Trysail

A trysail is a small, heavy-duty replacement for the mainsail, used in storm conditions when the mainsail cannot be safely reefed further. It is the mainsail’s equivalent of the storm jib.

Design Purpose

Survival sailing: Provides drive and balance when the mainsail is dropped
Mainsail protection: Avoids running the mainsail in conditions that may cause permanent damage (flogging, hardware failure)
Independent from boom: A trysail is sheeted independently, so if the boom fails or becomes unsafe, the boat can still sail

When to use: When conditions exceed the third reef of the mainsail (typically 40+ knots), or when the boom or boom vang has failed.

Key Dimensions

Parameter	Specification	Notes
Area	15-20% of mainsail area	Small enough for extreme conditions, large enough for steerage
Luff Length	~50-65% of P	Must fit on mast track/groove above boom
Foot Length	~50-60% of E	Not boom-attached — sheeted to deck
Head Angle	Narrow (8-12°)	Flat profile

Sizing Reference by Boat Length

Boat LOA	Trysail Area (approx)	Luff (approx)	Foot (approx)
30ft (9m)	5-7 m²	5.0m	2.5m
36ft (11m)	7-10 m²	6.0m	3.0m
42ft (13m)	10-14 m²	7.0m	3.5m
50ft (15m)	14-18 m²	8.5m	4.0m

Materials

Cloth Selection

Material	Weight	Application
Heavy Dacron	8-10 oz/yd² (270-340 gsm)	Standard — proven, easy local repair
XRP13/XRP18 + Double Taffeta	190-220 gsm base	Performance cruisers who want lighter weight

Recommendation: Heavy Dacron for nearly all applications. A trysail is a safety item — durability and repairability in remote locations matters more than weight.

Thread

Seam thread: V-138 or V-207 polyester (double standard)
UV stitching: PTFE/Tenara on all exposed seams
Chafe areas: Bartack reinforcement at all hardware attachment points

Construction

Structural Requirements

Feature	Specification
Seam construction	Triple-stitched, zigzag + straight
Corner reinforcement	4-6 layers radial patches, 300-400mm diameter
Panel layout	Cross-cut (standard at this size) or radial
Leech line	Internal, 3mm pre-stretched polyester
Battens	None — trysails are battenless for simplicity and storm durability

Corner Hardware

Corner	Fitting	Specification
Head	Pressed ring (#4-#5) or webbing loop	Must accept halyard shackle
Tack	Heavy-duty D-ring (#5-#6)	Webbing anchor — must survive dynamic shock loads
Clew	Pressed ring (#6-#7) + heavy webbing	Sheets lead to quarter deck — must handle high side loads

For ring specifications, see Corner Fittings & Rings.

Luff Attachment

This is the most critical design decision for a trysail.

Method	Description	Pros	Cons
Dedicated trysail track	Separate track alongside or behind the mast groove	Independent of mainsail, fastest deployment	Requires installation on mast
Mast groove (shared)	Bolt rope or slides in the mainsail groove	No extra hardware needed	Mainsail must be fully dropped first; slides may jam
Lashing	Lashed to mast with webbing loops	Works on any mast, no hardware needed	Slower deployment, more chafe

Strong recommendation: A dedicated trysail track is the safest option. If the mainsail’s halyard or slides jam in heavy weather, you can still set the trysail on its own track. Most surveyors and insurers prefer this arrangement for offshore-rated boats.

Track Specifications (Dedicated)

Component	Specification
Track material	T-track aluminum, anodized
Track length	Equal to trysail luff + 30cm clearance above boom
Track position	Aft of mainsail groove, same side
Gate/Switch	Not required — trysail track is independent
Slides	Standard external slides, matching track profile

Sheeting

Unlike the mainsail, a trysail is NOT attached to the boom. It sheets directly to the deck or toerail.

Component	Specification
Sheet diameter	10-14mm (same as or heavier than mainsheet)
Sheet length	Long enough to reach quarter cleats from clew — typically 2× boat length
Lead point	Quarter deck cleats or genoa track car (moved aft)
Blocks	Optional turning blocks — often sheeted directly to cleats
Pennant	May need a tack pennant to raise the tack above the boom

Sheeting Diagram (Typical)

        Head → Mast (trysail track or lashing)
         |
    [Trysail]
         |
        Clew → Sheet leads to quarter deck cleat
         |
        Tack → Mast base + tack pennant (if needed to clear boom)

Color & Visibility

Requirement	Specification
ISAF/World Sailing	High-visibility orange recommended (not always mandatory for trysails)
Standard	International Orange or bright red
Panel coverage	Full sail or at least 2 highly visible panels

Regulatory References

Rule	Requirement
World Sailing OSR 4.26	Trysail required for Category 1-2 races
ISAF Cat 1-2	Must be capable of being set independently of boom
Cat 3	Trysail or fully reefable mainsail acceptable

Storage & Deployment

Storage: Pre-packed in labeled bag, slides pre-attached if using track
Location: Accessible from companionway — separate from storm jib bag
Tack pennant: Pre-cut and stored with the trysail
Sheets: Dedicated trysail sheets, pre-measured and coiled with the sail
Practice: Deploy at least once per season — setting a trysail in 40 knots for the first time is not the time to learn

Pro tip for your customers: Set up the trysail track and practice deployment during spring commissioning. A 15-minute drill in calm conditions prevents a dangerous 45-minute struggle in a storm.