View Full Version : Tidetech Test Drive: The Great Pumpkin Pursuit Race

11-01-2011, 04:53 PM
TideTech Test Drive : The 2011 Great Pumpkin Pursuit Race

Our friends at Tidetech.org provided registered Pressure Drop Readers permission for distribution of their exclusive detailed tidal charts for SF Bay for last Sundays Great Pumpkin Regatta Pursuit Race. In exchange the users promised to provide the input on how the program worked for them, in an unvarnished manner.

The SF Bay Region charts are broken into 7 detailed areas:

SF Berkeley/Southampton
SF Central Bay
SF City Front
SF Entrance
SF North Bay
SF San Pablo Bay
SF South Bay

For our purposes, we utilized the Southhampton and Central Bay models. The beauty of this system is it gives you a 3 day window to view from and provides extremely detailed 1/2hour by 1/2hour sequence.

No more fumbling through the tiny tidebooks and trying to remember the time additions or subtractions. Even the larger charts produced by NOAA are no match for the detail info provided within the files from Tidetech. You can look at them one by one or run a pdf file generator that will allow you click through them on your computer or mobile device. For simplicity we sent out jpeg files of each section mention above with hour by hour computations, starting at 1:00PM and ending with 4:00PM.

Our main concern was the current in Raccoon Strait and weather we could get enuf current relief to sneak through. Testing the day prior we stopped at several points along the Straits, around Knox, along the south side of Angel Island, down to Blunt and along the back side. Comparing notes to reality, we were very impressed with the accuracy. Before we actually started on Sunday we had a predetermined plan, with few” what ifs” in store. As it turns out, by the time our start on the Contour 34 Hapa Girl rolled through, our destiny was cast in semi hard cement and it was off to the races. And even after we rounded Knox in a clockwise fashion, we knew to stay centered and avoid the edges, that info alone bought us bundles of time allowed us to reel in boat after boat. But enough about us, here are a few testimonials from those who jumped in and got a little help from their friends….

(PS Tidetech is a proud technical supplier of the 2011-2012 Volvo Ocean Race and will be providing Pressure Drop Readers a chance to score some of their unique product during the event via the Pressure Drop VOR Pick and Win contest)









From the Corsair F-27F "Three Sigma":

Prior to the 2011 running of the RYC Great Pumpkin Pursuit Race, the good folks at Pressure-drop.us offered up a set of Tide Tech's data sheets. The data that we received showed the current vector maps of the racing area for each hour, from 13:00 to 16:00. After calculating our start time (12:45), and monitoring the local forecast, the vector maps were invaluable in helping develop our strategy
for the race.

As is typical in pursuit races, the advantage of having a later start time is the ability to use the earlier starters to monitor how the race course is developing, before having to commit to a strategy. As our start time approached, it was evident that the morning Northerly breeze was fading, as the Westerly was just beginning to work it's way down the middle of the Bay. As a result, we went with Plan-B, which was to go to Alcatraz first.

The wind was very light at the start, and based on the information from Tide-Tech charts, our Plan-B called for staying as far west as we dared, to try and use the current relief offered by Point Blunt, while not getting so close and running out of wind. his plan seemed to be working, as we were making big gains on the the boats that were further east. When we finally reached the Westerly, our course gave us a perfect line to Alcatraz that would take us close enough to take advantage of the current relief on the East side, while not getting so close as to run out of breeze.

Rounding Alcatraz was Crazy, as boats were converging from every direction, and the wind was freshening. We tacked onto port, and were in good shape, on a perfect line to just clear The Rock until..........the ID-48 Bodacious + crossed us, and tacked directly on our our wind. We knew we were in trouble when the oxygen deployed from the overhead compartments, as we struggled to find enough air to avoid hitting the mark (Alcatraz). When we realized that we weren't going to make it, we had to flop over onto starboard, directly in front of about a million approaching port tack boats. Once we found clear lane, it was back onto port, ease the sails and blast across to Raccoon Strait.

As we approached Raccoon, we went to the chute as soon as the wind backed enough, and we had a clear lane in. I sent the crew down below to have another look at the Tide-Tech chats to confirm our Plan-B strategy for the Strait, only to realize that.......I had left them in the truck.

Now, here is when things began to go wrong for us. You see, at this point we were leading the "Trimaran" division, having passed the boats that started ahead of us, and pulled away from the ones behind. All was good, as we worked our way down Raccoon. As most of the boats were on the North side, we worked the South, as there was a better lane, with fewer boats to windward. However, as we passed Ayala Cove, it appeared that the current had started to ebb in the Strait. That's funny, because according to what I remembered from the Tide Tech charts, it was still too early for the ebb. So, onward we sailed, blissfully unaware.....

After exiting Raccoon, and heading across towards the finish, the pressure was getting lighter, as we found ourselves caught in a series of little battles, trading jibes with the much bigger boats like Bodacious +. We were still doing great, however as we approached the finish, and remembering what I had seen off Ayala Cove, I made the fatal mistake of going to the left, figuring the ebb would "set us free". Needless to say, that last jibe onto starboard was torture, as we helplessly sailed against the still-flooding current, making about 1-2 knots over the ground. All the while, we watch as boat after boat approaching from the right crossed the line. By my estimate, we lost over 30 positions, including the other trimarans in The "Rum Division", within the last 300 yards. Arrrrrrrrrrgh!!!

