February 2011 Archive

Android + Bluetooth Servo Controller

2/11/11

We are exploring the use of our new Nexus S Android phone as a kite-based programmable wireless camera and pan/tilt controller. The first step in making this happen was to make a bluetooth connection to an RC servo controller and control it from the phone.
For extra fun, we mapped the phone’s orientation to its commands so that the pan/tilt unit tracks the phone’s rotations.

Next we will improve the app so that a user interface on a second phone or a remote computer can control the phone remotely over a socket connection. The final step will be to transmit both low-resolution, low-latency “preview” images and full-resolution images from the phone back to its client.

Kitefoiler Tow Test – Feb 10

2/10/11

We towed the Kitefoiler again today. We added a pulley system that allows us to adjust the J-foils from the steering position at the stern of the boat. These pulleys worked very well. The port foil was sticking and not moving correctly as it did yesterday, but due to the glassy bay conditions, this did not prove a problem for our very short test. Henry visited the shop today and rode on the boat with Don and Joe.

Three Kitefoiler tow points were tested, each with the powerboat pulling at at 45 to 60 degree angle. The graph shows the measured forces and speeds for each tow point. The 3rd point appears to have reduced the load over the 1st. […more]

Kitefoiler Kite Test – Feb 9

2/9/11

We took the Kitefoiler out today for a second test with a kite. We spent a bit of time hunting for wind, but found a reliable source east of Alcatraz and Angel Island. Dudu helped launch the kite, then left the Kitefoiler so Don and Joe could pick up speed. He later returned to the Kitefoiler to see if his extra weight would make it easier to steer at top speeds, which it did. We achieved the fastest speed yet for this boat, 27 knots. The kite bridle looked loose in one place, although it did not cause kite steering difficulties.

First Kitefoiler Kite Test – Feb 4

2/4/11

We performed the first Kitefoiler test with a kite today. Greg Ketterman, designer of the Trifoiler, joined us on the test. Prior to testing with the kite, we towed the boat to the city and back around Treasure Island to make sure that everything was working as expected. The foils were a little looser than we would have liked, but the wind picked up, so we tried the kite anyway. Despite the mediocre wind speed, the boat performed very well, foiling consistently with two crew members in the area between Angel Island and Chrissy Field. After returning to the shop, Joe disassembled the cassettes and found the problem with the foils–the stress on the bearings had caused them to fall […more]

Kitefoiler Tow Test – Feb 2

2/2/11

Another tow test today after Joe and Damon repaired and modified the J-foils. We experimented with different crew weights and different positions for that weight, at various speeds. The adjustments seemed effective–the boat was stable under all parameters.

We put different GPS and tow tension sensors on both the Kitefoiler and Protector this time so that we could compare several sensor options. The load cells on each boat were in general agreement. The GPS receivers often reported different speeds, but this reflects the relative motion of the two boats. The peaks in line tension appear when the speed of the Kitefoiler drops enough for it to drop down from the foils. The segment in the attached graph shows the boats’ […more]