Inputs
I and J describe the foretriangle; P and E describe mainsail luff and foot limits; LP is the headsail luff-perpendicular. Crew and use choices shape the practical questions added to the brief.
Complete planning
Yacht sail specification studio
Estimate the working geometry, then turn the numbers into a consistent brief for professional verification.
Worked example
Example: 38-foot short-handed cruiser
I 14.0 m, J 4.2 m, P 13.2 m, E 4.5 m and LP 5.04 m produces a 120% genoa, approximately 35.3 m² of headsail area and a 31.2 m² triangular mainsail before roach.
Tool guide
How to use and interpret this tool
It converts verified rig dimensions and use priorities into a consistent first-pass specification for comparing quotes.
Decision logic
Triangular areas use ½ × height × base. Genoa overlap is LP ÷ J × 100. A selected roach allowance is added only as a transparent estimate.
Read the result
Treat the result as a common briefing sheet, not a finished sail design. Differences between loft proposals become easier to identify when their starting brief is identical.
Worked example
For I 14.0 m, J 4.2 m and LP 5.04 m, overlap is 120% and approximate headsail area is 35.3 m². P 13.2 m and E 4.5 m produce a 29.7 m² triangle before roach.
Common mistakes to avoid
- Using brochure dimensions after the rig or furler has been modified
- Comparing quotes built from different intended wind ranges
- Treating estimated area as a cut plan
Professional verification
This tool supports briefing and comparison. It does not replace measurement on the boat, structural engineering, class or safety rules, or a sailmaker's final design.
Continue the decision