French curve

A French curve is a template usually made from metal, wood or plastic composed of many different segments of the Euler spiral (aka the clothoid curve). It is used in manual drafting and in fashion design to draw smooth curves of varying radii. The curve is placed on the drawing material, and a pencil, knife or other implement is traced around its curves to produce the desired result. They were invented by the German mathematician Ludwig Burmester and are also known as Burmester (curve) set.

A set of the three most common French curves, also known as a Burmester set. The bottom object is most commonly used for hyperbolas; the smaller one above it is suited for ellipses. The large one is used mostly for parabolas.[1]

Clothing design
A complete Burmester set from the Lexikon der gesamten Technik (1904)

French curves are used in fashion design and sewing alongside hip curves, straight edges and right-angle rulers. Commercial clothing patterns can be personalized for fit by using French curves to draw neckline, sleeve, bust and waist variations.

Digital versions

As modern computer-aided design (CAD) systems use vector-based graphics to achieve a precise radius, or approximate curves, mechanical templates (and most mechanical drawing techniques) have become obsolete outside of stitchers' home pattern adjustments and fashion designs. Manual curve templates are also used by model makers and others maintaining traditional trades and skills. Digital computers can also be used to generate a set of coordinates that accurately describe an arbitrary curve, and the points can be connected with line segments to approximate the curve with a degree of accuracy, although this varies with the type of curve. Some computer-graphics systems make use of Bézier curves, which allow a curve to be bent in real time on a display screen to follow a set of coordinates that are not on the line being drawn. This is different from the way a French curve is placed on a set of three or four points on paper.

See also
  • Flat spline – Long flexible batten used to produce a fair curve through a set of points
  • Lesbian rule – Flexible strip of lead for use in molding
  • Ruler – An instrument used to measure distances or to draw straight lines
  • Technical drawing tool – Tools and instruments used for accurate and precise manual drafting

References
  1. "Drawing tools – French curves".
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