Spade rudder design for 40 foot sailboat

Discussion in 'Hydrodynamics and Aerodynamics' started by DennisRB, Dec 15, 2013.

  1. DennisRB
    Joined: Sep 2004
    Posts: 1,270
    Likes: 27, Points: 48, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    Hello guys. I have already made a thread regarding the construction of my new rudder here: http://www.boatdesign.net/forums/fi...k-needs-replacing-foam-core-rudder-49041.html

    [​IMG]

    We have discused some hydrodynamics but I thought I would make a thread on it in this section to talk about shapes specifically.

    The rudder is draft limited as the boat has a shallow draft keel. This fact also makes the rudder a very important lifting surface as its area is about the same as the keel! So upwind performance is not as good a deep keel boat, and I wish to make sure the new rudder has the best possible planform and foil sections to help in this area.

    I plan on getting say 10 plywood foil sections laser cut which I will join up to the armature then add foam between using the plywood formers as a accurate guide for fairing. So I should be able to get an accurate shape. The foil needs to be around 14% due to a thick hollow rudder stock.

    I will probably go for a planform that looks something like this as suggested by PAR.

    [​IMG]

    I am interested in using a more modern foil section. I have read many posts on the subject and have seen a few posts suggesting the 63 series is a poor choice and that there are many more modern sections such as eppler or wortman sections. I would like to learn more about these foils and how to best select them for my purpouse. I have downloaded profili which has a xfoil plugin and am trying to learn to use the predictions etc.

    See the attached pics. It seems the original foil is a 63 series, which appears to not really be the best section to use here? The middle pic is an outline of the rudder section at the top, I believe it is the same all the way down. The other drawing is the original rudder.

    Dennis.
     

    Attached Files:

Loading...
Similar Threads
  1. motorbike
    Replies:
    9
    Views:
    2,278
  2. Cow Cocky
    Replies:
    11
    Views:
    1,314
  3. rubenova
    Replies:
    3
    Views:
    1,294
  4. JerryWo
    Replies:
    4
    Views:
    1,330
  5. seandepagnier
    Replies:
    16
    Views:
    3,319
  6. Claudio Valerio Parboni
    Replies:
    0
    Views:
    1,414
  7. Dave_S
    Replies:
    4
    Views:
    1,554
  8. Dave_S
    Replies:
    7
    Views:
    2,144
  9. 23feet
    Replies:
    3
    Views:
    2,444
  10. WildCard
    Replies:
    20
    Views:
    6,249
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.