sailing dinghy

Discussion in 'Boat Design' started by old dog, Oct 3, 2012.

  1. old dog
    Joined: Dec 2011
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    old dog Junior Member

    I know I'm crazy but I would like to fit a sail to my 4.27m Quintrex deep v hulled clinker style dinghy. Any thoughts? (not about my mental state please). Regards Rob L.
     
  2. alan white
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    alan white Senior Member

    Go for it------ but being a power boat hull, it will surely drag a ton of water behind it due to the wide straight run, making it a real dog to sail.
    The theories behind power boat design and sailboat design are completely different. Sailboats rarely get up on a plane (or if they do, they are heavily comprimised to also sail well without planing). Power boats are the opposite. They almost always are designed to plane and they are incredibly inefficient at powering at sailboat speeds.
    The difference is mostly in the way water exits the transom. If you examine sailboats you'll see that at the waterline, the "footprint" of the bottom is lens-shaped and the powerboat is flat iron shaped.
    I don't think you're crazy but if you do what you're thinking you are certainly not going to have much fun sailing. I suggest you go sailing a few times so that you can appreciate how sailboats move and change direction on the water. Then take a motor boat for a spin at sailboat speed. You'll see immediately how different the water looks exiting the stern. The sailboat hardly disturbs the water but the motor boat wastes a lot of energy and drags its transom deep in the water.
     
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  3. Skyak
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    Skyak Senior Member

    I take exception to to the statement that sailboats rarely plane. It is an outdated generalization based on old keel (or fixed center ballast) boats. Almost all modern sailing dingies (and other ballast shifting monohulls) are designed to plane. The latest high performance designs are sacrificing displacement mode performance for increased planing efficiency with stepped hulls and lifting foils -more advanced planing hulls than most motorboats.

    Alan's statement presumes that you are not going to add the large high performance rig it would take to push your hull into it's design range and in this he is most likely right.

    What do you think you are going to put into the project and what do you think you will get as a result?

    There are lots of smart designers here. At their best they can save you time, money, and possibly your life. At worst (the way you are using them) they will do nothing more than point out your ignorance in their field of expertise.
     
  4. alan white
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    alan white Senior Member

    Sailboats rarely plane. If you were to suddenly know which of all sailboats now actually sailing were planing, my guess would be a very tiny percentage.
    Sure, more boats designed nowadays can plane------ because material advances have lightened designs considerably, allowing planing sooner as wind increases.
    Any case, whether or not most sailboats today plane has nothing to do with whether it's a good idea to turn an aluminum tender into a sailboat.
     
  5. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    Very true. We like to think of our boats as planing sailboats but it happens much less than we'd like. All but a few are designed to sail fairly efficiently at all speeds and plane when the conditions are very favorable. The effort to turn that boat into a decent sailboat would be better spent on something actually meant to sail.
     
  6. old dog
    Joined: Dec 2011
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    old dog Junior Member

    Thank you all for the response. All valuable. To pick up on a couple of points, my desire is to use the boat to meander around Port Stephens in the most ecological and cost effective manner. I felt the mast should should be placed against the forward bulkhead(some 600mm from the bow) in an attempt to lift the stern. The boat weighs 200kg plus motor plus bodies etc; say 500kg total. I was thinking of using a simple gaff rigg. Please keep putting in all your imports. I'm like Sgt Schulz, (I know nothing!)
     
  7. PAR
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    PAR Yacht Designer/Builder

    Sgt. Schulz, you'd be best advised to pick up a $500 well used sailboat, than sink $1,500 into making a powerboat into a dog of a sailor, particularly if you're going to guess at rig type, it's placement and of course appendages too. I'll assume you have a Dart or other 14' aluminum scooter. As you've heard, these aren't very well shaped for a sailing application, but sure you could get it to move at say 4 knots with a big enough rig. Much faster then this is simply a dream that will not come true. You'll need appendages, likely retractable and a rig, that's properly placed over them, considering the hull shapes provided. Yep, 4 knots might be just a pipe dream too, maybe 3.5 knots would be more realistic. Provide the year and model of your Quintrex?
     
  8. old dog
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    old dog Junior Member

    Busta 4.2 2012
     
  9. Skyak
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    Skyak Senior Member

    Your money would be much better spent on a used sailboat. Beyond the sluggish speed (which you might be willing to tolerate) the windward performance is likely to be atrocious. 180 degrees of heading being off limits will be intolerable. Catboats (mainsail on the bow) are intrinsically ornery handlers and you are applying it to a hull that is too narrow. If you make the sail smaller for handling it's butt slow. If you make the sail big enough for your full load it will be unmanageable, possibly unsafe for single-handing. You do know that even well designed dingys often suffer knockdowns -not good for outboards.

    If you still want to add sailing capability I suggest you make it furlable in seconds. I have a design to put a roller furling genoa on the rail. I think it would be the cheapest and safest you are going to get.

    Regarding sailboats that plane; Scows A,B,C,D,E fireball.... all wing dingys Moth, international canoe, ausy 14s, 18s, 49er...All olympic classes, laser, finn, 470, and even keel boats downwind and reaching... most if not all multihulls beach cats, trimarans...

    Generally, if you look at new performance sailboat designs for a crew of 3 or less the vast majority are designed to operate beyond hull speed.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Its one thing to have the potential, yet another to have her up and scooting most of the time. Most of the time, in spite of the potential, they're in displacement mode.
     
  11. Skyak
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    Skyak Senior Member

    I would agree that all dingys must be designed to perform well in displacement, but as a laser sailor I see wind in two values, 'planing', and 'why bother'.
     
  12. old dog
    Joined: Dec 2011
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    old dog Junior Member

    After careful consideration I bought a second hand 16ft Hobbie. Together with the tinnie, my lawn looks like a boat yard! :cool:
     
  13. PAR
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    PAR Yacht Designer/Builder

    You'll have fun on the Hobie 16. You get wet, learn how to sail, eventually out grow it and with your new found skills can make a much better choice the next time out (there's always more boat, just get used to it).

    Congratulations and have fun. At this is time of year in New South Wales, you should have a lots of time, to get to know the old gal, likely finding other beach cats to poke around with, compare notes about, etc.
     
  14. messabout
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    messabout Senior Member

    Good decision Old Dog. The H16 will be a fun boat. It'll go like a bandit and give you a lot of whoooie! moments.

    Way back in the olden days, I bought a truckload of 12 foot Nova Scotia molded shapes. They were hot molded birch, round chined power boat hulls. They came as the molded shape only. No transom or other parts. They made a nifty little runabout and were very attractive when well finished. I got a bug in my bonnet that told me to use one of them to make a sailboat. Pretty little thing it was. Didn't sail worth a damn.

    The ill concieved little sailer was eventually sliced in half, down the middle , installed a nice flat mahogany deck that covered the entire surface. Then added shelves and drawers underneath the deck. Three pretty little legs held it off the floor and it made an appropriate desk for the showroom of our boat business, never to sail again. The other half of the boat went into the dumpster.

    If that tale could be used as any sort of precedent, then your decision to leave the tinney alone was fortunate.
     

  15. PAR
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    PAR Yacht Designer/Builder

    Were those molded 12' boats out of Nova Scotia, Clydes? I'm aware of a Michigan company (Clyde Boats) that offered 12', 14' and 16' warped bottom, round bilge, birch molded (Ashcroft) powerboats, but the hulls where hot molded in NS. There were some mahogany hulls as well.
     
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