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  #1  
Old 02-05-2015, 05:01 PM
PhilQ PhilQ is offline
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Default Bracing "philosophy" for small guitars

Hey guys,

As I keep building guitars and reflecting on things, a lot of questions come up, some of which I wish I had experienced builders to ask directly.

Thankfully this forum exists!

So far I've built my guitars with the popsicle brace, but I've read quite a bit about some people removing them in their guitars (or at least having luthiers do it for them). I understand the presumed benefit of doing this, as well as the added risk. But I am wondering: if building a smaller-bodied guitar (a 00 for instance), does the size of the instrument make having a popsicle brace less important structurally? I guess there's less surface area of the top that isn't braced in that area with a smaller guitar, so does that make a difference either way?

How about bracing? Do you tend to shave the bracing a bit more on a small-bodied guitar?

Lastly, how about the presence or absence of a center strip over the joint of the back? I know quite a few people don't use one when not including a backstrip. But does the size of the guitar make a difference for you as to whether or not to use one?

Thanks so much!

Phil
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  #2  
Old 02-05-2015, 06:15 PM
Twilo123 Twilo123 is offline
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this will probably give you more questions than answers but there is a section on bracing here http://www.esomogyi.com/principles.html
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  #3  
Old 02-05-2015, 06:28 PM
Tom West Tom West is offline
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Quote:
Originally Posted by PhilQ View Post
If building a smaller-bodied guitar (a 00 for instance), does the size of the instrument make having a popsicle brace less important structurally?

How about bracing? Do you tend to shave the bracing a bit more on a small-bodied guitar?



Phil
The popsicle is less about structural strength then it is about differential shrinkage between the top and fingerboard resulting in top cracks in this area. So that says to me one should have this insurance and perhaps prevent a disaster such as the neck trying to push its way into the soundhole. Once cracks form, the brace becomes important for structure.
My experience with bracing is that the size of guitar and bracing are not proportional. A guitar that is an 1/8 smaller needs bracing a bit less then 1/8 smaller. Others with more experience in size variations may be able to add more insight.
Tom
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Old 02-06-2015, 02:23 PM
PhilQ PhilQ is offline
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Thanks M. West. How about the center strip on the back?
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Old 02-06-2015, 03:06 PM
Tom West Tom West is offline
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I have never built without a reinforcement strip and don't think I could be convinced not to. Don't think it would have much if any effect on tone but provides some insurance for the joint. Again just my opinion.
Tom
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Old 02-06-2015, 03:59 PM
Ned Milburn Ned Milburn is offline
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Quote:
Originally Posted by PhilQ View Post
Thanks M. West. How about the center strip on the back?
As long as your center strip isn't ridiculously giant or heavy, it shouldn't have a great impact on tone either way.
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Old 02-06-2015, 04:11 PM
John Arnold John Arnold is offline
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I think including the center back reinforcement should be a function of the integrity of the joint. With that in mind, softer woods like mahogany glue to themselves better than a dense oily wood like rosewood. That would lead to the practice of gluing a simple line of mahogany or other softer wood between the halves of a rosewood back.
IMHO, a single line in between the halves does not require a reinforcing strip, while a marquetry strip (which is not as strong) normally does.

You can glue a small spruce patch in place of the popsicle. The main reason for either one is to prevent top cracks next to the fingerboard. Unless the guitar has a soundhole that is smaller than the width of the fingerboard, the need for reinforcement is the same, regardless of the size of the guitar.
My small spruce patch is about 1/8" thick, or a bit thicker. It is quartersawn. The grain is parallel with the grain in the top. It is sized to fit tightly between the neck block and the UTB (very important to prevent neck block shift). The width is the same as the neck block where it contacts it, flaring to the width of the soundhole where it contacts the UTB. That forms the trapezoidal shape. The angled edges prevent a stress riser which would occur when the edges of the patch are parallel with the grain in the top.

Quote:
How about bracing? Do you tend to shave the bracing a bit more on a small-bodied guitar?
Definitely. Not only shaved, but the initial size of the bracing is smaller. Martin is a good starting point for bracing design.
The thickness of the top, back, and sides should be a bit thinner on smaller guitars, too.
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Old 02-06-2015, 04:22 PM
Tygrys Tygrys is offline
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I founded this in the net.

http://www.bryankimsey.com/popsicle/
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Old 02-06-2015, 06:27 PM
PhilQ PhilQ is offline
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Quote:
Originally Posted by John Arnold View Post
I think including the center back reinforcement should be a function of the integrity of the joint. With that in mind, softer woods like mahogany glue to themselves better than a dense oily wood like rosewood. That would lead to the practice of gluing a simple line of mahogany or other softer wood between the halves of a rosewood back.
IMHO, a single line in between the halves does not require a reinforcing strip, while a marquetry strip (which is not as strong) normally does.
Thanks for the amazing info, as usual, John. If I understand what you are saying correctly, you're talking about having a line of mahogany in lieu of a marquetry strip, correct? Perhaps my use of the terminology in the original question was wrong, but I was wondering more how important the reinforcement strip itself was when you don't use a marquetry strip or anything else between the plates.

