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Sea Wolves - The new America's cup boat! AC75 Technology analysis/Deep dive special! Auckland 2021
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- Опубликовано: 15 дек 2020
- With less then 6 hours to go till the start of the first event in the 36th America's cup series, It's time for a deep dive / thorough analysis and talk about the design, function and racing edges, of the brand new AC75 sailing monsters! With all 4 boats in the water and the race set to start, we now have the info we need to start the conversation which will no doubt continue over the next months and in 2021, right up to the moment the last race finishes.
Then we will know, but for now, we get to analyze, speculate an presuppose and this is exactly what we are going to do today. In an nearly hour long special, with an stunning introduction by non other than: XXX secret XXX. You don;t want to watch the first race without first having taken on board all the design and racing insights we will discuss today!
Also see our special on the history and origin of the America's cup races: • Sea Wolves - The Ameri...
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#AmericasCup #AC36 #Auckland2021
Wow!!! Just WOW!!!! Thank you so much that was utterly priceless to see the America. What a privilege.
Thank you! We are so glad you liked the special tour :)
2nd. What Mr. Puxley said!
@@martyhill8342 Thank you so much! It was such a privilege to be on Florian's show :)
I had no idea American was still around!!!! Very cool to see such important history so well cherished and maintained! I’d love to have the chance to see her in person some day!
@@zbeekerm it is a replica, but a very good one. wikipedia says the original boat fell into disrepair until the shed it was stored in collapsed and the whole thing was scrapped and burned.
Just a small point of correction for you:
The foil cant system is not powered by the grinders at all. It uses a separate battery pack that is charged before the race. The grinders only provide hydraulic pressure for managing the sails.
The foils cants DO use hydraulics though, it is just they have an electric hydraulic pump to provide pressure.
Other than that small correction, great video!!!
Thank you for that insight.
true
Cracking presentation - foil arms are rated over 35 tonnes.
I heard that the skeg acts as an aerodynamic endplate during the transition to foiling. When the boats first start generating lift, without the skeg they would lose power when the high pressure air bleeds over to the lower pressure side. The skeg being in contact with the water stops this, allowing them to generate more power until they are fully foiling. Once they are full foiling, then you don't want the extra drag, as drag is the proportional to the square of the velocity. Therefore, they should be out of the water after the transition.
The skeg has three functions. They separate the high and low pressure. They capture the air on the side of the leeward foil and provide a ground effect lift like the Russian Ekranoplan. Then they give a gradual transition from water to air.
@@SxWerks can you please elaborate more on how they “capture air on the side of the leeward foil and create ground effect lift”? I have heard this explanation from multiple different sources (who probably know better than I do) including the Italian Quantum sails guys, Vittorio and Pietro, however I’m not sure I follow the logic and the phenomenology. Part of the confusion may stem from the fact that I’m an aerospace engineer (and fluid dynamicist) and the definition of “lift” is much less ambiguous when talking about an aircraft than a sailboat-especially a foiling sailboat. Furthermore, traditional ground effect lift is usually attributed to image vortices: virtual reflections of the wingtip vortices below the plane of the ground due to the no penetration boundary condition that induce a (virtual) upward flow between the two image wingtip vortices increasing lift.
Now, when the skeg is out of the water, a large vortex should be present and attached to the leeward side of the skeg and hull. This lacks the symmetry of wingtip vortices, but I can see how an argument might be made that the image vortex provides more upwards induced flow along the centerline this is a form of ground effect lift. But does this really outweigh the low pressure of the attached vortex pulling the leeward flat portions of the hull down and vertical portions of the hull to leeward? After all this sort of attached vortex is what creates the low pressure responsible for the lift of delta wings and in this case such a low pressure is pulling the hull in the wrong directions (down and to leeward). I suppose that leeway helps your VMG downwind, which may outweigh the harm it does to VMG while traveling upwind? But apparent wind speeds should be higher upwind so I would expect the penalty upwind to outweigh any benefit downwind. Additionally, due to the asymmetry, the image vortex will induce additional flow from windward to leeward enhancing leeway and side slip.
