Spinnaker 50 Design Considerations/Sailing

This topic was started to respond to Gregs questions and statements under Matthew Lingley’s proposed Offshore Model Design. There may be some unavoidable repetition of material covered elsewhere in this section and on this forum to provide this information.
Only two of the ten S 50 owners sometimes use this forum or the other one(as fas I know): David Goebel and Todd Drake–they may or may not choose to post here.
Greg mentioned something to the effect of the Spinnaker 50 compared to an AC boat presumably meaning IACC boat. It actually bears no resemblance whatsoever to an IACC model(or an AC modelfor that matter.) and was never intended to. The boat was designed as a Strict One Design to provide close racing using a spinnaker. It was not designed to compete with a Marblehead and no compromises were made to allow it to be competitive with a Marblehead.A state of the art spinnaker boat is possible now that could directly compete with a Marblehead-upwind and down,however.
Total sail area upwind is 1200 sq. inches which is a little more than a Marblehead and offwind sail area is close to 2000sq.inches. Since the 50 was designed(about 8 years ago or more) new and much lighter ways of installing a spinnaker have been developed; the S50 weighs about 13 lb’s and has a spinnaker that can be set or doused in less than three seconds. The spinnaker can be carried as high as a beam reach and gybed at will inless than one second and without collapsing the spin-with practice. Further, the sail can be hoisted with the boat head to wind to allow it to backup quickly shedding weeds.
The sailplan of the 50 was carefully worked out to allow the hoist to be at the right angle so as to lift the boat when the spinnaker was hit by a gust-and to present a constant lifting force on the bow-THIS IS THE MOST CRITICAL PART OF THIS SPINNAKER SYSTEM! If the hoist were higher the boat would pitch pole in winds over 8 mph; as it is since the spinnaker develops so much lift it will sail in a stronger wind deaddownwind with the spinnaker up than with it down.
The jib on the 50 is intentionally small to prevent it from inteferring with the spinnaker. Generally, in most conditons because of the double slot formed between the jib and main and the jib and spin it is faster to tack downwind.
Compromises in design were made to allow the use of only one spinnaker for the widest range of conditions.
On a development class the system could allow multiple spinnakers changed when the A,B and C rigs are changed. A masthead spinnaker is possible in light air as long as the hoist is lowered in winds over around 7-8mph. The S50 uses a symetrical spinnaker because it is easier to set up and less costly than is an asymetric .
The underdeck part of the spinnaker system includes a tube that runs aft 1/2 the hoist of the spinn. and the front end is a molded unit glassed into the deck during layup. Beacause of the relatively wide beam of the boat and the fact that the spinnaker tube runs to one side inside the boat there are two drains(vs one on A1) that remove water from the spinnaker stowage tube.

Doug Lord
–High Technology Sailing/Racing