SV Pilgrim - 1979 Morgan 382 - Homeport: Beaufort, NC

Saturday, January 3, 2015

Round Two of Templates for Morgan 382 Rudder Modifications

Thanks for the emails and comments on the original post in this series… Creating a template for Morgan 382 Rudder Modifications.

An email suggested checking out alternative modifications to the M382 rudders.  From the Morgan 38 Discussion Board, I have discovered images of couple unique modifications.

This design incorporates a portion of the skeg into the rudder and also fills in the area at the top of the rudder along the hull.  The design appears well balanced and well crafted.   Often our travels take us to shallow waters and/or waters with many floating buoys from crab or lobster traps thus we prefer to retain the fixed skeg forward of the rudder on Pilgrim.

This design adds surface area to the lower section of the keel, but leaves the upper area open.  I think this is a fine solution for blue water or sailors rarely operating in shallow waters.  Again, we feel more confident operating in shallow waters with a full skeg along the leading edge of the rudder.

This M382 rudder modification does not stray far from the later model factory design.  It does include a horizontal plane near the lower edge of the rudder.

This design intrigues me.  If water spilling over the top of the rudder decreases its effectiveness be creating an eddy on the aft side of the rudder, then does a similar effect not occur on the lower edge of the rudder?  Would this short horizontal plane not reduce this effect with little change in rudder weight and wetted surface?  Yet this design is rarely seen… why?  I welcome anyone with insight to comment.

As for Pilgrim’s rudder modifications, using my original template a created  a second template with additional surface area primarily at the top of the rudder.
Smaller, original template on left and new, larger template on right.
I took Colin’s advice… “ It is important to maintain the proper clearance [between rudder and hull].  The later model rudder had more than your template.  The designers had to consider flexing of the hull and resulting distortion in heavy weather. “, and added additional clearance between the hull and the rudder.
Upper section of template viewed from starboard with the rudder centered.

With this design I am able to run my fingers between the hull and the rudder along the full length of the top edge when the rudder is centered.  Moving the rudder hard to port or starboard reduces the clearance.
Second generation template viewed from starboard with rudder hard to port.

I do prefer the larger, second iteration of the rudder modification.  Below is an image with of the larger template with the rudder centered.
Second generation template viewed from starboard with rudder centered. 

Notice any other changes?  Yes… I have sanded down the hull and removed the rudder gudgeon since the first round of images posted a few days ago. 

I’ll save the details of the gudgeon removal for another post.

I would really like to hear your comments on the latest template for Pilgrim’s rudder modifications and any thoughts on adding a horizontal plane to the lower edge of the rudder.


7 comments:

  1. I really like the fence on the bottom of the rudder! Adding this little bit should give more effective rudder area than the deep versions above.

    Do it!

    Bob
    s/v Eolian
    Anacortes

    ReplyDelete
    Replies
    1. I too am in favor of the "fence" at the lower edge of the rudder. Thanks for the endorsement.

      I continue to wonder why this concept is not employed by more manufactures?

      Delete
  2. ... and while we're at it...
    o Why not put a fence on the top as well?
    o Will you pull the rudder to make the modifications? If so, then I ask you: can you pull your shaft with the existing rudder design, without dropping the rudder?

    bob
    s/v Eolian

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    Replies
    1. In latest design the top of Pilgrim's rudder is either against the hull or out of the water. I think a fence at the top is overkill.

      We do plan to pull the rudder then complete the modifications with the rudder off the boat.

      The rudder and the shaft are a single unit. Dropping the rudder requires removing the gudgeon, the steering cables, the quadrant, and the packing nut. Once the rudder and shaft are free then we will elevate the boat with the travel lift to drop the assembly.

      I have already removed the gudgeon, steering cables and quadrant. The packing gland is still in place. I'll devote a future blog post to removing the packing nut as it required fabricating a custom open ended wrench. Hope to free up the packing nut Monday morning.

      Delete
    2. Oops - sorry. I was referring to the prop shaft. Would this be a good time to make modifications that allow the prop shaft to be pulled without dropping the rudder?

      Delete
  3. Ahh - Now I understand your initial question, Good idea. Due to the location of the stock in the rudder I do not believe a modification to allow for pulling the prop shaft is possible. I will take another look at this possibility.

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  4. I have always understood that modifications to the rudder that increase its surface area up near the waterline are less effective than at the bottom. The water sliding off the bottom forms a Vortex which creates drag (regardless of the modification) but the top side is close to the surface so the the water can upsurge.

    ReplyDelete