trailing edge

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

  1. jehardiman
    Joined: Aug 2004
    Posts: 3,314
    Likes: 729, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

  2. Kim Klaka
    Joined: Feb 2017
    Posts: 14
    Likes: 3, Points: 3, Legacy Rep: 10
    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
    Posts: 10
    Likes: 0, Points: 1, Legacy Rep: 10
    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.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.