Am I missing some critical phenomenon for how the skeg creates ground effect lift?
Or am I misinterpreting lift to mean a force acting in the upwards direction when the boat is floating at rest in flat water? (Versus, e.g., lift created by sails which acts with a forwards and leeward component)
As a CFD guy I readily admit that it’s more or less impossible to accurately intuit the causes and relative magnitudes of many of these forces, however I have not yet heard anyone give a detailed explanation of the phenomenology behind the “increased ground effect lift” argument/explanation and I am therefore not confident in my own assumptions and understanding what people (who have done the calculation or know what they are talking about) mean by this statement.
Forgive my informal and imprecise description typed out on a tiny phone screen... not my best work but hopefully clear-ish enough
@@zbeekerm 👍🏽
Skeg in simple term is to prevent mix flow between right n left side, and create single flow from front to the back .. mixed flow from the side will stall wing shape of the hull, and lost the lift .. like on plane you get flat spin on topgun movie..
Great video and an amazing intro!
Personally I think that the main purpose of the skeg on ETZ, with its flat bottom, is to act like a kind of water-ski to provide a little bit of extra hydrodynamic lift. That helps get the boat out of the water earlier, but more importantly I think it helps the boat stay up. Right after a tack, the new foil and the sailplan might not be at full power right away, but the boat might still have enough speed to slide along on its water-ski skeg and the partially working foil for a few boatlengths until everything is in the zone again. Landing and having to take off again will cost a lot of distance, so anything which prevents an occasional landing will be a huge boost to the overall result.
Thanks Troy for showing world history through AC hull shapes! And the AC presentation following it was amazing! Totally worth the 51 minutes.
Great show! I think one reason why they opted for soft sails is that the hard sail is very hard to handle as you have to demast the yacht to be safe in harbour. This increases the handling costs and makes everything more difficultand time consuming... Really appreciate your shows :)
also the condistions in new zealand means the winds are higher and waves compared to burmuda which the was last cup . that is why Cats are not popualar in higher winds and waves
I think there was also the desire to foster a development which was more applicable to crossing oceans. It´s a huge limitation of most hard sails (wings) that their area cannot be reduced, whereas soft sails can be reefed (or lowered entirely, in extreme conditions or running repairs). Whilst the specific implementations in this AmCup are not reefable, the concept lends itself to reefing, hence the trickle down effect for real-world sailing
Great video!! these boats area absolutely insane. who else can't wait to see the racing start?!?
such a clear description> we are looking at a huge number of exceptional complex leading edge technologies all interconnected. sailing will never be the same
Another amazing video! Thanks to Troy for joining
Yes, most instructive and thought provoking presentation Florian!
Yeah, and just imagine his wife in the next room, thinking "Florian you were screaming in the last 1 hour into the camera..." :D
I am not sure if this was more recently addressed but I think that you are mistaken about the skeg. I don't think that it has anything to do with a transition. If you windsurf the first time you rake the sail back and close the slot between the sail and your feet you will notice a jump in power. My understanding is that this stops the wind from leaking under the sail and thus reducing the pressure difference. Closing the gap seals this off and you gain lift without adding drag. Since these boats fly above the waves the wind can go under the hull. The skeg therefore closes this gap without smacking the waves with a large wetted surface. So it adds lift with minimal extra drag. I believe that this is also why they are trying to fly low (there may be other benefits). Also, I don't think it is fair to say they reduce power once they are up on foils. I think that they maximize lift to take off and then reduce drag once they take off. Maybe this is what you meant.
Hi Florian, thx. for again another fantastic episode. An idea for next special on AC could be to focus on the teams. What are the various roles, how do they work toghether to steer the boat, etc...
No doubt the various hull shapes under the wing theme reflect the different compromises designers are making to optimize these new boat/plane objects. One will emerge the winner. And no doubt future boat designs will benefit. Thanks also to the owner for showing the beautiful America schooner. Great respect for all wood boat owners...
