Flat bottom/vertical sides/flat deck/ flat everything

Discussion in 'Sailboats' started by Ron Cook, Apr 3, 2009.

  1. Ron Cook
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    Ron Cook Junior Member

    Wetted suface

    Paul my calculations are correct the round section boat is a contemporary rounded U section design. I did double check. And it will go to weather just fine. Things are surprising some times.
  2. Paul B

    Paul B Previous Member

    If you are happy with your calculations I will not argue. Your note that at 15 degree heel you have the same LWL for both shapes tells me something. It should indicate something to you as well.

    I can't think of any modern rig that would be worse than the rig you show for upwind sailing through a variety of conditions. I hope you are not basing your beliefs on some anecdotal comment attributed to Bolger about his version being better than all the other boats upwind.

    If he did if fact say such a thing that would be more reason to discount everything he has ever claimed.

    In the end it is your design and success or failure will be based on your criteria.
  3. Ron Cook
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    Ron Cook Junior Member


    Paul I base my interest and conviction on first hand knowledge of the corsair 24.
  4. Gary Baigent
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    Gary Baigent Senior Member

    "Designs like this really confuse me.

    The only raison d'etre for an Open 60, Open 40 is to win races.

    The design shown would not be competitive in the class.

    So why would such a design exist?"

    Paul, I agree that to build a 40 or 60 foot yacht like the Tanton would be a huge amount of work for a result that would not come near state of the art versions - but relatively speaking, this would be less powerful (less sail area, less beam) but somewhat cheaper to construct than the sota - and that might be the reason Tanton drew it. Also it could be built by amateurs because the hull shape is simple and less sophisticated. IMO it is way superior to Ron's box (and its horrible rig, sorry Ron) but both designs are aimed similarly towards moderate performance, "moderate" expense and construction ease. And the Tanton would still be a fast boat, relatively speaking again, to moderate past and present displacement designs. Your thoughts?
    Here is a kiwi 40 foot cruising, centreboard design (with internal ballast) by Sandy Mill who also built it himself, that is multiple chine construction and based on (but with greater beam proportionately) the Yachting World Diamond hull cross section. This hull is cuts of straight lengths of quite heavy ply - and has already been around the world.

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  5. Tanton
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    Tanton Senior Member

    (Paul B.).Such as it is, the design above is from 1995. From an 1/2 size prototype model built in 1992. Fast to built and fast on the water. By presenting the design, I was mostly interested in promoting a shape, competitive at the time, even as an Open 60, with a simpler , less expensive method of construction for the hull and deck.

    (Ron Cook). Wetted surface is 438sq/ft. @ 15Deg. on the new model below.
    Fast boats pound. Real fast boat pounds more. Open 60, are horror show going up wind with any seas. Vendee Globe is race that is mostly downwind.

    (Garry Baigent) Yes, it was quite a few years ago, and the hull shape looks simplistic. I am showing, preliminary only, what could be a newer model. My thoughts are that in the Open 60 Class, huge leap has been made. Thanks to : carbon fiber for construction, swinging keel, turning mast and above all; total professionalism driving very powerful boats. They still go badly upwind. They pound!

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  6. sharpii2
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    sharpii2 Senior Member

    Actually, Paul, if you look at it carefully, sailing downwind might be this rig's Achilles heel. I could imagine it having terrible down wind course keeping characteristics. I could see it having quite a tendency to round up into the wind. That would be due to the somewhat side pull of the jib sheet and the windage of all the rigging so far aft.

    Going upwind, you need a light bow and a great deal of initial stability, which, if anything, Ron's boat would have. Going upwind, I can imagine it pounding considerably less than the market variety open 60, with any strength in the wind.

    Going up wind in a light breeze and a rolling swell would be a whole different matter. There, the rounded bottom would shine.
  7. CT 249
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    CT 249 Senior Member

    PAR, with respect it seems very difficult to believe that your boat would plane upwind efficiently. From the looks of them the current carbon canting 98s don't plane upwind, and the couple of times I sailed them the pre-canters like the carbon 80' R/P Shockwave/Alfa Romeo or the Simonis/Voogd Nicorette (83', water ballast) didn't plane upwind.

    Much as I love Ragtime, the skinny 65-70 footers aren't as fast as the fatter TP 52s, and nobody's claimed they plane upwind. After all, planing can be slow - there's been a long term shift away from maximising planing lift in skiffs for about two decades now as designers have found that reducing wave and wetted surface drag gives better results.

    Maybe the simple hull concept CAN work, if it's tied in with simplicity everywhere else. Build a simple ply hull, chuck on an ex TP52 or IACC rig and keels and second-hand gear and you could have a cool boat for not a lot of bucks (comparatively speaking).....although getting a high-tech rig to work on a bendy hull is another problem.

    Ron, I understand the appeal of roller furling, but why not just have a fully battened main (a la Moth, A Class cat, windsurfer and all the other really efficient machines) and lazyjacks?

    Can you point us to any on-line info about the Bolger boat and its performance against similar craft? I have to admit, I find some of his marketing is a little bit off-putting, but on the other hand I want to turbo a Folding Schooner before I die!
  8. diwebb
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    diwebb Senior Member

    Blondie Hasler produced a 46 foot design with many similar characteristics, to the 60 footer that is the subject of this thread, to compete in the 1966 two handed round Britain race. She was called Sumner. She was very narrow beamed at 6.75 ft and only drew 4 ft of water. She had twin fixed bilge keels and a skeg mounted rudder. She was originally Bermudan rigged but was later changed to single Chinese lugsail on a free standing mast. A sketch and short write up is included in the book Practical Junk Rig by Hasler and McCleod. She aparrently did some extensive offshore cruising ,after she left Haslers ownership, by a paraplegic French sailor and his wife and young family.
  9. Paul B

    Paul B Previous Member

    Doing something like this would have been a waste, just like the weird cat-ketch, done by a designer who posts on this board, and the skinny freestanding rig boat that represented the last American Open 60 to finish Around Alone.

