Official Luthiers Forum!

hi there,

Just wondering what people’s thoughts/experiences are in bracing patterns for a standard pined bridge vs a string through pinless design bridge.
Is there for example any need for a bridge plate? There is a lot of force on that area, would seem strange to leave it bare.
Are there any common solutions to the additional shearing force given that the strings aren’t anchored through the soundboard?

Interesting question.
A bridge plate has been used by some classical guitar makers (Hauser) and not used by others (Hernandez). Romanillos said he felt it created stresses in the top and others have felt it "balances" the construction (similar to plywood).
I - generally - use them when I use a pinless bridge and for a steel string instrument I think it is prudent. If the pinless bridge is a failure replacing it with a pinned bridge would not be too difficult.
Another advantage to using it is it can provide some additional structure if mechanical fasteners are used to counter the peeling force on the bridge. On some of my steel string pinless bridges I have used tiny bolts bolted through the top and hidden under MOP dots ( the nuts are epoxied on because the vibrations of the top will make them come loose ). On others I have increased the width of the bridge to help counter act those forces. Classical guitar bridges seem to survive O.K. without any additional "anchoring" measures, some in fact have done O.K. with narrow "lute like" bridges.

Breedlove has been making guitars with pinless bridges for many years and their guitars have bridge plates. As far as I know, the bridges are glued to the top without added mechanical fasteners.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I've made guitars with a couple of styles of "pinless" bridges and prefer the Elliot style (which is more like a permanent pin bridge).
I've always used a bridge plate as I still want some added stiffness in that area. Depending on the design, I have used a spruce plate in some instances, though.
I'd think you'd run a greater risk of having your bridge peel at some point using the type of bridge you'e talking about with no plate.

William

I also make sure the bridge wings extend out to the x-braces. I built an acoustic bass and had to narrow the x-brace pattern to get there.

Lowdens have bridge plates too, with pinless bridges. The function of the bridge plate is not just to hold ball ends of the strings in pinned bridge designs. It also stiffens the top under the bridge to resist the rotational force that the strings apply to the bridge. For this reason it is important that the bridge plate extend forward beyond the front of the bridge, and not just cover the back where the pin holes are. So, in a pinless design a bridge plate can still serve this structural purpose. Many classicals are built without them and get away with it because of the lower string tension. I am sure some pinless steel strings have been built without a bridge plate also - and might have got away with it if the top is thick enough or the bracing a bit heavier. But I think it would be inviting some trouble.