graphs

K2 Foil Offset vs Speed

9/16/13

We are now recording the foil actuator positions during tests. Looking at tow and kiting test data from last Thursday, we’ve plotted the relationship between the T-foil setting and the boat speed. The T-foil is controlled by the helmsman and is used in conjunction with the J-foils to control the pitch and ride height of the kiteboat. A relatively simple relationship between the two (as we see here) suggests that we may be able to automate the boat’s pitch stabilization, which would free the crew to concentrate on other tasks.

Rear Line Loads

3/7/13

We’ve been curious about the distribution of rear line loads, and have recently been collecting load data from both lines. The result is a bit of a surprise. As expected, the “top” rear line has a higher load, but the difference between the top and bottom lines is smaller than anticipated: typically only a few kgf, out of a total rear line load of up to 120 kgf.

The top attached histogram shows the distribution of the total rear line loads. The second histogram shows the difference between the right and left lines when on a starboard tack, and the third histogram shows the same for port tack. This data comprises the entire test on March 5 during which the […more]

K2 Speed vs. Load

11/16/12
Towing power as a product of force and speed.

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]

Kite Inflation Maintenance System

11/15/11

Jamie has augmented our kite inflation controller, which monitors a kite’s inflation levels and maintains a designated psi by inflating the kite further, in case of a leak or temperature change, for example. The new electronics add precise pressure measurement, a radio link to the ground, and remote pressure control. In the photos, the system is inflating a kite section to 8 psi. Our smaller kites take higher inflation pressures, up to 9 psi, whereas the larger kites take lower pressures, 2-3 psi. This system is splashproof, but not waterproof, which is sufficient now that our launch and retrieval procedures largely keep the kite out of the water.

The graph shows the pressure as the small kite section is inflated […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.

KAIView Map Update

5/2/11

KAIView 0.2.6 contains several improvements from the last few weeks, particularly in the mapping component and its integration with the other data displays. The overall goal has been to make the mapping window more useful as a primary interface to the data, instead of just a supplement to the graph display. By default the map window is now larger, the data that it already displayed is easier to read, and a legend shows the geographic scale and the meaning of the color-coded data.

In addition to these visual changes, there is now better correspondence between selections made in the graph window and those made in the map. Right-clicking and dragging in either view will create a selection that is shown […more]