No-one else did this: AC Wing Comparison
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- Опубликовано: 7 сен 2024
- @EmiratesTeamNZ have done something with their wings that no other team attempted. But why would they risk such an structurally unstable wing?
Mozzy talks everything foil related with Tom Partington and Rob Gullan with a full digest of the race wings of @americascup 37.
Big thanks to @alinghiredbullracing for the sweet footage of BoatOne
Recon video and photos credit to Recon Photographer / @America's Cup
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Good video. I'm going to watch the ads just to make sure the wine budget is met.
You're the best!
If you get offered a promotional set of six matching wine glasses with your first order maybe send them to Tom as his glass game is a bit lacking by the looks of things.
Love the humility in saying that they aren't sure.
Tbh, they would look foolish othwrwise
As a mechanical engineer who has worked in some form on previous AC boats, I thoroughly enjoyed watching this video while sipping on a Margaret River Bordeaux blend. I can't emphasise enough how much I would like to enjoy a wine of some sort while discussing some of these finer details on AC foil design with you lot. I'm a big fan of the channel, but this has been my favourite so far. The combination of foil design and fluid dynamic physics is fascinating, and if I could only share a discussion over a glass of wine, I would be elated. Kudos to you all, and I look forward to any future discussion leading up to this AC. Cheers.
Carbon fiber manufacturing is far more complex than simple modulus limitation as rob suggests. Optimized strand orientation, nonwoven reinforcement, and internal geometry has a profound impact on directional rigidity of components, making the concept of special kiwi carbon very much within the realm of possibility.
Agreed. Optimized strand orientation makes a huge difference as to twist, which has been an essential design characteristic in carbon windsurfing racing fins for the last 40 years. Nevertheless, this was an excellently instructional discussion. Much thanks!
The foils are all steel
Fair enough. But this is indeed common knowledge and the presenters addressed this. Structurally all the teams will know as much as each other about laying carbon fibre and bonding it. For what it’s worth, I think it will turn out that the impact on ventilation will offset the concern with rigidity. Of course, it will have to offset that, not just match it for it to represent an advantage.
Thank you guys! That was monumental 🎉
My thought also. While I was mostly just flying model slope gliders, I helped with some builds and I know when we were building carbon fiber slope racing gliders (also for Dynamic Soaring), the type of carbon weave and how its oriented / layed up makes a significant different to how it performs under various load directions. Dynamic Soaring is quite challenging as the wings are under high G loading and must be highly resistant to twist (or the wing will flutter at high speed) and normally has a much heavier lay up (weight is usually not such a bad thing in DS as it helps with turbulence stability and a higher glide ratio at speed BUT it must be able take the very high G loads).
So pleased to see you guys all enthusiastic for this event. So many comments from my generation bemoaning the lack of spinnakers and big crews efficient in there work, where as you seem accepting that this is a very special trophy, and to win it you need the technical edge. I’ve appreciated for a few years now your explanations and admit they have made me sound wiser in some conversations, but more importantly helped me enjoy watching these boats more. I personally think you need more recognition from the organising committee.
I am 50 years old and was old school in sailing until foils came into it. I can understand the old school thinking but I bet these comments are mostly coming from actual sailors. The old school boats with the big crews and spinikers were great fun to if you were on the boat but boring for spectators. Especially non sailing spectators.
Love these foiling boats and I am 73 so not all of us oldies are stuck in the past
@@ojnish It's definitely great for sailing because they will attract new talent to the sport. This next cup will have the most people watching in cup history I reckon.
I think Tom P is on the money: "its about maneuvarbility, not speed" (i assume he meant speed as top speed). I think ETNZ has focussed their mast control combined with their foil design to be faster during & out of each tack. Having automated routines around camber control with their dual mainsheet system at the clew, combined with lowest drag foils - means ETNZ wins every tacking battle.
On its own, the straight leading edge doesn't seem like it makes sense if it causes too much twist at high speed. However, if your goal is to accelerate faster out of a tack, or stay on the foils at low speeds during prestarts - then focus on drag reduction at lower speeds by having the slickest foils, and high mainsheet control. We saw in AC36 each tack caused 60 metres loss due to the drop in speed, and time to re-accelerate.
If a team is faster at every tack, you can stay ahead of the guy behind, and if you are behind, you can luff them. Either way, you have a clear advantage. The compromise is slower at top speed. Slingsby said in an interview that whoever wins the start is likely to win the race.
Interesting
Great point, a boat is a system. The only edge is in reducing your weakest link in that system and that is maneuvers.
