Constructing a personal watercraft/ jet ski

Discussion in 'Boatbuilding' started by MountainRunner, May 17, 2015.

  1. MountainRunner
    Joined: May 2015
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    Location: United Kingdom

    MountainRunner New Member

    I'm totally new to boat building. I have for some time wanted to build my own 2 person personal watercraft. I need some advice on the materials I need for the hull and the pros and cons of using a rear mounted outboard as opposed to a centre mounted inboard engine.

    4 materials I have considered for hull construction are:

    Fibre glass/composite
    Marine ply
    Mild steel of about 21 gauge galvanised

    The steel seems the cheapest and easiest option, is it a viable material to use so long as it's well primed and protected against corrosion? The water craft will be kept at home out of the water when not used.

    If not is composite expensive?

    Have you any other information on how to build a jet ski and maybe other posts from people who have done this?
    Last edited: May 17, 2015
  2. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    If you mean a personal watercraft in the same sense as the industry (Kawasaki Jet ski, Seadoo, Waverunner, etc) You would be far better off just buying one. Building your own would more than likely cost you far more.

    Materials. Fiberglass. I suppose you could build one of plywood but it would still be heavier than FRP. Steel would be very heavy.

    Using an outboard is dangerous on a craft that you are bound to fall off of. One of the reasons for powering PWCs with jets is to get rid of the propeller. Back in the early 80's people were building what were then called "thrill Craft" but they were essential personal watercraft and they tried making them with outboards. It was not a good combination. When the newer ones started being built by Kawasaki, Bombardier, Honda etc they all had jets. The jets were lighter, faster and safer, and they would roll over and keep on running. People could fall off, climb back on and motor away without worrying about getting cut up. The only practical way to get back on one of these in the water is from the back. Hard to do with an outboard hanging there.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    If your asking these questions, you're looking to design, then build a two place PWC, is this correct? I'd strongly advise against this, unless you have a solid grasp on the hydrodynamics, physics and engineering involved. Again, since you're asking these questions, it suggests you don't have these skills, as any budding designer would already have material preferences nailed down, while the design was still in the concept stage. Steel isn't a reasonable material in this type of craft, in fact, a bit silly to consider. Your other three choices listed shows wood and plywood, again suggesting a lack of some understanding about how things are approached, from an engineering stand point.

    Do yourself a big favor and buy a set of plans. Stick to the plans, it's BOM and scantling schedules and you'll likely produce a boat you can be proud of and one that performs as expected.
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