GPS jibe analysis

When working on improving your jibes, a GPS can be a useful tool. Looking at the GPS tracks in GPS Action Replay, simply click on "Jibe analysis", and you get a nice table that summarizes your jibes:

I have sorted the jibes by "minimum speed" to quickly see my best jibe of the day. In this example, I kept a speed of 14.3 knots or more through the entire jibe - 70% of the entry speed (the "score"). The next-best jibe was pretty close, and even the average for the best 10 jibes is not so far behind. Great! Indeed, my jibes that day had felt good - for once, I had planed out of the most of my jibes.

However, the results looked a lot worse when I changed one analysis parameter by selecting the "Doppler" checkbox, and re-computing the results. Here is a direct comparison:

Suddenly, my jibes did not look nearly as good anymore - according to the Doppler analysis, I lost more than half of my entry speed in even my best jibes; for some jibes, like the first jibe that's highlighted in blue, the minimum speed dropped to less than half! What is going on?

Let me start by quickly reviewing the difference between "positional" and "doppler" analysis (not all my readers are GPS speedsurfers - if you are, perhaps just skip to the next paragraph). All GPS units, regardless if you use them for directions in your car or for measuring your speed while windsurfing, determine your position from the measured distance to several GPS satellites (typically 6-8). The accuracy of the position is limited by a number of factors to about 3 meters. My GPS, the Navi GT-31, measures the position once a second; the difference in two positions gives you the speed. When windsurfing at 20 knots, you move about 10 meters in one second. An error of 3 meters would then give you a 30% error in the speed, a rather large error! But fortunately, there is another way top measure the speed using the "Doppler Effect". Doppler-based measurements tend to be much more accurate, with reported speed accuracies of 0.1 knots. This is why GPS-based speed events generally require the use of a GPS that logs Doppler speed, like the GT-31 that I used.

So, if Doppler speeds are much more accurate, does this also mean that the Doppler-based jibe analysis is more accurate? Not so fast! Let's look at the GoPro video of the jibe #1, where the position-based speed was 13.8 knots, but the Doppler-analysis thinks it's just 6.2 knots:

 The jibe was nicely planed through, which typically requires a minimum speed of more than 10 knots. For comparison, here is a section from the same session where I was moving at about 7 knots (and positional and doppler speeds were very close):
Nina was also wearing a GPS, so I could use her tracks together with mine to accurately define this 8-second period where I was sailing at 7 knots (I was slightly slower at the very beginning and end of the movie).

Obviously, the board speed during the jibe was significantly higher than 7 knots, so the Doppler-based jibe analysis does not seem to be accurate. Let's take a close look at the track and speeds for another jibe (#12 in the table above):

In the middle of the jibe, the direction of the board changes by about 30-40 degrees per second for about 4 seconds. The speed tracks show something interesting, though: the Doppler appears to lag behind the positional speed by about 3 seconds! According to the Doppler data, the minimum speed is after the board started going pretty straight again; the upper (positional) speed graph shows rapid acceleration at this point. Looking at the GoPro video, the positional speed seems correct, since I hung down and pumped to regain my speed right after the jibe. Here is the video:

This jibe (#12) was a bit wider than jibe #1, and the discrepancy between positional and Doppler-based minimum speed was smaller. This was a recurring theme in all the jibes I looked at: the tighter the jibe, the more the minimum speed would drop in the Doppler analysis. I was working on laydown jibes, so I was cranking them relatively tight; Nina's jibes that day were wider, and the speed differences between Doppler and non-Doppler analysis were much smaller.

To some extend, the 1 Hz sampling rate will cause an underestimate of the speed when the board changes direction rapidly. Even in the positional analysis, we measure the distance along a straight line, but the board had sailed a longer arc. In the Doppler analysis, a similar error would occur; however, it should also be of similar magnitude, and not substantially larger. But we need to keep in mind that even the binary data files do not contain "raw" data, but rather the result of a complex mathematical analysis. From the time difference in the speed curves, it appears that the Doppler data include a filter with something like a 3-4 second time constant. In 4 seconds, the board changes direction by perhaps 120 degrees in the jibes - that's very far away from a straight line! I think this could explain why the Doppler speeds in the jibes appear to be too low, and that things get worse the tighter the turns are.

