Auxillary pontoons for old houseboat

Discussion in 'Boat Design' started by MarkIFC, Sep 9, 2007.

  1. MarkIFC
    Joined: Jul 2007
    Posts: 12
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    Location: Ohio

    MarkIFC Junior Member

    The old houseboat I bought has had extra deck space added to the stern and a swim platform . This caused the stern to sag low. To try to remedy the issue the former owner attached 2 36" X 42" X 12" deep plastic floatation boxes using nylon tie-down straps.
    I want to tryto redo it better. My idea was 2' X 2' X 7' long pontoons made out of plywood and fiberglass tape. I calculated the current floatation boxes are supporting about 400# a piece. I'd want my new pontoons to support upto 800#.
    My question is, what minimum thickness plywood could I use? I want it to be as light weight as possible. I'd include baffles or braces. Would 1/4" fir plywood be acceptable.
    Any design recommendations would be appreciated.

    Thanks,

    Mark mark8076@msn.com
     
  2. MarkIFC
    Joined: Jul 2007
    Posts: 12
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    Location: Ohio

    MarkIFC Junior Member

    Anyone?
     
  3. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Well...2x2x7 will displace 1748 lbs each when totally immersed so each will support 874 lbs at half immersion. With 3 frames of 2x2"s and 1x2 framing at the ends supporting the plywood I would use 3/8" ply for the build. I would also glass the entire outside using epoxy and 12 oz glass cloth. This should be pretty darn bulletproof. Each is going to weigh in at about 75-90 lbs so you are in the ballpark weight wise for 50% immersion. For best results...use 9mm BS1088 marine ply...it will last a lot longer.

    Steve

    PS: It usually takes 18-48 hours to start getting replys to posts
     
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