Sound hole patch

Storo · Dec 4, 2016

I'm new to this forum, and to building ukes. I've built other instruments, but the ukes I'm building will be my first. One each for my 2 grand kids. One will be rosewood w/Engleman spruce top, the other will be toasted Birdseye maple, again w/ an E spruce top.
So I have a question.
I have 2 plans that I am building a uke from. One is from Hana Lima 'ai, in Hawaii, and one is by S Antes.
I know that building techniques vary, but the Hana Lima plan shows a sound hole patch - a piece of 90 thousandths top wood installed on the back side of the sound hole - while the Antes plans do not have this patch. I am not sure which way to go, and am concerned that a patch will have a dampening effect on the sound. What do you guys do? Any recommendations?

BR Ukuleles · Dec 4, 2016

A sound hole patch is not going to dampen the tone.

If you are building with a timber that would easily split, like cedar, spruce or redwood, then you would be best advised to add the patch.

As well, depending on rosette style and depth of inlay, a patch is pretty much a must.

And finally, you want that area around the sound hole stiff. Think of the forces on an instrument, and you will realise that the soundboard with a hole cut in it at the waist is going to weaken it considerably, and the string tension is going to want to fold the instrument in half and swallow itself down the sound hole. Thus, in most plans you will see rather substantial braces on the upper and lower side of the sound hole.....and in some cases the patch.

Rrgramps · Dec 4, 2016

Storo said:
/
am concerned that a patch will have a dampening effect on the sound. What do you guys do? Any recommendations?

I'm told that the lower bout provides most of the excitation, and it is common to have reinforcement around the soundhole for durability.

sequoia · Dec 5, 2016

I used to not reinforce the sound hole and then thought about it and as Allen says, it is obvious there is a structural weakness here in a very important spot. So now I add reinforcement. I have found that it does not seem to influence the sound whatsoever. Since I never did a sound hole reinforcement before I kind of made it up as I went along. I would have preferred to use a round "doughnut" and I think that is probably the best way to go structurally, but it is very wasteful of wood and my scraps are just not large enough so I just put in two angled braces on either side with the grain lines perpendicular to the grain lines on the top. Very fragile pieces that gain strength from the glue. A cross-ply. Also just pulled a number for thickness out of the air and make them the same thickness as the top or a little thinner. Say around 70 mil or so. Don't think this is critical. Below a pic of my sound hole braces on a Sitka spruce top. Never seen this arrangement in a plan, but it just seems to make sense to me. Braces firmly butted to the upper and lower transverse braces. Oh and I use the same wood as the top on the theory that they will expand and contract in concert.

Timbuck · Dec 5, 2016

I don't use a patch on soprano's ,the rosette and two cross braces are there to prevent splitting and add strength..but on one build recently I cut the rosette channel a bit too deep almost breaking through I didnt want to fit a chunky patch so I made one out of brown paper .. it did the job fine and can't be seen or felt wth the finger.

Rrgramps · Dec 5, 2016

Reinforcement helps for those who carry by inserting fingers into the sound hole, with thumb on the waist.

sequoia · Dec 6, 2016

Yeah, probably not needed on a soprano. This is a tenor sized uke. Not sure even necessary here, but I figure it doesn't hurt and might even possibly help. Shrug...

Michael N. · Dec 6, 2016

I've never seen one on a romantic guitar and countless thousands of those were made. I can't recall problems with the soundhole area either, which might tell you something given that most of them are now nearly 200 years young. Plenty of other problems - cracks in backs, sides, soundboards, neck angle issues but nothing I can recall specifically to do with the lack of a soundhole patch. Having said all that a patch isn't likely to do much harm either. Take your pick.

Rrgramps · Dec 6, 2016

Checked the archives, and found a good one from Pete Howlett...
http://forum.ukuleleunderground.com/showthread.php?56144-Bracing-patterns

It's similar to Sequoia's, and saves having to line up another hole, if you forget to glue it in until after the soundhole is already cut. I'm going to use that, but as said, it's ok to dispense with it.

StewMac's tenor kit doesn't have a sound hole patch; apparently they don't think it needs one. Worst case, the hole in Willie Nelson's guitar, although worn a different place, could be a proud emblem for some astounding ukulelian. Heheh.

Maybe a new/old relic ukulele could be on the luthier's list to sell at a premium cost. Sell it for more, and use up the rejected tops. Hmmm. I do have an über thin cedar top that I set aside for patches.

pahu · Dec 10, 2016

sequoia said:
I used to not reinforce the sound hole and then thought about it and as Allen says, it is obvious there is a structural weakness here in a very important spot. So now I add reinforcement. I have found that it does not seem to influence the sound whatsoever. Since I never did a sound hole reinforcement before I kind of made it up as I went along. I would have preferred to use a round "doughnut" and I think that is probably the best way to go structurally, but it is very wasteful of wood and my scraps are just not large enough so I just put in two angled braces on either side with the grain lines perpendicular to the grain lines on the top. Very fragile pieces that gain strength from the glue. A cross-ply. Also just pulled a number for thickness out of the air and make them the same thickness as the top or a little thinner. Say around 70 mil or so. Don't think this is critical. Below a pic of my sound hole braces on a Sitka spruce top. Never seen this arrangement in a plan, but it just seems to make sense to me. Braces firmly butted to the upper and lower transverse braces. Oh and I use the same wood as the top on the theory that they will expand and contract in concert.

View attachment 96111

Interesting reinforcement, and light enough to not increase overall weight.
What's your explanation of the 3-piece head-block?

pahu · Dec 11, 2016

sequoia said:
I used to not reinforce the sound hole and then thought about it and as Allen says, it is obvious there is a structural weakness here in a very important spot. So now I add reinforcement. I have found that it does not seem to influence the sound whatsoever. Since I never did a sound hole reinforcement before I kind of made it up as I went along. I would have preferred to use a round "doughnut" and I think that is probably the best way to go structurally, but it is very wasteful of wood and my scraps are just not large enough so I just put in two angled braces on either side with the grain lines perpendicular to the grain lines on the top. Very fragile pieces that gain strength from the glue. A cross-ply. Also just pulled a number for thickness out of the air and make them the same thickness as the top or a little thinner. Say around 70 mil or so. Don't think this is critical. Below a pic of my sound hole braces on a Sitka spruce top. Never seen this arrangement in a plan, but it just seems to make sense to me. Braces firmly butted to the upper and lower transverse braces. Oh and I use the same wood as the top on the theory that they will expand and contract in concert.

View attachment 96111

After you piqued my interest, I looked inside some of my vintage Ukes. This 1960's(?) Martin Tenor has a brace like yours.
Unknown type of wood, but I'm guessing it's spruce like the bracing

sequoia · Dec 11, 2016

pahu said:
What's your explanation of the 3-piece head-block?

Ah yes, the overbuilt neck block. The reason is that that is how I saw it built and that is the way they did it so that is the way I do it. Sometimes we do things just because that is the way we do things. This can be dumb I agree. I guess if I had to rationalize it I would say: This is an acoustically dead area (oh really?) so that I get some extra support for the downward force of the fretboard on the top and it helps anchor the neck to the body... Sorry for the lame answer. I'm not an ukulele designer so I just do what other people do. Truth is, it works and I'm afraid not to do it that way because I don't understand it.

Sound hole patch

Storo

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BR Ukuleles

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Rrgramps

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sequoia

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Timbuck

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