Optimum waterline length for performance rowing skiff

Discussion in 'Boat Design' started by SailorDon, Dec 15, 2016.

  1. SailorDon
    Joined: Apr 2013
    Posts: 137
    Likes: 4, Points: 0, Legacy Rep: 34
    Location: Livingston, TX

    SailorDon Senior Member

    There are not many commercially produced performance rowing skiff designs to choose from. There is the Heritage 12, 15, and 18 series, the Tango 17, Solo 14 and Skua 16, to name a few.

    My question is, for this classification of rowing skiffs, what is the optimum waterline length for performance rowing.
    Assume boat weight about 100 pounds.
    Assume oarsman and cargo weight about 250 pounds.

    From personal experience, I am guessing the optimum waterline length to be about 16 to 19 feet.

    When rowing a 17' skiff, I find that at 4.5 mph, the wave making resistance builds exponentially and a reasonable cruising speed is 4.0 mph.

    When rowing a 18' skiff, I find that at 5.0 mph, the wave making resistance builds exponentially and a reasonable cruising speed is 4.5 mph.

    I have not had the opportunity to row anything longer than 18'.

    I'm guessing that at some waterline length exceeding 18', the extra drag due to skin friction will outweigh the advantage of reduced wave making resistance.
    I wonder if that would be 19' or 20'. Any longer than that, and the rowing skiff becomes "unmanageable" for a person to handle by themselves. Weight and windage would become a problem.

    This Heritage 18 is my current rowing skiff:
    [​IMG]
     
  2. JosephT
    Joined: Jun 2009
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    Location: Roaring Forties

    JosephT Senior Member

    That's a nice boat SailorDon. The definition of performance will depend on the individual rower's environment and personal preferences. For example, a paddler in calmer waters may feel comfortable in a longer, narrower skiff that can achieve cruise speeds in calmer waters and achieve 6+ mph. On the other hand, rower in choppy waters requires a wider, more stable skiff so you sacrifice some speed there.

    So, it really depends on [where] you will row the skiff and how much you enjoy waves. I personally enjoy both and would probably settle for a boat around 18-21ft with a moderately narrow waterline that offers decent speed and enough stability to come out on top if you decide to paddle through some chop.

    If you go longer, generally you want to go narrower too if it's speed you're after. A 21ft boat can weigh the same as a 17ft boat if you apply this logic. If you want to maintain waterline width (beam) then going longer will make your boat heavier and slower too.

    Ben Booth designed & built a high performance rowing skiff that takes things to a new level. Notice a few key features that allow it to dominate:

    1. Narrow waterline = fast speed
    2. Decent length (18ft)
    3. Bow & stern decks (deflect water, improve buoyancy in waves.

    Looks like a nice bomb proof design and a fun boat to me!

    http://www.boatdesign.net/forums/boat-design/designing-fast-rowboat-14250-117.html
     
  3. SailorDon
    Joined: Apr 2013
    Posts: 137
    Likes: 4, Points: 0, Legacy Rep: 34
    Location: Livingston, TX

    SailorDon Senior Member

    I read the Ben Booth posts on designing a fast rowboat. He certainly found the optimum design for his purpose, which was to win the fixed seat single class in the Blackburn Challenge. 30 spm for 20 miles! WOW! I'm guessing that he is not a member of the geriatric set as I am. It almost gives me a heart attack just reading about it. :D

    Ben's design is based on circular sections which makes it less stable.
    Not as tippy as a racing shell, but it might require keeping both oars in the water to keep from capsizing. I think my Heritage 18 is more stable.
    The manufacturer's website shows a guy standing up fishing from his Heritage 18.
    Here is a pic of my boat. It is not a very good angle for viewing the profile of the sections below the waterline, but it is definitely not round.
    [​IMG]

    My boat is also designed for rowing single or double with just a quick conversion of seats and outriggers. One of these days, I'm going to find someone to row doubles with me (he says hopefully).
     
  4. JosephT
    Joined: Jun 2009
    Posts: 856
    Likes: 107, Points: 43, Legacy Rep: 218
    Location: Roaring Forties

    JosephT Senior Member

    Indeed. Ben's boat was designed to win. Your boat definitely has multipurpose possibilities and it will provide decent speed. If you want to race it you'll probably want to enter into the correct hull & age division. Many good races have senior divisions with respectable names (e.g. Masters, Gold, Platinum). Gotta honor us older folks! We can still chew nails for our age!

    You've got a nice boat there. I would be tempted to mount a temporary transom & small outboard so I could do some fishing as well. It's definitely a good all around boat to enjoy.
     

  5. SailorDon
    Joined: Apr 2013
    Posts: 137
    Likes: 4, Points: 0, Legacy Rep: 34
    Location: Livingston, TX

    SailorDon Senior Member

    There needs to be another Senior Division for Sailor Don:
    Coffin Dust.[​IMG]

    With respect to outboard motors on Whitehall Rowing Skiffs (like the Heritage 18), that does not set well with the cosmos. :(
    However, the manufacturer offers an optional outboard motor mount (which I ain't got.)

    I do have a temporary "bolt-on" transom for mounting the flagstaff.
    [​IMG]
     
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