Love this calculation but as many here pointed out, the anhedral foils shift the vertical lift to the outer foil more. My rough math says the difference is 1.1% Scenario: 8 degrees heel of foil arm and 14 degrees additional angle on LR foil (as per sketch). Assuming foil length 2x1,000mm 1) That gives ETNZ 0.99 x [lift per foil arm, for simplicity =1kN] x 2 x 5732 = 11,352 Nm, total lifting force is 1.98 kN 2) LR gets Outer foil: 1.03 x 1 x (5634+510) + Inner foil: 0.927 x (5634-470) = 11,115 Nm total lifting force is 1.96kN Righting force is 2.1% stronger on ETNZ. But hey, then the use the lifting force is less so they could increase the surface (or use flaps) to equalize the lifting force from 1.96 to 1.98. Then we are back to 1.1% difference... Infuses a bit more drag though but at better manouverability and less initial stability allowing Luna Rossa to roll into turns with less force of the rudder. And do not forget that the foil digging into the water allows you to point higher, like a moth leaning into the wind. But ETNZ is a great straight line machine. Reasoning (of a quick calculation of my office desk) The LR foil in near horizontal is about 3% longer than the ETNZ foil, increasing the lifting force by 3% (=1.03) and at 515mm from the centre point. The inner foil will have a 22 degree angle down, with horisontal force at 0.927, but only 463mm from the centre point.
It so heartening to know that there are some really smart people left in this world. If you just watch the news, you'd swear the whole world has just gone stupid.
Not the whole world, just about 70. When the people I lead tell me someone in the office is so stupid, I politely remind them that there is not a single person in the office on the left hand side of the bell curve and that the vast majority are in the top quartile if not higher. It is sobering and a little depressing to know that, because yes compared to those team members of mine a lot of people in the office are stupid and yet they are veritable geniuses compared to the rest of the population. Statistically speaking I am (supposedly) more intelligent than 9,999 of every 10,000 people. If that statistic is true, I find it so sad cos whilst I am fairly intelligent, I'm no freaking einstein.
@@jaysdood those that are hooked by the illusion of power are idiots for they think that It will be theirs forever. Politicians aren't leaders and leaders aren't politicians. Leaders have life skills, politicians have MBAs.
Hi Guys, I just wanted to make a point on the "centre of lift" discussion. When you compare the anhedral foil in LRPP vs the straight one in ETNZ you assume that both the windward and leeward foil halves contribute the same amount of lift. While this is roughly true in the ETNZ straight case, it is certainly not in the LRPP case. The anhedral angle between the half-spans in Prada means that pitch changes to the boat can affect the distribution of lift between the half-spans because it changes the angle of attack of the leeward span more than that of the windward one. Effectively, this means that by changing the pitch of their boat LRPP can put more load on the leeward blade, reducing flap angle to keep the overall lift constant. This gives them a significant righting moment advantage.
I was thinking the same thing, but didnt it look like they made allowances for at least a slight difference in the lift from the two foils on LRPP? The inboard foil is always operating at a worse angle for creating lift that the outboard one, but better for creating windward lift though. Perhaps LRPP can rely much more on just their outboard foil than ETNZ can, in part due to their bigger foil area, should equalize things a bit if LRPP can move their center of effort further outboard. But, I dont think they can unload the inboard foil completely, they would have almost nothing stopping them from going sideways then, and that part of the foil would just be creating drag, so I cant imagine that they would be able to move the CoE further outboard than ETNZ?
That's was my first thought too. Also, they are talking about pure speed, but the important thing is VMG and having a wing with a more vertical angle in the water could give LR the ability to sail more close to the wind. So I'm confident we will see a much closer race than predicted.
Initially I agreed with you but after more thought I think it's more nuanced. Yes, the centre of the vertical component of the lift will be further out on LRPP because the outboard half is providing proportionally more vertical lift. However I don't think that is where the boat will pivot around. I think the boat will pivot around the centre of all lift which will be on the foil centreline where Mozzy has put it. Might be wrong but that's my current thinking
@@Robinlarsson83 I guess the key for Prada´s set up is to optimise the pitch so that the benefit of moving the centre of lift to leeward outweights the inefficiency created by having a "less effective" windward wing dragging on the water. However since the foils have to be symmetric, the parasitic drag of the windward half of the foil is not something that changes. Essentially having the anhedral foils gives Prada a new degree of freedom (distribution of the centre of lift) that ETNZ don´t have (although they recover with having the lower canting angle discussed in the second part of the video). The problem, at least in my mind, is that ETNZ´s set-up forces them to have a significant part of their foil very close to the surface, which can make it unstable in "rough" seas I think. Regardless, I love how these new rules have created so many subtleties and areas for optimisation.
thank you all for your team effort over the last few months. It really is fascinating to discover and understand the engineering parameters. Great stuff!
Mozzy, your series is fantastic. I am a sailor and cyclist and been there to watch both Bus Mosbacher and Eddy Merckx will in the day, as well as to participate through my life. My fave though is DN racing and maximizing, speed on ice. The AC75s seem like a similar thrill, and the yacht design analysis is very enlightening. These are basically sailboats without keels, with the keel being replaced by the foils. It puts a whole new light on the potential trickiness of traditional keel design. Remember the 1987 keel foil that was installed backwards? Thanks so much for your work spreading this informaiton.
excellent intellectual and enginneering discussion as all ways......typical of the bright young engineers that will drive the whole concept once TNZ wins and Ineos becomes the Challenger of Record....
As a fluid dynamics expert, (I can swim a bit!), I appreciate just how complex your specialities are, and that you are seeking to educate and inform numpties like me. Accordingly I would like to concur with an earlier reply that you manage to find time to prepare your 'script' , not that its written out, but that with all the subtleties and complexities involved it takes time to marshal the issues involved to properly present the message, not that you don't know the answers. I was deep in major commercial IT projects in the late '60s where 99.99% of the user community couldn't spell computer and the level of communication we had was appalling, until the penny dropped. Thanks for an outstanding channel series.
All very interesting, and another variable is in the equation. LRPP drives the two flaps for the foil differentially, not as one. That allows to move the center of lift even further, in theory
I think there is so much underestimation of LRPP. Those @mozzysails videos are great food for thought but they seem so biased. Constantly ETNZ this advantage ETNZ that advantage, while on the water its the ETNZ the one that is trying to desperately find an edge, even experimenting with code zero and double helm. To me it feels like ETNZ is the only one that knows that italians will be really tough opponent.
Great engineering expose’... well explained and projected information to be superficially but commonsensically understood by Mr and Mrs Average with family in tow.. appreciated and always look forward to seeing the next infovid...🥰😎
Thank you. This is exactly what I was wondering about. Now I'm more convinced that there is more to discover. But you can lower or lift the the wing. So you have more effects combined to others
I think more cant = more lee resistance = more vmg. And, tip out ventilates the entire side, this is evident from many overhead shots of both boats, and perhaps from the pitting on etnz outboard hinge. This will move CE in, but reduce drag further and increase lee resistance. Great series thx
The gift that just keeps in giving. The calculations / analysis and explanations were very well done and clearly articulated. First rate and definitely some learning for me ! Even if you discount the real world advantage from the theoretical as things in life never quite add up as expected it tells me in a straight line NZ will be quicker. How much will LR catch up using latest mods in the shed is the big question. And lighter airs these differences don’t work as well... which with LR being so strong in the lighter airs might make things more even depending on weather...
When u guys decompose the lift, shouldn’t it be perpendicular to the foils? Especially regarding the anhedral foils one side of the foil wings contributes a lot to prevent leeway as far as i see it?
Love the discussion. One of things that strikes me about the tip out of the water approach, is how it harkens back to the 2013 V shaped foils that didn't have trailing edge articulation, so they depended on coming out of the water to decrease the amount of lift. If you invert your previous discussions about how important tip winglets are in controlling lift loss around the tip in light air, it gives you a sense of how important the tips out could be in heavy air. My understanding is that foils sections that pierce the water loose up to 50% of their effectiveness. If you consider the T shape foils of Emirates as 2 foils, in theory you could have as much as 25% less lift when the tip is fully exposed. As American magic clearly demonstrated, the issue at high speeds isn't too little lift it is too much lift and the inability to rapidly decrease the amount of lift. By having a tip out approach, the amount of lift is self limiting, as as soon as the tip is lifted out of the water the amount of lift drops rapidly without intervention. The other component of tips out is that, by allowing air in from the the tips, the amount of drag on the foils is theoretically decreased. I would love to see a work up on those numbers as it is well beyond my modeling ability. However at high speeds, as you have pointed out before foil drag becomes the speed limiting factor, not the amount of lift.
