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-   -   Gluing Top Braces (https://www.acousticguitarforum.com/forums/showthread.php?t=604284)

Victory Pete 01-18-2021 11:53 AM

Gluing Top Braces
 
Do you glue top braces to a flat or radius surface when using a Go Bar deck?

charles Tauber 01-18-2021 12:14 PM

That depends on whether you want a flat top or an arched top. If flat, glue braces on a flat surface: if arched, glue braces on an arched surface. That's regardless of how you chose to clamp them while the glue dries.

Seems pretty self-evident. Am I misunderstanding your question?

Victory Pete 01-18-2021 01:10 PM

Quote:

Originally Posted by charles Tauber (Post 6607904)
That depends on whether you want a flat top or an arched top. If flat, glue braces on a flat surface: if arched, glue braces on an arched surface. That's regardless of how you chose to clamp them while the glue dries.

Seems pretty self-evident. Am I misunderstanding your question?

The braces for a Dreadnought are radiused. If you clamp to a flat surface some of the radius of the braces will be reduced. If you clamp to a radius dish the radius will remain.

charles Tauber 01-18-2021 01:47 PM

Quote:

Originally Posted by Victory Pete (Post 6607934)
The braces for a Dreadnought are radiused.

Most are, yes.

Quote:

If you clamp to a flat surface some of the radius of the braces will be reduced.
True. Is that the result you want? If so, do that. If not, don't do that.


Quote:

If you clamp to a radius dish the radius will remain.
Also true. Ideally one would use a radius dish that matches the radius one wants to end up with (i.e. the same as the radius on the braces).

I still don't understand what is your question. It seems like you already know the answer. Glue radiuses braces using a radiused dish: glue flat braces using a flat surface.

Victory Pete 01-18-2021 02:16 PM

Quote:

Originally Posted by charles Tauber (Post 6607968)
Most are, yes.



True. Is that the result you want? If so, do that. If not, don't do that.




Also true. Ideally one would use a radius dish that matches the radius one wants to end up with (i.e. the same as the radius on the braces).

I still don't understand what is your question. It seems like you already know the answer. Glue radiuses braces using a radiused dish: glue flat braces using a flat surface.

My first build was a StewMac kit and the instructions were to glue the braces, which were radiused, on a flat board. That guitar was very loud. I have since bought a radius dish and have been using that but wonder if the first guitar was so loud because of the conflict of the radiused braces and the flat gluing surface, It seems to me that could make the top that much stiffer.

Alan Carruth 01-18-2021 02:46 PM

There are lots of anecdotes on this, one way and the other, but I'm not sure there's much actual data. Even 'identical' guitars made from 'the same' wood sound different, simply because it's a natural material and varies. I would hesitate to attribute a change in sound to some particular variable on the basis of a sample of two instruments. And, since all of us tend to hear what we expect to hear you'd have to do 'blind' tests.

I use arched bracing and radius dish throughout, but not for sound. Up here in New England the humidity and temperature changes so fast and so often, and swings so widely, that top and back cracks are the repairman's bread and butter. An arched top is less likely to split than a flat one, so using the radius dish is one way to keep the customers from coming back for the wrong reasons. ;)

Victory Pete 01-18-2021 05:48 PM

Quote:

Originally Posted by Alan Carruth (Post 6608041)
There are lots of anecdotes on this, one way and the other, but I'm not sure there's much actual data. Even 'identical' guitars made from 'the same' wood sound different, simply because it's a natural material and varies. I would hesitate to attribute a change in sound to some particular variable on the basis of a sample of two instruments. And, since all of us tend to hear what we expect to hear you'd have to do 'blind' tests.

I use arched bracing and radius dish throughout, but not for sound. Up here in New England the humidity and temperature changes so fast and so often, and swings so widely, that top and back cracks are the repairman's bread and butter. An arched top is less likely to split than a flat one, so using the radius dish is one way to keep the customers from coming back for the wrong reasons. ;)

My dish has a 28' radius, so it doesn't match the braces exactly which forces them down giving me some of that stiffness I want.

https://i.imgur.com/Si7bi7f.jpg

redir 01-18-2021 06:35 PM

I think I read once that at Martin Guitars they either do, or used to, glue radiused braces by clamping them down flat so that when they released the clamps the top would spring into the radius of the braces. I've never tried this though and I wonder what the purpose of doing so would be for. It seems to me that as mentioned it would reduce the radius but I can't quite mentally picture that in my mind.

charles Tauber 01-18-2021 08:13 PM

Gluing arched braces using a form of different radius won’t increase stiffness.

Victory Pete 01-19-2021 05:23 AM

Quote:

Originally Posted by redir (Post 6608266)
I think I read once that at Martin Guitars they either do, or used to, glue radiused braces by clamping them down flat so that when they released the clamps the top would spring into the radius of the braces. I've never tried this though and I wonder what the purpose of doing so would be for. It seems to me that as mentioned it would reduce the radius but I can't quite mentally picture that in my mind.

That puts stress and stiffness into the top. I see people doing different things online. I see flat braces glued using a radius dish which seems to do the same thing, create stress and stiffness in the top. So it seems to me you should not do both, radiused braces and a radius dish for clamping, You get no internal stress and stiffness.

Victory Pete 01-19-2021 05:24 AM

Quote:

Originally Posted by charles Tauber (Post 6608350)
Gluing arched braces using a form of different radius won’t increase stiffness.

I think it will, because the surfaces don't meet up perfectly, they will fight each other making stiffness.

Glen H 01-19-2021 10:39 AM

I think you’re confusing tension with stiffness

Victory Pete 01-19-2021 10:59 AM

Quote:

Originally Posted by Glen H (Post 6608717)
I think you’re confusing tension with stiffness

Not really, they are related. I have glued my radiused braces to a flat surface, like my first build, which has great volume.

https://i.imgur.com/bHxVwX9.jpg

John Arnold 01-19-2021 01:11 PM

Quote:

I think I read once that at Martin Guitars they either do, or used to, glue radiused braces by clamping them down flat so that when they released the clamps the top would spring into the radius of the braces.
Spring back is less than complete, so the result is less radius than what was cut into the braces.

In the old days at Martin, there was more spring back when gluing to a flat surface because the braces were not pre-scalloped. With pre-shaped bracing (CNC), I believe Martin uses radius dishes these days.
I glue uncarved (rectangular) braces to a radiused surface, but not a dish. I cut the radius into a 2X4, and use those 1 1/2" wide pieces to back up the top in the go-bar deck. This is a simple and effective system, particularly useful since I employ a compound radius on my tops.

Victory Pete 01-19-2021 01:31 PM

Quote:

Originally Posted by John Arnold (Post 6608869)
Spring back is less than complete, so the result is less radius than what was cut into the braces.

In the old days at Martin, there was more spring back when gluing to a flat surface because the braces were not pre-scalloped. With pre-shaped bracing (CNC), I believe Martin uses radius dishes these days.
I glue uncarved (rectangular) braces to a radiused surface, but not a dish. I cut the radius into a 2X4, and use those 1 1/2" wide pieces to back up the top in the go-bar deck. This is a simple and effective system, particularly useful since I employ a compound radius on my tops.

Are your braces radiused?


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