Triangular experimental hull

Discussion in 'Boat Design' started by Jamesblack, May 17, 2014.

  1. Jamesblack
    Joined: Jun 2013
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    Jamesblack Junior Member

    Hi guys. I have been designing a single handed 10 ft sailing dinghy that is a lot like a triangle. with a budget of About $700 (AUD). i will be about 3.0m long and 1.2m BEAM. it shall be constructed of 6mm marine ply for the most part, have wings, and an international cadet mainsail of only 4 sqm. i plan on using this sail because i already have it, and a suitable section of aluminium tubing for the boom with a bolt rope track.
    To make it look better, and increase strength and sailing properties, it will have a slight v-bottom, similar to a mirror dinghy. i could build a regular sailing dinghy, but it would be pointless and not much of an experiment. i know this is a crazy idea but i would like to hear your thoughts.
    some of the paint, the sail, boom, fittings and running rigging i already have after owning a international cadet and i am currently restoring a mirror dinghy.

    thanks for your time and i would love to hear your comments, ideas, comments and suggestions.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    If it is really triangular in plan view, and only 1.2m wide max, it won't be very stable, and gawd know what will happen when you plow into the back of a little chop.
     
  3. Jamesblack
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    Jamesblack Junior Member

    It sounds better when you think of it as wave piercing.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like the sail version of the "sea knife".
     
  5. Jamesblack
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    Jamesblack Junior Member

    you're not far off
     
  6. Jamesblack
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    Jamesblack Junior Member

    What is the likely hood of this hull ever planing?
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Depends on how many buckets of fried chicken you eat ! You will weigh as much as the boat, in all likelihood. Some people who know more than I about sail ( that should be most everyone) might offer an opinion, but I would not back it to plane with a tiny sail area.
     
  8. Jamesblack
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    Jamesblack Junior Member

    My international cadet only planes with main,jib and spinnaker in more than 10 or 15 knots.
    All I really want to do is go faster than the cadets (blunt bow and crew of two) on Sunday sailing. Maybe I will need an assymetric spinnaker. My hull should be slimmer and pointer, with higher spect foils but maybe not faster downwind.
     
  9. WhiteDwarf
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    WhiteDwarf White Dwarf

    with a Cadet mainsail!

    James,

    You will be severely restricted in power with the lack of sail area by this choice, which is barely more than an Optimist sets.

    Optis do plane because the lift per unit of bottom that they have to generate in order to over come the wave making characteristics of their hulls are very low. As a result they can, relatively easily ride over their bow wave. Read up on Froude numbers in Wikipedia.

    As I read your intention, your concept will be more streamlined than an Opti, but may have less lifting surface (bottom area) and it may also need more rocker in the keel, to carry your weight particularly if you use 6mm ply. This is likely to restrict maximum speed on the plane.
     
  10. Jamesblack
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    Jamesblack Junior Member

    I don't think strength will be a problem because the bullheads for the buoyancy tanks and the strong wings combined with the v bottom make the hull quite rigid. (I only weigh 60kg)
     
  11. Hampus
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    Hampus Junior Member

    If it's a true triangle there won't be much buoyancy in the bow, or anywhere else except for the aftmost foot or so. The bow will risk digging into the water if you sail in following seas or if you move forward in the boat.
     
  12. Skyak
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    Skyak Senior Member

    if you have a single symmetric dagger board it will fight the hull underwater profile when you heel -which you will do a lot because your hull is so narrow. The dagger board is more powerfull than the hull laterally so your hull will go sideways and have lots of drag heeled -think of the angle between the chine and the DB.

    Your sail is tall but small -not a good match. You don't have the low drag or stability to go upwind or reach, and a small high aspect main is no good downwind.

    If you had this boat as described I would say the only way to make it fun for anything would be to make a big low aspect headsail to see if you can get it to plane downwind. But then how do you get back upwind?
     
  13. rwatson
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    rwatson Senior Member

    This thread is so much fun. Someone who has some leftover mast, sails and boom is going to create a totally unworkable hull shape, with no calculated performance logic, to perform better than any dinghy hull design in the last 20 years.

    Go James ! Who needs Dr Who :)
     
  14. Skyak
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    Skyak Senior Member

    YEAH! Lets do a pentagonal hull next! Then a bucky ball. Then the shape of a celebrity boob!

    Which one would win a race? My money is on the boob!
     

  15. messabout
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    messabout Senior Member

    Jamesblack;post some drawings of your triangular boat. Then we can asses the efficacy with less mirthful commentary.

    There used to be an APBA powerboat class that had a generally triangular plan form. If I recall correctly, it was a 500cc class of race boat that was the norm for its class. I think that the most popular builder was Jacoby. That was a power boat..............A sailboat? Hmnn. Maybe we'd better consider some other alternatives.

    (Boob shapes are considerably more attractive to we depraved old sailormen.)
     
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