Depends how close they are. It was true for much of last AC but etnz did prove this wrong in the AC. In choppy, heavy sea conditions I think we can expect more unpredictability, more mistakes and, this will be where maneuverability and fly time will be the cruncher.
Even in sale gp, etnz has built a platform on no mistakes sailing. It does require other things to play out but, keeping those starts tight will matter.
The manoeuvrability idea only works if they have a load of straight line speed advantage that they’re comfortable sacrificing.
Still, last cup showed, as always, that the fastest boat won. Even if Luna Rossa then, in my opinion, had an advantage in manoeuvrability and high/low modes variation. So, what is different now so top speed is less important? Is it the choppiness of Barcelona waters?
I developed foils on everything from windsurfers to high performance 40 footers from ~1980 - 1995. The way I thought of forward swept foils was that they "stuffed" the vortexes up against the hull as an endplate and reduced the induced drag at the tip. The problem with them was that they wanted to twist around the lengthwise axis in exactly the wrong way.
In, say a 0012 with a 30% max thickness, straight or angled back, any twist around the max thick axis reduces the angle of attack. In other words,.going faster tends to lessen the angle of attack, and lift/drag, particularly toward the tip due to twist along the lengthwise axis being close to the tip.
EXAMPLE: Looking from tip to root, leading edge to the left, higher speed will twist the foil counter-clockwise, lessening lift and drag, moreso towards the tip. That usually isn't a problem, and goes unnoticed.
In a forward swept foil, or one very close to being very close to being forward swept, especially with a low drag section with max thick 35-50% back from the tip, the dynamics may change. Now in the example above the twist along the length may be in a clockwise rotation. When that happens it may result in rapid, difficult to predict, changes in angle of attack: increasing lift, drag, and instability, possibly damaging the foil.
The way to deal with that, if it can be dealt with, is to insure that the twist is forced to occur close to the leading edge.
Of your many excellent videos, this is best IMO. The physics explanations with diagrams very helpful together with commentary. Well done, effort well appreciated.
thanks for the in depth conversation about what may be motivating the design choices of each team keep up the good work
Loved the wee intersections of detailed info (the little clips explaining what the hell you're talking about). I think this is the best video you've made so far....
I look forward to all your other AC videos. Thanks,
Glad it was helpful!
Wish you would keep the diagrams up while you continue your discussions.
The X-29 (US experimental aircraft with forward-swept wings) dealt with the positive feedback issue by using carbon fiber's directionality to create an offsetting negative feedback mechanism in the structure itself. The wing inherently tended to twist towards lower tip angle-of-attack as it flexed. Using the structure to cause the tip to wash out this way would also reduce tip stalling, which has the potential ventilation benefits you cite.
There is no reason why ETNZ couldn't have done the same, as simulation and layup techniques have only improved since the 80s. They wouldn't have needed higher-modulus carbon to do it, just a different and very tightly controlled layup.
en.wikipedia.org/wiki/Grumman_X-29#Aeroelastic_considerations
en.wikipedia.org/wiki/Aeroelastic_tailoring
Speaking as a mechanical engineer by training, though I haven't worked as such for a long time
The effective local velocity that each section of a 3D wing sees is the perpendicular component to the swept Leading edge line. Hence if you swept back the wing leading edge line, you are reducing the effective local velocity that each section sees ( that’s good for transonic and supersonic wings). With a more or less straight leading edge line, you are maximising the velocity that each section of the wing sees which maximises lift at each section.
I had bever considered these facts. Despite being a paraglider pilot. Thank you for sharing!
The aeroelastic instability of the forward swept wing may be non-existent in the outboard tip as it seems to be often out of the water, especially in high winds. For the other tip... well I assume that you try to keep the resonance frequencies of the foil out of the expected load frequencies and live to sail another day. The sweep angle seems pretty small so you may not have too much trouble achieving it.
I have not given these matters much thought in 50+ years -- I turned from an aeronautical engineer into a pumpkin (computer guy) some midnight 50+ years ago. So... apologies if I don't make sense. And thanks for the video -- wonderful, although I don't know what the general public will make of aero/hydro elasticity, Young's modulus and such.
Kiwis have been leading carbon use and design for decades. Don't forget John Brittan and the V1000 motorcycle that pioneered carbon fibre in motorcycle frame, forks and even engine parts. The bike cleaned up Ducati's of the time and we're talking 1980's.
Good point.
They actually cleaned up everyone, not just Ducati. Last year I finally saw the last Britton on public display in the world that I hadn't yet seen. Like all the others, stunning.
