Revolution by Evolution: *NEW* Cup foils analysed

It has been a huge week in the America's Cup, with no less than three completely new foils revealed within seven days.
Where have these new designs evolved from? What are the America's Cup engineers trying to achieve?
0:00 - Intro
0:39 - Team New Zealand
1:35 - American Magic
7:48 - Luna Rossa
10:25 - INEOS
16:15 - Alinghi
Recon video and photos credit to Recon Photographer / @America's Cup
#MozzySails supported by Allen Brothers (fittings) Ltd
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#AmericasCup #AC37Recon #AC37

[@richardcannon7327]

I am a F1 Aerodynamicist and we ran turbicules on our rear wing for several seasons. Tbh it’s a bit of a fad thing. At some incidence you get vortical structures shed. But they are not a big player. May be a sign of who the aero is more than anything else. For us they were mildly positive but it was hard to justify the weight. It might open up the incidence at stall or generate slightly more lift at max aoa and I guess that is probably the attraction might give lift off 1/4 knot earlier and cost nothing at fill speed. Re the strut vs wing it’s possible that the wake of the strut is reduced by travelling into a favourable pressure gradient of the wing and this also explains the cl tweak to the foil flaps. Glad to see INEOS finally have a proper aero on foils all the previous ones looked horrendous. The flap fence we would consider a rotation fence. And is the cuff not just drag reduction to help lift off

[@Nickle314]

They've existed on gliders for a long time. The idea being that if you get chaotic formation of vortices they are larger than if you trigger them directly. Plus its cheaper than blowing the wing. What I've not seen, and I wonder if it works is this. You clearly get a vortex that the wing tips. However you also get vortices at other places. How many do you get? I suspect its speed related. So what if you trigger the vortex deliberately dependent on speed, with a small movable vortex generator that moves in and out. Does that reduce the chaos and hence reduce the drag? Same thing for the position of ailerons. Should the end be close to where a vortex is generated, say at thermalling speed or should it be at a different location. If you google "The tip vortices trail back from the wing tips and they have a tendency to sink and roll toward each other downstream of the wing. Again, eventually the tip vortices dissipate, their energy being transformed by viscosity." It brings up a page with some diagrams It shows just after the quote above, the flow over the top surface, the bottom surface, and how that generate vortices along the trailing edge. How many? I suspect less at higher speed than low speed. Where is another issue but I suspect they are roughly equally separated.

[@CarkeekW]

Please comment again on future stuff Richard, it's really interesting getting your pov . Would the tubercles stop the foil slipping sideways to some extent and promote better vmg even if they have slightly higher drag?

[@Paul_C]

Isn't Red Bull technology doing some Aero work for the America's Cup? Seem to remember Newey was involved.

[@Zickafoose2024]

I wonder, would it reduce resistance when the foil is plunged into the water at the beginning of a tack?

[@guydinsdale3645]

Zipp introduced this on their carbon road bike wheels. I think they said it was to help in cross winds which ties in with your comment on high angles of attack.

[@AR_434]

We tested tubercles or serrations on the leading edge of fan blades when I worked for a fluid dynamics chair in Germany. We looked at their effects on the overall performance and aeroacoustics. In optimal conditions they were always worse than standard blades, but in highly throttled operating points or with highly turbulent inflow conditions they offered some benefits, reduced flow separation and made the operational window wider. Our conclusion was that they introduced longitudinal vortices that reenergized the boundary layer downstream, stabilizing the flow on the suction side, preventing flow separation and/or reattaching it faster than a normal blade. Maybe they try to improve takeoff speed and the foils behavior at very low speeds.

[@guglielmoscovazzi2572]

Hi Mozzy, I have a Ph.D in CFD. I agree with everything that Richard Cannon has said. But I read that one of the advantages of the tubercles leading edge is that on average it improves lift and drag performance of the direction if the flow is not coming at the optimal angle of attack. Now if we think about the swell in Barcelona and the foil going through the waves, maybe the tubercles will help making the foil more progressive in it reactions and avoid a drastic loss of lift in near stall situations. During maneuvering we might have similar advantages. On a formula 1 the advantages are probably less evident, unless we consider the effect of natural wind that can tilt or shift the true wind direction with respect to the wing. I’m any case, Richard has had certainly a lot more experience than me.