Great analysis guys. However as a few lads have commented here, the anhedral form of Luna Rossa's foils allows them to carry the center of lift towards the outer span of the foil. Thus negating the alleged advantage of the increased righting moment of the straight foil of ETNZ. However, that comes at a price, and that is Luna Rossa cannot stick their foil out of the water as much as ETNZ. And here is the trade off. At high speeds, ETNZ can stick their foil out of the water reducing wetted surface. At slower speeds, with foils fully submerged to provide enough lift, Luna Rossa has more righting moment thanks to the anhedral shape. And if they can control the flaps of the two spans independently, they can potentially have a very powerful high mode sailing upwind by adjusting the flap of the inner span of the foil.
It explains a lot of what we've been seeing from the sail spotter videos. Specifically, points raised by viewers concerning apparent instability and the crazy speeds. ETNZ are riding on a _knife's edge_ - literally. There's so little foil in the water; their foils have less area to begin with coupled with the canting angle employed which lifts more of the foil into the air. This is truly a fine balancing act and will no doubt result in higher speeds, all else being equal. Hopefully, they have mastered control of the tricky dynamics involved. Amazing insights and analysis.
It also explains a lot of what we're hearing out of LRPP. Jimmy is talking up their maneuvering ability and how hard it is to overtake on these narrow courses. I suspect that they know that they're slower and are pinning their hopes on getting a jump on ETNZ in the start box and then controlling the race from there. If that's true then we'll see some intense match racing if LRPP start in front at any point but a parade if they start even or ETNZ starts ahead.
@@franzfanz It's certainly sizing up to be a spectacular set of races. Two teams with very different boats applying wildly different strategies and philosophies. May the best team win!
I LOVE these videos. So much fun getting to geek out with you guys on these engineering nuances. That being said, I sure hope the racing is closer than the VPPs are telling us. Thanks for making such great videos!
Amazing analysis guys. Shocking conclusion too really. On the face of it, this looks like the AC final is going to be a fore gone conclusion. It’s almost as if NZ designed the boat they wanted, then wrote the rules around their boat design in such a way to disguise their solution as much as possible from their competitors, & driving them down different, sub optimal, design routes.
Thank you guys for this extremely interesting video... most probably more than 50% of the performance of AC75 is coming from foils, rudder included. The team who got it right will win. BTW forza Luna Rossa 🇮🇹
I also think that ENTZ canting the leeward foil also helps drive to windward like a kitesurfer instead of just relying on the vertical part of the arm in water.
Thank you, gentlemen - interesting, informed and erudite as always. Sky Sports should consider bringing this team into commentary for debunking / demystifying some F1 rules & interpretations... :-)
I think the TVNZ commentary team are watching Mozzy. During the Prada cup final, their technical commentary focus was virtually a borrowed script from Mozzy's previous day's episodes.
Very interesting mozzy but, being an aerodynamic engeneer I wonder why in your consideration you did not consider that the lift schould be considered perpendicular to the surface of the foil. This changes the moment considerations quite a bit. Just curios to know what you think! Thanks
We did, but just drew the vertical component. Thought that would make it clear how the anhedral shifts lift slightly outboard of the bulb. In retrospect should have shown X component and the resultant (perpendicular to foil surface). Basically they are there, just not shown.
And here’s me thinking flying the tip above the surface was for reduction of drag. But once explained, flying it along with the t shape to max out the CoL is a simple solution. It’s like they started with the sum then figured out the parts in a basic manner, quite kiwi in thinking. If this, what seems basic, solution proves to be a large part of the winning (RM)formula why did the other teams not travel this path? Maybe the execution was too complex relative to risk. Thanks Mozzy Sails and Rob and Tom for your clever analysis and it’s clear presentation. Hope some Allen jerseys are in the post.
Your analysis is excellent as a team of 3. It’s impartial and balanced. Keep it up.... we’re in Auckland and planned to take the kids to watch at the viaduct today but have to watch online next Wednesday, as we’re still at level 2 lockdown. If all goes to plan hopefully you three can visit Auckland for AC 2025?!!
Fantastic. Question: is there a trade off between more righting moment and more leeward drift, in the case of TNZ tips-out foil? Might LR be able to head upwind more acutely, gaining on VMG even if sailing with lower boat speed?
An extra two and a half knots boat speed will bring the apparent wind forward, so I would expect Luna Rossa to point higher than Te Rehutai. Likewise LR might be able to point deeper, downwind. As to the extra horizontal component of the inboard wing on LR, giving her a shove to windward, yep it should be accounted for before we start assuming TR is way faster. However, if those speeds prove accurate, that’s a hell of a lot to overcome. Buono Fortuna, a Luna Rossa. Kia Kaha, Peter and the boys, Go Te Rehutai!!
@@q.e.d.9112 Providing there will be ideal conditions, it will be much harder to overcome than even that if the speed rumors are true. Several sources claim much higher than 2.5 kts faster. If indeed valid, LR's alleged superior VMG vanishes.
What i find interesting from watching these excellent videos and reading the comments is how far the Americas Cup has moved into the domain of highly complex aeronautical engineering and away from naval architecture... i wonder what the likes of Sir Thomas Lipton and others would have made of all this !
Thanks for the contribution. I agree with the great point of this video but I cannot “grasp” the transition between best righting moment and higher speed, unless it is assumed that the boat with the best righting moment is the one that can therefore allow larger sails. Maybe you refer to the less wet surface?
You're looking at center of rotation as a straight line down the center of the hull. If you look at this in 3D you have a triangle defined by the center line, and a line between the rudder foil and the leeward foil. So perhaps this means that the heeling axis is defined by a line between the rudder and the leeward foil. So as the boat heels to leeward, it'll pitch a little nose up and thus the angle of attack if the foil increases slightly.
Thanks for the in-depth analysis. We see the theoretical difference in 17 knots - how about at 10 knots? 12 knots? etc? is it increased or decreased at lower wind speeds?
Another great video guys. So I'm pretty familiar with the VPP pgm and my head hurts trying to think about modeling these boats, good on ya boys... Great discussion. I think ETNZ is built for speed, the low wetted surface at speed... low drag, just my $.02. I love your opening... 'It's the internet, so what you want...'😂
Definitely. The issue then is whether they can get it up and keep it up in light winds. The furlable code zero will help with that. I'd assume they all have one -- it was a big thing back in monohull AC days -- but ETNZ seem to be seriously practicing with theirs.
@@BruceHoult There were some comments in other videos that they opted not to use the code zero in the races. Probably didn't help to lift the boat onto its foils but can't verify that.
Great video, very complex variables. I'm beginning to see that in higher wind slapping the hull into a few waves and a minor touchdown or two is a price worth paying for a few degrees less of foil arm cant and a more vertical foil.
The hull occasionally skimming the surface doesn't appear to shave much speed if at all, judging the distance from the chase boats staying the same when that happens. Besides, ETNZ like to fly close to the water for aerodynamic purposes and it must be an acceptable minor tradeoff to them from all appearances.
. . . .not forgetting the reduction in leeway angle by having the lifting surfaces acting as a centreboard when going to windward. Also having hull lower makes it more of a ground effect flyer.
The total force may be orthogonal, but I think they are only considering the vertical component of the triangle of forces as being relevant to righting moment. The horizontal component is relevant to leeway, which is not being discussed.
Hi Mozzy Men, Things also to consider when making your prediction's for the upcoming races are that it seams Autumn is coming sooner as we have just had rain which has cooled the land and the winds could be closer to 16 knots than the average of 13 Knots for March.
I live and sail in NZ , the cliffs overlooking course E are just down the road. Today both boats.were practicing in 10 to 12 knots and foiling fast . We are in autumn now when normally there are more windless days than usual That said its been a hot summer with a lot of warm Easterlies and strong afternoon sea breezes so the usual weather patterns may not apply .
Initial races will be on courses A and E. due to COVID level two restrictions. Have the impression, from previous race course selections by race managers, that these are the least challenging from "emphasis on tactics and boat handling" perspective. Swirly, strong SW on course B has been my favourite so far. Wonder if the old adage of "pick horses for courses" will come into play?
