I am reminded of research in to the shape of certain whales' fins, and also the surface of the skin of sharks. Creating 'micro eddys' reduces drag. The AC has always been a 'playground' for innovative designers, and so wonderful to see that continue. Some want to see the AC dragged back to the 1980s and 1990s, but that perspective does not pay enough 'homage' to the designers of the past, nor to the skill of those who are engaged to win the next edition. I love sail craft of every age, and so I am of course excited by this edition of the AC. Very thought worthy vlog.
Agreed. The "it's flying not sailing" lobby completely miss the point that the AC is now a commercial enterprise first and foremost, and the foiling boats just attract a lot more eyeballs than conventional keelboats.
Good analysis of movement of water in the wave. However, consider also that water is not just moving up and down, because the wave/swell is moving laterally, the water is flowing towards the peak in opposition to gravity. This is how dolphins/porpoises "surf" within a wave like a hang-glider in an updraft. The water behind the peak will be dropping, but also may be aeriated, and thus increase the risk of a foil ventilation event - hence the "tubercles." Your analysis is a great illustration of how the rules stifle true innovation.
I assume the symmetry rule exists so you only need one spare foil to cover breakage. Otherwise a team basically has to have four foils to cover themselves.
@@powerlooper9121 the maximum number of foils is limited to try and restrain costs (not going to work of course, but that's another argument). So having them fit both sides is pretty important to help ensure the maximum amount of racing.
The holes at the tips are all about turbulation or ‘blowing’ to unstick and accelerate the lamina flow. They are exactly on the right point of the chord for that. I think the flexi part is simply sealing to cover the flap mechanism and keeps the aerofoil shape as perfect as possible. On the delta shape, I’ve always seen it as a nigh speed feature which in theory, wouldn’t help the boat to foil at low speed, in fact the opposite, so very interested to see if they are trying to change the wing shape from a fast speed delta to a low speed straight trailing edge with a ‘scissor’ flap arrangement. That could explain the flexi material? What I really don’t understand is what effect the tubical leading edge has on the laminar flow particularly over the top of the ‘wing’?
tubicals create exactly the same "effect" as VGs but without the VG (foil) drag aspects .. a difference the bulges have is they create high & low pressure "streams" down the wing/foil cord rather than the tornado effect vortex with considerably less friction drag & lost flow (energy) as well as a notably thinner boundry layer as a consequence .. the pressure streams also reduce span wise flow root to tip in the lower pressure trailing 2/3rds of the wing/foil improving lift & reducing parasitic surface flow drag as well as aiding flow to reattach when venting or cavitation happens .. this is a reason why most of a foil tends to generate most of its lift over the leading 1/3rd of its profile hence the aero balance point of wings typically between a 1/4 & a 1/3rd of a wings cord .. ask any aero modeller where a planes static balance point should be .. THATs because of the strong (small (close/tight) boundry layer) laminar flow airstream "accelerating" over the leading 1/4 - 1/3rd of the wing cord vs the decelerating trailing 2/3rds to 3/4s.. & its proportional to the size of the tubicals which in turn are proportional to the cord of the wing foil.. this has been known & understood since the 30s but an association with whales wasn't known then .. it was in responce to the effects of fabric & frame biplane type wings & their wing rib profiles vs a constant smooth profile
Fascinating analysis, as usual! It's an interesting point you make about the asymmetry - it's against the rules, so can't be used in the races, but might enable testing on opposite sides of the boat. I take it the foil is made in unit with the lower part of the arm, and that the joint to the main arm is symmetrical, not handed.
That knobbly leading edged fin reminds me of whales and Humpbacks with witch I am familiar, attached flow is everything and stopping aeration creeping along the low pressure side of you foil is the trick.
Another great video, thanks. Have been wondering for a while, all the efforts going into foil development I am sure makes sense, but apart from the more obvious efficiency lift vs drag and ventilation and cavitation minimisation what are the other objectives and do these have more of an overall impact. Last time round, other key factors seemed to be speed at which foiling started, carrying speed through tacks and establishing better high modes the later being one of the seemingly big differentiators. What in the foil design is more likely to improve the high mode ability of these boats. Of course a lot to do with the aero/sails as well. Can't wait for next installment.
that "indentation" (if I may call it that) on the outside of the port side foil reminds me of a humpback whale pectoral fin. that takes me back to (if my memory isn't playing tricks) the AC in the 80's, when 1 boat got a shark skin texture hull paint job (or am I imagining that?) Cheers from Portugal
correct .. but the shark skin cause & effect are quite different .. humpback's are where the concepts were devised from although .. it was know & understood in the 30s with studies of biplane type fabric & frame wing rib bulges .. development then sort richoche'd off in a different direction .. now its come back .. lifes funny like that .. humpbacks are better designers 🤧
I just took a photo of Ben Lexens Australia 2 test keel yesterday. I was surprised that after 42 years you could still see the same DNA between that design and the modern AC foils
Thanks for keeping an eagle eye on the progress of the teams Mozzy. I don't claim to follow it all very closely but that's the first time I've seen one of the teams out in a open sea swell and Alinghi seemed to be handling it in style. Respect! Good for them if they can upset the established order on their first outing.
