How to Use French Curves

Use the French curve to draw curves with a seamless fit.

A French curve, a plastic or wooden curved template often used in the design of cars and dresses, is an instrument used to draw curves on paper or on your computer screen. The French curve allows you to draw and connect curves together so they are perfectly fitted together without using mathematics calculations. Using the French curve is simple. Just align one of the curve sections on the French curve to the two points you want to connect with a curve. Then trace the edge of the French curve with your pencil or electronic pen.

Plot two points on a piece of paper such that the total distance between them is less than 1/4 the distance of the longest curve on your French curve. Use an electronic tablet and pen to plot the points on your computer screen if you prefer to draw your curves within a graphic design program.

Select an edge of the French curve such that the curve edge of the French curve will pass through both the points. Try different edges with different curvatures to locate the section edge of the French curve that will pass through the two points and give you the type of curve you want.

Move your pencil along the edge of the French curve to draw the curve that connects the points together. Use your electronic pen to trace the edge of the French curve on your electronic tablet if you are drawing curves in a graphic design program.

Plot another point that is on one side of the curve and is between the two end points of the curve. Use your French curve to locate a curve between one of the end points of the original curve and the new point, called P1. Now trace the edge of the French curve between the two points. Repeat the procedure for the other end point of the original curve to the point P1. Observe that your curves form a closed group of curved lines.

  • The actual math behind the French curve is related to tangents, points of inflections and center of curvatures. Understanding these concepts will help you get the most out of your French curve. If you want to draw curves easily with your graphic design program, use an electronic pen and tablet. Simply lay down the French curve on your tablet and trace around the edges of the French curve with your electronic pen.

Mark Stansberry has been a technical and business writer over for 15 years. He has been published in leading technical and business publications such as "Red Herring," "EDN" and "BCC Research." His present writing focus is on computer applications programming, graphic design automation, 3D linear perspective and fractal technology. Stansberry has a Bachelor of Science in electrical engineering from San Jose State University.