With the anhedral foil, the windward wing can also be set to provide windward lift... ie: added pinch to windward. I wonder if this is part of how LLPP was able to so easily squeeze out Sir Ben. This also could similarly be applied to ETNZ when they lift the arm that 3°. Also, breaking the surface with the foil produces extra drag, it doesn't just reduce wetted area. So complex!!! Really appreciate your thoughts and discussions! Thank you
Great commentary and analysis. I would like to hear comments about effect of anahedral on RM, In regard that LRPPs anahedral is unfaworable configuration dynamicaly. To elaborate on this, Lets asume equilibrion condition; foil arm strut going through water at 0 deg AOA, both foils (equaly loaded, thus force projecting through bulb and strut), HM and RM moments ate in perfact balance in this point in time (and so are Y forces). Now gust hits, sails start to produce more Y force, boat start to sail with more leeway. Now this bigger leeway is changing lift distribution on anhedral foil in such way that it loads more inboard foil. Obviously this is reducing RM, so trimer is easing traveler more than he would in case of straight foil.? One more thing, By canting more foil arm TNZ is lowering their boat, but also reducing arm between sail force and foil Y force, thus reducing Heeling moment. Cup is loosing apeal quickly :( 7:0 for TNZ?
hi guys, interesting analysis, but Tom did not take into consideration the great advantage of the huge angle that the internal semi-foil of the "lunarossa" Y creates when the pierced navigator, almost 45 °, capable of developing a greater upwind angle ... it will be a great challenge, but the double helmsman could be the big advantage ... !! Hello and congratulations !!
Thanks - well explained Mozzy. How did yachting get into such a pickle with its mixed units? Fortunately we didn't put any values on pressure or righting moment so only heard metres, millimetres, tonnes while forced to mention weight and knots? (0.54kn =1km/hr)
Forces are calculated in Newtons, moments in Newton/metres. However I often use a conversion to "tonnes-force" as I find it easier to relate when we talk about a boat (+ crew etc) that weighs 7.8 tonnes. 😎
@@maxhugenFirstly a correction moment unites ar Newton-metres. And the total pressure force is 7 8×9.80665=76.5kN assuming their vertical velocity and acceleration are zero and there is no contributing vertical component from rudder/elevator. This discussion is more about the differences in righting moment arm lengths and ignoring other directional dynamic and balancing components so is greatly simplified.🥝🥝🙏
What I take from this is that one of these boats can be seen in an analogy to a trapezing dinghy (say a Contender, where the skipper and crew are one and the same), where the leeward foil is essentially the hull of the dinghy in the water; the actual hull of the boat is analogous to the body of a trapezing crew; and the windward foil, lifted from the water, is actually analogous to that crew's arms lifted over their head for greater leverage. In this analogy also it makes sense that these boats should sail with their hulls as close to the water as possible without letting them touch, much as a dinghy crew would lower themselves on the trapeze wire. That would maximize the outboard distance of the hull relative to the leeward foil, in the same way as a dinghy crew might go on tiptoe while trapezing.
@@TheUltimateWriterNZ I bet all three are going to be up in their pyjamas and sponsors jumpers too, maybe at 4am GMT! Certainly it would be great to beef up the commentary though.
I doubt that NZ has a 7.5% speed advantage, but we shall see. However, if LR can sail closer to the wind at their optimal VMG than NZ, this will at least partially negate any speed advantage NZ have. Also, in light air, LR can probably turn faster through the tacks.
Idk, I keep thinking that the fact the foil lift is perpendicular to the foil is a factor in parts of the discussion. Paticularly regarding the out board foil for the anhedral foil which horizontal vs pitched significantly on the inboard foil.
Been wondering if down force could be created by the IB foil and lift by the OB foi to create righting moment by torquing on the foil arm? And can any positive effect be created by the windward foil flying thru the air or is it matter of air drag reduction?
When ETNZ's tip pierces the surface it creates a smaller lifting surface. ( particularly on the out side half of the foil) Wouldn't that shift the righting moment further inboard on the foil as a whole? Foil length divided by two equals center of effort of foil?
Thanks for the vids guys , great work. Other factors to take into consideration are manoeuvrability and how the hull "cuts" through the air , how low relative to the surface of the water they fly ....need to put it all together to have a more complete picture , but all your videos have been very formative . Last but not least , the high mode that LR showed ...can ETNZ match or beat that ? Fascinating .
Please correct me. Wouldn't the foil lift be roughly in the center of effort of the sails rather than vertical? If that is the case, then excess lift could be used to crab the boat to windward increasing VMG and contribute to even more of an advantage. Great job guys!
What about the drag due to the profile of the foils. I would assume, that etnz needs another profile than LR as their surface area of the foil is smaller. The boats have the same weight so etnz needs higher lift per area on their foils. Is that possible without inceasing the drag of the foil? In the end it could be faster using a profile with higher lift to surface ratio as you gain drag due to little wetted surface area bit the fact you need another profile could lead to smaller gains of etnz as you predicted in your very interesting and detailed video. Love your argumentation and discussions. Well done
Great catch about the center of lift !!! Just, following your idea, the center of lift is pushed a bit on the external side because the vertical component of the external (more horizontal) wing should be bigger than the vert. comp. Of the internal wing due to the different angle.
Do you think moving the foil tip out of the water is also cutting hydrodynamic drag, as at high speed even the small foil is probably producing the lifting force with very low and therefore inefficient angles of attack? (Below the maximum Lift/Drag ratio AoA)
Just want to mention another point - moving the center of lift up or down changes the vertical distance from the CE of the sail plan to the CL so it has an effect on the heeling moment.
First - Love your work. Great analysis but can I suggest a coupe of other considerations? A foil piercing the surface has greater drag than one fully submerged. Also a smaller surface area foil with otherwise equal parameters equates to a more highly loaded foil and again greater drag. As you so beautifully put it - it's complicated.
Not related to this video but I haven't seen anybody analyze how Luna Rosa was able to gain ground in headwind without necessarily going faster. I'm not a sailing expert, but I think this is what is highlighted with polar plot. I haven't heard anybody talk about it. I'd love to hear your take on it.
A more important measure is VMG - Velocity Made Good (how fast you are moving towards the next mark). This is calculated from both boat speed and the angle they are sailing at. As an extreme example, if you are sailing at awesome speed, but at 90° to the course, you're not getting any closer to your next mark. In real terms, LR was able to sail closer to the wind than GB during the Challenger Finals, so made better VMG and won.
With the anhedral foil, the inboard half needs to have a vector diagram of the lift as only a percentage of the lift will be vertical. With less vertical lift inboard the center of the total lift of the foil will move outboard but the total lift will be less in kg. Do these changes cancel out?
hey, could you comment on longitudinal position of the foils. LRPP has foils in front of the arm, and ETNZ pushed max backwards. I am guessing this makes point of lift for etnz about 1m back. Would be nice what you guys think about that difference. keep up great work!
Fore and aft relative to centre of gravity changes pitch balance and stability. But that can also be changed with foil arm position as well as wing attachment to arm. I think the attachment to arm is about separating peak pressure but also about foil 'flutter'. There's a video from a few weeks ago we did touching on this.
I am not an aeronautical engineer, but I am a pilot. What I can say is that getting a tip out of the water is a little bit like having a wingtip collapse in a paraglider. It just doesn't matter. The reduction in surface area of the wing results in higher wing loading, which raises the pressure inside the wing, and under the wing, and resists further collapse. In the case of a boat, extending a tip from the water will not only increase wing/foil loading, but also reduce drag. I think that's right. So, the more the tip extends into the air, the more downward force is exerted on the remaining subsurface wing area, pushing it back down. We know that G=L/D - so a foil tip protruding from the water should automatically increase the glide ratio through the water. The higher glide ratio is compensated for by the increased wing foil loading, which should maintain a steady horizontal ride height. Or at least that is my understanding - which could be worth exactly what you paid for it. :P
Sorry mate not completly right on that, breaking or even disturbing a surface creates added drag, wheather this is beneficial or not considering that some viscous resistance is gone is to be calculated. but one of the main advantages of moving on foils is that the residual resistance is almost gone (in naval arch. the residual resistance is the one not generated by viscous effects) except for the small sections in wich you break the water
do you have an idea of why the foil tips on Luna Rossa are angled up and constantly piercing the water? Could they be angled down as on moth foils or it will not have the same effect on the anhedral?