With regards to the foil tip ventilating, you may indeed prevent the ventilation spreading, as the span wise flow of the foil is towards the tip. You will however get a pitch up moment as the CoL moves forward on the foil. A pitch up right as ventilation begins is going to be bad if it cannot be prevented by the elevators.
@@Errol.C-nz by elevators I mean the rudder elevators that control boat pitch angle. Not the flaps on the main foils. A fast enough pitch down moment from the rudder elevators could prevent the pitch up from the movement of the CoL on the main foils.
I may have missed something. Have you explained to us about the effect of different positioning of the foils on the arm? Some further fwd than others? Many thanks
Are you shure at around 5:15 there is no mix up of pictures before/after sailing? To me the first picture looks like some flexible material got ripped away from the wing during sailing. Specially at the top those holes I suspect them to be some sort of fixation for the flexible material to be bonded on
Yes, I am sure. The photos I have are timestamped and the the first one was taken on the day the foil was 'revealed' but the boat did not sail. The second picture was taken from before sailing the next day.
Tom, you are hecka smart at this and I really enjoy your analyses. One point is that the speed of the circulating water “particles” is very low compared to the water displaced above and below the foil surfaces. Still I’m intrigued by the idea that having a portion farther below the water would reduce the overall effect of the circulation in extra lift or fall. I always thought that having the foils anywhere below the surface gives that level ride, but is there still some lift induced by that internal wave circulation?
More analysis please. Geometry, math and some simple calculations could go so far here. SOME DEBATES. Maybe test exaggerated foil ideas to show what's going on.
the down side is .. the up side of the wave circulation the foil passed through .. has a circulation down side .. as the foils pass through .. different if it was just a surf board .. but its still only relative to foil attitude to incoming flow
Fab update thank you Mozzie!! Are you also tracking the Ocean Race?? Pretty amazing watching the records tumble across the Atlantic on the last leg. What are your thoughts as to how much further that record can go? And what tech transfer is there from AC to Ocean?
Thanks for mentioning that. Not being a surfer I had no idea about these foils. Probably where Alinghi got the inspiration for their test foil if not the humpback whale itself.
Whales fins -having wavy leading edges-was said to be better for flow, and I melt wondering when I’d see it on boats. Also, I sometimes wonder about slightly softened trailing edges using silicone….
Regarding interference at the midpoint ends of the two foil flaps during articulation, could one solution be to have the foils at slightly different angles of attack when they move? One end could then overlap the other during movement.
That would create a rolling moment that would then have top be comensated by asymmetric flap movements - draggy, and probably against the rules as well I suspect.
Be interesting to know what the material that pulled away was about. Was it supposed to pull away and allow what was underneath to be exposed? Would something like that be legal?
My thought was can you present a symmetrical foil for the rule measurement and then have erodable sections that "unexpectedly" erode/ablate during use to produce an unsymmetrical foil?
@@roythompson6137 if a part breaks during a race, then it is likely not to be in measurement. At the end of the race the broken/used part is removed and replaced by another compliant part for the next race. I suppose it's treating foils like a F1 tire. It starts off legal and is consumed during the race and replaced as required.
I think it's more likely that the material is simply not standing up to the forces imposed on it by the water. It's doubtful that random, ragged ablation would lead to improved performance. It obviously does have some flow-viz paint effect, since the affected areas have to be experiencing greater disruptive forces.
It looks to me like the chord length of the flap (which I'm assuming is the silver coloured element) plus the chord length of what we are assuming is a flexible element make up close to 58% of the foil chord. Assuming the leading edge is structural as is the trailing flap, are all the hinge mechanisms hidden in the central black section? You discussed off axis hinge centres a while ago, which could mean the actual flap deployed or extended aft of the structural part of the foil. The flexible part, which you point out looks to have been eroded away might act as a faring as well as containing the hinge bits, however I doubt any skinny flexible faring or boot could stand the velocity of water or the pressure to survive for long. Just think how often we replace simple rudder fairings.
I just took a photo of Ben Lexens Australia 2 test keel yesterday. It’s easy to see the same DNA between that 42 years old design and the modern AC foils.
