Owen Clarke setup and analyse training and race data to help crews improve boat speed, change gears, whether it be the adjustment of fore-aft trim, hiking, ballast, boards or sail-plan at the optimum time and so get the best out of your boat on the race course. We provide a unique service of racing yacht performance data logging, combined with on-site/onboard analysis and prediction by one of the world’s leading naval architects who also happens to be an experienced offshore racing yachtsman. We configure the data logging in your navigation software (Expedition, Adrena, Maxsea, Deckman) and an onboard event manager to record sail trim settings and monitor condition changes. Feedback is provided verbally during onboard team meetings and as hard copy in daily and regatta reports.
Most owners at some time have bought sails that just don’t seem to fit well in the wardrobe as well as expected, some are downright wrong for the boat. The green and yellow points (Figure 1) overlaid on the yachts current cross-overs come from an actual sail testing session looking at upwind vmg which clearly shows that the J1 produces higher average boat speed numbers in 9.5 kts TWS than the J2. That is, that the J1 cross-over to the J2 is higher than originally thought and that that in higher wind speeds under the J2 the upwind target TWA is less than previously thought. The software also records speed data points during a session and these are overlaid on the yacht’s current polars which are adjusted in Polar Manager producing new target speeds for use by trimmers/drivers and nav/tactician.
It’s critical that we turn up on a boat where the instruments, speed and wind are already well calibrated. One of the daily reports we produce is for calibration which can help to make fine adjustments during the test period. However, it’s less than ideal to spend time and the client’s money to begin that from scratch. No data collection is worth anything while the instruments remain un-calibrated. If the boat speed and/or the wind angles are not correct then the calculation of true wind angle, true wind speed cannot be correct. In which case, helmsmen and trimmers will be looking in the wrong columns when looking for target boats speeds. Sail changes and VMG will also be wrong. Experience tells us that calibration is in itself an ongoing process, but basic calibration is a first priority.
If we’re not racing when data logging, then pre-planning to make cost effective use of on-water time is key. We require close to steady state conditions as possible and days of low or no wind shear keep the variables down to a minimum. The boat also has to be in race configuration and displacement. If she’s a fully crewed boat then the right weight is needed on the rail when applicable. One of the functions within the software allows us to filter out unwanted data and inshore we acquire in thirty second phases and longer phases offshore, discarding bad data automatically. However, time coded manual notes are important for full comprehension. These notes on sail trim conditions etc. can be supplemented by pictures, which refer to a point in time and are logged in using the Event Manager.
The majority of the data analysis we’ve completed has been in training days before and racing during regattas since that’s when the boat is in racing mode, at racing displacement, with the crew onboard concentrating on optimum performance. The Race Replay software is used then to play back to the sailors and analyse the various aspects of the boat and crew’s performance during the day. It’s not just about collecting data to update the speed polars or sail crossovers. One can zoom into an area of performance improvement one wants to look at and analyse the actions in say the start sequence, or entry and exit from marks, sailing angles and speeds out of tacks. The graphic show points in the race noted in the onboard Event Manager. The lines in pink indicate times when useful data was collected.
There is for many teams far too much data and this is where we believe that with our take/overview as both designers and sailors we can add considerable value to the project to provide a cost effective, practical evaluation, working with the boat’s speed team to sort the wood from the trees. The ability to post process race/testing information and filter out unnecessary numbers easily is one of the most important aspects of the software along with data collection speeds of 1 Hz. The table shows the kind of inputs that are recorded automatically by the software, in this case in thirty second phases. Processing this and tying it into the time coded information recorded manually in the event manager usually starts on the way back in to the marina from the finish or the test area.
As a rule, it takes one hour of post processing/reviewing and reporting for every hour of data collected, plus additional time at the end of a regatta or testing period for a comprehensive report. Some points can be talked through at the end day crew meeting, with a summary report always ready for discussion on the boat the next day. The blue table shows the highest/target boat speeds attained at various wind angles/wind speeds during a race. The darker the blue, the more phases the data was extracted from and so the more reliable it is. The red table shows the same for heel angle. Along with any calibration, incremental changes are made daily to the polars but it takes a whole regatta or race series to have sufficient points over a spread of wind speeds for a complete and accurate polar diagram.
Reporting is also provided in graphical format for the team, such as the sail crossover charts shown at the beginning of this page and these forestay tension and rudder loading curves that were used with the trimmers to discuss headstay and mainsheet trim and the effects on boat speed and balance/helm respectively. OC charges at our daily sailing rate when on the water, then an additional charge at the same hourly rate for work in the evenings post processing. We do it this way since every team’s requirements and time spent post processing are different. For the post sailing report which draws on our experience as naval architects/designers we charge our standard daily design/project fees. To date, everyone we’ve worked with has found the input cost effective and well worth the expenditure.
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