Jet boat designer needed

Discussion in 'Boat Design' started by Sid, Oct 24, 2020.

  1. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

    Hi everyone

    I'm looking to hire a designer to design a 18 ft. aluminum boat for comfortable and safe family cruises over shallow rivers. The boat will be powered by a 80HP outboard jet that I own.

    I'd appreciate your advice on whom I should reach out to.

    Kind regards,

    Sid
     
  2. Squidly-Diddly
    Joined: Sep 2007
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    Location: SF bay

    Squidly-Diddly Senior Member

    what's your budget?
    Unless you got a specific "picture in mind" that you aren't sharing, I can't imagine doing better with Home Made than an American factory made proven setup as shown, even if it costs an extra $5000 to ship. "Offshore" high bow and lots of sturdy grab rails for comfort and safety. Good match to your engine HP and maybe a spare motor or TWO (and trailer!) in the bargain.
    https://sfbay.craigslist.org/nby/boa/d/sebastopol-klamath-offshore-aluminum/7218989032.html

    Rent 20' Shipping Container and stuff boat into container (even if need to cut trailer tongue to fit, easy to re-weld) and stuff the container full of other stuff that is cheap in SF Bay Area.
    https://sfbay.craigslist.org/eby/boa/d/walnut-creek-canoe-for-sale/7217248373.html
    https://sfbay.craigslist.org/d/free-stuff/search/zip

    recent arrival Polish acquaintances in SF Bay Area seemed amazed that so much perfectly good often high quality stuff was being given away for free in USA.
     
  3. ondarvr
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    ondarvr Senior Member

    Is the motor 80hp at pump or powerhead?
     
  4. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

    Thunderjet's Rush 186 (Heavy Gauge Aluminum Fishing Boats - Thunder Jet 186 Rush https://www.thunderjet.com/boat/186-rush/) is more or less what I'm thinking of. Having such boat built by local shop wouldn't cost significantly more than the shipping costs, not to mention import tariffs and taxes.


    The motor has been jet originally, so I believe it's 80HP as marketed.
     
  5. mudsailor
    Joined: Mar 2013
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    mudsailor Junior Member

    Sid likes this.
  6. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

  7. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    You probably need no more than a 12 degree vee, for a river boat that will allow shallower draft, plus the usual jet requirement, a shallow, well raked forefoot.
     
    Sid likes this.
  8. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

    @Mr Efficiency, is it something you could help me with? If so, how could I contact you?
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    What are you proposing to do, construct it from panels cut using CAD files ? That's not something I can supply.
     
  10. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

    CAD files can be prepared by the aluminum shop. They need a detailed boat plan with exact dimensions. Would that be feasible?
     
  11. Barry
    Joined: Mar 2002
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    Barry Senior Member

    Any time you have to hire someone to build files from drawings, it is going to cost you a bunch of money. I would send Metal Boat Kits an email with your requirements. Their website is pretty good but you have to hunt around for the specifications. They have many boats in the 16 - 20 foot range that should meet your goals. Their CNC files can run from $300 to $900 which will be cheaper than building a male jig or having someone try to build a set of DXF files from
    a set of plans. I believe that they will provide a US Hull Identification Number, not sure what the validity is in Poland. You should check to see about regulations for a home built as well as what your insurance company might require
    to insure it.

    Some things to note.

    1) Beam- In an 18 foot boat you want to have quite a bit of beam especially if you are considering installing a tunnel in front of the jet. Ie a narrow beam boat with a 2 foot tunnel will normally ride nose up when unladen. I would try to get the
    chine width ( not boat beam) close to 6 - 6 1/2 feet.

    2) Length- In North America, quite a few of the boat manufacturers have taken liberties with boat length. One medium sized manufacturer introduced a new 32 foot model of boat this year, same length hull as a 30 foot, but merely extended the
    swim grid another 2 feet. Ie bigger numbers for the brochure, same inside length. So when you look at the Metal Boat Kit site, you really need to be aware of this. Many outboard boats are going to swim grids that are integral
    to the bottom of the hull but the actual dividing structure where the engine is mounted is moved forward which reduces inside usable space. MBK (Metal Boat kits) has a 16' with normal transom that appears to have about the same inside space as a 19.5'due with pod/hull extension due to this measuring method. Just be aware. Two 18 foot boats, one narrow with the extended "hull/pods" and the other with standard transom and wide can offer a major difference in usable space

    3) Deadrise- Mr E is spot on with a 12 degree deadrise. Without an engine leg in the water a jet will skid out in a tight turn and can even swap ends. Google Shotover Jet Boat Rides, New Zealand for 360 degree victory rolls.
    Albeit inboards, but you get my drift. To compensate for the skid, I would incorporate 4 lift strakes, turned down as an add on to reduce this effect. Twelve degrees will be rough in waves over 1 1/2 feet at higher planing speeds but one of your requirements was "shallow rivers". Two will be the reverse chine and two will be placed further inboard toward the keel. If you get to actually build it, I can dig out some dimensions for you.

    4) Tunnel- We have built outboard jets from 4 degrees to 12 degree deadrise and they all drift and tunnels introduce issues. The shallower the V the more drift. The problem is that when the boat is drifting in a tight turn the tunnel under the right conditions can/ will ventilate and rob the intake of water. Without a tunnel, and you may only add 6 inches of draft, ie leave the intake below the boat. So when you say "shallow rivers", what depth are you wanting to run
    your boat in. The tunnel does protect the intake to some extent in many cases and does permit a little shallower water running. If all of your rivers are free of rocks and the "shallow water" that you want to run is say 12 inches
    you can easily leave the tunnel out of the mix. Note that the ventilation issue is with tight turns. In our area, rock gardens are prevalent, and rock avoidance tight turns a real concern

    5) Welding- Use Mig, aluminum alloy 5086H116, ( you could use 5052H32) if you actually get to the build process PM me and I can offer some more direction to welding and grinding methods.
    Also as you intend to run shallow water and be susceptible to hitting things, the inside stringer strength should be addressed/ increased
     
    Last edited: Oct 25, 2020
    bajansailor and Sid like this.
  12. Sid
    Joined: Oct 2020
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    Location: Poland

    Sid Junior Member

    Thank you @Barry for your insightful comments. The rivers I intend to build the boat for are shallow here and there. They are irregular, meandering with frequent sandbanks, submerged obstacles and rather less frequent rocks. They rarely get shallower than 12 inches over full river breadth.

    PMed you with a follow-up.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

  14. Barry
    Joined: Mar 2002
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    Barry Senior Member


  15. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I'd be happy enough with 5'6 for a river boat, the effective waterline beam at rest would be more like 5'9, that's adequate with a low deadrise boat. And it is using outboard, not a much heavier inboard jet. I don't think he'll find much else, unless you have an alternate suggestion ?
     
    Last edited: Oct 27, 2020
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