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thickness for soundhole patch (Read 1830 times)
sweetgum
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thickness for soundhole patch
Nov 28th, 2008 at 4:32pm
 
hi everyone,

this is my first posting, i've read most all of the posts and have learned a lot from you all. thanks!

so my question.  what are the thickness dimensions for the sound hole patch and the centerline grafts?

thanks,
jason





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unkabob
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Re: thickness for soundhole patch
Reply #1 - Nov 28th, 2008 at 5:52pm
 
Jason:
I have used veneer for graft (20 thou) but it seemed too thin.

Sound-hole and bridge patch I make from left over soundboard material (70 thou) but it seems a bit thick to me.

I am guessing that 40 to 50 thou is my choice but be sure to apply it cross-grain like plywood.

This is strictly my opinion.

Bob
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Matt Blacka
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Re: thickness for soundhole patch
Reply #2 - Dec 2nd, 2008 at 11:32am
 
Hi Jason,

For hardwood soundboards (blackwood, koa, etc) I'd go for patches that are around 1.6 mm (0.06") and for softwood soundboards (spruce, cedar, etc) it's best to go a little thicker and more like 1.8 mm (0.07").

For centre grafts, I usually start with a thickness of about 1.8 mm and then sand the graft using a piece of sandpaper stuck into a section of PVC pipe lengthways. This gives the top of the graft a nice radius profile that makes it a little thinner towards the edges where less strength is required. I think the Hana Lima 'Ia manual just says to put a bevel on the edge of the graft for the finishing touch, but I prefer the look of the radiused top. This is just personal preference.

As Bob pointed out, the most important thing is to remember that the grafts and patches have to go cross-grain. If not, they will not provide any additional support to resist splitting of your soundboard along the grain, or to support the centreline join between back board plates.

There have been lots of previous posts about the thickness of patches and grafts on this site, and about a year ago I went through and made myself a copy of all the opinions. The numbers I have listed here for thickness (and use for my ukes) are pretty much the conclusion/summary of all the previous opinions.

Matt
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MAKAIO Ukuleles, Australia www.makaioukuleles.blogspot.com
 
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sweetgum
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Re: thickness for soundhole patch
Reply #3 - Dec 22nd, 2008 at 1:55pm
 
thanks for the help.  i like the pvc radius sanding block idea.  i ran some pieces through a router and put a 11 degree bevel on the center graft to provide the taper, but i think that process could be simplified with the pvc. 

great!
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