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So, I made a MAJOR rookie mistake this past weekend. I was routing out the sound hole in my top, and didn't have the top clamped down. When the router went through on the last pass, the top moved and created an oblong sound hole. To fix it, I just made the sound hole a little bigger... Unfortunately, the soundboard wasn't exactly centered when I started the new size.. So now my sound hole is larger than it was supposed to be, AND off center. I know I can get it re-centered, and enlarge the hole, but what will that do to the sound? It's a Martin OM sized build. The hole was supposed to be 3.875" or 98.425mm. By the time I get it centered, it will probably be more near 4.25". Am I wasting my time by even trying to fix this?

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Jason McGowan
M&S Guitars
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United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns

...

I completely agree. I either need to find a way to fix it, or I'll have to scrap the top. Just not sure if enlarging the sound hole will do to the sound of the guitar.

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Jason McGowan
M&S Guitars
_____________________________
United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns

That's a quite substantial size difference. It may (probably) affect the end of the fretboard and look out of proportion. I would scrap that top and start over. Best to learn from your mistakes and take your time and try to do it right. Save the scrap top for making center seam reinforcements, and/or finishing practice.

I did quite a bit of change to the design of this guitar to begin with. The fret board is actually designed to hang over the sound hole for the last fret anyway. Aesthetically, I'm not sure that it would look bad. I would be more concerned with the distance between the sound hole and rosette only being 3/32"

But will it affect the sound?

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Jason McGowan
M&S Guitars
_____________________________
United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns

No need to scrap the soundboard. Good wood doesn't grow on trees!
An alternative might be to enlarge the soundhole and then bind it in a Black or contrasting wood, thus reducing it's size. Masses of early 19 th century Guitars had the soundhole binding.

Do a rosette that reaches all the way to the soundhole edge.

Cut a plug for the current soundhole, same thickness as the soundboard. Then make a rosette reinforcement patch to go inside the box, as is commonly done. Usually kind of pentagonal shape, to fit between the X brace arms, soundhole braces, and upper transverse brace. Glue the reinfrocement patch over the soundhole area and the plug, thus re-establishing a solid and level outer face. Drill a new center hole, do the rosette, route out the soundhole, and you should be good to go.

Here's an example of a to-the-edge rosette which is just for artistic purpose, not out of necessity

Dennis you never cease to amaze me .... Great recommendation

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Here's another take on a to-the-edge rosette:

There are a few alternatives on the same theme. I've noticed in pictures of old (classical) guitars that the grain pattern in the spruce by the sound hole doesn't always match the grain pattern of the rest of the top, suggesting that the whole inner section of the rosette has been inlaid, including the spruce immediately adjacent to the sound hole. It's not hard to do; the most difficult bit being getting concentric with the existing rings.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I agree with the above recommendations, bind it or make a to-the-edge rosette.
No reason to waste a good top.

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

......

You can enlarge/centre the hole and bind it if you want to reduce the diameter of the soundhole. No big deal.

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Here is a picture of the Sound hole and rosette as it is. It's still a little rough, and needs a little more scraping before finish. I took some measurements, and to get it centered and round, the hole would end up being 4.0825". Is that too far out of spec?

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Jason McGowan
M&S Guitars
_____________________________
United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns

I'm completely willing to do this, especially if the sound of the guitar depends on it. This is my first build, and I really want it to be a decent one. My only concern with this sort of fix is if it will look ok with a dissimilar wood ring inside the existing rosette, mainly because its segmented.

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Jason McGowan
M&S Guitars
_____________________________
United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns

Hey, Jason,
I don't think you should scrap it, either. Now, I'll admit I'm not an expert instrument builder, so I can't comment on the implications for the sound of your guitar. But I'm good at camouflaging my mistakes. I'm also a very good graphic designer, and I believe you can fix the cosmetic flaw very nicely with some patient sanding of the sound hole edge and a black/white/black binding that would complement the borders of your rosette segments. I don't believe anyone but you (and us) would know that you didn't plan it that way. For that matter, even without binding the edge, it doesn't look to me like you are going to open the hole too much more. I say go for a fix! You have absolutely nothing to lose. Don't waste that top and all that nice rosette work.

