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.

 1.865,00

Sail Area: 29.5m2
Luff: 12.94m
Foot: 4.57m
Leech: 13.56m

Original price was: € 3.590,00.Current price is: € 1.895,00.

Sail Area: 55m2
Luff: 16.5m
Foot: 5.8m

 1.936,00

Sail Area: 35m2
Luff: 13.91m
Foot: 5.2m
Leech: 14.52m

Original price was: € 3.614,00.Current price is: € 1.936,00.

Sail Area: 22.2m2
Luff: 9.58m
Foot: 4.15m
Leech: 10.27m

 1.975,00

Sail Area: 26m2
Luff: 11m
Foot: 3.85m
Leech: 11.47m

Original price was: € 3.371,00.Current price is: € 1.995,00.

Sail Area: 17.1m2
Luff: 7.12m
Foot: 3.7m

 2.000,00

Sail Area: 42m2
Luff: 14.9m
Foot: 5.3m

Original price was: € 3.121,00.Current price is: € 2.185,00.

Sail Area: 24.5m2
Luff: 11.1m
Foot: 374m
Leech: 11.4m

 2.195,00

Sail Area: 33m2
Luff: 13.24m
Foot: 4.13m
Leech: 13.4m

Original price was: € 3.260,00.Current price is: € 2.245,00.

Sail Area: 27m2
Luff: 12.37m
Foot: 4.38m

Original price was: € 3.750,00.Current price is: € 2.250,00.

Sail Area: 43.2m2
Luff: 14.2m
Foot: 5.35m
Leech: 15m

Original price was: € 3.575,00.Current price is: € 2.395,00.

Sail Area: 21.4m2
Luff: 10.01m
Foot: 3.42m
Leech: 10.5m

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.