Gennaker and Code Zero

Asymmetric downwind sails have revolutionized racing sailing. While the classic symmetric spinnaker still dominates on tight leeward legs, modern crews increasingly rely on gennakers and Code Zeros – sails that bridge the gap between jib and spinnaker and deliver enormous speed advantages on broad reaching angles. Those who master these sails gain not only on the downwind leg, but also on reaching courses and in light-air phases where competitors are still sailing with an underpowered jib.

This guide explains the differences between gennaker and Code Zero, optimal use ranges by wind angle, professional set and drop sequences, trim fundamentals, and typical mistakes in competition. It complements Spinnaker Set and Drop and connects to Wing-on-Wing and Gennaker Set as well as Optimizing VMG and Angles.

What Are Gennaker and Code Zero?

Both sail types belong to the family of asymmetric downwind sails – they do not have identical windward and leeward sides like a symmetric spinnaker and are flown without a spinnaker pole. The difference lies in cut, material, and area of use.

Gennaker

The gennaker (also A-sail or asymmetric spinnaker) combines characteristics of a genoa and a spinnaker. It is voluminous, made from lightweight laminate or nylon, and suitable for reaching angles up to almost close-hauled. Typical use angles range between 70 and 160 degrees AWA (Apparent Wind Angle). On race courses it is set after the windward mark or used on reaching legs when the wind comes sufficiently from aft.

Code Zero

The Code Zero is a flatter, more tightly cut asymmetric downwind sail made from laminate or structural Dacron. It was originally developed for the America's Cup to maximize sail area on apparently close-hauled courses under tight rating rules. Today it is standard on IRC and ORC racers, J/70, Melges 24, and many performance yachts. The Code Zero flies at AWA from approximately 40 to 90 degrees – significantly closer to the wind than a gennaker.

Use Ranges by Wind Angle and Boat Class

The right sail choice decides VMG and boat stability. Setting a gennaker too early costs control; dousing a Code Zero too late slows you down on reaching legs.

Rigging and Setup On Board

Asymmetric downwind sails require adapted rigging. Without proper preparation, set times increase and the risk of sail damage rises.

Furling System vs. Turtle/Bag

Modern boats use furling systems at the bow or on the bowsprit extension. The gennaker or Code Zero is wrapped around the furler drum and unfurled via the sheet. Alternatively, smaller boats work with a turtle or bag – similar to a symmetric spinnaker, but without a pole.

Bowsprit and Tack Point

The tack (luff) is attached at the bowsprit end or on an extension. The distance from the mast influences sail shape: further forward creates more volume and stability, further aft allows tighter angles. Code Zero systems often have a separate, higher tack point for better lead angle when close-hauled.

Sheets and Halyard

• Halyard: Carries the sail at the mast; on furlers often an anti-torsion halyard
• Sheet: Controls sail shape and angle of attack
• Tweaker or barber hauler: Changes sheet angle for fine trim
• Cunningham (on Code Zero): Tightens the luff in gusts

Gennaker Set – Crew Sequence

A fast gennaker set follows the same choreography as an asymmetric spinnaker set, only without pole work. The crew must know the sequence by heart.

Preparation Before the Windward Mark

1. Open furler or bag – bowman checks sheet and tack for tangles
2. Halyard at mast – head on hook or furler prepared
3. Sheet free – through all blocks, no knots in the run
4. Tack prepared – shackle at bowsprit, extension secured
5. Tactical decision – gybe plan and gate choice communicated

Set After the Mark Rounding

1. "Gennaker hoist!" – mastman/pitman hoists the sail
2. Unfurl – set sheet until sail is fully deployed
3. "Made!" – confirmation, sail up and unfurled
4. Fine trim – trimmer optimizes sheet, tweaker, and course
5. VMG optimization – coordination with helm and tactician

Code Zero Set on Reaching Legs

The Code Zero is often set before the windward mark or on a reach leg when the course is too tight for a gennaker but too broad for the jib.

1. Stabilize course – AWA between 50 and 80 degrees
2. Douse jib (optional) – to avoid sail conflicts
3. Unfurl Code Zero – controlled, without sudden weather helm
4. Trim mainsail – adjust twist and ease to Code Zero
5. Fine tuning – Cunningham and sheet for maximum VMG

Drop and Douse Maneuvers

A controlled drop is just as important as a fast set. Tangled sheets or a sail in the water cost valuable seconds and can damage equipment.

