Monday, April 7, 2014

Put it behind you!

In windsurfing, we often do the right thing for the wrong reasons, and the wrong thing for the right reasons.
Andy Brandt showing how to jibe


In the past two years alone, I jibed more than ten thousand times. Overall, the number is probably at least 25,000 times, maybe even 50,000. You'd think I jibe really well. Ha! You'd think wrong, sir!

After a recent session with mediocre jibes, I posted a few pictures here. My big question was: why do I pull myself up to the boom just before I jibe? I know it's wrong, so why do I keep doing it? Armed with my GoPro, Clew-View mount, and 5 Hz Flysight GPS, I set out to find out two days ago. Before I show you a video, I have to show you another picture, though:
Dasher showing how to jibe
This is Dasher in his "12 Step Jibe" video. I think this is a great instructional video. He teaches the jibe almost the same way as ABK does. But in many of his jibes on the video, he does not oversheet the sail nearly as much as Andy does in the first picture. The picture shows the sail when it is maximally sheeted in. He has another windsurfer in his videos who sheets in much more dramatically:
Another jibe from the Dasher video
This stance is much more similar to Andy Brandt's stance in the first picture. In the video, Dasher says that the more aggressive laydown style jibe is for smaller boards and really windy days. That's a bit different from what Andy says: he often tells me to push the sail down and fully out of my line of sight, even in mediocre wind. If I'd just listen to Andy and do what he says, this entire post would not be necessary... 

When I sailed two days ago, the wind was around 20 mph. I sailed around mid-tide at Kalmus, so there was some noticeable chop, but nothing terrible. I was well powered on my 7.0 m freeride sail and 110 l freeride board (I used a big 30 cm week fin). Here's a video of the one jibe I planed through nicely:

I planed out of it, but there are many things that I did wrong. Don't let that distract you! We will not be giving out prizes for the person who can find the most things to improve.

In the third, really slow showing of the jibe in the movie, it flashes and zooms in twice. The first time, it shows my surfing stance as I approach downwind. In my opinion, it is a reasonable good imitation of what Dasher does in the picture above. But a second later, I pull myself up to the boom! Bad idea. I know that the front arm must stay long. So why do I do the pull up?

When I looked at the GPS data for this jibe and compared them to the video, I got some important clues. Here's a picture of the GPS tracks:
The minimum speed in this jibe is when I am on a new beam reach, about 4 seconds after passing dead downwind. That was my first indication that I had flipped the sail too late. Looking back at the video, I saw that my feet switched a bit too late, too. Ideally, the new front foot should go forward at the same time as the clew opens up to clew first; in this jibe, there was a noticeable delay.

That means that I did my pull up when I was about to go dead downwind. The GPS shows that I was going about 19 mph, about the same speed as the wind, so there was no pressure in the sail. I knew it was switch the feet, but I obviously was still hanging to far to the back - I had to pull myself forward to get balanced over the carving foot. This must happen to me quite often, the pull up to get forward is something I do automatically, without even being aware of it.

Now, ABK Christopher's suggestion that timing is extremely important in jibes came into play. I did let the sail power pull me in from the hanging position to a more surf-like stance; however, I did not let it pull me in far enough, so I had to do some of the pulling afterwards. That extra pull then delayed the foot switch and sail flip.

Following the Dasher and ABK advice to "let the sail pull you in" is both scary and tricky. If you give in too fast, the sail will pull you into water; if you pull in too slow, you may find yourself a bit too far back, like I did. Getting the timing just right requires both experience and feeling; add some chop to the equation that changes your board speed and sail pressure, and you may just need a lot of experience.

So far, so good - I now had a pretty good idea why I was doing the stupid pull up thing. But how do avoid getting into this situation in the first place? Developing more "feeling" by practicing another 25,000 jibes does not seem like an attractive solution. But what about Pete's suggestion to pull the sail behind me, like Andy and Dasher's helper do in the pictures above?

I know this looks cool, but I rarely ever did it before. Andy says I should do it, so I should; but I never bought the reason he gave me: that this interrupts the laminar flow of air over the sail. If I am going downwind at the same speed as the wind, there is no more air flow over the sail, no matter where it is!

But now, I see a much better reason: when you push the mast down and pull the clew up behind your back, you can completely take the power out of the sail when you want. You can let the sail pull you up rapidly without having to fear that power remains in it longer than you thought. This allows you to get into a fully balanced, forward-oriented position not only sooner, but also more reliably.

Having all this figured out, I was dying to test it on the water. Yesterday's wind forecast was horrible, but fortunately, nobody told the wind, and it picked up to low 20s around noon. I had some extra motivation to go sailing: Dean, the fastest guy on our speedsurfing team, is currently on Cape Hatteras, and he's alway producing wicked fast speeds. I so wanted to be able to get a session in to back him up, so his speeds would count for the monthly ranking!

