16-18' "Sit-in" Planing Monohull ("Trapwing")

Discussion in 'Sailboats' started by Doug Lord, Feb 27, 2009.

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  1. Doug Lord

    Doug Lord Guest

    I have always wanted to sail a boat like a 2.4 Meter but with much higher performance. I suggested a concept years ago and wonder if anyone else has any thoughts on how to make something like this work or improve the concept.
    The idea I had was to use a molded "wing" that would have ballast slide inside it to give large RM-similar to a two handed dinghy where one of the crew is on a trapeze. The ballast could be moved by hand, foot power or electrically. The boat might have a small fixed keel. The ends of the "wing" would be slightly larger in section to provide extra buoyancy. Each side of the wing would be supported by a "trapeze" wire making moving the whole wing(and the ballast inside it) fairly easy since it all moves horizontally.
    The idea is to sit in the boat like a 2.4 meter but plane early and fast.
    I'm interested in any ideas that would accomplish this in a relatively small POSSIBLY self righting monohull....

    Personally, a boat that would sail like a Windmill- with me sitting in the center- would be cool. That boat planes in 10 knots or slightly less and is a great ride offwind in a breeze. But a boat could be built that would be a bit more powerful and meet Bethwaites criteria for upwind planing:
    LOA 16'(or so)
    SA-around 160 sq.ft. upwind
    12' sliding "trapwing" with 160 lb ballast
    All Up boat weight minus wing,wing ballast and keel ballast including rig:160lb
    75lb keel bulb
    130lb-180lb crew
    SCP/Total Weight=30% @ 180lb crew

    As I envision it the wing+ballast is supported by trapeze wires-side to side movement would not require a whole lot of effort....
    Just as a rough illustration here is a picture of a Melges 24 model fitted with a "trapeze power ballast system". The battery was part of the sliding ballast and that could be done on a full size version. The "wing" on the model is just two carbon tubes that form a track for the ballast to slide on. To me, a molded wing
    on the full-size version would have a number of advantages including lower aerodynamic drag, buoyancy and it could be built with a slight curve.
    A well designed, tested and proven version of this boat(that was self-righting) COULD offer disabled sailors(and/or grumpy old men like me) a high performance single-handed alternative to the 2.4 meter. BUT,and this is important: to be viable this boat does not have to be suitable for disabled sailors! Don't view this concept ONLY thru the lens of what might be suitable for disabled sailors.
    Here's a pix of the model with the movable ballast system supported by trapeze wires:

    Attached Files:

  2. PI Design
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    PI Design Senior Member

    Hi Doug,

    The concept of a fast, sit in, boat is appealing. A couple of quick thoughts though:

    160lb is very light for a 16ft boat - especially if you are coounting the spars, sails, foils, rigging etc.

    The main challenge to overcome is probably how to centalize the ballast quickly, in the evnt of a lull or wind shift. It is common practise for trapeze sailors to get dunked as the power falls off - a capsize to windward can follow. The ballast would also need to be centred in the event of a capsize.

    For both these reasons, a 'fail' mode of centralising the ballast would be a good thing.

    An alternative could be to have buoyancy sliding to leeward, rather than ballast to winward?
  3. Doug Lord

    Doug Lord Guest

    Good thoughts,Pi. The wing is buoyant even with the weight at max extension.
    It might be possible to use removable training wheel floats on the wing end to help with getting used to it though the design calls for extra buoyancy there any way. I wouldn't want to create a multihull out of a monohull but it doesn't matter too much as long as its fun to sail-and can be made self-righting. Some sort of hybrid maybe? An electrically controlled system could easy use an auto centering overide that kicks in at a certain angle.
    I think an IC all up is around 120lbs at 17',isn't it? An 18' A Class cat is 160 lb all up I think.
  4. Daniel Noyes
    Joined: Feb 2008
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    Location: North Shore, Massachusetts

    Daniel Noyes Junior Member

  5. Doug Lord

    Doug Lord Guest

    Somebody made one I think-probably would be fun. I think it might be hard to equal the RM of the "trapwing" even with a canting keel and a lot of beam. Just for the heck of it I'll look into it a bit. Thanks for the suggestion.
  6. bistros

    bistros Previous Member

    Doug: Some basic concepts with your idea that need re-thinking (or perhaps initial thinking):

    1) The movable ballast weight can not exceed the bulb weight or the boat will not be self righting. It will be self capsizing. You can not count on the ballast weight being to windward. As another poster pointed out, teabagging happens to everyone.
    2) The upwind sail area is tremendous for a light weight single hander. It exceeds that of a SwiftSolo, RS700/600 or Musto Performance Skiff by 20%. All these boats are challenging expert trapeze boats that require superior mobility. Add a big asym-kite to this and the whole thing becomes a psychedelic voyage.
    3) The all up weight is spectacularly low for a 16' boat that one would expect to be built for safety and reliability. Light weight is wonderful but it comes at the price of reliability and high cost.

    I too would like to design a low cost, low work-effort, perfectly safe, armchair comfort, lightweight high tech boat that could blow away International 14s with no mobility required by the operator. In the world I live in that means it would have to have an engine and a gas tank.

