dorox

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Everything posted by dorox

  1. dorox

    The new sailing twin skin setup

    The last one, headsail (without mast, single skin): L/D = 14.208 Hmm, I guess I'm calculating L/D wrongly there, numbers aren't making much sense. will redo it another day. It would be helpful if someone gives me the cross section dimensions for ac50 wing, and ac75 mast and sail - that would make the simulation a bit more relevant
  2. dorox

    The new sailing twin skin setup

    While having a little time to procrastinate I have tried to see the difference in lift-to-drag ratio(L/D) between different wing and mast designs - lets see your opinions. The simulation is for a 10 m/s wind at an angle of 6deg to the wing (sail). Symmetrical single wing: L/D = 8.8243 Non-symmetrical wing (it is similar to double-skin sail): L/D = 9.0541 Circular mast with a single skin sail : L/D = 22.934
  3. dorox

    Artemis?

    Seems like Artemis is taking part in the work on the design rule. Did they officially announce the challenge? Or is it a random person wearing an artemis hat? (screenshot from the recent ETNZ video)
  4. Nope, this guy is not a commodore of St Peterburg YC. He is the owner of watste processing company, alcohol producer, and a lecturer in a university . It does not seem like he has any connections to Gazprom. Valentin is actually the leader of the Synergy racing team - the one which participated in ACWS in 2011 under the name of "Ё-Challange" according to russian press https://itboat.com/articles/263-kubok-ameriki-rossiya-uchastvuet. I can not confirm this as I did not follow AC at that time, but there is a picture of the boat (could be photoshopped). The interesting thing is that Synergy wanted to compete in 34th AC, but the cost was too high."The cost has grown from 20 millions euro for 32 AC to 60millions for 34 AC... I am not sure that there is anybody willing to compete at that price in Russia" https://itboat.com/articles/183-kogda-nibud-my-ego-zaberem
  5. dorox

    Team NYYC

    Waiting for Russian hackers to steal ETNZ's simulation software
  6. dorox

    AC36 Protocol - Ask Dalts

    Good job asking about the bulb. Now one can imagine their 2 options are: with and without ballasted keel (?)
  7. dorox

    AC36 Protocol - Ask Dalts

    Will the videos from ac34 and ac35 be published on youtube? Will the race management publish boats telemetry as it has been done before?
  8. dorox

    Next USA Team

    I can assure you - you woudn't see a potential AC founder there
  9. dorox

    Next USA Team

    Nobody cares about sailing in Russia. It is just too far from being a national sport. And the oligarchs are having fun in RC44 which they can actually sail, as opposed to modern AC. There is also a language barrirer and the price of oil. There was an interesting endeavour of Gazprom with ESS, but it failed.
  10. Today's data. Oracle had non symmetric foils - look at the speed difference on the polar - port foil was worse. Not much of the straight line speed difference I would say. Probably tacking is killing them.
  11. Yes, and the median TWS is higher for NZL, which supports the point. I don't see much speed differential, not at all. Probably the most gains were created by maneuvers. I need to find the way to analyse that.
  12. dorox

    Oracle Team USA

    Today's portion of "analytics": Tactics: median TWS for NZL - 8.7kn, USA - 8.5kn. Tacking: average VMG at TWA<30deg: NZL-13.8, USA- 13.13 Gibing: average VMG at TWA>160deg: NZL - 23.86, USA - 17.86
  13. dorox

    Team NZ

    Today's portion of "analytics": Tactics: median TWS for NZL - 8.7kn, USA - 8.5kn. Tacking: average VMG at TWA<30deg: NZL-13.8, USA- 13.13 Gibing: average VMG at TWA>160deg: NZL - 23.86, USA - 17.86
  14. Today's portion of "analytics": Tactics: median TWS for NZL - 8.7kn, USA - 8.5kn. Tacking: average VMG at TWA<30deg: NZL-13.8, USA- 13.13 Gibing: average VMG at TWA>160deg: NZL - 23.86, USA - 17.86
  15. New interpretations on rudder wings with nice pictures: https://docs.google.com/a/acracemgt.com/viewer?a=v&pid=sites&srcid=YWNyYWNlbWd0LmNvbXxub3RpY2Vib2FyZHxneDozOTUzMTc4ZGI2ZGFhOGFl https://docs.google.com/a/acracemgt.com/viewer?a=v&pid=sites&srcid=YWNyYWNlbWd0LmNvbXxub3RpY2Vib2FyZHxneDo3ZGE3NzkyOWM2NzU1Y2Vm
  16. I don`t know exactly, but my guess is that because there is larger heeling moment from the wing. This heeling is balanced by higher lift on the foil when compared to downwind. And higher lift equals to bigger angle of attack which leads to lower pressure around the foil. In simplier terms, for downwind foil is used to support only weight of the boat. For upwind it supports weight plus increases righting moment which requires higher lift.
  17. What I found interesting is the top limit they hit at high wind speed: appr. 15kn VMG or 25 kn SOG. I think this should be cavitation speed in upwind mode. Keep in mind that cavitation causes damage to appendages - they do not want to sail 100% unless it is their last cup race
  18. The dots I plotted are at "steady state" sailing. It is defined as change of average SOG over 10 s is less than 0.1kn and change of a COG over 10s is less than 0.1deg. Look at the polars - the course is changing within 20 deg when going upwind: sometimes they sail lower/higher, or they might put more or less pressure on the boat by adjusting the wing (they dont need to go 100% all the time, just enough to beat SWE)- this affects VMG.
  19. dorox

    Team NZ

    That's just one race. Every point represents a steady state straight line sailing for 10 sec. When all races are plotted on one graph it gets very messy.
  20. dorox

    Team NZ

    Well, polar graph on the top shows speed in knots at different sailing angles. 0 - dead upwind, 180- dead downwind. The lots of dots between 30 and 60 is the starboard upwind tack. Dots between 210 and 240 represent port downwind. Those two directions they sailed most of the time because the wind shifted right quite a lot. The bottom one is basically proportional to the lift to drag ratio of the wing and foil combined. The typical value for a keelboat would be 0.2 - 0.3. You see how Artemis is worse than NZL in light wind. And also is interesting how both teams basically hit the limit at high wind speed.
  21. dorox

    Team NZ

    Today NZL average upwind VMG of 14.8 against 13.4 of SWE. This difference of 1.4 kn equals to 200 m gain over 5 min of upwind sailing - pretty much what we saw today.
  22. Today's analysis. NZL is much faster upwind: average VMG of 14.8 against 13.4 of SWE. This difference of 1.4 kn equals to 200 m gain over 5 min of upwind sailing - pretty much what we saw today.
  23. I'm actually using MATLAB. The issue with polars is that boats are really sailing only upwind or downwind. And for both modes I would expect the sailors to go for best VMG mode most of the time. So the best approach is to plot VMG in one way or another. However polars are very illustrative especially for casual public.
  24. Thanks Stingray. Did oracle use only one set of foils over challenger series? It would be interesting now to compare their performance to the kiwis. Nodrog: it was yesterday and ACEA didn't bother to upload that data yet.