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Parabolic Bracing?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=20634		 Page 1 of 3
Author:  Blain [ Thu Jan 22, 2009 7:45 pm ]
Post subject:  Parabolic Bracing?
I want to give Parabolic Bracing a try on my next guitar.
It will be an OM sized guitar.

I was wondering what would be a good height & width to start off with for the various braces before shaving them down(X Braces, Tone bars, etc...)?

Any reccomended finished height dimensions (ballpark)?

Also if anyone has some good pictures of some Parabolic braced tops, I would appreciate it. I've seen a couple pictures in another thread, but more is always better right? I'd be most interested in seeing some side shots of some braces to get some ideas of the side profiles. Then from there I'll just shave away and see if I can figure anything out while tapping.

Thanks in advance for your response.
Author:  James Orr [ Thu Jan 22, 2009 7:56 pm ]
Post subject:  Re: Parabolic Bracing?
Hi Blain. I haven't built one, but my notes tell me the X braces are .5" tall, tone bars are .25", and they're all .25" wide.
Author:  JJ Donohue [ Thu Jan 22, 2009 8:24 pm ]
Post subject:  Re: Parabolic Bracing?
Howard thoughtfully brought this up a few days ago but we never expanded on the topic. Why do folks refer to it as "parabolic bracing". Where's the parabola? Who started calling it so in the first place?

I often use non-scalloped bracing but refer to it as tapered bracing. Isn't this more accurate?
Author:  Hesh [ Thu Jan 22, 2009 8:35 pm ]
Post subject:  Re: Parabolic Bracing?
Yeah, yeah, yeah..... :D the term parabolic is incorrect I agree so just non-scalloped or tapered is probably more accurate.

My friend James has posted the dimensions that I use on an OM and it works very well for me. Also, I profile the braces so that the sides are triangles and free from excess brace material and mass.

So start a bit higher at the X-intersection then .5" and then plane down to .5" and cap. If you follow your ears when tap tuning you may find that the braces have a reverse taper below the X intersection and if your brace stock is very stiff. I am speaking of the lower X legs.

PS: If I can't call them parabolic anymore then I am going back to saying I am installing "kerfing" or working on a "build." :D
Author:  Blain [ Thu Jan 22, 2009 9:53 pm ]
Post subject:  Re: Parabolic Bracing?
Thanks James and Hesh.

Luckily this build that I'm working on, I've already installed the kerfing. :D
Author:  Rod True [ Thu Jan 22, 2009 9:56 pm ]
Post subject:  Re: Parabolic Bracing?
No, the term parabolic is NOT incorrect.

It's looking at the cross section when calling it parabolic, not the run from x-brace intersection to termination point at the edge.

Attachment:
bracing cross section.jpg


Look at many pictures of scalloped braces, they are not parabola shaped but more triangular.

Some bad factory guitars are actually rectangular in cross section, even if they taper from the x-brace intersection to the termination point.
Author:  Kent Chasson [ Thu Jan 22, 2009 10:21 pm ]
Post subject:  Re: Parabolic Bracing?
There used to be a guy around that specialized in re-shaping braces for people and his company was called "Parabolic Guitar Works" or something like that. He had a lot of theories about why parabolic (and he did mean in length, not cross section) braces were superior. I always thought he coined the term.

There was an old issue of American Lutherie with an article with 3 or 4 guys (Dana Bourgeois was one) giving their theories about scalloped braces and they also interviewed that guy about his work. I can never seem to find that issue though so if anyone knows it, I'd be curious to read it again just for kicks.

edit: Seems he's still around http://www.vanlingeguitars.com/index.html
Author:  Rod True [ Thu Jan 22, 2009 11:06 pm ]
Post subject:  Re: Parabolic Bracing?
Kent,

Scott was a member here a couple of years ago, but he decided that his offerings (opinions, thoughts, musings, theories etc...) were challenged to much and he deleted every post he made in what was a great thread on bracing theories. It was after that, that we all lost the ability to edit our posts, till the new software came along.

Scott can be found on at least one other forum (although not there often) and he responds well to emails. He loves talking about his ideas and what he's been able to accomplish with some instruments that were some what "dead" when he first heard them. His customers are happy and that's the true measure of success.

It would really be very very very difficult to create a true parabola running the length of the brace as it's generally only 5/8" (at most) high yet 18-20" long. Calling it an arc is more accurate than a parabola. That's my opinion anyway. The wording misrepresents the geometry.
Author:  Mike OMelia [ Thu Jan 22, 2009 11:16 pm ]
Post subject:  Re: Parabolic Bracing?
You are correct Rod. I think logarithmic might come closer given the initial (typical) height of a brace. Parabolic (true) should result in holes in the top.

I think I am hereby copyrighting the term "logarithmic bracing."

Mike :D
Author:  WaddyThomson [ Thu Jan 22, 2009 11:18 pm ]
Post subject:  Re: Parabolic Bracing?
Yeah, but it sounds scientific! :D
Author:  Mike OMelia [ Thu Jan 22, 2009 11:24 pm ]
Post subject:  Re: Parabolic Bracing?
Please contact my lawyer(s) should you want to license the use of logarithmic bracing (log bracing) in your new designs.

My licensing fees are very reasonable. I may even try this on my next guitar.

Mike
Author:  Pat Foster [ Thu Jan 22, 2009 11:46 pm ]
Post subject:  Re: Parabolic Bracing?
Mike O'Melia wrote:
Please contact my lawyer(s) should you want to license the use of logarithmic bracing (log bracing) in your new designs.

My licensing fees are very reasonable. I may even try this on my next guitar.