It seems like the optimization of CFD models need to consider the percentage time the foils spend in the various regimes including different weather conditions and speeds, not just straight line sailing. Do you know if they do this? I liken it to how wind tunnel testing of bike racers consider yaw angles of the wind and other assumptions, or base it on real world data of the conditions experienced on a given racing situation.
Almost certainly yes. I believe this was part of the the innovation of the Juan K Volvo boats (ABN Amro, Ericsson, Groupama). They put the Volvo race course into a routing model showing that if you optimized for reaching/running you could go a lot faster (and spend even more time reaching/running).
Do you think the lost material simply hadn't cured properly? Sounds like it had just a few hours overnight. It appears that there're plenty of drag forces in play to strip those areas bare again.
I personally believe foils will be a small part of the all over performance as all foils are with in 1 to 4% in difference , Lift , drag , wetted surface > The big one is the sails , shape & aero dynamic shape change in the smoothest way to the couse sailing , Use of the angles sailed .
thats like saying a race cars engine is everything .. the tires arent important .. water is 800 time desner than air .. 800 times everything vs the sails .. every action (sails) creates an equal & opposite reaction (foils & keels) .. its ALL relative !!!!!!
@@Errol.C-nz Its not as if there's a Hull in the water , These machines are all about windward sailing & sail shape , Angle of attack , Smoove clean wind flow , Lift THAT IS THERE MOTOR .
Can a foil be switched side? Any insight into how the hydrofoil sections separate from the arms? Always assumed they where ‘one piece’ Cheers for the posts, great to see these boats in detail
if they have to have "tubercules" on both L/E then experimenting with them on only one is questionable. Wouldn't it make more sense to one foil with the straight L/E on both sides (of the leg) and the other foil with "tubercules" ? could they claim their foils are symmetrical (about the boat CL) ? or is "symmetry" defined in the rule as about the leg CL ?
It would be interesting however there are quite a few risks with it. Read through this for a bit of a brief on some of the pros/cons. en.m.wikipedia.org/wiki/Forward-swept_wing
It'd be nice if someone could measure the bumps, angles, chords, wakes, etc for the foil and figure out what speed and flow direction the are optimized for hydrodynamically. I wonder if the tubercles are more for interference to cancel or reinforce waves and wakes. Also, don’t know if it’s just me, but it looked like they were going with massive flap angles. Maybe they need help keeping flow attached when they crank those flaps to get out of the water fast and early at low speeds. Newer is its Red Bull in this new era because he made sure he could get the wing that is the floor of the car to be at optimal angles, at as wide a range of car and environment conditions, as possible. He made sure the suspension could lock the floor angle in at whatever the required ride height needed of it. He designed the suspension around RB18/19 to always allow equations for center of pressure, induced drag, overall lift, and center of gravity not to dramatically shift as the car and suspension hit bumps, braked and rolled and change speed. Because of his suspension, the wing that is the car that also keeps the tires at peak performance, this floor wing is itself always predictable and efficient. The steady performance control allows them to show off with a double kicked diffuser to stall it out. In fact, if Red Bull put a small rear wing the diffuser flow would detach and they'd be slower then running a huge rear wing that kept diffuser flow attached. Newey and Alinghi need a foil that gives full foil control 100% of the time so that they can maximze the sail's maximum potential in all conditions without worrying about the foils. A foil with massive flaps and high speed sweeps means the foils can keep the sail's happy no matter what stage of the race and what the foils encounter. I wonder if the sweep and tubicle are meant to decrease spanwise flow outwards flowing fast pas the tips. Also, the tubicles could help with micro conditions within waves in terms of speed, angle of attack, vertical spped, height and buoyancy changing throught the height and depth of the wave, but the foils are designed to deal with all the waves can throw at them effortlessly and at many speeds and force of lift. I wouldn't be surprised if the bumps on the foil keep the wake above and behind them as minimal as possible. The half and quarterlength induced waves will maintain a high depth of flow above the wing, and behind and below the wing the air is more laminar and spanwise flow doesn't let much air get suckedmdown, if at all. The foil tip may have no wake at the tip (canceled with interference pattern) and solid, laminar, spanwise flow providing only a small narrow vortex of high speeds and vortices to create suction of air at the foil tip. It needs as much entrenched flow over the wing to keep the fluid speed low over the top wing so pressures are high above these foils with massive flow volumes. Extra vortices from foil bumps would increase control and guide cavitation problems by maintaining low P vortices to entrain and keep away cavitation gasses. Mixing air in water could be useful.
