CFD on rowing boat hulls

Discussion in 'Boat Design' started by MadMarsupial, Feb 1, 2023.

  1. MadMarsupial
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    MadMarsupial New Member

    I'm hoping someone here has some relevant experience that will help guide me.

    I am starting to design and build my own single scull. My start point has been a set of hull lines from a known designer who has given me some advice.

    A keen friend of mine who was once a rower offered to take these lines and put them into the ORCA software to try to analyise it some more. He's not a professional or trained boat designer, but he used Rhino and Orca in the design of his 'improved' canal boat that has been demonstrated to be more efficient with less engine power (and he's got decades of experience in the sailing and marine industry)

    He's admitted that his method isn't able to predict fully what the hull can do, but it can help us compare different hulls in more detail.

    He's generated some data using a Holtrop analysis. He says the rowing hulls are outside of the parameters of this method, but if we run multiple hulls through we'll get some more meaningful results. So far we have three hulls examined, but this is inadequate given the age of a couple of the designs.

    To that end I've measured up a few more modern boats and I'm drafting them up for him to test.

    So...has anyone here looked at rowing boat hulls? Can you offer any suggestions for different or improved virtual testing methods with the tools we have?

    Once I've confirmed the hull shape I'll start to work on a Cedar strip prototype boat for on water testing. I'm hoping to work up to building a couple of boats in other construction methods later.
  2. wet feet
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    wet feet Senior Member

    A few years ago a very clever fellow called Leo Lasauskas often posted here.He developed a program called Michlet for precisely this purpose,unfortunately both he and the program don't show up any more.
  3. Squidly-Diddly
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    Squidly-Diddly Senior Member

    do the tests account for heavy weight of rower shifting in a light boat, and the several pulsing inputs of the oars on power and recovery strokes, that match the weight shifting?

    Do top tier rowers time or coordinate their stokes to some perfect rhythm that synchs with wave length like you can supposedly with with butterfly stroke?

    I'm thinking doing hard science study of all that would be NASA NSA tier engineering. I've also heard that no one has ever been able to get a handle on what makes birds fly as far as being able build a computer simulation that can be tweaked to study.
  4. mc_rash
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    mc_rash Senior Member

  5. mc_rash
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    mc_rash Senior Member

    As @Squidly-Diddly said, a detailed, "realistic" analysis with weight shifting and stroke rhythm would be somewhat overrated, in any case for a homebuild rowing boat. Probably a 'simple' resistance evaluation of different hulls and some optimisation would be sufficient.
  6. MadMarsupial
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    MadMarsupial New Member

    I remember Leo from - I think - University of Adelaide. He designed some very fast but unrowable hulls to prove various theories. And he came up with something clever for the Navy to help multiple ships sail together in formation to eliminate wash to one side.
  7. MadMarsupial
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    MadMarsupial New Member

    It's going to be a racing single scull with possible aspirations for going on sale, so I want to do my best!
  8. DCockey
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    DCockey Senior Member

    The Holtrop analysis used in Orca is not CFD - Computational Fluid Mechanics. Unlike CFD the Holtrop method does not solve any 3D equations and predict the flow around a hull. Instead the Holtrop method is based on regression and interpolation, and uses various parameters as the input with resistance and related coefficients as the output. Orca has an available CFD analysis using the Simerics-MP which does a numerical solution of the Navier Stokes equations with a turbulence model for the flow around a hull.
  9. MadMarsupial
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    MadMarsupial New Member

    Thank you.
    I hadn't known the detail about the method. I'll ask my friend if he has access the Simerics-MP CFD tool.
  10. Alan Cattelliot
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    Alan Cattelliot Senior Member

    Unstationnary CFD analysis should be done, for the hull to be optimized. Regression-based tools or stationnary CFD results can always be compared to one another, but won't take into account the beat stroke of rowing boats and the specific hull's movement. Some specific software do exist, but as any tools, they all require also a specific expertise, for their results to be critizised.

    Commercial CFD tools always give colored result, but, unless you have a true expertise in CFD, you cannot know if the results are consistent. Truly speaking, their is not much "true" CFD analysis that has been made on rowing boats.

    Budget for such detailed studies is, in general, beyond what is traditionnaly spend in hull optimization, done by naval architects themselves, and mostly based on their true experience. I am aware that builders sometimes communicate about CFD studies, but this is often more a commercial speech. Everybody can make CFD today, but not everybody is able to make CFD usefull.

    In your case, unstationnary CFD is mandatory, if your will to to improve the hull.
    Last edited: Feb 3, 2023
  11. BlueBell
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    BlueBell . . . _ _ _ . . . _ _ _

    I have rowed competitively, designed and built many human powered boats, competitively.
    You are splitting hairs, there's no way the margins of error will allow for any meaningful test analysis.
    Unless you're just in this for the academics, you'd be miles ahead to simply build to a proven design that meets your needs.
    And you'd be even further ahead to buy a rowing shell, even used for cost reduction.
    You'll see more performance increase from training than from trying to design a better, faster boat.

    So, there it is, some relevant experience that is meant to guide you, as requested.
    Good luck.

  12. gonzo
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    gonzo Senior Member

    I used to row too. The shells are designed for different crew weights and weather conditions, so there is not design that is better. If this project is to manufacture shells you should decide if you want to focus on only one type, like a single, or have whole range of shells. Each type, in turn, should have at least a three or four models.
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