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I'm almost afraid to ask this because I suspect it is a stupid question (and yes, I do believe those exist), but I couldn't find a specific answer in my searches.....

Why use a bridge patch on a top with a pinless bridge (ie: some ukes and classical guitars)

I read and was taught that the function of the plate is to prevent the strings from chewing through the top. I can imagine that it helps strengthen the top under the glued-on bridge, but if you were to use reinforcing strips in a low tension instrument like a cl or uke, would the loss of the plate be a factor?

My particular interest in the answer to this is that I would like to lighten my uke bracing, and wondered if one would gain anything (or have an unacceptable loss) by eliminating that rectangle of spruce.

Thanks, Beth

Hi Beth.
I don't use a bridge patch on ukes.

I understand that when gluing up flat pieces of wood, you are creating stresses that can cause waves, so it is usually better to have 3 pieces of wood in a laminate, to balance the stresses, maybe not induce a curve.
So, in a sense, the patch is the 3rd part of a good laminate.

All that being said, I still don't use a patch on ukes.

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I asked a similar question recently and was referred to David Hurd's write up here:
http://www.ukuleles.com/Technology/bridgesize.html
He uses a very thin CF Shear Web bridge patch.

Beth:
I am using a veneer strip (0.024" thick crossgrain) as a bridge patch on my present concert uke. It is required because of the Hana Lima style tie-through bridge. This concert has only the Koaloha style "unibrace" which is a single bulkhead brace at the waist.
could you use thinner bracing. I have used 0.070" thick bracing on a Kasha braced baritone.

What bracing patern are you using?

Bob

Thanks all!

Bob, I'm using a fan braced pattern on the Hana Lima plans. My bridge has a tie block like the classical guitar bridge.

I really think I'm overbracing the tops. I like the idea of a light web patch.

Beth

Mark, that article was really helpful. It answered the "why" question, and gave detailed discussion of what I think will be a better way to do it. Thanks so much.

I'll throw another opinion in, because I'd like to see more discussion of this. There are plenty of relevant differences between classical guitars and ukes (e.g. string tension, bridge shape, top thickness, desired tone ), but just for fun, let's think about classical guitars. Most of these have bridge patches, and for the same reasons that ukes have them: reducing changes in action as the humidity swings, and reinforcing the stress concentration at the forward corners of the bridge.

Famously, Antonio Torres built his guitars without bridge patches (unless he occasionally used them, in which case, I'm famously ignorant). I'm intrigued by a lot of recent innovations in classical guitar design. I build Nomex double tops, and have plans to build some lattice-braced guitars. Still, for me, the answer to most classical guitar questions is: "What would Torres do?" Many of the best sounding classical guitars I've played were based on a simple, no-bridge-patch, Torres fan-braced pattern. For a few years, I did warranty repairs for a small company that made a "Torres" model. They also imported a similar model from China. Neither of these had a bridge patch, and neither of these were prone to top cracks near the bridge, or action problems. I did repairs for several models from this company, and got to compare results from over 1,000 guitars, some with bridge patches, and some without.

Importantly, Torres made some design decisions that reduced the bridge-corner stress riser problem. His tops were thinner than almost anyone attempts today, but he made sure that the forward corners of his bridges were positioned directly over a brace. The "Torres" models that I serviced didn't have this feature, but their tops had a more "modern" thickness.

And action? I would imagine that a bridge patch would reduce changes in top doming. I don't know if this is true, but it seems like it should be. Is this a good thing? One thing I like about classical unbound fret boards is the feedback they give you about humidity. If you start noticing the fret ends, it's time to humidify. Some people are very sensitive to this. Others just go on playing. When everything starts buzzing really badly, some of the latter group call their guitar tech. I think I rescued a good friend's steel string when he called from abroad to wonder why his Martin was suddenly buzzing. Slipping a shim under the saddle will get you through a gig. Is it really better to be unaware of what's happening (or about to happen) to your guitar (ukelele) ?

Oh, and I understand that Romanillos went through a no-bridge-patch period, and then started using bridge patches--maybe adjusting to the non-mediterranean climate of England?

Okay, fire away.

Torres never used a patch, and I guess same goes for the great Spanish makers before WW2. I think the patch become widely used after the success of Hauser.
A patched soundboard has the advantage of offering a more solid surface on which to glue the bridge. It obviously works without, but on my guitars where I add a bridge brace, I feel that the bridge fitting goes a bit better.
Another thing a patch can do is to fix an erratic bridge. Some are very dense, when you thin them to a decent weight they become floppy. Others are low density, unless you make them chubby they are too light and again too flexy. For these a patch will help bring the stiffness and weight more in line with a regular bridge.
As for the sound, they don't do much. I shaved a couple with minimal tonal change if any. Exactly what Romanillos thought when he was done with them.

Another type of patch or brace used under the bridge is the longer-than-the-bridge one, and these can go as long as almost the entire LB and they definitely have a tonal effect (from some to a big lot) not just structural.

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