kiteassist

Comparing Three Wind Sensors

5/6/11

We have been concerned about the accuracy of the wind sensor that we have been using on the Kitefoiler, an Airmar PB200 ultrasonic anemometer. Today we took this sensor to Crown Beach, along with our old standby, a Maretron WS100 (also ultrasonic), and a handheld mechanical anemometer. In summary, the new Airmar sensor was found to report wind speeds that were 23% higher than the other two sensors, which tended to be in good agreement with each other.

We will do further testing to determine if the wind direction relative to the sensor makes a difference, if the sensor is dirty, and if it is broken or operating outside of its specified accuracy range. The graph shows the measured correspondence […more]

Lifting kite testing: rok G9 & fled – May 6

5/6/11

Today we took the inflatable lifting kites out to Crown Beach to test them with Armand. Dudu and Armand flew the most recent rokkaku, the G9, in about 15 knot winds and used it to lift a payload of sand. The front spar on the G9 kite is fused to the center strut, while the back spar is free to rotate, as on the G8 kite. There is a tube that links the back spar to the center strut at the cross point, and this allows the entire kite to be inflated via one rear valve. We loaded the kite with sand bags until it began to deform, and then observed the flight pattern with that weight suspended from the […more]

Logger as WiFi Access Point

5/4/11

The box that we use for logging boat tests contains a very small linux PC that connects to sensors, records data, and manages data displays. Connecting to it remotely from our phones and laptops to verify that it is operating correctly, to control its operation, and to have a rich real time display of all recorded data is an advantage. To this end, it now functions as a wireless access point, which was not possible on the original hardware using readily-available linux builds. Now that this is working, we can connect via any wireless device and be directed to a web page hosted on the logger.

GoPro Remote Control Update

5/2/11

In the background we have been incrementally working on making our GoPro cameras remote-controllable via the ZigBee wireless protocol. The objective is to make a minimally-invasive modification to the camera that allows us to detect which cameras are present, turn those cameras on and off, and to initiate synchronized recording by multiple cameras. We have now accomplished some subset of these goals using each of three different interfaces to the camera: external “hero-bus” connector, internal serial port, and direct wiring to buttons and LEDs.
However, each remote interface approach solves only part of the overall problem or introduces new complexity, so testing continues. We are now fabricating a PCB to implement any combination of the approaches in a camera […more]

Rokkaku & Android camera setup test – Mar 31

3/31/11

We took the “good” kite from the last two rokkaku tests out to the parking lot to compare its performance to that of the original carbon spar kite in very low wind.

Additionally, Jamie debuted his Android phone camera system by attaching one phone, in a padded cardboard box, to the kite line of the carbon-sparred kite and letting it out about 75m. In his hand he held another Android phone, which displayed the image taken by the lofted camera.

Meanwhile, Don and Dudu discussed weight differences in the two kites and experimented with bridle positions on the inflatable one. We also briefly attached a GoPro to the line of the inflatable kite to get an aerial view of the […more]

Rokkaku kite test – Mar 28

3/28/11

Dudu, Jamie and Renata tested two Rokkaku kites today, both with inflatable cuben fiber struts. Kite A was the best one from Friday (#4), which had 50% of the original curvature, 90% of the original diameter, and long battens. Kite B was a new one with the same tube diameter, 75% of the original curvature, and short battens.

From Dudu:
Both kites flew well with the same stability and held all gusts with no issue. The 50% kite still had better flying angle.
This test proved we can have smaller battens at strut tube tips and still spread the loads. This can save weight and storage.

Rokkaku kite test – Mar 25

3/25/11

We took four different rokkaku kites out to the parking lot today to compare their performances. Kite 1 (photos 1, 8, 12-15) was the original rokkaku with all-carbon spars. Kite 2 (photos 1, 8, 11-12) was similar but with a modified spine. We also hung a camera off the line of this kite to film Kite 3. Kite 3 (photos 1, 8-10) had an identical canopy to 1 & 2, but instead of carbon spars, it had inflatable spars made of cuben fiber. The inflatable spars had the same curvature as the original carbons spars. Kite 4 (photos 3-7) was also made from an identical canopy and also had inflatable spars made of cuben fiber. However, these spars were 90% […more]