extruded rudders and centreboards

Discussion in 'Boat Design' started by grob, Jun 10, 2009.

  1. Steve W
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    Steve W Senior Member

    Nice, any plans on making extrusions of a size suitable for bigger boats, perhaps as a keel fin for the bulb keel on a smaller sport boat. There used to be a company in Europe making such extrusions but I have not been able to track them down.

  2. tspeer
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    tspeer Senior Member

    Just be advised that moisture will cause a bonded aluminum joint like this to fail in time. There are ways of preparing the surface to make a secure joint, that consists of an acid bath to etch the surface, followed by phosphoric acid anodizing process to build up a strong oxide coating to which the epoxy actually adheres. Andrew Marshall describes it in his book, Composite Basics.

    For a dinghy rudder, failure of the joint is an inconvenience but not exactly life-threatening, so it may be something that you just accept will happen eventually.
  3. grob
    Joined: Oct 2002
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    grob www.windknife.com


    No plans to make a larger one yet, not sure how much of a market there would be for a larger one.

    I think that can be said of all glued joints, I have advised gluing anodised parts as I think that gives a good compromise of usability and performance.

    I have bonded anodised joints that have been left in damp conditions for over ten years that are still going strong.

    The best joints could be treated with Alimiprep 33 then Alucrom 1200. I don't feel comfortable recommending them to the home builder as they are expensive and unpleasant.

    Henkel have re branded their products and called them bonderite. They do a wipe (1455) and a pen (1132) for surface preparation of aluminium which maybe a little more user friendly. I think the wipes are used by auto repair shops.

    For safety critical joints I would always recommend also using mechanical fasteners as well such as rivets as well as the glue.


  4. grob
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    grob www.windknife.com

  5. revintage
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    revintage Senior Member

    Great Gareth, suppose this for hydrofoil use?
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