I am pretty sure that Alinghi were not a European team that won the cup. They were a European financier that funded the bulk of Team NZ to defect to a professional travelling circus.
Honestly, I'm still not optimistic about ARBR's chances watching them get up to speed on their boats. Maybe it just shows how much time it takes to come to grips with this form of boat? I guess they do have another year to get ready, and that might be enough, if they do end up launching the fastest boat.
As a Humpback Whale - they seem to think they work (From Wikipedia) The tubercles allow the very large whales to execute tight turns underwater and swim efficiently; a task imperative for the humpback whales feeding. The tubercles on the flippers help to maintain lift, preventing stall, and decreasing the drag coefficient during turning maneuvers.
Yes, as the angle of attack increases, if you can induce a little turbulence at the leading edge using the tubercles, this delays breaking the smooth flow over the wing from a fully ventilated stall.
I have to read laws again. ... It ist not forbidden flexible material to use? Why only alinghi having on foils in and outside different? And its this against law?
The foil can flex, but only as a result of external forces. The exception is areas of 'flexure' which can flex due to flap movement. But those are limited to a % of foil chord
Hi Mozzy. Great video. I found this link to tubercle foil already being sold on surfboards. In this case, surfers are pumping on the board to get the foils going and the tubercle might help since the angle of attack is oscillating. This is the dual of the wave oscillating. th-cam.com/video/MOrKRZ2z2L0/w-d-xo.html
Ventilation prevention is the game - all else is secondary. IMHO, these machines are craptastically over-engineered (i.e., they still cling to using the vertical shear on the bows on a flying hull - which causes a nice braking effect when they touch water [at least no pitchpole, like with the silly foiling cats]). And the squiggly lines are amusing. But I do nevertheless love your analyses, Mozzy.
At least the IMOCA 60s and smaller foiling offshore race boats are moving towards blunter, wider bows that allow the boat to 'plane' more easily making it less likely they will dig into the wave and experience a sudden loss of speed. In the future, I see wave-piercing bows to remain on the large foiling trimarans but not the foiling monohulls.
@@jamesaron1967 The IMOCA boats are blue water boats. It would make no sense for them to bury their bows into every oncoming sea - or what they might surf into. As re: trimarans - check out the "superfoiler" pontoon bows - they are (halfway) figuring it out.
@@powerlooper9121 I seriously doubt the Ultims will significantly alter their bows. They're doing fine as they are and the fastest have exceeded 50kts unofficially. The Superfoiler is a weird but interesting design. Not sure I'd call them true tris. Anyway, haven't seen or heard anything from that series in ages... Regarding the IMOCAS, you and I may think that it doesn't make sense but only recently have the bows began to change. The first gen IMOCA foilers had standard piercing bows and many still do. It's a function of cost as well as superior understanding of all the dynamics involved with foiling boats.
@@powerlooper9121 Yes, exactly. Which is probably why ETNZ changed the bow shape for Te Rehutai. Will be interesting to see what the teams come up with for the second generation AC75.
Keora m8t i can design some radical and tem new Zealand will absolutely definitely faster just try it out wat have teams new Zealand got to loose ☆☆☆☆☆
I am reminded of research in to the shape of certain whales' fins, and also the surface of the skin of sharks. Creating 'micro eddys' reduces drag. The AC has always been a 'playground' for innovative designers, and so wonderful to see that continue. Some want to see the AC dragged back to the 1980s and 1990s, but that perspective does not pay enough 'homage' to the designers of the past, nor to the skill of those who are engaged to win the next edition. I love sail craft of every age, and so I am of course excited by this edition of the AC. Very thought worthy vlog.
Agreed. The "it's flying not sailing" lobby completely miss the point that the AC is now a commercial enterprise first and foremost, and the foiling boats just attract a lot more eyeballs than conventional keelboats.
Good analysis of movement of water in the wave. However, consider also that water is not just moving up and down, because the wave/swell is moving laterally, the water is flowing towards the peak in opposition to gravity. This is how dolphins/porpoises "surf" within a wave like a hang-glider in an updraft. The water behind the peak will be dropping, but also may be aeriated, and thus increase the risk of a foil ventilation event - hence the "tubercles." Your analysis is a great illustration of how the rules stifle true innovation.
I assume the symmetry rule exists so you only need one spare foil to cover breakage. Otherwise a team basically has to have four foils to cover themselves.
@@samlook You give them too much credit. I would suggest the rule exists because conformity is paramount.
@@powerlooper9121 the maximum number of foils is limited to try and restrain costs (not going to work of course, but that's another argument). So having them fit both sides is pretty important to help ensure the maximum amount of racing.