So I packed the slalom boards into the van and went. No windsurfers at Kalmus, so I started at Sea Street Beach, closer to the Kennedy Slicks. The tide was not ideal - just about 1 foot, and coming in slowly due to a neap tide, so the Hyannis Port Harbor breakwater looked extra tall. But the chop near the launch was too big for speed, so I cruised up to the Slicks, anyway. I was on my 117 l slalom board with the 7.5 m Matrix sail, exactly the same gear as what I had used in my recent "mediocre jibes" session. Same spot, same flat water, very similar wind - what better test?

I focused on making sure to move the clew hand back far, and really sheeting in during the jibe entry. Very quickly, I learned about another reason to pull the clew hand up behind you: when just sheeting in normally, the clew would drag in the water during the jibe, creating interesting situations. Pulling it up behind my back solved the problem nicely. Pretty soon, I was planing out of many jibes - a definitive improvement! Runs were about 600 m long, so I got to practice a jibe about every minute.

When the wind picked up a bit and the gear felt big and draggy, I sailed back downwind to the van and de-rigged. I wanted to go out on smaller gear, but had no desire to sail 1/2 mile upwind through chop again, so I drove to the harbor, and rigged there. Out came the XFire 90 and my old Matrix 7.0, which feels at least a meter smaller than the (newer) 7.5.  Back on the water, the fun continued for another 40 minutes. It seemed I was planing out of most of my jibes on the smaller gear! I stopped when I started making typical "getting tired" mistakes.

The GPS track analysis at home showed a rather large improvement. I used the "jibe analysis" feature in GPS Action Replay Pro, looking at minimum speed in jibes. Any jibe with a minimum speed of at least 8 knots is one that cleanly planed through. I also used a second cutoff of 6 knots, which are jibes that often appear to be planed through when watched from afar. During the "mediocre jibe" session in March, I had cleanly planed out of just one jibe, and only two jibes were above 6 knots. In the second session today, 9 of 29 jibes had a minimum speed of 8 knots, and 16 had a speed of at least 6 knots. The results for the first session were a tad worse, but still substantially better than for the March session.

Trying to figure out what's going wrong with my jibes sure has been fun. I think I have a bit deeper understanding of jibes now. Maybe I can now keep my plane-through rate up without having to do ABk camps every 3 months! But I have also come away with a deeper appreciation of the skills of the ABK teachers, and in particular Andy Brandt's teaching skills. It took me several hours to identify the many mistakes and deviations I made in the jibe in the video above, and to sort out what's important. In my experience from more than a dozen camps, Andy always sees the one most important thing right away, and the gives clear instructions for one thing to change that will let you make progress. If you have taken ABK camps before, you know what I am talking about; if not, sign up for an ABK camp! Maybe I'll see you in Hatteras in a few weeks. Apparently, there are still rooms available in a rental house very close to the camp site.

Let me end with the GPS tracks from yesterday's second session. These tracks are from the Flysight GPS. The superior accuracy and measuring rate of the Flysight compare to the GT-31 is really great for jibe analysis.

6 comments:

  1. Ahhhhh now you're getting somewhere. Oversheeting and dropping the mast into the jibe relieves ALL the pressure from your sail so you can easily rotate it. If you keep the power on you will lean back to compensate for the pull in the sail and that kills speed. It's ALL about the entry !!!!!

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  2. Looks like you replaced your GT-31 with the Flysight? How is it? I'm waiting out till another GPS unit gets approved for GP3S...luckily my GT-31 hasn't locked up on me yet!

    -Kevin

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    1. Kevin, I am still using the GT-31 for every session. But I sometimes also wear the Flysight since it gives me much better data for jibe analysis. The position data from the GT-31 are useless in jibes, so you cannot tell where exactly the minimum speed was. I would not have been able to come to the same insights with the GT-31 data.

      We are still working with the Flysight developer on making a new GPS for windsurfing. Some things progressed really fast, but designing and manufacturing a water-proof case is a non-trivial and expensive issue that is delaying things a bit. But hopefully, there will be a better GT-31 replacement before you GT-31 dies.

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    2. Excellent! I'm sure the GP3S community appreciates your initiative! I would really like to have a device that would give good data points for gybe analysis!

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  3. You are a much better windsurfer than me but I've been watching instructional videos over and over. Just before your foot change and sail flip it appears you are looking at the rig instead of looking in the direction you want to go. I can't see if the old front hand is sliding all the way to the boom head before the flip. Have you ever tried exiting with the new front hand going straight to an underhand grip? This seems to keep the speed going on the exit.

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