Acoustic Guitar Shapes

[Rcnewcomb]

It isn't a full-blown gadget, just a LUA script. I took basic measurements of various acoustic guitar body shapes and set up the LUA script to create the bezier curves using ratios or percentages. This allowed me to experiment with the shapes using more of a mathematical approach.

It assumes the project is 24x24 with the XY datum position in the center of the material. It is set up to do one body design, but I have other shapes in the comment section.
To run the script:
1. Open a new project 24x24x0.5 with the XY datum position in the center of the material
2. open the LUA script using Notepad or Notepad++, or some other script editor
3. In Notepad Select all the text of the LUA script using Edit/Select All or <ctrl>A
4. In VCarve or Aspire select Edit/Paste or <ctrl>V

I've attached a ZIP file with the LUA script and a CRV job with 5 different shapes with the associated molds, forms, and spreaders for the waist and upper and lower bouts.

[PaulRowntree]

Thanks Randall!

[sylvan356]

I can't wait to see what you have done! Thanks!!!

[sylvan356]

Randall -
I have tried to use the VCarve file and am able to see all of the work you did there. Terrific! However, I want to use the Lua script. When I follow your instructions I get in the program exactly what you posted - what appears to be a jumbo shape. How do I modify the Lua script to look at, and possibly modify, the other shapes? I tried removing the two dashes (comments) to make them active and deleted what appears to be the Jumbo instructions but when I copy and paste that (without the Jumbo) into Aspire I get nothing. Obviously I am deleting something important. I would really appreciate any help you can give me! Thanks!
Sylvan

[Rcnewcomb]

I've attached examples where I've commented out the Jumbo and uncommented either the Dreadnought or the Gibson L-0

[mikeacg]

Randall,

Can't wait to look at this! Thanks for sharing!

Mike

[sylvan356]

Randall
Thanks!!!!

[hooked]

Thanks Randall,

I will have a play. If you are interested in guitar design this may be of use http://liutaiomottola.com/formulae/gthang.htm

Cheers

Daryl

[Rcnewcomb]

Daryl,
I haven't used that tool, but I definitely use that site for calculating neck resets.

[hooked]

Randall,

We may have a similar interest other than CNC. I make small guitars. http://www.darylhooke.com/pu/gallery/

[StefanK]

I just stumbled on this. Thanks! it looks very handy.

[Rcnewcomb]

Currently on my bench....

[litzluth]

Hi Randall,.
I just tried a new technique I like. (My backstrips aren't the full thickness of the back though, only about 1.3 mm).
I routed a 15 mm wide slot for the internal brace for the back splice. .3mm deep. That's just deep enough to ensure it won't move under gluing pressure, and a 15 mm wide brace will stay perfectly aligned and perpendicular.
Then I routed mortises for the splice brace in the 4 back braces and glued them in.
Best,
Mike

[adze_cnc]

I was looking for a project to implement some ideas I had for a new "VCarve / Engraving Toolpath" last pass option gadget that I am thinking of writing. I stumbled across Randall's guitar profile Lua drawer above and thought that it might be a good one to play with.

As with Randall's original Lua script this is a not a full-fledged gadget. Running it follows pretty much as described above. Load into editor. Copy all text. Paste into VCarve / Aspire.

To change which guitar profile to draw is a little different but with hope a much easier task. At the bottom of the file is a list of guitars available:

Code: Select all

   -- dreadnought:drawshape(layer)
   -- j45:drawshape(layer)
   -- om:drawshape(layer)
   -- gibsonl10:drawshape(layer)
   -- l00:drawshape(layer)
   -- m:drawshape(layer)
   -- size5:drawshape(layer)
   -- sj:drawshape(layer)
   jumbo:drawshape(layer)

Just remove the comment—two hyphens—from one (or more!) guitar that you wish to draw. Put a comment in front of ones you don't want to draw. For example:

Code: Select all

   -- m:drawshape(layer)
   size5:drawshape(layer)
   -- sj:drawshape(layer)
   jumbo:drawshape(layer)

Will draw both the Jumbo and Size 5.

To add a new guitar is fairly simple. Look in the function "initGuitars()". Copy one of the definitions there. Give it a new identifier. Then add a line to draw the shape in the list above.

For example say we want to add a Taylor LKSM Leo Kottke Signature 12-String just copy one of the other guitars (say dreadnought) and alter parameters:

Code: Select all

   lksm = Guitar:new({
      Name = "Taylor Leo Kottke Signature 12-string", Units = "i",
      ... fill out the rest ...
      upper_bout_to_neck_ctrl2x = -0.67, upper_bout_to_neck_ctrl2y = 0
   })

And then add:

Code: Select all

   -- sj:drawshape(layer)
   -- jumbo:drawshape(layer)
   lksm:drawshape(layer)

I hope this is useful.

Steven

[Rcnewcomb]

Thanks for the update Steven!