Quote:
Originally Posted by Craig Regan
I am building from a Peter Chandler plan. His graduation pattern for the top plate has a thick 8 mm center "spine" running top to bottom. Here are some ideas for different patterns, for thinning the top.
The first is a simple peanut type shape. Starts off thick in the middle and gradually thins at the edges. Seems simple and straight forward.
The second is based on a cello pattern. Ovals in the center, thinned out in the upper and lower bouts or "lungs" as they are sometimes referred to in this sort of pattern. Good pattern for cellos and violins but unsure with double basses.
What is the accepted "normal" patterns used by manufacturers past and present?
Would the tea leaf and audio oscillator set up help out in this situation?
The further I go on this project - the less I know.
If anyone wants to chime in on graduating top plates, the forum is open.
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Not having ever made a Bass I have been inside quite a few of them and outside as well. My worry on the second pattern for Cello on the right is Bass bar sinkage. I think the one on the left (Peanut?) is the more common and trusted way to go.
The 6mm all across the bottom might be ok but why take the chance. Also, I have heard that Panormo made some Bass at 6mm all over without any graduations. Each piece of wood is different and has different strengths and weaknesses even within the same piece of wood end to end. What you can do is try something more on the heavier side like circles in the center 8-10mm and gradually thinning and turning to oval graduations as you move outwards. After the Bass is done you can always go back and re-graduate if you like. I have seen some Basses with a slight built up platform under the Bass Bar, the entire length (and soundpost area too). This is done to add strength to that area. If re-graduated with the 'Bar in place, it would be ok to work around it leaving the platform. My Gilkes as made that way and I know of an old attributed Maggini that was as well. Someone re-graduated that Maggini thinking it was wrongly made and guess what? The Top sunk under the Bar afterwards, so the former owner told me some 3 1/2 decades ago. Things like that you don't forget!