The tow test on Wed Nov 14 provided some insight into how much force is needed to pull our kiteboat at a range of speeds. By measuring the tension of the tow line and plotting it against the boat speed, we can infer the approximate force that a kite would need to generate to pull the boat at those speeds. The first attached plot shows only the tests with a crew of three, for which the maximum sustainted speed was 38 knots. The second plot shows the towing power, calculated as the product of the force and speed. The polynomial fit (red and green lines) may be helpful to understand the density and trend of the collected data, but should […more]
Today we tow-tested K2 to see how well the boat performs at very high speeds. Specifically, we wanted to determine the cavitation point for our foils. We are using a conventional section for the foils, which means that our foils are designed to operate at speeds at which they do not cavitate. The cavitation point of a foil is the speed at which the water passing over it turns to vapor; cavitation on our foils would prevent them from providing lift and the hulls would drop into the water. Most foils utilize a conventional section, but certain high-speed vessels utilize a caveating section, which allows them to continue to provide lift, even while cavitating. We experimented with cavitating foils on K1–the last iteration […more]
Today we headed out to test several new components on K2. We tested the new motorized winch for the first time, and we used a new car (which houses pulleys and load cell) under the seat, which was an upgrade from the former aluminum car. We did not plug in the load cell but structurally tested the system. The new winch worked excellently. Dudu flew over in his helicopter, and Gino Morrelli and Bruce Sutphen, visiting boat designers, joined us on the kiteboat and Protector. The kite seemed to be deflating the entire time, perhaps as a result of the inflator accidentally turning off during the test. Despite this behavior, it was a great test. We hit our fastest K2 speed of all […more]
In 1997, soon after he became involved in kitesurfing, Don attached a kite to a boat for the first time. It was a Hawaiian surfing canoe. From 1997 to 2006, he worked with a team in Hawaii to develop kites for use with surfing canoes, small catamarans, and large sailing cats, and the team used those boats for wave-riding and to complete several island crossings. In 2006, the project moved to Alameda, where we began experimenting with hydrofoil test platforms and eventually transitioned to building our own platforms from scratch.
We headed out for another test today, but the wind came and went in gusts. After the kite fell out of the sky during a lull, the crew discovered that the kite had also already been deflating due to a faulty connection between the leading edge bladder and a strut bladder.
As polyurethane ages, it shrinks, and that meant that the bladders in this older kite had shrunk in storage. An octopus valve connecting the strut to the bladder had failed as the polyurethane fittings pulled it apart, causing a leak. Don fixed this as the other guys untangled the line. By the time of relaunch, there was still no wind, so we headed back to the dock. Tomorrow we’ll […more]
We got a bit of a late start getting out on the water, launching as the sun was setting, which made for some beautiful photos. It was a short test, but it went smoothly. We brought out the 50 sqm kite again. Before launching the big kite, we briefly launched a blue Dacron lifting kite from the Protector. We had hoped to film K2 and the big kite using the rokkaku, but it turned out to be a flawed model and we could not keep it in the air consistently. Allen Smith joined us on this test. He contributed a stabilized GoPro mount, which we mounted on the stern pole, but it proved to be less effective than the fixed […more]
We took the boat out for another evening test today. We got the boat foiling nicely with four guys and the 40 sqm kite in low but steady wind. We also used a new line camera mount, the first time we’ve used a line camera in a while. Allen Smith joined us on this test.