Hi guys thanks for the video. I’m not a foils expert but shouldn’t you apply the force vector perpendicular to the foil (cord). If so, when you do the vector analysis you get 2 components: one perpendicular to the water surface (lift) and the other perpendicular to the rudder. This is important, I think, because with the T foils you can’t separate the two effects while with a Y foils you can set them to be different in case you need. Thanks
Very interesting video. However, it appears to me that there is an underlying assumption that the pressure distribution on the leeward foil is symmetrical with respect to the foil strut, similar to the pressure distribution for an aeroplane. However, for those teams with 2 flap controls, that may not be necessarily true? In fact, they could tweak the span-wise circulation distribution so that the resulting centre of effort is more towards leeward than the corresponding symmetrical distribution obtainable with a single flap actuator. Any thoughts?
As ETNZ lifts its foil up so that the tip is out of the water, what about the change in the share of vertical and horizontal components of lift? The doesn't the vertical component decrease and the horizontal increase? How does that change effect the righting moment? Also, not that it effects the comparison of the two boats (probably), isn't the righting moment based on 6.5 tonnes, as about 1 tonne is at the end of the foil arm in the water?
The foil with the tip out of the water has less form drag which will negate the loss of lift. I calculate that the less drag actually favours the lack of lift by a fraction, however the better righting moment is further enhanced giving it two wins for one loss. What I don’t fully understand is how much loss one gets with the foil being closer to the surface with higher percentage of oxygenated water and the higher risk of cavitation. It could mean that team NZ have a lower all out maximum speed than the Italians?
Has anyone looked into / discussed the possibility or option of using the two flaps independently to “torque” the lift effect about the axis to induce righting moment via the pressure differential? Obviously etnz with the “linked” foil control couldn’t but it would be interesting to know if any teams played with the idea
Great videos thx and agree etnz will have a speed edge. I think there is also more that we cannot see. Etnz learnt their lesson in San Fran, we will not see their true performance, only what they need to win.
I also think a key factor will be the VMG, at the last America’s cup TNZ always traveled significantly less distance. They didn’t look that much faster but the vmg was significantly better
@@nickleach3570 The boats are radically different from the last AC, though. Everyone seems to be claiming LR has better VMG this time around. I guess we'll see come race day.
The additional canting is done for cavitation issue not for righting moment I think....Vittorio d'albertas should have a video coming up with some CFD guesses results Having looked at the anhedral the key is down to splitting lift force and side force. LRPP I believe can control each foil separately. That's when you see the high mode. Using the outermost flap for more lift and the inboard one to go for sideforce. Your analysis is good but when you factor the above in I think and hope we have a close race
I am convinced in my own mind the hull delivers a small percentage of ground effect lift, more noticeable always on the side where the foil arm is down, using the shape around the "hinge" in a constructive manner to trap air and that sailing with the bow down sometimes touching is part of the equation to give stability and slippiness when one considers the need for the rudder pitch to be as neutral as possible. The flatter surfaced skeg (not as radical as Ineos) I observe as "smacking" the water at over 30 kts which results in any touches acting like those of a skimming stone so it never gets depth and drag and finally, the useful videos put out such as Justin mitchell and sailchaser and airflownz show the latest practice runs of ETNZ having the windward side of the boat "leaning into" the wind on speedy turns! The Total package of a low flying machine.
@@petertelford5338 I didn't know this, thank you for pointing it out. In my mind this doesn't make any sense, however I get the feeling that the mechanics are much too complicated here for understanding without details.
@@pp2793 Definitely so. We as laymen get the overall idea of what is going on. These videos are incredibly helpful as are the two Italian blokes who draw down from top experts in Italy. They did some good work on foil shapes, profiles, and hull "stickiness" to the water. Like most things in life, it comes down in the end to what happens in reality. That is where the human element comes in. LR with machine like team can pull off some great results. All we want now is some great drama on the water which makes us all feel proud as humans at the ingenuity and effort. Roll on Wednesday! By the way, the weather for Wednesday and Friday is in LR's favour in my view 11 to 18 and 11 to 20 MILES PER HOUR. So 9 to 15 and 9 to 17 knots. on one of the days, the wind is fading away during the day. ETNZ should tread with care not to go 4-0 down!
ETNZ AI is its big advancement has been to test sailing modes in all conditions, with design changes, refined in simulation, before committing to hardware.
The half of the delta shaped anhedral foils will not have its CoP at the laf way point along its span, it will be closer to the bulb and therefore higher and closer to the centre line of the boat i.e . to the keel
NZL worked out a long time ago the aerodynamics should not be lifting the hull but forcing it down. You can see the modification on the Luna Rossa boat was a game changer. But how you can change direction and speed of change under sail load and in close proximity is probably the important race winning formula.
Firstly, love your video’s. Could Tom do the same math with Ineos. It would be great to know if they had no chance mathematically from the word go against Pravda and it would also be great to compare the mathematical assumptions with actual data to get a feel for how accurate the percentage difference is and apply that to team NZ. Cheers
If you'd like to have more righting moment, you could have the hull provide less aerodynamic lift. (or increased down force) The foil has to provide more lift to compensate. I don't know if this is a net gain or not...
If we take righting moment as pointing up (as your diagrams seem to do) then the center of lift (as regards righting moment) is outboard of the foil arm because of the anhedral. The outboard wing lifts. The inboard wing prevents leeway. But then the center of righting moment is well outboard of the foil arm giving LR more righting moment....no?
One other thought. Speed isn't what gets you to the windward mark. It's VMG. Does LR not have more leeway-resistance too, because of the anhedral? And whether they're faster in a straight line or not, are likely to be able to sail higher (and lower) angles?
Sorry if I missed it but have you guys considered the horizontal lift component of the ‘T’ foil adding to the righting moment? I’d need to do some maths to see if this is greater of less than with an anhedral foil. It strikes me that clearly NZ are not needing lift but it’s becoming clear it’s all about the righting moment! - I’ll leave the maths to you boys!
![กิโลเมตรที่ 0 เดินทางรอบโลกไม่ใช้เครื่องบิน [Around The World Ep. 1]](http://i.ytimg.com/vi/toJG9oofLFY/mqdefault.jpg)
Love this calculation but as many here pointed out, the anhedral foils shift the vertical lift to the outer foil more. My rough math says the difference is 1.1%
Scenario: 8 degrees heel of foil arm and 14 degrees additional angle on LR foil (as per sketch). Assuming foil length 2x1,000mm
1) That gives ETNZ 0.99 x [lift per foil arm, for simplicity =1kN] x 2 x 5732 = 11,352 Nm,
total lifting force is 1.98 kN
2) LR gets Outer foil: 1.03 x 1 x (5634+510) + Inner foil: 0.927 x (5634-470) = 11,115 Nm
total lifting force is 1.96kN
Righting force is 2.1% stronger on ETNZ. But hey, then the use the lifting force is less so they could increase the surface (or use flaps) to equalize the lifting force from 1.96 to 1.98. Then we are back to 1.1% difference...
Infuses a bit more drag though but at better manouverability and less initial stability allowing Luna Rossa to roll into turns with less force of the rudder. And do not forget that the foil digging into the water allows you to point higher, like a moth leaning into the wind. But ETNZ is a great straight line machine.
Reasoning (of a quick calculation of my office desk)
The LR foil in near horizontal is about 3% longer than the ETNZ foil, increasing the lifting force by 3% (=1.03) and at 515mm from the centre point. The inner foil will have a 22 degree angle down, with horisontal force at 0.927, but only 463mm from the centre point.
It so heartening to know that there are some really smart people left in this world.
If you just watch the news, you'd swear the whole world has just gone stupid.
To obtain power, one must brainwash a large number of stupid people. This involves speaking to them in their native language.
A lot of intelligent people are stupid.
All the politicians certainly have gone stupid, if they weren't already born that way...
Not the whole world, just about 70. When the people I lead tell me someone in the office is so stupid, I politely remind them that there is not a single person in the office on the left hand side of the bell curve and that the vast majority are in the top quartile if not higher. It is sobering and a little depressing to know that, because yes compared to those team members of mine a lot of people in the office are stupid and yet they are veritable geniuses compared to the rest of the population. Statistically speaking I am (supposedly) more intelligent than 9,999 of every 10,000 people. If that statistic is true, I find it so sad cos whilst I am fairly intelligent, I'm no freaking einstein.
@@jaysdood those that are hooked by the illusion of power are idiots for they think that It will be theirs forever. Politicians aren't leaders and leaders aren't politicians. Leaders have life skills, politicians have MBAs.