The holes at the tips are all about turbulation or ‘blowing’ to unstick and accelerate the lamina flow. They are exactly on the right point of the chord for that. I think the flexi part is simply sealing to cover the flap mechanism and keeps the aerofoil shape as perfect as possible. On the delta shape, I’ve always seen it as a nigh speed feature which in theory, wouldn’t help the boat to foil at low speed, in fact the opposite, so very interested to see if they are trying to change the wing shape from a fast speed delta to a low speed straight trailing edge with a ‘scissor’ flap arrangement. That could explain the flexi material? What I really don’t understand is what effect the tubical leading edge has on the laminar flow particularly over the top of the ‘wing’?
You raise some interesting points. Thanks for insight on the various design features.
tubicals create exactly the same "effect" as VGs but without the VG (foil) drag aspects .. a difference the bulges have is they create high & low pressure "streams" down the wing/foil cord rather than the tornado effect vortex with considerably less friction drag & lost flow (energy) as well as a notably thinner boundry layer as a consequence .. the pressure streams also reduce span wise flow root to tip in the lower pressure trailing 2/3rds of the wing/foil improving lift & reducing parasitic surface flow drag as well as aiding flow to reattach when venting or cavitation happens .. this is a reason why most of a foil tends to generate most of its lift over the leading 1/3rd of its profile hence the aero balance point of wings typically between a 1/4 & a 1/3rd of a wings cord .. ask any aero modeller where a planes static balance point should be .. THATs because of the strong (small (close/tight) boundry layer) laminar flow airstream "accelerating" over the leading 1/4 - 1/3rd of the wing cord vs the decelerating trailing 2/3rds to 3/4s.. & its proportional to the size of the tubicals which in turn are proportional to the cord of the wing foil.. this has been known & understood since the 30s but an association with whales wasn't known then .. it was in responce to the effects of fabric & frame biplane type wings & their wing rib profiles vs a constant smooth profile
You think the foils don’t just flap up and down, but can move fore and aft a bit like a swing wing jet? That would be mighty cool!
Fascinating analysis, as usual! It's an interesting point you make about the asymmetry - it's against the rules, so can't be used in the races, but might enable testing on opposite sides of the boat. I take it the foil is made in unit with the lower part of the arm, and that the joint to the main arm is symmetrical, not handed.
That knobbly leading edged fin reminds me of whales and Humpbacks with witch I am familiar, attached flow is everything and stopping aeration creeping along the low pressure side of you foil is the trick.
Another great video, thanks. Have been wondering for a while, all the efforts going into foil development I am sure makes sense, but apart from the more obvious efficiency lift vs drag and ventilation and cavitation minimisation what are the other objectives and do these have more of an overall impact. Last time round, other key factors seemed to be speed at which foiling started, carrying speed through tacks and establishing better high modes the later being one of the seemingly big differentiators. What in the foil design is more likely to improve the high mode ability of these boats. Of course a lot to do with the aero/sails as well. Can't wait for next installment.
that "indentation" (if I may call it that) on the outside of the port side foil reminds me of a humpback whale pectoral fin. that takes me back to (if my memory isn't playing tricks) the AC in the 80's, when 1 boat got a shark skin texture hull paint job (or am I imagining that?)
Cheers from Portugal
That's exactly where the shape originated from ultimately, humpback whale fins.
correct .. but the shark skin cause & effect are quite different .. humpback's are where the concepts were devised from although .. it was know & understood in the 30s with studies of biplane type fabric & frame wing rib bulges .. development then sort richoche'd off in a different direction .. now its come back .. lifes funny like that .. humpbacks are better designers 🤧
Thx for your observations
I just took a photo of Ben Lexens Australia 2 test keel yesterday. I was surprised that after 42 years you could still see the same DNA between that design and the modern AC foils
Great info as always!
Great video thank you.
Thanks for keeping an eagle eye on the progress of the teams Mozzy.
I don't claim to follow it all very closely but that's the first time I've seen one of the teams out in a open sea swell and Alinghi seemed to be handling it in style. Respect! Good for them if they can upset the established order on their first outing.
With regards to the foil tip ventilating, you may indeed prevent the ventilation spreading, as the span wise flow of the foil is towards the tip. You will however get a pitch up moment as the CoL moves forward on the foil. A pitch up right as ventilation begins is going to be bad if it cannot be prevented by the elevators.
elevators/flaps .. exasperate the problem in higher lift modes at lower speeds .. its like turning a steering wheel, into a slide vs with it
@@Errol.C-nz by elevators I mean the rudder elevators that control boat pitch angle. Not the flaps on the main foils. A fast enough pitch down moment from the rudder elevators could prevent the pitch up from the movement of the CoL on the main foils.