This entire thing is not just a theoretical thing. If I want to know how good my jibe was, it makes a big difference if I kept 70% or just 44% of my speed. Keep in mind that the Doppler-based analysis keeps estimating lower speeds for several seconds in a row, without ever "compensating" for it with higher speeds. If you'd draw two tracks, one based on positional and one based on Doppler data, the "Doppler surfer" would fall behind in every jibe!

This has a significant effect on alpha 500 results. For the top jibes in the tables above, the lower mid-jibe Doppler speeds added about 2 seconds to the time to reach 500 meters, dropping the alpha speed by 1-2 knots! Since alpha team rankings are usually quite tight, even just one knot would make a significant difference. However, I do not think that going to non-Doppler alphas is the solution, since the non-Doppler data errors add up over the 45-50 seconds that a 20-knot alpha 500 run requires.

For now, the solution for alpha rankings is to go with wider jibes with a very even carve. In the future, we can only hope that better GPS units with a higher sampling frequency become available. Several 10 Hz GPS trackers are commercially available already, but it is not clear if any of them provide the Doppler data required for highly accurate speed measurements - and if such Doppler data do not suffer the same shortcomings shown here for the GT-31.
----
Added July 25, 2014: 
I recently learned why the position-based speed and the doppler speeds were so different, especially during jibes: I had my GT-31 set to "low power" mode. In low power mode, the GT-31 tracks fewer satellites (at most 6), which leads to much lower accuracy. Simply setting the power mode back to "normal" resulted in a much better agreement between doppler and regular speed data. The tracks also seem much more accurate in "normal" power mode, where the GT-31 typically tracks 8-10 satellites. 

Falcon Fun

East winds today brought a nice setup for some speed sailing in the properly name East Bay, 10 minutes from our house. This time, my lovely wife decided to join me to sail her Falcon 89. She had bought the board just a couple of months ago from Dani. But while she loved this and other Falcons when she sailed them the past two years, the first couple of sessions on her own Falcon had been frustrating. So we played it conservatively today, and rigged her 5.7 m wave sail that is similar to the sails she usually uses for freestyle.

The wind was in the low 20s, gusting into mid-20s, and the water in East Bay was nice and flat. Nina ended up having a blast - here are a couple of pictures:

Flying the Falcon

Despite the moderate wind, she clocked her second-fastest session ever. After sailing freestyle boards almost exclusively for many months, jibing the slalom board needed some adjustments, and she was not happy with her jibes. Nevertheless, she set a new personal best for alpha 500 - nice!

I mostly just enjoyed the sailing on my XFire 90 / Matrix 7.0 combo. I have been working on different aspects of the jibe in recent sessions, and was starting to get a bit frustrated with the lack of visible improvements. But the flat and shallow water in East Bay creates the perfect jibing playground, and I finally got the impression that all that work is starting to pay off. Here's a mid-jibe GoPro picture:

I think it helped to have Nina on the water - I really wanted to push the sail down and out of the way to see what she was doing. So my arms are like they should be, with the front arm extended and the back arm bent to oversheet. The mast is pointed about 45 degrees towards the water, keeping nice pressure on the carving rail. My posture is better than in most jibes, with a straight back, chin up, and looking into the turn; but my knees should be bent a lot more. The GoPro showed that I still tend to fall back into other bad habits, too, like not sliding the hand to the mast - but there's definite progress. The non-doppler jibe analysis gave my top jibe a score of 70%, with a minimum speed of 14.5 knots, and 12.9 knots min speed average for the top 10 jibes. The XFire 90 does do tight turns quite well, so most of my turns were reasonably tight, which means the results using doppler analysis are a lot worse; but that's a topic for another post in the future.

Company on the water

I'm a bit tired after 3 days of windsurfing in a row. Maybe it's Friday's fault - with Dean having plenty of wind in Hatteras, I tried to do my part in improving our Fogland Speed Surfer team ranking on the GPS Team Challenge and sailed 100 km. We went to Kalmus, where low tide, south winds, and warm temperatures attracted a crowd - Nina, Ron, Marty, Dani, Drew, and Bruce were all to out there. Nice to have plenty of company on the water again! It was, however, rather foggy:

I sailed a new fin for the first time: a 35 cm Type S from Black Project fins. As a speed fin, it's not supposed to go upwind really well, but I still was a bit disappointed. I ended up practicing a lot of tacks just to stay upwind; but perhaps the fog was also to blame, since picking landmarks for orientation was not possible most of the time. Besides seeing lots of friends on the water, the great thing about Friday was that I finally was able to sail without a hood and gloves.

