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The new J Class sailing yacht Lionheart

Lionheart was the third new J Class to be launched since Harold S Vanderbilt’s successful America’s Cup Defender, Ranger, took to the water in 1937. In 2003, a replica of Vanderbilt’s 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 Sweden’s Tore Holm in 1938 but never built; and A Frank C Paine design that didn’t 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.

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