20ft Nemesis Cat

Discussion in 'Boat Design' started by Alexander Peter Bromley, Feb 24, 2021.

  1. BlueBell
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    BlueBell . . . . .

    So what if your tunnel sits in water at rest if it won't when making way.
    Not sure what the penalty is there.
     
  2. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    Hi Blue Bell, so the aim to keep the tunnel clearance high out the water should theoretically prove to be a softer riding boat whether trolling speed or on the plane.

    If the tunnel is out the water at rest it will only get higher out the water once on the plane. If the chop is less than the tunnel height the ride in that sea state should be very soft.
     
  3. BlueBell
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    BlueBell . . . . .

    So, that's more about sea state not your tunnel being submerged at rest.
    Okay, that makes more sense, thanks.
     
  4. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    3D Printed Scale model 1:18.
     

    Attached Files:

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  5. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    Some progress on the build.

    Screenshot (83).png Screenshot (82).png Screenshot (85).png Screenshot (84).png
     
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  6. bajansailor
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    bajansailor Marine Surveyor

    Thanks for the update Alex.
    On your first page you mentioned a plug - will you be taking a female mould off the plug for series production of this boat, or is she going to be a 'one off'?
    Sorry, this has probably been mentioned somewhere in the last 6 pages, but I haven't gone back through all of them.
     
  7. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    @bajansailor Hi, yes we will produce a female mould and then use it for production of these boats.

    Today some more progress was made... Screenshot (93).png Screenshot (91).png Screenshot (94).png Screenshot (91).png
     
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  8. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    So I know you can't deduce too much from a towing test such as this but it gives a rough look and feel to how the boat will run. Just skip the slow parts between runs.

     
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  9. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    Another.

     
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  10. BlueBell
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    BlueBell . . . . .

    Get yourself a stick and lower the thrust angle of your tow line.
    Unless this is the kitepower option you're testing.
    You're picking up the bow considerably in these videos.
     
  11. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    Hi @BlueBell thanks I will try it with a stick.
     
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  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Seeing you are going ahead straight to a mould, what purpose is served by towing scale models ?
     
  13. Alexander Peter Bromley
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    Alexander Peter Bromley Student Naval Architect

    Curiosity, anticipation, any odd behavior form the model that might be a cause of concern, further the need for plug or mould adjustments and comparison between how the scale model behaves compared to the full size boat with the resources available, for future designs prediction accuracy.
     
  14. Jimboat
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    Jimboat Senior Member

    Nice project!
     

  15. Alexander Peter Bromley
    Joined: Apr 2020
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    Alexander Peter Bromley Student Naval Architect

    Thanks Jim! I see in your bio you have a book called the secrets of tunnel Boat Design is that yours?
     
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