Mike


Too late. Eat Drink

Attachment:
log.jpg
Author:  Kent Chasson [ Fri Jan 23, 2009 2:50 am ]
Post subject:  Re: Parabolic Bracing?
Rod True wrote:
Kent,

Scott was a member here a couple of years ago, but he decided that his offerings (opinions, thoughts, musings, theories etc...) were challenged to much and he deleted every post he made in what was a great thread on bracing theories. It was after that, that we all lost the ability to edit our posts, till the new software came along.

Scott can be found on at least one other forum (although not there often) and he responds well to emails. He loves talking about his ideas and what he's been able to accomplish with some instruments that were some what "dead" when he first heard them. His customers are happy and that's the true measure of success.

It would really be very very very difficult to create a true parabola running the length of the brace as it's generally only 5/8" (at most) high yet 18-20" long. Calling it an arc is more accurate than a parabola. That's my opinion anyway. The wording misrepresents the geometry.


Thanks for filling me in. Hard to imagine people getting hot about something as trivial as bracing... ;)

And stop by next time you're south of the border. I need to remember to renew my blasted passport before I can head up that way.
Author:  Todd Rose [ Fri Jan 23, 2009 5:42 am ]
Post subject:  Re: Parabolic Bracing?
I think of the lengthwise brace shape I use as being very similar to the cross section profile of the surface of an archtop instrument. A very wide, low bell curve. The real difference, in my mind, between this and "scalloped" (not a particularly accurate term, either) bracing is the lack of peaks.
Author:  Michael Dale Payne [ Fri Jan 23, 2009 8:56 am ]
Post subject:  Re: Parabolic Bracing?
Rod True wrote:
No, the term parabolic is NOT incorrect.

It's looking at the cross section when calling it parabolic, not the run from x-brace intersection to termination point at the edge.

Attachment:
bracing cross section.jpg


Look at many pictures of scalloped braces, they are not parabola shaped but more triangular.

Some bad factory guitars are actually rectangular in cross section, even if they taper from the x-brace intersection to the termination point.



BINGO Rod is dead on here [:Y:]
Author:  Kent Chasson [ Fri Jan 23, 2009 10:44 am ]
Post subject:  Re: Parabolic Bracing?
Yes but Van Linge clearly means both cross section and profile, whether or not it's a true parabola. Maybe the meaning has changed over the years but he's been using that term for a long time.

As for the cross section, if the goal is strength to weight ratio, paraboloidish-like falls well short compared to triangular or a shape like an inverted T.
Author:  Joe Sabin [ Fri Jan 23, 2009 11:00 am ]
Post subject:  Re: Parabolic Bracing?
From my time making my own telescope mirror, I learned that a sufficiently small section of a parabola is measurably indistinct from a segment of a circle. Therefore a curve on a guitar that is spherical in nature would approach parabolic within a small fraction of a wavelength of light. Thus it would be entirely impossible to determine, using woodworking tools, if you got it parabolic or spherical.

Astronomy, another interest of mine.
Author:  Brock Poling [ Fri Jan 23, 2009 11:02 am ]
Post subject:  Re: Parabolic Bracing?
Todd Stock wrote:
To be accurate, you'd probably want to call it something like Semi-Conic or HyperEllipsoParabolic Bracing, as it's doubtful anyone can maintain a consistent parabolic shape without CNC, so a blend of conics and non-conics. Brush off the high school (junior high if under age 30) math to understand why this is so.

Almost sounds like there's real science or engineering behind this stuff when we use a name like 'parabolic bracing' in our ad copy, which is not the case.


How about Polytoric?
Author:  Michael Dale Payne [ Fri Jan 23, 2009 11:24 am ]
Post subject:  Re: Parabolic Bracing?
Most builder/luthiers tht claim to use parabolic bracing are referring to both cross-section and longitudinal profile. In truth few if any are truly parabolic in either plane, but are reasonable facsimiles of a parabolic shape. In my line of thinking is that sharp edges create stress risers curved reduce them. This is one tangible attribute of a so called parabolic cross-section and why I use it. Now with my limited knowledge base a parabolic profile provides a brace that is more predictability graduated as the brace gets taller than a shaved V cross-section on a given incline. I can’t say one is better than the other. I personally do not try to create a parabolic profile. I roughly taper my braces as experience has taught me then shave the cross-section into a near parabolic form. I believe I can build lighter, some what thinner tops with this method. It works for me. But all I claim is that my braces are near parabolic in cross-section. Not necessarily in profile.
Author:  Howard Klepper [ Fri Jan 23, 2009 12:27 pm ]
Post subject:  Re: Parabolic Bracing?
The most impressive way to describe one's braces would of course be hyperbolic.
Author:  SteveSmith [ Fri Jan 23, 2009 1:11 pm ]
Post subject:  Re: Parabolic Bracing?
Perhaps the cross in the x-brace could become a hyperbolic paraboloid? (insert tongue-in-cheek emoticon here)
Author:  Hesh [ Fri Jan 23, 2009 1:15 pm ]
Post subject:  Re: Parabolic Bracing?
Or perhaps hypersonic pseudo parabolic (HPP) :D
Author:  Rob Lak [ Fri Jan 23, 2009 2:12 pm ]
Post subject:  Re: Parabolic Bracing?
What was the question again?
Author:  Michael Dale Payne [ Fri Jan 23, 2009 2:18 pm ]
Post subject:  Re: Parabolic Bracing?
Also if you are banking on self promotional advertizing about using parabolic bracing as your magic bullet sales strategy…….Well this thread may make you a tad hypertensive
Author:  JJ Donohue [ Fri Jan 23, 2009 2:43 pm ]
Post subject:  Re: Parabolic Bracing?
It's actually psychobolic!
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