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.

 4.950,00

Sail Area: 86.19m2
Luff: 17.66m
Foot: 7.11m
Leech: 19.91m

Original price was: € 8.632,00.Current price is: € 5.178,00.

Sail Area: 53m2
Luff: 15.78m
Foot: 6.74m
Leech: 16.82m

Original price was: € 7.600,00.Current price is: € 5.325,00.

Sail Area: 61m2
Luff: 15.83m
Foot: 4.77m
Leech: 15.97m

Original price was: € 8.968,00.Current price is: € 5.380,00.

Sail Area: 50m2
Luff: 17.2m
Foot: 5.9m
Leech: 17.65m

Original price was: € 10.275,00.Current price is: € 5.900,00.

Sail Area: 60m2
Luff: 15.4m
Foot: 5.66m
Leech: 16.12m

 5.950,00

Sail Area: 31.76m2
Luff: 11.05m
Foot: 3.82m
Leech: 11.60m

Original price was: € 8.500,00.Current price is: € 6.900,00.

Sail Area: 39.4m2
Luff: 14m
Foot: 4.96m

Original price was: € 26.470,00.Current price is: € 9.950,00.

Sail Area: 65m2
Luff: 19.72m
Foot: 6.55m
Leech: 20.55m

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.