Extending Rudder Shaft

Discussion in 'Boat Design' started by bristol27, Jul 3, 2012.

  1. bristol27
    Joined: Oct 2011
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    Location: Portland, OR

    bristol27 Junior Member

    I am hoping to do away with the rudder stuffing box.

    My idea is to fiberglass in an extended rudder tube. The tube would run from the existing rudder shaft tube, to the underside of the cockpit and would be fully water-tight. I would like to make this modification, because it's the only reason I need to access the below cockpit area and I am hoping to fill the area below the cockpit with flotation foam. Further, no stuffing box is one less point of failure and leaks. Additionally, the entire tiller head base and rudder shaft would be greatly strengthened.

    I've attached an image of my plan to this post. The red lines indicate where the shaft tube will be extended. (Please excuse the old image as well as being slightly out of focus; it was the best image I had at this time)

    I don't really see why this plan wouldn't work. I'm wondering if I'm missing something. For example, perhaps the the stuffing box provides some kind of lubrication required for turning the rudder?

    Attached Files:

  2. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Bristol27--The modification will work in principle. The stuffing box keeps water out and does provide a bearing of support for the rudder shaft at the lower end. You probably have another bearing of sorts at the deck. When you make the modification, you should set it up so that you keep a bearing at each end, and these are probably best installed from the ends of the tube. So you will likely need a new sleeve bearing at the hull end and installed from outside, and the same or similar one at the deck end installed from above deck.

    The modification is worthwhile, it does indeed eliminate a site for potential leak into the boat.

    Good luck with the modification.

  3. BMcF
    Joined: Mar 2007
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    BMcF Senior Member

    I recently made some replacement hardware and some repairs to the shaft on an older sailboat rudder that was installed almost exactly as you propose. Instead of a permanent structural tube, however, this one had 2" hose couplings top and bottom, just below tiller support bearing at deck level and just above the lower stock bearing where it went through the hull, with a piece of reinforced 2" hose between them.

    Looking at the corrosion markings on the rudder stock, I would guess that the average waterline (hence.."freeboard" before leakage) inside the hose was probably a good 8-10" below the top bearing and hose connection. Lots less maintenance than a stuffing box..and less wear on the rudder stock too.
  4. bristol27
    Joined: Oct 2011
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    Location: Portland, OR

    bristol27 Junior Member

    Thanks for both your inputs.

    The idea to use hose couplings seems like a fairly good suggestion, although I tend to always prefer a permanent installation. Since I'm rebuilding the whole boat anyway, I'm not afraid of a little extra fiberglassing.

    I'll have to give the exact method for extending the tube some thought, but at least I know it's feasible. Many thanks, again.
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    As Eric has pointed out, an external bearing at the lower end, is the way to go. It can be repaired without flooding the boat and you'll still need an upper end of the tube bearing, but this is a given.

    Think carefully about flooding an area with pour in foam. What happens if you have a hard grounding and the shaft tube cracks? You'll be digging through foam for a while to get at it and if this occurs while afloat and some flooding happens, you'll never have time to get a band-aid around the tube. Consider buoyancy bladders or chambers instead. Also you could compartmentalize the area, leaving access to the shaft tube, while still having floatation all around.

  6. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I have seen more than a couple boat split in half from pour in foam. I once damaged a wall in my boat with the can stuff. Fill area with ping pong balls. :)
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