The reason that you get the effect that Mozzy describes with a forward swept lifting surface is that the centre of lift ends up forward of the centre of the stiffness.This induces the unfavourable twisting as it bends. To remedy this you have to move the centre of stiffness forwards to get it over the centre of lift or even in front of it to get it twisting the other way (angle of attack reduction when bending). If this foil is made from carbon most (80% plus) of the fibres will be aligned along the axis of the foil to deal with the high bending loads. If you swing these forward by say 10 degrees this will do this ( the exact amount will be determined by FEA).This foil does not have a large amount of forward sweep so this should be achievable. I remember Dalts said in a video I saw a few months back that their foils were metal and inferred that everyone was now going for metal. Maybe that’s right ( with metal you can’t fix this problem), or maybe he is giving us some disinformation to keep us in the dark about what they are doing here.
Yes, I saw that interview with dalts and he said very quickly when asked about foils there all steel. Mmmm said it too quick for me to believe!!
Yes- I thought that was slightly weird at the time.
Great video, been following for the last 4 years and its great to see the excitement for this cup building. Looking forward to it!!
I agree with the flow separation argument.
The foil may bend more under load and the extra lift helps in the lift off phase. The bend disappears when the tip breaks the water surface. That the lift decreases when breaking the surface makes the boat more heave stable and you need less correction through the flaps.
The genius is having more lift in light winds and still have low drag in high speeds.
Yes if you align the carbon off axis you can deal with the bend / twist problem . That gives you increased angle of attack at the tip as it bends
Love your videos, thanks for all your detailed explanations. It has made the lead up so much more interesting.
Re: add-ons to the foil box.
IMO, it's not only about weight. During the last cup, I noticed that the water was splashing upward a lot behind the foil arm, where it entered in the water. I always thought it was a significant waste of energy. The new foil boxes with complex shape have little to no vertical splashing behind them and are therefore more efficient. I'd love to hear your opinions on that.
Hey sail nerds! Great conversation and have massive respect for your analytic abilities, really cool. The best AC channel for the tech bits. Thanks Mozzy (and company). I hope your drinking Grappa!
You have already discussed how the triangular planform used to move the center of lift closer to the foil root for structural reasons (also mentioned by several teams) is less than ideal for reasons of increased induced drag compared to a planform that would yield a more elliptical loading. For such a planform, sweeping the wings forward even slightly reverses spanwise flow from root-to-tip to tip-to-root, which helps reduce induced drag for a given angle of attach and improves overall L/D. The resulting reduced tip downwash also allows the foil to operate at higher angles of attack without stalling. So, the Kiwis may be able to lift off in the same light wind on smaller foils with flap and greater overall angle of attack without fear of stalling the foil with a similar level of overall drag. As others have said, I don’t think the slight forward sweep is going to cause any serious twist or associated structural issues.
You suggest that the swept forward foils induce significant inboard span wise flow. The diagram shows a very slight forward inline. Might I suggest that the aim of this is to reduce wing tip vortices. To reduce vortices one would normally have wing tip fences but with an inboard flow the centre structure would naturally do this at zero cost, it has to be there anyway. It will be interesting to see how the foil reacts to sharp turns but I presume that it has been thoroughly tested in all conditions.
Great job guys! Well done! On the question of why not smaller foils, other than struct bending moment and thickness, don't forget cavitation which is directly related to S*Cl. If you drop the S too much then you Cl has to go up limiting your top speed cavitation. In the low speed end, drag due to vorticity (induced) if proportional to Cl^2, so there is another limit there. On the "sweep fwd" we can have a beer about it... Thank you.
Hope that after you have a beer, Mozzy makes a video about it. 🍻
The forwards swept foil will allow the flap to be more effective and efficient as it can maintain a better % crossection over the span, in other words it is quite difficult to keep the flap a constant % along with a flap axis that has a single pivot axis, so with it swept forwards you can more make a better flap that hinges around that single pivot. The forward sweep will also allow increased turning performance and lower speed turning characteristics, some due to the inherent instability of the forward sweep characteristics. Forward sweep also means they can allow for higher angles of attack without stall if needed for faster take off when dropping off the foils
Great video as always Mozzy. Given the differences in sea state we are going to see in Barcelona, I think your theory around limiting ventilation is a good one and probably makes the most logical sense.What we do know about ETNZ is their modelling algorithms are exceptional. So one would assume in design land they have pushed this idea as far as possible for optimal performance and then wound it back to add in a structural failure safety margin they feel confident in. Negating the conversation around structural failure that Tom and Rob were talking about.
