Questions about a pontoon boat build.

Discussion in 'Boat Design' started by steelheadseeker, Mar 22, 2012.

  1. steelheadseeker
    Joined: Mar 2012
    Posts: 1
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    Location: Washington

    steelheadseeker New Member

    Hey Im a brand new member. Ive been interested in building a person pontoon boat for some time now. Im finally going to get after it. Heres my plan, Id love to have any input

    Im starting with 5, 4 x 8, 2 inch thick insulation foam (the pink or blue stuff) from hardware store cutting directly in half. With the two sections I want to glue two 8 inch 1/4 inch strips of plywood ever other stack in the edges for strength.. glue and press together. now I will have to two 2x8 logs. In the center of the each block. Im going to carve out a spot for a 2x4 to run and attach my lags for the frame connection. im going to add fiberglass mesh in this channel or a heavy glue. for locking it in. I am going to be fiberglassing the whole thing at the end.

    Heres a few of my questions.

    Will this foam work? bouyant enough? What shape should I use on the front of the pontoon? I was thinking 30 degree on each end, sort of similar to a jon boat and easy to carve out. Or do I go for the pointy coneish style? Id like best hydrodynamics or whatever its called lol. so I can power it easy with electric motor.

    Any Ideas or answers would be awesome. Thanks and happy building !
  2. messabout
    Joined: Jan 2006
    Posts: 3,106
    Likes: 273, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Your method of construction is not entirely clear. It sounds like you are building a foam five decker sandwich. Five bread slices (foam) and four meat slices (ply). You'll have two box like structure that measure 24 x 11 x 96. Each of them will displace about 5.3 cubic feet and support about 915 pounds less its own weight.......maybe 50 or 60 pounds for a net flotation of...915-60= 850 pounds Two pontoons then will support 1700 pounds.

    Let us suppose that the boat will weigh 125, the battery and motor about 65, and the skipper and his fishing gear, about 200 pounds. Total weight of a little less than 400 pounds. You will have plenty of reserve bouyancy. That will not make this a safe boat. You should not use such a flivver in rough water. Calm streams or ponds O.K. Sobriety will also be a desireable condition of use.

    Foam construction will be more trouble and aggragavation than you need to endure. If the foam is of the styrene type you will not be able to use polyester resin for the glasswork. Polyester will melt the foam into a gooey mess. You'd have to use epoxy resin which is much more expensive.

    Do this project the easy, cheaper, faster, lighter, way. Three sheets of plywood will make two boxes 16" x 16" x 96". Each box will support about 850 pounds less their own weight, for a net flotatoion potential of about 800 pounds. Each ponton will draw about 4 inches of water when fully loaded as above.

    It will be an advantage to taper the bottoms of the floats/pontoons at the ends. Measure back from the ends about 18 inches. Measure up the sides at the ends about 6 or 7 inches so that you have a triangular shape on the sides. Remove that section and you have a rocking chair like profile. The electric motor will like that arrangement better than a blunt ended box. The boat in motion will splash a little less too. When you do that, the bottom closure will be about 19 inches long. SO you will need to make the boat length 94 inches rather than 96 inches. That is unless you are willing to buy the fourth sheet of ply.
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