I may have missed something. Have you explained to us about the effect of different positioning of the foils on the arm? Some further fwd than others? Many thanks
Are you shure at around 5:15 there is no mix up of pictures before/after sailing? To me the first picture looks like some flexible material got ripped away from the wing during sailing. Specially at the top those holes I suspect them to be some sort of fixation for the flexible material to be bonded on
Yes, I am sure. The photos I have are timestamped and the the first one was taken on the day the foil was 'revealed' but the boat did not sail. The second picture was taken from before sailing the next day.
Has anyone looked at dimpling? You know. That feature that made golf balls fly further.
Great video
Thanks!
Tom, you are hecka smart at this and I really enjoy your analyses. One point is that the speed of the circulating water “particles” is very low compared to the water displaced above and below the foil surfaces. Still I’m intrigued by the idea that having a portion farther below the water would reduce the overall effect of the circulation in extra lift or fall. I always thought that having the foils anywhere below the surface gives that level ride, but is there still some lift induced by that internal wave circulation?
More analysis please. Geometry, math and some simple calculations could go so far here. SOME DEBATES. Maybe test exaggerated foil ideas to show what's going on.
the down side is .. the up side of the wave circulation the foil passed through .. has a circulation down side .. as the foils pass through .. different if it was just a surf board .. but its still only relative to foil attitude to incoming flow
Fab update thank you Mozzie!! Are you also tracking the Ocean Race?? Pretty amazing watching the records tumble across the Atlantic on the last leg. What are your thoughts as to how much further that record can go? And what tech transfer is there from AC to Ocean?
Another great analysis, Tom.
Thanks!
Takuma’s Kujira foils for surfing/winging have been out for several years and have this characteristic of bumps on the leading edge to mimic humpbacks
Thanks for mentioning that. Not being a surfer I had no idea about these foils. Probably where Alinghi got the inspiration for their test foil if not the humpback whale itself.
@@jamesaron1967 whale"s don"t fly at all
@@pierpalumbo415 Neither do bicycles yet here we are..
@@pierpalumbo415 Humpback whales most certainly do, they're famous for it
I'm sure you're just being facetious but it's all fluid dynamics. Nature has always been a good inspiration for designers.
I am intrigued to know what differences the tubicals would make on tbe deeper side of the wing
what do you mean by deeper side of the wing?
@Errol Churton the inner wing of the foil, ie; deeper in the water. Not the outer wing which pierces the surface
Whales fins -having wavy leading edges-was said to be better for flow, and I melt wondering when I’d see it on boats. Also, I sometimes wonder about slightly softened trailing edges using silicone….
Regarding interference at the midpoint ends of the two foil flaps during articulation, could one solution be to have the foils at slightly different angles of attack when they move? One end could then overlap the other during movement.
That would create a rolling moment that would then have top be comensated by asymmetric flap movements - draggy, and probably against the rules as well I suspect.
@@gingermattb What if its just the last few mm's of the flaps that are offset? Any difference in roll moment would be trivial I'd think.
Be interesting to know what the material that pulled away was about. Was it supposed to pull away and allow what was underneath to be exposed? Would something like that be legal?
My thought was can you present a symmetrical foil for the rule measurement and then have erodable sections that "unexpectedly" erode/ablate during use to produce an unsymmetrical foil?
Either that or they found an ablative material that works as sort of a “flow viz” paint for turbulence.
@@chrislambourne4275 guess it depends on which part of the rules... Surely during the regata the boat must be in measurement?
@@roythompson6137 if a part breaks during a race, then it is likely not to be in measurement. At the end of the race the broken/used part is removed and replaced by another compliant part for the next race. I suppose it's treating foils like a F1 tire. It starts off legal and is consumed during the race and replaced as required.
I think it's more likely that the material is simply not standing up to the forces imposed on it by the water. It's doubtful that random, ragged ablation would lead to improved performance. It obviously does have some flow-viz paint effect, since the affected areas have to be experiencing greater disruptive forces.
It looks to me like the chord length of the flap (which I'm assuming is the silver coloured element) plus the chord length of what we are assuming is a flexible element make up close to 58% of the foil chord. Assuming the leading edge is structural as is the trailing flap, are all the hinge mechanisms hidden in the central black section?
You discussed off axis hinge centres a while ago, which could mean the actual flap deployed or extended aft of the structural part of the foil. The flexible part, which you point out looks to have been eroded away might act as a faring as well as containing the hinge bits, however I doubt any skinny flexible faring or boot could stand the velocity of water or the pressure to survive for long. Just think how often we replace simple rudder fairings.