[@tube_de_siguro]

Considering the F1 Teams' problems with crosswinds in Miami, the tubercles might have actually played a role if they were used more agressively on the cars 😅

[@paulsmith4220]

I'd have thought that the foil was always subject to a sideways slip load which would cause a angled flow across the foil. As noted a bigger seaway adds more chaotic flow. So just maybe, but at 40kts plus in a water, any parasitic drag?

[@martinmoxon2723]

Thanks again Mozzy. There has been some examples of tubercles used in cycling over the last few years. Filippo Ganna had a 3D printed bike when he set the world hr record last year and it had tubercles on the seat tube and seat post. This was said to help keep the airflow attached for longer in an area of high turbulence (right between the riders legs). Also Zipp and Princeton Carbonworks have wheels that have a sawtooth rims. They help keeping the airflow attached especially when the yaw angle increases (i.e. crosswinds)

[@barryscott6222]

Re the new Alinghi foil, the interesting part is rather the swept plan-form, rather than the tubercles. As you say, the tubercle idea has been talked about for decades, and no-one has ever managed to make it work meaningfully. They are effectively vortex generators, which theoretically help retain attached flow, and/or less drag. But inevitably, there works out to be easier and cheaper ways of creating the same desired result. Also whale flukes operate through a much bigger range, of angle-of-attack motion. Whales are sweeping them around, all over the place. While Hydrofoils are typically/predominantly, set and forget.

[@fargneta]

Although it is not my first language, and you are speaking in technical terms, you always manage to give me a complete analysis on the subject of foils. I am happy that you are able to convey your great passion to us. Greetings from Rome Italy.

[@woodmonster16]

Thanks Mozzy - now I’m going down a tubercle rabbit hole right before bed 😂 EDIT: A bit of reading indicates that the prescience of tubercles on a leading edge reduces the tendency of a foil to stall and when it does it loses lift gradually rather than suddenly. I wouldn’t be surprised if Alinghi RB are having issues in the sea state in Barcelona and are trying to find ways to reduce the effects of loss of laminar flow when the foil leaves the water. Seems to increase lift as well, so maybe we’ll see teams bringing out super high aspect ratio foils with tubercles?

[@richardcaw]

yes correct. In aviation they use mini vortex generators on top of the wing, This is to break the turbulent air at the rear of the wing into smaller packets when near the stall so the air breaks away in a controlled manner instead of suddenly in a big lump.

[@williamfennell8175]

I’m aware of a few academic/ basic research efforts to quantify the effect of leading edge tubercles when added to a more traditional foil profile Empirically, the span-wise distribution and magnitude of the tubercles was evaluated over a range of velocities and angle of attack in a small water tunnel . As mentioned above , one observation was the benefit of delaying the onset of stall conditions . I don’t believe there were any significant benefits to optimal lift or drag coefficient..just more “forgiveness “ in suboptimal conditions.

[@peterbrown7965]

Would be great to get the boys in to discuss some of these developments when you can. I found the three way conversations really interesting and often different brought fresh perspectives.

[@johnmarkgatti3324]

good to see some leading edge playing going on [ and I'm not paying for it !] . the tubercles ,been waiting for 10 years [?] for this to get used , the idea came from the chief designer , when wale watchers noted humpy backed whales were more agile than hydrodynamacists thought was right and proper ,for whale shaped bodies . They found the leading edge bumps allow far higher angles of attack with out flow detachment . The thinking is you get lines of higher pressure that will stick to the foil shape better , these HP lines attract ,or entrain , more of the lower pressure flows , a bit like the NACA vents ,a small amount of air bending into a hole draws a lot more in . The STOL airplane crowd are useing lots of little right angle foils along the front of wings to give vortexes or high pressure lines ,increases their angle of attack ,giveing slower speeds before a stalled wing . My thinking is they should negate the need for fences and anti vortex wing tips ,plus being able to run smaller ,less area drag , foils . the thinking on hump backs was their foils are about 30% to small for what they do ,so some potential in there [ possibly make the other teams blubber ?]