Terrific technical look at these boats. You mentioned so many points I never thought of. Love it!
I have been in love with America since about 8yrs old and winning Round Isle of Wight was one of the greatest moments of my sailing career. The history is not lost in those moments.
Wikiflorian, thanks for this highly educational session on AC75!
45:50 "White Knuckle Science" lol I'll remember that one. Great video. Thanks buddy
Fantastic video! One of your best....the tour of the America made it for me. Thank you for sharing this treasure with the Sea Wolves!!
Big Thanks to Troy, and great overview of the AC75s - there is so much secrecy and still no idea if NZ are really ahead of the rest or not roll on tomorrow for our first proper look 👍😀
Many thanks to see inside America - hopefully it’s there when I get back to San Diego to see it for real - beautiful yacht -Troy 🤩🤗and Mr Wolfie for another great show ☕️Cheers Pete
Please come visit us! We'd love to have you aboard :)
Great to see America!
Thanks so much, I am so glad you enjoyed Captain Troy's tour :)
Brilliant start (toast).. great scoop Florian..
Wow¡ What a joy To see The América! Love it! About if foilers aré boats, My grandpa died deeply convinced that fiberglass sailboats werent really sailboats. And i remember endless debates about monos vs multis, and multihulls aré kings in The charter industry, and liveabords. Maybe many SeaWolves will be foiling in a few years!!! THANKS FLORIAN for another xcellent show!
Perhaps we're missing something by not racing beautiful boats like America, but those foilers are looking very exciting. Another great video.
Next step : Ask Burt RUTAN and his Canard configuration (aircraft ....) ! Same lift, less drag .... It will be certainly very interresting ! ....
Good luck.
Whoa. Getting into epic territory here with the tour of America. And nice touch with the music in the background ... again Florian, you are killin' the details. 😊
Thanks so much!
Thank you all for such a fine program. Thankyou Troy, for opening up your "home" on the sea! What a beautiful ship. Astonishing, vessel! Thank you, Mr. Sea Wolf, the aero-dynamic qualities of these new designs are just amazing to sea. Lol.
Thank you so much! Come aboard the Yacht America anytime, we'd love to have you aboard :)
Wow. Well done to an amazing piece of history relayed. Fantastic lesson Troy.
The show was too good , so very interesting with Troy and Florian
Very interesting episode Florian. I know some of your AC75 content was speculation and guesswork, but I think you'll not be far off the mark with most of it. However the "America" overview - just fantastic. Quite incredible that you got that content. The sheer craftsmanship that built, and maintains, a boat like that is beautiful to behold.
Thanks for the insight into all of this. I am a total noob regarding sailing. Stumbled across a video of the AC75 class by accident and was immediately intrigued.
I will definitely check out the AC.
Watched some videos of the Christmas event in Auckland.
And regarding the "flying boat" I'll just say Ektranoplane - ground effect vehicle.
Maybe the same principles apply here.
Go Seawolves!! Great intro of Troy. Now that’s talking sails! (and hulls, off course) Back to the beginning.. Nice!!
Great presentation as always...but...it was especially nice to see Yacht America and Captain Troy, here from our shared hometown of San Diego! Great boat, great crew, and always a pleasure to share the experience with folks who visit from out of town (Next Level Sailing, whale watching, etc).
Interesting video. I owned and sailed a windrider rave about 20 years ago, recording a best of 26kn. The “flight” level was maintained automatically by trim tabs on the foils. A “float” rigged on an arm over the outriggers and through some levers inside the aluminium foil adjusted the trim tabs continuously depending on the how the float was positioned in the water. The rudder was controlled via foot pedals and the lift trim-tab on the rudder was controlled with a little lever on starboard side. It was great fun and quite challenging. I did learn more or less on how to fly it as of about 8-10kn and more of wind. I would imagine that a similar mechanical system would be implemented on a AC75 possibly via some internal pressure sensor or some Flettner type rudder or trim tab inside or around the main trim tabs to make the whole system work. I would have a hard time imagining a human doing it... but of course, I don’t know.