Hi Guys, I just wanted to make a point on the "centre of lift" discussion. When you compare the anhedral foil in LRPP vs the straight one in ETNZ you assume that both the windward and leeward foil halves contribute the same amount of lift. While this is roughly true in the ETNZ straight case, it is certainly not in the LRPP case. The anhedral angle between the half-spans in Prada means that pitch changes to the boat can affect the distribution of lift between the half-spans because it changes the angle of attack of the leeward span more than that of the windward one. Effectively, this means that by changing the pitch of their boat LRPP can put more load on the leeward blade, reducing flap angle to keep the overall lift constant. This gives them a significant righting moment advantage.
I was thinking the same thing, but didnt it look like they made allowances for at least a slight difference in the lift from the two foils on LRPP? The inboard foil is always operating at a worse angle for creating lift that the outboard one, but better for creating windward lift though. Perhaps LRPP can rely much more on just their outboard foil than ETNZ can, in part due to their bigger foil area, should equalize things a bit if LRPP can move their center of effort further outboard.
But, I dont think they can unload the inboard foil completely, they would have almost nothing stopping them from going sideways then, and that part of the foil would just be creating drag, so I cant imagine that they would be able to move the CoE further outboard than ETNZ?
That's was my first thought too. Also, they are talking about pure speed, but the important thing is VMG and having a wing with a more vertical angle in the water could give LR the ability to sail more close to the wind. So I'm confident we will see a much closer race than predicted.
@@strozzascotte 100%
Initially I agreed with you but after more thought I think it's more nuanced. Yes, the centre of the vertical component of the lift will be further out on LRPP because the outboard half is providing proportionally more vertical lift. However I don't think that is where the boat will pivot around. I think the boat will pivot around the centre of all lift which will be on the foil centreline where Mozzy has put it. Might be wrong but that's my current thinking
@@Robinlarsson83 I guess the key for Prada´s set up is to optimise the pitch so that the benefit of moving the centre of lift to leeward outweights the inefficiency created by having a "less effective" windward wing dragging on the water. However since the foils have to be symmetric, the parasitic drag of the windward half of the foil is not something that changes. Essentially having the anhedral foils gives Prada a new degree of freedom (distribution of the centre of lift) that ETNZ don´t have (although they recover with having the lower canting angle discussed in the second part of the video). The problem, at least in my mind, is that ETNZ´s set-up forces them to have a significant part of their foil very close to the surface, which can make it unstable in "rough" seas I think. Regardless, I love how these new rules have created so many subtleties and areas for optimisation.
You are all awesome nerds! thank you
thank you all for your team effort over the last few months. It really is fascinating to discover and understand the engineering parameters. Great stuff!
Mozzy, your series is fantastic. I am a sailor and cyclist and been there to watch both Bus Mosbacher and Eddy Merckx will in the day, as well as to participate through my life. My fave though is DN racing and maximizing, speed on ice. The AC75s seem like a similar thrill, and the yacht design analysis is very enlightening. These are basically sailboats without keels, with the keel being replaced by the foils. It puts a whole new light on the potential trickiness of traditional keel design. Remember the 1987 keel foil that was installed backwards? Thanks so much for your work spreading this informaiton.
excellent intellectual and enginneering discussion as all ways......typical of the bright young engineers that will drive the whole concept once TNZ wins and Ineos becomes the Challenger of Record....
You need these guys and more like them on the next iteration of the INEOS technical team. Youthful talent is the future for a winning AC team.
Nah. It’s all about Ben.🙂
As a fluid dynamics expert, (I can swim a bit!), I appreciate just how complex your specialities are, and that you are seeking to educate and inform numpties like me.
Accordingly I would like to concur with an earlier reply that you manage to find time to prepare your 'script' , not that its written out, but that with all the subtleties and complexities involved it takes time to marshal the issues involved to properly present the message, not that you don't know the answers.
I was deep in major commercial IT projects in the late '60s where 99.99% of the user community couldn't spell computer and the level of communication we had was appalling, until the penny dropped.
Thanks for an outstanding channel series.
All very interesting, and another variable is in the equation. LRPP drives the two flaps for the foil differentially, not as one.
That allows to move the center of lift even further, in theory
Not only in theory, but practically !
I think there is so much underestimation of LRPP. Those @mozzysails videos are great food for thought but they seem so biased. Constantly ETNZ this advantage ETNZ that advantage, while on the water its the ETNZ the one that is trying to desperately find an edge, even experimenting with code zero and double helm. To me it feels like ETNZ is the only one that knows that italians will be really tough opponent.
@@DryAx3 Maybe that's what it looks like to some observers, but since when is experimentation considered desperation??
Great engineering expose’... well explained and projected information to be superficially but commonsensically understood by Mr and Mrs Average with family in tow.. appreciated and always look forward to seeing the next infovid...🥰😎
Thank you. This is exactly what I was wondering about. Now I'm more convinced that there is more to discover. But you can lower or lift the the wing. So you have more effects combined to others
U guys are just awesome!
seconded, awesome, agree with the guys above, u should be on Sky
I think more cant = more lee resistance = more vmg.
And, tip out ventilates the entire side, this is evident from many overhead shots of both boats, and perhaps from the pitting on etnz outboard hinge. This will move CE in, but reduce drag further and increase lee resistance.
Great series thx
Well done guys and thank you for another excellent report and discussion.
The gift that just keeps in giving. The calculations / analysis and explanations were very well done and clearly articulated. First rate and definitely some learning for me ! Even if you discount the real world advantage from the theoretical as things in life never quite add up as expected it tells me in a straight line NZ will be quicker. How much will LR catch up using latest mods in the shed is the big question. And lighter airs these differences don’t work as well... which with LR being so strong in the lighter airs might make things more even depending on weather...
Fantastic guys. Thanks a million. Super interested to see it in reality now!
When u guys decompose the lift, shouldn’t it be perpendicular to the foils? Especially regarding the anhedral foils one side of the foil wings contributes a lot to prevent leeway as far as i see it?
Love the discussion. One of things that strikes me about the tip out of the water approach, is how it harkens back to the 2013 V shaped foils that didn't have trailing edge articulation, so they depended on coming out of the water to decrease the amount of lift.
If you invert your previous discussions about how important tip winglets are in controlling lift loss around the tip in light air, it gives you a sense of how important the tips out could be in heavy air. My understanding is that foils sections that pierce the water loose up to 50% of their effectiveness. If you consider the T shape foils of Emirates as 2 foils, in theory you could have as much as 25% less lift when the tip is fully exposed. As American magic clearly demonstrated, the issue at high speeds isn't too little lift it is too much lift and the inability to rapidly decrease the amount of lift. By having a tip out approach, the amount of lift is self limiting, as as soon as the tip is lifted out of the water the amount of lift drops rapidly without intervention.
The other component of tips out is that, by allowing air in from the the tips, the amount of drag on the foils is theoretically decreased. I would love to see a work up on those numbers as it is well beyond my modeling ability. However at high speeds, as you have pointed out before foil drag becomes the speed limiting factor, not the amount of lift.
These videos are fantastic! I'm so excited for the racing!!!
Great analysis guys. However as a few lads have commented here, the anhedral form of Luna Rossa's foils allows them to carry the center of lift towards the outer span of the foil. Thus negating the alleged advantage of the increased righting moment of the straight foil of ETNZ.
However, that comes at a price, and that is Luna Rossa cannot stick their foil out of the water as much as ETNZ.
And here is the trade off. At high speeds, ETNZ can stick their foil out of the water reducing wetted surface. At slower speeds, with foils fully submerged to provide enough lift, Luna Rossa has more righting moment thanks to the anhedral shape.
And if they can control the flaps of the two spans independently, they can potentially have a very powerful high mode sailing upwind by adjusting the flap of the inner span of the foil.
Thanks again guys awesome insights I can't wait to see the upwind speeds compare after the first race .
Thankfully, the lads haven't uncovered our true secret weapon in sock selection.
Let's go, Team NZ!
That's a easy one they are Red
LOL Socks !!!
@@isaacmtamou8070 Yeah but the Prada socks are 300 Euros a pair!