After returning to the truck, one look at the Tide Tech vector charts showed exactly what went wrong. The chart showed that the early ebb that we experienced off Ayala, was actually a back eddy off the point. So, had I not left the vector charts in the truck, we could have avoided the fatal mistake that cost us not only the bragging rights as first-trimaran-to-finish, but also the bottle of grog for the winner of the Pressure-drop.us multihull Rum division.

My take away from all this is that the information available from Tide-Tech is an invaluable tool for racers on San Francisco Bay. It made a believer out of me.


-Christopher Harvey
Corsair F-27 Class President
F-27 "Three Sigma"

We were studying the Tidetech maps before the race on our Beneteau 10R Split Water. The obvious big flood in Raccoon Strait early in the race made it a gamble to go there first. But the flood going over from the start line to the Strait appeared to be a help in fetching the Strait entrance. We did a few runs before our start and the wind angle was good, and we felt we could even crack off enoughto put up our Code 0, which has been an effective sail for us.

So we gambled in going the counterclockwise route (seemed to be about 50/50 of the boats starting before us). As Tidetech predicted, we were able to use the strong left-to-right set to almost make it into Raccoon with the Code 0 up (we were sailing quite a bit to leeward of most of the CCW fleet). But in the end, as everyone found who went that way, the wind was too light insight the strait to make decent progress. We were among the many boats trying to work the flood relief along the Angel Island side, which added some hairy moments with a lot of boats with little to no steerage in a close space with various eddies etc. Out the other side we all found wind and we had decent boat speed from there on out. We should have probably been more conservative though, based on the tide charts,
and gone the other way, but we sure weren't the only ones!

Dave Britt
Split Water

Looking at the TideTech data the nite before the race it was clear that, unless there were strong winds, going to Racoon Strait first wasn't an option. The forecast called for light northerly winds, that would switch to westerly some time after our start. The TideTech chart showed some relieve from a strong flood east of YRA 8. So the plan was to hoist the spinnaker at the start and ride the northerly breeze toward YRA 8. Past the mark, once into the cone of alcatraz, we would have tacked back and forth until crossing to the other side of the island. We would have used the remaining flood down Racoon strait, all the way to the finish.

The wind at the start was light, so we executed the plan. The northerly wind didn't last much, and we soon switched to the jib. Once on the slot there was a fresh breeze that was fetching us toward the island. My mistake was that with the fresh breeze, I stop focusing on the currents, and I didn't execute the plan of playing the cone, but rather tried to fetch the island on a single tack. With the strong flood it didn't work, and we lost quite a few positions to boats that played the cone more wisely. The flood was strong and pushed us back to the island forcing us to an extra tack. By then I had definitely realized the force of the flood, and I tacked as close as possible to the island gaining on a few boats that had just passed us but tacked early. After tacking toward tiburon, I kept a wide berth from little alcatraz, aware of the strong flood still on. From then on the current game was over, and the dying flood did help us all the way to the finish line.

What surprised me most is how detailed the TideTech data is, and how much easier it becomes to plan a strategy with such a clear visual help.

Fabio Maino - FT10 "Centomiglia"

Whelp, I would not want our less than stellar showing to detract from what a good product I think the TideTech models are. Because I definitely see their very precise predictions reflect the actual behavior of the currents very well, without a doubt. Unfortunately, our read of the wind, among other factors, lead to a fairly late finish for us. :^(

The relatively light wind predictions and the models showing the flood abating sooner in Raccoon Straits, lead us to take a counter-clockwise route (along with most of our similarly rated competitors). We however started late, and low (South) of the majority of them. This worked out not so bad at first for we were able to utilize the good current relief on the Angel Island side of the approach and in the straights. Out of contact with the fleet, we had fairly undisturbed breeze, light as it was. Even though there was a Northerly fill, the fleet above and us had a hard time over coming the current. We had less wind, but much more favorable water.

Entering the straights close to Angel Island, there was some very mild shore breeze in tight on the shore of the island, plus the slight counter current pulled us up to the same rung as the boats that had been leading us (but further to the North). The majority seemed to be battling the brunt of the current in the middle of the straits. Things were looking up for us at this point. Unfortunately we dug too deeply into Alyala Cove, lost attachment of what little breeze we had. Ended up having to back track out of there. At this point we could see a Westerly fill had come through the gate, and we had lost what gains we had achieved playing the counter current.

Exiting the straights we met the a large pack of the later starters that had gone clockwise. It was obvious that there had been a solid Westerly fill that had allowed them to over come the greater current. We fought our way across the turbulent tide confluence there, and turbulent wind of the converging fleets. But, we suffered some less the stellar boat speed, allowing the boats we were chasing to further separate. Fun blast across to Alcatraz and popped the chute. We stayed further West of and in more favorable current than our leaders.

Coming back around A.I. this seemed to be working out for us, staying in the channel and residual flood. Or, at least it seemed there was again the chance we could come in contact with some of the boat we had been chasing. But, again we played it too close to the wind shadow and was becalmed. Fortunately, the residual flood was sufficient to continue carrying us in the right direction. And, we were able to get in the Westerly coming through R.S. again. And, finish before I had had the chance to drink all our beer. :^S