I just took a photo of Ben Lexens Australia 2 test keel yesterday. It’s easy to see the same DNA between that 42 years old design and the modern AC foils.
It seems like the optimization of CFD models need to consider the percentage time the foils spend in the various regimes including different weather conditions and speeds, not just straight line sailing. Do you know if they do this? I liken it to how wind tunnel testing of bike racers consider yaw angles of the wind and other assumptions, or base it on real world data of the conditions experienced on a given racing situation.
Almost certainly yes. I believe this was part of the the innovation of the Juan K Volvo boats (ABN Amro, Ericsson, Groupama). They put the Volvo race course into a routing model showing that if you optimized for reaching/running you could go a lot faster (and spend even more time reaching/running).
It's a red bull team and so maybe Adrian Newey might have some magician tricks happening just like the RB19 floor.
How much articulation is there on the foil flaps?
Do you think the lost material simply hadn't cured properly? Sounds like it had just a few hours overnight. It appears that there're plenty of drag forces in play to strip those areas bare again.
INEOS had similar problems. I think there can be significant forces on those flaps and mechanisms can easily bind up with load and flex.
I personally believe foils will be a small part of the all over performance as all foils are with in 1 to 4% in difference , Lift , drag , wetted surface > The big one is the sails , shape & aero dynamic shape change in the smoothest way to the couse sailing , Use of the angles sailed .
thats like saying a race cars engine is everything .. the tires arent important .. water is 800 time desner than air .. 800 times everything vs the sails .. every action (sails) creates an equal & opposite reaction (foils & keels) .. its ALL relative !!!!!!
@@Errol.C-nz Its not as if there's a Hull in the water , These machines are all about windward sailing & sail shape , Angle of attack , Smoove clean wind flow , Lift THAT IS THERE MOTOR .
@@billhanna8838 You are dead wrong. Both are equally important.
Can a foil be switched side? Any insight into how the hydrofoil sections separate from the arms? Always assumed they where ‘one piece’
Cheers for the posts, great to see these boats in detail
For the AC40 boats the foil arms are a single one design piece, it separates about where the black paint begins so below that is the foil section.
if they have to have "tubercules" on both L/E then experimenting with them on only one is questionable. Wouldn't it make more sense to one foil with the straight L/E on both sides (of the leg) and the other foil with "tubercules" ?
could they claim their foils are symmetrical (about the boat CL) ? or is "symmetry" defined in the rule as about the leg CL ?
Symmetry for the foil wing is about the leg centre line
@Mozzy Sails... Would a forward swept foil work?
It would be interesting however there are quite a few risks with it. Read through this for a bit of a brief on some of the pros/cons. en.m.wikipedia.org/wiki/Forward-swept_wing
It'd be nice if someone could measure the bumps, angles, chords, wakes, etc for the foil and figure out what speed and flow direction the are optimized for hydrodynamically. I wonder if the tubercles are more for interference to cancel or reinforce waves and wakes. Also, don’t know if it’s just me, but it looked like they were going with massive flap angles. Maybe they need help keeping flow attached when they crank those flaps to get out of the water fast and early at low speeds.
Newer is its Red Bull in this new era because he made sure he could get the wing that is the floor of the car to be at optimal angles, at as wide a range of car and environment conditions, as possible. He made sure the suspension could lock the floor angle in at whatever the required ride height needed of it. He designed the suspension around RB18/19 to always allow equations for center of pressure, induced drag, overall lift, and center of gravity not to dramatically shift as the car and suspension hit bumps, braked and rolled and change speed. Because of his suspension, the wing that is the car that also keeps the tires at peak performance, this floor wing is itself always predictable and efficient. The steady performance control allows them to show off with a double kicked diffuser to stall it out. In fact, if Red Bull put a small rear wing the diffuser flow would detach and they'd be slower then running a huge rear wing that kept diffuser flow attached.
Newey and Alinghi need a foil that gives full foil control 100% of the time so that they can maximze the sail's maximum potential in all conditions without worrying about the foils. A foil with massive flaps and high speed sweeps means the foils can keep the sail's happy no matter what stage of the race and what the foils encounter. I wonder if the sweep and tubicle are meant to decrease spanwise flow outwards flowing fast pas the tips. Also, the tubicles could help with micro conditions within waves in terms of speed, angle of attack, vertical spped, height and buoyancy changing throught the height and depth of the wave, but the foils are designed to deal with all the waves can throw at them effortlessly and at many speeds and force of lift.
