A beamy 23 ft sailboat idea

Discussion in 'Boat Design' started by John Smithson, Aug 25, 2021.

  1. John Smithson
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    John Smithson Junior Member

    After reading about the variety of extreme wide beamed boats that have been built / attempted I thought I'd doodle around a bit with it.

    [​IMG]

    Missing cockpit and rudder and other bits, but hopefully the idea gets across. Was thinking maybe with a centerboard and an unstayed mast with emergency floatation at the top, it could have some hope of recovering from a capsize? If so, that could solve one of the major problems with it.

    I'd appreciate someone more experienced explaining why something like this could never work.

    Am I wrong in thinking that an extreme (example, 1.5:1) beam would behave more like a catamaran? (Along with slower speeds, turtling / capsize risk)

    Sorry in advance to those who get annoyed at this sort of thing. Just noodling around a bit, it's a fun subject to think about.
     
  2. gonzo
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    gonzo Senior Member

    It will behave like a buoy more than a catamaran.
     
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  3. bajansailor
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    bajansailor Marine Surveyor

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  4. messabout
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    messabout Senior Member

    Nice drawings John. The design has little if any merit in terms of performance, safety, and building complexity. It will not behave at all like a cat. Would have some steering problems in anything except flat water. Have you calculated the overall weight (expected displacement)? It might be a little bit more stable if you remove the protrusion in the bottom, surrounding the center line.

    It would be more stable if given a near flat bottom or a shallow vee bottom. That thing would be a torture chamber in rough water. Draw some more conventional boats. Your cad program and you are doing OK but best stay somewhere near the mainstream. Think of it this way; Boat design and development has been going on for hundreds of years. By this time we have learned what sort of boat works well for a specific use.

    If you like the idea of a wide boat, take a look at traditional Catboats.
     
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  5. upchurchmr
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    upchurchmr Senior Member

    Another proof that being able to make a picture has no merit for something in real life.
    Apply to some cartoon movie company, nothing they do has to make sense.
     
  6. John Smithson
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    John Smithson Junior Member

    Catboats are pretty interesting, especially since they have such a history being used. They have a 2:1 length/beam ratio, I wonder if it can be pushed even further to a 1.5:1

    I've not seen that many that are larger than 20 foot though (but a quick google says they go up to 30+ feet?). Might be a good option.

    Now that I think about it, you're right. The protrusion on the bottom just lowers the center of buoyancy. Oops. Was thinking maybe putting batteries and other heavier stuff down there, but not sure the gains from lowering center of gravity are offset by lowering the center of buoyancy.

    I was trying to avoid a flat bottom, since from what I read those are the cause of a lot of wave pounding. Maybe shallow vee bottom though.

    Learning fusion 360 has been a goal of mine for a while, so doodling around with random ideas has been great practice. I'm obviously an amateur, why are people so offended by amateurs messing around with basic understandings of hydrodynamics? hah

    Still, fun to think about. I'd like to learn more about the problems with it and what can be done to address them.
     
    Last edited: Aug 25, 2021
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    There will be a lot of resistance you would be better without, basically.
     
  8. Kayakmarathon
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    Kayakmarathon Junior Member

    I looked at the Maxi 650. It has a dagger board, but no weighted keel. Is the ballast embedded into the midship? When heeled, its length/beam ratio gets large like a canoe.
     
  9. bajansailor
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    bajansailor Marine Surveyor

    I found this link with Google -
    Interesting Sailboats: VIRGIN MOJITO 650 http://interestingsailboats.blogspot.com/2020/11/virgin-mojito-650.html

    Here is a quote from it :

    On a small cruising boat, more than on a bigger one, it makes sense to maximize hull form stability and interior living space and that's what Mojito 650 is about. But its hull is not only designed to maximize space but also to offer maximum performance downwind. It is the one of the Maxi 650, the mini-racer that is a winner in the mini-class races.



    [​IMG]
    There are differences, starting on the displacement, 950kg on the racer, 1200kg on the Mojito and on the sail area that is (upwind) respectively 44sqm and 38sqm. The keels are different too, a torpedo one on the racer and a swing one, with all the ballast on the keel, on the cruising boat even if this one can also have the racing keel.