Superb work again today Florian! Was amazing to look over America and have that personal touch to see where Troy watches Sea Wolves from! BIG thank you to him! Also appreciate all of research that went into the Americas Cup boats information. Your show is the best way to start the day for us here in NZ with a morning coffee. .......Now I'm waiting for the racing to start in Auckland!!!
So lucky to be so close to the action :)
that was a great show; from the historic schooner to the current AC75 aircraft; presented varied and with lots of detail; I am always excited; very well done
Man this episode was awesome!!! So great to get some inside into the first America’s cup boats.
Thank you for the great video, both the segment from Troy and especially your comments on the technology. Thanks for all of your "research" into the subject. Very well done!!
Wow... A fantastic tec talk. That was awesome!!! So much info and explanation.
And loved the presentation of America with Troy.
Soooo cool.
Actuallly the italians have two skippers, and they don’t change sides when tacking. Amazing to see how your show evolved from a small interesting chat with the viewers to a big show with professionals involved. Congratulations Florian, keep it up :)
You are the greatest! Bringing Troy to your show. Very creative and bold to ask him. Congrats!
Wow wow wow wow, thanks Troy, thanks Florian!
Please introduce the Foley Artists who did such a wonderful job with the creaks. Very Realistic!
Sorry, yesterday Im to bussy to see the show, but today, yea! Great show! Congratulation! Ist so amazing, so cool, so intresting. Carry on, see you again! Cheers!
Amazing session - keep on flying with the eagles
Awesome Troy! Great to see you! It's been too long. I am sharing this with my friends who are also AC fans, some of whom I have brought on board for your whaling charters .
Geweldige video, interessante bijdrage van Troy! Dank Florian!
Great presentation thanks Florian. A few thing you didn't mention maybe due to lack of time. I'm not an 'insider' or 'expert' so please check the facts.
The mainsails are double skinned, with two tracks on the mast. Very unusual.
The size, area of the foils is important. Large area for low wind range, small for heavy air. Why? because big foils will lift at a lower speed but have a lower max speed because higher drag. Small foils will lift later (or not at all in low wind) but when running have a lower drag profile. Foil for the day are selected according to the wind forecast.
Flying a foiler is more tricky than an aircraft in this respect: There is a very narrow allowable 'altitude' band. Too high and the foils break the surface, all lift lost, crash down. Go too low and you drag the hull. Most foiling dinghys have a mechanical water surface sensor, a wand, which partly automates this. I dont know how the ACs do it.
A wierd thing about these ACs is the heeling (roll) axis. Any other boat, it heels over and rotates about an axis running through the boat fore and aft. With these the rotation axis is a line drawn between the active foil and the rudder foil, a diagonal line to one side of the boat. Thats why, if they get it wrong either the boat rears up and crashes or the reverse, the bow gets suddenly slammed down.
Keep it up bro, you're doing great!
Loved the tour of the America. Need to see more videos of it sailing. Also wonder if it has ever sailed around the Isle of Wight.
Hi Ben! Thanks so much. We have not yet sailed around the Isle of Wight, but Captain Troy did sail it from San Diego to Maine in 2016. We certainly would like to get to the Isle of Wight! If you have any ideas, please let us know :)
@@nextlevelsailing5200 Stage a race with an English counterpart. I bet the AC Organization might find sponsors.
Hi Florian, fantastic video! You’ve put some work into creating this episode! And it is much appreciated. “Wing” technology is extremely interesting and future development will be fascinating to observe. As a non sailor, I hope it does not cause the end of sailing boats as we know them. Hulls in water driven by sails is not only a beautiful sight but a skill which hopefully will continue to evolve too.
That was an amazing toast! And, one that was fitting for an amazing boat. Howl! Howl! Howl! Your channel is becoming a must watch sailing channel. 👍✊🙂
Excellent video. Got a new subscriber for this one.
Great show. Amazing how much good content you were able to pack in for limited production time (and staff 😉) Thanks!