@@Toob41 I was referring to Sir Peter Blake's Red socks RIP
Etnz socks it to luna rossa
It explains a lot of what we've been seeing from the sail spotter videos. Specifically, points raised by viewers concerning apparent instability and the crazy speeds. ETNZ are riding on a _knife's edge_ - literally. There's so little foil in the water; their foils have less area to begin with coupled with the canting angle employed which lifts more of the foil into the air. This is truly a fine balancing act and will no doubt result in higher speeds, all else being equal. Hopefully, they have mastered control of the tricky dynamics involved. Amazing insights and analysis.
It also explains a lot of what we're hearing out of LRPP. Jimmy is talking up their maneuvering ability and how hard it is to overtake on these narrow courses. I suspect that they know that they're slower and are pinning their hopes on getting a jump on ETNZ in the start box and then controlling the race from there. If that's true then we'll see some intense match racing if LRPP start in front at any point but a parade if they start even or ETNZ starts ahead.
@@franzfanz It's certainly sizing up to be a spectacular set of races. Two teams with very different boats applying wildly different strategies and philosophies. May the best team win!
Fascinating. Thanks for the excellent analysis.
I LOVE these videos. So much fun getting to geek out with you guys on these engineering nuances. That being said, I sure hope the racing is closer than the VPPs are telling us. Thanks for making such great videos!
Amazing analysis guys. Shocking conclusion too really. On the face of it, this looks like the AC final is going to be a fore gone conclusion.
It’s almost as if NZ designed the boat they wanted, then wrote the rules around their boat design in such a way to disguise their solution as much as possible from their competitors, & driving them down different, sub optimal, design routes.
Thank you guys for this extremely interesting video... most probably more than 50% of the performance of AC75 is coming from foils, rudder included. The team who got it right will win. BTW forza Luna Rossa 🇮🇹
Too complicated for us to analyze...I hope someone got it right. May the best team win and I vote for Italian victory too!
I also think that ENTZ canting the leeward foil also helps drive to windward like a kitesurfer instead of just relying on the vertical part of the arm in water.
Thank you, gentlemen - interesting, informed and erudite as always. Sky Sports should consider bringing this team into commentary for debunking / demystifying some F1 rules & interpretations... :-)
I think the TVNZ commentary team are watching Mozzy. During the Prada cup final, their technical commentary focus was virtually a borrowed script from Mozzy's previous day's episodes.
Better than that, how about Ineos TUK hiring them all for the design and reconnaissance team on the next edition?
Very interesting mozzy but, being an aerodynamic engeneer I wonder why in your consideration you did not consider that the lift schould be considered perpendicular to the surface of the foil. This changes the moment considerations quite a bit. Just curios to know what you think! Thanks
We did, but just drew the vertical component. Thought that would make it clear how the anhedral shifts lift slightly outboard of the bulb. In retrospect should have shown X component and the resultant (perpendicular to foil surface).
Basically they are there, just not shown.
And here’s me thinking flying the tip above the surface was for reduction of drag. But once explained, flying it along with the t shape to max out the CoL is a simple solution. It’s like they started with the sum then figured out the parts in a basic manner, quite kiwi in thinking. If this, what seems basic, solution proves to be a large part of the winning (RM)formula why did the other teams not travel this path? Maybe the execution was too complex relative to risk.
Thanks Mozzy Sails and Rob and Tom for your clever analysis and it’s clear presentation. Hope some Allen jerseys are in the post.
I think that flying the tip of of the water is an added benefit. Hydrodynamic drag is massive compared to aerodynamic drag.
Nice job. Best episode so far👍👍
ETNZ actually have even less wetted surface area relatively since a lot of their volume is on the faring
Your analysis is excellent as a team of 3. It’s impartial and balanced. Keep it up.... we’re in Auckland and planned to take the kids to watch at the viaduct today but have to watch online next Wednesday, as we’re still at level 2 lockdown. If all goes to plan hopefully you three can visit Auckland for AC 2025?!!
If it stays in NZ - whether we win or not it could still go overseas
Not easy to kep up with all that but it was fascinatiing. Thanks.
Very informative! Can't wait for racing to start!
Absolutely fascinating. I can't wait to see if this ends up being the case.
Fantastic. Question: is there a trade off between more righting moment and more leeward drift, in the case of TNZ tips-out foil? Might LR be able to head upwind more acutely, gaining on VMG even if sailing with lower boat speed?
An extra two and a half knots boat speed will bring the apparent wind forward, so I would expect Luna Rossa to point higher than Te Rehutai. Likewise LR might be able to point deeper, downwind. As to the extra horizontal component of the inboard wing on LR, giving her a shove to windward, yep it should be accounted for before we start assuming TR is way faster.
However, if those speeds prove accurate, that’s a hell of a lot to overcome.
Buono Fortuna, a Luna Rossa.
Kia Kaha, Peter and the boys,
Go Te Rehutai!!
@@q.e.d.9112 Providing there will be ideal conditions, it will be much harder to overcome than even that if the speed rumors are true. Several sources claim much higher than 2.5 kts faster. If indeed valid, LR's alleged superior VMG vanishes.
What i find interesting from watching these excellent videos and reading the comments is how far the Americas Cup has moved into the domain of highly complex aeronautical engineering and away from naval architecture... i wonder what the likes of Sir Thomas Lipton and others would have made of all this !
Thanks for the contribution. I agree with the great point of this video but I cannot “grasp” the transition between best righting moment and higher speed, unless it is assumed that the boat with the best righting moment is the one that can therefore allow larger sails.
Maybe you refer to the less wet surface?
You're looking at center of rotation as a straight line down the center of the hull. If you look at this in 3D you have a triangle defined by the center line, and a line between the rudder foil and the leeward foil. So perhaps this means that the heeling axis is defined by a line between the rudder and the leeward foil. So as the boat heels to leeward, it'll pitch a little nose up and thus the angle of attack if the foil increases slightly.
The winning machine I hope Mozzy ! Go ETNZ.
Thanks for the in-depth analysis. We see the theoretical difference in 17 knots - how about at 10 knots? 12 knots? etc? is it increased or decreased at lower wind speeds?
Another great video guys.
So I'm pretty familiar with the VPP pgm and my head hurts trying to think about modeling these boats, good on ya boys...
Great discussion.
I think ETNZ is built for speed, the low wetted surface at speed... low drag, just my $.02.
I love your opening... 'It's the internet, so what you want...'😂
Definitely. The issue then is whether they can get it up and keep it up in light winds. The furlable code zero will help with that. I'd assume they all have one -- it was a big thing back in monohull AC days -- but ETNZ seem to be seriously practicing with theirs.
@@BruceHoult There were some comments in other videos that they opted not to use the code zero in the races. Probably didn't help to lift the boat onto its foils but can't verify that.
Great video, very complex variables. I'm beginning to see that in higher wind slapping the hull into a few waves and a minor touchdown or two is a price worth paying for a few degrees less of foil arm cant and a more vertical foil.
The hull occasionally skimming the surface doesn't appear to shave much speed if at all, judging the distance from the chase boats staying the same when that happens. Besides, ETNZ like to fly close to the water for aerodynamic purposes and it must be an acceptable minor tradeoff to them from all appearances.
. . . .not forgetting the reduction in leeway angle by having the lifting surfaces acting as a centreboard when going to windward. Also having hull lower makes it more of a ground effect flyer.
Thanks guys love your work. For Luna Rosa I hope they don’t watch this because.. they will be piling them selfs.. “impossible impossible”
Now I understand better. Very good work
The vector diagrams describing lift - shouldn't the lift be orthogonal to the wing surfaces?
The total force may be orthogonal, but I think they are only considering the vertical component of the triangle of forces as being relevant to righting moment. The horizontal component is relevant to leeway, which is not being discussed.
Hi Mozzy Men, Things also to consider when making your prediction's for the upcoming races are that it seams Autumn is coming sooner as we have just had rain which has cooled the land and the winds could be closer to 16 knots than the average of 13 Knots for March.
Are you sure of that? I am asking because I have just heard the opposite statement about the weather trend... thank you for more info
I have also heard the opposite Mark. What sources are you using ? You maybe write.
And I am thinking they will be more 10 to 14
Regards John. Auckland
I live and sail in NZ , the cliffs overlooking course E are just down the road. Today both boats.were practicing in 10 to 12 knots and foiling fast . We are in autumn now when normally there are more windless days than usual
That said its been a hot summer with a lot of warm Easterlies and strong afternoon sea breezes so the usual weather patterns may not apply .
Initial races will be on courses A and E. due to COVID level two restrictions.
