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Laminated braces?

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Bill Greene

Post subject:

Posted: Thu Sep 06, 2007 6:29 am

Koa

Joined: Wed Jun 01, 2005 6:35 am
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Location: Kings Mtn., NC, USA
First name: Bill
Last Name: Greene
City: Kings Mountain
State: North Carolina
Zip/Postal Code: 28086
Country: USA
Focus: Build
Status: Amateur

And what adhesive would someone use to laminate CF to brace stock, epoxy?

Thanks.

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Bob Garrish

Post subject:

Posted: Thu Sep 06, 2007 6:34 am

Brazilian Rosewood

Joined: Tue May 02, 2006 9:02 am
Posts: 2351
Location: Canada
First name: Bob
Last Name: Garrish
City: Toronto
State: Ontario
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Status: Professional

Arg, you're totally right (Tony and Mike). For some reason I was interpreting the statement as implying the center lam should be set in as all short grain, like one would do when laminating sides together, and it just made no sense. Too many perpendiculars in three dimensions.

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Steve Saville

Post subject:

Posted: Thu Sep 06, 2007 7:24 am

Contributing Member

Joined: Sat Nov 26, 2005 7:32 pm
Posts: 1969
Location: United States

People who ride road bikes and mountain bikes understand real well that CF has 2 important characteristics -
1) Strength to weight ratio.
2) Stiffness.
3) Vibration dampening.

The vibration dampening is very real. It does a great job of smoothing out the ride. It is used for frames, handlebars, forks, seat stays, stems, etc.

Just a guess - the high vibration dampening characteristic might not be the best thing in most steel string guitars.

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Mattia Valente

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Posted: Thu Sep 06, 2007 8:42 am

Brazilian Rosewood

Joined: Wed Jan 05, 2005 6:25 pm
Posts: 2749
Location: Netherlands

The amount I'm talking about (and Mario uses) is really pretty minimal, and in terms of 'tap tone resonance', I don't hear huge/significant differences. Certainly not in terms of damping and/or ring, although I'll do a little more testing when I get the big stuff laminated up (X-braces, which is where I'm using it). Keep in mind I'm talking loose sticks of binding right now, not the easiest things to tap. The goal is to add enough CF to get rid of a memory effect, and longer term deformation (ie, bellying), not to add massive amounts of stiffness, if any at all.

We put CF in necks, after all, and I like what it does to those (mine resonate longer and at a slightly higher pitch, good sustain, after I glue the bars in compared to before gluing in the bars. It's selective stiffening that affects the main vibrational modes, but for necks at least, it does it in a way I like.

Anyway, I'll shut up about it now until I've actually finished a guitar with CF braces in it.

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Michael Dale Payne

Post subject:

Posted: Thu Sep 06, 2007 9:02 am

Old Growth Brazilian

Joined: Tue Dec 28, 2004 1:56 am
Posts: 10707
Location: United States

[QUOTE=ToddStock]
As for cool? I personally think a nice composite bowl-shaped back, a raised rosette made from mother-of-toilet-seat, and a single-piece cast aluminum neck would be oh-so-mega-cool...[/QUOTE]

Humm???? sounds like 1977 model Applause. you need one

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Steve Saville

Post subject:

Posted: Thu Sep 06, 2007 10:06 am

Contributing Member

Joined: Sat Nov 26, 2005 7:32 pm
Posts: 1969
Location: United States

[QUOTE=MichaelP]
Humm???? sounds like 1977 model Applause. you need one

[/QUOTE] You got one? They make great beach/camping guitars, personal protective devices, and while not as good as Martin backpackers, they can can be decent canoe paddles in a pinch.
You just can't say that about any of our instruments.......well most of them....

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Jim Kirby

Post subject:

Posted: Thu Sep 06, 2007 11:33 am

Brazilian Rosewood

Joined: Tue Nov 29, 2005 11:44 am
Posts: 2186
Location: Newark, DE
First name: Jim
Last Name: Kirby
Focus: Build
Status: Amateur

I'll jump in here pretty late, and perhaps misguided...

One application in the lattice brace world is to cap the brace with the carbon fiber, right? So the fiber sheet is parallel to the top, separated from the top by the height of the brace? Some of the lattice braced guitars use this over a balsa brace, if my memory serves. ( Hard to commit this all to memory, when it's so esoteric. Actually, given the usual impression that the classical world is so set on the basic design of each of it's instruments, I'm impressed that a lot of the innovation in the classical guitar world is really out there, compared to the historical designs.)

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grumpy

Post subject:

Posted: Thu Sep 06, 2007 2:12 pm

Koa

Joined: Wed Aug 22, 2007 11:58 am
Posts: 1667

ust a guess - the high vibration dampening characteristic might not be the best thing in most steel string guitars.

bad guess(and a pet peeve with these forums is the number of guesses posted...).

