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Chris' thread on Brazilian rosewood bridge plates got me thinking about materials, and reminded me of this nifty idea from Bruce Petros http://www.petrosguitars.com/features.htm (hit the bridge plate tab there).

Basically, a big plate of spruce for the stiffening effect, and a small plate of ebony for the ball end protection. A full hardwood bridge plate is definitely more logical on factory guitars, where simplicity rules and tops are thick enough that the entire plate isn't enough bigger than the ball end section for material to make a difference. But if you build with a thin top and need a larger bridge plate to distribute the twist of the bridge, the hybrid plate seems like a better solution.

So, has anyone else tried it, and if so, what were the results?

There's also the option of a thicker and/or larger plate, versus a thinner plate with that cross brace behind it. Personally I'd probably go with a thicker plate, rounded on the bottom, and feather the thickness out. Also possibly have the hardwood plate notch into the X brace legs, rather than float in the middle. Not much more weight, and seems better connected.

Yes...I like it. Use it on ladder and X bracing.

haans, i like your sloped tail block.
lets the top vib better, no?
i think i'll start doing that.

Been doing it for some years. About 0.05" ebony or similar, the same of spruce for a total thickness of 0.100". Tonally, maybe a difference, hard to tell. Structurally, no problems.

Petros also does a laminated plate but I don't know what materials he uses.

okay, great idea.
thanks you all.
i'm going with spruce, with a lignum vitae patch.
i think it be better than ebony.
i'm also thinking, set up the
bridge before the back is on,
drill for strings, slot, etc.,
cleaner deal from the inside, no?

A bevel on the tailblock stops any distortion of the top around the block. I like the idea of Lignum. I have a block of it and might try it. It's darn dense and has interlocking grain. I flood the ebony plate with thin cyano.

I like the idea. I'm trying to decide if the grain of the spruce would be parallel or perpendicular to the top.

_________________
"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I do ladders at 90 to top grain and X brace at 45 to top grain.

lignum vitae , have you ever glued it? Does it need anything special? I was thinking about iot for bindings.
MM

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Mike McNerney

Sounds good guys, I'll give it a go
Hmm, maybe Petros laminates two layers of spruce with alternating 45 degree grain? Or maybe it just refers to the ebony patch being laminated onto the spruce plate. I was thinking about doing alternating 45's myself, but I'll probably just pick one and go with it. Probably grain in line with the saddle slant, especially since I'm thinking of doing multi-scale on the next one, so it will be mostly grain matched with the bridge, but stiffening longitudinally as well.

Setting the bridge location before closing the box is an interesting idea. You could make the string patch even smaller if you already have the pin holes drilled so you know precisely where it needs to be. I'm probably going to try an integral neck too, so the nut to bridge line will have to be locked before closing anyway.

I'll definitely be doing that beveled tail block design from now on too. I decided to leave it flat on my first for simplicity and to see what effect it has, and it does have a definite impact on the tap tone of the top around it. No dimples is just a bonus.

i would think the spruce would go 90 degrees to the top grain,
because if you used hardwood patch, the grain wouldn't matter on da spruce.
the hardwood would go at an angle.

The direction of the grain in the patch is determined by what you think the bridge plate does and how you think wood works. Start with what the plate's there for, figure out what properties are important to achieving those goals, and orient the wood so it maximizes those properties. Simple!

I am still a bit uncertain on exactly what the bridge plate does besides anchor the string balls. I have been using the spruce patch (about .04 or so) under a normal thickness but thin hardwood piece. The hardwood piece is usually about .1 thick and 3/4-7/8 wide and extends from x brace to x brace under the pin holes.

I have been using the spruce patch parallel to the grain and butting it up against a cross brace below the bridge. What I notice most is that if I have a very lightly braced top that any belly that occurs is centered further back and you don't get the crease style belly close to the bridge. I feel like it effects intonation less this way although I would prefer it didn't really belly at all.

I am trying it out as a cross grain patch on one I am working on now. I ran the other braces a little differently to accommodate this. I'm not really sure what to expect. It will be interesting to see if I really notice anything.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

got it, rick.
looks like 45 degrees then.
might help with bridge twist.
by the way, i liked that book by tim brookes that you are in.
good reading for a box builder.

This doesn't help at all.

Would that be 45 degrees towards the top or bottom?

_________________
"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.