brace design question

[peter havriluk]

I'm in the midst of laying out the bracing for my 93%-of-full-size scratchbuilt dreadnaught. I make a reduced copy of StewMac's Herringbone drawings and I'm proceeding from there. Interesting thing, I was laying out the bridge position for my all-but-24-inch scale length and I'm running into a traffic jam. The x-brace can be shifted forward a bit so as to allow a larger bridge plate, big enough to cover more of the bridge footprint, sort of, but the x-brace will leave a lot of the bridge overhanging their outer edges past the bridge plate. I can change the x-brace intersection angle from 92 degrees, as measured, to 100 degrees (tenths not included) to give the bridge plate some more width. Problem being that while the body be shrunk, the bridge is not.

Comments, reactions, advice and warnings will be gratefully received.

Thanks, folks.

[John Link]

I'd say, shorten the span of the bridge. The point of the extra length ("wings") is to reach over the X-braces, thereby forming a triangle. Once that is achieved, extra wood is simply adding to the resistive mass that plucking the strings must move to make sound. You might start thinning the thickness of the bridge as early as possible, once the saddle is accommodated - even less mass and it might improve the appearance of the bridge.

[ken cierp]

Martin uses 6" long bridges on just about every model, so that is not an issue. Make sure you are not drilling pin holes through a brace and into the bridge plate ----- you'll be OK. As a matter of design spreading out the "X" is a good idea, there's a lot of string tension lost with such a short scale length. Freeing up the lower bout most likely will improve responsiveness.

[peter havriluk]

Thanks, folks, for the replies. Little by little I'm picking up design considerations. Wonderful parts of the project, too. Much obliged. Already thinned the wings when I made the bridges. Now I know why that's a good idea. Kinda' contrary to 'pyramid bridges', I think.