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  #1  
Old 10-18-2020, 11:06 PM
Taylor Ham Taylor Ham is offline
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Default How do YOU draw up and make different body shapes?

Personally: I have tools like CAD, but using pencil, paper, ruler, and compass is the most satisfying to me. I'm self taught which may be evident. I don't have a french curve, since I like to achieve certain x-y measurements precisely. I just fit tangent arcs of specific radius and angular width that add up to my specs.

It took many iterations to find what looks right to me. I've arrived at a similar point to the classic L5 archtop shape, before it got stretched out to a tubby 17". And even now, 'thin slicing' still applies.

Here's my latest shape. I would have the upper bout a bit wider, but for this build I'm constrained by the existing GS mini overall widths.
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Old 10-19-2020, 05:04 AM
charles Tauber charles Tauber is offline
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Historically, I've used a pencil, eraser, ruler, triangle and thick card stock. I draw, freehand, on the thick card stock until I get the half-shape I want. I then cut that out with a sharp knife and trace around the half pattern to get the full shape. I have not found that French curves or a compass provides the curves that I want.

More recently, I have transferred the existing shapes to CAD for use in CNC operations. I don't often make new shapes, being happy with the shapes I iteratively came up with over a couple of decades.

In the course of developing those shapes, I experimented with a variety of things including golden ratio proportions and other regular shapes. I eventually concluded that the shapes that I wanted were more complex than simply a series of tangential arcs - more along the lines of bezier curves. I discovered that if one thinks of the outline as an elastic line that can be pulled up or down or side to side, one can create any guitar shape. For example, if one takes the point of maximum width of the upper bout, sliding it upwards gives one the typical shape of the upper bout of a dreadnaught; sliding it downward gives on a typical shape of a classical guitar. Ditto for the position of the waist and lower bout, as well as moving them laterally to make the shape wider or narrower.
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Old 10-19-2020, 08:19 AM
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IndianHillMike IndianHillMike is offline
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I can't remember if there's a name for it, but years ago I made a little tool to help draw my shapes...





Essentially just a flexible piece of plastic attached to a square piece of wood. In that photo I have the wood parallel to the center line of the guitar and at the widest point in the lower bout. The piece of scrap pushing against the plastic defines where the curve transitions from convex to concave and the curve "finishes" at the tangent point in the waist (parallel to the center line). All of those points can be moved around and I find I'm able to get very natural and smooth curves working this way. I've found that it's very difficult to transition from the constant radius of a circle to another type of curve without catching my eye and this helps eliminate that.
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Old 10-19-2020, 10:43 AM
Taylor Ham Taylor Ham is offline
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Quote:
Originally Posted by charles Tauber View Post
Historically, I've used a pencil, eraser, ruler, triangle and thick card stock. I draw, freehand, on the thick card stock until I get the half-shape I want. I then cut that out with a sharp knife and trace around the half pattern to get the full shape. I have not found that French curves or a compass provides the curves that I want.



More recently, I have transferred the existing shapes to CAD for use in CNC operations. I don't often make new shapes, being happy with the shapes I iteratively came up with over a couple of decades.



In the course of developing those shapes, I experimented with a variety of things including golden ratio proportions and other regular shapes. I eventually concluded that the shapes that I wanted were more complex than simply a series of tangential arcs - more along the lines of bezier curves. I discovered that if one thinks of the outline as an elastic line that can be pulled up or down or side to side, one can create any guitar shape. For example, if one takes the point of maximum width of the upper bout, sliding it upwards gives one the typical shape of the upper bout of a dreadnaught; sliding it downward gives on a typical shape of a classical guitar. Ditto for the position of the waist and lower bout, as well as moving them laterally to make the shape wider or narrower.


I definitely agree, because alot of my early iterations looked really angular and awkward. Back then I was using less arc segments so the transitions were sharper. I still like the precision of this style so I just made more steps to smooth out the tranisitons. Ideally I could use CAD to make totally smooth curves with infinite steps. But, it would be hard for me to the transfer that to a cardstock pattern. I'm happy with my current compromise given my relatively limited tools. It would have been so much easier just tracing an existing body.
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  #5  
Old 10-19-2020, 10:48 AM
Taylor Ham Taylor Ham is offline
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Quote:
Originally Posted by IndianHillMike View Post
I can't remember if there's a name for it, but years ago I made a little tool to help draw my shapes...











Essentially just a flexible piece of plastic attached to a square piece of wood. In that photo I have the wood parallel to the center line of the guitar and at the widest point in the lower bout. The piece of scrap pushing against the plastic defines where the curve transitions from convex to concave and the curve "finishes" at the tangent point in the waist (parallel to the center line). All of those points can be moved around and I find I'm able to get very natural and smooth curves working this way. I've found that it's very difficult to transition from the constant radius of a circle to another type of curve without catching my eye and this helps eliminate that.


Hi, I've seen your work on instagram and it looks excellent. I figure when I actually bend the sides, the way the wood bends takes care of slightly easing the transitions between the tangent lines and arcs. In fact, Since I bend free hand for now, most portions of the sides dont stay perfectly straight, besides beneath the neck join.
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Old 10-19-2020, 12:52 PM
Shuksan Shuksan is offline
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I've been using the Windows-based program G Thang written by R.M. Mottola specifically for designing acoustic guitar bodies. I've designed several guitars and an octave mandolin using it. It's actually fun to use. Using the program is pretty intuitive, but it has a well written manual that's very helpful.