The forecast for the weekend had not been great, with only 14 mph SW wind for Saturday. However, the fog was gone, and we saw a little bit of sun from time to time. The air was a bit colder, but still warmer than the water, so we got a nice little sea breeze enhancement in the afternoon that kicked the winds up above 20 knots. A lot of the same sailors came back to Kalmus, now also joined by Steve. Nina did not sail; instead, she rode her bicycle down to the beach, and took a few pictures:

Martin doing a one-handed downwind 360

Dani going slow. Most of the time, only his fin was in the water.

Sailing the good old Hawk again

Steve

Another 360 by Martin

Besides being a bit colder, another big difference was the chop. With SW-WSW winds, there was a lot more of it than the day before, when the straight south wind has created nice and orderly little rollers. I tried to escape the chop by cruising up to the Kennedy Slicks, but timed it so that I arrived during and extended lull, where even my 7.0 and Dani's excellent 38 cm Vector Volt fin did not alway get me planing. When the wind picked up a bit later, I took out my Hawk to try a new 30 cm MUF Slalom Weed fin. This was quite an amazing fin - it provided plenty of lift, something I rarely get from weed fins, and was almost impossible to spin out. But it was also the first power box fin I ever used that did not fit the box without sanding. It's quite normal that tuttle box fins need some sanding to fit, but all of the perhaps 10-15 other power box fins I have fit without sanding. I went out without bothering to fit the fin, only to discover that it actually was able to move a bit from side to side. Even more amazing that it worked so well, then!

For today, the forecast predicted some N-NW winds in the upper teens for the morning. Since Dani was still in town, and the tides were timed perfectly, I convinced him to try a new spot: Barnstable Harbor. We had a lovely 100 minute session there, starting just as the tide dropped low enough for the marsh islands to come out, and stopping when the wind dropped too low. Dani sailed without gloves and needed to take a bunch of breaks to warm up his fingers, since air temps were only around 42ºF (6ºC). Nevertheless, we had tons of fun, and Dani absolutely loved the spot. Sailing full speed on water where the "waves" are about one inch high is just a wonderful thing. We were a bit underpowered most of the time, but still managed top speeds around 25-27 knots. The nearest wind meter in Chapin showed averages around 12 knots, and gusts up to 18 knots, but we probably did get a few knots more where we sailed.

With three sessions in the last 3 days, I have now windsurfed 11 of 21 days in April. The forecast for the next 2 days also looks promising, and Nina is eager to sail her Falcon tomorrow. With sun predicted for tomorrow, but rain on Tuesday, we might actually not go sailing on Tuesday...

Bonaire SUP Sailing

I finally got around to putting together a short video clip from SUP sailing at the Lac Bay reef in Bonaire - here it is:


Go to Vimeo to view the movie in HD.

I did a couple of SUP trips out to the reef during our two weeks in Bonaire. The first was with Andy Brandt and several other campers during the ABK camp; the second on, from which the video is, was a few days later with Nina. It was great, if not essential, to have Andy show us the way during the first trip, since the reef has a number of very shallow areas that just love to eat fins. On the days I went, winds were marginal (15 mph), perfect for SUP sailing. The waves are slow and very beginner-friendly; most of us fell once or a few times, but no damage was done. Being on slow SUPs was a big advantage - we were going slow enough that we could pick our way between coral heads in the dicey areas. A German windsurfer, Rainer, came out to join us during the second trip, but he was planing on a shortboard. Even though he is a better windsurfer than I am, his speed did not give him enough time to avoid the corals. He hit on, and broke off the fin. There was not much we could do to help him, other then keep an eye on him. He tried to tie the harness around the back of the board as a fin replacement, but that did not work. Fortunately, the wind was onshore, and within a few minutes, he had drifted in past the reef, from where he slowly walked his way back.