I know some makers don't use a reinforcement strip at all, and I would be curious to find out whether their instruments are more prone to center cracks on the back. A lot of the Larrivées I've seen were like that. The company has been in business for many years, so you'd think there'd be enough instruments on the market to give a good sample size...
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Old 02-06-2015, 07:26 PM
John Arnold John Arnold is offline
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Quote:
If I understand what you are saying correctly, you're talking about having a line of mahogany in lieu of a marquetry strip, correct? Perhaps my use of the terminology in the original question was wrong, but I was wondering more how important the reinforcement strip itself was when you don't use a marquetry strip or anything else between the plates.
It's fine. I am just saying that gluing two pieces of rosewood together requires more care than gluing mahogany (or maple, walnut, etc.) together. A strip of softer wood in between the halves of a rosewood back helps somewhat.
FYI, it is a good idea to surface rosewood immediately before gluing. With the other woods I mentioned, it is not an issue.
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  #11  
Old 02-06-2015, 07:58 PM
printer2 printer2 is offline
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Quote:
Originally Posted by John Arnold View Post
My small spruce patch is about 1/8" thick, or a bit thicker. It is quartersawn. The grain is parallel with the grain in the top. It is sized to fit tightly between the neck block and the UTB (very important to prevent neck block shift). The width is the same as the neck block where it contacts it, flaring to the width of the soundhole where it contacts the UTB. That forms the trapezoidal shape. The angled edges prevent a stress riser which would occur when the edges of the patch are parallel with the grain in the top.
I am taking this nugget of information with me. Next guitar will get one.
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  #12  
Old 02-07-2015, 02:34 AM
Halcyon/Tinker Halcyon/Tinker is offline
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Personally, I really can't see the Popsicle brace influencing tone. I don't believe there's much tone creation action happening in the top in that part of the guitar. I know some folk swear by it, but...

I don't think the size of the instrument is important in that regard. Though, in the case of a 12 fret 00, there is quite a bit more space between the UTB and the neck block.

As for the bracing, yes, there needs to be changes, mostly in the height. But I also make my tops thinner on smaller boxes.

For me, the size of the box has nothing to do with the back reinforcement. If it has no external decorative centre strip, then I feel, personally, that it doesn't need an internal reinforcement.

Mind you, that comes from 18 years at the Larrivee plant watching (and helping) 140,000 guitars come through without them. Repair people might feel differently.

John Arnold,

I'm surprised that your patch is parallel with the top. I had thought the patch was meant to be opposing the top grain. Having it wedge between the UTB and block tightly makes sense.
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  #13  
Old 02-07-2015, 04:48 AM
John Arnold John Arnold is offline
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Quote:
I had thought the patch was meant to be opposing the top grain.
A cross-grain patch has two disadvantages. In the case of a Martin, it is 1" wide. Gross-grain construction that is that wide will tend to loosen over time, due to differential shrinkage. That is why popsicle braces often don't prevent the top crack beside the fingerboard. The second disadvantage is that it will not guard against neck block shift, since wood is not nearly as stiff or as stable across the grain. In other words, any shrinkage will cause a gap to form between the patch and the block or the UTB, defeating the purpose.
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  #14  
Old 02-07-2015, 01:27 PM
Howard Klepper Howard Klepper is offline
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Quote:
Originally Posted by John Arnold View Post
A cross-grain patch has two disadvantages. In the case of a Martin, it is 1" wide. Gross-grain construction that is that wide will tend to loosen over time, due to differential shrinkage. That is why popsicle braces often don't prevent the top crack beside the fingerboard. The second disadvantage is that it will not guard against neck block shift, since wood is not nearly as stiff or as stable across the grain. In other words, any shrinkage will cause a gap to form between the patch and the block or the UTB, defeating the purpose.
But will a patch that has grain parallel to that of the top prevent cracks from differential shrinkage of the fretboard?
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  #15  
Old 02-07-2015, 03:08 PM
PhilQ PhilQ is offline
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Quote:
Originally Posted by Howard Klepper View Post
But will a patch that has grain parallel to that of the top prevent cracks from differential shrinkage of the fretboard?
Was wondering this as well.
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