While I am no expert, in my view we see a similar issue in banking wing stalls on an aircraft where the lower wing stalls first due to it being down and behind (increasing AOA) and the the upper wing essentially being more forward so has slightly less AOA than the lower wing. Ironically a banking aircraft looks almost identical to a canting foil... Cheers Dylan
I was wondering if one area where twist in the wing/flap may be utilised is in the tip of the wing foil.
In that the outboard tip of the flap may effectively be fixed to the tip of the wing (or so close as to not make a difference).
And with the actuator in the centre, the flap flexes along its length, such that it is basically only the centre 50-60% which moves/deflects.
That could aid in mitigating ventilation.
But would I imagine, require that the forward section of the wing be pretty rigid.
If venting and wave action combined, forward swept portion will act like a ski. Ski's Cl's NP is about 40%-->50%. Also slight forward sweep cancels out the Drag bending motion in the beam equation for aligning fibers. Its a handy cheat. Aircraft have used this cheat for years. Also, spanwise flow coefficient especially with venting = aspect ratio effective is severely limited and that area is dead area anyways so if they turn it into a SKI, they get SOME*** maybe*** lift back, or at least not a negative or null.
New Zealand have always been innovative, going right back to when they first contested the America's cup in a fibreglass 12 metre class boat when everyone else was using aluminium.
Hi. You can add onto that innovation. After the Fremantle regatta and the whole drama regarding our (NZ) fibreglass boat was that they then revealed that they had a fibreglass mast:)
And after the successful defence on the large monohulls in Auckland they showed that they had the solid mast rigging made oval shape to aid wind flow.
@@peterdykzeul3074 We don't do too bad for a small nation in a remote region.
In terms of lift distribution, an elliptical lift distribution first does not require an elliptical wing, as the foil profile of a wing changes over its length, as will the angle of attack and chord/thickness ratio along the span. A fair bit of spanwise flow is controlled by varying of the above parameters. In terms of flexion I don't think it's going to pose an enormous issue here as the degree of sweep in terms of structural thickness etc the leading edge sweep and the sweep of the point of maximum thickness are linked, but not rigidly tied and so it's not impossible for them to build a sufficiently stiff wing especially since much of the thickness of these wings is actually steel since it both provides righting ballast, and is significantly stiffer by volume than carbon, which is very important for hydrofoils. In short, I don't think there's anywhere near enough forward sweep here to be comparing it to an X-29, at most we're talking ASW-15 glider.
Thanks for the thought out reply. Some of the comparisons are extremes to extrapolate out a point. The reality is more subtle.
In terms of other ways of dealing with the elliptical loading that's also true and cut out a segment where we discuss this. But one downside of using washout (twist) and varied sections is that it can make flap control more difficult and end up requiring a thicker section to get adequate control.
Excellent! All correct. but there will always be some, maybe very small, flex and twist, think of the forces involved. The trick is making the center of rotation of twist close enough to the leading edge.
Yes, elliptical distribution does not require elliptical shape. I built some elliptical keels for Ultimate 30's, parallel leading/trailing edges, squared off tip, square to the waterline, by playing with section.
Team nz has been working with rocket lab, rklb so we have space carbon glue stuff going on.
Love it. Three poms trying to figure out if ETNZ have a jump on the rest. It's going to be epic. Kiwis can fly !!!!
ETNZ hold my beer 🍻 while we Send It 💪🏽
All seem to still be living in the UK and no stripes?
Great episode!
Thanks, spread the word!
Indeed, they all are!
Excellent work guys.
Fascinating analytical analysis of foils with some interesting follow up comments being posted, keep it coming . Well done guys love the group discussions, but you now need a drinks sponsor !!!
Love the nerdy chat. Looking forward to the racing starting so we can see how they compare.
my guess. ETNZ leaned a lot from there land speed campaign.
👍🏾👏🏾
The kiwi's always go big, epic awesome or epic fail. This am cup will be one the ages I reckon.
Would it be possible/allowable to have a composite foil construction of Hi tensile alloy (Steel, Titanium etc) and carbon which might provide the structural characteristics required to avoid unstable flexing in the outer sections ? Not sure if this is within the rules or otherwise unfeasible but I attended a talk from a team NZ member after the AC in Bermuda, In this talk they said that as the rudder foils got progressively more slim ETNZ switched from Carbon Fibre to Hi tensile Steel painted black to ensure it still looked like CF to competitors. Not sure if he was pulling our legs but it made for a great yarn.