Have the impression, from previous race course selections by race managers, that these are the least challenging from "emphasis on tactics and boat handling" perspective. Swirly, strong SW on course B has been my favourite so far. Wonder if the old adage of "pick horses for courses" will come into play?
Great and detailed as always
Awesome, thanks for posting 👍
The faster you go ,The less foil you need ,When the tip is out ,less foil .Nice control with out changing any thing
Great video guys, thanks once again
With the anhedral foil, the windward wing can also be set to provide windward lift... ie: added pinch to windward. I wonder if this is part of how LLPP was able to so easily squeeze out Sir Ben. This also could similarly be applied to ETNZ when they lift the arm that 3°.
Also, breaking the surface with the foil produces extra drag, it doesn't just reduce wetted area.
So complex!!! Really appreciate your thoughts and discussions!
Thank you
Great commentary and analysis. I would like to hear comments about effect of anahedral on RM, In regard that LRPPs anahedral is unfaworable configuration dynamicaly.
To elaborate on this, Lets asume equilibrion condition; foil arm strut going through water at 0 deg AOA, both foils (equaly loaded, thus force projecting through bulb and strut), HM and RM moments ate in perfact balance in this point in time (and so are Y forces). Now gust hits, sails start to produce more Y force, boat start to sail with more leeway. Now this bigger leeway is changing lift distribution on anhedral foil in such way that it loads more inboard foil. Obviously this is reducing RM, so trimer is easing traveler more than he would in case of straight foil.?
One more thing, By canting more foil arm TNZ is lowering their boat, but also reducing arm between sail force and foil Y force, thus reducing Heeling moment.
Cup is loosing apeal quickly :( 7:0 for TNZ?
hi guys, interesting analysis, but Tom did not take into consideration the great advantage of the huge angle that the internal semi-foil of the "lunarossa" Y creates when the pierced navigator, almost 45 °, capable of developing a greater upwind angle ...
it will be a great challenge, but the double helmsman could be the big advantage ... !! Hello and congratulations !!
In this configuration, also the independently actuated flaps are a big advantage...
Thanks - well explained Mozzy. How did yachting get into such a pickle with its mixed units? Fortunately we didn't put any values on pressure or righting moment so only heard metres, millimetres, tonnes while forced to mention weight and knots?
(0.54kn =1km/hr)
It's a very old sport.
Forces are calculated in Newtons, moments in Newton/metres. However I often use a conversion to "tonnes-force" as I find it easier to relate when we talk about a boat (+ crew etc) that weighs 7.8 tonnes. 😎
@@maxhugenFirstly a correction moment unites ar Newton-metres. And the total pressure force is 7 8×9.80665=76.5kN assuming their vertical velocity and acceleration are zero and there is no contributing vertical component from rudder/elevator. This discussion is more about the differences in righting moment arm lengths and ignoring other directional dynamic and balancing components so is greatly simplified.🥝🥝🙏
@@MrVaticanRag Certainly, it is simplified. Way too much to cover in a YT video, no matter how long it is! 😎
What I take from this is that one of these boats can be seen in an analogy to a trapezing dinghy (say a Contender, where the skipper and crew are one and the same), where the leeward foil is essentially the hull of the dinghy in the water; the actual hull of the boat is analogous to the body of a trapezing crew; and the windward foil, lifted from the water, is actually analogous to that crew's arms lifted over their head for greater leverage. In this analogy also it makes sense that these boats should sail with their hulls as close to the water as possible without letting them touch, much as a dinghy crew would lower themselves on the trapeze wire. That would maximize the outboard distance of the hull relative to the leeward foil, in the same way as a dinghy crew might go on tiptoe while trapezing.
Hi, do you thought about to stream a live comment during the live stream of the AC races? Would be interesting. What do you think? Cheers Tim
Have you?
He's in the UK. NZ is 13 hours ahead, so 4pm race time here in Auckland is 3am in Blighty.
@@abatesnz so what is the Problem? Bell is ringing at 03:00am. Here in Germany 04:00am. I did it several times👍🙂👍
I watched all the Prada Cup races in real time, from the UK.
Being on New Zealand time was a good antidote to the lockdown and the British winter 😀
@@abatesnz not sure how that’s relevant? You think these boys aren’t already up watching? Aren’t people on lockdown?
@@TheUltimateWriterNZ I bet all three are going to be up in their pyjamas and sponsors jumpers too, maybe at 4am GMT! Certainly it would be great to beef up the commentary though.
Thank you Tom for calculating those relative figures. What a massive advantage for NZ
I doubt that NZ has a 7.5% speed advantage, but we shall see. However, if LR can sail closer to the wind at their optimal VMG than NZ, this will at least partially negate any speed advantage NZ have. Also, in light air, LR can probably turn faster through the tacks.
Idk, I keep thinking that the fact the foil lift is perpendicular to the foil is a factor in parts of the discussion. Paticularly regarding the out board foil for the anhedral foil which horizontal vs pitched significantly on the inboard foil.
Great video, Rob clearly likes to sit on the fence!!!.
Wait till our predictions come out 😂
Been wondering if down force could be created by the IB foil and lift by the OB foi to create righting moment by torquing on the foil arm? And can any positive effect be created by the windward foil flying thru the air or is it matter of air drag reduction?
When ETNZ's tip pierces the surface it creates a smaller lifting surface. ( particularly on the out side half of the foil) Wouldn't that shift the righting moment further inboard on the foil as a whole? Foil length divided by two equals center of effort of foil?
Thanks for the vids guys , great work.
Other factors to take into consideration are manoeuvrability and how the hull "cuts" through the air , how low relative to the surface of the water they fly ....need to put it all together to have a more complete picture , but all your videos have been very formative .
Last but not least , the high mode that LR showed ...can ETNZ match or beat that ?
Fascinating .
Have you considered differences in foil area at different depths, with respect to hydrostatic pressure differences?
Please correct me. Wouldn't the foil lift be roughly in the center of effort of the sails rather than vertical? If that is the case, then excess lift could be used to crab the boat to windward increasing VMG and contribute to even more of an advantage. Great job guys!
What about the drag due to the profile of the foils. I would assume, that etnz needs another profile than LR as their surface area of the foil is smaller. The boats have the same weight so etnz needs higher lift per area on their foils. Is that possible without inceasing the drag of the foil?
In the end it could be faster using a profile with higher lift to surface ratio as you gain drag due to little wetted surface area bit the fact you need another profile could lead to smaller gains of etnz as you predicted in your very interesting and detailed video. Love your argumentation and discussions. Well done
Great catch about the center of lift !!!
Just, following your idea, the center of lift is pushed a bit on the external side because the vertical component of the external (more horizontal) wing should be bigger than the vert. comp. Of the internal wing due to the different angle.
Do you think moving the foil tip out of the water is also cutting hydrodynamic drag, as at high speed even the small foil is probably producing the lifting force with very low and therefore inefficient angles of attack? (Below the maximum Lift/Drag ratio AoA)
Just want to mention another point - moving the center of lift up or down changes the vertical distance from the CE of the sail plan to the CL so it has an effect on the heeling moment.
Indeed, this has been incorporated into our caluclations.
Thanks for these very interesting videos
First - Love your work. Great analysis but can I suggest a coupe of other considerations? A foil piercing the surface has greater drag than one fully submerged. Also a smaller surface area foil with otherwise equal parameters equates to a more highly loaded foil and again greater drag. As you so beautifully put it - it's complicated.
Not related to this video but I haven't seen anybody analyze how Luna Rosa was able to gain ground in headwind without necessarily going faster. I'm not a sailing expert, but I think this is what is highlighted with polar plot. I haven't heard anybody talk about it. I'd love to hear your take on it.
A more important measure is VMG - Velocity Made Good (how fast you are moving towards the next mark). This is calculated from both boat speed and the angle they are sailing at. As an extreme example, if you are sailing at awesome speed, but at 90° to the course, you're not getting any closer to your next mark. In real terms, LR was able to sail closer to the wind than GB during the Challenger Finals, so made better VMG and won.
Theres a big expert debate elsewhere in the comments on precisely your point.
With the anhedral foil, the inboard half needs to have a vector diagram of the lift as only a percentage of the lift will be vertical. With less vertical lift inboard the center of the total lift of the foil will move outboard but the total lift will be less in kg. Do these changes cancel out?
hey, could you comment on longitudinal position of the foils. LRPP has foils in front of the arm, and ETNZ pushed max backwards. I am guessing this makes point of lift for etnz about 1m back. Would be nice what you guys think about that difference. keep up great work!