Patrick

Yeah, that would do the trick.

Here's another one done all the way to the edge, on purpose. My first guitar, btw.

Sheesh! You don't make it easy Jason! On my OM sized guitars I use a 95mm sound hole diameter and pick either 95 or 100Hz for the T(1,1)1. You're going to end up close to 104mm, which would up the T(1,1)1 on one of my guitars by ~ 7.5Hz and, personally, (my tastes) I wouldn't want to be that high. I've measured plenty of 000's at ~106Hz, though, so you're still in the ball park.

I can't think of any easy fixes (or difficult ones, for that matter) for a segmented rosette like that, with the coloured top wood, that will still look designed rather than fixed. Even a complete do-over (i.e. totally new rosette) will look too large on the OD, I think.

There's the stepped sound hole idea that I mention in the book, where the sound hole is stepped down to a smaller diameter using an internal plate, with the right sound hole diameter cut in it. Artfully done, with the "old" sound hole re-centred, it might be your best bet, if you can make a stylistic feature of it.

Best I've got at the moment. Hopefully the people with more imagination than me can help out with some more ideas...

As you don't have a huge investment in this top ATM, putting it aside and starting again isn't too big a deal, using the original top on a later build. Inspiration can be slow to come, but it usually does.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

If you really want to keep the segmented rosette look, I think the best bet is a do over. There isn't really enough space between the segments and the edge of the whole to match aesthetically with the spaces between the segments. If you added an inner binding, again the space would between the binding and the segments wouldn't look right.

If you set it aside and start over, you'll have the benefit of experience. The original soundboard could be set aside for some later project, and the original rosette routed off and replaced with a big mosaic rosette that goes to the edge - or whatever else you can think of.

Here's an alternate perspective. if this is your first guitar, I wouldn't scrap and start over, I'd continue, employing one of the great suggestions provided already. On my first guitar I think I made about 10 errors that required major adaptations and fixes. I think the real goal on the first guitar is to get it completed, and learn as much as you can from the experience. I know that you want it to be as good as it can be, but this won't likely be the final opportunity for improvisation on this guitar....

Enjoy it!

A 4 inch sound hole should still work fine. I believe Mario Proux has built smaller bodied guitars with large soundholes and likes the result.

I find a 4" soundhole is a necessity... most soundhole pickups will not fit with a soundhole smaller than 4"... but since I only have a 4" soundhole pickup... so I make all my steel strings 4".

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

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Hmm, it would be sad to waste that rosette... and 4.0825" isn't that big. Two options I can think of to preserve it:

1. Add soundhole binding, but make it out of white MOP so it connects with the rectangles you have. You'll need an inside reinforcement patch to support the MOP pieces.

2. See how a steel string guitar sounds with a tornavoz That should restrict the airflow in and out through the hole, and hopefully counter some of the effects of the larger diameter. I need to try this on my harp guitar, actually... I think it has a bit too much soundhole, with a main air resonance in the vicinity of 110Hz (A).

Thanks for all the ideas, gentleman. I believe that for this build I need to start another top. This is actually going to be a gift to the person that got me started playing guitar, and hopefully an heirloom. So it has to be as perfect as I can get it. I am, however, going to find a way to salvage this top. It will most likely end up getting the old rosette routed off, and another rosette installed that goes all the way to the edge of the soundboard.




Dennis, I like this idea and may try to incorporate it. I will update this thread with pics of what I end up doing.

Again, thanks a lot everyone. I really appreciate all the input.

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Jason McGowan
M&S Guitars
_____________________________
United States of America, looks like another silent night
As we're sung to sleep by philosophies that save the trees and kill the children....
Casting Crowns