Kaimusailing

The boatyard is still without internet, ever since a lightning storm that took out other things and left half the boatyard dark. It looks like the Comcast router’s ports are fried.
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The hot weather, heat index of 123 today, means working in the shade. Too hot on deck and too hot down below in the hulls, looking for small projects that can be done under the crossdeck in the shade.
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The recent America’s Cup racing has everyone talking about foils, just like last time. I googled L’hydroptere, the French foiling trimaran that set a few ocean sailing records. I was surprised to find out it had been abandoned after a record attempt transpacific to Hawaii. Not abandoned at sea, abandoned in Honolulu, out of funds to pay dockage and port fees. It is also surprising that the boat is over 20 years old.
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Instead of the complicated L, J, or inverted T shaped foils that we’re seeing on other sailing craft, L’hydroptere was using simple slanted boards that are on about a 45 degree angle to the water. This arrangement had opposing foils, so the thrust of the port foil, for instance, would be towards the middle of the boat and upward, while the starboard foil would be thrusting from the opposite direction, but also upwards. The port and starboard components of the foils’ lift would cancel out, leaving the upward components of the force raising the boat out of the water.
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The downside of this arrangement is lift that is wasted, only part of the lift of the foil is actually lifting the boat. And since lift always has an amount of drag associated with it, the drag of the two foils is much greater proportionally than the drag of the type of foils used on the America’s Cup boats. Also the angled foils are generating lift all along the length of the foil, and the section near the surface of the water is susceptible to ventilation, what some call cavitation, when the low pressure surface of the foil sucks air down and then the foil suddenly loses lift, it is no longer using water pressure, it is partially covered in air.
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In the old days of windsurfing a racing technique for working to windward with a course racing board was to tip the board slightly to leeward so that the lee rail was in the water. This surface of the rail would help develop some leeway prevention. This tipping of the board also tipped the fin at the back enough that it would generate a bit of vertical lift. At high speeds the board would go faster and faster as more of the board was lifted out of the water, reducing drag. When the amount of lift generated grew to a high level, the fin would ventilate, and the feeling was that the fin had broken off. The first time it happened to me I dropped into the water as the board washed out to leeward. I was sure the fin was gone, but when I checked, there it was. I learned after that to pull the tail of the board under me when it slipped out, then steer a bit downwind taking the pressure off the fin. The flow of water would reattach to the fin and I could add more pressure.
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I haven’t yet made the rudder/daggerboard blades for the BFB proa. Now I’m thinking, what if I added a bit of angle to them. The proa is light and meant to sail fast. Perhaps it could generate some lift and go a bit faster.
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The image is of July 4th heat in the town of St. Marys, heat index of 119. A large turn out of folks braved the heat waiting for the massive fireworks display later. We can see them from the boatyard, so that is where we will be. Rocky, boatyard owner, manager, and chief crane operator was digging a ditch to bury new electrical cable. They were not in the shade doing this backbreaking work. They did take a break for a soda.