Sailing Boat Design

ACT-420

New 420 Class Design

The new 420 design was completed and built at Tsujido and the first hull was launched in June 2014. The same scientific approach as the Snipe was applied to the design with help of the feedback from the Snipe and the performance analysis of 470s in the past. The rule specifies some restrictions with some allowances on the hull shape. It was clarified from the CFD study that there would be 10% drag difference in the allowances. Since the optimized hull shape is different at every boat speed, the extensive CFD simulations were carried out at different boat speeds for various hull shapes. The final hull shape was designed to be less drag at every condition than the base hull which was evaluated as a good hull in the existing 420s and furthermore fine tuned in the detail shape to be more competitive.
The best fore and aft trim depends on the boat speed and then it is necessary to optimize the hull shape at its optimum trim. At 6.5kt boat speed, for example, the best center of gravity position is around 1.6m from the transom and if you move the position by 100mm forward the drag increases by about 6%, which means it is necessary that the hull shape optimization should be carried out at its best trim at each boat speed. The CFD simulation capability to simulate the planing attitude accurately is required for the hull shape optimization.

The following are the visualizations of the 420 boat at 6.5kt boat speed by CFD

The deck shape was designed to be good for crew work and simple as possible from the various experiences at Tsujido and opinions of professional sailors.
The hull and deck plugs were constructed by NC milling to be very accurate to the design shapes.
The actual sailing performance was evaluated by 2 boat testing of the North Sails Japan technology which enables real time evaluation with the GPS data and sail shape capturing data transfer. It was revealed that the new 420 boat was faster by about 2% which is almost the same as CFD results.
Please contact to Tsujido for detail and ordering.
Tsujido Kako
North Sails Japan

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