[@fettermatze]

The turbicules are really interesting - as in my opinion they do highlight an aspect of the foil application that is not talked about as much. The foils are not only providing lift out of the water but are also angled to provide "lift" against the side-way slip much like a centreboard would. This lift can also be used to provide sideways lift to the boat (like a trim-flap on keel or the windward heel in a Moth). With more angle comes more tendency to stick the leeward tip of the foil out of the water - and even more in wavy conditions. This would cause very unstable flow conditions around the outer foil section and the turbicules can help to keep the flow attached longer or reattach faster. The potential gains are showcased in the cycling examples that @martinmoxon2723 mentioned. In my opinion that's also the reason why we only see them applied to the outer section of the foils. In summary: I think Alinghi goes for a smooth/straight foil on the inside as it provides the lowest drag or best lift and the turbicules on the outer part of the foil because they are planning on running the foil highly angled and partially out of the water in wavy conditions.

[@mrl22222]

Paul Bieker has been applying tubercles to foils for 15 years now. My understanding is that they're good at disrupting flow (think pressure) running along the leading edge and generally help prevent large vortices from forming and disrupting the overall flow. For them to be effective you have to have the vortex problem to begin with.

[@mertonhartshorn5974]

I'm reminded that early aircraft had scalloppedd trailing eddges to the their wings and as aerodynamics improved spats and fairings began to clad the undercarriage, then materials and power plants improved and any gains superseeded by new problems to solve. We are watching fantacstic experiments in the trade off beween wetted mass, lifting area, drag and lifting moments and also time. While playing for percentage improvements there is the bigger picture of where meaningful gain can be made as each element is brought into play over time as the system is deployed. An increase in thrust or lift from a slick foil may well be delayed by turbulance and drag as the arm snicks into place, so thats a half-second lost in a turn. Equally pulling the foil out of the water need to be clean. And everything under the water has a boat balanced on top of it! Thank so much for these preentations - it's keeping me interestedd in a type of racing I didn't much care for before!

[@hendrikvandeperre851]

In surf foiling there is one brand that’s now down to its second generation of foils with tubercules. Takuma with their Kujira foils. The original series provided a much slower stall speed and bigger tolerance to angle of attack changes and turbulent water flow ( messy sea state) than all other foils on the market. As well as incredible grip in turns. Those foils were very hard to slip out and very tolerant to ventilation. Sound to me like all those attribute would be a great benefit for foiling in Barcelona in light puffy conditions with a messy sea state. I like their direction of thinking.

[@learigg]

Fantastic analysis as usual.

[@MozzySails]

Cheers Davie!

[@alienlifeformresearch2280]

Thanks Mozzy for comprehensive foil overview. Good to see Alinghi designers peeking into world of asymmetrical foil wing designs for the first time. Though scalloped leading edge on outboard wing seem a modest start.

[@tanguyz]

Nice video. We use tubercules or bumps design on surf foils (kzbin.info/www/bejne/jJWal2eBhbd2gdE). We work with Laurent Borgna who practice those design since many years. We have make several test with and without bumps and the major benefits of the bumps are in low speed conditions: it’s working like smoothing the CL curve and pushing more the stall angle. Worst « global »CL/CD with bump design but offer top control during hight acceleration turns. It also prevent the ventilation progression along the LE during tips breaching (probably why alinghi use it on external foil part) sorry for my bad french english

[@angusaitken7211]

I just spent a semester building and testing tubercles on hydrofoils. One of the things I found is they help reduce drag and ventilation that happens with surface piercing foils. Essentially its stops the air from travelling too far down the foil and helps direct the flow at the water / air interface...

[@MozzySails]

Is there any reading you can recommend?

[@sly6627]

Thumbs up again for the best AC insight on the web. I would love to see some footage from the cameras mounted on the various foils but that's never going to be available at least until after the cup.

[@MozzySails]

That would be cool. They might release some nearer the cup once the secrets can't be copied

[@nicolaslyon4342]

Excellent as always, thanks!

