Answers to your America's Cup Foil questions

The best thing about my videos is your comments. And the chances are, if a few are asking comments then many are wondering the same. So here is a run through with my replies to your biggest AC75 foil questions.

Thanks to @alinghiredbullracing for their sweet drone footage

Recon video and photos credit to Recon Photographer / @America's Cup

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[MicrophoneAssassin]

Hey Mozzy, just wanted to shout out the notable increase you've made in overall production quality and narration from last run or the cup. You've become an excellent "public" speaker and the technical quality now matches that of the content. Super excited to watch this AC cycle with you

[MBCGRS]

I work for the engineering company that makes the foils for ETNZ. The mono-blocks of billet these are machined out of are huge. It's great just standing and watching the machine cut. (It's very large). Great video.

[pkpwnerful]

Have watched every one of your videos front to back this past year Mozzy! I get so excited when I see a new one in my feed. And nice job shutting down that know it all at the end there, twice the stress of a F-16 wing spec! Wild. Definitely gonna bring that up at the dinner table sometime soon.

[yellowpitch]

Juan K has entered the chat!?!
Famous to me as well.
Great segment.

[nickl]

@MossySails - great format.
Great idea to draw such interesting content and discussion from your viewers and their comments.
As I guess most here viewing your channel are either skilled enthusiasts or, like you and the guys, proper pros in the fields you cover, thanks for keeping your coverage focused on the engineering and racecraft!! You've got the tone spot on!

[adrianthompson]

Brilliant analysis leaving us some lovely nuggets of design to chew over. Your calculated foil loading of 7000 plus kg is based on the full planform area. The teams that have split flaps with no structural continuity through the centreline will be even more challenged. You can probably knock off nearly 40% of the effective structural foil area at the root, leaving an even higher loading on what's left.

[dinky]

An interesting comparison of aircraft and sail boats. Both count as extreme in different ways. But I've seen almost every part of boats break when pushed hard enough.

[kevingerald]

Hi Mozzy, great analysis and interaction with your followers. Keep them coming. 👍

[charlottescott]

Thank you Mozzy. I am a sailing enthusiast and know little about engineering but can follow a lot of what you say!

[freeaccess]

Mozzy, you are the Premier source of information about the AC. Great technical video.

[greenstripeypaint]

Thank you Mozzy - the excitement ramps up another notch

[AlanMerry]

Very happy to watch your updates on the AC37. Not sure if it is possible but would be great to see any analysis of the current on water activity in Barcelona.

[Coolcmsc]

Very interesting about the extreme loads, although I had at least worked that out. But what I hadn’t considered is the distribution of those loads onto the flaps. Or, more specifically, into their little hinges and their presumably thin couplings to their actuators. Intuitively, that hinge functionality seems extraordinary to me under these loads. I’d love to hear you explain this aspect of the foil loading please.

Also, for those who’d like a real world example of how much load that is: those really big round bales of hay we see in a farmer’s field wrapped in plastic (which are almost impossible to move for a human) weigh - just - 400Kg each… So, it’s something like 18 of them = this amount of load on the little foil. And that is more of those bales than can fit on a really big trailer behind a giant farm tractor!

[gheckolock]

What if the forward sweep has to do with surface piercing? The tip that breaks the surface will have its lift twisting off while the tip in deep water will twist on lift. I think they figured out a way to make the foils act as if they are asymmetrical. Reducing cavitation at the surface and increasing lift in deep water.

[TheLDunn]

DARPA have been experimenting with active flight controls. These have no moving flaps, but instead have outlets on the wings where air is vented to modify the lift characteristics. No moving flaps leading to more efficient, lower drag designs.

Just wondering if any team has considered something similar (but maybe with water) to control the lift from their foils. Evidence from aircraft experiments seems positive, and maybe something AC boats could exploit.

[warp]

I think one aspect was not mentioned yet. The flap percentage along wingspan. It is beneficial to have max percentage in the center and decreasing percentage further out. Since the hing-line is given, forward sweeps allows to decrease flap percentage more aggressive towards the tip. And maybe even have the tips fixed and twisting the flap while its deflected.

[Spartan]

I am still blown away by the fact that such a big beast can get up on such a small foil in 5-6 knots of breeze. Just think where technology will take these boats into the future. Step aside F1, you have competition in the technology development department. It's brilliant to see because F1 is now boring as bat sh-t. Cheers Mozzy. Less than 2 weeks to the You bloody beauty!

[patrickchase]

I think that the question about whether the ETNZ foil is truly forward swept is indirectly onto something.

While I agree with you that it technically is forward-swept, it's only slightly so, and that matters here. The distance by which the tip is advanced relative to the root is a lever arm, the length of which determines the magnitude of the torsional load causing divergence. Going back to your saw example, as you reduce the amount of "forward sweep" you'll find that it takes more force on the tip to produce any given amount of twist. It may be that ETNZ were able to make their steel foil rigid enough to withstand the (relatively small) torsional loads created by its small amount of forward sweep.

[ChimeraActual]

Another great vid, TY.

Thank you for calculating the forces on the wing, I knew they had to be right up there, but that's more than I expected. Steel may be the only material with the mass and rigidity to work.

BTW, even if the flaps appear continuous, that doesn't rule out the possibility that the center section has some flex. Not saying it does, just that it's possible.

[JanHolland-wd]

Love the technical discussions on this channel as I am learning lots! Remember Sailrocket? I guess you do. Back in the day they claimed to have made a breakthrough regarding cavitation. There's an outfit on your side of the Channel by the name of Aerotrope who've claimed to have been involved with SR. Would be interesting to find out if they are YT interview material ...