Replies

1. 
   saschafer | Sep 05, 2007 08:12pm | #1

   Do you want true elliptical curves (that is, curves that conform to the mathematical definition of an ellipse) or just smooth, ellipse-like curves? How big do you need? Assuming you're talking about true ellipses, how much of the ellipse do you want?

   Are you aware of the string-and-two-nails approach? That's about as easy as you can get, but it assumes that you have enough room to work in (hence the questions above).

   Incidentally, ships' curves (batten-based methods in general) result in curves that are approximately cubic splines, rather than ellipses.

   -Steve

    

   
   

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   Edited 9/5/2007 1:14 pm ET by saschafer

1. 
   Bioman | Sep 05, 2007 08:32pm | #2

   I have used both at different times, so the answer would be both, but these have been art store templates.  The issue that I have is that when making larger sized conceptual drawings or actually laying out the shape full length on for instance a mirror; I am limited by the small templates I own.  I need to be able to make plywood/hardboard templates that can vary in length from several feet and up.  So far the only thing I have seen is the Rockler jig (which would need to be adapted), but would like to avoid the $80.00 cost as my usage is occasional. 

1. 
   saschafer | Sep 05, 2007 08:57pm | #4

   If the goal is to make a template, then one of the jigs is probably the best approach. Otherwise, you'll have a bunch of sanding to do.

   -Steve

    

2. 
   [email protected] | Sep 05, 2007 09:57pm | #5

   You could just lay out one axis and the center, then measure out, calc the distance out to the ellipse from the axis, and plot that point.  Do this for a series of points and then use your ships curves to connect the dots. 

   Kind of a pain, but it does work every time. 

   With a spread sheet it is pretty to easy to develop a table of coordinates.  The equations you would need are available online.  Just google ellipse. 

2. 
   mvflaim | Sep 05, 2007 08:47pm | #3

   Theres a method of drawing an ellipse by taking a stick and driving three nails into it.  Drive the first nail in one end of a stick and determine how long you want your ellipse to be and drive the second nail into the stick so that it's half the total length of the ellipse from the first nail. Then take the third nail and drive it into the stick so that it's distance between it and the first nail is half the total width of the ellipse.

   Take the stick over to your work piece and lay a framing square in the center of the work piece. Take your stick and run the two nails closest to each other along the rim of the framing square (one nail on the Y axis of the square and the other nail on the X axis of the square). The nail at the end the board (The first nail you drove) will scribe a quarter of an arc. Rotate the framing square 90 degrees to the first lay out line and repeat the scribe method. When you do all four sides you have the ellipse that you want.

   Obviously it's a lot easier to show you than write about it but hopefully you get the idea.

   mike

   
   

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   Edited 9/5/2007 1:54 pm ET by mvflaim

3. 
   Pondfish | Sep 05, 2007 11:35pm | #6

   Sometimes I just model the curve I want in a drafting program (I use designCAD) and then print it full size.  I transfer the curve to my stock or template, and cut to the line, smoothing with a spokeshave.

   There's a way to do it with a framing square and a stick, but it's a bit too complicated to describe--pictures really help.  Try a Goggle search on draw+ellipse+framing square.

   Recommending the use of "Hide Signatures" option under "My Preferences" since 2005
4. 
   GaryW | Sep 05, 2007 11:43pm | #7

   http://www.uwgb.edu/DutchS/MATHALGO/Ellipses.HTM

    

   Gary W

   gwwoodworking.com

1. 
   Bioman | Sep 06, 2007 01:25am | #8

   Thanks for the responses guys, now I have a place to start.

5. 
   Bioman | Sep 06, 2007 01:32am | #9

   PS, I just ran across this visual that realy pulls it all together.

   http://www.miterclamp.com/Woodworking_video_index.htm

1. 
   WillGeorge | Sep 07, 2007 03:39am | #11

   Thank You for this post.. I'll look at the videos later..Thanks again!

2. 
   KeithNewton | Sep 07, 2007 04:44am | #12

   Hi Bio, I couldn't watch that, but did it have a means to attach the router. I have a neat jig that I made about twenty years ago that I use a lot. It was made out of scrap P/W, and can be adapted for any size, and proportion ellipse that you need. Basically, it is a stack of various lengths of scrap plywood of the same width, with a T-slot cut down the length of each. Some have a T-cross-slot. I cut the leg of the T on the T-saw with a dado, and routed the wings with a router. After cutting the T-slot, I clamped them together in pairs with a key in the end to keep the slots lined up where they fit together. I ran the base of the router against the key, with a dovetail router bit in the router. THis allows me to use a butterfly key in the dovetailed ends of any parts that I choose to put together, or thus make a cross-track with the T-slot to any length that I wish to make.In the tracks, I made some UHMW slides that I screw through the trammel arms into a slide that rides in each of the cross-tracks. I usually just drill a hole in the end of the trammel arm to match a guide-bushing in the router, and normally use a 3/8 or 1/2" bit. After I fit the router to the t-arm, with the bit slightly out, I measure back for the screw holes that attach to the slides. Which by now I am sure that an ellipse has a long and short radius, so about all you need to know beyond this is that the length of the tracks needs to be as long as the short R subtracted from the long R. The skinnier and longer the ellipse, the longer the tracks need to be. All of the jigs that I have seen in the mags usually only show a single cross plate, which would only allow short fat ellipses. since my parts are snap-fit, I can change the track parts on the fly, so to speak. That is while I am cutting one side of the ellipse, I am using the parts on the opposite side of the jig, so the ones on the side I am working on are no longer there, because I have taken the off to get them out of the way. I will send you a photo of the parts if you email me. Sorry I have not published this before, I am pretty sure that I contacted FWW, but they probably thought it would be too advanced for the average woodworkers mind to comprehend. Hard to believe that after all of these years, I have not gotten one thing in this rag. HaWell, at any rate, I have demoed it several times back through the years to the local club when they have ask me to entertain them, so it is public domain now, so anyone can make it, and I don't expect anything for sharing something that I made for my own use. If you want to see some of the things that I have done, go to my website. http://www.treetales.com It opens to an elliptical column that is about 30" x 60" x 96" tall, and the trunk of the column has 1.5" of taper to each side as it comes up, so you can see that there had to be a bunch of patterns made when you consider that all of the shelves or stations, and moldings have a different pattern at each level. Working with ellipses is insane. Unlike a circle, each part has to sit and have its ends cut precisely where it was made for. You can't make a close cut, then adjust, and slide the parts around, because the curve is constantly changing. But it is fun if you like challenges.

1. 
   Bioman | Sep 07, 2007 03:26pm | #13

   Wow, I went to your site, very very impressive work Kieth!

    

   Yes the jig in the video was for a router.  The guy who did the video appears to be a finish carpenter, and the example he shows seems to be for a window or door transom.

1. 
   KeithNewton | Sep 07, 2007 04:58pm | #14

   Did you follow what I was describing for making the track parts? I don't have photos in my computer, and the jig is over at my nephews house right now, but I probably be over there this weekend.

1. 
   Bioman | Sep 07, 2007 05:27pm | #15

   Pictures would definitely help if that’s not too much of an imposition.

6. 
   flglide65 | Sep 06, 2007 02:08am | #10

   Figure out the length & width you want the ellipse to be, then draw an x-y axis. Go from the center of the axis 1/2 way to the end of the axis and drive a screw or nail. Do the same on the other end. Take a piece of string and go around both screws/nails with enough extra to make a triangle with the top of the triangle at the top of your X axis. Fasten a pencil at the same point and keep the string taunt while you draw around your ellipse.