[@ferdypl322]

Juan K said that they used them on the clubswan 36 to increase the stall angle (albeit with an increase in drag). Pinarello, Princeton and Zipp have also used them for similar reasons. Maybe Alinghi are using it to attach the flow faster when the board is dropped.

[@nh-ss5pw]

Excellent!

[@charlottescott7150]

Great thanks

[@redcavnz9618]

Nice work , super interesting

[@christromp5897]

Thanks Mozzy. Love the breakdown and analysis.

[@MozzySails]

Thanks!

[@isaacislaughter]

You are my primary source for news of the America's Cup. Cheers Mozzy

[@jameslochhead5950]

Great video very interesting information looking forward to your next one

[@MozzySails]

Thanks James

[@zlm001]

I'm glad there's still a bunch of different approaches.

[@freeaccess5905]

Very nice summary

[@dulls8475]

Thanks Mozzy from Lymington

[@jamesaron1967]

Best AC tech reporting as always 😎

[@richardnorthover8995]

Thank's again Mozzy, great roundup of the development paths and some insiteful "best guesses" of the philosophy changes from team to team. WOMAS, interesting thoughts on the tubercle leading edge. Because ALINGI RB are the only ones testing at the AC venue their findings could be inteesting.

[@user-xc1ml9kt2c]

I am the originator of the tubercle concept of the humpback whale flipper and it does work.

[@MikStorer]

My reading is that Tubercles delay stall at high angle of attack. To turn a 30 ton whale takes sustained angle of attack over quite a long period. If a hydrofoil has a high angle for attack for very long ... I would suspect something is very long. The humpback cruising speed is 2 to 7 knots ... so sustained angles of attack at slow speeds. The humpback tops out at 13knots. Tubercles have been tried on a couple of yacht rudders. More lift at higher angles of attack might be more worthwhile there. But two famous examples the best part of ten years ago and I don't think there are very much more than two sets around now. Not exactly bursting onto the racing scene. We will see of course within a few weeks. Interesting that the tubercles are on one side ... I guess they can swap sides and have the tubercles outboard or inboard. I'm expecting them to disappear without trace in a month or so. But if not ... then I've learned something.

[@tomgruitt6563]

Interesting!

[@zumpkin]

Thanks Mozzy! It's always a pleasure to view your videos, I am surprised you didn't start to build your foil yet 😂 Would be interesting anyway to hear what is your opinion on those tip caps that AM uses: are they covering something or just protecting the foil during the warehouse operations? Also is there a limit of revisions that the team can release? Thanks again 🙏

[@michaeljames1857]

Legend

[@12killerfish]

I've messed about with tubicules on kite foil wings. They feel as if they reduce the stall speed slightly but I found with the bumps near the tips of the wing creating pressure differences, increased the chance of large ventilations down the wing compared to a flat wing. But cool to see someone trying them out.

[@uberseehandel]

why we haven't seen more of these cetacean style foils previously, surprises me. On a foiling project some years ago this was a feature we wished to test. It will be interesting to see if there are benefits in the real world. Nature usually ends up being pretty efficient in these matters.

[@paulsmith4220]

Not many whales etc have them. Does that tell 8lus anything?

[@gerhardeide]

Hi; again a interesting Video with a lot of information from some blurred pictures. Amazing! Just a small question from the sideline; could these spats on the foil arms be more for lift getting the hull out of the water and/or during foiling, rather than area needed for actuators or weight?

[@chriscochrane6319]

Really good video thank you for all the photos. Mike Arnold did a lot of work on intersection drag with his AR 5 light racing aeroplane videos on you tube which I think is pertinent regarding the positioning of the foil/ strut exactly as you suggest .Al Bowers ex nasa did a lot of work on the Prandtl D wing architecture which is similar to Alinghi . Re tubercles I believe Bieker and JK believe they delay ventilation of the leading edge where it breaches the water surface with less drag than a fence.

[@TornadoCAN99]

I recall hearing these type of leading edge lumps called Trip Turbulators. My understanding is they help keep a supercritical wing section from exceeding stall point by making vortices in the boundary layer.

