The Physical Art of Sailing

Discussion in 'Hydrodynamics and Aerodynamics' started by Leo Lazauskas, Nov 24, 2014.

  1. Leo Lazauskas
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    Leo Lazauskas Senior Member

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  2. sharpii2
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    sharpii2 Senior Member

    I don't see any mystery here. All of these maneuvers are imparting extra energy into the system. Deliberately rolling the boat, side to side, is causing the sail to flap like the wings of a bird. So a portion of the energy the skipper is putting into this, by rocking the boat, is adding to the forward propulsion.

    Other maneuvers may make course changes occur more quickly.
     
  3. CT249
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    CT249 Senior Member

    This may be significant;

    "The movement has components that are both parallel and perpendicular to the flow of air over the sail, creating what the researchers term an "exotic heave," in contrast to a classic flapping motion that would be purely perpendicular to the sail's motion through the air."

    It's interesting because those who race windsurfers - where the rig moves freely and there are few restrictions on pumping - know that moves which would probably fall into the "exotic heave" classification are much more effective than pure flapping. Efficient pumping is quite a skill. Problem is that it effectively removes many other more enjoyable skills when permitted!

    With respect to the team, RSXs could be a much more informative field to study than Lasers, assuming they want to explore all the ways that hysterisis etc affect flow.
     
  4. Petros
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    Petros Senior Member

    the tone of the article I find rather funny, it has been observed for many centuries that they technicians work, and the essay start out with a completely absurd statement "but there is no scientific literature that explains exactly how the moves increase a boat's speed." As if that were necessary to understand it, or know how to use it effectively.

    "We know these techniques are effective, and we're looking into the fluid dynamic reasons why they're effective," IOW, and lot bookish types want to spend a lot of time writing equations (most of which are numerology, in my observation) to try and mathematically explain it. Woop-tee-do, so what will that get us?

    Many years ago when I worked for a defense contractor doing both computational and wind tunnel aerodynamics on miliatry aircraft, there was a young engineer there that got his masters in aerodynamics. At the university they had a wind tunnel large enough to put a human in it and used it to try and improve the lift to drag ratio of ski jumpers under a grant from the US ski federation. The thinking was they would measure L/d of a human in various body positions (arms out, arms in, over the chest, over their head, etc) to try and lengthen their "jump". After a year and many dollars worth of testing, they found that what the most skilled jumpers did naturally (i.e. what felt right when they were in the air), resulted in the best L/D anyway, and the longest jumps.

    There are a lot of very complex things in nature that we do (like sailing, riding a bike, skiing, etc), that are very difficult to analysis analytically becomes of the number of variables (many of which are unknown, or not understood well), that with lots of practice, we humans adapt to and than do naturally without a lot analysis necessary.

    It is called practice, practice, practice.
     
  5. NoEyeDeer
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    NoEyeDeer Senior Member

    All true, but that doesn't mean that greater understanding is a bad thing.
     
  6. gonzo
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    gonzo Senior Member

    "Roll tacking" works well to accelerate after tacking. We started doing that in 71 on Snipes and Penguins. I think they are getting more pronounced now. However, it seems that there isn't a greater advantage. My more moderate rolls keep me at about the same speed as the youngsters. Then they hike out on strong winds and leave me behind.
     
  7. Richard Woods
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    Richard Woods Woods Designs

    Continuous roll tacking is so fast in light winds that it was banned years ago. Even exaggerated rolls are no longer allowed.

    Most top sailors do cheat, by ooching, rocking, hitting the forward bulkhead etc. The challenge for the umpires is to spot them doing it. Certainly the fastest sailors will be the ones who are continuously moving their bodies, even in light winds.

    Maybe 35 years ago Tony Marchaj told me that the fastest way to sail a Finn or Laser downwind would be by the lee with lots of sail twist. But no one tried it until the 1990's when Ben Anslie (I think) perfected the technique.

    Richard Woods
     
  8. CT249
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    CT249 Senior Member

    I'm pretty sure that the technique was very widely known back in the mid '80s, at least. It did advance in the 1990s, probably due to the rise of pro Olympic sailors. My magazine bookshelf collapsed ((*&^% Ikea!) so I can't find any '80s articles to confirm this at the moment.

    I think Marchaj also said that the Finn should be sailed standing-up downwind in a breeze. We know that Elvstrom could do this, and than Mankin also stood up for training, yet neither of them adopted the technique, which leads me to think that Marchaj was wrong and not the guys who beat him and won gold medals and world titles.

    If I recall correctly, in flat water the top Laser sailors actually locked their body in position in light winds; Michael Blackburn advocated placing one hand on the deck to steady the upper body, I think. Of course, in waves you're bouncing the boat in Lasers, but that's largely to steer and to press the bow down to avoid pounding.

