14' concept sailing W

Discussion in 'Sailboats' started by icetreader, May 2, 2005.

  1. icetreader
    Joined: Jan 2003
    Posts: 217
    Likes: 1, Points: 28, Legacy Rep: 12
    Location: USA

    icetreader Senior Member

    The passengers in W boats sit, ride and stand in them with one leg in each hull, with their feet reaching the bottom of the hulls. This provides good stability and control for sailing sitting as well as standing.
    -See details in US patent # 6871608.

    -Being just 3' wide but remarkably stable for its width, how much sail could such a boat carry?
    -Would such a boat require twin rudders or could a single rudder be enough?

    Yoav
     

    Attached Files:

  2. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 147, Points: 0, Legacy Rep: 2043
    Location: Ontario

    marshmat Senior Member

    A single rudder could be enough, of course, depends on size. It is usual to have one rudder for each hull on a cat though, and the boat depicted would certainly do better with two.
    How much sail.... does it have a centreboard? how heavy?
     
  3. CT 249
    Joined: Dec 2004
    Posts: 1,701
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    I'm curious, why is it more stable than a 3' wide scow type? Is is much more stable than a Sunfish? There's probably more volume out to leeward, but how much will that increase stability compared a Sunfish or Laser? They both require hiking, so if you don't want to hike you'll need a much smaller rig unless you are vastly more stable.

    There have been catamaran dinghies out here (Australia) where your legs go into the hulls for years, how'd you get a patent on it? We used to have one, they were great, but I would have thought they'd also bee prior art?????
     
  4. mackid068
    Joined: Feb 2005
    Posts: 857
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: CT, USA

    mackid068 Semi-Newbie Posts Often

    By virtue of 2 hulls, it's more stable. Additionally, I am pro the one rudder per hull connected by a bar a'la hobie cat rudder with a tiller extention looks like this:
    |(rudder)
    ----|
    |(rudder)
     
  5. CT 249
    Joined: Dec 2004
    Posts: 1,701
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    But what makes two hulls more stable, if everything else (ie disposition of bouyancy, C of G, metacentric height whatever) is the same as a mono? I think the answer is "nothing".

    Normally two hulls are more stable because they are a long way apart. In this case, with only 3' beam the cat is only as beamy as many monos so the buoyancy forces created by the lee hull may not be any greater than the buoyancy forces created by the lee side of a single hull of similar width - and most 14 monos are wider.

    In the early days of cats, when they were narrow, they fell over quite often. More stability is obtained by increasing beam; narrow beam = low stability. It's a very well known thing, ask anyone who sails small cats. A normal 14' cat is about 7' wide or so, not 3'.
     
  6. Skippy
    Joined: Nov 2004
    Posts: 568
    Likes: 1, Points: 0, Legacy Rep: 12
    Location: cornfields

    Skippy Senior Member

    CT 249: ... There's probably more volume out to leeward, but how much will that increase stability ... Normally two hulls are more stable because they are a long way apart.

    I ran into this problem in the thread a while back about a pump barge. The cat hulls have more volume away from the centerline, but for a small, specified heel angle, the monohull of equal beam will lose flotation on the high side all the way from the centerline out to the topsides. That includes both the area away from the centerline that corresponds to where the hulls are in the cat, and some additional area that in the cat is just open space between the hulls. The monohull has flotation there, and the change in displacement in that area means that its righting moment increases faster with heel angle. It's not a whole lot more, because we're talking about the region near the centerline, which has less leverage. But it is more. Likewise on the low side with increasing displacement/righting moment.

    So at small heel angles, the monohull is stiffer than the catamaran. Since the mono has more area in the water, it also has less draft. That means that at some point as the heel angle increases, the hull bottom on the high side will start to come out of the water, and the equation changes. Then the righting moment of the mono is pretty much maxed out. Meanwhile, the cat starts to catch up as more of the taller/deeper hulls rise out of and sink into the water, until both boats are balanced on one chine/bilge (mono) or hull (cat) on the low side. At that point, it's a question of the exact shape of the submerged volumes. Tall narrow AquaCat hulls might start to scoot back under toward the centerline, but rounder cat hulls should be slightly better at high heel angles than the wider, shallower submerged volume of the monohull.