    It has a 1.60m draft on the fixed keel and 0.80/1.85m on the swing one. The superior area upwind on the racing boat, on a lighter boat, indicates a bigger B/D but both boats are certified as class C boats. That is not a good reference in what regards final and safety stability. Unfortunately, neither IDB neither David Raison, the designer, disclose the ballast in any of the boats.

    It is very difficult to reunite on such a small boat the qualifications to have it certified as a class A boat, but not impossible as the Mini-racer Pogo3 demonstrates. I find odd the Virgin Mojito 650 not to be certified on at least Class B and certainly if I was interested in buying one I would certainly want to know more about the boat stability, particularly about RM at 90º, final stability, AVS and downflooding angle.

    I have no doubt that the overall stability, due to the huge beam (3.0m) and the shape of the hull, with its rounded bow, will be a good one for a hull with 6.50m length, and I have no doubt that it will have an excellent performance downwind, a very good one while beam reaching and even a satisfactory one upwind with the deep swinging keel (1.85m) help, at least on a flat sea.
     
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  10. Will Gilmore
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    Will Gilmore Senior Member

    I like the idea. The boats you might look at for ideas are sandbaggers.
    upload_2021-8-26_21-2-28.png
    upload_2021-8-26_21-3-3.png
    A monohull won't behave like a catamaran because they don't straddle waves, their centered buoyancy picks them up and they will roll more than a cat in some sea states. They also have more surface area in the water, but they might be made to plane pretty easily with the right bottom and sail plan.

    -Will
     
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  11. John Smithson
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    John Smithson Junior Member

    Thanks for pointing me at sandbaggers. I looked it up and apparently they have quite the history (as workboats and top racers before rules forced them out). Pt 1.4: The Sandbaggers https://sailcraftblog.wordpress.com/2016/05/23/519/

    I also like seeing how beamy with centerboards were used so much for work (the sandbaggers and the catboats). Which makes sense with their more shallow draft and capacity for weight / cargo. I tend to think you can tell better what a good boat is by what people actually use, and not just by what rich people play with.

    The more I read about the history and beamy boat usage, the less crazy of an idea I think something like this is. Combine it with the history surrounding coracle use in india and other parts of the world and there is a lot of room between those extremes of beam ratios depending on the need. But the idea in general of wider beam doesn't seem doomed from the start at all.

    I keep hearing people say "wide beam = slow" or that it isn't practical, but history keeps showing that it isn't necessarily true.
     
  12. gonzo
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    gonzo Senior Member

    Sanbaggers carried a crew of burly men that shifted their weight along with the sandbags on each tack. It does not seem to be a good design for cruising shorthanded.
     
  13. John Smithson
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    John Smithson Junior Member

    For extreme racing sail plans... but sandbaggers were also used as just normal work boats.

    Though taking advantage of a very wide beam with some type of dynamic ballast isn't a bad idea. Maybe a water ballast system? Putting tanks on each side and making use of the favorable hull design.
     
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  14. gonzo
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    gonzo Senior Member

    Sandbaggers were pure raceboats. Workboats did not have the crew or the available space. The working boats had interior ballast that could be moved to trim them, but the design was much more moderate.
     

  15. Peter Belenky
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    Peter Belenky New Member

    Sandbaggers were close to catboats in evolution. They were New York workboats that shifted a modest sloop rig to an even more modest cat rig in winter. Then racing led to larger rigs, larger crews, and shifting ballast. The same thing can be observed in New England cats (minus the sandbags). Also Chesapeake Bay log canoes, Bermudan and Australian dinghies, Dubai dhows, International 14s, etc. The factor used to handicap the competitors and the technology permitted by the rules determined the elements that would be exaggerated to the point of impracticality for other uses and even danger.

    Whether for cargo, crew, or ballast, the beam of some of these classes is as much underwater as on deck, providing the buoyancy to support the weight as well as righting moment. Apart from everything else, is the convex protrusion of the bottom in the sketch supposed to represent the total immersed volume? If so, the topsides, deck, and superstructure would have to be made of feather pillows.
     
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