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So I've been attempting to find information and plans of the Martin made Ditson dreadnought ukes of the teens and twenties to no avail and thought maybe it might be possible to take a photo of an original instrument and convert that into a relatively accurate set of drawings. My only problem with that is I have little understanding of how to do much more than google things or record bad songs on garage band in regard to computers. I was wondering if anyone might be able to help me figure out how to convert a photo like this into a useable drawing when the only dimensions I know of it are the scale length of 13.614" and sound hole width of 1.75"

Download a free vector graphics program called Inkscape (very similar to Adobe Illustrator). Go to File->Document Properties and set "default units" to inches, so the rulers along the edges and cursor position shown in the bottom right corner on the status bar will be in inches (of course you can also use mm if you prefer). Drag and drop the photo file from windows explorer, and rotate and scale until it's the right size (make sure you scale uniformly by holding ctrl while dragging the handles). You can also use Object->Transform to scale numerically.

Then trace it using the tool "draw bezier curves" (keyboard shortcut shift-F6) and "edit paths" (shortcut F2), and Object->Fill and Stroke to edit the line width and color (set fill to none if it isn't already). When editing nodes, clicking on them while holding various combos of ctrl, alt and shift does different things. Just fiddle around with it until you get the hang of it.

Most guitar shapes can be produced with 8 nodes (two each for widest point of the shoulders, narrowest point of the waist, and widest point of the lower bout, and one each for top center and bottom center) and the node handles all going straight up/down/left/right. Hold ctrl while dragging a node handle to snap the angle.

You might be able to fit just the body on standard printer paper, but if you want to do the whole thing you can save to a thumb drive as PDF and take it to Kinko's or similar to get it printed. Since all the positions are in real-world units, it should come out just right. The File->Document Properties window also lets you set the page size shown in the editor, which is helpful to see if everything will fit on whatever size paper the print shop has.

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Ed

One way you could do it would be to print it out on graph paper. Then by scaling the known dimension you could determine the "size" of each block on the graph paper. One thing to keep in mind is that most photos have some distortion and may not be accurate in all dimensions.

I do that all of the time. I made a Gofriller viola from photos on line, designed a Gagliano viola as the link between a photo of a Gagliano violin and cello. I made a 1/2 scale 5 string guitar based on a Stradivarius guitar from photos.

Print out the photos, and figure out the scale. Use a compass and find the radii and center points of all of the outside curves. Get a piece of paper, I like Bristol paper; it's nice and thick; but guitar sized 18 X 24 in sketch paper is fine. Draw a centerline, and cross lines for length, and centers of bouts, and the soundhole and bridge, and start spinning the arcs with the compass in the right scale, and see what happens. You will probably have to adjust everything.

As Clay said, photos are rarely without distortion. But your dimensions, in width, and length, and placement SHOULD have some sort of geometric ratios that make sense. Classic designs are classic because of their framework. The width is related to the length. The widest part is so far down. The narrowest part is so far up from the widest part. Common ratios are phi? .618 it is in between 5/8 and 3/5, also common ratios used. .577 or as they would have found it tan 30, is another. There are many more, usually very simple 1/3, 2/3, 2/5, that sort of thing.

Play around with it and see what comes out. I found those ratios when I drew out the Archtop I'm building now.

I've used computers to draw violins out. I use Auto Cad at work, and had it on a computer at home for a while. It isn't as much fun, and you don't have the same learning experience. Some people like them. You do have a digital backup, and you can click on points to find dimensions; but you can take your drawing to Staples, and have a working drawing printed out, and have it saved as a pdf that you can file away in your computer.

Just a low tech solution.

I have NO IDEA what those penciled circles are around the outside. OH! I remember. I was making up a set of spool clamps for gluing, and wondered how many I needed!

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Why be normal?

Several good suggestions, all basically the same process just different tools. The idea is to get that photo to scale and then trace. Whether you use paper or software.

Personally, I use Fusion 360. There are several tutorials on YouTube on how to do that. The basic idea is that you import the picture as an "Attached Canvas" and scale it with a known dimension. Fusion then scales the whole photo proportionally. The photo becomes a semi-transparent background attached to your drawing plane. From there you use the 2D drawing tools (called "Sketch") to draw over the lines in the photo you want. If you accurately trace the photo you will end up with a properly scaled and dimensioned technical drawing.

This is exactly what I do, complete with the trip to Kinkos ($2.55 per 18x24" print seems hard to beat). In my case I scanned my pencil and paper drawing (also at Kinkos), then traced it with the pen tool, anchors at the extremis of the upper, waist, lower. I only trace half the outline, copy, paste, and flip it to mirror it. The pen tool is the most difficult tool in Illustrator-type programs to use, but once you get the hang of it, you'll be golden.