Question on bridge patches

[Matt Fisher]

Hello All,

I am just working on my second build, a grand concert cutaway type with black acacia back and sides and a spruce top with standard style X-Brace pattern. I experienced some difficulty gluing the maple bridge patch in and realized that it had warped and was unsuitable so I have gone back to square one with it. Due to a deficiency in scrap maple or rosewood I may use a bit of the black acacia or even a bit of ebony. Then it got me thinking....

The bridge patch is usually flat but is glued onto a radius'd soundboard and I wondered if this caused anyone any problems?

Does anyone radius or even bend their bridge patches to suit the internal radius of the soundboard?

I have seen one or two people online who use laminated patches formed to the radius of the top and some who have played around with different materials such as carbon fiber to get around this.

I'd appreciate some guidance from those more experienced than me!

Thanks

[ken cierp]

Forcing the sound-board into "unnatural" shapes and contours can and often leads to problems during construction and for sure down the road. This is wood not a " a sheet metal stamping" We spend time and good money procuring dry flat material -- the notion that we then need to force it into a different shape seems counterintuitive to me. There is no question that changes in relative humidity are going to cause the bent flat work to do weird things. So for those reasons I see "zero" value in trying to put a contour (carved or forced) on such a tiny piece of wood. Leave it flat and as a matter of fact, I recommend using the bridge plate as the true position locator for all the other bracing as demonstrated here:

http://kennethmichaelguitars.com/topassembly.html

[ken cierp]

Just as a side bar to this thread --- keep in mind that the most prized vintage Martins and those constructed today are "flat top guitars" the braces are only slightly contoured to 52' to prevent the appearance of concavity -- there is plenty of incorrect conventional wisdom that looses site of this reality. And the best sounding most expensive "R Taylors" are also flat with a 65' option.