[@alyen11]

My guess on the turberculs.... replacing a long stagnation ligne on the leading edge by multiple stagnation points=less drag.

[@TechnikMeister2]

Hydrodynamics and aerodynamics are not the same. The structures need to be quite different to produce lift. For a wing in the air, the forces come from above as a low pressure area is created above the wing, creating lift. In a wing, like a foil under a boat, the lift is created by water pressure on the underside of the foil. The shape is quite different. You also get much greater water resistance than air, so the water foil has to be much thinner. If the AC designers don't understand this, then I am available to take over. Hands up those who would thike the AC ro revert to the 10m rule. It was so much better.

[@franspigeaud2199]

I guess all teams are quite aware of this….

[@potNuts]

Would a dimpled surface on the foil allow a team to run a slightly higher angle of attack with the same drag level? Even if not, would a similar modification at least at the T-joint be potentially beneficial?

[@janholland2224]

Good stuff as always, appreciated. Glad I am not the only one struggling how to pronounce tubersomething. You'll find lots of stuff out there referencing either directly or indirectly a Mr. Fish (Chester Uni). Personally I found one of the more interesting reads a 2012 Uni of Adelaide thesis by Kristy Lee Hansen with the title 'Effect of leading edge tubercles on airfoil performance' . Cheers and thanks, J@n

[@MozzySails]

Thanks, I'll check his work out. Come across the name already in some brief searching

[@hippopotamus6765]

Alinghi is going with the owl wing design . Leading edge nodules to reduce noise. Very interesting

[@philforeman7102]

Hi Mozzy is there any positive reason for canting the foil on a hinge once it is down ? Also what about allow the working part to rotate say, 15 degrees

[@AdrianThompson-wn8eu]

The INEOS 'W' foils looked very agricultural too me, with lumpy appendages housing the flap actuation mechanisms, so it is with some relief to find they are heading in a more positive direction with a slicker looking foil package. They do seem to be a few iterations behind the best teams though. The turbicules were fitted to sailboat rudders a few years ago, but interest seems to have wained, suggesting that, although interesting, they may be a trend rather than a solution. Great analysis Mozzy - Thank you.

[@airtensor]

Good to see the end of Ineos W foil. All the appendages for linkages and dihedral changes and high taper ratio meant it was never going to be fast. The new Ineos foil looks pretty ; Elliptical, little or no external junk, Good fairing between flap and wing. Also the flap chord ratio reduces towards the tip, which probably helps to keep tip stalling with a lot of flap applied. Flap is quite large. Could they maybe could reduce the flap size as a percentage which would give them a stronger wing structure so they could go for a thinner section. Not sure about the upswept tips. They are used on airliners because airliners wingspan is restricted I believe. A simple longer wing is better aerodynamically. Maybe the same rationale here? Anyway I predict Ineos new foil is what boats will converge on. As regards the zig zag leading edge on Luna Rossa, as has been commented, this may help to soften the stall, but it will not be fast, so I predict it will not be on the winning boat. Ultimately you just need to hang on your foils ( as Burling did last time) so low drag at high speed is what you to win on these boats. That will look like a simple elegant foil, which the new Ineos foil is I hope!

[@matthewmorgan9269]

Tubercles are beneficial on the leading edge of a foil (of whale fin) to avoid stalling at high angles of attack. In the case of a humpback whale, the tubercles enable the whale to make sharp turns when hunting schools of fish. My guess is that the tubercles on the outboard blade of the Alinghi foil assembly prevent cavitation for the first few seconds after entering the water or possibly during sharp turns in a gybe. Most of the time the blades remain at a relatively low angle of attack.

[@martinformlos9826]

Are morphing surfaces on foils a theme of research? i remember a discussion on that in the 80s or 90s, concerning glider profiles, but i never have seen more than prototypes.

[@Fr3DDy73]

regarding the chrome foil by americans, I reccomend you (if you speak italian) the channel "Sail Ring". They had a nice vid on that foil recently, and they think is an actual metal foil, evidence of a precise line of thoughts: reducing the overall resistance (same strenght than carbon at less weight --> less surface --> less spray). This is achieved by the reduced dimension of the "missile" (i lack the precise term) that the carbon foils have to fit the weight measurements of the rule.

