ASYMMETRICAL SPINNAKERS
A4 Medium / Heavy Running
Built for racing downwind in medium-heavy winds with durable construction. The A4 delivers powerful running performance in conditions where durability matters most. Optimized for apparent wind angles 115–155° and 14–30 knots.
Why choose an A4?
The A4 is designed for racing downwind in medium-heavy winds, when you don’t want to risk damaging your A2 (the most used sail on any boat). This sail has a powerful running shape, but is about 10% smaller than the A2, having narrower girths and shorter foot length. A4’s are made out of heavy cloth to keep the sail bulletproof, which it needs to be for times that the sail will collapse and then snap full.
Heavy Wind Confidence
Built for 14–30 knots
Heavy cloth construction makes the sail built to perform under repeated stress, remaining strong and reliable and handling repeated collapses and fills with ease.
Protects Your A2
10% smaller, remarkably tough
Save your most-used sail for more moderate conditions. The A4’s narrower girth, and heavier construction make it the workhorse for heavy running.
Powerful Running Shape
Mid-girth 100% of foot
Full downwind power for AWA 115–155°. The A4’s geometry delivers maximum projection when you’re blasting deep angles.
Matrix Construction: The Heart of Performance
The key to faster spinnakers lies in their construction. UK Sailmakers uses a Matrix panel layout—a radial design made up of narrow panels aligned with the sail’s primary load paths. Panels radiate from the head, tack, and clew, joined by vertical Matrix panels through the midsection. This layout minimizes distortion and delivers the strongest, most efficient sail for its weight.
Each panel is shaped on all sides to create a smooth, round sail. For one sail to be so versatile, a spinnaker must hold its designed shape without distortion. Distortion is most noticeable when close reaching. Spinnakers made from generic nylon tend to stretch through the middle, which causes the leeches to harden or hook. This reduces driving power, increases drag, and adds heel. The most effective way to prevent distortion, without using a heavier fabric, is to build the sail from performance nylon spinnaker cloth. These materials provide the strength and stretch resistance of standard nylon that is one weight heavier
FAQs
When should I use an A4 instead of my A2?
Use the A4 when wind speeds reach 14-30 knots and you’re sailing deep downwind angles (115-155° AWA). The A4’s heavy construction protects your primary A2 from damage in conditions where sails repeatedly collapse and fill.
What makes the A4 different from a “chicken chute”?
The difference between an A4 and a “chicken chute” is that an A4 is a larger, medium-heavy asymmetrical sail, while a “chicken chute” like and A5 or A6 is a significantly smaller, sturdier, and flatter spinnaker designed for extreme heavy wind conditions.
What is Matrix construction and why does it matter?
Matrix uses narrow, fully-shaped panels oriented to align threads with primary loadpaths, minimizing distortion especially when close reaching. Combined with high-performance Superkote or Airx nylon, it creates the strongest sail for its weight.
