Fan braces over bridge patch

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AndrewE

Posts: 56
Joined: Oct. 6 2004

Fan braces over bridge patch

What is the general way that fan braces are fitted over a bridge patch. By that I mean;

does the cutaway section of the braces come in contact with the bridge patch and glued to the plate?

or is there a small clearance gap between the plate and the braces and consequently no glue in the bridge patch area?

Andrew

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 11 2007 17:54:34

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Fan braces over bridge patch (in reply to AndrewE)

Hi Andrew.

I think its a wrong idea to fit the braces above the bridge patch. You will clearly loose strength where you need it the most. If you can make a perfect fit and I mean perfect with a big P (I cant) then glue it above. If not, do like me, cut channels in the patch where the braces pass and glue the braces directly on the soundboard.
Remember the braces are there in order to strengthen the top lengthwise and the less unnescessary weight, the best.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 11 2007 18:37:01

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: Fan braces over bridge patch (in reply to Anders Eliasson)

quote:

ORIGINAL: Anders Eliasson

If not, do like me, cut channels in the patch where the braces pass and glue the braces directly on the soundboard.

I don't understand the purpose of the bridge patch. I suppose it could be a way to hold the side to side arch in the top, or perhaps if it is extended past the ends of the bridge it can help to prevent those annoying little ripples that can occur there. It would seem to be worthless for preventing checks from running past the bridge since the bridge does that already. Is it just a device to support the bridge while gluing? I've tried it in the past and couldn't see any effect on the sound so I dropped it. Why add superfluous weight?

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 2:32:18

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Fan braces over bridge patch (in reply to AndrewE)

John, How do you fix the bridge when you glue it on?

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 3:02:49

aarongreen

Posts: 367
Joined: Jan. 16 2004

RE: Fan braces over bridge patch (in reply to AndrewE)

I fit the braces to the bridge patch, when I use a bridge patch that is. Anders is right in that you need them to fit together well but I think to cut through the patch to the top is pretty much making the patch useless. The patch serves to increase the cross grain stiffness in that area and perhaps keep the top from distorting as much as it might between the braces.

Since your braces are taller than the patch, I don't think your losing any strength in the braces when you notch them out for the patch. Dake Traphagen builds a model whose bracing he attributes to Hauser II that has cutouts under the bridge as if there was a bridge patch, but without the bridge patch. I could be wrong in this analogy but it makes me think of a suspension bridge.

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 3:45:21

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: Fan braces over bridge patch (in reply to Anders Eliasson)

quote:

ORIGINAL: Anders Eliasson

John, How do you fix the bridge when you glue it on?

We sand the bottom of the bridge to fit precisely the arch in the top then use cam clamps and cauls. Same way you do it I suspect.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 5:49:51

AndrewE

Posts: 56
Joined: Oct. 6 2004

RE: Fan braces over bridge patch (in reply to jshelton5040)

quote:

ORIGINAL: John Shelton;
"I suppose it could be a way to hold the side to side arch in the top.."

I using the vague Reyes plan put out by T.Blackshear and the top is basically flat in the bridge area. The patch is 1/32" thick under the bridge and tapers to nothing either side of the bridge. The patch cross all 7 braces in this design.
Being so thin either side of the bridge it seems hard to see how it would stop any wrinkling.

The more I look at it the more they look superfulous.

Andrew

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 10:07:25

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Fan braces over bridge patch (in reply to AndrewE)

Even the thinnest patch will stiffen. Not so much because of the strength of the patch but because of the crossgrain lamination.

John, I´ve done just as you say when I dont use a patch and I´ve pinned the bridge with a patch underneath.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2007 19:09:24

jshelton5040

Posts: 1500
Joined: Jan. 17 2005

RE: Fan braces over bridge patch (in reply to Anders Eliasson)

quote:

ORIGINAL: Anders Eliasson

John, I´ve done just as you say when I dont use a patch and I´ve pinned the bridge with a patch underneath.

If you're pinning the bridge it is logical to use the bridge patch for more support. We use masking tape to keep the bridge from sliding during gluing.

As far as "cross grain stiffness" I don't see how a thin layer of spruce or cedar could add much more stiffness than the bridge itself. Unless of course you extend it past the edges of the bridge. Extending the patch past the edges of the bridge will likely have an effect on the guitar's voice since you would essentially be enlarging the bridge's footprint.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 13 2007 3:05:55

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Fan braces over bridge patch (in reply to AndrewE)

Yes, I talked about extending the patch. It gives more harmonics and the top lifts a bit more. I do it on classicals but not on flamencos, even though I know that Barbero used to do so.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 13 2007 19:37:31