Did you not see the americans' test foils on their AC40? Definitely steel.
I think the key is being able to shift the lift distribution in towards the centre of the span at highest lift coefficients (low speeds) , with reduced lift coefficients towards tips. This will reduce tendency to cavitate/ventilate at tip penetrating the water surface and still provide most of useful induced drag reducing fencing effects of high aspect ratio - it's a bit like having flaps only on center span of a wing. Effectively it's creating the ability to twist off the hydrofoil just as we do in sails. It might also mean they can usefully reduce the foil thickness, drag and tendency to ventilate/cavitate at highest speeds. There will be a definite winner and loser and a lot of nervous challengers from this reveal.
The higher the speed the more the tip will wobble and more drag will be induced so maneuverability must be the compensating factor. Excellent analysis thanks..
Full marks on your report!
love this channel! mentally stimulating intelligent conversation!
Great vid. Thanks for the effort Mozzy & Co!
It’s all about managing the opponent… this will be done at or near the start. Forcing an error and then running away with great speed…. Maneuverability is absolutely the key…. Watching the test boats I was amazed at what they can and could do repeatedly… having been watching the foiling vessels since there conception the latest developments are absolutely mind blowing… go the kiwis 💪
You have beautifully explained aeroelastic divergence! One way to avoid the divergence is to tune the carbon fibre orientations in a way it moves the elastic axis of the foil ahead of its centre of pressure. There is still a weight penalty associated with this solution but it helps. On an aircraft, a forward swept wing offers better control effectiveness from the ailerons. While the roll authority of the control surfaces decreases as the dynamic pressure increases on a backward swept wing (up to the point of aeroelastic reversal), it improves on a FSW hence giving better control at higher speed.
Great discussion. A few comments and things you might chew on. Think about the associated stress and displacements that occur with loading changes and how a larger plan form (longer chords) may respond with dynamic bending and twist. There may be more flow stability and hence provide better average performance on the smaller plan form. On the structural side, although they are all governed with material and modulus control there is the possibility of someone making a superior structure, (for those primarily loaded in one direction) to use pre-stress.
Thanks for your efforts to keep us informed on state of the art sailing!
Tnz boat looks by far the most stable, mozzy you guys answered the question. Tnz can do all what the others can, but have smaller and better movability.
Purely a guess. But your lift will be more efficient with a straight leading edge. It will also change how you control your yaw in flight mode. Think about landing a delta wing aircraft compared to a cessna with the different yaw approaches.
the yaw is a big factor on these boats, as a lot of the instability is in turns. Where you want that lift to be while slamming a tack is definitely something the teams will have been working on.
Fascinating about the leading edge bending forward. Didn't know that about plane wings and why they aren't that way. Beauty. Go TNZ!!!
I think they're over engineering or Mossy is delving too much.
Ok, good to get a fast wing that's suitable for forecast weather conditions etc.
I think its who's out of the start box 1st AND tacking fast to getting up to speed out of the tack, the quickest will win the races, but there's that ol chessnut little wind to get up on the foils, if the leading boat can keep in front of a quicker straight line boat, tacking will be the ace as long as the following boat follows!
@daedster1 the beauty of this is that we are all guessing. The truth will out soon. I reckon, ultimately, the percentage of maximum potential each team can extract from their vessel is crucial. Meaning a team that gets 98 percent out of a boat that is potentially faster (on paper) than a team that gets 99 percent out of a slower could lose to that slower boat. 😳
So time on the water is critical.
Just another great Video! I'm never 100% sure exactly what is being discussed but you make it understandable and interesting to the novices like myself. I've now got out my old engineering fluid dynamics books to try and give me some insight for this cup haha. Keep up the great work all!
my baseline assumption is that drag is king and that one side of the wing being both in and out of the water is a key detail
Great video guys. Can’t wait to tune into your debrief daily during the AC.
Forward sweeping wing in a jet fighter is theoretically desirable to induce a degree of instability but at an increase of manoeuvrability. However, fly by wire and computer control is required to help the pilot. As a young naval arch, I was toying with this on high aspect ratio keels on non-foiling mono hills. 😊
Love your channel, Mozzy. Such a nice opportunity to nerd about about things besides my actualy engineering job. A couple thoughts...
