Boat Hull Design Help

Discussion in 'Boat Design' started by Jacob Beckley, Nov 19, 2018.

  1. Jacob Beckley
    Joined: Jul 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Chicago, IL

    Jacob Beckley Junior Member

    I am designing and building a boat that I'll use to tandem row for charity. The boat is is a hybrid between a traditional ocean rower and an expedition type rower. The boat will be constructed of plywood and fiberglass. This is not the first boat I have built, but it is the first I have designed.

    Up to this point, I started with ProChine to define the hull and then exported that to Rhino3D to continue with the rest of the design. I am happy with the aesthetics of the boat and the overall look of it, but I am worried about the hydrostatics and overall performance and balance. I have no idea where the waterline will lie, nor if the boat will have the proper balance.

    These are the dimensions I used as the hull base.

    Length of Waterline 23
    Bow Oberhang .5
    Stern Overhang .25
    Distance to Amidship 11
    Draft .85
    Steer Height at Bow 2
    Steer Height at Amidship 1.25
    Steer Height at Stern 1.5
    Beam at Bow 0
    Beam at Amidship 5
    Beam at Stern 2​
    I am looking for lots of advice, or better yet, a kind soul who would be willing to help with my cause. Attached is the current model of the boat.

    Thanks,
    Jake


    Screen Shot 2018-11-19 at 12.58.20 PM.png
     
  2. DCockey
    Joined: Oct 2009
    Posts: 4,036
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    Location: Midcoast Maine

    DCockey Senior Member

    Basic principles:
    Weight of water displaced by the boat = weight of boat (when the boat is at rest or moving slowly) (Archimedes principle)
    Weight of water displaced = Volume of water displaced x density of water
    Center of gravity of the boat will be directly above (or below) the centroid of the volume of water displaced by the boat.
    Rhino has Hydrostatics command which calculates displace volume, centroids and other useful quantities.

    Send me a personal message if you'd like me to look at your design in Rhino.
     
  3. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Well, now that you have drawn your design, now you need to prove it'll work, in principle.

    To do that, you'll have to work out/estimate the the structure and the weight of the structure.
    Then add on the remaining outfitting and then the rowers of course.
    Sum all that up along with the relative LCG's and VCG's....then and only then, can you answer this question.
     
  4. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    Since the shape of the hull is given, the displacement and the location of the COG are the next steps - as Ad Hoc says. Before knowing that you are only able to calculate some COB's depending on the respectively assumed waterline. Furthermore assuming the boat will swimm level, not knowing if it will be the case.

    Edit: My post was mainly an answer to an objection post, which a day later disappeared.
     
    Last edited: Nov 23, 2018
  5. TANSL
    Joined: Sep 2011
    Posts: 5,349
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    Location: Spain

    TANSL Senior Member

    @Heimfried, the post that disappeared was mine and I made it disappear because it did not contribute anything to this thread.
    @Jacob Beckley, I attach some sketch of the changes that I would make in your latest design.
     

    Attached Files:


  6. Jacob Beckley
    Joined: Jul 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Chicago, IL

    Jacob Beckley Junior Member

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