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Thistle3841

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Posts posted by Thistle3841

  1. Not that it’s the biggest difference but I’ve heard the helix structure used in the mains on the North boats is a significant advantage.  Far better control of the luff of the sail, more shape for more power, and less stretch for more consistent shape.  Guesses are that the sails on AM are 8-12% heavier than the other 3 boats.  AM tried to get North to give them blanks and do the finishing themselves and rebrand them, but North declined.  It’s a legit technology.  

    Still, there’s other issues with that boat that are bigger than that right now.  But they know they’re at a deficit on the sails.  Both main and jib.

  2. I'd feel better about AM if they were owning their mistakes. 

    Instead the boat goes quiet when things aren't going their way. The other boats are great examples of how to communicate in a race. AM just isn't. 

    In the media they lay the blame on things they have no control over - the wind, course, etc, instead of taking ownership of the things they are screwing up. 

    It doesn't mean they won't turn it around, but they aren't in a good place right now. 

  3. 1 hour ago, Kate short for Bob said:

    That's why it is pointless showing a country wide Isobar map.

    If you want accuracy then go to localised models - even the upper North Island would be better.  I can't see where a 15 knot South Westerly is coming from.  Even the main Metservice forecast for Auckland is predicting on 9 knots.

    rain-nzni-2021011512-012.gif

    Doesn't this setup for good counterflow for the NE sea breeze?  I'm not sure if the sea breeze is NNE or ENE, but it looks like the gradient should help the sea breeze today, no?

  4. Just now, jsn7821 said:

    NordVPN + Youtube worked great for me from the USA

    I was just offering to help him. Works great for me with SurfShark in the US. I had issues with NordVPN (not related to watching the AC stuff) and finally gave up. 

    • Like 1
  5. 1 hour ago, us7070 said:

    so how are people in the usa going to watch this?

    can i use a vpn, or do i have to pay nbc $175?

    if i can use a vpn, where should i watch it - what country, what network?

    i'm sure this has been covered somewhere.., so sorry, but i couldn't find it

     

     

    Use a VPN and set it to Canada.  

    If you don't have a VPN, I use this one: SurfShark

  6. 9 minutes ago, enigmatically2 said:

    I suspect crashtack was being sarcastic. I got tired of pointing out that when people said that boat x was clearly faster it was almost always the closest.. People think they can still judge it but forget that the zoom of the camera lens distorts our perspective in this matter

    Of course I try to be nice and get made to look like an idiot. 

    • Like 2
  7. 11 hours ago, erdb said:

    This is summarized data from all legs of a race, so it's not good for finding those moments where ETNZ goes into high mode, but maybe these summary histograms also tell the story. This is from race 4 ETNZ vs AM. Upwind TWA and boat speed.

    715224149_uwtwa.png.0ffda99f9a1470826c8a645bcffdf46a.png   175799266_uwbs.png.b1c2940694de48f99b7c5af8738e669a.png

    Overall ETNZ's TWA is much better, but there was a small percentage of data points in the 30 - 35 degree range, which was way beyond what AM could do. There are also some low speed points for ETNZ in the 25-30 kts range, so maybe that's when they go into high mode.

    BTW, this is why I disagree with those who say that upwind starts in this AC are much more important than in the last one, and PB's lack of experience in match racing can hurt ETNZ. First, he might as well win all the starts again when it counts, but even if he starts close second, he can easily get out of the wind shadow of the other boat. It's so easy to escape by going a few degrees lower or higher. If they have just a few % VMG advantage, they'll grind the other boat down. Steering for maximum VMG is much more important than starting well.

    Do you know if the yaw of the boats is similar? I don't know if that data is included but some yaw from NZ would explain some of the angle difference, although not all of a difference that large. 

  8. 10 hours ago, crashtack said:

    Interesting phenomenon where the boat closest to the camera always seems to be a bit faster... can anyone explain this to me?

    The area you're looking at gets bigger the further away it is. Think of a camera outside, where right in front of the camera it only shows a few inches but far away it shows vast distances.

     

    When one object is closer than another it has less distance to cover to cross the screen, so viewing two objects moving at the same speed will have the near object move across the screen more quickly and appear to be faster.

  9. 10 hours ago, crashtack said:

    Interesting phenomenon where the boat closest to the camera always seems to be a bit faster... can anyone explain this to me?

