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.

 1.250,00

Sail Area: 25m2
Luff: 9.22m
Foot: 3.71m
Leech: 9.57m

 1.330,00

Sail Area: 32.5m2
Luff: 13.7m
Foot: 4.8m
Leech: 14.14m

 1.365,00

Sail Area: 28.5m2
Luff: 12.44m
Foot: 4.32m
Leech: 14.01m

 1.390,00

Sail Area: 26m2
Luff: 10.23m
Foot: 4.45m
Leech: 11.29m

Original price was: € 2.595,00.Current price is: € 1.395,00.

Sail Area: 29.1m2
Luff: 13m
Foot: 3.8m
Leech: 13.25m

Original price was: € 1.995,00.Current price is: € 1.398,00.

Sail Area: 19m2
Luff: 9m
Foot: 3.3m
Leech: 9.7m

Original price was: € 1.995,00.Current price is: € 1.450,00.

Sail Area: 22.3m2
Luff: 13.78m
Foot: 3.4m

 1.450,00

Sail Area: 26.5m2
Luff: 13.5m
Foot: 3.94m
Leech: 13.87m

 1.452,00

Sail Area: 29m2
Luff: 14.24m
Foot: 4.15m
Leech: 14.63m

 1.452,00

Sail Area: 27m2
Luff: 12.18m
Foot: 4.49m
Leech: 12.72m

 1.452,00

Sail Area: 27m2
Luff: 12.2m
Foot: 4.45m
Leech: 12.72m

Original price was: € 2.900,00.Current price is: € 1.500,00.

Sail Area: 29m2
Luff: 12.51m
Foot: 4.44m
Leech: 13.11m

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.