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I think I have carved the x-braces too low in the region around the bridge patch.
Is it advisable to glue another piece on top to increase height?

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We are all in the gutter but some of us are looking at guitars.

How low have you carved them? I have gone below .25" at the trough of the scallop...just barely, but I have done it. It was a dread if that helps. You could add a brace behind the bridge plate that connects the two X legs. I did that on an OM I had concerns about. Check Mario Proulx's website for info:
http://www.proulxguitars.com/buildup/build6.htm

Looking at how deeply Mario scallops his braces...they are barely higher than the bridge plate. Granted, he adds carbon fiber to his braces, but thems be some deep scallops!

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http://www.CostaGuitars.com
PMoMC

Hi Joe,
You might want to google Fred Carlson of drednautilius fame. He doesn't seem to worry about gluing up braces from multiple laminations of wood.

Since the top isn't on the guitar
take pictures and post . It sounds like you may have gotten overzealous on the scalloping. I won't scallop much in that area . In a nut shell you can pop the braces off and redo. It is easier now than after the guitar is done. .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

John beat me to it. If it's really bad, it's always easy to carve off, clean, and start again.

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

But we don't know how thick or how stiff his tops are.

I too would strip off the braces and begin again. Then you will end up with what you started out to do.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Thanks for the replies.
I carved the brace down to about 5mm in an over-enthusiastic scoop. I thought it would have to come off but before that I thought I'd try a radical solution. So I glued on a bridge between the x-brace intersection and the peak. It certainly stiffened her up again. I want to make it clear that I don't really intend to leave it like this. I'll probably remove the braces and but in other ones. This is only my second guitar (my first was a disaster) so I want to follow the plans fairly closely.
But Im hoping to open this to discussion. What if I left it like this? Would it work?



sorry for poor photo.

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We are all in the gutter but some of us are looking at guitars.

slightly better photo

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We are all in the gutter but some of us are looking at guitars.

How thick is the top?


Posted using something.

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http://www.CostaGuitars.com
PMoMC

The top is about 2.9mm (0.114173228 inches) thick. Although is not even thickness all over.

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We are all in the gutter but some of us are looking at guitars.

5mm (3/16ths inch+) may be tall enough for a relatively stiff top. So depending on the size of the guitar you are building and the sound you are looking for, the braces may be fine as is.

I'm building an OM. When I flexed across the x-braces it felt really floppy. I cut out the notches so the top sat on the sides and appled pressure at the bridge- there was a lot of give. I don't really know what I'm doing but it felt like the top would collapse too much under the weight of the strings.
Anyway, now I've glued on the bridge across the x-brace It's either go with that or install new braces.
I'd still like to hear some comments on the bridge across the brace.

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We are all in the gutter but some of us are looking at guitars.

String it with light gauge strings. It will be fine. I built a dread with a top at .095" and the braces were similar to yours and its fine. Obviously, the stiffness of a particular piece of wood matters, but you should be fine.


Posted using something.

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http://www.CostaGuitars.com
PMoMC

I love your solution with the over brace, but I like different and creative. I also don't see any reason why an over brace like you've designed wouldn't stiffen the area in question (which it did according to your observations) and save some weight/mass at the guitar top in those areas. I'd go for it with the over brace just to see what you get, I can't see a downside, but as usual better to wait for those who would know more about such things.

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Thank You and Best To All

Thanks, Larry. I'm tempted to leave it too.



Yes, please!



Tony, I love your optimism!

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We are all in the gutter but some of us are looking at guitars.

I think you'll be fine, as long as the top isn't overly weak. This one -will- belly, so keep that in mind when setting the neck; allow some room for cutting-down the saddle in the following years. In other words, over-set the neck a bit, maybe as much as 1/16" over the bridge, such that everything should resolve itself to the correct geometry in a few years(instead of starting-out correct, and needing correction(neck reset) in a few years).

Not sure of the little spanning braces, though, because of the way the bridge torques the top at that point, so if you leave them in place(I say why not!), check-in on them, visually, once in a while. If they begin to show signs of buckling, just reach-in with some side cutters and cut 'em out...

Oh, and if you had your heart set on running mediums, try them; if the top is very stiff(and with little experience, you really can't tell us right now if this is a really stiff one or not, right?), you'll be fine.

I like it. "Bridge over troubled scallop" or "Bridge saves scallop from torque monster"

But really, I think I've gone this low and it was ok. But if I flexed it and it felt like it was piviting at one point rather than a gradual flex, I would be sceptical.

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Pat

Really appreciate your reply, Grumpy, but:

I need to understand this. If the bridge bellies doesn't that mean the saddle will go down? And if so, if the neck was set higher, wouldn't that give a bigger action?


Good idea!


Not sure what you mean by running mediums...



Thanks, Pat. It felt like the top was pivoting. The bridge has stopped this. In fact it feels good (I think).
This is the problem with learning without a teacher and something even this forum can't solve. Things like, how stiff is a top are impossible to judge without comparison and someone telling you "this feels a good stiffness". The same is true with voicing the top- despite reading about it, I haven't a clue what I'm doing. I need someone to show me. I guess some of these things are covered in Trevor's book with formula but I ain't got that book yet...

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We are all in the gutter but some of us are looking at guitars.

If the bridge bellies doesn't that mean the saddle will go down?

Nope, with a true belly, the top rises...

Not sure what you mean by running mediums...

Medium gauge(.013" to .056") strings.

I'm a really positive guy. Plus, unless you had a really floppy sound board to begin with, I am certain you will be just fine. Especially with your "Bridge over troubled scallop" solution.

When Grumpy says to over set the neck, he is talking about tipping it back more than you would normally. Without string tension and without the top being pulled up, over setting the neck will result in a straight edge placed on the neck and extended over the bridge, being higher over the bridge than you would normally want it. However, when you string up the guitar, the tension will pull the bridge up and give you the action you want. Leaving the saddle high lets you adjust the action as the top rises a bit more over time. If you do not over set the neck, you will end up with very high action. I had to make the same compensation on a the dread I mentioned in the quote above. With only the two E strings on while I was doing the set up, they buzzed all the way up the neck. Once I had all of the strings on, the action was perfect. Time will tell if I over set the neck enough, but a year later and it is still fine.

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http://www.CostaGuitars.com
PMoMC