    I tend to find that the top sailors are normally fair; at the top end the stakes are high enough to make a protest worthwhile so people are often pretty conservative. There's a difference between pushing the fine line of legality in pumping (which is pretty subjective) and cheating IMHO.
     
  9. Richard Woods
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    Time flies as you age. Maybe it was the 80's, not the 90's, but I know that no one used the by the lee technique in the 1950's - 1980

    I have been a RIB driver for umpires at Laser qualifiers, with the top UK guys racing. I know what I saw and what the umpire was looking for.

    I agree that it's always a tricky one. In flat water its ooching, in waves it's stopping the boat pounding, yet it's still body movements

    Very definitely the fastest boats have the most active crews.

    Richard Woods
     
  10. CT249
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    CT249 Senior Member

    Yep, before Swedish furnituremaking had its revenge I'd gone through a couple of '70s and early '80s articles and noted that the emphasis was much more on using more vang tension to survive downwind in surfing conditions at that time. By '98 I was often adjusting my vang's cascade system to ensure that it was almost block to block when max tension was on, as that allowed an extremely floppy leach which was useful in racing and also in training when we would play with the edges of control when loose leaching. (EDIT; I got that wrong, the idea was to allow the vang to be just tight enough for maximum depowering, but still have the greatest possible length when eased off so the leach could go as flappy as possible, which was actually too flappy for true performance").

    I checked some Olympic vids and saw no ooching in flat water, nor did I see any in my brief time and injury-shortened time as a serious Laser sailor when the Sydney fleet sometimes included Ainslie, Moberg, Lima, Blackburn, etc, who were always up for informal light-wind duels with a local lightweight in the lead up to the 2000 Games. It may have changed since then; last time I sailed against Tom S he reckoned that the judges' approach to extreme roll tacking had been loosened, and that was years ago. Maybe it was just too subtle for me.
     
  11. Petros
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    Petros Senior Member

    I am not saying it is not worth studying and understanding better, they may find a few ways to improve the technique further. It was the tone of the opening paragraphs, almost as if doing these things are "unproven" because no one ever wrote a scientific paper on it. As if we need a scientist to approve of the methods we use to sail a boat, or ride a bike, or any myriad of other things we do for sport or recreation.

    There have been lots of scientific speculation on gravity, nothing conclusive and nothing provable. No experiments worth a darn. So we can say that there is no scientific paper proving the process of gravity. Yet we all know it is exists, and we all use it to our benefit.

    It just strikes me as a silly way to introduce an article announcing that a group of scientists that want to study the motion of sailboats.
     
  12. daiquiri
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    daiquiri Engineering and Design

    Oddly, I haven't read the opening paragraph that way. I took it as a mere observation of the fact that there is apparently no research around which explains the physics of this type of sailboat handling. Which in no way downplays the importance or the validity of this sailing technique. And the cited researchers also say it clearly: "We know these techniques are effective, and we're looking into the fluid dynamic reasons why they're effective".

    And the gravity - we all feel it, know that it exists and use it in countless ways. But we also know that we don't have yet a comprehensive, rational and conclusive physical explanation of what the gravity fundamentally is and how it is created. Once we arrive to that, a door to the whole new technology will likely open for us. Hence the importance of scientific researching and digging into even the apparently most obvious stuff. ;)

    Cheers
     
  13. tdem
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    tdem Senior Member

  14. Petros
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    Petros Senior Member

    That statement appears way down in the body of the text, not in the opening paragraph. the opening for me kind of sets the tone, and it just struck me as an odd way to open such an article.

    I asked my sister, who is a scientist with a PhD in physics, what she knows about the current state of the understanding of the mechanism of gravity. (being an engineer, I thought I might be able to use the research to develop machinery that can use this knowledge, to neutralize it or manipulating in some way or something). Her answer was: "the only thing they have discovered so far is the earth sucks".
     

  15. daiquiri
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    daiquiri Engineering and Design

    Ok, but the fact is - you have read into that opening phrase in a way (rather negative one, if I may say) which is very different from the way I have read into it.

    There is a radio advertisement in Italy these days, in which the actor takes a casual phrase from everyday life and pronounces it in two different ways, putting the emphasis on different words in the phrase. The effect of putting an emphasis on different words is really striking. It completely changes the mood and the meaning of the phrase itself, like putting commas at different places of the same phrase. I feel we might be dealing with a similar effect here. ;)

    But now I am quite side-driving this thread, which should be about this particular sailing technique. My fault for starting this.

    Cheers :)
     
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