Rudder vibrations Help

Discussion in 'Boat Design' started by Robb swe, Jul 12, 2024.

  1. Robb swe
    Joined: Jul 2024
    Posts: 7
    Likes: 0, Points: 1
    Location: Sweden

    Robb swe Junior Member

    Thanks for looking at this,
    Yes the cutless bearing is new also the axel and propeller is new balanced. I was thinking it was some of these things so we replaced all that. But still the vibrations. When we tested after have replace everything we see that the rudder mount and rudder was vibrating.
     
  2. skaraborgcraft
    Joined: Dec 2020
    Posts: 652
    Likes: 210, Points: 43
    Location: sweden

    skaraborgcraft Senior Member

    It could be natural resonance and cavitation and as pointed out previously, the propeller tip clearance is not best practice. Many boats will have a point in the rev range where things may vibrate and be smooth at different revs.
    Your rudder is not exactly a foil, some filler behind the round bar, or better yet some glassed foam or welded sheet would at least be a step in elimination.
     

  3. Ad Hoc
    Joined: Oct 2008
    Posts: 7,958
    Likes: 1,827, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    The support is insufficient.
    One must always support penetrations/seatings like this in a min of 2 planes of axis. In this case, both long.t and transversely.
    You need an additional support bkt shown in red.

    upload_2024-7-16_9-15-0.png
     
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