I sailed to him to check if everything was fine, but underestimated how fast the wind made me drift sideways, and ended up falling off at a really shallow spot. Since I did not want to climb over the pretty much untouched corals there, I had to let go of the board, and swim around through deeper channels to get back to it. But perhaps that was a lucky fall, because the GoPro took some nice footage of the corals while the board was drifting (I was using the dive housing, which works great above and under water).

I used the oldest and longest SUP that Jibe City had lying around, because Andy had called it "unbreakable". It worked fine for me - I don't think that I would have done anything more dramatic on one of the newer, fancier, turnier SUPs. There's not much action going on, even after piecing together a few small rides, but I thought that the reef was just so beautiful that I had to share the video.

Fun in the rain

Air and water temperatures around 44ºF (7ºC), showers turning into steady rain, wind predicted in the low-to-mid 20s (mph) - who would not be eager to go windsurfing? Well, I could think of a few names, so I ended up on the water alone. Part of my excuse to go out was that Dean had a very nice forecast down in Hatteras, and was planning to "sail his ass off". But I also wanted to explore another new potential speed spot 10 minutes from our home: East Bay in Osterville. Here are today's GPS tracks:

The forecast had predicted that the wind would pick up in the morning, with occasional rain showers before noon, followed by steady and heavy rain. So I left as soon as the local wind meters showed some promise, and was at the beach before 9 am. The initial gear choice was my XFire 90 slalom board with the KA Koncept 5.8 m sail. Since the tide was low, I used a 23.5 cm weed fin from Black Project Fins (the one they call the "28").

Since I had never sailed this spot before and the water looked shallow, the first few runs were slow and cautious. I got off a number of times to check the water depth, which was just deep enough. Sailing slow on slalom gear that's meant to go fast is a bit of work, so after a few runs, I gave my arms a rest and went back to the van to get the GoPro. Back on the water, I started going a bit faster, although I still got off several times, and even walk the shore line for a while at what looked like the spot for speed runs. Meanwhile, the wind was picking up steadily, and I fiddled around a bit with the sail trim to adopt.

Being overpowered while exploring a new spot was more tiring than I had expected. I did a few downwind speed runs on the left side, and suddenly found myself in chop that made board control a bit challenging. It also took a while to learn the wind patterns - what I had originally taken for gustiness turned out to be strongly linked to upwind and downwind obstacles. When I analyzed the GPS tracks at home, I discovered that I had gotten my top speeds not at the spots where I went for speed runs, but rather in the middle, where the wind came unobstructed through the inlet, and thus was stronger than at the sides where the water surface was a lot smoother. Here's a GoPro picture from one of the speed runs:

The picture shows that my stance is not quite perfect; I never really got the feeling that I was 100% dialed in. However, I did see some pretty decent top speed numbers on the GPS display, and ended up with my 4th-best ever 2 second speed (30.5 knots, 56.5 km/h). Quite happy with that, I decided to switch to something more comfortable to get a decent 1-hour average for our Fogland Speedsurfer team.

Out came the Tabou 3S 96 and the Gaastra Manic 4.5. Since the water in the bay was quite flat, I decided to give the Maui Ultra Fins 19 cm Delta Freeride fin another try. I had loved the fin the first time I used it on flat water, but had serious spin-out problems when I later used it in chop. Today, the fin worked quite well. I had one spinout when entering a jibe at high speed with too much back foot pressure and too little rail engagement, but a small technique adjustment made sure that did not happen again. After a few rig adjustments during the first runs, I was off to jibe practice! The short run length in the bay (about 650 m) meant about one jibe every minute, but I had wanted to work on jibes, anyway. The water surface at both ends of the runs was nice and flat, just about perfect for full-speed jibes. I ended up with quite a few planed-through jibes that I was happy with. They helped to forget the pelting rain that had now started. I sometimes had rather reduced vision, with the windward eye closed, but fortunately, I had the entire bay to myself.

