Click for Cross Click for Walker Click for Ocean Alexander Click for Perko Click for Nordhavn

fiberglass shaft logs ?

Discussion in 'Technical Discussion' started by Kenny's Toy, Oct 21, 2007.

You need to be registered and signed in to view this content.
  1. Kenny's Toy, Oct 21, 2007
    #1
    Kenny's Toy

    Kenny's Toy New Member

    Joined:
    Jul 15, 2007
    Messages:
    22
    Location:
    South Caribean
    Hi, I have seen a custom boat that is using a full length fiberglass shaft logs around the shafts( Paul Mann ), aparently this makes the boat go faster, some guys have tried it around here and swear they picked around 2 to 2.5 knots.
    it not so difficult to do, the problem I have is with the zinc anodes on the shafts, what can I do to ground the shaft without anodes ??
  2. Northern Lights, Oct 21, 2007
    #2
    Northern Lights

    Northern Lights New Member

    Joined:
    Sep 25, 2005
    Messages:
    29
    Location:
    San Diego
    cone zincs

    There is a zinc that is fitted to a prop nut. Typically the second locknut that retains the propeller is replaced with a special fitting. The fitting acts as a locknut and is also milled to hold a trailing cone zinc. The zinc now trails the prop hub. Very common fitting for race saiboats.
  3. Kenny's Toy, Oct 22, 2007
    #3
    Kenny's Toy

    Kenny's Toy New Member

    Joined:
    Jul 15, 2007
    Messages:
    22
    Location:
    South Caribean
    Northern, thanks so where can i get some information on this special fitting ?
  4. CODOG, Oct 23, 2007
    #4
    CODOG

    CODOG Senior Member

    Joined:
    Jan 25, 2007
    Messages:
    397
    Location:
    Bournemouth, southern England
    I've not heard of this before. I'd be interested in seeing a photo / link to this.
    A 2 knot increase in speed is a bit much to take on trust, my brain tells me the increased diameter of the shaft 'sheath' would if anything add to drag, unless the mechanics of it work because the rotating surface of the shaft is creating more drag originally. Cant see it personally, but would be happy to be proved wrong. Also, I'd be cautious about blocking the water getting into the P / A bracket bearing if indeed one was fitted. Is this 'sheath' around the shaft cylindical or is it shaped, perhaps with an aerofoil section ?
  5. Spinnaker, Apr 15, 2008
    #5
    Spinnaker

    Spinnaker New Member

    Joined:
    Apr 13, 2008
    Messages:
    14
    Location:
    B.C. Lower Mainland
    Why don't you install shaft brush's and bond them?
  6. K1W1, Apr 15, 2008
    #6
    K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,396
    Location:
    My Office
    Hi,

    What is a full length Fiberglass Shaft Log when it's at home?

    It sounds like this is another term for the Stern Tube to me but I am happy to be corrected.

    BTQ- Zincs are not used for grounding your shaft.
  7. Kenny's Toy, Apr 15, 2008
    #7
    Kenny's Toy

    Kenny's Toy New Member

    Joined:
    Jul 15, 2007
    Messages:
    22
    Location:
    South Caribean
    K1W1 : , shaft tube, stern tube i really don't know how its called :rolleyes:
    but i have seen it work, I think this idea was picked up from some boatbuilder in Stuart, there have been like 5 boats that have done this modification and all of them picked up some speed, im looking to do this myself next month when my boat is hauled..

    Spinnaker : don't know what a shaft brush is :confused: , but I will do a search thank you......
  8. Spinnaker, Apr 15, 2008
    #8
    Spinnaker

    Spinnaker New Member

    Joined:
    Apr 13, 2008
    Messages:
    14
    Location:
    B.C. Lower Mainland
    Shaft brushes work vertually the same as the motor and brushes on an elec. drill. Between the coupler @ the transnision and the shaft log you install a spring loaded lever whereas the spring tension holds the connection against the shaft. This is bonded. http://www.boatelectric.com/shftbrBE.htm These are incredibly easy to fabricate yourself.