Great video really informative 👍👍👍
So cool to see Troy Sears and the America, what a ship!
Boat
Great video, thanks for sharing
Florian, I’ve been windsurfing for years and I’m also a pilot for many years. The current AC 75 concept is the closest to the two principles merging into one. I love how aerodynamics and hydrodynamics is merging into FluidMotion.
@Kor Kiley just like with a fully cambered windsurfing Sail, outhaul adjusts the camber ( depth) of the foil. On my slalom racing sail I have an adjustable outhaul connected to both sides of my boom. This allows me to adjust the sail camber between upwind beats and a broad reach. The AC75’s have a very large windsurfer sail where the sail effectively wraps around the mast and remains two seperate “sheets” till around 2/3 of the chord line. Just like a windsurfer sail. The AC75 have hydraulic outhaul which is adjusted in synch with the sheet position and angle of attack. . All controlled by the “ mainsail trimmer “ who’s monitoring a pressure distribution diagram of the main sail on a waterproof monitor. They require a computer to tell them when the main sail is at optimum efficiency. As windsurfers, our brains and body act like a human computer since we do all this instinctively by “ gut feel”. The same way a pilot should be be able to fly the wing on an aircraft by “ the seat of his pants”. 👨✈️🇦🇺
@Kor Kiley our windsurfing club welcomes people your age. You are never too old to go sailing. inverlochwindsurf.org.au/
thank you for your one of a kind informative productions. excellent.
Well done! Very insightful & articulate.
Great episode! Wonderful morning toast and yacht tour of the America by Troy and Ashley! Hope I have an opportunity to visit San Diego and enjoy whale watching on the America!
Thank you for this amazing sailing videos. I watch you every single day and I love it!
Regards from Rune, Norway.
Thank you :)
Wow that was cool Florian. Very very good explanation of the AC75. It‘s funny to see your enthusiasm for this airplanes äh sorry boats!
Very interesting! Thanks , and terrific intro by Troy, great to see the origins.
Great Job Troy, make SD proud!!!
Thanks Florian, will share this with my son, a keen sailor and consultant engineer. Very interesting.
Great video
The tailtales may actually as boundary controls like the goofball dimples but better as they deform but not as well as the wing feathers of bird near stall.
A plane flight direction is controlled by the ailerons and the roll or banking. The rudder is secondary. These sailboats do not bank in the turns, the hydrofoil must be doing the rolling to provide extra lateral force required to change direction as the sail force change drastically
It is not easy to fly an hydrosailboat or hydrosailplane.
Sailploat ...
Amazing .. thanks you so much ..
Awesome episode! Congrats
Great video. Very informative. This design is going to change the America's Cup.
What is amazing is that 6.5 Tonnes are supported on a foil. The force must be huge.
WOW! I loved the intro with the guy that owns America. Was going to send in a video of me talking through my RS Aero dinghy but not sure it stacks up now :)
All the boats are very impressive, but the NZ boat's deck looks the cleanest aerodynamically. Watching the races, the NZ team keeps low and the bulwark cockpits separates them better from the air rushing over the center uninterrupted. I'm for the US team, but it seems intuitive from an aerodynamic sense that Team New Zealand has a better design. But racing will prove this out I'm sure.
Very interesting. As an ex (is one ever ex?) yacht designer I found this all fascinating. My thanks to Troy Sears for the tour of his boat and his comments about design. Looking at the half models it was sad to see how the 12 metre rule distorted hull shapes but I suppose any rule does this in one way or another. The thinking behind the foiling boats is fascinating though to me they look weird and not beautiful. I'm probably too old! I'll watch the series with interest though. Thanks for a great video Florian, you must be putting a lot of time into making these
Really great! You are good at explaining!
Another great video ! I look forward to these daily updates ( i wish the coffee cups where microwave safe - I'd buy one)
I guess the skeg also directionally stabilizes the boat when the hull starts to get contact with water. If the bottom would be flat, the sudden increase of drag would make bearing downwind very difficult and induce torque to upwind direction which would need rudder compensation and thus slowing the boat. Now, especially with the flat bottomed skegs, the hull has minimal contact and less torque against the foils, helping to maintain speed in turns like jibes and rounding downwind mark.