    The area you're looking at gets bigger the further away it is. Think of a camera outside, where right in front of the camera it only shows a few inches but far away it shows vast distances.

    When one object is closer than another it has less distance to cover to cross the screen, so viewing two objects moving at the same speed will have the near object move across the screen more quickly and already to be faster.

  10. 10 hours ago, crashtack said:

    Interesting phenomenon where the boat closest to the camera always seems to be a bit faster... can anyone explain this to me?

    The area you're looking at gets bigger the further away it is. Think of a camera outside, where right in front of the camera it only shows a few inches but far away it shows vast distances.

    When one object is closer than another it has less distance to cover to cross the screen, so viewing two objects moving at the same speed will have the near object move across the screen more quickly and already to be faster.

  11. 10 hours ago, crashtack said:

    Interesting phenomenon where the boat closest to the camera always seems to be a bit faster... can anyone explain this to me?

    The area you're looking at gets bigger the further away it is. Think of a camera outside, where right in front of the camera it only shows a few inches but far away it shows vast distances.

    When one object is closer than another it has less distance to cover to cross the screen, so viewing two objects moving at the same speed will have the near object move across the screen more quickly and already to be faster.

  12. 2 hours ago, idontwan2know said:

    The battens are the measurement points and the fact that the sail "cloth" doesn't go all the way to the end of the batten creates a hollow. The measuring process allows for the measurer to measure the outside dimensions of the sail and to "bridge" any hollows by measuring from one outside point to the next and ignore that there isn't any actual sail there, just battens.

    This is done because sails are 3D but are measured on a flat surface, so sometimes you get these hollows. AM have created them intentionally to get a sail that is smaller than the minimum prescribed in the rules.

    TL;DR - when measured, the whole outline of the sail including the battens counts towards the area even though the cloth doesn't actually cover that whole area.

    The measured area of the sail is larger than the effective area.

    Thanks for that!

    • Like 1
  13. Would someone explain the interpretation on main measurement in layman's terms? I'm trying to visualize the hollow, distortion, and how bridging them allows the sail to be cut smaller than measured area. Regardless, it's quite clever.  

  14. 8 minutes ago, MaxHugen said:

    You may well be right, my grey-matter CFD program can't compute this! :wacko:

    Yes, I did visualise the vortex being created at the sharp edge and beyond (ie to leeward). Mainly because that's where I see a low pressure area forming, which is the precursor to a vortex.

    Pity we don't have a CFD guru here that could whip up some models and run a few scenarios through it.

    I'm just an armchair doing this in my head for fun so I could easily be wrong. But I view the air flow as front to back primarily and secondarily from top to bottom. 

  15. 1 minute ago, MaxHugen said:

    Yes, that is one of the uses of vortices in F1.  From front-on, the 'bottom' of the vortices on either side of the floor pan are acting to keep the airflow 'in' - ie under the car.

    But I visualise a vortex created by Rita's skeg to be rotating the wrong way, and accelerating airflow under the skeg towards the leeward side?

    Ah, I see what you mean. Although my understanding is that a vortex can work as a seal rotating either way. One way is just more effective. No?

    I'm visualizing the vortex flowing down next to the skeg, which I think is opposite the way you see it, then returning air away from the skeg at the water to form the vortex. It wouldn't be a perfect seal and would leak plenty of air under the skeg. 

    • Like 1
  16. 1 hour ago, MaxHugen said:

    "... we went for this very squared bustle to try to create a vortex off the sharp edge that would effectively seal [the gap].” - Muyl. 

    Having seen diagrams of how vortices are used in F1 cars, did I interpret that backwards?  Plus it's adding another useful trailing vortex... 

    Interesting point.  F1 is essentially a niche field of aerodynamics that focuses on vortex management. 

    In F1 they use vortices to seal the floor to the track, especially around the rear tires where they have tire squirt. The better you seal the sides of the floor, the better the diffuser works to create downforce.

    I think what they are saying here is that creating a vortex on the skeg will provide a better seal than other designs when the gap from the skeg to the water isn't zero, which is most of the time. And that will create a better endplate effect. 

    AM seems to be going for a physical seal, which is probably better when it's achieved and worse when there's a gap.

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