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Is there an online website that will draw a radius of your choice?
I want to print out various radii ranging from 15', 16' 17',..to 25'. Just need a line the length of a piece of paper.

Hi David,

In this thread there were a few members that generated a radius diagram with their software and posted PDF files.
[url]http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=29337&p=390409&hilit=print+radius#p390409[\url]
Not sure if this helps - I searched online a while back and couldn't find a site where I could just generate a curve and print it - however the PDF's in the link gave me what I needed.

Rob

Tell me all the ones you need and trimmed to what length, I will send them to you in DXF, DWG, or JPG. I normally include an adjascent straight line so you can make sure your print out is aligned.

I use 60 foot, 30, 25, and 15, but can generate whatever you need.

While you are at it, could you answer my DVD inquiry?

I haven't tried this cad program yet, but I've heard good things about it on this forum. Is this what your looking for?
http://www.3ds.com/products/draftsight/draftsight-overview/

Another way that is very accurate, compared to what one most commonly sees is to draw line where the ends are at 0 height and the middle is at 100% height, across 8 divisions where the percent heights are as follows:

0, 41, 73.6, 93.4, 100, 93.4, 73.6, 41, 0

Then fair those points with a batten. Of course this requires knowing the height of your radial arcs for a given length, which is some trig. And it is easier to sketch. That said, one sees a lot of people using stuff like batten across a single point, or Somogui's bow. These all create parabolas. Not arcs of a circle.

Another cool trick which can be a jig, is to place two nails on a baseline, then a third in the center. Arrange two batten so they overlap the middle nail from both side, like a very flat tepee. Now fix the two batten were they overlap. Anywhere you move them, remove the center nail. Now anywhere you move them the inside corner will be on the arc. This can be used to draw lines or run a router.

Life would be easier if nobody had thought up this arc of the circle stuff, at least as far as the nomenclature is concerned. On boats, nobody says to make the deck an arc of 1300 feet or something. They just say make it .75" high at the widest point. Same thing here, it would all be simple if we just looked at the guitar at the widest point and decided to make it 1/16" high, or whatever. Who really knows what a 60 foot radius looks like off hand.

Here's a great website that explains a great way to layout an arc
http://liutaiomottola.com/formulae/sag.htm

Mark

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That's thorough. With the Sagita calculated, all my percentages above do is give you the other elevation heights, to fair accuracy by means of ratios.

For those who want to bend a batten, whether around nails or like a bow, all you need to do to get arcs is taper the batten from both ends. This is a process called tillering, about which there are doubtless endless youtube videos. With bows like tone, you are hitting a multi element target, but since we don't care about draw weight or arrow speed, all we care about is a nice arc, just side tapering the batten will work.

If you have access to simple cad, or maybe google sketchup, what you can do if find the circle function/button, on the toolbar. Normally this can be operated by mouse or entry, or both. Often the fastest way is to click the toolbar circle button; then click the mouse on the whitespace anywhere you want, then look for a radius entry field and insert your radius with the keypad; then push "enter". You should have a full size circle. If you highlight the circle the screen probably has a function indicating object size which is a useful check.

Navigate to the 12 oclcok position on the circle. Start another circle at 12 oclock, this one is the size you want the printout to be like 18".

Once it is drawn, look for "trims". This button should allow you to highlight the little circle, and then click on the outside portion of the big circle. All bu 18" of the arc will disappear. Add a straight line for reference.

With these simple techniques, and by adding to them "snaps" a function that allows you to precisely place objects, you can design any guitar body that is a series of circles.

Other useful buttons will be translational moves (precise way to move components around, can be used with snaps). And the tool that allows you to do complex curves, easily with multiple points. It's just like lego, you start with shapes and plug them together. Anytime you think something like " I wish I knew how to rotate parts" You can be sure the menu has a button for that too.

http://www.youtube.com/watch?v=Nr0OSxTHYIE&NR=1


Here it is on youtube. All cad programs including the free ones, will have something similar.

http://www.youtube.com/watch?v=Nr0OSxTHYIE&NR=1

The two point method is the one I described.

Three point method allows you to specify elevation, and baseline for a specific arc.

Another way that is very accurate, compared to what one most commonly sees is to draw line where the ends are at 0 height and the middle is at 100% height, across 8 divisions where the percent heights are as follows:

0, 41, 73.6, 93.4, 100, 93.4, 73.6, 41, 0

Then fair those points with a batten. Of course this requires knowing the height of your radial arcs for a given length

I need an 18', 40', 50' and 60' radiusthe length of a 8.5 x 11 paper is fine. Jpg prefered or pdf.

Thanks for all the great replies!

What is your question?

This should do it. Each radius has straight line with a curve above it. I haven't test printed so there is a 1" by 1" box in the lower right corner to make sure it's to proper scale.

CHECK SCALE BEFORE YOU YELL AT ME!!

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Here are files generated in Adobe Illustrator and saved as PDFs. The file is zipped.

Here's a link to another spreadsheet that was for radius dish building, but would work for you as well. http://homepage.ntlworld.com/coleman005/Curves.htm

Wow! Thanks guys. That helped out. You guys are fast!

Next I want to check out some fretboard radii. 20" is too much for a classical IMO. I'd like to see what a 30" and 40" radius looks like over a 2 1/2" distance. Can any of your programs calculate that?

I'm hoping to have someone make a custom fingerboard radiusing sanding block 8" long out of aluminum once I determine the radii I want. Any recommendations as to who could do that?

Yes Master.

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http://banduramaker.blogspot.com

Andy, Wow! You're awesome. Thanks.

Have you ever drafted a set of guitar plans?

No, I've never tried. What you've been asking is actually quite easy. 2D guitar plans wouldn't be all that difficult though I don't think. Just time consuming to make sure you didn't miss anything.

I'm actually rather a beginner at CAD (had a class about 20 years ago in school) but am currently trying to build a 3D model of a Bandura - the primary instrument I make (although I have made a few guits too). You can read about my struggles here: viewtopic.php?f=10106&t=30598

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Is there a program that can scan my hand drawn plans and convert them into cad?

For example, say I have the traced outline of a guitar drawn on a piece of paper. I want the exact 1:1 size and shape. Then I want to add the bracing dimensions and locations, etc...

Obviously I'm a newbie at computer drafting or what ever it is called. THe less complecated the better .

Best way I've found is to scan your tracing, or take a good straight on photo of it (use a zoom lens to reduce lens distortion), and then import it into your cad program and "trace" over it in cad. That's what I do with Autocad, anyway. You can use a "spline" command to make a smooth curved line.

Since you probably don't have a large format scanner, you can scan different overlapping portions of your tracing and sort of reposition and reassemble them in your cad program before you digitally trace them. It helps to have a bold straight reference line on your sketch (like the centerline of the body tracing), because you can use that to precisely align and scale your jpg in cad. Hope that makes sense.

There are programs that will convert "raster" images (photo, jpg) to "vector" (cad, dxf), but the cad information won't be that great. Instead of smooth curves you'll have a series of short line segments, a lot of times. This would still also require you to have a large format scanner of some sort.

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Jonathan Kendall, Siloam Springs AR