Finally the ice has been broken. The 4 regattas on the first day of the America's Cup World Series gave particularly beautiful images in a day with perfect weather of the Hauraki Gulf: wind between 15 and 18 knots, sun and flat sea, which allowed the teams to experience the performance of the their boats in real competition after years of training. The day saw some important gaps, but not only that. The starts were all very close, even more than expected, and the last race was run entirely on a tightrope. Good conditions for the show in general.
The first challenge between Luna Rossa and Team New Zealand goes to the hosts
The program saw the opening match against Team New Zealand and Luna Rossa's challengers. For the Italians, therefore, immediately the most difficult challenge. The pre-departure was immediately very tight. The wind had turned particularly to the left and New Zealand took that part of the line by force. Luna Rossa, however, responded by putting the defender in difficulty, aggressively "pushing" him towards the line and then turning and starting on the opposite tack, with New Zealand struggling to cross the line itself.
First advantage for Luna Rossa then which however quickly vanishes. A combination of something imperfect aboard the Italian boat, coupled with better wind pressure on the left side of the course gives New Zealand the first crossing ahead of the Italian boat, albeit slightly.
However, something continues to not work in the right direction on Luna Rossa. The boat flies higher than the New Zealand one (with too high a height it loses efficiency) and has some problems even in the turns. After the first crossing, New Zealand literally flies away with almost 900 meters of advantage at the end of the first beat. From here on, the situation will tend to stabilize, a sign that on the boat owned by the owner Bertelli, helmed by Francesco Bruni and James Spithill, things have at a certain point started to work properly. The AC75s are extremely complex boats even in on-board systems, and having problems in these first official races was expected by all teams. The fact is that New Zealand takes home the first point of the series.
Team Ineos UK in huge difficulty
The second test of the day saw the challenge between the Americans of American Magic and the English of Ineos. The regatta of the latter actually lasted a few minutes, after which they began to show problems in maintaining themselves on the foils, also seen in the test races, with high-speed dives in the water and violent braking that gave the Americans a victory. more than easy with a detachment even beyond the maximum time allowed. Luna Rossa also easily wins against the English, who will eventually have to withdraw from the regatta due to the succession of technical problems on board. The aggression shown at the start by the Italian team was beautiful: knowing the weak point of Ineos, which is that of having a hard time starting again once he got off the foils, the Italian team managed to "fit" Sir Ben Ainslie in a corner of the start with a very aggressive leeward tack, which plunges the two boats into the water.
From here on it becomes a walk for Spithill, Bruni and companions, who at the moment of the start fly towards the line at full speed with the English in an embarrassing difficulty.
Bad situation for the union with the most budget available (we are talking about 120 million euros, against about half of all the others) which will have to find solutions quickly, given that from January the points will weigh seriously.
American Magic hit in a wonderful regatta
On the other hand, it was a beautiful show in the last test of the day that saw the Americans of American Magic, helmed by Dean Barker, against Team New Zealand. Something is wrong at the start on the New Zealand boat and American Magic immediately starts strong and ahead. New Zealand remains in close contact, at times it seems to have the speed to get closer, but a problem with the handling of the keels forces the home team to very slow turns, throwing it back whenever it seems in a position to attack. This was until the last lap of the course, when the problems were finally resolved on New Zealand and the defender showed all his speed (and above all his ability to tighten the wind upwind).
The Americans are not there to be caught and a battle is born made of pure match race, simply run on the edge of 80 km / h. At the last buoy the boats arrive together, with New Zealand taking in and seems to have managed to complete the comeback. Burling, the Kiwi helmsman, however, is perhaps too enticed by the possibility of increasing the advantage and leads the Americans too far off course, incurring a penalty, albeit doubtful.
The Americans take the lead again and manage to close in front of just 12 seconds, hoisting themselves at the top of the general classification with 2 points, ahead of Luna Rossa and Team New Zealand with 1 point and Team Ineos with 0.
