fiberglass canoe conversion to expedition sailboat

Discussion in 'Sailboats' started by josh907vest, Feb 22, 2016.

  1. Steve Clark
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    Steve Clark Charged Particle

    I guess it's a philosophical thing. I think that performance under sail is MOST important in cruising boats. I will accept a bit more draft and having to be a bit more cautious about shoals in order to sail upwind really well when it matters. If your muscles are the only auxiliary power, it comes down to safety if you cannot for any reason paddle your way out of trouble.
    If you have to sail upwind, 10 degrees of pointing turns into 23% more distance you have to cover to get to the same distance upwind and probably means you have to venture further offshore to clear a headland or hazard. You will have to stay out longer, which can be bad.
  2. gggGuest
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    gggGuest ...

    All very true, but I've sailed in places where 6 inches extra draft means 10 minutes pushing the boat until you're in enough water to get enough daggerboard down to be able to sail. These days I simply don't sail at those places any more, because I have the wrong sort of canoe for that stuff, but those sorts of heavily raked foils were common enough in the early days from the likes of Baden Powell and Butler, so they must have worked to some extent, and given modern hydrodynamics...

    Obviously 10% pointing would be utterly unacceptable, but supposing it were 3%? And there's ability to sail closer in to the hazards with a shoal draft capability (if they're not too hazardous) I guess I'm thinking mud flats and natural harbours, not rocks and open sea.

    I suppose the only thing to do is to try it and see just how awful the performance is, but that weird shaped board looks like a ***** to build without the facilities or cash for a cnc core.
  3. upchurchmr
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    upchurchmr Senior Member

    A man after my own heart. I recently went out with a friend in a Compac 16 and was talking about making distance to windward. We took a very long time to get up a short lake. The GPS afterward showed tacks at about 120 degrees (possibly worse). Even a Hobie cat would do a lot better to windward.

  4. markstrimaran
    Joined: Dec 2014
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    markstrimaran Senior Member

    Thin skinned canoe, fiberglassing, taper , feather the bulkhead.

    I built a canoe catamaran a while back. They are factory built to be light weight. Which means if you build a solid bulk head that is not feathered, into the original hull, it will create a stress point. That can cause the glass to Crack instead of bend.
  5. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Not according to my calculations.

    The way I see it, the sin of 50 deg., for the boat that can sail just 40 deg. off the wind is 0.766.

    The sin of 40 deg., for the boat that must sail 50 deg. off the wind is 0.643.

    0.766/0.643 = 1.19 which is just under 20% more distance the less weatherly boat would have to sail to get the same distance upwind. This would mean six tacks instead of just five.

    Now if this meant you had to sail considerably less further out to clear a shoal, the sacrifice might be worth it. Also, with the very deep 'Board, one has to worry about hitting the bottom, even if it can pivot back. This is because the boat could be slipping sideways when it happens. The worse case would be with the deep 'Board shown on the windward side.

    Grounding accidents are far more likely to happen with cruising boats than with racers, as the race courses tend to be put in waters more than sufficiently deep, while cruiser tend to sail closer to shoals.

    I suppose a more ideal cruising boat would have a belt and suspenders approach. It would have at least some windward ability, with the 'Board retracted, and excellent windward ability, with it down.

    I discovered my Siren 17 could sail up wind, even with the 'Board fully retracted. This was a startling discovery, as this boat has no Keel or Skeg. It just has a clean, rounded, canoe body with a deep Center Board and a deep Rudder, with a blade that pivots aft.

    With just the main sail up, and the Rudder pivoted all the way aft, she was able to creep to windward, with many, many tacks.

    This got me out of a bay of tree stumps, which had a narrow entrance, dead upwind.

    I tried it again in the middle of the lake, with a stiff breeze. She did it again, probably pointing no closer than 70 deg. off the wind and making good at least 5 deg. less than that, but making real upwind progress, none the less.

    But I wouldn't want to sentence anyone to dozens of short tacks to reach sufficiently deep water to lower the 'Board, when a considerably less deep, though certainly less efficient one, would be deploy able in far shallower waters.
  6. latestarter
    Joined: Jul 2010
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    latestarter Senior Member

    That depends on how well your boat points.

    If you assume the boat points at 45 degrees and 55 degrees off the wind you get
    cos(45) / cos (55) = .7071 / .573 = 1.232 therefore 23%
  7. gggGuest
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    gggGuest ...

    Can't help thinking disputing the exact effect of made up example numbers is somewhat pointless.

    I think a lot depends where you're going to sail.

    When I've sailed on narrow but reasonably deep rivers the ability to point 2 degrees higher, even if it meant going painfully slowly, could make the difference between getting round the next bend and having to tack into the current and back, which could make a huge difference in whether or not you got home in time for a hot dinner.

    But as I said before, in shallow muddy estuaries - especially muddy estuaries where you *really* don't want to get out and push - the ability to sail reasonably efficiently with very shallow draft may be more valuable.

    So perhaps the craft should be tailored for the job in hand, which isn't really a surprise. Since all boat design involves compromise between competing aims its inevitable that different circumstances will suggest a different compromise.
  8. gonzo
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    gonzo Senior Member

    Geezz, when it gets so shallow that a canoe runs aground, you can push the damn thing.
  9. Steve Clark
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    Steve Clark Charged Particle

    What I encourage is a boat that paddles well enough so that you don't try to sail where there isn't enough water.
    And which sails better where there is.
    I think lee boards hinder both, so offer the alternate view.
    I think that being able to beat to windward efficiently is a requirement of seaworthiness.
  10. philSweet
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    philSweet Senior Member

    @ Steve. I've done a bit of gunkholing over 20 years in the Everglades, and I can sail in shallower water than I can paddle. My skiff could sail reliably in 5" of water. I need twice that to paddle without disturbing the bottom. I can sail a canoe at a beam reach in about 8". Any time you get below about 1 foot, you should just assume you are going to go slowly, like less than normal paddling speed. The trick for dealing with extensive shallows is to know your wading birds. If the bay is full of herons and spoonbills and flamingos and godwits, you can float a canoe and make progress. If all you see is 5 square miles of Red Knots and and sand pipers, not so much. Take binoculars to search for likely passages. My hiking partner and I re-opened some canoe routes in the 'glades that hadn't been tried in 15 years.

  11. Steve Clark
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    Steve Clark Charged Particle

    Nothing saying you HAVE to sail with the board and rudder down.
    I always assume you can pull the board up and steer with a paddle like the ACA Cruising class or St Lawrence skiff.. In my early days of sail training, we were all taught how to sail without rudders, to sail backwards, and backwards without rudders. Where I launch the C Class catamaran is too shallow for the rudders at least 25% of the time. So I steer a 400 lb carbon fiber wing sail hydrofoil catamaran with an oar quite often. It isn't "fast" but I haven't sacrificed any deep water speed because I have to sail in a mud puddle sometimes.
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