designing a fast rowboat

Discussion in 'Boat Design' started by nordvindcrew, Oct 13, 2006.

  1. NoEyeDeer
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    NoEyeDeer Senior Member

    When are you thinking of starting the build, Ben?
     
  2. BenH
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    BenH Junior Member

    That's a good question that I don't really have an exact answer for. I'm wrapping up a guideboat (Grant Virginia) in Kevlar and fiberglass right now. It should be done by the end of the month. I was planning to put it through it's paces for a while and get a good feel for it. I'm hoping to spend my summer out tripping instead of building, and come September I should have a good knowledge base on whether I need to tweak my current design any. So, hopefully I'll get it started this fall. I'm a pretty slow builder. About a year per build, so don't hold your breath. I'm also working on another boat, basically the exact opposite of a fast lightweight rowboat, a drift boat based off the Rapid Robert design. We'll see which one is striking my fancy come September, but most likely it will be the guideboat.
     
  3. NoEyeDeer
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    NoEyeDeer Senior Member

    Fair enough. :)
     
  4. BenH
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    BenH Junior Member

    NoEye, you've had some time now to test out your design. What do you think so far? She was a beaut from what I saw at the Aussie woodwork forum. And light weight for a 19 footer.

    The only race I follow around here is the MR340, no rowing allowed, only paddles and peddles. So, have any of the boats in this thread beat out the guides in the Blackburn yet?
     
  5. NoEyeDeer
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    NoEyeDeer Senior Member

    She's generally a good boat, but not perfect. I haven't done any racing yet, due to the race I was thinking of being a long way from here and life getting in the way, but I have managed to get some rowing in under a range of conditions. Easy to cover ground in if you're just cruising.

    However, while directional stability is better than the Herreshoff boat it's still not quite as good as I would like it to be. In windless conditions this is not such a bad thing as the boat tracks well enough and is surprisingly nimble for such a long boat.

    With a wind on the beam she's well-balanced and will track straight if the breeze is even. What causes problems is gusts on the bow, which can make it fall off and require correction.

    Gusts from astern aren't much of a bother. She will actually blow straight downwind with the oars clear of the water, although the hull will be crabbing at 10 degrees or so. What seems to happen is that the boat rounds up a bit until the box garboard aft starts biting, then just goes downwind. If rowing downwind, even with little effort and a low stroke rate, she's easy to keep on course, particularly if I just chuck my boots or whatever right into the stern for an extra touch of trim.

    The other problem is leeway. The midship section underwater is similar to the Herreshoff and has little lateral resistance, so although the boat is balanced with an even breeze on the beam she drifts to leeward more than I would like. I can compensate by rowing at a slight angle upwind, but the leeway combined with gusts on the bow can make rowing along a lee shore an exercise that is not for beginners. She needs to be kept off with some water in reserve, just in case.

    Seems a bit less inclined to pound than the Herreshoff boat, which is probably due to being a bit narrower on the bottom (about 13" compared to 16") and with more depth to the chine forward.

    Initial stability is enough to be idiot-proof and reserve stability is very good. Roll damping is excellent, even when standing up (providing the water is fairly calm). This is something else I was aiming for and that she does better than the Herreshoff boat. Would definitely be stable enough for fishing, as long as you weren't going after marlin.

    My conclusion is that although the hull form is an improvement compared to the Herreshoff, which was one of the main aims, it is close enough to the same form to share the same problems to some extent (leeway and tracking). I am still considering whether it is worth adding a retractable fin (very small daggerboard) just aft of the third frame.

    So yeah, good but not perfect.
     
  6. Clinton B Chase
    Joined: Mar 2005
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    Clinton B Chase Senior Member

    Updates

    Good to hear updates from folks. I love the strong keel on the Drake rowboats. I struggle to decide how to handle that on the Drake Raceboat. Of course, a strong keel makes for more wetted surface and weight.

    I am finishing up the modeling of the SLRS Annie and will build that with a group of students in August.

    Then I will model in quarter scale the Drake Raceboat for this winter's build.
     
  7. NoEyeDeer
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    NoEyeDeer Senior Member

    I'm already thinking about the next boat. I'll do some more rowing and thinking first. ;)
     
  8. Jamie Kennedy
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    Jamie Kennedy Senior Member

    I remember reading a technical paper about flatwater boats that indicated that there is a lot more to lose by being shorter than optimal length than longer. So the idea would be to err on the side of being longer. I think for an open water boat this may be even more true where then extra wetted surface of a longer boat is compensated by such things as better handing into waves and wind, and more speed potential when rowing with the waves and wind.

    That said, the fact that you should err on the side of longer makes it even more compelling to reduce beam and freeboard, which then becomes a balancing act, is you can excuse the pun, between building a modified racing shell that cuts through waves and is closed in but needs to be actively rowed and at some point will be overwhelmed, and a more comfortable and seaworthy craft that might be slower most of the time, but is still a wonderful boat to row in flatwater, and, let's face it, a much more sensible boat for open water rowing in pretty much all conditions.