Obviously it is too early to draw any definitive conclusions, especially as the event does not award decisive points and therefore no one knows how much the teams are really pushing. First impressions certainly see the New Zealand hosts very strong, but that's no surprise. Luna Rossa seems to have a bad customer in the Americans for the Prada Cup. The program of the second day includes 2 challenges between the Italians and American Magic, which promise entertainment and to be significant in trying to understand something more about values in the water.
so much good information. You rock!!!
Many thanks Florian for the video. Could you please cover at some point the different roles of the crew members?
Thanks for the America tour from San Diego!
Very nice tour of America! I was lucky to go on that boat years ago when (on loan to?) the San Diego Maritime Museum was sailing it out to watch whales. And it is more beautiful in person.
Wow! You keep topping yourself!!
The design of the skeg, must also affect slamming as it comes off the foil. Also I think they must be minutely altering the flaps on the foil when the water gets more choppy to prevent the nose down attitude the one in the video got when it pitch poled. You know its going to be fast and hairy when they are all wearing crash hats.
Thanks Florian, that was a really interesting explanation of the boats.
The mainsail is actually double skin and one team i think the kiwis or Italian don't have a boom but hydraulic jacks that can pull the two skins hence allowing much more control .
Looking forward to another super show Florian!
The Skeg is an air dam....that's why the boom also hits the deck. Without the skeg air passes from high pressure to low pressure underneath the boat. The increased skeg area prevents this air passing....
Awesome show thank you Florian!!
Florian..... Chapeau!!!
\
Thanks for the interview. Great content!
The AC75s are like flying fish, part fish and part bird. They swim and fly. The hydrofoils while smaller than the sails, take advantage of the fact that water is 1,000 times denser than air. The hull shapes are now designed for aerodynamic vs. hydrodynamic fluid dynamics. This is why I like the skeg as it can provide a ground effect lift like the Russian Ekranoplan.
Zeer leerzame video. Wat ik graag zou willen weten is hoe ze de zeilen hijsen en strijken. Wat me ook opvalt is dat ze ondanks de enorme zeilen toch heel rustig wachten na afloop van de race, langszij een RIB. Bedankt voor de video. Super!
The skeg is because the hull has no centerboard or keel, so as long as you aren’t foiling, it’s still a sailboat. And sailboats need a lift medium underwater to create speed at all..
But because a keel or centerboard keeps dragging while ‘ flying’ , they choose a skeg, in order to to stay shallow enough while foiling, and effective enough while sailing..
Kiwis designed the better hull in my opinion. Their skeg serves the same purpose as a water ski during jibes and tacks, enabling their boat to skip off the water and keep from sinking into displacement mode less frequently than other boats. Combine that slight advantage with the lower center deck and higher crew “gunnels” so obviously designed to convert wind sheer to lift as air moves under the hull, and across and through the deck. Hence my opinion the Kiwis win it on design. There’s more to racing than design, of course. We’ll get some deliciously competitive races and see mechanical, rig, and fitting failures, with strategic and tactical drama, etc.. But all things being equal, the Kiwi design wins it on ability to transition and capture additional lift from their water-ski skeg and air lifting hull and deck design-the other designs will require more consistent and higher wind conditions with flawlessly precise boat handling to capitalize on any Kiwi mistakes if they hope to win a race. That’s how significant I believe the Kiwi design advantage is at this stage of the game.
They also seem, at this admittedly early stage, to be ahead in foil efficiency (they have the smallest foils, and yet can fly in the lightest winds) and in mainsail shape control. To take just one of many examples: they seem to be able to deepen the chord at the foot of the sail remarkably quickly, which is an essential prerequisite when the boat drops off the foils and the apparent wind flicks aft and flickers out.
Obviously they also need a sudden ease to prevent a stall (of both the sail and the rudder), but there is no difficulty arranging this on almost any boat. It´s my guess (at this early stage) that this is part of the reason they sometimes seem able to stay up better than their opponent.