I wouldn't be surprised if the bumps on the foil keep the wake above and behind them as minimal as possible. The half and quarterlength induced waves will maintain a high depth of flow above the wing, and behind and below the wing the air is more laminar and spanwise flow doesn't let much air get suckedmdown, if at all. The foil tip may have no wake at the tip (canceled with interference pattern) and solid, laminar, spanwise flow providing only a small narrow vortex of high speeds and vortices to create suction of air at the foil tip. It needs as much entrenched flow over the wing to keep the fluid speed low over the top wing so pressures are high above these foils with massive flow volumes.
Extra vortices from foil bumps would increase control and guide cavitation problems by maintaining low P vortices to entrain and keep away cavitation gasses.
Mixing air in water could be useful.
I am pretty sure that Alinghi were not a European team that won the cup.
They were a European financier that funded the bulk of Team NZ to defect to a professional travelling circus.
Honestly, I'm still not optimistic about ARBR's chances watching them get up to speed on their boats. Maybe it just shows how much time it takes to come to grips with this form of boat? I guess they do have another year to get ready, and that might be enough, if they do end up launching the fastest boat.
What do the tubercules do?
in motorsports they're used to reduce drag
Look at the last video comments for an explanation. A few aero designers chim in.
As a Humpback Whale - they seem to think they work (From Wikipedia) The tubercles allow the very large whales to execute tight turns underwater and swim efficiently; a task imperative for the humpback whales feeding. The tubercles on the flippers help to maintain lift, preventing stall, and decreasing the drag coefficient during turning maneuvers.
Yes, as the angle of attack increases, if you can induce a little turbulence at the leading edge using the tubercles, this delays breaking the smooth flow over the wing from a fully ventilated stall.
Would be nice making an video about laws for foils.
Why aren't they curving them up at the tips, like all planes are now. It would lessen the drag.
Be buggar if the pressure breaks or wears down the foils appendages
Alinghi didn't win the cup. ETNZ won it sailing under their banner. At least Ellison built a unique team.
Jimmy Spithill, is that you?
I have to read laws again. ...
It ist not forbidden flexible material to use?
Why only alinghi having on foils in and outside different?
And its this against law?
The foil can flex, but only as a result of external forces. The exception is areas of 'flexure' which can flex due to flap movement. But those are limited to a % of foil chord
Hi Mozzy. Great video. I found this link to tubercle foil already being sold on surfboards. In this case, surfers are pumping on the board to get the foils going and the tubercle might help since the angle of attack is oscillating. This is the dual of the wave oscillating. th-cam.com/video/MOrKRZ2z2L0/w-d-xo.html
I was at Lake Garda last week and saw a tubercle foil there. It was being used by a winger though.
Ventilation prevention is the game - all else is secondary. IMHO, these machines are craptastically over-engineered (i.e., they still cling to using the vertical shear on the bows on a flying hull - which causes a nice braking effect when they touch water [at least no pitchpole, like with the silly foiling cats]). And the squiggly lines are amusing. But I do nevertheless love your analyses, Mozzy.
At least the IMOCA 60s and smaller foiling offshore race boats are moving towards blunter, wider bows that allow the boat to 'plane' more easily making it less likely they will dig into the wave and experience a sudden loss of speed. In the future, I see wave-piercing bows to remain on the large foiling trimarans but not the foiling monohulls.
@@jamesaron1967 The IMOCA boats are blue water boats. It would make no sense for them to bury their bows into every oncoming sea - or what they might surf into. As re: trimarans - check out the "superfoiler" pontoon bows - they are (halfway) figuring it out.
@@powerlooper9121 I seriously doubt the Ultims will significantly alter their bows. They're doing fine as they are and the fastest have exceeded 50kts unofficially. The Superfoiler is a weird but interesting design. Not sure I'd call them true tris. Anyway, haven't seen or heard anything from that series in ages...
Regarding the IMOCAS, you and I may think that it doesn't make sense but only recently have the bows began to change. The first gen IMOCA foilers had standard piercing bows and many still do. It's a function of cost as well as superior understanding of all the dynamics involved with foiling boats.
@@jamesaron1967 Just look at the 40 second mark in the vid above. Then tell me that vertical shear bow isn't creating parasitic drag.
@@powerlooper9121 Yes, exactly. Which is probably why ETNZ changed the bow shape for Te Rehutai. Will be interesting to see what the teams come up with for the second generation AC75.
To much thinking bro
Haha. Yeah, spose so. But we all do that don’t we Victor? Especially on this topic.
Never under estimate Alghingi!
They invented a lot, i.e fat head main sails no racer these days is without.
Keora m8t i can design some radical and tem new Zealand will absolutely definitely faster just try it out wat have teams new Zealand got to loose ☆☆☆☆☆