1) Structural - I agree with the comments about the potential for layup and other variables in the structural design to somehwat undermine the discussion of aero/hydro elastic effects and divergence. A HUGE amount can be done to couple loads and deformation in really interesting ways using fiber angle. E.g., in a prior life I worked on a project to use one piece fully carbon fiber driveshafts on commercial trucks - including having carbon flexures in place of U joints - which could be accommodated with careful selection of layups, geometry, and materials. Those layups are, also, much better damped than your saw (although lovely example)
2) Vortices - One thing not mentioned here, and I may be off on the relevance of this because I don't due hydrodynamics, is vortex formation (or NOT) and control. (The comment about flow separation on forward swept wings is headed in this direction). One of the major changes that happened over the decades in F1 aerodynamics has been a move from thinking broad surfacts and flow fields towards using vortices intentionally as a key component of the aero package. When I look at the last cycle boats, I see this in a lot of ways. Especially in the shaping of wetted surfaces a lot of work to reduce drag directly and manage vortices in fairly traditional ways - e.g., wing tips/fences to reduce tip drag. I can only imagine ventilation and vortices are closely coupled phenomenon. I wonder if this is not an attempt to fundamentally change how the foil interfaces with the water utilizing the leading and trailing edges. I could see a path where this shape has more stable and more useful control of vortices - leading to more stable lift generation. The progression over the last two decades in aircraft has delivered major gains beyond the original wing fences.
3) Stability - Could the movement of the weight higher up (and further forward) be related to the stability kinematics? Effectively - using offset mass to damp instability of the foil itself? You noted the new foil as 'massively unstable' - that instability is in lift generation. But the same amount of total instability (in terms of force) is acting on a lot of moment arms. The weight closer to the center of pressure decreases the rotational inertia, further away increases it. Part of me wonders if you took the fairing off whether that weight has any flex in its mounting.
4) Wing loading and tadeoffs - Higher wing loading in aircraft (and...thats the route TNZ has pushed everyone towards) has a number of secondary impacts as well. They include (improved) gust response, (worsened) stall speed...and takeoff speed, and (potentially decreased) stability. So there are other things to consider in that conversation as well. I imagine those are major considerations as well. All to say, I'm not sure stability is the primary concern for this type of wing? I would be very curious about simulation to performance correlations related to tradeoffs. They are a major challenge in aerodynamics, and understanding why things work in real life that don't work in a tow tank or in a simulation come from a tone of experience which TNZ obviously has.
It is possible to hone the design of the CFRP wing using acoustic emission technology (AET), similar to how the final foil design was approved when I was involved testing the foil under load with AET monitoring.
American teams also bought all the Kevlar for sailcloth the year it was in Australia.
1986/87?
Epic video! Thanks Mozzy.
I'd put this down to a marginal reduction in drag induced by the tip vortex, as the wing shape is typical of glider wings and pre-jet fighters.
We are so close to the start of the cup that I can taste it! Man this one is going to be epic. Can't wait so I have started making my own model AC75 from scratch. The hardest part is making the foils work properly but I am getting there. Have been doing tow testing behind the tinnie. Cheers Mozzy and the guys.👍😁🇦🇺🍻
Please post a video, Spartan902. Would love to see it!😀
@@adhthethird I will when it's finished. Still a bit of money to be spent and ironing out the bugs. I am made a bunch of foils and am still testing. Getting the stern to sit right has been tricky. I have been making model RC catamarans mostly before but that was exceptionally easy compared to foiling boats. I also sailed competitively like Mozzy does for 25 years so I know a lot about sailing. It won't be finished until after the cup has been run I reckon if I'm lucky.
@@adhthethirdI have been taking a few shots on the phone but not ready to put a post together.
Forward swept wings cause more flow towards the root of the wing, increasing lift as they have more area there. They also reduce induced drag as you have less of a pressure differential at the tip. The problem is there incredibly difficult to design, what your missing is the magic of carbon where you can vary the fibre angle to control how the wing bends. Stick some carbon to your saw blade and you can start to control the bending shape. I would be very surprised if etnz don't have a bin full of old wings that didn't quite bend as planned. I'm guessing your allowed to build extra wings if you don't ever get them wet.
The AC boat has 3 foils, tungsten tips could be a thing to stop unwanted deflection and remainder high quality steel.
Elliptical loading is created by a rectangular type planform, not an elliptical shape. The taper reduces tip loss.
Considering all the expertise that went into the last cup it seems funny the challengers all got it so 'wrong'. Perhaps they expected less wind. Other foil sports have found the same thing, apparently as much by trail and error as anything. Regards section thickness it seems to be a case for going as thin as you dare.
As, Slingsby said, they may have a tough time getting out of the water in 6 knots winds😊
slingsbys dreaming never doubt team nz.
