Colby,
Have a look here on Scott Van Linge's website: Parabolic Bracing
I don't think the bracing pattern should be any different just the shape. This is my take on "parabolic" using my normal bracing pattern :
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| Author: | Colby Horton [ Thu Oct 13, 2005 12:15 am ] |
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Does anybody have some pictures or dimensions of a parabolic braced top? I have built guitars with both parabolic bracing and scalloped bracing. Out of the two I like the scalloped braced better. I think it maybe because the parabolic braced one is two strong or two tight. If anyone has some info on the placement and dimensions I would appreciate it. |
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| Author: | Dave White [ Thu Oct 13, 2005 12:26 am ] |
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Colby, Have a look here on Scott Van Linge's website: Parabolic Bracing I don't think the bracing pattern should be any different just the shape. This is my take on "parabolic" using my normal bracing pattern :
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| Author: | Colby Horton [ Thu Oct 13, 2005 12:42 am ] |
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Thanks Dave! Have you finished that guitar yet? If so how did it sound? |
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| Author: | Dave White [ Thu Oct 13, 2005 1:04 am ] |
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[QUOTE=Colby Horton] Thanks Dave! Have you finished that guitar yet? If so how did it sound? [/QUOTE] Colby, That particular one is still being made, but I have used the same parabolic bracing on my last 3 guitars and I am a big fan. I get the best tap tone from this shaping and can tune each brace and the system a lot easier. The guitars from first stringing sound really open - like my other guitars did after a month or so, and the strings sound a little more balanced. The bracing really suits the guitars I make and helps me get the sound I am aiming for - strong projection and sustain, clear fundementals but with complex overtones and good for open tunings. One one guitar I tried making the bridge more parabolic in profile too. It could also be that my building skills are getting better as I keep building - I am using much lighter bracing in terms of height - and I have never really used scalloped bracing as to me they look unnatural and not very graceful. This was the sort of bracing profile I used previously: 
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| Author: | csullivan [ Thu Oct 13, 2005 3:58 am ] |
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Dave, Nice, clean bracing. You seem to have a clear idea of how to control and tweak the braces to attain the sound you're looking for. I'm curious as to how thick that top is in your first post? It may just be the photo, but it looks thicker than most. Do you graduate the perimeter once the sound box is complete? Tuning plates is becoming an obsession for me and I want to hear as many approaches as I can. Craig |
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| Author: | Dave White [ Thu Oct 13, 2005 4:39 am ] |
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Craig, I probably do my tops thicker than most - especially in the middle - as I think this helps with trebles. But I do leave it thicker and when the box is joined, before binding, I thin it down, particularly towards the edges and at the back of the lower bout. This also gives leaway to take out the dings that seem to appear on Euro Spruce no matter how careful you are! I would say that in the centre (and bridge area) my tops are around 3 - 3.2mm thick coming down to between 2 - 2.5mm at the edges, depending on the stiffness and "sound" of the top. I wouldn't say my tuning is remotely scientific, but there are certain things that I am listening for and alter braces until I get. One is the overall "ping" I hear - a bit like tuning a bhodran, and appropriate as my tops have a lot of arch. Secondly is a sort of "pop" when you hit on the bridge plate, and if you leave your finger on you feel the top "kick back". Also after reading and discussing with Scott Van Linge his Sound is Round theory, I have started tappimg along the length of all of the braces listening and feeling carefully for responsiveness, changes and sound. Sometimes I hit a falling off or deader spot, and then I shave/sand off some brace material until it comes back up again. I suppose I am trying to "tune" the braces to get as aven a response as possible all over. This is only tuning in the raw, and when attached to the rest of the box, and more importantly when under string tension, this may change. Since doing this process and using "parabolic" I have noticed that my tops have been a lot more open and "responsive" from first stringing. Could all be Spiritual Hokum of course! But I find it a very relaxing and satisfying process to go through. The one fascinating thing I have noticed is the importance of the top - upper bout brace - which apart from the finger braces is the last one I put on. The tap tone of the lower bout improves "immensely" when this brace goes on. I don't believe that the upper bout section of the guitar is an acoustically "dead spot". |
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| Author: | Sprockett [ Thu Oct 13, 2005 4:49 am ] |
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Here are a couple that I braced: 
This is a Koa one that I did, the top is spruce and that's pretty much my standard bracing style. This one is owned by a guy who plays in a local church and has probably the most balanced sound of all my guitars. 
