Curved Laminated Bracing?
 

As mentioned previously, Sam Irwin, luthier and Tutor at Lagan Lutherie School, is experimenting with curved Laminated braces.
I thought we should post some pics and get opinions on this.
We're not sure if this has been done before, but if anyone out there knows of something like this, please let us know!
Please note, this is an experiment and we're not professing that this is the be all and end all of bracing!

https://lh3.googleusercontent.com/-Q...0/photo-11.JPG
(Bridge patch to be added)

https://lh3.googleusercontent.com/-3...0/photo-10.JPG

Each brace is two pieces of spruce glued together vertically over a curve.
At this early stage we're finding that the top is very stiff, allowing the overall mass of the braces to be greatly reduced compared to standard bracing patterns.

I sense controversy! Discuss!

(And on another note, we recently added some videos of guitars made at LLS to our Youtube Channel)

Curved braces have been done before. Lutes employed them in construction as early as C. 1600. Kasha/Schneider guitars employed curved braces. Neither were laminated. In the last 20 or so years, many luthiers have used straight laminated braces, often with carbon fiber.

I interpret this to mean that there are two pieces of spruce, each full height, that are glued and clamped face-toface against a curved caul/form (i.e. side ways). Is that correct?

An interesting experiment. Straight braces will offer lateral stiffness proportional to the thickness of the braces - primarily, they offer stiffness along a line. By curving the braces, the lateral stiffness is increased, potentially quite significantly, providing stiffness to an area, rather than primarily a line. That could be a good thing - or it could inhibit motion in a bad way.

If you wanted to decrease mass even further, you could use carbon fiber in your braces and/or drill lateral holes in the sides of the braces.

No, not really. :D I don't see any more or less rhyme or reason to it than a lot of other things folks have tried. If, empirically, it produces a perceived improvement in either sound or longevity, great.

Thanks for sharing what you are doing.

I believe Trevor Gore is currently using curved, laminated bracing. I haven't had the pleasure of playing one of his guitars.


People will find controversy in anything. I suspect it created some controversy when CF Martin started using an X brace. Inovations, reguardless of whether they work or not will cause some people to talk. I don't see myself using curved laminated bracing, but I will enjoy watching this thread, and would enjoy playing a guitar with it. I wish you and Mr Irwin much success with your project.

Hi Charles,
Yes Sam actually uses curved braces in the construction of his lyres, which have quite a large amount of strain proportional to their size, but we're not sure if the idea had been applied to a guitar. And yes your correct in saying, "there are two pieces of spruce, each full height, that are glued and clamped face-toface against a curved caul/form"
We've had students here use Carbon fibre braces on 12 Strings and Bouzoukis

Thanks for your input!

I've built a few with a very similar bent bracing pattern a few years ago. I too was amazed at how much more stiff the top was. My result was a very resonant guitar with a very unique tone. The tone was too non traditional for me though and I haven't done it since. There's also Trevor Gore who does bent bracing and just wrote a book about it. I hope you post some sound clips when you are done so I can see if your result was different than mine.

In my experience, there's the rub. From what I've seen, the further one deviates from conventional design, the further the tone tends to deviate from conventional "guitar sound". Chances are, however, one or more players will find that sound to be their preferred sound. If only one or two players find it "right", it won't be a very successful design. If many players find it "right" it will be very successful.

For me, a mental framework a la Somogyi helps a bit in terms of where you want increased stiffness, where you want more or less mass, etc.

It's a function of which vibrational modes you want to let ring or squelch and the frequencies you want to amplify.

To me, that top looks like it'd be too stiff for any monopole action, and it has too much longitudinal stiffness (where the spruce is already stiff).

Can't comment on the monopole action, but the longitudinal stiffness is exactly what I liked about it. It might counter the tendency of the guitar to fold into the soundhole from both the bridge and the neck. Might even address the deformation that necessitates neck resets.

However, it is all speculation: the proof is in the pudding and the proof may take decades before one can conclude much structurally, though one should be able to determine if one likes the sound or not in relatively short order, regardless of what the mono, duo or tadpoles do. ;)

Yes, structurally it looks like it should be very robust.

But guitar players like their bass response, and my guess is that this guitar will have a fairly weak bass response. It'll probably sound lovely in the high-frequency registers, though.

I was looking at some old ladder-braced parlors just the other day. Sort of the opposite end of the spectrum -- virtually no added longitudinal stiffness.

Most of them had the usual belly, sound hole sinking, etc. But one of them didn't. 60+ years old and looked like new. The only differences? Reasonable sound hole reinforcement and a larger-than-normal bridge plate.

Sometimes, it doesn't take much. Stiff and light isn't necessarily a good thing. If it were, we'd all be using lattice bracing. :)

Thank you for sharing
 

What are the goals that you wish to achieve with this design; i.e., volume, projection, frequency response, type of musical application? Can you share the dimensions and materials as the build progresses towards said goals? It is hard to sail beyond the x brace paradigm for steel strings and classical designs for nylon gut guitars. It seems as though the proper course is to create an entirely new flavor of stringed instrument al la Smallman. Experimentation is necessary and I thank you for sharing your journey.

I tell you what, go ahead and finish it... send it to me and I'll give you a great written review. I get to keep the guitar of course. :D

Thanks for the comments so far everybody. We're very much of the thinking that you'll never know until you try!
We'll certainly keep you updated as the build progress. Although, Sam is so busy it may be a while before its finished.

I can't speak for him in what he's trying to achieve sonically with the tap tone. I don't think hes looking for a specific frequency response, but instead a good range of audible frequencies, and a specific double decay in the sustain that he normally goes for.
I'll have to get him to explain his thoughts...possibly in a video!

Some others have made questions as to what is the desired effect of the curved braces. I would also wonder how the designer wishes to manipulate the transmission of sound vibrations through the top, given that braces affect top resonance both through their stiffness and through their direct sound transmission.

Can you explain this "transmission" thing to me? I've seen that analogy before, and I don't really get it.

If anything, braces seem more like "anti-transmission" devices. Imagine a trampoline. If it's braced only at the rim, you can freely jump up and down anywhere. If you add braces within the rim, you create areas that aren't as bouncy.

Braces do "shape" how the top vibrates, though. Using the trampoline analogy, by X-bracing the trampoline, you create a trampoline that has 4 bouncy mini-trampolines (with a higher resonance frequency than the large trampoline). And if you don't couple the X to the rim, the trampoline will still bounce up and down if you jump on it near the center of the X. It'll also bounce from side-to-side and end-to-end.

I don't know about the bouncy mini-trampolines ;-) but here is a try at explaining the use of the word transmission.

The sound wave (vibrational energy) initiated by the player, created in the string, transmit to the saddle & bridge, then transmit onto the vibrating top of the guitar where the air molecules are hit and the soundwave continues to be transmit to the listeners' ears.

So it is all about the transmission of vibrational energy from one substance to the next. The top of the guitar is what sends the sound vibration into the air.

Sound waves travel faster and more efficiently through dense objects rather than gases (air), so part of the function of braces on soundboards is also to transmit more volume of sound waves to all parts of the top faster than the soundwave can travel through air - virtually (but not precisely) instantaneously.

Then, "ping", the top is vibrating, and the audience is happy.

All due to the transmission of sound vibrations.