near the plate edge.

    Forgot to mention:
    Like many other builders I carve a "spine" in the center of the top. That is, I do not carve under 4mm in the area under the strings from tail block to head block.

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