Very good video Fellas
Can't wait for the next
Dan was interviewed by Shirley Robertson and let slip some info on how sail rocket goes over 50 knots, could be something to do with that.
He also let slip that he feels 2 boats are off the mark, but obviously wouldn’t name them. He’s guarded but not as guarded as other designers.
@johnmartin7158 He did say that an ac 75 was capable of getting near the speed record if it was specifically designed for it but even if it was heading fractionaly in that direction down wind that might make the difference this cycle...
NZ is blessed with great wine. Enough of it and you too can be a genius designer who will jump up and say, "hey, let's try this crazy idea!"
Great video again guys
the foil looks more like a spitfire wing.... that'll win us the war...
It's nothing like the Spitfire's elliptical wing. If not for the US you would be posting in German. This might still happen.
@@lesp315 The Germans couldn't cross the Channel. It was the Kiwis - Keith Park - what won it. ;-)
@@abatesnz No, Germans couldn't make there mind because they feared of starvation. Only English can survive on English food.
Forward projecting wing, with fluid flow towards the centre/ bulb, means initial separation (inducing cavitation?) happens at the stiffest section, around the bulb. If it happens at the bulb it's also the area with zero lift creation, so it won't disrupt flight. I could be talking drivel, but just visualising... always wanted to be a naval architect. Mech engineering was a close as I got. Now I'm a gardener!😁
You might be able to add something about flower design :)
Great stuff Mozzy and crew, as always. Am I right, there's 2 differences with the fwd swept ( chord), it encourages tip to root flow, and when it bends the twist increases lift at the tip, rather than decreases, ie its unstable. The foils are limited in being symetrical, and ( I think?) only one flap so the upper and lower ( or inner and outer) wings on the stbd side say are normally going to be same shape. BUT, if the lower wing, the one in the water, is twisting extremely, and the upper one, breaking the water surface isn't, then even with a common flap angle they can create asymmetric wings. Does that result in a wider range of lift/drag trade-offs versus a symetrical pair of foils? Perhaps the fully submerged wing can be cranked up for max lift whilst the surface piercing one is lower lift to help prevent cavitation?
As a Kiwi very proud of the massive amazing Emirates team NZ. But we can get it wrong some times let's see if it works. Taihoro is a very happy boat and loves her old foils she may have something to say about the new gear.
Why couldn’t the bend/twist link of the forward swept wing be the reason they’re doing it? One tip out of the water and unloaded would result in an asymmetric twist, loading the deep end of the wing more than the shallow end.
This could allow them to push the wing harder without cavitation. It may also help with ventilation as it will further unload the tip.
NZ also seems to be the only team playing with shortening the wingspan. This could be a high wind option that reduces drag by flying higher (less strut in the water), could reduce wing tip spray drag, or could increase control in choppy conditions.
As ever,a detailed analysis and very informative.A couple of points,any hinge axis can only exist in a straight line which makes it a self regulating feature.Secondly,I wonder if any of the design teams take any notice of racecar trends as Le Mans prototypes switched to "swan neck" rear wing mountings a good while ago in order to allow the best possible airflow beneath their wings (obviously they are chasing downforce so directions reversed).Does anybody else wonder if moving the foil arms aft and the foil forward to get the leading edge perhaps continuous and in clear water would have potential?
The resin matrix could possibly improve the stiffness with the aid of material orientation. This is evident in bicycle frame construction.
As an extremely novice yacht wise,I loved this video
fibre orientation is hugely significant in tortional rigidity. if you need to vary/increase tortional stiffness anywhere along the span it can be achieved with laminate design.
The wings are made of steel which I didn't make clear
You should have at a minimum 133K subscribers for the amount of info you’re putting out.. 💪🏽 Cheers Mate
Would it be turning what others see as an undesirable flex into an advantage by designing a mechanical feedback loop. All other teams will be thinking how do we stiffen up the foils now they’re smaller, whereas TNZ could be thinking how do we make use of the flex we observed last time.
Maybe the flex of the tip or stalling of water around the centre can be measured/monitored - let the sailors know when they are on or close to sailing as high as possible, so that they don’t drop off the foils.
You all seem to forget how much design testing the kiwis have done. If it didnt work they wouldnt be using it..
@@cruiznnz the kiwi’s created the dimensions for the foil box rule after they had already settled on a design, they intentionally gave the competitors a generous space to work with hoping they’d all maximise the dimensions, which they all did. This has the same flavour, limit the modulus to encourage the competition to beef up the foils thickness instead of working with the flex. If I were competing against TNZ, my first thought would be what the trick, are they sending us down the garden path here?
