Extended Hull for jet drive

Discussion in 'Boat Design' started by drev500, Jul 22, 2015.

  1. drev500
    Joined: Jul 2015
    Posts: 6
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    Location: Ohio

    drev500 Junior Member

    Hey y'all,

    This may be too long but I want to explain my project :)

    I am in the process of doing some research for a Senior Design project at my college. I am entering my senior year studying Mechanical Engineering and I proposed an idea of repowering an old Starcraft Supersport or something similar with a jet pump. With the amount of rain we have received this summer in Ohio, the Ohio River has seen a higher than normal water level causing lots of drift to come down river. I grew up on Lake Erie so I am not used to river boating. Hanging out at a friend's river house over the Independence Weekend opened my eyes up to how much drift was coming down stream and how it affected boaters. My buddy being one of them did not want to run the risk of damaging his stern drive so he opted to stay on land.

    I got to thinking that an aluminum hulled jet boat would solve this issue. If I had the welding skills and money I would buy aluminum and weld a nice, thick hull together. This is where the Starcraft comes into play. Although they are riveted, I was thinking of using Gluvit or maybe some kind of truck bed liner like Line-X (which does flex) to coat the seams and inside the hull to prevent leaks and cover ones that may be existing.

    Currently I do not have a hull in my possession as I am waiting for approval form the engineering committee but I wanted to get a head start on research. A jon boat comes to mind for a project like this but I want something that can also handle better than a flat hull boat so I opted for the Starcraft which has a Semi V hull (If you would call it that) at the transom. For cost reasons, I was going to use a jet ski driveline and have one in mind/onhold (WaveRaider 1100). The jetski is a 1100cc 2 stroke with a trimmable jet nozzle. I was going to modify the nozzle to also accept a reverse bucket. I would like to use a Berkeley or Hamilton pump but cost is keeping me away and jetskis/jet ski parts are easily obtainable.

    The only issue with the jetski drive is form the pictures, it seems very long. I would estimate with the pump and engine together, it is 5 feet long. I want to make this boat as efficient as possible (fuel and space). Jet drives already don't have the best fuel efficiency so as an engineer I want to try squeezing all I can out of it.

    Obviously having the least amount of "wet" surface will help with efficiency. Having a trimmable nozzle will help get as much hull out of the water but if too much of the lower side is showing and air gets under there, the pump will start drawing air...making forward propulsion null until water draws again.

    I tried search but could only find examples on prop boats with an offshore bracket/ flotation bracket/ extended hull. Since the drive train is so long, I was hoping that extending the jet drive as far back would help with CG by shifting it back more and keeping as little hull in the water but also feeding the pump with water (neglecting rough water since this will see a calm river). Would an extended hull work on a jet boat? I think that it would help with porpoising so increase the stability while also aiding in planing.

    I thought that getting a 16' Starcraft and adding a foot or so on the back of the hull would be great but then thought why I shouldn't just buy an 18'. This would keep me from having to add aluminum on the hull and just make a false transom 2 feet forward and place the pump on the original transom.

    Am I thinking crazy? I have only been doing a few weeks of research so I hope I don't sound ignorant.

    So my two questions: Extended hull/offshore bracket for jet drive? Should I get a 16' and add on or get a 18' and make a false transom at 16'?

    Hope I didn't kill you with all the typing :D
     
  2. drev500
    Joined: Jul 2015
    Posts: 6
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Ohio

    drev500 Junior Member

    I realized I didn't include a picture of what I was thinking. Here is a picture of a Blackhawk with what the call an offshore bracket. It sits the outboard further back. I was thinking of doing something similar but with an inboard jet drive. Also, the jet drive will not be that far back, maybe half that?
     

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