C
arinthiaAsymmetrical Spinnaker
Evolution of the modern asymmetric
The asymmetric is not new. In the 1930's the mighty America Cup J-Boats originated the concept with their "balloon" genoas, a predecessor of the modern asymmetric spinnaker. During the 1970s, the asymmetric spinnaker resurfaced onboard Intrepid during the Americas Cup defense trials, proving devastating in 25 knots of breeze! At the same time, the "cruising spinnaker" was introduced. Based on a symmetrical spinnaker with a shortened leech and the tack attached to the base of the headstay, the sails were usable on a reach but their symmetric, draft-aft shape kept them from being good performers.
In the late 1970s, Australian skiffs
accelerated development of asymmetric design. Champion skiff sailor Julian Bethwaite set
out to reduce onboard weight by eliminating one crew member. To simplify downwind sail
handling, he flew a large asymmetric spinnaker from a long, fixed bowsprit. With no pole
to gybe, the flat chute handled like a genoa and was perfectly suited for the 45 degree
apparent wind angles common in skiff sailing.
In the 1980s sail designer Tom Schnackenberg
designed a 12-meter gennaker for the Australia IV campaign which proved a winner in the
heavy Perth conditions. Dennis Conner liked what he saw and set to work experimenting with
new designs. The result were true reaching asymmetrics that were draft forward with
leeches and luffs that were more vertical in profile... a true genoa/spinnaker hybrid.
Recently, retractable-sprit
"sportboats" have been winning the hearts of sailors. Lightweight, and
very fast on a reach, the boats demonstrated a weakness in the medium airs, where they
could not match the deeper downwind angles of boats flying symmetrical spinnakers. The
1992 Americas Cup was a key to solving this design dilemma. This crossover area between
the asymmetric and symmetric spinnakers was the focus of much testing. The result was a
new class of asymmetrics with a longer luff, shorter foot and leech, added depth in
the upper sections, and the draft moved aft. This allows the trimmers to ease the sheet so
the sail can rotate to weather. This development has found its way into the sport boat
classes, effectively narrowing their window of vulnerability in medium air for this type
of boat. To link for more information about asymetrical sails -click
here-.