Boring propeller shaft through wooden keel...

Discussion in 'Sailboats' started by CanuckGuy, Sep 14, 2009.

  1. CanuckGuy
    Joined: Aug 2008
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: North America

    CanuckGuy Junior Member

    Hi all,

    I'm building a 42' wooden ketch and I'm getting near to the point where I'm going to have to bore the propeller shaft through a 5" thick mahogany keel at a rather large angle.

    I'm preparing for this to be a huge ordeal in itself. If anyone has any tips and comments, I'd be very grateful.

    Attached are a few images for your enjoyment as compensation. =)


    Attached Files:

  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 496, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Measure, measure, measure, then make a drilling jig, usually a few bits of steel tubing and angle stock to fix the drilling angle and provide a way to camp it to the keel. Drilling from both sides and meeting in the middle is less likely to "burst through" then trying to drill completely from one end. Drills wander around, so use a healthy pilot hole. Go slow, check often, good luck.

  3. ecflyer
    Joined: Jan 2009
    Posts: 81
    Likes: 4, Points: 0, Legacy Rep: 72
    Location: Green Bay, Wisconsin

    ecflyer Junior Member

    I just recently drilled a 2.25" hole thru 36" of wood for my prop shaft. I learned so much as it took me over 2 months to accomplish my task. The Geougeon brothers from Bay City,Mi. advised drilling a 3/4" pilot hole which they assured me would veer off some. Then I was to make an internal boring bar and place it thru hardwood bearing blocks on each end to straighten out the hole. I was to gradually enlarge the hole in 3/8th inch increments. That did not work out the greatest. Thru experimentation I discovered a much easier method but a bit more expensive but lightening fast and accurate. I purchased a 3/4" schedule 40 steel pipe 11' long. Then had machine shop make me an adapter that fit the inside dia of the pipe and fit the chuck of my 1/2" drill. I welded this on one end. For the other end, I purchased several size of drill bits designed to fit a 3/4" chuck which enabled them to slide right inside the steel pipe. You could purchase the cheep chineese bits from McMaster-Carr out of Chicago since they will be a single use item. I welded these bits on the other end of my pipe. I started out small and gradually used larger bits uintill I achieved the correct diameter for the stainless shaft tube. I made 2 hardwood bearing blocks that my 3/4" pipe would fit nicely. These blocks must be clamped securely to the boat at the correct angle. I was able to bore a perfectly straight hole using this method, in fact I even corrected my previously bored crooked hole. It is easier if you make a plywood silouette of your engine/transmission and temperorarily mount it at the proper location and height. Then you can use a string or straight edge to draw the drive shaft angle thru the keel before you install the final hull sheeting. Marking both sides in this way assures you of a perfectly straight shaft hole and also lining up with the engine.
    Have a Great Day!
  4. CanuckGuy
    Joined: Aug 2008
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: North America

    CanuckGuy Junior Member

    Earl, thanks for the advice!

    I'm wondering, did you do this before your strip planking was complete (i.e. with an exposed keel)?

  5. wardd
    Joined: Apr 2009
    Posts: 897
    Likes: 37, Points: 0, Legacy Rep: 442
    Location: usa

    wardd Senior Member

    don't know if this will help but in machining when drilling deep holes you start out with short pointy drills so they go straight and increase the drill lengths as you go deeper also the points get less pointy so as not to follow the point of the preceding drill

    also drill in short steps cleaning out the chips that may cause wandering
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.