[@Fr3DDy73]

kzbin.info/www/bejne/aJbJiKmHot5mn9U there it is

[@MozzySails]

Thanks Federico. I watch quite a bit of what they do, but have to rely on Google auto-translate which can inaccurate!

[@Fr3DDy73]

@@MozzySails eheh I can get it

[@michaeldonovan9334]

Are the teams allowed different treatments on the inboard and outboard sides of the foils or are the tubicules only on one side of the bulb for testing?

[@MozzySails]

For the race foil they have to symmetrical. But on these test foils they can do what they play around a bit more

[@michaeldonovan9334]

Thanks! Really enjoy the channel, looking forward to more!!!

[@duncanadams6993]

Did I hear that on the new Ineos foil the flap is only the bottom surface so kind of a half flap? What’s you thoughts on that? Presumably reduces drag but does it make the flap less effective?

[@MozzySails]

Yes, I think some moth foils a similar flap where to top (unbroken) surface is flexible and acts as the hinge

[@attainconsult]

what is the equation lift vs drag but with these boats there is also cavitation

[@andyschuster9829]

There was a SNAME paper on the leading edge knobs of whale fins. If I remember correctly, there was a performance increase for whales. Im not sure it applies to high speed foils.

[@AnttiBrax]

Gow much flex is allowed in the foils? Can they engineer the bananana foils so that they straighten up under load and "break out of the box?"

[@MozzySails]

They are allowed to flex under hydro loads. But they can't bend due to flap / actuator movement

[@richardcaw]

Im not sure how they are hinging and moving the single piece flap on a curved surface like that. I really hope they are not still going for the slotted flap and moving it back and down

[@user-xc1ml9kt2c]

The tubercles along the leading edge of a wing-like structure mainly delay stall by creating a series of paired counter-rotating vortices which accelerate and energize the flow over the tubercles and keep the flow attached. As a results, there is an increase in lift with higher angles of attack and compared to a straight wing, there is no drag penalty prestall and a lower drag poststall. This was validated by model testing at the US Naval Academy. The tubercles act as aerodynamic fences without the increase frictional drag of a physical fence. This decreases spanwise flow and the tip vortex which increases efficiency, reduces induced drag, and results in noise reduction. There have been over 500 scientific articles and meeting presentations published on the subject. The benefits of the tubercles dependent on the geometry that is used and tuned to the wing-like structure and its function. The tubercles have been applied to jet engine stators, surfboard fins, hydrofoils, swim fins, sailboat rudders, keels, and sail masts, dive planes, truck mirrors, race car spoilers, bicycle wheels and frames, aircraft engine ducts, stabilizers, aircraft wings, paragliders, propellers, helicopter rotor blades, fans, compressors, tidal turbines, and wind turbines.

[@scottseale]

Whats the function of the slight dip or depression of the trailing edge at centre of foil, many are adopting?

[@MozzySails]

interesting question. It does seem to be a feature that is increasing. Perhaps to accelerate the flow off the back of the vertical and maintain flow there at the expense of sacrificing some over shape in the lifting wing. Pure speculation on my behalf, would be good to get views of someone more knowledgeable than myself on it though

[@scottseale]

Makes sense. Will keep an eye out for any replies with further insights. Thanks.

[@vwwestfaliasyncro913]

Is the Alinghi foil asymmetric as well the outboard wing looks a lot shorter ?

[@MozzySails]

They are symmetric, apart from some small details. However, a lot of the profile shots have some skew to the image as one tip is always nearer to the camera than the other

[@vwwestfaliasyncro913]

@@MozzySails Thanks for clarifying :) This reminds we of the fins we used in the 80's on wave boards to tackle cavitation (I think they were called Toucans)

[@Silvius.2]

How many foils every team able to building? They must counting every new? They able building so many they want before AC 37 boat finnished?

[@MozzySails]

They can build 4 new foils on their test boat. Then for the AC75 race yacht they can build 3 foils, but they all have to have the same design (so two for racing and one spare). INEOS have built all 4 of their test foils. Luna Rossa have built 3. American Magic have built 2. ETNZ have just launched their second (since this video). Alinghi have built 1.

