Where to get papers ?

Discussion in 'Hydrodynamics and Aerodynamics' started by fcfc, Nov 6, 2012.

  1. fcfc
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    fcfc Senior Member

    This one "A New Method for the Prediction of the Side Force on Keel and Rudder of a Sailing Yacht ... " from Keuning, 19th CSYS 2009.

    For a mere individual : no education, no professional.

    NB Not for sale on cafepress/csysonline. They only sell up to 18th CSYS.

  2. Mikko Brummer
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    Mikko Brummer Senior Member

    Here's a copy. Oddly enough, much the same that I used in my VPP in 1989. It discusses the lift carry over from keel to hull, also discussed in winged keel to bulbed keel

    Attached Files:

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  3. fcfc
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    fcfc Senior Member


    What I am investigating is why most recent cruiser/racer have keel area way smaller than Larsson Eliasson PYD suggests.

  4. philSweet
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    philSweet Senior Member

    I think they basically blew the whole zero drift angle thing.

    There is a lot of blind regression going on there. For instance, the calculation of zero lift drift angle could be done based on a simple set of hull parameters based on direct geometric causes, rather than by regression. The most important factor has been left out. In reality, the drift angle is entirely under a designer's control and it is often kept to a low value to minimize the steering effort of cruising sailboats. Heeled sections can be analyzed and their individual moments about the centerline plotted. Vessels which have similar areas under the curve forward and aft of midship will have low drift angles. This used to be considered a fairly important design consideration for full keeled boats.

    I generally get pissed off when a formula fails to recognise that it is trying to account for something that has yet to be determined by the designer. A VPP based on this couldn't be used to optimize hulls because it isn't sensitive to some rather important decisions regarding hull volume distributions. It shouldn't be used to establish handicaps either, because this insensitivity will be exploited to game the rule, and likely produce some strange looking boats if pushed hard.

    All you can say about a decent regression expression is that it's value and it's derivative(s) (we can hope, but I've seen plenty where even the first derivative wasn't constrained) track that of the series it was based on. There is no reason at all to suppose the partial differentials reflect the real world unless this constraint is applied by the regression's creator. They should realize this and identify the significant differentials in light of the purpose of the program the formula is being included in.

    Drift angle expressions should support differentials in some measure of the fore-aft righting moment distribution. Drift angle is unchanging if the distribution is symmetric.

    Off topic, I suppose, sorry for the rant.