If you would like to make the original type of shell, but not sure how to start you can use the tool below to help you choose the parameters to use to make a shell with the shape you'd like. This tool shows the cross-section as if you cut the shell down the middle to make two halves. The pink / red points are movable to adjust either the bevel angle of your saw, or the angle of your wedges. Other items with a pink dot are movable to rearrange, and you can also click and drag the text or attached image around.
This tool will also model the curve you'll get with a propped-up wedge. This will allow you to make a shell that grows faster in height than it does in width resulting in a narrower shell. The bevel angle in the outermost part of the shell will be greater than the bevel angle along the left and right sides of the shell. Watch this video for a demonstration of the effect. This tool is only 2-dimensional and does not model the width of the shell.
The image export function of this web app does not work, but you can make a screen shot to save the information. More tips and information below.
Image of actual nautilus half provided by Wolfgang Grulke, author of Nautilus Beautiful Survivor. Get his book here.
1. Click the button in the bottom left corner to make the app full-screen. Press escape to exit full screen.
2. The background color can be changed by clicking the 3 bars in top right corner, then settings, circle / triangle icon below the gear.
3. If your wedges do not taper to a sharp edge you can model the effect to see how big the hole is through the center. Remember to keep the thin edges aligned while tracing the next segment, and also while gluing them together.
4. Adjust the wedge angle to match the angle of the wood wedges you will use. If you are bevel ripping a 2x4 to make wedges, your wedge angle will be around 18°.
5. Adjust the bevel angle keeping the point to the right of the thick edge of the wedges. Move it until you get the desired cross-section shape. The correct bevel will be shown to obtain that shape. Note that if you change the wedge angle again, it will change the shape somewhat.
6. Scale doesn't affect the shape of the cross-section, but you can change it if you'd like in order to get dimensions of your shell you're designing. Move the pink / red dot at the thick end of the largest wedge, and use the 2 ruler points to measure from the thick edge and the edge of the hole - or center point if using sharp-edge wedges. Drag the point to match your wedge width (assuming you plan to use the entire width). Now you can use the ruler points to measure the rough size of the shell.
7. You can also use this tool to figure parameters for a shell in an image. Drag the center of the spiral in the photo over the center of the model (might need to zoom out to see it) and then drag the point for wedge width onto the edge of the spiral. You can resize and rotate the image using the two points on the edge of the image. Now adjust the bevel point until the model matches the image. You might need to move the image around to get the best fit as few spirals are perfect. The web app doesn't allow you to upload your own image, but you can send it to me by email and I can place the image in the model for you.
8. Have fun! I hope you enjoy playing around with it. Check back soon because I plan on making more models.