rudder shelf

Discussion in 'Boat Design' started by Eric Poche, Jul 21, 2008.

  1. Eric Poche
    Joined: Oct 2007
    Posts: 2
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    Location: Louisiana

    Eric Poche New Member

    Hi too all this is my first post. I purchased a 28' Bertram and in reading different web sites the rudder shelf on a Bert was known to rot they are made with plywood. While inspecting the boat before purchasing I found they were rotten unknow to the owner which help me with bargining power. I am replaceing them with aluminun plate. What I need to know I am using hot dipped galvinize bolts to attach the plate to the fiberglass stringer and stainless steel bolts to attach the plates to each other. Where the galvinize bolts passing thru the stringer there is a copper bonding strip. I am I making a mix of metals that will give me a corrosion problem, or with the bonding will help to prevent it . Any help is appreicated.
    Thanks
     
  2. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Eric, just use stainless steel bolts for the whole job, they are galvanically bonded as you say.

    A decent plywood plate is quite OK too, unless you have already made the alloy plate. 1" plywood with glas over both sides is very strong, certainly good up to nearly 40 feet, so the berty will not suffer, and it is much cheaper and easier to do it that way. Lay the glass onto a piecs of window glass, wet out and attach the plywood, cover with plastic and add a few batteries or bricks to squash it down, then when set turn over and do it again, this will give two very well sealed surfaces to work from.
     
  3. diwebb
    Joined: Jun 2008
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    Location: New Zealand

    diwebb Senior Member

    Eric,
    what you are suggesting would certainly create a problem. As Landlubber has said go with the ply and stainless bolts. Make shure they are 316 stainless, more expensive but much less prone to crevice corrosion. All the best with the repairs.
    David
     
  4. Eric Poche
    Joined: Oct 2007
    Posts: 2
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    Location: Louisiana

    Eric Poche New Member

    thanks to you all I will go with all stainless bolts, and I already have the aluminum plates cut and fitted
    Thanks again
    Eric
     
  5. lazeyjack

    lazeyjack Guest

    find LANACOTE it is a natural wool based grease , it will stop corrosion, , and for instance if you tap alloy and then scew in, with lanacote it will always unscrew
    You can always drill oversize and sleeve with nylon bushes and washers , to make a total isolation ,you know this is what we do on our alloy yachts
    of coarse they are not up with the play is Aust:)) they still use a product called, um er , yellow , but it hardens and is useless long term
    i have heard it called COCKATOO SNOT, by the illiterates!
     

  6. Landlubber
    Joined: Jun 2007
    Posts: 2,640
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    Location: Brisbane

    Landlubber Senior Member

    Duratec...cocky **** mate
     
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