aluminum for compression post

Discussion in 'Boatbuilding' started by robwilk37, Jul 1, 2012.

  1. robwilk37
    Joined: Nov 2010
    Posts: 120
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    Location: san diego

    robwilk37 Senior Member

    I came across a 5" x 5" x 16' tube of 6061 T6 aluminum in the scratch and dent bin at the local metal supply shop. Square section quarter inch wall thickness. I'm considering 2 lengths through-bolted to the main bulkhead (1" marine fir plywood) as compression post on my deck-stepped yorktown 39 rebuild project.

    I'm curious to know if 6061 would be the preferred alloy, keeping in mind the compression post's step on the keel will be above the level of the bilge and therefore never in standing bilge water. I like the square section tubing because it allows a chase way for mast wiring and a lightning conductor to the keel where I can connect to an external grounding plate.

    Any constructive comments would be greatly appreciated. Thanks!
  2. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Just prep the AL, and prep with zinc chromate and paint properly. But isolation grease on stainless hardware attached to AL. T6 stronger that marine aluminum but not as corrosion resistance. Avoid welding it, it will lose t6
  3. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Have you calculated what loads the post shall experience, and what is the length of the post? These are you main drivers and shall dictate the selection and scantlings of your material. As you should be more concerned about the actual loads rather than the material choice.

    You also need to isolate the ally from the plywood. In a void you'll get condensation etc and this will lead to poultice corrosion between the wood and the ally.
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