Rebuilding a Riva

Discussion in 'Wooden Boat Building and Restoration' started by johnnythefish, Jan 28, 2022.

  1. johnnythefish
    Joined: May 2016
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    johnnythefish Junior Member

    A friend is restoring this Riva run about. He has taken all the rotten plywood out and also the rotten ribs and replaced them.


    He says there was a funny sort of waxy canvas between two layers of plywood (which I believe was planked diagonally at 90 degrees to each other)…


    He is asking for some advice on the rebuild …


    As it is almost a completer rebuild I am inclined to suggest that he use epoxy and encapsulate all the ribs and “cold mold” all the strips and then sheath the outside at the water line with biaxial…


    But I don’t know enough about whether this would be possible/ compatible with what is left or whether he should copy the original system of fasteners, waxy canvas etc…


    I don’t think he is looking for it to be restored as original necessarily…


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    fallguy likes this.
  2. fallguy
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    fallguy Senior Member

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  3. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Epoxy encapsulation is rarely a bad idea.
    Trying to glue laminations together with wax is rarely a good idea.

    Use Epoxy!
     
  4. fallguy
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    fallguy Senior Member

    wasn't wax-the waxy substance was painted canvas most likely; as was typically used between layers of planking

    my expertise is very limited here
     
  5. Blueknarr
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    Blueknarr Senior Member

    This is the first time I've heard of wax. Often tar between or painted canvas over tar.

    Could be an uncurred resin that feels like wax.
     
  6. fallguy
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    fallguy Senior Member

    Painted canvas might seem waxy to someone?
     
  7. Rumars
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    Rumars Senior Member

    Doped canvas between two layers of diagonal planking, mechanically fastened, was used commercially until the end of the wooden boat era. The dope was usually white lead, applied as a thick paste, the fasteners screws or ring nails. Depending on the exact dope formulation today it can appear as anything between a rubbery paste up to crumbly chalky solid.
    Beside replicating the original construction (white lead is unobtainium in some places) there are two ways of replacing the bottom. One is to cold mold the skin with epoxy and glue or screw it to the frames and stringers. The other is a so called "5200 bottom" where the original doped canvas is replaced by a thick layer of 3M 5200 as a sealant. This method mandates screws or nails, the skin is not glued to the framing.
    Fiberglassing the bottom is entirely optional as long as the skin thickness is maintained.

    Rivas from the golden age of Carlo Riva don't use doped canvas, the bottom and sides were hot molded, the sides always in one piece, the bottom in several pieces with different number layers and scarfed together. But, the firm begun building speedboats in the 1920's, so it's possible this is an early boat, before Carlo took over and begun using hot molding techniques.
     
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  8. johnnythefish
    Joined: May 2016
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    johnnythefish Junior Member

    Thank you for this fascinating insight
     
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