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Capping the x-brace
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=32396		 Page 1 of 1
Author:  Ken Mitchell [ Wed Jun 01, 2011 7:17 am ]
Post subject:  Capping the x-brace
I remember readiing some time back about the benefits (and different ways) of capping over the x-brace when bracing an acoustic guitar top. People were commenting on how much strength that added back, something impressive, like 20% (?).

The search engine doesn't like the 'x' in 'x-brace'. Does anyone remember what the numbers were on the strength that is added back by capping?

TIA,
Author:  Corky Long [ Wed Jun 01, 2011 7:57 am ]
Post subject:  Re: Capping the x-brace
I don't remember any quantification of the increased stiffness, but for me it's a no-brainer. The added mass is negligible, and for me, it's a neat little cap which is aestetically pleasing. As for technique, all I do is plane the joint flat at the top with a couple of passes of my block plane, then glue a piece of scrap spruce from an offcut from a top - with grain running parallel to the "bottom" x-brace (correct orientation is obvious, but hard to describe). Once it's dry I shape it with a chisel, then sand. Glue lines almost invisible, and I'm sure it adds to the stiffness of the top, and the joint.
Author:  Dreadnuffin' [ Wed Jun 01, 2011 10:47 am ]
Post subject:  Re: Capping the x-brace
Here's a very informative discussion on the merits of capping/notching x-braces.
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=29400&hilit=capping+brace
Author:  Tom West [ Wed Jun 01, 2011 11:11 am ]
Post subject:  Re: Capping the x-brace
Todd's picture looks like an example of a lot of things NOT to do. Besides the cloth patch. Runout in the X brace. Maybe a pickguard crack from gluing a pickguard directly to the wood.Also appears that no caul was used during the drilling of the bridge pin holes. A lot of learning info in one small photo.
Tom
Author:  Laurent Brondel [ Wed Jun 01, 2011 11:49 am ]
Post subject:  Re: Capping the x-brace
Only a '70s Martin is good enough.
The glue soaked cloth patch is a valid cap though.
Author:  Howard Klepper [ Wed Jun 01, 2011 12:56 pm ]
Post subject:  Re: Capping the x-brace
The cloth patch adds a littel strength. It is mainly there to hide that Martin pre-shaped their braces before notching them, so there is no contact in the supposed lap joint in the upper half.
Author:  Pat Foster [ Wed Jun 01, 2011 3:00 pm ]
Post subject:  Re: Capping the x-brace
Howard Klepper wrote:
The cloth patch adds a littel strength. It is mainly there to hide that Martin pre-shaped their braces before notching them, so there is no contact in the supposed lap joint in the upper half.


...therefore nothing to break!

Todd, is that a factory-built guitar?

Pat
Author:  gozierdt [ Wed Jun 01, 2011 4:48 pm ]
Post subject:  Re: Capping the x-brace
I look at it this way. The x-brace that is notched on the side next to the top has a "cap" on it, since it's glued to the top. The top acts as a "cap", about .100-.110" thick- whatever the thickness of the top is. So on the brace that has the notch on the brace facing up, away from the top, I want to create a similar situation to keep the two x-braces of similar strength. So I put a cap about the same thickness as the top across that notch. Now both braces are more equal in strength. One could argue that the notches are glued to each other, so no cap is needed, but those end-grain joints are very weak. I wouldn't count on them to not crack when the joint is stressed.
Author:  nickton [ Thu Jun 02, 2011 2:20 am ]
Post subject:  Re: Capping the x-brace
Interesting grain on that x brace. Certainly doesn't look like it came from a split billet. Great picture. Eat Drink
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