Fore and aft relative to centre of gravity changes pitch balance and stability. But that can also be changed with foil arm position as well as wing attachment to arm.
I think the attachment to arm is about separating peak pressure but also about foil 'flutter'.
There's a video from a few weeks ago we did touching on this.
I am not an aeronautical engineer, but I am a pilot. What I can say is that getting a tip out of the water is a little bit like having a wingtip collapse in a paraglider. It just doesn't matter. The reduction in surface area of the wing results in higher wing loading, which raises the pressure inside the wing, and under the wing, and resists further collapse.
In the case of a boat, extending a tip from the water will not only increase wing/foil loading, but also reduce drag. I think that's right.
So, the more the tip extends into the air, the more downward force is exerted on the remaining subsurface wing area, pushing it back down.
We know that G=L/D - so a foil tip protruding from the water should automatically increase the glide ratio through the water. The higher glide ratio is compensated for by the increased wing foil loading, which should maintain a steady horizontal ride height.
Or at least that is my understanding - which could be worth exactly what you paid for it. :P
Sorry mate not completly right on that, breaking or even disturbing a surface creates added drag, wheather this is beneficial or not considering that some viscous resistance is gone is to be calculated. but one of the main advantages of moving on foils is that the residual resistance is almost gone (in naval arch. the residual resistance is the one not generated by viscous effects) except for the small sections in wich you break the water
do you have an idea of why the foil tips on Luna Rossa are angled up and constantly piercing the water? Could they be angled down as on moth foils or it will not have the same effect on the anhedral?
Hi guys thanks for the video. I’m not a foils expert but shouldn’t you apply the force vector perpendicular to the foil (cord). If so, when you do the vector analysis you get 2 components: one perpendicular to the water surface (lift) and the other perpendicular to the rudder. This is important, I think, because with the T foils you can’t separate the two effects while with a Y foils you can set them to be different in case you need. Thanks
Very interesting video. However, it appears to me that there is an underlying assumption that the pressure distribution on the leeward foil is symmetrical with respect to the foil strut, similar to the pressure distribution for an aeroplane.
However, for those teams with 2 flap controls, that may not be necessarily true? In fact, they could tweak the span-wise circulation distribution so that the resulting centre of effort is more towards leeward than the corresponding symmetrical distribution obtainable with a single flap actuator.
Any thoughts?
This is very true
Love the analysis guys! Does foil design (anhedral vs flat) impact leeway and therefore VMG?
As ETNZ lifts its foil up so that the tip is out of the water, what about the change in the share of vertical and horizontal components of lift? The doesn't the vertical component decrease and the horizontal increase? How does that change effect the righting moment? Also, not that it effects the comparison of the two boats (probably), isn't the righting moment based on 6.5 tonnes, as about 1 tonne is at the end of the foil arm in the water?
The foil with the tip out of the water has less form drag which will negate the loss of lift. I calculate that the less drag actually favours the lack of lift by a fraction, however the better righting moment is further enhanced giving it two wins for one loss. What I don’t fully understand is how much loss one gets with the foil being closer to the surface with higher percentage of oxygenated water and the higher risk of cavitation. It could mean that team NZ have a lower all out maximum speed than the Italians?
Has anyone looked into / discussed the possibility or option of using the two flaps independently to “torque” the lift effect about the axis to induce righting moment via the pressure differential?
Obviously etnz with the “linked” foil control couldn’t but it would be interesting to know if any teams played with the idea
Ok there may be a speed gain to ETNZ but what about the drift du to less wing below surface? And what will it do to the VMG?
Great videos thx and agree etnz will have a speed edge. I think there is also more that we cannot see. Etnz learnt their lesson in San Fran, we will not see their true performance, only what they need to win.
I also think a key factor will be the VMG, at the last America’s cup TNZ always traveled significantly less distance. They didn’t look that much faster but the vmg was significantly better
@@nickleach3570 The boats are radically different from the last AC, though. Everyone seems to be claiming LR has better VMG this time around. I guess we'll see come race day.
The additional canting is done for cavitation issue not for righting moment I think....Vittorio d'albertas should have a video coming up with some CFD guesses results
Having looked at the anhedral the key is down to splitting lift force and side force. LRPP I believe can control each foil separately. That's when you see the high mode. Using the outermost flap for more lift and the inboard one to go for sideforce.
Your analysis is good but when you factor the above in I think and hope we have a close race
How does the additional canting affect cavitation?
You guys are amazing !,!
Does the shape of ETNZs bow provide some lift and a cushioning effect as the speed increases?
I am convinced in my own mind the hull delivers a small percentage of ground effect lift, more noticeable always on the side where the foil arm is down, using the shape around the "hinge" in a constructive manner to trap air and that sailing with the bow down sometimes touching is part of the equation to give stability and slippiness when one considers the need for the rudder pitch to be as neutral as possible. The flatter surfaced skeg (not as radical as Ineos) I observe as "smacking" the water at over 30 kts which results in any touches acting like those of a skimming stone so it never gets depth and drag and finally, the useful videos put out such as Justin mitchell and sailchaser and airflownz show the latest practice runs of ETNZ having the windward side of the boat "leaning into" the wind on speedy turns! The Total package of a low flying machine.
If it did it would be extremely disadvantageous, because it would negate some of the righting moment
@@pp2793 LRPP also claim some lift from their overall boat shape (like an aerofoil)
@@petertelford5338 I didn't know this, thank you for pointing it out. In my mind this doesn't make any sense, however I get the feeling that the mechanics are much too complicated here for understanding without details.
@@pp2793 Definitely so. We as laymen get the overall idea of what is going on. These videos are incredibly helpful as are the two Italian blokes who draw down from top experts in Italy. They did some good work on foil shapes, profiles, and hull "stickiness" to the water. Like most things in life, it comes down in the end to what happens in reality. That is where the human element comes in. LR with machine like team can pull off some great results. All we want now is some great drama on the water which makes us all feel proud as humans at the ingenuity and effort. Roll on Wednesday! By the way, the weather for Wednesday and Friday is in LR's favour in my view 11 to 18 and 11 to 20 MILES PER HOUR. So 9 to 15 and 9 to 17 knots. on one of the days, the wind is fading away during the day. ETNZ should tread with care not to go 4-0 down!
Nice vid. Maybe try using a de-esser for the audio track, those S sounds are quite loud...
Or a decent pop filter.
Sssserously?
About two people care and they are sound technicians
@@Fifty8day LOL, there seems to be a specialist in every field viewing technical videos..
ETNZ AI is its big advancement has been to test sailing modes in all conditions, with design changes, refined in simulation, before committing to hardware.
In the automotive racing world we call it a roll center.
roll centre is in line with the cg though, they seem to be focused on the centre of lift
The half of the delta shaped anhedral foils will not have its CoP at the laf way point along its span, it will be closer to the bulb and therefore higher and closer to the centre line of the boat i.e . to the keel
NZL worked out a long time ago the aerodynamics should not be lifting the hull but forcing it down. You can see the modification on the Luna Rossa boat was a game changer. But how you can change direction and speed of change under sail load and in close proximity is probably the important race winning formula.
Firstly, love your video’s. Could Tom do the same math with Ineos. It would be great to know if they had no chance mathematically from the word go against Pravda and it would also be great to compare the mathematical assumptions with actual data to get a feel for how accurate the percentage difference is and apply that to team NZ. Cheers
Nice analysis boys
If you'd like to have more righting moment, you could have the hull provide less aerodynamic lift. (or increased down force) The foil has to provide more lift to compensate. I don't know if this is a net gain or not...
If we take righting moment as pointing up (as your diagrams seem to do) then the center of lift (as regards righting moment) is outboard of the foil arm because of the anhedral. The outboard wing lifts. The inboard wing prevents leeway. But then the center of righting moment is well outboard of the foil arm giving LR more righting moment....no?
One other thought. Speed isn't what gets you to the windward mark. It's VMG. Does LR not have more leeway-resistance too, because of the anhedral? And whether they're faster in a straight line or not, are likely to be able to sail higher (and lower) angles?
Sorry if I missed it but have you guys considered the horizontal lift component of the ‘T’ foil adding to the righting moment? I’d need to do some maths to see if this is greater of less than with an anhedral foil. It strikes me that clearly NZ are not needing lift but it’s becoming clear it’s all about the righting moment! - I’ll leave the maths to you boys!