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S4 Medium/Heavy Runner – Racing spinnakers
AWS 14-30 kts
Mid Girth 95-100% of foot length
Almost Full Girths and reduced shoulders
.9 oz. to 1.5 oz. cloth
The S4 is 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, by having narrower girths and a shorter foot length. S4’s are made out of heavy cloth to keep the sail bullet-proof, which it needs to be for the moments that they will collapse and then snap full.
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.
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 import, a .9 oz. performance nylon can be used.
Spinnaker Painting Program
Use this program to create a custom look for your new spinnaker or cruising spinnaker. Click here to go to the Spinnaker Painting Program.