Tell me if this tracks with your experience. My first projects featured straight lines — and only straight lines. Next I discovered sections of circles: think roundovers and uniform Shaker curves. From there, I felt more confident to try irregular profiles.
The challenge lies in drawing a complex curve either directly on a workpiece or in shop drawings. After struggling with freehand attempts, a set of French curves saved the day.
While they seem random, French curves are made up of segments of a whole lexicon of geometry vocabulary: ellipse, parabola, hyperbola, involute, and logarithmic spirals. The ways they get plotted, mixed, and matched results in the various forms you find. And there are way more forms of these than the typical three-piece set. It’s a good idea to have curves in a range of sizes.
Dirk Ver Steeg, one of the long-time illustrators here at ShopNotes and Woodsmith shared some helpful information from his drafting class books back in the days of pencil and ink drawings. Together with other information and shop practice, I’ve found ways to use these tools to improve my work.
CASE STUDY.
 |
| This bookcase was the inspiration for my own version. Changing the various profiles results in a unique project. |
Rather than gather a list of options, I’ll show you three ways I used French curves in a recent project of mine. The bookcase shown above was featured way back in Woodsmith 108 (1996). While billed as a children’s bookcase, I liked the lines of it and decided to make a version to house my woodworking books — with a few changes.
THE BASIC TRACE.
My work started by making a template for the sides. A shallow arc on the bottom of the sides separates it into feet. For something more shapely, I found a swoopy section of a French curve that I liked and traced it on the template.
 |
| French curves come in a wide variety of shapes and sizes. Our shop-made ones are shown at left. The large versions were created on a CNC by Creative Director Chris Fitch. The plastic set at right came from an online source (refer to page 46). |
DUPLICATING CURVES.
 |
 |
| Masking tape wrapped around the French curve allows you to trace a section onto a workpiece in multiple locations consistently. Arrows on the tape are a further memory aid. |
 |
| To make a mirror image, the tape needs to wrap onto the opposite face of the curve. Take care to keep the edges of the tape aligned on each face for an exact match. |
At the top of the case, another simple arc is shown in the plans. My next change was to modify that arc into an elliptical profile. The result was more dynamic to my eye.
The steps below show how to create a symmetrical look. I marked the width of the case on the template, then played around with different sections of the curve to find one that appealed to me.
I used masking tape to mark the section of curve I want to use. Wrap the tape around to the back face as well. Align the marks with the top and edge line of the template and draw one side, as shown in Step 1. For the opposite side, all you need to do is flip the curve over and realign the taped marks, as you can see in Step 2.
SINUOUS CURVES
The leading edge on the sides of my bookcase features a long irregular curve — more interesting than a straight taper. The plans show a scaled profile on a grid. The case is too large to blow this up on a photocopier. Instead I plotted it out by hand.
POINTS OF INTERSECTION.
 |
 |
| Use a square and ruler to plot a series of points that correspond with whole number intersections on the scaled profile in the plans. |
 |
| Starting at the bottom, move a French curve around with the goal of connecting two to three points. Trace this segment with a pencil. Ideally, the curve should extend in the general direction of the next plotted point. |
 |
| Using one of the last points in the string, connect another set of points with the curve. Watch the transition between sets to avoid abrupt changes in direction. |
 |
| After connecting all the dots, go back over the line to smooth and refine any areas that look bumpy. The curve should flow seamlessly from end to end. |
I found places on the curve that aligned with whole number grid coordinates. Step 1 shows how, using a ruler and a square, I mapped those points on the template. Now it’s time for the curves.
It’s unlikely that your French curve will align with all the points. Instead, start by aligning smaller groups of dots with a section of the curve. Ideally three at a time, but you take what you can get, as shown in Step 2.
Extend the line past the third dot and in the direction of the next set. Use this extension as an on-ramp to transition from one section of dots to the next. Repeat this process all the way along, flipping and sliding the French curve as needed to complete the curve.
REFINEMENT.
Step back to examine the curve you created. Chances are there will be some noticeable inconsistencies. Take another pass in those sections with the French curve to form a graceful line.
Like any tool, French curves require practice to develop skill. The reward is greater confidence in your designs and better-looking projects.
ESSENTIAL Drawing Tools
French curves are just one element of a set of drafting tools. Here are a few others that will help you develop a good set of plans for your next project.
| | |
| ---------- | ---------- |
|
|T-squares are used to establish baselines and floors in drawings. The head follows the edge of your drawing board.|
|
|An assortment of triangles and protractors allow you to create straight lines and angles.|
|
|A pencil compass lets you create a custom-sized radius. Circle templates are quicker for common sizes in small increments.|
