Boats and foils comparison

jaysper

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No loophole, NZ just has to use a greater foil AoA, plus greater flap angle, to achieve the same amount of lift.
Actually they did exploit the loophole that allows the teams to include the foil faring weight in the overall nine hundred odd kilos as well as the loophole that allows them to have the two flaps connected by a control mechanism that is magically not part of the flaps.

 

jaysper

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Wellington
Haven't heard of any observations of NZ using different size foil flaps, have you seen this?

Considering GB & LR's foils are some 50% larger than NZ, I think some of our sharp eyed observers would have noticed any substantially larger flaps?
Haven't seen anything Max but you can get more lift 3 ways. AoA as you mentioned, surface area and profile.

 

erdb

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Yep. Makes the smaller foils seem a pretty fucking smart idea right?
This is new to me, too. Where are the rules that specify what can be changed from day to day? I haven't found anything in the class rules, it only lists the max number of components and % of changes. 

 

jaysper

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This is new to me, too. Where are the rules that specify what can be changed from day to day? I haven't found anything in the class rules, it only lists the max number of components and % of changes. 
Can't remember where I saw it. Might have been one of Mozzy's vids.

If you get into trouble with the MC designing your AC75 accordingly, just send them to me and I'll sort them out for you. 

 

JonRowe

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This is new to me, too. Where are the rules that specify what can be changed from day to day? I haven't found anything in the class rules, it only lists the max number of components and % of changes. 
Anything on the measurement certificate cannot be changed without invalidating that measurement certificate, and they I believe have to have the measurement certificate the same across the entire "phase" of competition?

 

erdb

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Anything on the measurement certificate cannot be changed without invalidating that measurement certificate, and they I believe have to have the measurement certificate the same across the entire "phase" of competition?
Yes, I found the rules. It's in the "Match Conditions" document. They have to lock in everything 120 hours before the first race, and everything including flaps need to stay the same for the whole series. 

config rules.JPG

They have to give a list of replacement parts ahead of time in case of damage, and they can only replace stuff from this list if the MC approves the repair/replacement.

So can't switch flaps day to day, you have to choose the best setup based on your long-term forecast.

View attachment Match Conditions (CORD 26).pdf

 

The_Alchemist

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More power with less drag. Pretty powerful combination  :ph34r:

Going off the time stamps of the footage of ETNZ training after the final race verse LR in the final race. ETNZ were 20 seconds faster during their practice upwind after the final race than LR were on their last upwind of the final race.
Well, it looks like NZ could be competitive than.... Hate for the AC to be too one sided for LR...lol

 

erdb

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Hi Erdb, interesting data as ever.  Are the can’t angles the same on both tacks?
Yeah, I looked at it before. It's hard to tell, because obviously there's some variability in the conditions, and they may sail in a low vs high mode for tactical reasons.

Upwind, port vs starboard:

port uw cant.png     sb uw cant.png

LR sails with the same cant angle on both tacks. What's interesting here is how LR was much more locked in whereas INEOS was struggling to find balance.

port uw twa.png     sb uw twa.png

There is quite a bit of variation for both teams in TWA, but for what it's worth, LR had a tighter average TWA on starboard and INEOS had a tighter TWA on port.

Downwind port vs starboard:

port dw cant.png     sb dw cant.png

Downwind, there is 1 deg difference in average cant for LR starboard vs port. Does that make a huge difference? I doubt. INEOS is about the same.

port dw twa.png    sb dw twa.png   

Again, hard to tell if there's any real difference in TWA here. LR sailed deeper on port, INEOS sailed deeper on starboard.

To me it seems they are finetuning something that may make some marginal difference in certain conditions. If it made a huge difference, they would have finalized it and had it set up the same way on both sides. Shows a confident team that was thinking ahead for the Cup all along the series. ...or it's just a busted compass.  :D :D

 
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I think thir theories are sound, they are things I have thought about boat as well. When I saw Mozzies vid I thought he was making it more than it is.
The apparent wind angle going up-wind at 40 knots is (I'd guess) around 10 degrees.  There's no way that wind is not going to rip down between those fairings and hit the main.  There's plenty of Italian wishful thinking in that video :)

 

MaxHugen

Super Anarchist
The apparent wind angle going up-wind at 40 knots is (I'd guess) around 10 degrees.  There's no way that wind is not going to rip down between those fairings and hit the main.  There's plenty of Italian wishful thinking in that video :)
Just watched the English version... and I disagree with their conclusions about the venturi effect. When considering the crew pods, and the sail dividing the area between them, this strongly suggests that there would be an acceleration of airflow on the leeward side, and deceleration to windward, resulting in a pressure differential and therefore sail lift.

Being no expert though, I'll side with NZ's design team, and conclude that the extra 3-4 m2 of low down sail area is quite useful!  :rolleyes:

 

I ride bikes

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Auckland
The hull form itself is not a venturi, but surely the extra part of the sail sheeted towards the side pod is?  The opposite of course is true on the other side, so a high/low pressure differential must also exist in the extra section of mainsail between the pods?

It's almost like tnz created a sail to water endplate, and then worked out how to include the infrastructure and crew within the rules. 


 



 




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