J Class Association
The J Class Association (JCA) was founded to protect the interests of the Class, present and future.
To keep the J-Class fleet and races alive and to encourage new build yachts to enter the field, new Class rules were established for the construction of Replica Rebuilds from original plans.
One of the key drivers of the J-Class revival was the decision of the J-Class Association to allow aluminium and other materials to be used as a hull construction material. This reinforced the renewed interest among owners to build J-class yachts.
After a performance analysis by Gerard Dijkstra of the existing J’s as well as the designs that were allowed to be built under the new JCA rules, a specific J Class handicap system was developed in order to enable all yachts built to the J Class designs to race against each other regardless of size, sail area or hull construction.
The new rule is a VPP (Velocity Prediction Program) based rating system which puts limits to the performance. The aim of the JCA and the rule is to bring fair & close racing to the fleet and to give all designs a chance of winning on a handicap based system.
J Class Rating
In the 1930s, the J Class yachts raced under the Universal rule, this rule used waterline length, displacement and sail area to control the racing condition and rating of these Formula One racing yachts of their day.
Now in the present day, there is mixture of refitted surviving yachts along with a number of new yachts built to original hull lines with more yachts in build now and planning to be built in the future.
These yachts can no longer be raced in their original designed conditions due to their luxury interiors and the need to adhere to modern marine standards and as a result their speed potentials are different. Their performances are also determined by their overall design and it was decided to use a modern velocity performance prediction technique to better estimate each yacht’s performance across a range of wind speeds and course types to produce fair racing and rating.
This method uses a computational model of each yacht to incorporate the effects of hull parameters on the hydrodynamic forces, mast and sailplan parameters on aerodynamic forces. From this tool, time correction factors are developed to be applied to each yacht’s course time.
The relative differences in performance between the majority of the Js is small and this approach produces fair rating that encompasses the major influences affecting boat performance.