Mainsail

Mainsail guide: selection and specifications

A mainsail is the primary driving sail set aft of the mast on the main boom or mast track. It accounts for 40–60 % of total sail power and determines balance, helm feel and heavy-weather behaviour. This page details the four core mainsail configurations—full-batten, partial-batten, in-mast furling and storm trysail—plus sizing, reefing and end-of-life options.

 3.000,00

Sail Area: 20.5m2
Luff: 11.12m
Foot: 3.54m
Leech: 11.7m

 3.095,00

Sail Area: 65.64m2
Luff: 15.65m
Foot: 6.25m
Leech: 15.68m

Original price was: € 5.125,00.Current price is: € 3.300,00.

Sail Area: 55m2
Luff: 16.53m
Foot: 5.75m
Leech: 17.25m

Original price was: € 6.385,00.Current price is: € 3.385,00.

Sail Area: 37m2
Luff: 113.2m
Foot: 4.96m
Leech: 13.84m

 3.500,00

Sail Area: 46m2
Luff: 14.82m
Foot: 5.94m
Leech: 16m

Original price was: € 5.900,00.Current price is: € 3.500,00.

Sail Area: 35m2
Luff: 7.2m
Foot: 5.85m
Leech: 8.5m

Original price was: € 4.900,00.Current price is: € 3.500,00.

Sail Area: 52m2
Luff: 15.8m
Foot: 5.4m
Leech: 16.7m

Original price was: € 5.600,00.Current price is: € 3.500,00.

Sail Area: 60m2
Luff: 17.9m
Foot: 6.15m
Leech: 18.5m

Original price was: € 5.370,00.Current price is: € 3.500,00.

Sail Area: 56.2m2
Luff: 16.3m
Foot: 5.75m
Leech: 17.2m

 3.518,00

Sail Area: 33.91m2
Luff: 13.79m
Foot: 5.09m
Leech: 14.38m

Original price was: € 9.400,00.Current price is: € 3.595,00.

Sail Area: 38.8m2
Luff: 11.99m
Foot: 4.53m
Leech: 12.71m

 3.599,00

Sail Area: 50m2
Luff: 18m
Foot: 5.45m
Leech: 18.71m

Definition and key measurements

The mainsail fills the main triangle bounded by mast, boom and tack. Standard dimensions:

P = luff length (mast track from boom to black band)

E = foot length (boom from mast to black band)

Roach = extra curve beyond the straight line from head to clew

Area = (P × E) / 2 + roach allowance

Girths (MGUM, MGM, MGU) control shape when reefed.

Mainsail categories

Full-batten mainsail

Horizontal battens span clew to luff

Zero flutter, maximum projected area

Requires lazy-jacks or Dutchman for flake control

Ideal for performance cruisers and racers

Typical roach 12–18 %, supported by 5–7 full battens

Partial-batten mainsail

3–4 short battens at upper leech only

Easier to hoist and flake by hand

Moderate roach (8–10 %)

Standard on boats under 30 ft or charter fleets

In-mast furling mainsail

Vertical battens or none; zero roach

Rolls inside mast via continuous-line furler

Infinite reef points, single-line cockpit control

Trade-off: 15–20 % less drive than battened mainsail

Cloth: vertical-cut Dacron or hydra-net for roll stability

Storm trysail

Separate sail, bright orange, 15–25 % of working mainsail area

Set on dedicated trysail track parallel to mast

Deep third reef replaces trysail on modern rigs

Required for World Sailing OSR Category 0/1

Procurement and upcycling

Send P/E measurements to info@resail.org for a matched second-hand mainsail or to arrange free collection of your retired sail. Every exchange keeps 20 m² of technical textile in circulation.