[@GermanGreetings]

It`s a grand banks.... or the schooner America in your background ?

[@hummerlionn]

Does anyone know what kind of airfoil they use?

[@lewisa5062]

Wait ... are the foils interchangeable from port to stb? If so have alinghi just created a "2 for 1" test bed. And potentially doubling their foil design allowance?

[@MozzySails]

I think so. That would be the only way of really testing either side of the foil, because if they leave it on port then outboard side will always perform differently due to it's proximity to the surface. How good the data will be from switching side will be another question. It will always be a different day, with different wave angles and patterns which might make pulling conclusion out difficult if it's not a clear difference

[@lewisa5062]

@@MozzySails agree but they should be able to get reasonable data from performance and cameras ... as you say it might be 80% as good as symmetric data but now you have twice as many foils to gain data from. Very smart move by alinghi ... disappointed in myself and other teams for the light bulb not flashing on

[@-M.O-]

I would assume those Turbicules are “just” vortex generators that reenergise the boundary layer and thus reduce or delay stall. You can look it up it is more or less the same reason why Golfballs have dimples. But (at least as far as I know) creating the small vortices does come at the cost of extra drag except of that one speed region the foil (or better the turbicules) is designed for. Same goes for the golf ball. The dimples are only useful at typical Golfball speeds. Anything above or below it is going to do more harm than good. Another guess is that they do it to reduce ventilation but it is just a guess. I cannot propose any concrete mechanics on that.

[@-M.O-]

kzbin.info/www/bejne/nJTNkqt5Ysprpbs Basics for the Golfball

[@radarriau]

Great show... Holy cow, insanely complicated flaps. Love the camera application. Makes me feel lucky I'm at Windfoiler and just have to worry about dynamic weight changes and fixed pitch adjustment in the stabilizer wing on the fuselage, or rudder angle in the case of the Sail GP F50. I always wondered about turbicules on whales and hammerhead sharks. They're not exactly slow animals. However, never really looked at tuna and swordfish fins that closely. They look pretty sleek, certainly pretty sophisticated.

[@macscott5290]

As always great video. Re the tubercules at the end. Probably been on the same web pages as others and looks like in theory they help increase lift and reduce spanwise flow of the fluid. So could reduce the winglet/end plate size for the same overall effect? Other thoughts are 1) do they increase the effective overall length of the leading edge? Not sure. And 2) swept wing aircraft work better at high speeds, straight at lower. The wavy front edge gives both angles to the fluid flow at different points on the wing so could help create lower speed lift with less flap for a slight reduction in top end efficiency - with that being countered by smaller flaps and end plates? Im an engineer but not in fluid dynamics. Why dont you ask Hannah Fry if she’s interested in commenting? Only half joking here BTW….

[@igbc176]

Latest paragliders have those tubercules and they perform better for avoiding the wing stalling without sacrificing performance... I think

[@MozzySails]

Really? Do you have a video link I'd like to take a look

[@igbc176]

@@MozzySails kzbin.info/www/bejne/jInXaqWwgJ1pjc0

[@paddledogs]

@@MozzySails Not the OP but here: kzbin.info/www/bejne/jInXaqWwgJ1pjc0

[@charlestoast4051]

Looking at how different all these foils are suggests to me that the gains are marginal, altho everyone seems to now have reduced or zero overlap between the lower arm and the foil, perhaps indicating a measurable benefit from that arrangement. Fluid dynamics will always remain a black art, so I expect to see many more designs tried out.

[@jsytac]

🇬🇧 leverage = lever 'idge 🇺🇸 leverage = levva 'edge

[@maurhum]

Juan Kouyoumdijan rudders....

[@jameslittlewood7663]

Not an expert - the opposite - but I’m glad to see the end of that thing Ineos was dragging around.