    Other issues are that the cat doesn't plane, and the two bow waves will interfere with each other more, so there's less reduction of wave drag than with a wider cat. One advantage might be that because of its slight initial softness, the narrow cat should be more comfortable than the flat beamy monohull.
     
  7. mackid068
    Joined: Feb 2005
    Posts: 857
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: CT, USA

    mackid068 Semi-Newbie Posts Often

    I sail small cats a bit myself, but in this case, it seems that it looks stable if you keep the center of gravity low.
     
  8. icetreader
    Joined: Jan 2003
    Posts: 217
    Likes: 1, Points: 28, Legacy Rep: 12
    Location: USA

    icetreader Senior Member

    Stability etc.

    -Thanks Matt,
    W boats don’t need a centerboard since their straight and relatively deep hulls get the job done. The 10’ model weighs 56 lb without the sail -I think a 14’ model could weigh around 100 lb total if roto-molded from polyethylene. In composites it could weigh more or less- depending on the material used.

    -CT,
    Cats are more stable than monohulls of the same width because their buoyancy is distributed where it’s most productive in terms of lateral stability that is away from the boat’s longitudinal axis
    A W boat is more stable than other boats its size not just because of the fact it has two hulls, but also because of the means it offers the passenger/s to stabilize it. In order to get the full answer you can either read the patent on www.uspto.gov (pat. #6871608) or go to my website www.wavewalk.com to the “Ergonomics” page and other parts, or watch this demo movie of the 25” wide 10’ long W1 model:
    http://www.wavewalk.com/Stability%20-%20Jumping%20in%20the%20boat.WMV
    and/or watch this demo movie of the same model sailed standing: http://www.wavewalk.com/Sailing%20Standing.WMV

    I just got an order from a distributor in NZ, so in a few months there will be some W1 models (10’ paddle craft) to test in your part of the world.

    -Mackid,
    Thanks for the comparison with a Hobie cat :) -Coming from a Hobie sailor like you it’s a compliment that shouldn’t be taken lightly!
    I already installed a single rudder on a couple of W1 boats and I’m waiting for this #!@%^&*>* New England weather to go away so I can test them with the new 32 sq ft sail.


    Controlling lateral stability means you want to keep the boat from tilting too much (it can be bad in terms of directional stability) and from overturning in extreme cases.
    Keeping the CG low is one good strategy, and having a wide beam or two hulls at a great distance apart from each other is another good strategy.
    But when for various reasons your boat must be small and narrow a third strategy can be to use the passengers as “active ballast”. It is possible to achieve this by exploiting the natural capability we have to use our legs for stabilizing ourselves even in highly demanding circumstances. For example: when horse-riding with our feet in the stirrups, when riding a cross-country motorbike etc.
    When a passenger in a W boat shifts weight from one leg to another the effect is significant and yet controllable due to the fact his/her weight is applied by direct contact of his/her foot with the bottom of each hull, under waterline.
    The hull offers good resistance to the additional weight due to its volume, and doesn’t roll easily because of the water pressure on its side.
    Our legs are powerful and sensitive, and do a great job in shifting weight from one hull to another both quickly and precisely.
    Riding is the best position for that, but standing is a good position as well while sitting with legs forward is not as effective.

    -Skippy
    You can control wave interaction between the hulls by reducing the hulls' symmetry.
    I understand what you're saying about the planing capabilities of cats, but what if the twin hulls are flat at the bottom, like skis?

    This drawing shows a cross section of the 10' long and 25" wide W1 (yellow) and a possible 36" wide "dinghy" or "canoe" type W boat design. You will notice that the "saddle" in the middle can remain unchanged, and the bottom of the hulls can be flat.
     

    Attached Files:

  9. mackid068
    Joined: Feb 2005
    Posts: 857
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: CT, USA

    mackid068 Semi-Newbie Posts Often

    I like the 36" wide, but maybe you should try having a motor mount if it's for a dinghy purpose. Maybe, if you want it to be really sporty, have a tiller or a wheel steering with seating inside the hull (it sounds odd, but it, atleast in my mind, is a good idea).
     