    So how would you write a rule to categorize boats for open water racing to allow open design, but prohibit modified racing shells that are superior in all but the most extreme conditions, or when the crew needs to stop rowing for one reason or another? Perhaps a minimum volume as a function of length. To keep costs down you might also have a minimum weight and radius of gyration as a function of length. Then there is the matter of how open the boat should be. I think we all agree that boats should be allowed or even required to have built in flotation, but it would be nice if they didn't have to be closed in completely, not just for aesthetic reasons but also for functional reasons. This is where the rules can become very specific and restrictive. One practical and natural way to allow more design and construction freedom is to always allow boats to have removeable decks or covers, so they can be rowed more open in fair weather, and still be competitive, and safer, in more adverse conditions.

    The other thing to do is always have lots of prize categories, including things like oldest boat, oldest rower, best looking boat, designers choice, builders choice, best family boat, cheapest boat, cheapest rower, etc. ;-)
     
  9. NoEyeDeer
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    NoEyeDeer Senior Member

    Shorter boats handle better in wind, and in rough water you'll often be going slower than in flat water (unless you happen to be surfing). Shorter boats are also more likely to go over rather than through the waves. My feeling is that a rough water boat would, if anything, optimise at a shorter length than a flat water boat.

    Anyway, I just remembered one good thing about my boat's low lateral resistance. Some of the launching spots around here have quite steep drop offs from the water's edge, That means the best way to board a long and skinny boat is from the side, but you then have to get far enough away from the shore to be able to run shore side your oar out.

    This turned out to be easy in my boat. I just put one foot in the middle, give a good hard shove off the bottom with the other foot, and use that shove to also bring my body into the boat. She sits over on her bilge and just slides out sideways for eight or ten feet, at which point I can just row off. :)

    She's easily stable enough for this to not be a drama, and having her heeled over makes her scoot sideways very easily.
     
  10. Jim Gallacher
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    Jim Gallacher New Member

    What design is this boat built around?

    Hello NoEyeDeer,

    Can you give me some info about the design of this hull? I am wondering if it is based on an existing craft and or how you came up with the moulds? Thanks.


     
  11. Manfred.pech
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    Manfred.pech Senior Member

  12. NoEyeDeer
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    NoEyeDeer Senior Member

    Yeah sure. What I was after was a boat that had a decent turn of speed, but with stability anyone (within reason) would find reassuring and with decent carrying capacity (up to three adults in fairly good conditions). I also wanted a flat bottom with no protrusions, for dealing with mud flats.

    The Herreshoff/Gardner boat fit the bill pretty well, but in my opinion has poor directional stability, and a very quick and nasty roll when moving around the boat. What I did was to get rid of the rocker aft to add some deadwood/skeg to help tracking, and give it a harder bilge above the waterline to dampen the roll without adding wetted surface.

    I gave it a nice sheer, since I don't like the "powderhorn" effect that Gardner's offsets give. I added a transom, to give more stability when down in the stern for whatever reason, like when poling or sculling or retrieving my boots from where I threw them. She'll take my weight right aft, without the gunwales going under and with tolerable stability.

    After running a range of options through Michlet, I also made the waterline length longer and increased the prismatic. This does increase wetted surface, but according to Michlet gives quite dramatic reductions in resistance once speed is 4 1/2 knots or more, at the cost of approximately 20% more resistance at speeds of under 4 knots. If you want a boat for 4 knots or less then a shorter boat with a lower prismatic would be better.
     
  13. flo-mo
    Joined: Jul 2010
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    flo-mo Junior Member

    Blackburn Challenge 2015

    Ben Booth who won the fixed seat single class at record time last year is rowing the same boat but this time with a sliding seat.
    No results yet but I assume conditions were not the best for sliding seat this year.

    https://youtu.be/WroTIThoYTU
     
  14. flo-mo
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    flo-mo Junior Member

    Blackburn Challenge 2015

    The results are in: http://www.blackburnchallenge.com/CARC_Race_Results.asp

    Congratulations Ben Booth on winning the sliding seat touring class with your Westport Racing Skiff -- must have been a tough race which tells a lot about the seaworthiness of your design and your rowing skills given this year's rough conditions.

    Video from Halibut Point State Park, with a 10-15 knot NNE wind creating some 4-6 foot seas: https://vimeo.com/134538093
     

  15. Tallman
    Joined: Jun 2011
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    Tallman Junior Member

    Great link, Flo-Mo!
    The guy around the 3:46 mark in the video won the sliding seat racing category. He's in a Van Dusen Mohican kayak modified for sliding seat.
    Looks like Ben is on screen at about 4:34.
    The winning times for the two events are nearly identical -- Ben has indeed designed a very fast boat and is a very strong rower.
    Fascinating to see how different boat designs handle that crazy water.
     
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