Yes, CF will have higher damping properties... when compared to the metals otherwise used in bikes. When compared to woods, CF has much, much less damping.

We don't build bikes......

And yes again, CF, when used as i do, will add weight, though minimally, to the brace, stiffness to stiffness. But a higher stiffness to weight ratio wasn't my goal in using CF; for that, cap it. But be careful capping braces, for it's ridiculously easy to overbrace at that point, with no recourse, other than ripping the cap off. The world's lightest bracing scheme still won't make a sound if it's so stiff the strings can't make it move.

I have more evil goals for its use...

Muahhahaha!!!

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uncledave

Post subject:

Posted: Thu Sep 06, 2007 3:11 pm

Walnut

Joined: Tue Jun 26, 2007 3:04 am
Posts: 14
Location: United States

The Left Brain Lutherie forum did a big thread on this recently. One of their engineer types did weight/stiffness tests with CF/spruce braces vs non lam spruce only braces and came out that spruce only braces scored better on weigh/stiffness. (Note: this was my interpretation,,, to be taken FWIW)

Prob being that the lamination such as in the pic from McPherson tho cool looking, wastes a lot of the CF's properties.

An I-BEAM structure with the CF on the top, the spruce brace as the web, the soundboard as the opposite piece to the CF was stronger in a weight/stiffness test.

Reason being that using CF in the web of the beam places it where it flexes less, instead of out on the top of the I BEAM where it acts in compression/tension.

McPherson = lots of weight, not as much stiffness gain compared to I-beam structure, tho great marketing. Some things are just cooler'n hell. (Ray Wylie Hubbard said that)

So, I side with Todd

Who the heckam I and what does it matter what I think?

Dave

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grumpy

Post subject:

Posted: Thu Sep 06, 2007 3:27 pm

Koa

Joined: Wed Aug 22, 2007 11:58 am
Posts: 1667

<sigh>

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Rick Turner

Post subject:

Posted: Thu Sep 06, 2007 3:58 pm

Koa

Joined: Wed Aug 24, 2005 11:13 am
Posts: 1398
Location: United States

I top back braces with .021" CF and also top the back center seam reinforcement strip with the stuff. The back braces bridge over the continuous center strip. It's unbelievably strong. The first one I did was on HK's Antarctica guitar and I only did the back braces. I was able to stand on the back before I glued the top on.

On my latest acoustic, I lined the reverse top kerfing with CF and then used CF for binding around the top. You want to talk stiff and strong? Once again, unbelievable... It's all in the engineering as to whether you take full advantage of the stiffness properties of CF.

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Kent Chasson

Post subject:

Posted: Fri Sep 07, 2007 3:31 am

Koa

Joined: Fri Mar 23, 2007 9:56 am
Posts: 1271

Rick, this may deserve another thread but what's the advantage of that much strength/stiffness in a box? I'm a believer in stiff boxes and use solid linings and round shoulders and butts (except on my dreads, although I'm working on that) to make them stiff. But I would expect diminishing returns as you go stiffer than that. What makes it worth that much effort to go from stiff to bombproof? I assume the bindings in particular add some noticeable weight too? Are you trying to get rid of the buttresses in the process?

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Bob Garrish

Post subject:

Posted: Fri Sep 07, 2007 3:52 am

Brazilian Rosewood

Joined: Tue May 02, 2006 9:02 am
Posts: 2351
Location: Canada
First name: Bob
Last Name: Garrish
City: Toronto
State: Ontario
Country: Canada
Status: Professional

[QUOTE=Kent Chasson]

Rick, this may deserve another thread but what's the advantage of that much strength/stiffness in a box?\

[/QUOTE]

They'll get a big surprise if they ever try to use one of Rick's guitars in a Juicy Fruit ad

(For those outside North America, or who don't watch TV, there was a series of ads last year of some hooligans running around smashing guitars on people)

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

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Rick Turner

Post subject:

Posted: Fri Sep 07, 2007 2:34 pm

Koa

Joined: Wed Aug 24, 2005 11:13 am
Posts: 1398
Location: United States

I am basically building in an ultra stiff skeleton to which wood is attached. I'm pushing the wood parts thinner and thinner now, and the guitars just sound better and better to me. Bear in mind that there are other things that are somewhat "off center" about this series of guitars...the graduated top, fan bracing coupled to the X, flying buttresses, cantilevered fingerboard...on and on.

What I'm trying to achieve (and it seems to work) is a lot of headroom, really good harmonic sustain, and almost archtop midrange punch, but supported with flattop low end.

The carbon fiber binding is not significantly heavier than celluloid would be. The trick is in engineering where the CF is used, and as surfaces on structural elements, I'm maximizing the modulus potential.

I understand the usage as a center vertical lamination, but that isn't the most efficient use from an engineering point of view, though it does allow later "voicing" which my system is not great for.

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