This is a fanned fret I delivered not too long ago, same dimensions with some mods for the shifted bridge. It has a nice bright tone, it's not very loud but has what I would call a delicate sound. The top is adirondack as is the bracing. For my X-Braces I use .010 Carbon Fiber laminated in with long cure epoxy, I don't remember the exact dimensions (I have a little black book with the numbers in it) but I know they are a little over 1/4" wide and pretty tall (under 3/4" for sure), I try to keep the contact area on the top as minimal as I can. They are fully curved from the X-Joint down to the scallops at the end (which are 1/8" high and sit 3/4" proud of the kerfing), the scallops are set so that enough of the flat part sits outside the kerfing to allow the top to vibrate off of them. Hope that helps... -Paul- |
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| Author: | Josh H [ Thu Oct 13, 2005 11:05 pm ] |
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Dave That is a mighty tight X brace you got going on your tops. That looks tighter than 90 degrees if I am looking at it right. Do you know what the angle it is? I've been thinking about the angle of the X brace over the past few days. Most of the recent ones I have done have been at 90, but I have decided to go a little wider on the one I am doing now. I hope to get most of the top braced today so I will post a pic if I get it done. Josh |
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| Author: | GregG [ Thu Oct 13, 2005 11:32 pm ] |
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Hi Colby, Sorry no pictures for you as I did not have access to a digital camera when I made my first guitar. I did a lot of research before building though and decided on parabolic bracing....the guitar sounds fantastic, better than I could have hoped for. I spoke to Scott Van Linge via email before the build and he was kind enough to send me some info on parabolic bracing....might want to email him and see what you come up with. I believe that my first guitar, a parabolic braced one, is in the top 5 of all of the guitars I've played or heard so heck I'm sticking with it that's for sure! I'll document my next build with pictures to show my version of parabolic bracing anyway. Greg |
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| Author: | Dave White [ Thu Oct 13, 2005 11:37 pm ] |
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[QUOTE=Josh H] Dave That is a mighty tight X brace you got going on your tops. That looks tighter than 90 degrees if I am looking at it right. Do you know what the angle it is? I've been thinking about the angle of the X brace over the past few days. Most of the recent ones I have done have been at 90, but I have decided to go a little wider on the one I am doing now. I hope to get most of the top braced today so I will post a pic if I get it done. Josh[/QUOTE] Josh, The X brace angle is about 78 degrees. Before I started building I had a good look at the bracing of guitars whose sound I really liked and admired, and this angle came from one of Stefan Sobell's guitars that I looked at. I also like the way the top of the X braces lock into the upper bout brace. Another thing I like is that the outer strings on the saddle are positioned on the X brace arms - for both my guitars and guitar bouzoukis - and I suspect that as well as tensioning the tops the X braces also are part of the vibration distrinution of the top. My topes arch a lot laterally and I find that having this tight X brace angle gives more flatness in the bridge area and lets the arch fall away to the sides. I know that "conventional wisdom" is to have a wide X brace and big area in the lower part of the bout between the X legs where the bridge plate is. Perhaps someone here can educate me to the science behind this. |
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| Author: | Josh H [ Fri Oct 14, 2005 3:06 am ] |
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Dave Some interesting ideas you have going. I noticed that your X brace locks into the upper bout brace like you mentioned. Haven't seen that before, but it is interesting. You are using a pinless bridge on all your instruments aren't you? You couldn't use a tight X like that with a pinned bridge or you would run into problems. Thanks for sharing the pictures. I am getting the feeling that I brace my tops considerably lighter than a lot of the guys around here. It's hard to tell exactly how big the braces are from pictures, but I think I'm seeing a lot more wood on some of the tops than what I put on mine. I will try and get a picture up later today or tomorrow and you guys can give me some opinions. Josh |
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| Author: | Howard Klepper [ Fri Oct 14, 2005 5:40 am ] |
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So is the parabola supposed to be the cross-sectional shape, or the shape when looked at from end to end in the plane of the top? And does anyone actually use a quadratic equation to plot a parabola, or is parabola a nice techie sounding word that really just means some kind of curve that's higher somewhere near the middle than it is on the ends? I once asked Scott on another thread somewhere if he had the equations for his parabolas. He ignored the question. |
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| Author: | Don Williams [ Fri Oct 14, 2005 5:46 am ] |
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Parabolic bracing is supposed to refer to the general shape of the cross-section of the brace, not how it is shaped end to end. Parabolic vs triangular or flat on top etc. Most people I know curve their braces downward in the middle not upward... I'm not sure that those braces wouldn't be way too stiff. Not ridiculing here, but just posing my thoughts on that. I know that there are folks who build with unusually tall bracing that get great sound though, so just maybe there are no hard and fast rules. It's a mystery! |
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| Author: | Brock Poling [ Fri Oct 14, 2005 5:54 am ] |
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So then... it would be possible to have parabolic AND scallopped in the same guitar? |
