Sail control: key differences emerge between Cup teams

I am not familiar with sailboat design, but I find these AC boats fascinating from an engineering standpoint. From the standpoint of wing design, being able to adjust the thickness of a wing at such low speeds (compared to aviation wings) makes huge sense. The relative speed between the air and these wings is probably similar to STOL aircraft wings. While airplanes in STOL mode are ok with drag because they have lots of available HP, clearly drag in these boats needs to be minimized. Plus EVERY airfoil has a stall speed. Check out the airfoil of Mike Patey's "Scrappy" build where he built a double leading slat design to change the wing shape to provide a wider range of air speeds with one wing (lower stall speed while maintaining a high maximum speed with low drag.) It is hard to change the thickness of an aluminum wing, so in aviation they change the chord instead. If I recall years ago NASA experimented with a variable thickness/variable shape airfoil. I think there were benefits in flight envelope, but the design was just too complex and expensive to justify the benefit. Since minimizing drag is critical in these boats, and you can't significantly change the chord, changing the camber and the thickness is all that is left. The thickness may be a second order effect, but being able to change airfoil shape for different wind speeds and angles of attack, while minimizing drag, could be a huge benefit (these are airfoils that need to generate lift at just a few knots without stalling nor significant drag, but also enjoy minimum drag while at up to 50 knots or more. Few aircraft have wings that can provide lift across a ratio of minimum stall speed to maximum speed exceeding ten. These boats need to. Clearly a minimum stall speed, and minimum drag across the entire "flight" envelope are key to winning the America's cup. And in such a tightly contested event, optimizing second and even third order effects seems justified, especially when it comes to the mainsail (wing.) So changing the foil's camber and thickness seems completely logical to me. Dave Evans

your coverage just keeps getting better and better, last cycle was well researched and very insightful, and this cycle youve gone even further. just watching your interviewing skills improve over the last few years has been impressive. youve been a major force in making the cup more accessible and interesting for people like me who dont have the time or interest or knowledge to pour over recon photos. other sports have full coverage of a season to keep fans interested and invested until the championships/finals, our sport, not just the cup, doesnt besides a few people like you, thank you for all of your hard work and time and knowledge, keeping both sailors and non-sailors interested in our niche and sometimes dying sport.

Thanks Tom and Rob. Another deep dive into AC75 sail control systems. Much appreciated.

Great video Mozzy! I think you guys were hinting at this towards the end of the video, but I honestly think that sail trim and foil cant automation will be the key tech that separates the winner and loser of this cup cycle. With correctly designed automation, the potential is enormous. You can do insane things like: - Create a 'one button' tacking program that syncs foil cant, sail trim, and mast rotation perfectly through the maneuver while providing the helm with a steering angle target that they can follow. Essentially guaranteeing a perfect tack/gybe every time. You could also do the same with mark roundings. - Set up a series of perfectly optimized (computer modeled) sail trim modes that can each be accessed by the press of a single button. With the trimmer only being responsible for small adjustments for shifts/puffs/ducks etc. The possibilities are truly limitless, and in an event where being just 1 knot faster all the time gives you a massive advantage, this is really where I think the winning team will stand out.

Yes, the AC boats are getting ever more complex; what if they used CrowdStrike and couldn't sail for the Cup? (great video. thanks!)

New zelands main sheet looks so clean.

More education! Keep it coming. It really makes me enjoy watching the sailing even more

jeez’ you guys are going deeper every time. good job.

SO lovely and nerdy! Txs so much 4 keeping us updated on details! I learn much each time and have sailed since I was 7-8yrs

The teams and the sailors gets a vote from me. This is amazing stuff. Nobody else is doing this (they think they are 😂), so thanks 🎉

Excellent once again - the AC organisation need both of you on the core team!

On the topic of creating thickness in the sail profile between the skins... I have been rewatching the previous cup races, from the pre event onwards. And one of the main things i have noticed is that Ineos seem to not be able to create as thick of a profile in the mainsail. In particular, this seems to restrict their power production in the speed build before foiling. So, while you share good points here about creating smooth flow off the mast, i do believe that being able to create more power for takeoff is actually a key component of being able to "thicken" the profile.

One of the few times I've really enjoyed being taught! Thanks guys.

Thanks for posting this info. Very informative.

These AC 75,s are becoming more technical than F1 I reckon. Love it! Cheers Mozzy.

Fantastic bit of tech talk. Thanks yet again.

Hey guys, another great analysis. Have you noticed that team nz seem to be sailing with leeward heel quite often? Particularly in a stronger breeze. But I’ve noticed it in most conditions I’ve seen them in. Seems to be a very different mode compared to the last foiling cup cycles.

Very informative and engaging - as usual! my thnx

Responding to Rob's point at about 2:40 about the jib head being locked in place by the halyard lock, it might be worth thinking about small hydraulic cylinders (perhaps with mechanical advantage to trade stroke for force) one at the lock, and one at the tack, moving in a coordinated way to control sheeting angle, and differentially to control luff tension.

Great job guys