| The Columbia 30's flat-top main delivers more horsepower for a given rated mainsail triangle by (1) providing more sail area than traditional sail shapes, and (2) delivering more efficiency for the given sail area.
The first point is straightforward – the extra sail area on the mast is plainly visible. A rig with a flat-top main is similar in effect to adding approximately 6 feet to the mast.
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| Genuine Risk and Pyewacket off the Newport Beach Coastline Note flat-top mainsails |
As for the second point, the flat-top main's aerodynamic superiority is best thought of in the perspective of airfoil (or wing) efficiency. Mainsails on boats are basically wings, similar to those of aircraft. If traditional mainsail (triangular) shapes were the most efficient aerodynamic shape for an airfoil, then it would stand to reason that the wing tips of modern airplanes would come to a point, which of course they don't. You'll notice that the most modern rig designs ( America 's Cup boats, maxi ocean racers and so forth) employ flat-top mainsails.
Moreover, the wind velocity at the masthead is greater than the wind velocity at the surface of the water. As the mass of air flows across the water, a drag effect is created at the surface of the water that reduces the velocity of air at that surface. The wind velocity increases as it gets higher off the surface of the water, so the more sail area you have aloft, the more power you have.
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America's Cup Racers, Louis Vitton Cup 2004
Note flat-top mainsails |
Some have suggested that too much sail area aloft generates too much heeling moment. The Columbia 30 was designed from the beginning to handle the extra horsepower of this sail shape – from the low center gravity of the lead torpedo ballast to the lightweight Southern Spars carbon fiber mast. In the main, we employ a diagonal batten at the head of the sail, so when excessive wind pressure at the top of the mainsail is experienced, the top lays off to leeward, thus relieving to a substantial degree the wind pressure and the resulting heeling moment.
That said, in moderate to light air, the flat-top main provides the Columbia 30 with more effective sail area aloft, delivering greater driving power even in light air.
The Columbia 30 has a telescoping sprit at the bow, which protrudes up to 6 feet beyond the bow when fully extended, allowing you to fly a much larger spinnaker, as if you have an over-J spinnaker pole by 6 feet (J is the distance from a point at the intersection of the headstay and the deck to the forward side of the mast). Therefore, the bowsprit allows you the ability to carry a substantially larger spinnaker, which is also much easier to control given that you don't have to handle an unwieldy spinnaker pole. This extra-large spinnaker gives the boat the power to plane, and to reach speeds up to around 20 knots.
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