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| Author: | Josh H [ Fri Oct 14, 2005 5:57 am ] |
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Howard and others If all parabolic means is having braces curved on the top instead of flat (as Don said) than I guess those are the kind of braces I use. But I was carving my braces this way before I ever heard of parabolic braces. I just thought they looked better, not like many people will get to see them I guess. As far as an equation for carving them or anything like that. Nope, I carve them until I have removed the wood I think is necessary. Then I sand until everything is looking smooth and clean. I'm not really sure I know what I'm talking about when it comes to this whole parabolic bracing thing, but I don't think there is really anything magical about it. To me the bracing pattern and size of your braces have more effect than the shape of them. An interesting discussion though. Josh |
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| Author: | csullivan [ Fri Oct 14, 2005 6:14 am ] |
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As Alan C. explains it, the angle of the X can vary from guitar to guitar. It's a means of controlling the cross grain stiffness. A more open angle will give you greater stiffness, less angle reduces stiffness. That's why it's good to use on backs as well. It allows more control when matching the plates. If I have mis-quoted you in any way Al, I apologize. Craig |
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| Author: | Dave White [ Fri Oct 14, 2005 6:23 am ] |
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[QUOTE=Howard Klepper] So is the parabola supposed to be the cross-sectional shape, or the shape when looked at from end to end in the plane of the top? And does anyone actually use a quadratic equation to plot a parabola, or is parabola a nice techie sounding word that really just means some kind of curve that's higher somewhere near the middle than it is on the ends? I once asked Scott on another thread somewhere if he had the equations for his parabolas. He ignored the question.[/QUOTE] Howard, And are "spherical tops" supposed to be perfectly spherical? Do scalloped braces retreat into their shells underwater? Or do George Lowden's "porpoise" shaped braces follow ships? What is your point? Or your apex? The braces are not perfect parabolas either in cross section or lengthwise but it is a reasonable visual aide memoire description. OK from now on I'll refer to it as "parabolic'ish bracing". By the way, parabolas are very interesting: " A parabola may also be characterized as a conic section with an eccentricity of 1" I'm all for eccentrics. "A parabola spun about this axis in three dimensions traces out a shape known as a paraboloid of revolution." This is probably what John Lennon was trying to desribe circa 1968. "In polar coordinates, a parabola with the focus at the origin and the top on the negative x-axis, is given by the equation r(1-cos(theta))=l where l is the semi-latus rectum: the distance from the focus to the parabola itself, measured along a line perpendicular to the axis. Note that this is twice the distance to the top." Don't know what this means but it could be related to Brad's new creation, and it does mention the word top. By the way that was a fabulously stunning and interesting guitar you posted on the MIMF. If you have any I'd love to see photos of your adjustable neck joint construction. |
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| Author: | Dave White [ Fri Oct 14, 2005 6:31 am ] |
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[QUOTE=Don Williams] Parabolic bracing is supposed to refer to the general shape of the cross-section of the brace, not how it is shaped end to end. Parabolic vs triangular or flat on top etc. [/QUOTE] Don/Brad, What I understand as parabolic bracing is not just the cross section but also the end to end shape. You could have braces that were parabolic cross section and scalloped, but these wouldn't be parabolic "as we know it Jim" or as I know it. |
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| Author: | Dave White [ Fri Oct 14, 2005 6:33 am ] |
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[QUOTE=csullivan] As Alan C. explains it, the angle of the X can vary from guitar to guitar. It's a means of controlling the cross grain stiffness. A more open angle will give you greater stiffness, less angle reduces stiffness. That's why it's good to use on backs as well. It allows more control when matching the plates. If I have mis-quoted you in any way Al, I apologize. Craig[/QUOTE] Craig, Thanks that's interesting. My tops are highly arched which brings stiffness - or at least tightening like a drum - so perhaps my tight X brace makes sense as a balancing thing. |
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| Author: | Howard Klepper [ Fri Oct 14, 2005 6:45 am ] |
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Dave: that obfuscation is rampant is not a reason not to eschew obfuscation. Or perhaps I should start saying that the curve to which I arch my tops is a piecewise-cubic polynomial with second-order continuity and second derivative zero at the ends. That would have the advantage over "parabolic" bracing of being actually true. Nonetheless, I fearlessly eschew it; after all it's just a spline curve. Thanks for the compliment! I like your work, too! |
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| Author: | Dave White [ Fri Oct 14, 2005 7:44 am ] |
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[QUOTE=Howard Klepper] Dave: that obfuscation is rampant is not a reason not to eschew obfuscation. Or perhaps I should start saying that the curve to which I arch my tops is a piecewise-cubic polynomial with second-order continuity and second derivative zero at the ends. That would have the advantage over "parabolic" bracing of being actually true. Nonetheless, I fearlessly eschew it; after all it's just a spline curve. Thanks for the compliment! I like your work, too![/QUOTE] Howard, Apex taken. I bet if George Bush made guitars, he'd use carbolic bracing. |
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