Another thing about the skeg, it helps on the “flat belly dive” thing. Imagine that huge flat bowl hitting the water like concrete
And about the sails, I’ve seen in some video that they are able to deform it in specific ways in order to optimize shape
I agree with you, Florian. Being called a "monohull" is kind of a joke with these boats. I really kind of find it disingenuous with the Kiwi's and others who were complaining during the last cup about catamarans, and saying they wanted to go back to monohulls, whereas actually, there's hardly any difference between the 2 as far as- once you're on foils, you're on foils! And they plan (and you can see they can do it) to be on the foils 95% of the time- including on tacks and jybes.
The 'monohull' in this instance really doesn't mean much, and it's definitely not "better"- it's just a different 'base' for the foils.
The cats are far more dangerous in a capsize and are more likely to pitchpole, and to break up in either situation. They also present significantly more aero and hydro drag, which explains why these monos are so much faster to windward than their predecessors, sailing faster *and* pointing higher. The AC75´s upwind Vmg is already a major improvement on anything hitherto achieved by any sailing class. They also have the potential to be substantially faster on a reach. Even though the new course has no reaching leg, TNZ has already matched, in this very first regatta, the fastest top speeds only recently attained by the more highly developed cats, with their much more sophisticated (but impractical and unseamanlike) hard wing sails.
@@Gottenhimfella That's great, and I appreciate that they are a step up in speed, etc. But that's not the reason people were complaining when the cats first (and later) were being used. You didn't really answer to my and Florians main point that these aren't really 'monohulls' in any kind of traditional sense- it's just a single platform for the foils instead of 2.
Also, I don't believe anyone pitchpoled during the actual racing, and I don't know if we really know how much safer these AC75's are.
@@windwardpro Team NZ pitchpoled during a race in Bermuda, and have capsized in training with their first AC75. In these cases the boat behaved like a cat and a mono respectively. Moreover, AC75s behave like a monohull when in displacement mode, just as the catamarans behaved like cats ditto. Given that you seem happy to refer to the latter as cats, I'm not sure what the problem is with referring to the former as monos?
@@Gottenhimfella Right. No, I don't have a problem with them calling them monohulls (because they have 1 hull)- but I am saying for all the earlier hype of wanting a monohull, they have FAR, FAR more similarities to the foiling cats of the last cup than they do to any regular monohull.
I like these boats, but a plus for the cats was, at least they could keep going at a decent speed when off the foils. That is definitely the achilles heel of this design.
@@windwardpro At first my impulse was to repudiate your (latest, and final) claim, but I realise now that the claim I *thought* you were making was different from the one you were *actually* making.
I realised this having decided to review race 13 of the 34th AmCup in San Fran, which was a re-run of an abandoned light-wind race earlier in the day, during which neither cat could foil. However one of them managed to do a horizon job on the other through consummate skill much more than luck, and was robbed of a win, and the AmCup, only by the Race Director inexplicably neglecting to shorten the course, as the rules allowed, so that the leading boat could finish within the time limit (which it just failed to do on the unshortened course).
The second race was held in 10--13 knots. There were times when neither boat could foil, but you are quite right: the difference between foiling and not foiling was considerably less marked for those AC72s (big cats) than the AC75s (big monos from this series). And you are right, it WAS a more compelling race.
Personally I thought the cancelled race was even more compelling, because one team did an absolute masterclass in light airs sailing on a big cat. If the rule had been slightly differently worded, to REQUIRE (rather than just allow) the course to be shortened, that, to my mind, would have been the making of that class. Especially if they also permitted flaps on the main foils, so the ridiculous efforts by the grinders were not necessary.
I am happy to live with the risk of capsize or pitchpole on big cats if the sailors are. They bear that risk, we don´t. I do think their having a hull over each main foil is a safety advantage, especially given the foil tip is well inboard.
Fantastic episode!
Cool guest, well done Florian.
I think the skeg also helps to limit the touchdown drag and provides a transition between flying and not flying