AC72 Rudder Wings

Discussion in 'Stability' started by AeroCat, Oct 6, 2015.

  1. AeroCat
    Joined: Oct 2015
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italia

    AeroCat New Member

    Dear all,
    I'm trying to understand more about trim and the stability of an AC72 foiling Catamaran. Specifically, what about the lift acting on the rudder wings ? Is it pointing upward or downward ?
    Thank you very much for any help you may like to offer.
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,600
    Likes: 301, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Ac 72

    AC 72 rudder foils couldn't be adjusted when racing so they likely worked similar to other foiler rudder foils. The Rave foiler is set up with zero angle of incidence on the rudder foil and +2.5 degrees on the main foils. When the boat takes off the rudder foil lifts vertically but as the boat speeds up and pitches down the rudder foil will begin to pull down automatically.
    Hope this is some help.
     
  3. AeroCat
    Joined: Oct 2015
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italia

    AeroCat New Member

    thank you very much for your answer.
    So, when flying on foils with hulls outside water, an AC72 could control pitch moment only with daggerboard rake angle. Is it true ? i.e. if rudder is set to 0 incidence, the only contribution to righting moment comes from daggerboard lift, and rudder wings only provides stability and doesn't contribute to trimming?
    thanks
     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,600
    Likes: 301, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    The rudder foils automatically contribute to pitch stability throughout the speed range. Daggerboard rake angle was primarily used to set altitude for a specific speed range which depended on the foil design and heave stability of the foil. In 34, foils varied from straight "L" to uptip-the higher the tip was up the better the heave stability and less rake adjustment was required. Some rig adjustments also contributed to pitch stability.
    PS- the daggerboard/uptip foil did not contribute to righting moment.
     
  5. AeroCat
    Joined: Oct 2015
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italia

    AeroCat New Member

    thank you a lot for your answer
     

  6. AeroCat
    Joined: Oct 2015
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Italia

    AeroCat New Member

    Hi! I am now trying to perform a preliminar calculation of the longitudinal righting moment (along boat pitch axis) of an AC72 catamaran in a trimmed foil flying condition. What are major terms to be taken into account in a preliminar estimate of the longitudinal righting moment?
    thanks a lot
     
Loading...
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.