Est. 1998 — 27 years of woodworking knowledge
Plotting curves
David Barr
>How do you plot curves on your pieces of furniture? I'm quite the amature at this sort of thing and don't have a mentor to help me and I find this to be something of a problem for me. Simple curves I can figure out - just use a set of trammel points or even a compass and draw the curve. But what about complex curves say along the bottom of a table rail?
Re: Plotting curves
Bob Hackett
>The easiest way to get a smooth transition between two simple curves is to use a batten.
MB
Re: Plotting curves
William Duffield, on the Cohansey
>It depends on where you are and where you're trying to get to, and what tools you have to get you there. I use many different methods, depending on the curve, and depending on how many copies of it I have to make, and depending on whether I'm trying to reproduce someone else's art or creating my own.
Many years ago, I took courses in mechanical drawing, so I am proficient with compass, straightedge, dividers, circle and ellipse templates, french curves, ships curves, jar lids, etc. on paper, cardboard, velum and mylar. I also have a PC based graphics program (Deneba Software's Canvas) that draws lines, circles, arcs, spline curves, bezier curves, etc., and prints them out on paper. Sometimes I use a pencil and eraser on paper, by hand and eye. Sometimes I use a ballpoint pen and ROS on plywood, cut the pattern out on a bandsaw and refine it with a half round file or a drum sander. Some times I take a digital photo or scan a rough handdrawn sketch into my PC and use Canvas to draw and refine Bezier curves to follow the JPG or GIF image. The printed output from the PC gets a coat of 3M 77 and stuck down with a J-roller to either template material, or directly to the piece of wood I'm going to cut out. For templates, I use 1/4" lauan plywood, 1/4" MDF, clear or white plexiglas, thin offcuts of cherry or mahogany, depending on how durable and accurate and flexible the template needs to be.
There are lots of ways to solve your problem. I hope I've helped more than confused you.
Re: Plotting curves
Bob Smalser, Seabeck, WA
>Cut a flexible batten of dead-straight cedar or spruce....one that bends "fairly"...ie, with no kinks.
I make them using scarf joints up to 20' long for boats, for furniture, a piece of rip waste cut to 1/4-3/8" by 3/4-1" will work fine.
Ice picks or awls work best....simply spring the batten on the work piece where you want your fair curve and hold it in place with awls. When you can't mark up the work piece, lead weights called "ducks" or "whales" are made to hold the battens in place while scribing.
Re: Plotting curves
Tony - Memphis
>I usually draw it ona computer, then print it out and make a template. First thing to remember is that you only need to worry with one half, then mirror the other half. Also, don't forget the good old french curve(s). You can buy them or make your own. Using french curves and tangent lines can get you very far. Mark your major points and use them as your anchors. Flexible curves can help though I never uses them. Michael's and Hobby Lobby both have lots of drawing aids in their Art Dept.'s . Cut your template close then finish it by hand or with a spindle sander. Its more important to get a nice flowing curve than exactly match your drawing. Good luck with it.
Tony
Re: Plotting curves
Davy Barr
>Thanks for all the help, guys. Some great suggestions. I hadn't thought of getting stuff at Hobby Lobby / Michael's. I did notice the flexible curves and french curves that Lee Valley sells for dirt cheap prices too. I just have never tackled curves on my own unless directly copying them from another piece. Think in the near future I'll try making some of my own.
Re: Plotting curves
Bill Houghton, Sebastopol, CA
>Two others:
1. There are several methods for plotting ovals, most based on the relationship between the major and minor diameters. I've used the two-nails-and-string method, which is better drawn than described and besides I'm at work, away from my notes - but FWW shop tips collections and other sources list these methods.
2. If you're doing a shape that has a distinct center point, like a pointed arch or Colonial, country, etc. shape, develop (lay out) half your shape on a folded piece of card stock (or paper if you must, but card stock holds the shape better), with the center point terminating on the fold. Cut this out, and when you unfold it, voila! you've got your layout template.
3. Sometimes, you can actually do quite well with roughing out parts of the curve and then just freehanding the remainder. This is especially helpful for changing-radius curves, for example where the end of the curve tightens up. It's SUCH a rush, the first time you get a graceful shape just by freehand drawing. I would do this on some layout stock (card stock, cardboard, hardboard, etc.), not on your actual wood.
Re: Plotting curves
Gary Smyth
>I've seen whales on the floor of a lofting loft. I've never seen them painted. Did you do it or was it a set from somewhere? Where did the ones you show come from? What size are the ones shown? The ones I saw were 3"x5" and wighed about five or more pounds each.