Moving rudder?

Discussion in 'Boat Design' started by frank smith, Dec 28, 2010.

  1. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    What are the consideration for moving a rudder to the transom of a sailboat?
    Frank
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If the rudder was keel/deadwood hung previously, you'll possibly need to evaluate the CLP (or make rigging adjustments) if the boat displays some bad habits afterward. The same would be true if removing a skeg mounted rudder (including the skeg). If it was a blade mounted under the after portions of the hull, you'll probably have no issues that some minor rigging adjustments wouldn't fix.

    Lastly, without more information, such as the make, model and year of boat, what will happen is a crap shoot full of generalities.
     
  3. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    Par , this design has a keel hung rudder with the trailing edge at in line with the transom the rudders trailing edge at the transom.
     
  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    How much separation from the end of the deadwood, will you get if you move it to the transom? If this distance is 10% or less the LWL, then I wouldn't move the rudder. If it's 10% or more and you can stand the blade more upright, then it may be worth the effort if you can also whittle down the deadwood a bit to make a fair flow past it's trailing edge. You'll lose a little efficiency with the top of the blade now out of the water (no hull to act as an end plate), but a better plan form, sectional shapes and aspect ratio can help compensate to some degree. What are you hoping this will accomplish? Is there a prop aperture? A picture would enlighten a lot.
     
  5. gonzo
    Joined: Aug 2002
    Posts: 14,262
    Likes: 581, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    What is the reason to make such a radical change?
     
  6. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    I am looking at an existing design and wondering about modifying it.
    In this case I think a transom mounted rudder may have advantages,
    such as trim tab and a simpler mounting system.
     
  7. gonzo
    Joined: Aug 2002
    Posts: 14,262
    Likes: 581, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The mounting system may not be any simpler, you still have a couple of goudgeons or pintles. The main disadvantages are that stern mounted rudders are easy to damage, and that they ventilate. Also, in rough weather they may come out of the water and make you wipe out. I assume the trim tab is for self steering. You can install that on a keel mounted rudder.
     

  8. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I don't have much issue with a transom mounted rudder, given it's pro's and con's like anything else. It is a much simpler device, doesn't have the leak potential of an inboard setup and if well designed can come reasonably close in preformance of a inboard mount. The real question is what level of preformance are you interested in. If you are so much interested in preformance, then the transom mount may be just the thing. On the other hand a spade through a rudder port would offer several preformance advantages, assuming you have the room to mount this. Ultimately, the amount of separation you have between the deadwood/keel and the new rudder location will determine how much you get from it, though it this is an old CCA style hull, you'll probably not realize very much advantage, because there's just too much boat in front of the rudder.
     
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.