    If the idea is to make some cheap thing then don't try to claim it to be a competitive Open design. Call it something else. Even so, building something like this, might as well put in a bit more effort and/or cash and do something better.
  10. Paul B

    Paul B Previous Member

    I can't think of any point of sail where this would be the rig of choice.
  11. Tanton
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    Tanton Senior Member

    Flat, flat. Everywhere.

    The 4M. (13'). "Bee" boat 1975 prototype. TYD#756.

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  12. BWD
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    BWD Senior Member

    Genial, Tanton!!
    Regardless of how fast it sailed!
    Curious what the big batten was made of?
  13. Tanton
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    Tanton Senior Member

    Made of fibreglass. One can control the bend by applying more or less material.

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  14. peterraymond
    Joined: May 2009
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    peterraymond Junior Member

    flat everything

    Well, this thread has been quiet for less than 2 weeks, so I'll jump in. A long time ago I sent emails to the AYRS mailing list, but I haven't had much of a internet sailing fix since.

    Really nothing is fundamentally new in sailboats, but advancements in knowledge and developments in one area are still changing the best solutions in others. I don't know if this will be the case for your boat, but maybe.

    I would suggest taking advantage of the experts on this forum. Doing that makes the design part of the boat safer and easier and can improve performance and lower cost. But having said that I'll give some non-expert advice.

    - You need some way to get the sail out downwind. A jib boom mounted to the deck does sound good.

    - Stick to a design with no complex curves. This makes it easier to lay out panels that will smoothly come together on your frames.

    - You have been told that your rig will be no good upwind and no good down wind. I think it's worth trying. I might suggest adding a roller furling staysail. On a long tack in lighter wind it could be worth the effort to hoist. In heavy air you could furl the jib and just use the staysail, or use a scrap of each. Does kind of conflict with adding a jib-boom though.

    - I have always thought that long and thin was interesting. If you double the length, but don't change the beam, it seems to me you can go the speed of a longer boat with less sail area to work and pay for. If you are designing for single-handing, you don't need a lot of room below. Wide sterns are great downwind, but I think that kind of boat is a little intense for general sailing. I think you want to maximize speed per dollar, not speed for a given waterline length.

    - I'm wondering if a very narrow hull could be combined with a canting keel. Forget about form stability and like a moth, depend on moving the weight to windward. I sort of think of a single catamaran hull, but with the keel bulb to windward, not a second hull. If the beam is narrow enough, hull speed is much less of a limit, so you could maybe reduce the length of the design.

    Canting keels are of course more complicated and more work. You might want to do a form of roll tacking to reduce the work. Let the boat heel a lot by slowly releasing the keel, then at the extreme heel re-lock the keel and tack. A canting keel and a very narrow hull would never get stuck upside-down either. Another advantage? You can tune the heel angle to reduce pounding and to let gravity help shape the sails in very light winds.

    I don't know about shallow water and putting the boat on the sand at low tide. You might be able to tilt the bulb all the way over and settle with the keel flat on the sand and hull tilted. Not great for sleeping at low tide, unless your bed tilts too. A deep keel would be nice, but a canting keel that you can raise for sailing in shallow water? An opportunity for innovation.

    - I would not go with straight sides, but maybe flat top and bottoms. A V-bottom might not make that much difference in a very narrow hull, but some angle on the sides will at least look better, people will admire your boat and you will be prouder of it. Of course if it really is very narrow, maybe vertical sides will look fine.

    For tight, or busy waters I'd reduce sail, lock the keel in the middle and leave the sail self tending. For longer distances I'd power the boat up more and enjoy the speed.

  15. Guest625101138

    Guest625101138 Previous Member

    I was one who thought nice rounded curves were important on a hull until I got hold of Michlet and started doing comparisons.

    I have recently built two hulls designed for the same purpose. They are not sailing boats but are designed for best speed for a human engine over long periods.

    One is the absolutely optimised shape for 12kph at 150W. It has rounded sections and little rocker. The other is hard chined for simple construction from 4 flat foam sandwich panels. It is optimised within this constraint for 11kph and results in a good amount of rocker. (I do not know why this happens)

    The simple method of building the hard chine saved weight and considerable time - the whole hull, including making panels, took 38 hours of effort. The hull weight advantage of about 30% was allowed for in the design. Overall this gives it a slight performance advantage at 11kph - at least in theory and too early to tell in practice but seems likely.

    In initial testing the hard chine requires about the same power at 11kph, more power from 12 to 15kph but gets easier above this and will probably have a higher speed once the engine is back in tune. I figure the higher top speed is a result of lift with the rocker and flat bottom.

    The carbon fibre panels are only 3mm thick foam but still very stiff over the short spans in this hull. I have not calculated it but similar stiffness to 1/4" ply.

    Now to the point - Water does not seem too bothered about negotiating an edge. When you look at the transitions they are very small angles anyhow.

    There is no doubt a lot of opinion is formed from experience, highly tinged with proven practice, rather than being based on curiosity and actual knowledge.

    I think there could be slight improvements to the slab sided sailing hull proposed but I cannot see anything wrong with a hull simply built from 4 large slabs of foam cored panels.

    These hulls end up so light that the greater concern is actually being blown away. They are as much aeroplanes as boats.

    Rick W

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