Back at home, I discovered that I had set a new personal best for alpha 500 (that is a 500-m run with a jibe in the middle, and the ends of the run must be within 50 meters of each other).  The top three alpha results were all on the XFire 90, even though my best 15 or so jibes were all on the 3S. My best minimum speed in a jibe on the XFire was 6.5 knots, which is marginally planed-through; on the 3S, it was 9.5, a lot better (these speeds are doppler speeds, which tends to under-estimate the actual speed, especially for tight turns). Part of the difference was probably due to the sail - the 4.5 wave sail was a lot easier to handle in turns than the 5.8 m cambered speed sail. But part of the difference probably was also due to getting a bit better at jibing again, and to figuring out where exactly the best spots to turn were.

After 90 minutes on the 3S, I had to call it a day because my leg muscles were starting to cramp up. I really need more practice sailing overpowered on slalom gear! But is was a great session on a new spot.  Next time the wind direction is right for East Bay, Nina promised to join me. She likes the fact that large parts of the bay are shallow enough to stand, and can't wait to practice freestyle there.

--

A few hours after I wrote this post, Dean posted his speeds for the day. His day had started badly - he was out at the reef when the wind died, leaving him with a 2.7 mile schlog and a 2 mile "walk of shame". But he went out again when the wind picked up a bit later, sailed a total of 115 km, and easily beat all my speeds by at least 3 knots. No surprise there, he usually does that, and I actually liked it - this briefly gave our Fogland Speed Surfers team a top-10 spot in the monthly rankings. That only lasted a few hours, until other teams posted more sessions, but we're still much closer to the top than to the bottom. Quite a difference to most months, where we fight not to be on the last place! In the alpha ranking, we are currently #6 of 39 teams, less than 2 knots behind the top spot. I have to say that I am proud of that, since alpha is the most technical of all the speed rankings - you cannot get a good alpha without a good jibe and good speed. More reasons to keep improving the jibes...

Pictures of Graham

I mentioned in my last post that Graham positively rocked in Kalmus last Sunday. Fortunately, his dad Jeff took a few pictures of the action. Here's one about attitude:

That looks like the sail throw for a Kono. I saw one of his tries, and while he did not quite make it, it looked darn good to me. I just love the attitude Graham displays in this picture.

There's also a very nice series from a Flaka Diablo:

It's getting warmer

It's slowly getting warmer, and more and more local windsurfers are ending their long winter sleep. Yesterday at Kalmus, I talked to at least 3 sailors who were out for the first time in 2013. It was not quite as warm as promised, with air temps around 45ºF (7ºC) and water temps perhaps a tad lower; but it was warm enough for a 3-hour session on my 6.5 m sail. The wind was up & down a bit, so I ended up using 3 different boards - first my Skate 110, then the 3S 96, a short session on my XFire 90, and back to the 3S 96.

With south winds and a low tide, the water was just beautiful, with very nicely formed waves and perfectly flat water in between. The main reason I switched from my Skate to the 3S was that I wanted to play with the (non-breaking) waves a bit more, but a slight increase in the wind made this a perfect switch. I felt almost overpowered when I decided to switch to the XFire for a few speed runs - of course, that was just before the wind dropped again a bit for 15 minutes. Still, I got almost 29 knots on the dial. I'd be pretty happy with that on most days, but yesterday, I was on my "low-end", uncambered Gaastra Pilot sail, and the wind meter showed gusts of at most 25 knots, which makes this a darn good speed for me.

One interesting thing in sailing both the 3S and the XFire for a while was that it gave me the opportunity to compare the fins. On the 3S, I used a 29 cm Tangent Dynamics (TD) Reaper; on the XFire, I used a 23.5 cm Black Project (BPF) WEEDspeed (they call it a "28", since it's similar to a 28 cm pointer). The TD is a freeride fin, the BPF a speed fin with a longer base, and therefore an area that seems almost as large as the TD area. The BPF is noticeable thinner, with sharper front and rear edges. Both are weed fins, but they behave quite differently.

I like the TDs because they can take a lot of pressure right from the start - you can really push the fin to get going. I sailed the 3S with the TD fin a lot longer than the BPF fin, and ended up getting almost the same top speed (within about 1 knot); but I probably hit a stronger gust to reach this speed. With the TD, I had to be a bit careful about fin pressure at high speed - too much, and the fin would spin out.

