SYMMETRICAL SPINNAKERS
S4 — Medium / Heavy Running
Built for heavy-wind downwind racing when you need bulletproof reliability. The S4 delivers powerful running performance in conditions that would risk your primary spinnaker. Optimized for apparent wind angles 120–170° and 14–30 knots.
Why add an S4?
The S4 is designed for racing downwind in heavy winds when you don’t want to risk your S2 (the most used sail on any boat). This sail has a powerful running shape but is about 10% smaller than the S2, featuring narrower girths and a shorter foot length. S4s are made from heavy cloth to ensure bulletproof durability for those moments when they collapse and snap full in challenging conditions.
Heavy-Wind Power
14–30 knots true wind
When conditions get rough, the S4’s robust construction handles repeated collapses and fills without damage, keeping you racing confidently.
Bulletproof Durability
.9 oz. to 1.5 oz. heavy cloth
Built with heavier materials than your primary chute, the S4 withstands the violent loads and snapping fills that come with heavy-air downwind racing.
Risk Management
Protect your investment
Save your S2 for optimal conditions. The S4 lets you push hard in heavy air without worrying about expensive damage to your primary spinnaker.
Matrix Construction — The Performance Difference
The heart of faster spinnakers is the construction method. The panel layout UK Sailmakers uses is called Matrix, which is a full radial layout that features narrow panels, each oriented to better align the threads in the cloth with the primary loadpaths in the spinnaker. This is the most effective way to reduce distortion and make the strongest sail for its weight. Each panel is shaped on all four sides in order to create a smooth, round sail.
Cloth Options
An S4 can be made of generic 1.5 oz. nylon because a little stretch doesn’t hurt in high winds. If maximizing performance in the lower end of the range is important, a .9 oz. performance nylon can be used to maintain shape and responsiveness in transitional conditions.
FAQs
When should I use an S4 instead of my S2?
Use the S4 when wind speeds exceed 14 knots true or when conditions are gusty and unstable. The heavier construction protects your primary S2 from damage while maintaining powerful downwind performance.
What’s the difference between .9 oz. and 1.5 oz. cloth?
The 1.5 oz. generic nylon is more forgiving in heavy air where stretch isn’t a problem. The .9 oz. performance nylon offers better shape holding in the 14-18 knot range for maximum versatility across the S4’s wind range.
What makes Matrix construction better?
Matrix uses narrow, four-sided shaped panels aligned with the sail’s primary load paths. This full radial layout reduces distortion, maximizes strength-to-weight ratio, and creates a smoother, more aerodynamic shape than traditional construction methods.
Can I use the S4 for cruising?
While designed for racing, the S4’s durable construction makes it excellent for cruisers who sail in consistently windy areas or want a bombproof downwind sail for offshore passages.