Design files generated in G Thang can be exported to a drawing program and converted to pdf format. You can then take the pdf file to Kinkos and get it printed out at full scale to make plans and templates.

G Thang can be found here: https://www.liutaiomottola.com/formulae/gthang.htm

Example of output:

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Old 10-19-2020, 04:44 PM
Frank Ford Frank Ford is offline
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Here's a little piece on the classic boat builder's technique for generating smooth curves:

USING DRAFTING WEIGHTS
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Old 10-19-2020, 07:32 PM
rccosta rccosta is offline
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As insane as this sounds, I just trace the outline of a guitar body from an image online. I normalize the image to a known dimension (e.g., lower bout, upper bout) and go from there.
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  #9  
Old 10-20-2020, 11:24 AM
Alan Carruth Alan Carruth is offline
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That flexible stick is a 'spline'. It's an old technique.

Several years ago there was an article in the Violin Society journal about using bent sticks to draw out the curves of a violin. It's at least plausible that the old boys used some mathematical techniques, possibly based on things like the 'Golden Section', to determine the location of various points, such as the wide and narrow parts of the bouts, and used a bent stick to draw curves between those points. You can generate a very convincing 'Stradish' guitar shape that way, and its not so much different from a 12-fret Dread.

'Way back when I saw an article about using the product of circular and hyperbolic curves to generate guitar shapes. I wrote up a program (in BASIC) to do that, and have used it ever since to make up guitar shapes. The curves it makes are in the same class as the 'cubic splines' that you get from bendng a stick. I've showed the program to several other people (including R.M. Mottola) but nobody seems to be able to get the hang of it.

You can, of course, match any curve as closely as you want with circles and straight lines, if you use enough of them. That's how most of the guitar drawing programs work. A friend of mine included one such in the Android app he wrote, called 'Luthier Lab', which you can download free. It will save the shape as graphics file that you can get printed out full size at most copy shops. There's a whole lot of other good stuff in that app too.
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  #10  
Old 10-20-2020, 11:59 AM
H165 H165 is offline
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I experimented with a bunch of acoustic body silhouettes by drafting, using French curves, using math and radii, and freehanding half-shapes. In the long run I found I prefer shapes already existing. Right now it's the rather "curvy" shape of the old Harmony "figure 8" I like best. Ergonomics of these shapes can be altered with rests and wedging and body thickness.

Acoustics are really fun. Differences actually change the sound and ergonomicas significantly. There's no single goal, as conditions affecting the guitar, and the human body, change constanly.



With electrics, it's generally a gig or at least an amplified thing, so function can be extremely focused. I like a guitar I can play the whole gig without fatigue, which lets me easliy reach the high frets, which I can play comfortably, and which delivers the sounds I want. After 57 years of Duo-Sonics, Strats, Teles, Thinlines, Jazzmasters, 335s, 175s, 125s, Suhrs, PRSs, and Andersons, all that came down to the "less-known-but-better-for-me" Carvin (now Kiesel) 185 variants.


Last edited by H165; 10-20-2020 at 12:07 PM.
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  #11  
Old 10-20-2020, 03:27 PM
Rudy4 Rudy4 is offline
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Quote:
Originally Posted by Taylor Ham View Post
I definitely agree, because alot of my early iterations looked really angular and awkward. Back then I was using less arc segments so the transitions were sharper. I still like the precision of this style so I just made more steps to smooth out the tranisitons. Ideally I could use CAD to make totally smooth curves with infinite steps. But, it would be hard for me to the transfer that to a cardstock pattern. I'm happy with my current compromise given my relatively limited tools. It would have been so much easier just tracing an existing body.
It's usually easier to produce easily manipulated patterns in CAD using only a few points. It's even easier if you have a good idea of what you want to make with body length and waist and bout widths, then the shape practically draws itself. The body half-shape can then be instantly modified by grabbing a point of two and dragging. Once you have a pleasing half-shape it's a quick step to a full profile using the mirror command.

The thing I like about CAD is it's quick and easy to shift a body shape around until you have a design that pleases the eye.

CAD, of course, has a lot more going for it than just drawing body shapes. It's also easy to produce fret spacing templates and assemble newly designed instruments before ever cutting a piece of lumber. That can save a lot of trouble when you get a chance to visualize how neck angles, top arching, etc. is going to work (or not work...) in your finished work.

As far as transferring your drawn pattern to card stock goes, many CAD programs have a selectable "tile" feature that allows you to print on standard printer paper, cut the tile outlines and assemble your full size drawing.

I used to market specific full size instrument drawings and simply e-mailed a pdf to my local blueprint shop to have 100 large format copies ran off at a time. It's an option if you have a local shop you work with.

Last edited by Rudy4; 10-20-2020 at 03:41 PM.
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  #12  
Old 10-20-2020, 05:35 PM
Taylor Ham Taylor Ham is offline
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Thanks for the replies, I've considered some of those options. It's always interesting seeing the diversity of methods.
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