International 14 Mailing List
Re: [I14] leeway angles = AOA

14

From: Jason Werner (jwerner@oleen.com)
Date: Fri 25 Apr 2003 - 05:45:18 BST

  • Next message: Jason Werner: "Re: [I14] leeway angles = AOA"

    Alan,
        Something seems too simple here. For example, where does the coeff of
    lift of that particular planform come into play? I know for a fact that
    different airfoils produce different amounts of lift at the same AoA. So to
    me that would indicate that different setups should account for that. Are
    you indicting a zero lift airfoil (flat plate)? Or at least a constant in
    that regards?

    Just curious

    Jason Werner

    ----- Original Message -----
    From: "Alan Smith" <alans@arcom.com.au>
    To: "Jason Werner" <jwerner@oleen.com>; <14list@i14.org>
    Sent: Thursday, April 24, 2003 7:11 AM
    Subject: Re: [I14] leeway angles = AOA

    > some typical numbers
    > no weather helm
    >
    > boat speed 3 knts c of g 0.75 ft to windward of c of b, auw 500 lbs,
    > distance from c of e sails to c of e cb 11 ft, force on cb 500 X 0.75 / 11
    =
    > 56.8 lbs, leeway angle 4.7 degrees
    > boat speed 8 knots, c of g 5 ft to windward of c of b, force 227 lbs
    leeway
    > angle 2.6 degrees
    >
    > a cb area of 3 square ft has been used in these calculation...leeway angle
    > is inversely proportional to cb area and the square of boat speed ..run
    your
    > own estimates from the base provided above
    >
    >
    >
    > the force on the centre board also induces a drag component which is
    > approximately the force times SIN (leeway angle/2) so it is important to
    > keep the leeway angle small by using sufficient cb area for the conditions
    > of the day

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