The Black Project WEEDspeed was just about the opposite. I had to be careful at low speeds, but the faster I got, the more grip the fin provided. Once up to speed, the fin felt bomb-proof, giving a lot of confidence to go fast. I think this is pretty amazing, since this fin was quite a bit shorter than the TD; also, the XFire has outboard slalom footstraps which put more pressure on the fin than the single center strap on the 3S. I was clearly not anywhere close to the top end for the fin, which has been clocked at more than 40 knots by "real" speedsurfers.

The difference between the two fins is not really surprising. The thinner profile of the BPF WEEDspeed alone explains much of the difference - thicker profiles provide more grip at lower speed, thinner profiles will work better at higher speeds. Since I sometimes like to go fast on my non-slalom boards, I think I'll just have to get myself a few powerbox slalom or speed weed fins. Most of the slalom and speed fins are only available in tuttle versions, but at least one high-end fin company shows them as available in powerbox versions, too. I'll see what I can get and report back!

My focus in the session was primarily fun and distance, but since I had to turn around a few dozen times, anyway, I worked on jibes a bit, too. The good news is that sliding the hand to the mast has become quite natural now, after just one practice session. The bad news is that the oversheeting will need a bit more work. I did get the sail out of my line of sight a few times, but not always; and the timing of bringing it back up will need a bit more work. Looking at nice jibes in videos, this is just one fluid motion of moving the sail back and then bringing it forward again; in my better tries, its more like "Oh, cool, I remembered to push the sail back and keep my front arm extended! Cool! Now when do I bring it back up? Two seconds ago you say?" Well, ok, nobody really said "two seconds ago", but I'm sure someone would have if I had asked.

A brand new thing for Kalmus was the seal that was taking a break on the beach yesterday. Fortunately, it was still complete and alive, not half-eaten as the seal Jerry saw a few weeks back near Chatham. Maybe he just needed a break from the great whites.

Another great thing to see yesterday was young Graham in action. I admit that I stayed away from him most of the time, lest jealousy would overcome me. But I saw a nice Kono attempt that, to my unknowing eye, looked like he was almost there; and Nina reported that his Flakas have become "really nice" now. He is planning to spend the summer teaching windsurfing in Hatteras again - I can't wait to see him sail when he comes back, after sailing almost every day for a few months in a row.

A speed spot close to home

This morning was rather chilly - air temperatures near the water were around 36º F (2º C). After getting spoiled with temperatures in the 40s recently, that felt too cold. The waves at Corporation looked lovely, albeit too high for this newbie; Skaket looked easier, but had blowing sand and wind in the mid-30s. Nobody was sailing either spot this morning when I was there, and this was not my day to play alone in waves.

However, things warmed up a bit towards noon, and the wind went down a bit. Since the fastest sailor of our Fogland Speedsurfers team, Dean, is on Cape Hatteras and posting amazing speeds, I figured I just had to go out so we can get the two posting we need for a session to count. Since the wind had big lulls, I decided to stop back home first to pick up my larger slalom board. I finally made it onto the water shortly past noon. The nearest iWindsurf windmeter showed averages below 20 mph, but the water indicated a bit more - and it looked beautifully flat! 

We had checked out this area on SUPs before, and I knew that the water could get too flat to sail at many different spots. I therefore picked a smallish fin (28 cm WeedSpeed from Black Project - they call it a "34" because it has lots of area), and my trusted old 7.0 Matrix. Here are the GPS tracks:

I did step off the board a number of times during the session to check the water depth, and cut the session short after one hour because it was getting too flat in the area where I was sailing. The tide today was 10 feet (3 m), and I was sailing around mid-tide, so water levels were changing quickly. 

The spot has quite a lot of promise for speed sailing. You have to time the tides correctly - too high, and all the sandbars and islands are hidden under water; too low, and you are limited to channels or the deeper (and choppier) part of the harbor (although that would be doable). There were several regions with perfectly flat water. I did not reach any great speeds today, but I was definitely underpowered for speed runs; at times, I was barely able to plane. The fin I used was a safety choice for unknown shallow waters, and thus a bit to small for the wide board and slightly underpowered conditions. But even so, this definitely was a great session! And perhaps the best part is that going back there is easy - the launch is just a 10 minute drive away from our home :-)

Unlearning bad old habits

According to wind statistics, April is the windiest month on Cape Cod, so perhaps it is not a big surprise that I got to sail 4 days in a row. A couple of days included some SUP sailing - Monday at Dowses Beach in Osterville because I started early, and Wednesday in Skaket because I was late and arrived after the wind had dropped. My timing was also off a bit on Tuesday, where I went for speed at the Kennedy Slicks in Hyannis Port. The wind had been above 30 mph for 3 hours, but dropped just as I got onto the water. I got a couple of speed runs in, but then had to call it a day.