  10. icetreader
    Joined: Jan 2003
    Posts: 217
    Likes: 1, Points: 28, Legacy Rep: 12
    Location: USA

    icetreader Senior Member

    Thanks Mackid,
    The motor idea sounds great, actually:D and with the right steering device you'll be able to drive it sitting (riding) or standing :)
    A smaller W with a powerful motor and hulls wider than those of the W1 would be fun too.
    Maybe I should sketch something and post it on the Powerboats forum?

    Yoav
     
  11. mackid068
    Joined: Feb 2005
    Posts: 857
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: CT, USA

    mackid068 Semi-Newbie Posts Often

    Go for it! Also, I'd advise checking out the Go-Kart seat on the Sea-Doo 3D, it's a good model for an interior seat with steering wheel and a motor, it ought to perform well in such a config.
     
  12. icetreader
    Joined: Jan 2003
    Posts: 217
    Likes: 1, Points: 28, Legacy Rep: 12
    Location: USA

    icetreader Senior Member

    Micronautics?

    Thanks Mackid,

    I'm not surprised at all that you're mentioning a PWC.
    This W "thing" calls for a wide range of interpretations and applications.
    It looks like the W approach has something to offer as long as it's a small vessel carrying 1-2 persons and nothing much besides that.
    I have a word for this field of "personal" boats that includes scows and dinghies, canoes and kayaks, PWC etc.: Micronautics :D

    Yoav
     
  13. CT 249
    Joined: Dec 2004
    Posts: 1,701
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    Ok, Icetreader, I should have worked out that a greater % of the volume is further out. That makes sense.

    Re planing. I've sailed a planing cat or two, there have been many, many, many attempts. They have not yet provided better performance all-round than a normal cat.

    My understanding is that the main problem is that efficient planing depends on having a wide surface, not a long skinny one like a cat hull. The skinny hull presents a low aspect ratio surface to the waterflow, and just as in rigs that's not very effective.

    Look at a modern Formula Windsurfer, about 2.6m long and 1 m wide. They are much better at planing at moderate speeds than a skinnier board, whether it's a long skinny board or a short skinny board.

    I also agree with you about the value of standing up, it's a very effective way to shift weight.
     
  14. Skippy
    Joined: Nov 2004
    Posts: 568
    Likes: 1, Points: 0, Legacy Rep: 12
    Location: cornfields

    Skippy Senior Member

    CT 249: ... a greater % of the volume is further out. That makes sense.

    Yes Chris, it seems to make sense. But as I explained in my post above, it's not quite that simple. Roll stability is determined by how much the boat's righting moment increases as the heel angle changes, not what the distribution of submerged volume is when the boat is upright. At small heel angles, a flat-bottom mono with the same waterline beam as the cat, will lose and gain just as much flotation near the bilges as the cats hulls do. In addition, the mono loses and gains a little more flotation somewhat closer to the centerline, which in the cat is just open space. So at small heel angles, a flat-bottom monohull is in fact slightly more stable than the cat.

    At larger heel angles, the higher bilge of the mono rises above the surface, and if the monohull doesn't have much freeboard, the lower rail starts to go under. Then the righting moment of the mono is maxed out, and the cat hulls continue to redistribute their submerged volume because they're taller. Eventually the righting moment of the cat "catches up" with the mono, and if the lower rail of the monohull does submerge, then at that point the cat will have more righting moment. But with a relatively narrow beam, that will be a fairly high angle, not necessarily an angle most people will want to sail at.

    [Edit: only applies if the bottom of the monohull is relatively flat.]
     

  15. mackid068
    Joined: Feb 2005
    Posts: 857
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: CT, USA

    mackid068 Semi-Newbie Posts Often

    Micro (as in small) nautics (as in water vessels or something of that nature)! Someone's coined a new term. So guys, what do you think of a PWC style version? Oh, by the way, Yoav, where do you primarily sell to (regions of the nation)?
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.