The new J Class sailing yacht Lionheart
by Oliver Dewar
Lionheart was the third new J Class to be launched since Harold S Vanderbilts successful Americas Cup Defender, Ranger, took to the water in 1937. In 2003, a replica of Vanderbilts Super J Ranger left the Danish Yacht boat yard and immediately began racing, followed six years later by the J Class replica of Endeavour II, renamed Hanuman, leaving the Royal Huisman Shipyard and competing successfully against Ranger just four months after launching. With the launch of the Hoek Design_ Lionheart_ from Claasen Jachtbouw the stakes have been raised again.
The meeting between the replicas of Ranger and Endeavour II was significant when the duo met in 1930s, Ranger _was victorious, but the more recent _Endeavour II-replica, Hanuman, triumphed on the water 90 years later.
For Andre Hoek, a detailed research program focused on testing the various, original J Class designs revealed that Lionheart was one of the best set of designs available for an all-round, high-performance J.
When an existing client came to us for a third yacht, his main interest was a new J Class yacht, says Hoek. He asked us what we would do if we were to build a new J and that led to a proposal to first do a dedicated research project to determine what would possibly be the best performing J Class yacht.
We proposed to analyse the theoretical performance of all existing J Class lines and to develop a dedicated Velocity Prediction Program specifically geared to J Class hulls with long keels, the marine architect explains, as the existing VPP software is all for round-bilged hulls with fin keels and spade rudders, which are totally different hydrodynamically to a long keel hull with a rudder that forms a flap on a long keel.
The proposal was accepted and a new Velocity Prediction Program for typical J Class hulls was developed together with Peter van Oossanen (of wing keel and FDHF fame).
Tank test data of a 20 foot long model of the J Class _Rainbow _was used to calibrate the mathematical formula of the VPP program. With this new software, initially all possible Super Js (with a maximum waterline length of 26.51m) were analysed for performance both on line honours and handicap.
The five best-performing hulls from this research were then analysed using computational fluid dynamics software (CFD). The CFD analysis confirmed the VPP findings and the search was narrowed to three hull designs:
One of the eight tank-tested designs commissioned by Vanderbilt from W Starling Burgess and Olin Stephens for the Ranger77-F project;
Svea, designed by Swedens Tore Holm in 1938 but never built; and A Frank C Paine design that didnt progress beyond the drawing board.Of the final three, Lionheart showed the best overall performance, Hoek reveals. The Paine-designed Atlantis is a very good light wind and downwind boat and Svea is the best upwind boat.
Furthermore, the research proves that the_ Lionheart_ design is faster than the lines chosen for the original Ranger a choice that was not due to flaws in the combined wisdom of Vanderbilt, Burgess and Stephens, but purely that tank testing with models of just under a metre in length is now known to supply inconclusive and misleading data.