trailing edge

Discussion in 'Hydrodynamics and Aerodynamics' started by Chaos, Sep 27, 2020.

  1. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

  2. Kim Klaka
    Joined: Feb 2017
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    Location: Fremantle, Western Australia

    Kim Klaka Junior Member

    Be aware that the optimum TE shape for zero leeway is different from that for usual windward leeway angles (3-10 deg). The info is in Hoerner's two volumes, Marchaj, Larsson etc. and is summarised in this extract from my yacht design book (apologies for quasi-advertising):

    “For minimum drag at zero attack angle the trailing edge should be razor sharp. However, a razor sharp trailing edge produces less sideforce than one which is blunt i.e. one that has been cut off (Hoerner & Borst, 1975). These two conflicting performance characteristics become irrelevant in practice. A razor sharp trailing edge is easily damaged, and it is very difficult for antifouling paint to build up to sufficient thickness. A square cut off of 3-4 mm is probably a good compromise for most keels and rudders. If the foil is creating vibrations it may be worth making the cut-off at about 45° (Larsson et al, 2014). This may avoid the generation of a vortex street”
     

  3. Chaos
    Joined: Sep 2014
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    Location: Arkansas

    Chaos Junior Member

    Thanks. I think the info you and others have presented sums up what is going on. I like the 3-4 mm. It seemed that a lot of people had the idea the 1/4 inch TE was written in blood. Obviously, not the case. Thanks to all.
    Ron
     
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