hull shapes for low (paddle) powered ocean-going boat

Discussion in 'Boat Design' started by AdvEndureDesign, Mar 29, 2014.

  1. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,015
    Likes: 912, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

  2. Skyak
    Joined: Jul 2012
    Posts: 1,219
    Likes: 37, Points: 48, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    I like all craft powered by natural means (human and environment). SUP has the lowest power and bio-mechanical efficiency and the highest "look at me" value so I am inclined to not like it. The fact that it is so popular doesn't help. That said, my god-daughter rented one at the annual family gathering and I enjoyed the view. Now I stand up paddle my kayak occasionally. It's a refreshing alternative when I have been sitting a long time. At any rate I can assure you that I am very interested in your project and dedicated to your success. There is a children's saying 'sticks and stones may break my bones but names will never hurt me'. You might not like what I say but the ocean can deal out some vicious conditions to those that can't run away. The one question I have is how do we know the paddler never sat down and choked up on the paddle?

    About the re-configurable cabin, what I had in mind is a sealed fabric that has internal and external structure to fold into three shapes, down, port wind, and starboard wind. There is no 'storing' it. It is always attached and always sealed except when entering or exiting. If you have concerns about the durability of the fabric and folding, consider the 50s atlantic crossing in a klepper folding fabric hull. I can help you with the design. A big non-performance benefit of the fold down cabin will be photo-ops. With the cabin down your craft will look like a SUP.

    Thinking more about it I like the idea of a wide tail. The increased fore-aft stability is a good point and I got to thinking about sliding backward on big rollers -a sharp tail would be more inclined to broach backward. Following waves are a great opportunity to make miles so anything we can do to help you catch and ride waves will be important -sprint acceleration and maneuverability.

    The canoe picture you included shows a big deep fixed keel with bulb, and a fixed rudder. It looks like a small sailboat that lost it's rig. I am inclined to value the ability to retract the foils to adjust to wind and wave direction. Sometimes the ability to slide off a wave can save you from being rolled and surfing is too dangerous with a keel down forward.

    The last advice I have is about dynamics and prep. The best thing you could do right now is get a hull anywhere near the size and shape you intend, and load it up to your intended displacement. Get out and paddle it standing up. Do it in progressively bigger waves and bigger winds. What conditions can you make progress in? What condition put you in lifeboat mode? The history of conditions along your route are known and there are probabilities of what you will encounter based on your speed. Smart programs test in worst probable conditions in safe locations before the crossing attempt.

    What is your communications plan?
    How did you determine your displacement?
  3. Navygate

    Navygate Previous Member

    Good of you to indulge this individual despite your distaste for his flavour of adventure.
    I hope he appreciates and benefits from your generous guidance.
    Good on ya'

    Oh, do you have any photos of your God-daughter on that SUP? :)
  4. AdvEndureDesign
    Joined: Mar 2014
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Lübeck/Hamburg, Germany

    AdvEndureDesign Junior Member

    I'll wager that England simply has the strongest "recreational" rowing tradition in modern history, and the development on the English rivers has made it into a sport regarded as noble and sportman-like (see The Boat Race, aka Oxford University vs. Cambridge University). Combined with the British naval tradition, John Fairfax and others of his ilk it's possibly a culturally attractive pursuit. Also, with precedence comes national media attention, and at one point a critical mass is reached. Outside of the UK ocean rowing has not gotten a whole lot of attention overall.

    Interesting question, though!
  5. AdvEndureDesign
    Joined: Mar 2014
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Lübeck/Hamburg, Germany

    AdvEndureDesign Junior Member

    It's luckily not my place to have to decide on the value or ego behind this project, but I am happy to be challenged with this unique set of parameters. Apart from that I am very grateful for any and all sorts of input, and even if I might not "like" any of it, I believe to be able to discern enough to take the necessary (and that they are) lessons from it. So again, thank you for your input, it's highly appreciated.

    The paddler-sitting-down issue: Frankly, there's no way of telling, obviously. He might just as well paddle prone.

    The "cabin" idea made me think about inflatable structures, but reconfigurable, folding ones with a more standard reinforced approach may be just as valid. My concern is rather with wave impact and high wind pressure. The whole would have to be sturdy enough to allow for the paddler to sit (well, lay, rather) out extended periods of bad weather under para-anchor. This is a very tricky part!

    Wide tail is the current direction I'm modelling in, so in any case this will be one of the main hull shape ideas to evaluate.

    Regarding the appendages I'd discard the keel idea overall and prefer a daggerboard, for all the reasons you pointed out, especially reducing draft and wetted surface. The photo of the Hungarian ocean canoe was intended for illustration, not showing a preference. It can, as showed this crossing, not prevent the boat from capsizing, so a daggerboard seems to give most of the benefits without the added weight.

    Your suggestion regarding the prep is sound! I'll have to investigate what sort of hull might be most suited, and see to arranging for the tests with the paddler. Also a detailed idea about specific power output would be of value. Overall a ton of testing will have to go into everything about this before any major crossing can be attempted, and a training programme will have to ensure the paddler knows the behaviour of the boat in and out under all conditions.

    Communications - I assume you mean the actual communication from onboard - will likely be via a satellite phone, as is standard these days. Project communication (as in PR) overall is grinding into gear, but as of right now is lacking a boat design!

    The design displacement I determined by listing all necessary items of equipment (using the equipment lists of ocean rowers as guideline), researching and adding up all weights from actual products in an Excel sheet. It includes an assumed empty boat weight of 100kg, the paddler's own weight, 100kg of food, 50kg of cooking fuel and 100l of water reserves (here be ballast). With all this I end up at about 520kg, and then added a "fear item" of 120kg just to be sure for initial modelling... which I probably really shouldn't.
  6. SukiSolo
    Joined: Dec 2012
    Posts: 1,270
    Likes: 25, Points: 0, Legacy Rep: 271
    Location: Hampshire UK

    SukiSolo Senior Member

    Be careful with the placement of the 'daggerboard' or forward fin. It is possible to go too far forward and get reverse steering!. To help avoid this placing the rudder fairly well aft ie transom or stern hung helps. You need to be sure the hull will pivot correctly about the 'daggerboard' when steering.

    I have seen a 12' experimental sailing dinghy hull with no c/board which put lateral area as a fin down from the stem and had a transom hung rudder. It was in certain conditions ie planing almost unsteerable in that configuration. The 12m America 3 (Bill Koch) was later but a similar concept except she had to have a more central keel fin for ballast being a keel boat and that saved her from that particular nasty. Also I believe her bow fin was a limited movement rudder.

    Not sure why us Brits do so much sea rowing but in the SW there are lots of gigs, eights with raised freeboard and other craft. Also we have lots of big enough bits of waterway ie Thames, Trent, Severn, and a fair few canals to enable a lot of rowers to practise their craft.

  7. AdvEndureDesign
    Joined: Mar 2014
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Lübeck/Hamburg, Germany

    AdvEndureDesign Junior Member

    Good point to keep in mind at least! Difference here, though, is the lack of center of efforts from mast/sails. Cabin and hull sides are the only components in windage.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.