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The main goal was to create an easy boat, simple to transport, which can be sailed on foils instinctively, hardly different than a regular cat. Further, it had to be tremendously fast.
Design and Construction:
The two students designed and ultimately self-built this 2 person hydrofoil cat, almost exclusively of carbon fibre. Working with carbon A class hulls as a starting point, and borrowing the sail plan and mast directly from the Tornado class, they were well on their way. Simulation based design, tutored by Davide Tagliapietra, focused on flight dynamics, VPP, foil hydrodynamics (CFD) and accurate dimensioning of newly built components using Finite Element (FEA).
The choice of V (surface piercing-dl)foils, devoid of the need to actively alter the lift surface, fit the simplicity and transportability concept well. The hydrodynamics of the foil at the free surface, the limits on stability, and the impact on platform beam are the compromise.
Then they went and learned how to build a boat as well. Starting with pointers and tips from a small composite boatyard Punta Manara, they climbed the learning curve. At the end, vacuum bagging substantial components came easy. For the foils and main beam, they turned to the pros at Riba composites.
Here you see just how wide the platform is, with a trampoline 2x wider than long!
Beam 4m (!)
All up weight 125kg
Mainsail area 16.35 m2
Genneker ca. 17-20 m2
Testing and Refinement:
The project was first tested in tow in late September. Huge efforts were necessary to handle the concentrated loads on the platform induced by carrying the weight and developing the righting moment on such small areas. The tensile structure originally made of synthetic cables has been completely replaced first with steel rod and then remade with carbon straps to give rigidity.
By October the boat was sailing regularly and the results were convincing. The cat was flying high and stable on its hydrofoils, easily carrying one 75 kg person and even foiling with 160 kg of crew in 12 knots of wind. Handling was easy, just as predicted. The most recent session on Wednesday of this week saw the boat flying very smoothly and easily.
Speeds over 20 knots with only the main were achieved. Tests were carried out with two crew and the genneker, pushing the boat ever harder. With the genneker, the boat was able to fly in about 6 knots of wind. Due to a lack of instruments, the best indication so far of sailing angles is that the apparent is well forward when the boat is up. Video.
Next steps for refinement will be concentrating on proper sizing and positioning of V foil fences in order of increasing high speed performance. One of the next steps will be further sail development, a new main, and a flatter genneker is also under development.
Further the team will address the righting moment limitations of the design. In addition to double trapezing, which has not been utilized to date, the mast will be significantly canted, providing a portion of the lift, allowing for a wider stance of the foils.
Regattas such as Round Texel, Bol d’Or, Multi cento and perhaps some record runs. The boat will be at the Dusseldorf Boat Show in the new year, on display at the request of the Tornado World Champion Roland Gaebler.