STORM SAILS
Heavy Weather Jib
Bigger than a storm jib and built to keep pointing in a blow — the heavy-weather headsail, or No. 4 genoa, that bridges the gap between your everyday sails and your storm canvas.
What Is a Heavy Weather Jib?
The Heavy Weather Jib — also known as a No. 4 genoa — is a specialized headsail for the strong, but not extreme, conditions where your standard headsails become hard to handle. It bridges the gap between your everyday sails and your storm sails, keeping the boat under control and still performing when the breeze builds. A good No. 4 is typically about 85% luff length and 85% LP, which balances power against control.
ISAF limits a heavy weather jib’s area to 13.5% of the foretriangle height squared — but we think that’s more sail than most boats want once it’s really blowing. The rules also bar reef points and recommend against high-modulus material. Here we differ: if you’re going upwind in 28–35 knots, we believe the sail needs low-stretch cloth and battens to hold an effective shape. If the jib is cut for a luff-groove device, it must also carry an alternative attachment to the stay — most commonly grommets along the luff so the sail can be tied on directly.
Bridges the Gap
Between everyday and storm sails
Bigger than a storm jib and built for strong — not extreme — conditions, the No. 4 keeps you sailing well when your regular headsails become a handful.
Points in a Blow
Low-stretch cloth with battens
For upwind work in 28–35 knots we build it from low-stretch material with battens, so it holds an effective shape instead of going soft and full.
Backup Built In
Two ways to attach
It sets on your primary luff-groove or furler, with grommets along the luff so you can tie it to the stay if that system ever fails.
Design & Construction
A heavy weather jib is built around shape and durability for the conditions it works in:
- Cloth: low-stretch material chosen for the wind range, balanced between weight and durability
- Shape: optional battens to hold an effective upwind shape and deliver power consistently
- Structure: reinforced corners and strong attachment points for repeated hard use
- No reef points: per racing regulations
- Attachment: a primary luff-groove or furler system, plus backup grommets for tying to the stay
When to Use a Heavy Weather Jib
Reach for the No. 4 as the breeze builds past what your standard headsails handle comfortably:
- Wind speeds between 28 and 35 knots
- When standard headsails become overpowering
- Before conditions build to storm-jib territory
- During sustained strong winds
- When upwind performance is crucial
Racing or Cruising?
For Racing
- ISAF limits area to 13.5% of the foretriangle height squared
- No reef points allowed
- Material restrictions may apply
For Cruising
- Often a slightly smaller, easier-to-handle size
- Extra focus on durability
- Additional attachment options
Be Ready Before You Need It
A heavy weather jib expands your sailing envelope and gives you confidence when the breeze comes up — but only if it’s ready and the crew knows the drill. Practice setting it in moderate conditions, mark your sheet-lead positions, and test the backup attachment so there are no surprises in a blow. Inspect the attachment points, stitching, battens, and backup system regularly, store the sail properly between uses, and repair any damage promptly. Whether you’re racing or cruising, regular practice and proper care are what make it a dependable part of your inventory.
FAQs
What’s the difference between a heavy weather jib and a storm jib?
A heavy weather jib (No. 4) is bigger than a storm jib and built for strong but not extreme conditions. It gives you more sail area and better upwind performance, so the boat keeps driving and handling well — where a storm jib is purely about survival in the worst weather.
How big should a No. 4 be?
A good No. 4 is typically about 85% luff length and 85% LP. ISAF caps a heavy weather jib at 13.5% of the foretriangle height squared, though we think that’s more sail than most boats want once it’s really blowing.
Why fit battens when racing rules discourage them?
Because shape matters. ISAF recommends against reef points and high-modulus cloth, but for upwind sailing in 28–35 knots we believe the sail needs low-stretch material and battens to hold an effective shape — for better pointing, more consistent power, and longer life.
How do I know when to switch to it?
Look at the wind speed and forecast, the sea state, your crew’s capability, how your boat is handling, and any racing rules that apply. In general, set it once your standard headsails start to feel overpowering — before conditions build to storm-jib territory.
What if my furler or luff-groove fails?
The sail has a backup. A row of grommets along the luff lets you tie it directly to the stay, so you can still get it set and secured if the primary system fails.
