Hi, Just for the fun of it, I entered the text of your email into ChatGPT4.
You: I have a set of polars for my C&C 34+ (below), but I am unsure of how to interpret the downwind data. There is no information I have found on how the angles were determined. I am interested in best angles for downwind work without a spinnaker going wing on wing with a whisker pole. I am guessing the data is with a spinnaker and I am not sure if that matters. The issue is whether to go wing on wing direct to a mark and go a shorter distance vs. wing on wing or not on a lesser angle according to the polar chart. I have tried to measure this on my boat and have not found a big enough difference to convince myself I should tack downwind. ChatGPT: Interpreting the downwind data from the polar diagrams of your C&C 34+ requires understanding a few key points about these diagrams and how they relate to sailing without a spinnaker. Polar diagrams are typically generated with a spinnaker, especially for downwind angles, so the speeds shown might be higher than what you can achieve wing on wing with just a mainsail and a jib. Here’s how you can approach the interpretation and application of this data for wing on wing sailing without a spinnaker: Understand the Polar Diagram: The polar diagram shows boat speed at various wind speeds and angles. If the data is indeed with a spinnaker, the speeds at downwind angles will likely be optimistic for wing on wing sailing. Determine Best Angle for Wing on Wing: Without a spinnaker, your best downwind VMG (Velocity Made Good) might be at a different angle than what's optimal with a spinnaker. Wing on wing is most efficient when the wind is directly behind, but if the polar diagram suggests a slightly off-wind angle is faster, it may be due to the spinnaker's influence. Experiment and Record: Since you’ve mentioned not finding a significant difference in speeds when testing different angles, it’s essential to conduct more trials under various wind conditions and record your boat’s performance. Accurate and consistent data can help you understand your boat's behavior better. Consider the Course and Conditions: The choice between going straight downwind (wing on wing) or jibing downwind at angles suggested by the polar diagram also depends on the course and sea conditions. If the direct downwind route is shorter and the speed loss is minimal, it might be the better choice. However, if off-wind angles significantly increase speed, the extra distance might be worth it. Adjust for Non-Spinnaker Performance: Since the polar diagrams are likely based on spinnaker performance, you might need to adjust the expected boat speeds downwind. You can do this by reducing the speed values slightly or by using performance data from similar boats sailed without spinnakers. Software and Tools: Consider using sailing software that can adjust polar diagrams for different sail configurations. Some programs allow you to input your data and conditions to simulate the best course and sail setup. Ultimately, the decision to go directly downwind or jibe at angles according to the polar chart should be based on a combination of empirical data from your own experiences, the specifics of the course and conditions, and adjusted expectations from the polar diagrams. Continuous recording and analysis of your sailing data will help refine your strategy over time. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ > On Apr 5, 2024, at 3:18 PM, Bill Coleman via CnC-List <cnc-list@cnc-list.com> > wrote: > > > > On Fri, Apr 5, 2024 at 2:44 PM Bill Coleman <colt...@gmail.com > <mailto:colt...@gmail.com>> wrote: >> I anguish over this nearly every race, and one thing I can tell you is that >> whichever choice you decide, you will wish you did the other! >> >> Bill Coleman >> Erie, PA >> >> >> >> On Fri, Apr 5, 2024 at 1:48 PM David Knecht via CnC-List >> <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote: >>> I have a set of polars for my C&C 34+ (below), but I am unsure of how to >>> interpret the downwind data. There is no information I have found on how >>> the angles were determined. I am interested in best angles for downwind >>> work without a spinnaker going wing on wing with a whisker pole. I am >>> guessing the data is with a spinnaker and I am not sure if that matters. >>> The issue is whether to go wing on wing direct to a mark and go a shorter >>> distance vs. wing on wing or not on a lesser angle according to the polar >>> chart. I have tried to measure this on my boat and have not found a big >>> enough difference to convince myself I should tack downwind. Dave >>> >>> >>> S/V Aries >>> 1990 C&C 34+ >>> New London, CT >>> > Please show your appreciation for this list and the Photo Album site and help > me pay the associated bills. Make a contribution at: > https://www.paypal.me/stumurray > Thanks for your help. > Stu
Please show your appreciation for this list and the Photo Album site and help me pay the associated bills. Make a contribution at: https://www.paypal.me/stumurray Thanks for your help. Stu
