Sunday, December 25, 2016

Merry Christmas!

What does a windsurfing addict who has plenty of gear want for Christmas? A windsurf session!

I must have been good last year, because Santa brought some perfect windsurfing conditions today: wind around 30 mph, balmy temperatures in the mid-40s (yes, Fahrenheit, but that's counts as warm in late December), and lots of sun.

One of my favorite playgrounds for northerly and westerly winds is Barnstable Harbor. I usually sail there mid-tide, but had always wanted to explore the channels near low tide that the depth map shows:
I started sailing when the tide was just below 3 feet, and it dropped to 1.6 feet during my one hour session. Here are the GPS tracks:
I got off a lot to check the water depth - except for the 1st turn, I was able to stand every time. On the way back, I walked through some shallow areas, where even my short 21 cm fin might have been a bit too long.

The area where I sailed most is perfectly sailable, and probably would be fin down to a 0 ft tide. The water was not perfectly flat, since there are extended areas to windward where the water depth was about 0.5-1.5 ft. Since I was out alone in somewhat cold weather, I sailed conservatively, so there are no great speeds to report. In conditions like today, this seems more like a freestyle than a speed spot.

But I did see an area that looked very promising in a different wind direction: the sand bar near the top-right in the second image. It looked like a great speed strip for NE wind: the water got deep quickly enough that runs maybe 20-50 feet from the sand bar would be doable. I walked it for about 140 meters. The total length is about 500-700 meters, with a possible approach from choppy waters at the lower right. The best launch for NE low tide would probably be from Millway Beach, since this would me more than a kilometer upwind from today's launch in NE - a long walk at low tide against the wind! This would be a great speed spot in a NE with a neap tide; during a 1.3 ft neap tide, it should be sailable for 3 hours! Maybe we can check it out for speed next spring. Some of the other channels may work even at very low tides (0 ft and lower), although mostly in other wind directions (N-NNE and W-WNW).

Besides the lovely weather and great wind, I had another motivation to go windsurfing today: to try out my new GPS watch, the Locosys GW-60. It just was "provisionally" approved on the GPS Team Challenge, and replaces the GW-52. I find it a lot easier to use, with push buttons instead of touch areas that often do not work; it's also much more Mac friendly, and does not require Windows to download the data. The numbers I got today were very close to the numbers from the GW-52 - no surprise there, others have done a lot more testing already before the approval. But when I compared the tracks from the 2 devices, I noticed one area where they looked quite different - here's a part of that section:
What's going on?

My first suspicion was some difference in the signal processing, but then it dawned on me: it's much simpler! This part is from a walk along the sand bar, and the GW-52 (red) was on my arm just above the elbow; the GW-60 (blue) was on my wrist.  We can see my arm swings when walking, and the difference between the GPS that was closer to my shoulder and the one on my wrist. Cool! Now I just have to remember to push my hand out at the end of each speed run :-).

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