Yesterday was another fun day, with winds around 20 mph. I sailed in Kalmus for almost 3 hours, and Nina joined me for part of that time. Wind and waves invited some chop hop practice:

I love the way the water catches the sun in the pictures above and below:

The bottom picture shows the main thing I was working on yesterday - hand positions during the sail flip in the jibe. I can jibe decently when everything is lined up right. But there are tons of things that will make me loose speed in my jibes, or fall: too much chop; other sailors or distractions near me; getting tired after sailing for an hour or two; too much time since the last ABK camp; and many other things. I think the real problem is that I jibed for a couple of decades without decent instruction. Some windsurfers like Hardie or Tom can learn on their own and develop a nice style, but I don't belong to that group. I have been doing things wrong for too long, building bad "muscle memories" that I fall back to whenever I start to get tired, distracted, ...

Every time I look at GoPro footage, I see myself making the same mistakes over and over again. In jibes, that includes:

1. Placing the back foot so that it points to much towards the edge (instead of placing it parallel to the front strap, pointing more towards the front).
2. Pulling myself up to the sail with bent arms.
3. Not oversheeting (hard to do if both arms are bent).
4. Not moving the hand towards the mast when flipping the sail.
5. Looking down at the board or sail, instead of out of the turn.

There are other things I do wrong sometimes, but the things listed above I do wrong almost every time. Trying to remember all of them mid-jibe simply does not work for me - if I think of one, I certainly will forget the other four. So for yesterday's session, I decided to concentrate on just one thing - moving the hand on the boom towards the mast before flipping the sail. The idea is to do this so often and consistently that it becomes automatic. So when I then move on to the next thing on the list, I'm hopefully doing one at least that one thing right, without having to think about it.

In yesterday's session, I jibed about 50 times. It took about 10 jibes before I remembered what I wanted to work on, but after that, I did move my hand towards the mast in most jibes. On the water, I was quite amazed how much of a difference that made. Compared to leaving the hand near the front harness lines, as I had mostly done before, it's much easier to control the rig, and to move it towards the front during and after the flip. On the GoPro footage, I saw that I still did do the three other things wrong during most jibes, so it's no surprise that I lost a lot of speed in most of the jibes. Still, getting going again after the jibes was definitely much easier with the better hand positioning. That said, I did notice that my hand movements often were too small - I moved the hand maybe halfway towards the mast, instead of sliding it all the way towards the front end of the boom.

Some curious reader might ask why I started with the fourth step on my list of common mistakes rather than with the first one. The reason is simple: if I do everything right at the start of the jibe, so that I can oversheet nicely with a straight front arm, I'll often carry enough speed into the turn that the jibe is ok even if I do not slide the hand towards the mast. That takes away the motivation to keep improving - and therefore just re-enforces bad habits. In boom cam footage from light wind SUP sailing, I noticed that I had the same mistake of not sliding the hand; a SUP is stable enough that "little" mistakes are easy to overlook. 

For the next session, the goal will be to focus getting rid of bad habits #2 and #3 (under the assumption that #3 is mostly a consequence of #2). At the start of the jibe, my front arm is often reasonably straight, and I do let the sail pull me into an upright position. The next step would be to push the sail out of my line of sight with a (mostly) straight front arm; but instead, I often open the sail up a bit (and too early), which leads to the dreaded "bent arms, ass out" stance. The motto will be "sail, get out of my way!". I have done this on occasion, mostly after being told to do so during ABK camps. It will be interesting to see if I can get this to "stick" by concentrating on it a few dozen times in a row. Considering that a typical sailing year with 100+ sessions includes many thousands of jibes, I may need a few "single-focus" corrective sessions to unlearn each bad habit.