planing pods/skis/amas

Discussion in 'Multihulls' started by sigurd, Dec 12, 2004.

  1. tspeer
    Joined: Feb 2002
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    The shape was in no way similar to a NACA 63412 section. From the article, "It's important to realize that the hydrodynamic pressure drag is also very low. The virtue of hte sophisticated Johnson camber shape is that it results in the needed amount of lift, together with a minimum amount of total drag."

    The camber of the surface was a Virgil Johnson three-term section from:

    Johnson, V. E., Jr., "Theoretical and Experimental Investigation of Supercavitating Hydrofoils Operating Near the Free Water Surface," NASA Technical Report R-93, 1961.

    A planing surface is essentially a fully-ventilated hydrofoil with the upper cavity filled with boat instead of vapor. It's got nothing to do with a NACA airfoil shape intended for wings.
     
  2. Doug Lord

    Doug Lord Guest

    Clement step/ Dynaplane design

    My apologies; from the way I remembered it it seemed similar to the bottom of a 63412.
    Just looking again at the article and the picture on page 170 & the ilustration on page 173 there is a certain similarity to me-at least in the last half. What caught my eye was the way the back end of the shape sort of drooped.I was trying just to evoke the shape as I remembered it NOT to suggest that a 63412 section could be used in any respect whatsoever..Poor choice of imagery... But if it were to be tried it would pay to do it right and maybe even get Mr. Clements help and advice.
    The turned down(drooped) portion of the shape(like a partially deployed flap) might be able to be hinged reducing the step to zero. A removable version may or may not be able to be made but it seems like it might be worth a try. If it works then the back end of a final version might be hinged or whatever works. It sure seems to me to be worth investigating further...
    The article is in issue #97 the October/ November 2005 issue p164 "The Evolution of the Dynaplane design".
     

  3. Phil Locker
    Joined: Oct 2004
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    Location: Ottawa, ON, Canada

    Phil Locker Junior Member

    Interesting article. But I'm not sure how applicable the specifics of the planing step for a high speed V bottom hard chined powerboat would be to a soft chined sailing dinghy. Maybe the design translates perfectly, who knows. But I doubt that the control issues that appear at 70 knots are as critical at sailing speeds. The T-foil rudder will help lift the transom, as well as control porposing. Key seems to be to ensure that you ventilate behind the step, either via the chines or through the hull.

    To answer Doug's question, I found a bit of time this week to laminate the inside skin of the hull. Hopefully can start adding internal structure soon. Pictures are updated on the website.

    While a step that pops open like a giant Elvestrom bailer is interesting, it would add a lot of complexity. The point of the boat (for me) is to have something fun to plane around in when the wind is up, so any performance hit from a fixed step in light air is a non-issue. Experimenting with planing pad shapes will come once the basic boat is sorted out and sailing.
     
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