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Thursday, September 26, 2013

IMOCA 60 Shape and America's Cup 2013

                                                     Ellison: "Sailing has been changed for ever".
When sailing is more like flying, with such sophisticated machines, how are the technologies adaptable to more mundane venues?
America's Cup boats have a way to continuously improve elements of sailing, and even cruising. But, when we have all of sudden such a leap forward, where new boats; catamarans, wing sails and foils are thrown into the mix, what is going to happen?
The obvious is that the benefits are going to go to cats and trimarans. But, what about regular sailboats? I will leave alone the articulated wing sail, they are not manageable, because of reefing problems, but I think there are possibilities in the foiling area.
A monohull is always looking for stability, so deep keel, ballast and beam are the usual answers. Now, with the new technologies like DSS, which is an outboard deployed foil on a horizontal plan, and the AC foiler, which is an inboard oriented planing board, either concept, provides more stability and righting moment.
To work, we have to have speed, therefore the sailboat will have to be of light displacement, with a fast shape and low deadrise. My attempt is to show how such a configuration might work, of course all is in the details, and I do not pretend to solve the entire matter. It definitely would require very long and elaborate studies, model testing, strong engineering, but I am throwing things in the ring to see where it all lead.


Fast boats are long, light and lean. I choose for this base study the Imoca 60 in its latest form. With a dinghy shape, twin rudders, appendages and keel, the boat is an interesting monohull laboratory. A Class 40, or Mini Transat could be other examples of hulls where the merits of foiling on modified daggerboards could be
studied and compared for speed.
Where to start? Now that we have decided on a hull, the nest step is to describe what I have in mind.
The system has to rely on deployment and retraction of the blade. So, I am starting with the foil itself and I use the present configuration of the daggerboard, bend it at mid distance even before trying to work out surfaces and lift necessary to achieve the result of lifting the hull some ways. Because one of the question remains: how to have the apparatus to match the hull shape when retracted to minimize turbulence at low speed, without impairing the foil shape. Fortunately, the body presents nearly flat surfaces in the area and the daggerboard-foiler can be inclined perpendicular to the hull and designed in such a way that the bottom matches the small curvature of the hull itself. But what happens when you extend the lifting body ? There is a hole. The idea is to build a second blade, contained within a box to fill in the gap and keep flush the integrity of the hull.