Emirates Team New Zealand.

robingimblett

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Some interesting comments by Elise Beavis in today's recon interview. Tat the decreased boat weight is a performance penalty (obviously) but interestingly (to me) that it can be compensated by increased foil span? The foil flap is supposed to operate as one element across whole foil span isn't it? How are they moving the foil centre of lift substantially outboard of foil centreline to affect the lever length?
 

enigmatically2

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Some interesting comments by Elise Beavis in today's recon interview. Tat the decreased boat weight is a performance penalty (obviously) but interestingly (to me) that it can be compensated by increased foil span? The foil flap is supposed to operate as one element across whole foil span isn't it? How are they moving the foil centre of lift substantially outboard of foil centreline to affect the lever length?
The foil design has to be symmetrical, but flap positions can be different on each side. Indeed flap positions can be controlled in segments, so it is possible to maximise lift near the outward tip.

Indeed it would be possible to induce negative lift near the inboard tip to provid more righting moment. But I doubt it would be worth the drag except as a temporary trim
 

barfy

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Some interesting comments by Elise Beavis in today's recon interview. Tat the decreased boat weight is a performance penalty (obviously) but interestingly (to me) that it can be compensated by increased foil span? The foil flap is supposed to operate as one element across whole foil span isn't it? How are they moving the foil centre of lift substantially outboard of foil centreline to affect the lever length?
I thought she was alluding to the new AC class, not the legacy boats. The new class has a wider stance.
 

jmh2002

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Another short clip here too. Breeze is up today:


More wind today from the South West/South - forecast was up to 20kn. Te Rehutai headed to the back paddock first, then out between Waiheke and Motuihe towards Rakino. She returned later in the afternoon through the Rangitoto Channel. Light and heat haze made video difficult but it gives a feel for the smok'n Te Rehutai.


 
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Mozzy Sails

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I think Elise was talking about increase wing span (each foil) allowing higher aspect ratio foils and less drag.

The new foils also have a deeper 'foil box' which at high cant angles puts the lifting surface further away from the hull and increases righting moment. It also puts the foil deeper in to the water.

Whether the teams can actually use that deeper foil box as significant leverage gain will be interesting to see in Barcelona. In practice they may end up having to run lower cant angles and use the extra depth in the rule to prevent significant ventilation.
 

Dogfish

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I thought Elise was saying the new boats have less righting moment because they are lighter the increase in span just about makes up for this but not totally. I think the flap actuators are now hydraulic and that has required a bigger bulge in the foil arm to house them.
 

The_Alchemist

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great video Mozzy




is it possible to not have any flaps and just move the whole foil wing up and down at where it joins the foil arm. This would make the foil wing very simple.
 

Dogfish

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Just to correct a bit, the foil actuators cannot be changed on this boat according to Mozzy as it's not allowed under the rules. Not sure wether you can increase the fairing size to simulate housing hydraulics.
 

enigmatically2

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Here is a radical thought. How much of a factor is the foils drag. In light winds pre-foiling the drag of the hull is more significant. At higher wind speeds they are limited by cavitation, at least down wind. How big is that intermediate bit where they are limited by conventional drag on foils? Or do we think they never reach cavitation speeds upwind?
 

barfy

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Foil drag is a minimal factor, that's why team Ben is testing foils with shoes along the hinge lines. It won't be fast, but they will collect heaps of data.
 


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