1. Avoid abrupt changes in curvature by placing the short radius of the french curve toward the short radius portion of the line to be drawn.
2. Change your position around the drawing board when necessary so that you can work on the side of the french curve that is away from you.
3. You should avoid working on the "under" side of the french curve.
4. Place the french curve so that it intersects at least two points of the curve. 3 points is always recommended.
5. When drawing the curve along the edge of the french curve, stop short of the last point intersected. Then move the french curve along to intersect two or three more points.
6. Make sure that the edge of the curve connects smoothly with the part of the curve that is already drawn.
7. When drawing irregular curves, you can draw a perfectly smooth curved line by plotting enough points and by drawing in short steps.
The figure above shows how a smooth curve is draw through a series of plotted points.
- The french curve in view A matched points 1, 2, 3, and 4. Draw a curve from 1 to 3 only.
- At B, the curve matches points 3 to beyond 4. Draw a curve from 3 to 4 only.
- At C, it matches points 4, 5, and 6. Draw a curve from 4 to just short of 6.
- At D, it matches a point short of 6 to beyond 7. Draw a curve from 6 to 7.
- At E, it matches a point short of 7 to beyond 9. Draw a curve from 7 to 9.
- At F, it matches a point short of 9 to beyond 11. Draw a curve from 9 to 11.
You will probably notice how the french curve is turned over and reversed to find portions that fit the points on the line with increasing or decreasing changes in the curvature.
Here are my Rotring french curves that I use in my drawing plates. They are quite new. I've bought them Wednesday this week in order to finish a plate because I need to trace an irregular ellipse. By the way, if you wanted to learn how to draw an ellipse, click HERE.