Gennaker Drop

• Furler drop: Ease sheet, furl sail with furler – fastest method
• Bag drop: Gather sail into bag/turtle – bowman and pitman coordinate
• Gybe drop: Drop during gybe, new downwind sail prepared on other side

Code Zero Douse

The Code Zero is usually doused via furler. Important: ease sheet first, then furl – otherwise the furler drum may break or the laminate may be damaged. In strong wind, depower mainsail first, see Depower and Reduce Sails.

Trim Fundamentals for Asymmetric Downwind Sails

Good trimming separates fast from average crews. The fundamentals apply to gennaker and Code Zero, with different emphases.

Gennaker Trim

The trimmer watches for:

• Sheet length: Too tight = collapsed shape, too loose = unstable leech
• Tweaker angle: Lower angle for more power, higher for more control
• Course: Helmsman keeps AWA in optimal window (usually 110–130 degrees for VMG)
• Mainsail: Must give the gennaker room – coordinate ease and twist

Code Zero Trim

The Code Zero behaves more like a jib:

• Luff: No wrinkles, but not over-tensioned either
• Sheet: Finer than with gennaker – small changes have big effect
• Cunningham: Activate in gusts to reduce power
• Mainsail: Trimmed tighter than for gennaker use

Tactical Decisions in a Racing Context

When is which sail worth it? The answer depends on course layout, fleet position, and weather.

Leeward Leg After Windward Mark

• Set gennaker when AWA is stable above 90 degrees and enough distance from competitors
• Keep Code Zero when the leg is short and an early gybe is planned
• Jib/mainsail when the fleet is tight and a set would be too risky

Reach Legs and Gate Choice

On reaching legs between windward and leeward marks, a Code Zero can significantly increase VMG. The tactician must weigh: more speed on the reach leg vs. longer drop before the next mark rounding.

Light-Air Strategy

In calm phases, the Code Zero maximizes sail area efficiently – a topic also covered in depth under Maximizing Sail Area. Crews that fly a Code Zero in 5–8 kn wind often overtake boats struggling with an underpowered jib.

Crew Roles and Communication

Asymmetric downwind sails require the same precision as symmetric spinnaker maneuvers. Clear commands and roles are mandatory.

Crew weight distribution affects stability – when using the gennaker in gusts, shift weight aft, see Hiking and Trapeze.

Checklist: Gennaker and Code Zero in Training

Before the first racing use, the crew should check off the following points:

• Furler spins freely in both directions, tack shackle secured
• Set sequence practiced at least 20 times (target: under 12 seconds set time)
• Drop practiced in all variants (furler, bag, gybe drop)
• Wind angle limits for both sails known within the team
• Communication: Uniform commands ("Hoist", "Made", "Drop", "Furl")
• Emergency: Douse in gust without discussion – skipper's decision
• Equipment check: Tears, worn furler drum, sheet ends
• Tactical plan: When gennaker, when Code Zero, when jib/mainsail

Typical Mistakes and How to Avoid Them

1. Gennaker set too early – boat not yet on leeward course, sail luffs or tangles in rigging. Solution: Stabilize course first, then hoist.
2. Code Zero too close to the wind – AWA below 40 degrees causes overload and weather helm. Solution: Bear away or set jib.
3. Sheet too tight when furling – furler drum or laminate damaged. Solution: Ease sheet completely before furling.
4. Missing crew communication – two people pulling on different lines at the same time. Solution: Pitman as sole coordination point.
5. Wrong sail choice in light air – gennaker at 6 kn instead of Code Zero. Solution: Evaluate AWA and TWS live, don't decide the night before.
6. Drop neglected in training – 80% of training time on set, 20% on drop. Pros train drop and set in a 50:50 ratio.

Frequently Asked Questions

• Can I fly gennaker and Code Zero at the same time? – No, only one active downwind sail.
• Do I need a bowsprit? – Recommended for performance boats.
• Which sail at 12 kn, AWA 100°? – Gennaker.
• Code Zero close-hauled? – Only up to approximately 75° AWA.
• Furler or bag? – Furler faster, bag cheaper.

Material Choice and Maintenance

Sail type and material influence durability and performance. Details on laminate vs. Dacron can be found under Sail Types and Use Ranges.

• Gennaker: Often nylon or lightweight laminate, more volume, more sensitive to UV
• Code Zero: Structural laminate or Dacron, longer lifespan with frequent use
• Maintenance: Rinse furler after each race day, check sheets for wear, store sails dry and wrinkle-free

Related Topics

• Spinnaker Set and Drop
• Wing-on-Wing and Gennaker Set
• Optimizing VMG and Angles
• Boat Handling and Crew Work
• Maximizing Sail Area