Bridge plate question for Rick Turner, or anyone else with an answer.

Hi Rick,

You mentioned that you do not use bridge plates in your Compass Rose uke. What exactly is the purpose of the bridge plate if you don't have to use it? Do you compensate with the bracing? Does eliminating the plate improve the performance of the instrument?

Thanks

You could say that a bridge plate has several uses. It's use or not depends on instrument design and material that the top is made from. Ie, hard wood or soft wood. It's cross grain stiffness has a big factor in some of these considerations.

A bridge plate is usually a hard wood but doesn't have to be, and in string through top instruments it helps reinforce the area under the bridge so that the ball ends or knots on strings don't damage the top itself. Think steel string guitar here, but the same goes with other instruments.

It also adds cross grain stiffness to the top. Depending on what the builder wants to accomplish here, the size, thickness and shape of the bridge patch is matched to their design intent.

It can be shaped to add some dome to the top prior to being glued in, aiding in the tops geometry.

You can't make a blanket statement one way or the other on "Does it improve the performance of an instrument". It depends on far too many factors that only the builder will know after building a great many instruments in their own style.

like what Allen said. Rick also uses CF-reinforced cantelevered fretboard extension so the top is free to vibrate as a whole.

So the bridge plate is not always necessary to help keep the top from distorting from string tension?

You can think of the bridge plate as an extension of the bridge itself. A larger bridge can require a smaller plate and vise verser. That's kind of simplified. They work as an inseparable unit. You can't consider one without considering the other.

I use a hardwood bridge plate to protect the underside of the top from the string knots on my string-through bridges.

The first two ukulele I built were 6 and 8 string tenors. The bridges came off after 2 weeks. Bob Gleason did the repair for my man in Hawaii and advised - "Next time tell him to put a bridge late in them!" Now I ain't and haven't ignored that advise from the grandaddy of them all...

Then if my top is exactly 1.8mm thick, the hardwood bridge plate should mimic that thickness, and run opposite the direction of the top grain...correct? Did your bridges come off because the top distorted because of the absence of the plate?

The bridge is a small, thick chunk glued to large, thin chunk. As the wood responds to changes in atmospheric humidity and tempurature, this glue joint undergos a great deal of stress. The tension of the strings and the difference in wood density between the soundboard and the bridge add to this stress. The primary role of the bridge plate therefore is to stabilize the atmospheric response of this crucial area of the soundboard. For this reason, it is traditional and most helpful to use the same or a very similar wood for both the bridge and the bridge plate.