Jet Boat Hull Dynamics

Discussion in 'Hydrodynamics and Aerodynamics' started by IDoSeaDoo, Feb 18, 2015.

  1. IDoSeaDoo
    Joined: Feb 2015
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Apex, NC

    IDoSeaDoo New Member

    Hi everyone, I'm new to this forum and it seems like just the place to get some good answers regarding my project. This year, I began upgrading my 14.5' 1997 Seadoo Challenger to run a modern 4 stroke engine. For this, I bought a 2003 Seadoo GTX jet ski to be the donor of a 1500cc supercharged 4tec motor.
    In order to achieve this, I had to cut the pump intake tunnel out and graft it into my boat's hull.
    [​IMG][/URL][/IMG]
    I have successfully epoxied the graft into the hull, but now face a dilemma with the ride plate. I decided to use the original jet ski ride plate, but because the deadrise of the two crafts was different, when the ride plate bolts up, it doesn't sit flush with the hull.
    [​IMG][/URL][/IMG]
    In this picture, you are looking from the rear of the ride plate toward the bow. The center of the hull is flush with the ride plate, but notice how on the sides, where the ride plate meets the hull,there is a step. The hull dips about .5" lower than the ride plate at it's maximum difference. This step levels out and the situation reverses. The ride plate actually forms a slight 1/8" catch below the hull line at the outer edge of the plate. I tried avoiding this and making the edge of the plate level with the hull, but somehow it came out like this.The thing I fear is that at speed, this will create a low-pressure zone in that step. Now I'm not sure if the low pressure will be enough to pull air into the pump, or if that little catch will push water into the low pressure zone, or if this will not matter at all. When I assemble this, there will be copious amounts of sealant between the ride plate and hull, especially in this crevice between the ride plate and hull. Do you guys think I'll need more than just sealant to avoid any hydrodynamic anomalies? Not sure if this matters, but the donor jet ski used to go about 58mph, and the boat went high 40's with 110hp and a smaller pump. I'm hoping to hit 55 in the boat with the motor.
     
  2. IDoSeaDoo
    Joined: Feb 2015
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Apex, NC

    IDoSeaDoo New Member

  3. IDoSeaDoo
    Joined: Feb 2015
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Apex, NC

    IDoSeaDoo New Member

    Guess nobody cares. For what it's worth, I decided to fare the height difference away with fiberglass filler.
     
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