What is a French curve and how is it used? Lucy G.,
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Technically, a French curve (A) is a drafting tool used to connect points in a smooth curve. It's used for garment pattern drafting and alterations, especially for necks and armholes when trueing and blending seamlines. Other rulers for drafting patterns include a curve ruler (B) (used for shaping hips, hemlines, elbows and lapels) and fashion curves (C&D) (available in most fabric stores, a combination of a French curve and the curve ruler).
Trueing a line is the process of straightening seamlines to establish correct seam lengths. Blending is the smoothing, shaping and rounding of angular lines for a smooth transition from one point to another. Trueing and blending are often done at the same time.
For most home sewing, the fashion curve is used mainly for pattern alterations when fitting, changing or adding new design lines. See how the fashion curve is used in the following examples:
When cutting out a dart and lowering it to match your bust point, the side becomes uneven. Use the ruler edge that closely resembles the pattern line to draw a new or "true" the cutting line (1).
If you're using a slash and spread method to add width to a pattern piece, use the long curved edge to draw the new cutting line at the outside edge (2). Hint: Sometimes you'll need to flip the ruler and draw the line evenly from both sides for a smooth, symmetrical line.
When your body curves where a pattern line is straight, add a curve to the pattern. Measure your body and mark the corresponding points on the pattern. Then use the curved edge to connect the points (3).
To lower a neckline, mark the desired depth on the pattern. Then place the ruler so it intersects the original shoulder cutting line and lines up with the new mark; trace the resulting curve (4).
Sewing Q&A
