Halyard sizing calculator

How the calculator works

1. Line load

   load (kg) = area (m²) × wind² (kn) × 0.02104, with the apparent wind on the sail, as PremiumRopes gives it for sheets and halyards. A 2:1 halyard halves the load on the line.

2. Strength

   The working load stays at or under 20% of the rope's breaking load, so the rope must break at 5 times the load (Samson Line Selection Guide).

3. Creep

   Dyneema held under a steady load creeps little below 15% of its break and much less below 10% (Rigging Doctor). A loaded halyard is held for hours, so the rope must break at 6.7 times the load. This usually decides the size.

4. Splice

   A good splice costs about 5 to 10% of strength, so 10% comes off the catalogue breaking load before the comparison (PremiumRopes).

5. Fit

   Go 1 to 2 mm under the clutch's maximum (PremiumRopes), and give Dyneema a sheave at least 8 times its diameter to keep its full strength (RYA).

Before you order

• These are steady-wind figures. Gusts, waves and a shock load on the hoist go well past them.
• For monohulls with soft sails. Not for multihulls.
• No rope or hardware maker publishes a halyard load formula, and Samson's advice is to have your rigger set halyard loads. Use the result as a starting point the loft confirms.
• Catalogue breaking loads are for new rope. Knots, small sheaves, UV and chafe all take strength away.
• Clutch grip and handling often decide the diameter on a small boat, and class rules can set a minimum. Check your class page.
• Only ropes with published breaking loads are sized here: LS Palma and LS Rio. Of those, each halyard gets the one we rank higher for it (our ranking, job by job). For anything else, ask the loft.
• Matching a Marlow halyard? Lion and Marlow ropes, side by side.