How to measure a sail | Sailmaker's Fieldbook

Written by Fieldbook Desk.

Before the tape comes out

Identify the sail, boat, side and condition: loose on a clean floor, hoisted, or under a stated tension. Photograph the head, tack, clew, slides, reef points, battens and corner hardware. Note whether the sail is dry, stretched, recently repaired or carrying a cover.

A field sequence

1. 01
   Name the point: head, tack, clew, luff, leech, foot or station.
2. 02
   Record the unit and the tool. Do not mix a tape reading with a plan dimension without marking the difference.
3. 03
   Take the paired dimensions the sailmaker or class form asks for, then repeat the critical one.
4. 04
   Write an observation beside the number: seam, fitting, bend, crease, chafe or obstruction.

Photograph the interfaces

Overall luff, leech and foot figures do not explain how the sail connects to the rig. Add clear views of the headboard, tack and clew attachments, slides or bolt rope, reef cringles, batten receptacles and any cover or furling feature. Place a ruler beside local hardware and record the mast, boom or furler model when known. The Seldén sailmaker guide separates these interfaces by system because a similar-looking slide or reef arrangement can require different dimensions.

Resolve disagreement before sending

Repeat critical readings from the same named points. If two attempts disagree, inspect the tape path, endpoint, sail tension and movement instead of averaging the values. Keep raw readings and mark any later conversion. Send the completed form, sketches and photographs as one dated package, with a list of unknowns. Retain an unchanged copy so a follow-up request creates a second traceable observation rather than silently replacing the first.