Downwindsail

Function of a downwind sail

The downwind sail replaces the working headsail and mainsail combination on broad reaches and runs. It projects significantly more area into clean air, increasing boat speed by 30–100 % compared to white-sail configurations. Key performance parameters:

• AWA (apparent wind angle): 80°–180°
• VMG (velocity made good): optimized at 120°–150° true
• Projected area: 160–220 % of the foretriangle
• Stability: dependent on cut, cloth weight and crew trim

Downwind sail types: spinnakers

Resail offers only spinnakers—the proven standard for recreational and racing sailors seeking reliable downwind performance.

Symmetric spinnaker

• Equal luff lengths; pole required on both gybes
• SL ≈ ISP (spinnaker halyard height)
• SF ≈ 1.8 × J (foretriangle base)
• SMG ≥ 1.8 × J (IRC/ORC compliance)
• Cloth: 0.5–2.2 oz ripstop nylon, radial or tri-radial panel layout
• Wind range: 5–30 kn (code-dependent)
• Rigging: spinnaker pole, uphaul, downhaul, twin sheets/guys

Asymmetric spinnaker

• Fixed tack point; flown from bowsprit or stem fitting
• Luff length 5–15 % longer than symmetric equivalent
• SMG 70–85 % of foot
• Cloth: 0.7–1.8 oz nylon or Airx polyester
• Wind range: 6–28 kn
• Rigging: tack line, two sheets, optional top-down furler

 

Selection criteria for your downwind sail

Measure ISP and J from rig documentation or physical tape.

Match spinnaker code to conditions:

Light air / reaching → 0.5–0.75 oz (S0/A1)

All-purpose running → 1.5 oz (A2)

Heavy air → 2.2 oz (S4/A4)

 

Crew capability: symmetric requires pole work; asymmetric suits short-handed crews.

Storage: both pack into turtles; asymmetric generally more compact when furled.

Maintenance protocol

• Rinse thoroughly with fresh water after each use.
• Dry completely before packing to prevent mildew.
• Store in a dedicated spinnaker turtle, elevated off the cabin sole.
• Inspect corner reinforcements, radial patches and leech tapes monthly.
• Limit UV exposure to 80 hours per season.

End-of-life upcycling for downwind sails

When a spinnaker exceeds 25 % stretch or suffers irreversible colour fade, it is retired from active duty. Resail repurposes the high-performance nylon into durable, lightweight products:

• 60 L expedition duffels with original corner rings and sail numbers
• Spinnaker-cloth wind scoops for tropical anchorages
• Ultralight, packable beach rolls (5,000 mm hydrostatic head)
• Double-layer hammocks rated to 180 kg

Each retired downwind sail diverts 25–45 m² of ripstop nylon from landfill.Procurement and upcycling

Send your ISP and J measurements to info@resail.org to receive a matched second-hand spinnaker within 48 hours. Alternatively, request a free collection label to send us your retired downwind sail. Every transaction keeps 30 m² of performance fabric in active circulation.