  7. Doug Lord

    Doug Lord Guest

    1) Not true. Even at 90 degrees after a knockdown- with the ballast and wing extended- the boat is selfrighting with the specs above since:
    a. the wing ballast is at the heeled cb(boat + wing at 90 degrees)
    b. a portion of the wing is immersed and acts with the keel to make the boat selfrighting. If I were to do this I would sail it without the keel and it would not be self-righting-just marginal. If an electric ballast system was used it would automatically center the wing acting to literally push the boat back upright-with sheets slack.
    c. The boat would be hard,if not impossible to capsize with the wing moved in the direction of the capsize. The buoyancy of the wing exceeds the ballast by a wide margin.
    d. Again, the specs above are for a turbo version of the concept-a much more forgiving version is easily possible.

    2) That's actually the point. In addition, because the person is sitting very low the main would be significantly lower than any boat you mention.

    3) This version would have a very narrow hull with ,perhaps, 50% of the hull area and wetted surface of the boats you mention. The weight-for the type of hull I envision- is easily attainable in an 18' hull.

    4) That's a real shame......
    PS-Since the crew adds virtually nothing to the RM the crew weight range could be something like 100lb to 220lb- not equaled by almost ANY other high performance monohull.
  8. Daniel Noyes
    Joined: Feb 2008
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    Daniel Noyes Junior Member

    Wher you are going ultra light and hopeing to plane I think a wide hull combined with some sort of shifting ballast may be the way to go. The form stability of a wide hull can be a huge plus when trying to cary sail, the trick is, it is as stable upside down as right side up. The fastest sit inside type boat I think would be based on a ultra light scow type hull, the shifting ballast will alow it to sail on it's chine (just as narrow a waterline as a narrow beam boat with bulb keel) in even light wind, and it will have major sail carrying power on and off the wind...some people dont like the look of a square bow though, thats why I suggested the Open 60.
  9. Doug Lord

    Doug Lord Guest

    Thats definitely something to consider. By the way,your boats are gorgeous
    and your workmanship appears to be very,very good!
    Thanks for the idea...
  10. Chris Ostlind

    Chris Ostlind Previous Member

    You guys who do not read Sailing Anarchy's various Fora may want to read what the boys over there had to say on this very topic after it was floated by Doug back on Feb 18th.


    Ever more complex. Yep, that's the answer to what ails the human race. Yes sir, give me more of what most folks already do not understand. I mean, can't we see that we're handling the complex nature of our modern lives with such aplomb already? Let's heap it on even higher and just call it good.

    How about good clean design that simplifies the experience so that the real beauty of the sport of sailing can get through the morass of crap that bombards us daily?

    Something to ponder.
  11. Doug Lord

    Doug Lord Guest

    Wow,did I mention foils?
    You can't beat this concept-nice and easy thru "Turbo"- to allow the time and comfort to really absorb the ecstasy of fast sailing or just ghosting along. Spectacular views from a unique perspective in a high performance boat.
  12. Daniel Noyes
    Joined: Feb 2008
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    Daniel Noyes Junior Member

    The idea is interesting to me because I have recently been looking at affordable "Adaptive" sailing, While looking into the handicap acessiable sailing scene I was astounded that the single handed olympic boat is the 2.4m these boats are a bear to transport with their great weight and full keel and are probably one of the most expensive racing classes per foot of boat. I imediately thought a scaled down ocean racer could easily out perform one of these scaled down twelves on most points of sail and cost about the same. I have continued to develop the idea toward simplifying and reducing price to where I think an adaptive sailboat could be assembled for under 2,000$ US. Price is the greatest hurdle for someone looking to get into sailing but living on a limited fixed income.
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  13. Doug Lord

    Doug Lord Guest

    I really like your thinking,Dan. One of the reasons I like the "trapwing" is that it will allow high performance to be accessible by almost anyone from a weight, size and physical limitation perspective. Also, the trapwing system allows a beach launched boat which could be beneficial. But I don't think it could be done for under $2,000-particularly with an electrically moved ballast system.
    How would the ballast be dealt with on your proposed boat?
  14. Daniel Noyes
    Joined: Feb 2008
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    Daniel Noyes Junior Member

    I have been looking at retro fits for existing small one design board boats and a popular single hander sailed in the regular olympics. balast bulb on an longer than original dager board combined with a mast head float to prevent capsize and make the boat self righting when the sailor exits cockpit, a drop in sailing seat and push pull tiller arrangement that would work with existing rudder, the 2,000$ supposes the purchase of a preowned boat at a fair price. The Addaptive alterations are looking like 800$ +-

  15. Doug Lord

    Doug Lord Guest

    The problem I see with small planing hull boats adapted for this is that a fixed keel requires an angle of heel before it develops RM-I'm concerned that that may be a limitation on your idea.
    I grew up racing a Windmill and recently considered using the trapwing system as an add-on for a singlehanded version because with the trapwing it could be sailed flat. Most planing dinghies need to be sailed flat for best performance BUT your scow idea would remove that problem....It might create another problem in light air when you'd want to heel but couldn't w/o movable ballast.
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