Foiling boats weight sensitivity?

Discussion in 'Hydrodynamics and Aerodynamics' started by Mikko Brummer, Jun 15, 2021.

  1. Mikko Brummer
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    Mikko Brummer Senior Member

    Now that foiling is strongly in the Olympics (40% of the medals are for foilers, the foiling surfboard IQFoil and foiling kites), one questions how weight sensitive these disciplines will be? Given the same foil area, span & shape, and same sail area, how important will the weight of the sailor (rider?) be? And in a more general case, if you are free to choose your foil & sail area?
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Hi Mikko

    I think what you're eluding to is... 'control'.
    Since the boat is now lifted out of the water, and running/flying on the foils...its MO is now that of an aircraft.
    As such, the balance (LCG) and ability to control said balance is very important for safe flight.

    Thus, how is this achieved??..., as you note, if crew are moving about a lot, and if their weight is not just a minor percentage of the total displacement too.
     
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  3. Mikko Brummer
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    Mikko Brummer Senior Member

    Yes, control is one thing, but I was interested in the influence of pure weight on performance... with a similar equipment, how much will a heavier sailor be handicapped - he will presumably have more righting moment.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    But isn't that, in around about way, the same thing?

    If a rather larger than anticipated crewman gets onboard, that off-set balance needs to be accounted for, and this will be done by the 'control' side.
    It may mean more fin/flap angle than optimum. This of course = more drag... not ideal.
     
  5. Remmlinger
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    Remmlinger engineer

    Whether the additional righting moment is beneficial depends on the lift/drag - ratio of the foil. If the sails create an additional driving force because of the added weight, it depends on the drag-increase of the foil, if there is a net benefit. The increased weight will require an increased lift at the foil, which will increase foil-drag. So it all depends on the L/D-ratio of the foil.
     
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  6. Mikko Brummer
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    Mikko Brummer Senior Member

    So no simple answers? Same thing with a normal dinghy & hiking, too?

    Formula Kite.jpg IQfoil.jpg
     
  7. Alik
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    Alik Senior Member

    Hi Mikko, this is exactly my conern: the foiling classes are very weigth sensitive. WS is moving towards acrobatic 'riders' rather then sailors.
    In simple words, heavier athlet will need larger foil, but larger foil will creates more drag.
     
  8. CT249
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    CT249 Senior Member

    The funny thing is that for many years the Olympic classes favoured heavy sailors, and today events like the America's Cup favour heavy sailors. THAT is apparently considered just fine by heavy sailors...... when THEY are favoured then everything is fine and they never argue that light sailors should have a chance. But when heavy sailors are disadvantaged - and only then - do they suddenly discover that sailors of all physiques should have a chance.

    If sailors of all physiques should have a chance then heavy sailors should have complained when heavy sailors were favoured in the Olympics and now that they are favoured in the AC. To demand "fairness" only when it suits your interests is just hypocrisy.

    Closer to the point, in the Moth the optimum weight has increased since foils arrived because apparent windspeeds are much higher.
     
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  9. revintage
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    revintage Senior Member

    Found this about foiling moth in an old paper.
    EFD2DD6F-5061-4C14-97E4-1C08B9153A3C.png
     
  10. Alik
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    Alik Senior Member

    Would like to know which classes have favored for heavy sailors? In male 470, where helm is 60+ kg, which is well below average?
    Heavy is well above average, say 70-percentile. Those have no option for Olympics now.
     
  11. BlueBell
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    BlueBell "Whatever..."

    Significantly important.
    Insignificantly important.
     
  12. CT249
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    CT249 Senior Member

    The Finn has always favoured heavy sailors. So, I believe, does the O-Jolle (1936 Olympics) and probably even the Firefly in the way it was rigged in the 1948 Games. I'm not sure about the Snowbird or 1924 Monotype. But from 1936 to 1996, there was no singlehander for light sailors - and I can find no record of the Finn sailors complaining about that. In fact in a 1960s interview when the subject was raised, Elvstrom just said that it was perfectly fine that the Olympics were just for bigger sailors.

    The Star favours heavy sailors. So did the FD, and its predecessor the 12 Square Metre Sharpie. The Dragon's optimum crew weight now is 95kg average, and the Soling was only a bit lighter, I believe. Star sailors averaged almost 100kg when they were in the Olympics. I imagine the 5.5's crew weight was fairly high given that Etchells, a similar boat, used to have three very heavy crew.

    So from 1900 - when centreboarders were first used in the Olympics - until the 470 and Tornado arrived in 1976, there seems to have been no Olympic class that favoured medium to light sailors (apart from perhaps the big keelboats and the Swallow). The average Olympic boat sailor seems to have been about 95kg for the vast majority of Olympic sailing history.

    And who, out of the many heavy sailors who sailed FDs, Finns, Stars, Solings, Dragons etc, ever said that the Olympic classes should suit a range of sailor weights? Did the Finns, FDs, Star, Soling or Dragon classes ever demand that there should be a class that suited lighter sailors? No, as far as all my research showed, they completely ignored the ideal of being fair to all weights - until the arrival of the 49er and Laser started to change the picture. Then the Star and Finn sailors started whining, and suddenly invented the idea that all weights should be represented in the Games - a concept that they had never spoken about until it suited their own interests.

    And if the heavy sailors really are serious about the idea that sailors of all weights should be favoured equally in major events, why are they not complaining about the fact that the America's Cup has a target average weight of 95kg? The facts seem clear - the heavy sailors only use the ideal of "fairness" when it suits them.
     
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  13. Alik
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    Alik Senior Member

    This is not true; one can look at historical photos of national Olympic teams of the past, can find very few people over 95kg.
    (Consider also that 50 years ago the people were shorter and lighter than now).

    Why the classes 'favored' heavy sailors, say, 50-100 years ago? Probably because the level of technology the boats were built; those were heavier boats.
    What is the weight of average white male, say, fit for Army service? 86kg I think? In US, about 89kg?How Much Does the Average Man Weigh? https://www.healthline.com/health/mens-health/average-weight-for-men#average-weight-around-the-world

    So why there is no class to sail in Olympic program for anyone over 85kg? Why do they cut out about 50% of white male population?

    This sounds funny. No one complained about weigths on the Intertet forums 50-100 years ago, for sure ;)
     
    Last edited: Jun 16, 2021
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  14. Alik
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    Alik Senior Member


  15. patzefran
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    patzefran patzefran

    IMO, you are right, the rule could specify same foil area / kg and sail area /kg
     
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