Love the deep dives into the AC tech. Keep up the great work.
Forward oriented foil lift/twist could be alleviated/managed by incorporating in built memory into the foil layup by reverse twist of the laminates
Just a thought
.
If you are doing the same thing as everyone else, you won't win.
This is true for all endeavours, not just sailing.
From what we have seen so far (pretty much the pre-testing back down here in Auckland across a wide range of conditions) Team NZ appear to have found that sweet spot with the new foils that provides more maneuverability and possibly speed without compromising stability. Just like the previous cup. 😄
How do you know?????? You have some new way of working out speed in the same conditions from a camera???? Please tell us how you do this?
@@dulls8475 I can't say, I've been sworn to secrecy by Team NZ. 🎉
@@phillipmurray1724 In future please keep your posts secret so no one can see them. Will be much appreciated by TNZ security branch.
If they were using these foils in NZ how did they avoid them being photographed?
@@tallteacher good point they were actually using their old ones... But my role is one of subterfuge and bluff and keeping competition supporters on their toes 🦶🏻
I thought at least OE milled the foil from steel? Bend characteristics would be fairly constant.
I think most have a steel milled central strut, but then have panels and or carbon wrap to form final shape
Love these videos, so interesting. Could you please post the foil areas of the teams between Ineos and Alinghi.
I am just waiting for a measurement of the ETNZ foil which I should be able to get this week, then I will post them all together. But if you're desperate to see the challenger foil areas they're all posted in the members are of my channel and on patreon.
Kiwis are probably the best boatbuilders in the world.
Quality control and design.
ETNZ foils are built from an extremely strong steel that is normally used in manufacturing to build metal dies and tools. They are fully CNC machined requiring 500 hours plus of CNC machining time.
Wow. And the others?
Nice job
Well done lads.
The forward swept foils will be hydrodynamically tailored by laying up the uni carbon in a direction that stops the tips from twisting up to a higher angle of attack than the root of the foil.
Have Team NZ used a different thickness of their foil at the root vs at the tip? Doing this would allow them to attenuate the flexing. Effectively this could be accomplished by the way they layer the CF. An example of this (from another sport) is the F1 front wing. They all pass the non-flex stress test, but under load, on track, you see them flex.
Speaking from a position of ignorance, could they not design a flap and mechanism that naturally opposes the twist of the main foil? There by passively countering any undesirable twist?
No idea how but just a thought.
Another great video - have enjoyed following your analysis in the lead up. Time is getting close - you must come out with bettings odds in a video soon please! (Can't see sny actual bookmakers with published odds yet)
It's like a Supermarine Spitfire wing and they were one of the most maneuverable aircraft in WW2. It's interesting that the wing information on the Spitfire on Wikipedia discusses many of the same points made in this AC wing video.
Yeah, not new news, just the kiwis decided to take another look...
Your best video and discussion to date, well done.
My thought are the foil that allows for gains at tacking or ability to remain consistent throughout the race will be optimal design rather that those pushing the envelope.
NZ design is risky unless they are confident that they have sufficient control in the matches, as the slightest twitch at high speed will result in a disaster like Patriot pitching and breaking their craft.
I have a small design challenge question and wonder if you might want to help trouble shoot a foil design on a surfski I'm developing?
Awesome episode.
I'm not sure it's truly a swept forward wing but rather as you talked about, the quarter chord sweeps forward. It looks closer to a straight leading edge, not unlike competition aerobatic planes or even the Red Bull Air Race planes. Or, maybe the geometry is such that the other foils have aft swept quarter chords and ETNZ is perpendicular to the centerline? I know from flying model airplanes this is helpful to keep the cp from shifting at higher aoa, effectively minimizing the resulting cg change relative to cp. Not sure how relevant or helpful that would be here though.
Another great video!
A foil must resist both torsion and deflection. So the alignment of fibres is usually at about 45 degrees to the span for torsion while the deflection is countered by fibres along the span line. However the 45 degree fibres are also helping to limit deflection. So perhaps our own Emirates Team NZ has found a combination layup that prevents the forward sweep twist and accepts a slightly softer deflection curve. Maybe they have 30 degree fibres only that do both jobs. Maybe... Not that this suggested "forward sweep" is what I'd call real forward sweep, mind.
God defend tiny New Zealand. What an Anthem. Let's go lads. 🙏🏾💪🏾🇳🇿