Rowing Boat Hull Designs

Discussion in 'Hydrodynamics and Aerodynamics' started by Jhomer, Feb 8, 2022.

  1. Jhomer
    Joined: Jan 2010
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    Location: Adirondacks, NY

    Jhomer Boat Builder

    A general question in reference to hull design for rowing a fixed seat boat....
    I am building a Adirondack guideboat for racing although the boats themselves are noted as being a very fast craft. In my studies and research I have seen older boats with a wider shape in the bow and tapering off to the stern called cod headed. It has been said these type of boats were slightly faster. Is anyone here familiar with this concept? Wanted to see what the consensus was before putting in 350 hours to build this boat. Thanks in advance.

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  2. rangebowdrie
    Joined: Nov 2009
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    Location: Oregon

    rangebowdrie Senior Member

    In the days before engines the "Cods head/Mackerel tail" was a popular design element for both muscle and wind power, which had low drag at low speed/length ratios.
    For rowing, having a narrow beam meant easier control over the oars, whilst the fisherman wanted more room to spread out all his gear/paraphernalia.
    The guideboat as you referenced provided a narrow easily driven/low drag stern shape whilst providing space and buoyancy for the "paying cargo", so to speak.
    The boats would "glide up" to a likely spot where the fisherman could cast ahead of the boat.
    In areas where the fishing was more suited to trolling, rather than casting, the boats developed with wider stern sections, (where the fisherman tended his gear).
    Of course, as soon as engines became popular the stern sections had to be widened to prevent squatting.
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you are racing, that implies there are other boats of that design in your area. Look at the winning designs; those are the fast ones. The original boats where for carrying cargo, and I am sure the racing designs are considerably different.
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  4. Steve Clark
    Joined: Jul 2004
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    Location: Narragansett Bay RI

    Steve Clark Charged Particle

    The boats with "fuller lines in the bow" have most of the fullness above the waterline. For example John Gardner's modification of LFH's 17' pulling boat increased the fullness and flare forward to help the boat rise into a chop thus stay drier. This is a compromise of performance for sea keeping. Similarly the Guide Boat is very fine at the waterline with lots of flare to keep the waves out, and has proven to be a more successful blend of performance and seaworthiness than many anticipated. I think that a great deal of their success is due to the fact that they are generically lighter than most of the boats the race against.
    Those with better NA chops than I have, say that if you are targeting Froude Numbers above about 1 you should be looking to have a Prismatic Coefficient above .6 which I think is higher than a guide boat. A 17'wl boat has a hull speed of 5.3 knots which seems like a pretty fast pace, but also suggest that there is little need for a one man boat to be any longer than that. Minimizing wetted surface is also very important, but if you go too far down that road you can end up where I did with the one effort I made and discover you have a very twitchy boat that seems a unstable as a racing shell with great big flared topsides to violently chuck it around. The first time I rowed it in the Snow Row, I thought I was going to die. The not so dumb guys who built several hundred prototypes refining the Guide Boat looked very clever by comparison.
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  5. waterbear
    Joined: Mar 2016
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    Location: Earth

    waterbear Senior Member

    You can always draw your hull in freeship, then export to michlet to get the drag data. This sounds hard but it is actually quite simple. You could then compare your results to flomo's data on various hulls.

    See link below for flomo's site. under boat design studies there is a spreadsheet called resistance and stability. I believe there is some data on a guide boat or two, as well as sulkava rowboats and many of flo-mo's own designs.
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