Rudder stops with hydraulic cylinders

Discussion in 'Boat Design' started by Esprit Marine, Jul 19, 2011.

  1. John Riddle
    Joined: Aug 2008
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    John Riddle Junior Member

    Esprit Marine:

    Did you ever determine the cause of the damage to the rudder "housing" reinforcement? (I assume that refers to the top of the tube inside the hull through which the rudder post passes)

    I'm not an engineer but I can see (with just a couple of exceptions) that the position of the stops has nothing to do with the load on the housing. I'm with you - it seems that some underwater load on the rudder would have caused that damage. Whether that load is the result of hitting a solid object or the result of the usual forces exerted on the rudder is debatable but I don't see it having anything to do with stops or the travel of the hydraulic ram.

    The exceptions that come to mind (which are extremely unlikely) are:
    1) A strong stop located sufficiently close to the rudder post to act as a fulcrum when the stop is reached but the ram keeps pushing, thereby damaging the housing or;
    2) Failure of the stop coupled with such a long ram that the tiller arm becomes nearly parallel to it with still enough travel left in the ram to exert side force on the top of the rudder post without imparting any turning moment.

    My guess is they hit something or the housing was not built strongly enough to handle the usual rudder loads.
    Last edited: Aug 31, 2011
  2. serenitycat
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    serenitycat New Member

    Did you install what LS calls the Synchronization valve reference 2200213 ?
    Originally it is a safety pressure valve but it also should in your case have avoided the rudder stop to break. The problem with Craig is that he is no engineer and it is difficult to trust his laminate schedule. We ourselves had quite some issue with the rudder, the daggerboard and the prodder
  3. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    So where were the rudders, daggers & prodder built?
  4. cyclops2
    Joined: Sep 2010
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    cyclops2 Senior Member

    Original post clearly states the problem.

    No one in charge of the project was a experienced hydraulic person.
    It reads like a comedy of passing the blame on someone else.

    All blame for the failure always rests with the company installing the hydraulics. Period. Tough crackers if they did not pick a competant hydraulic engineer / designer.

    ALL GOOD hydraulic stroking systems are NORMALLY allowed to stroke full length. Why ? Because the piston & cylinder ARE THE FINAL STOPS. Good designs have cushioned INTERNAL stops to protect the cylinder parts ONLY !!

    The load they push or pull is assumed to be able to take the full force.

    The design was tested after the accident & found to be of poor & a dangerous design. Considering it was the steering system needed in a storm, There is absolutly no excuse for what happened.

    Failure of a pump pressure relief regulator should in the WORST CASE, just broken any part of the hydraulic system. It should have left the manual system operational. PERIOD !!

    Company should build surfboards. Not ocean going ships.
  5. bertho
    Joined: Aug 2006
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    Location: asean archipelago

    bertho bertho

    esprit marine,
    when you said on your first post" 5 biax 400grm on a PVC tube"..designer need to have some common sense.. I'm wondering if it's the right place to save weight.. (this 5 layer made a 3.5 mm epoxy/ fibre or even less if done under vacuum..+ PVC who should be anyway never used on any structural part on a boat(or just as mold) ..the most weak plastic ever ! check with the NA , personally I will put 5 times this schedule, without any pvc on it..
    this structural area should be more resistant than the piston/cylinder/relief valve/or any thing else.
    best rgds
  6. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    I may have the cables but I'd have to look. E-mail me anyway as I like the apparent fact that you have a Fales. Are you on WBO Yahoo Groups? I hope you're lucky enough to have a 32' Fales.
  7. serenitycat
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    serenitycat New Member


    They are supposed to be built in Australia but exactly where, no idea. Craig did not released this information. They came part of the kit

  8. SPARK1
    Joined: Nov 2010
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    SPARK1 Junior Member

    I would first look at the actual rudder shaft and tube installation. Is there any vertical play in the shaft. Was the correct top bearing used. If it is a rubber type bearing(bush), did it fail? Can the shaft come into direct contact with the tube? Is the shaft still straight? Was the correct hydrolic pump used for the auto pilot and not a more powerful one(faster)?

    The way I see the damage to the tube, it must be caused by the rudder shaft hitting the tube from a failed or dropped bearing. or a force hard enough to move the whole shaft side ways instead of turning the shaft.
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