Basic questions from a would-be beginning boat builder

Discussion in 'Boatbuilding' started by mitchgrunes, Jul 23, 2020.

  1. mitchgrunes
    Joined: Jul 2020
    Posts: 19
    Likes: 1, Points: 1
    Location: Maryland

    mitchgrunes Junior Member

    What I'm taking away from this discussion is that skin-on-frame prototypes are the easiest, cheapest and fastest to modify, in terms of shape - provided you use a skin that stretches or can be pulled tight over the frame, and you use a construction technique that allows shape modification. But also that SOF limits the final shape, and that if I were a hard-core competitive athlete, it wouldn't be completely optimal - which I can live with.

    If I'm wrong about those things, please tell me.

    In most sports, a lot of people benefit from and use custom made or adapted sports equipment, because it interacts with your body in very individual ways. Also, your equipment lets you express your individuality, and in aesthetic competitive sports, helps you stand out from your peers.

    Naval ship and commercial ship designs are presumably different. The crew and components need to be replaceable and somewhat interchangeable, so customization is counterproductive.

    In the long term, I like the idea of a surf ski/kayak hybrid. The surf ski phase would be easy to launch quickly from and land from in breaking waves, which have a tendency to swamp closed deck kayaks, which can only be partially compensated for by compartments, airbags and sea socks. (I've never used a sea sock. I suspect they are difficult to enter quickly, in surf.) An custom built surf ski would not hold much water while I was in it, and would mostly drain after each wave. I would lips to tuck my knees under. Past the breakers I would zip up the fabric and mount the spray skirt to gain the advantages of a closed deck kayak. A deck pump could pump out the rest of the water. I'd love a fold-up or break-apart design that can be stored out of the sun and bugs, in my home, and need not create roof clearance problems in parking garages, so I might eventually look into aluminum tubing. I'm also tempted, in the long run, to sew, nail or glue a more durable material into the keel, to launch from and land at gravel beaches. Something cheaply replaceable, like vinyl flooring, or veneer. (My best guess is that thick single-sheet materials, like vinyl flooring or veneer, can't be shaped into decent 3D boat designs?? If so, too bad. Vinyl flooring is CHEAP, if heavy.)
     

  2. mitchgrunes
    Joined: Jul 2020
    Posts: 19
    Likes: 1, Points: 1
    Location: Maryland

    mitchgrunes Junior Member

    Maybe I should clarify. I'm believe I'm not alone in benefiting from a somewhat thinner than minimum drag hull, for a given weight displacement and other constraints.

    Because of the ways paddles interact with the water, almost everyone can paddle more efficiently with a near vertical stroke. (Wing paddles, that act like a sideways airplane wing, generating sideways "lift", change this somewhat - rather than the most efficient stroke staying right next to the boat, they are more efficient if they move a little outwards. Nonetheless, wing paddlers too are taught to start their stroke, as close as possible to directly ahead of their body, and benefit from a narrow boat that allows them a longer stroke at the strongest parts of their muscle and joint range.)

    I believe most would also benefit from a full length stroke that ends fairly close to directly behind their body - if they were taught what I believe is the optimal long distance paddling method of holding the paddle, a loose hold in which you allow the paddle to rotate in both hands so as to create the most pull against the water, and in which you end the stroke on a semicircular motion that causes the blade to slice cleanly out of the water, lifting only a few drops of that water. Unless this has changed, many American kayakers and canoeists, whose instructors follow the ACA syllabus, are taught otherwise - that one hand should retain full control over the rotation of the paddle, and they should end their strokes in the middle, because the locked handhold doesn't allow an efficient full length stroke, because it places the shoulder in a potentially injurious position, and which also limits the use of support strokes if needed, at the back of the boat. Of course many paddlers are self taught, and don't think of any of these subtleties.

    While my shoulders are narrower than most men my weight, they are probably wider than most women (and young boys) my weight. So many women should have some of the same issues - though most are more flexible than me, and do not need a high deck over the knees to lean forwards.

    This idea, that the minimum drag hull is not always or maybe even usually optimum for a given paddler, even for competitive racers who are very good at self stabilization, is, one that I think even many competitive paddlers are not taught. Though some surf skis become narrow next to the paddler, which implies that other people have thought of it.

    Competitive scullers (rowers), based on instructions I found on the Internet, are also taught long vertical strokes, and might arguably benefit from this idea too - but I'm not certain.

    Also, righting force (or should I say righting torque?) is complex. First, because hulls that generate a strong righting force tend to be quite wide, and are inefficient, both in terms of drag, and in terms of efficient stroking. (If that weren't true, multihulls might be more popular.) Second because shapes that are very stable in flatwater, are unstable in large waves that break and turn over on themselves across the boat, and are virtually impossible to control under those conditions. So, while beginning level boaters almost always gravitate towards initial flatwater stability, which are also easiest for a beginner to climb into. But the inefficiency is one of the major reasons why they change boats after a few weeks or months. I'm not certain how often large breaking wave instability becomes an issue - most sea kayakers at least try to stay out of high wave conditions, though weather can be unpredictable.

    Finally, mass market boats contain a longer and wider area in which to sit than most people need, so as to be usable by more people. Which means that, even with the commercially available air bags, if they have to empty the boat of water, it takes a lot longer than it should.

    The end result is that a design customized to their specific bodies benefits almost all paddlers.
     
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