[@lewisa5062]

How has the alinghi foil not been protest, taken off the boat and 1 foil allocation taken away plus a penalty (assuming its touched the water). Foils must be symmetrical. This is same as the ineos tow mast issue. Can't be gaining information from non complaint items

[@MozzySails]

The symmetrical foils only applies to AC75 race foils. These are all LEQ12 foils, for which the only rules is the total number they are allowed to make (4) and the % they can be modified (20%)

[@lewisa5062]

@@MozzySails so out of all the teams you are saying alinghi are the first/only team to find this loophole?

[@MozzySails]

@@lewisa5062 Luna rossa have run different tips inboard and outboard (shown briefly in this video). So not as obvious as Alinghi, but similar thing. Personally I am not sure how useful testing a half and half wing is as the outer wing is operating at the surface which could cloud any results as the tip breaks through the waves

[@lewisa5062]

Interesting ... so there is nothing stopping a team installing a full sized AC75 foil on an LEQ12, adding a heap of weight to the boat and testing the characteristics

[@paoloradaelli7120]

Excellent discussion (in Italian) on Alinghi’s corrugated foil by D’Albertas and Morani here kzbin.info/www/bejne/pKSrgpqFZcyUl8k. They hypothesise that the unusual paint scheme might hide some microvortex generators.

[@MozzySails]

Thanks, I will give it a listen later

[@paoloradaelli7120]

They also speculated that the biggest benefit might be in the presence of swell, because this generates unusually high angles of attack.

[@smb5655]

print

[@wouterlauwereins-jf8ng]

Takuma has this whale thing on their wing en surf foils.

[@bernardboden537]

to undersand placemnt ofe the wing and the "arm" kzbin.info/www/bejne/omiTdXytaKmYrq8

[@josephthom6309]

why can't the foil wings just be made out of some really heavy material like tungsten? you'd surely then get the best of both worlds as you still get the leverage as the weight doesn't need to be pushed up into a spat, but at the same time you could keep the below water presence low as you wouldn't need extra weight in bulbs. maybe materials used are standardised?

[@thedoctor907]

there are in fact regulations regarding materials, Eg paper is out, No cardboard. or any cardboard derivatives. But in all seriousness there are regs on materials you can't use "exotic" materials in your ballast. I think that is one of those things where it comes down to making sure its not a case of having the most money to spend on materials, and also just to stop someone making the internal of their foil out of something like depleted uranium to make the foils much smaller than anyone who can't get it.

[@MozzySails]

The materials they're allowed are limited to a maximum density equal to lead, so they could pack more mass in, but lead isn't very useful from a structural point of view within the wing. There is good possibility any ballast they mount up on arm fairing will be lead though

[@woodmonster16]

I dunno, I like the idea of the Americans having depleted uranium in their foil arms 😂😂😂

[@duncanadams6993]

Did I hear that on the new Ineos foil the flap is only the bottom surface so kind of a half flap? What’s you thoughts on that? Presumably reduces drag but does it make the flap less effective?

[@macscott5290]

@@MozzySails is that average density of a total device or maximum density of an single constituent part of a device? Assume its max for any material used?

[@rogerpearce5650]

Hi. Love your work. Henri Pitot would not like your pronunciation of his name! Being French he would prefer it to sound like 'peetoe' rather than peetott! Unless you're pandering to our American cousins who can't even say 'lever' correctly...... I'll get my coat.

[@gordonyork6638]

Boy, you sure have a way of obfuscating your illustrations. Why do you have this terribly busy background? It makes it visually confusing. If these are photos taken while sailing do some post production photoshop and clean up the backgrounds.

[@DumfriesDik]

Thanks for you insight and observations. I am so tempted to go to Barcelona next year but is it better viewing on the telly with all the AR overlays?!

[@MozzySails]

Good question. Barcelona will have a good atmosphere though which is hard to create at home no matter how good the footage

[@lasral22]

I was lucky to go out and watch a couple of the races from the last cycle. Trust me , you have to see these things sailing with your own eyes. They are incredible! You wont regret it.

[@DumfriesDik]

@@lasral22 Think I may start planning!!

[@TheLDunn1]

Hump back whales aren’t exactly the fastest things in the water though, are they? If you were looking to nature for inspiration you’d be looking at the Sailfish (clocked at 68 mph) en.m.wikipedia.org/wiki/Sailfish