Hydraulic ram placement for steering.

Discussion in 'Sailboats' started by RayThackeray, Oct 3, 2011.

  1. RayThackeray
    Joined: Apr 2011
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    RayThackeray Senior Member

    Gerr's book has this passage:

    "...sometimes find it’s installed at right angles to the tiller when the rudder is amidships. This is not good. It puts the cylinder off angle at either end of its stroke. Instead, the cylinder must be installed so that it’s at right angles to the amidships tiller location when the rudder is turned 35 degrees either way..."

    I just can't make out what he's trying to say here. I can't imagine any other way than to mount the ram at right-angles to the tiller arm when the rudder is amidships. If mounted at right-angles when the rudder is 35 degrees one way or the other, then there's surely an asymmetric angle to the tiller when it's at the other rotation?! Confused to say the least.

    Gerr, Dave (2008-12-22). BOAT MECHANICAL SYST HB EB (Kindle Locations 5745-5747). McGraw-Hill.
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Basically, it is bad English. Unless there are some drawings to explain what it means, perpendicular to the center location is the correct installation.
     
  3. michael pierzga
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    michael pierzga Senior Member

  4. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    At sea my internet connection does not allow me to read bandwidth intense blogs. I cant read Sven comment.

    For mannie and his Micro cruiser, good advise for sleeping correctly, is to fit your bunks with air cushions underneath the bunk mattress. This inflatable air cushion could be a simple beach " lie low", inflatable childs "Alligator" or a custom shaped inflatable wedge. The principal is to level out your bunk and keep you from sleeping on one side in a heap, or from rolling side to side in a seaway downwind. Ive used inflatable underbunk cushions for hundreds of thousands of sea miles. They really make the difference between a night of semi sleep and a night of full shut down rest.
     
  5. philSweet
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    philSweet Senior Member

    I think Gerr is correct on this one if you are talking about a balanced cylinder. In Gerr's way, there will be the same stroke excursion and same torque factor applied from center to either side. If perpendicular when centered, neither will be true, so you have a different number of turns center to lock. If using an unbalanced cylinder, you can solve for a location that is least annoying to you.

    In a worst case installation with the cylinder pivot offset only about twice the steering arm length, there is about a 3% difference in the throw from center to in vs from center to out at 35 degrees when the ram is perpendicular to the steering arm with the arm centered. However, torque would differ by about 13% between in and out. More relevantly, the torque at the in position at 35 deg of steering would be about 8% less than if the cylinder was positioned per Gerr. The greater the offset to arm length ratio, the less the effect.
     
  6. CatBuilder

    CatBuilder Previous Member

    Another piggy back question:

    Anyone familiar with the best way to put hydraulic ram steering on a catamaran with kick up rudder cassettes?
     
  7. michael pierzga
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    michael pierzga Senior Member

    Kick up rudder steering
     

    Attached Files:

  8. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Actually he is worried about torque and throw as Phil alluded to. See the sketch below, the lower arrangement is the perfered one.
     

    Attached Files:


  9. ABoatGuy
    Joined: Aug 2004
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    ABoatGuy Member

    I think this is what he intends - see attachement. Same as above
     

    Attached Files:

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