William Sunnucks Pioneers Catamaran Canted Foiling – January 2015

Members will be interested to learn that William Sunnucks (Peterhouse 1974) has been pioneering the development of canted T-foiling for catamarans in the UK. William’s 20-foot Vampire is the current test bed, and the 20 degree outwards cant of the foils is designed to give least drag, imitating the windward heel of a Moth sailing upwind.

The windward foil can be hoisted out of the water without disconnecting the control wand mounted on the bow – a gull wing system that may well be another first. The gull wings have the other advantages listed below.

  • There is no need to insert the foils from the bottom of the boat, allowing it to be easily assembled and launched from a beach.
  • Light wind performance is enhanced by withdrawing the foils completely and using conventional daggerboards.

catamaran foiling
Vampire foiling at speed – 20 knots has been consistently attained downwind

diagram of foils
Diagram showing arrangement of foils

Development Team
William has been seeking a way to combine moth and catamaran technology since learning to sail a Moth in 2009. Further inspired by the 2013 C Class championship in Falmouth, he drew up the canted T-foil concept to be built on the Vampire as the test bed.

The concept was developed by fluid dynamics expert Kevin Ellway, designer of the Exocet International Moth, the first Moth to be designed completely using mathematical models. Scores of virtual designs were “flown” before putting the final design into production, and the same general approach has been taken with the Vampire project. Kevin is now working on rig developments to get the best out of the Vampire platform.

The foils have been built in Brightlingsea Essex by Graham Eeles a specialist boat builder engaged in a number of innovative projects. He has converted the desktop theory into strong and practical foils and has been acting as coach on the early test outings.

Enquiries to William Sunnucks, East Gores Farm, Coggeshall CO6 1RZ; William@sunnucks.co.uk; 07771 940763.

Some Additional Notes on Catamaran Foiling
T-foils were first fitted to a catamaran by the “Off Yer Rocker” C Class team in 2007. The foils were vertical and both remained in the water. The boat flew, but was never thought to be fast. More recently the Whisper project supported by Southampton Solent University has been following this line of development.

The 2013 America’s cup saw 72 foot catamarans foiling at 40 knots downwind. This L-foil technology was also applied in the C Class Championship, “the LittleCup”, at Falmouth in September 2013. Commercial production has started using the same principles on the Flying Phantom and Nacra FCS.

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