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.

 1.500,00

Original price was: € 2.050,00.Current price is: € 1.500,00.

Sail Area: 20m2
Luff: 9.05m
Foot: 3.92m
Leech: 9.5m

 1.535,00

Sail Area: 13.6m2
Luff: 8.25m
Foot: 2.76m
Leech: 8.5m

 1.695,00

Sail Area: 32m2
Luff: 13.67m
Foot: 4.43m
Leech: 13.97m

Original price was: € 2.200,00.Current price is: € 1.700,00.

Sail Area: 22m2
Luff: 9.25m
Foot: 4.28m
Leech: 10.05m

Original price was: € 2.914,00.Current price is: € 1.748,00.

Sail Area: 26m2
Luff: 12.12m
Foot: 4.22m
Leech: 12.54m

Original price was: € 3.950,00.Current price is: € 1.750,00.

Sail Area: 28.8m2
Luff: 11.15m
Foot: 4.5m
Leech: 11.83m

 1.750,00

Sail Area: 25m2
Luff: 10.85m
Foot: 3.85m
Leech: 11.4m

 1.800,00

Sail Area: 22.6m2
Luff: 11.2m
Foot: 3.32m
Leech: 11.65m

 1.800,00

Sail Area: 45m2
Luff: 16.3m
Foot: 5.23m
Leech: 16.81m

Original price was: € 2.572,00.Current price is: € 1.815,00.

Sail Area: 39.7m2
Luff: 14.5m
Foot: 4.6m

Original price was: € 2.620,00.Current price is: € 1.835,00.

Sail Area: 19.3m2
Luff: 9.75m
Foot: 3.35m

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.