Mini Cat Transat?

Discussion in 'Multihulls' started by Alex.A, Feb 12, 2010.

  1. Fanie
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    Fanie Fanie


    You US guys can only be glad it wasn' done by one of us. In metric meters the boat would even have been smaller ;)

    Will keep you posted Alex.
  2. Hisflyingtune
    Joined: Feb 2010
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    Hisflyingtune Hisflyingtunesmith

    Unit of Measure

    Are there other kinds of meters beside metric meter?;) I mean, I was gonna post length in cubits and weight in either shekels or stone.;)
  3. Bob Oram
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    Bob Oram Junior Member

    small ocean going cats

    I have been mid ocean on a few occasions and thought to myself 'why do I have such a big boat when something considerably smaller would be just as adequate'
    For my own interest I am drawing a 10mt version of this boat, although there will be some changes to the cabin profile.
    There are some big provisio's with this style of boat.
    You need enough experience offshore to be happy to be very conservative.
    In benign weather it will be 10% to 30% [it depends on apparent wind] faster than a good mono of equivilent size.
    This introduces the whole question of whether it is a worthwhile excercise or not.
    Drogues and para anchors are essential not optional.
    The user must have deployed and retreived them repeatedly in friendly conditions ready for the 2am in 70 knots deployment.
    Naturally water ballast is essential with easily accessed controls with only mechanical controls no electrics, [they fail at the most inopportune time].
    The boat should have a very protected central cockpit so the crew can stay warm and protected form the elements including noise which can be very distressing at any time but especially when one is tired.
    The better the crew protection the less fatigued they will become therefore the better decisions they will make.
    I think it is safe to say that a hell of a lot of preventable mishaps where caused by bad decision's made by fatigued crews.
    I have considered various rigs and none are yet cast in stone as they all have advantages and disadvantages.
    I feel a freestanding carbon mast with a mainsail only would be safest and offer acceptable performance.
    It would be quite easy to run a light weather drifter to get the boat up to a 1.6 performance no.
    It is in these conditions [under 8 knots of real wind] that a light very easily driven cat comes into its own. The enormous buzz derived from sailing at 1.2/1.5 wind speed also adds to the overall justification for such a boat.
    The other safety factor with this style of boat is having the ability to lower the rig in extreme condition's.
    With the rig down and water ballast it then becomes quite a big stable platform.
    Because of the light weight they actually make very accomplished power boats as well. A single 25hp 4 stroke outboard in the middle will return 10 knots at 4 lts pr hr.
    On the 40' and 50' a single 21/29hp diesel centrally mounted running a long tail will return 8 knots at around 2 lt pr hr.
    I am hoping to start my 40' Slim this year.
    Bob Oram
    1 person likes this.
  4. Hisflyingtune
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    Hisflyingtune Hisflyingtunesmith

    Hi Bob,
    Thank you for your response to my thread. Let me be quite open. I don't want to put on any airs. I'm a rank amateur and completely new to anything other than chartering the periodic off shore fishing trip, water skiing, and growing up along the Chesapeake Bay. I fished and crabbed as a kid outside of suburban Baltimore and have had a profound love for the water. It is only recently that I have discovered just how "easy" it is for anyone to design and build a boat. Designing and building one's own boat is clearly superior to anything that can be purchased for more reasons than time and space will permit here. I imagine that I'll build two: a skiff and a pocket cruiser. I positively love the old Chessie Bugeyes but, that nostalgia costs. A smaller simpler rig will do the same. As I am a 51 year old bachelor who is also an unemployed school music teacher, I have time to dream.

    All of that is to say this: I am absolutely fascinated and consumed with all aspects of design. I'd like to follow along on someone's design process and learn along the way without getting in the way. I don't have the financial luxury to go to boat design school although I would lunge at such a chance.

    Your motor-sailer sounds like the best of all worlds. Will you be designing this
    for single hand sailing or for more than a crew of 1? I definitely resonate with your idea that all controls should be manual as electrics do fail at the most inappropriate times: (Just ask this pilot of single engine aircraft!) I heartily approve of the idea that this will be a cruiser and not a floating patio for sipping martinis on weekends at the marina.

    Also, I do have an idea for enhanced outboard power (15hp) using polyamide-imide parts. I know what it is that I want to do but, I'm having trouble contacting the fellow who would make the parts. If my arithmetic is correct, it will maintain 4 to 5 kts @ > 1 ltr/hr. I mention this because of your intention to use a carbon mast. The weight reduction and torsional stiffness is clearly superior. Obviously, you've got loads of experience and you've done your homework. Your attention to safety and the natural environmental fatigue factors really piqued my interest.

    Feel free to contact me at my e-mail address:

    I spent 12 years teaching in South Korea. Both the Koreans and the Japanese have working boat hull designs for exceedingly heavy seas. Have you considered the novelty of using such a design? What materials do you plan to use for the hull. I'm looking at Nidacore honeycomb. It's weight and structural properties as well as its ability to absorb sound and tremendous punishment has got my attention. However, it's chemical make-up and potential/long term toxicity or lack thereof are unknowns to me at this point. Also, I don't know if there is any weight advantage or penalty when compared to wood construction. But, according to a boat building friend of mine, he swears by Nidacore. I simply don't know enough about it yet but, it looks to be quite economical and lends itself well to multi-hulls with compound curves.

    Again, Bob, thank you for your response and for entertaining such a green horn as I.
  5. Alex.A
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    Alex.A Senior Member

    Moved to new thread on minimal cruiser - minitransat doesn't seem viable - unanimous!!!
  6. Hisflyingtune
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    Hisflyingtune Hisflyingtunesmith

    OK. Now, I have a question of keels. In an effort to keep ballast weight to a minimum and, in some conditions, eliminate internal ballast altogether, is it possible to use a fin/bulb keel in combination with bilge keels. Yes. That's
    THREE (3) keels with the associated drag. The idea is to trade off some hydrodynamic drag for the ability to eliminate internal ballast, added stability, and add more sail area. Does anyone know of anyone who has modeled such a combination of keels and if the such results have been quantified?
  7. rayaldridge
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    rayaldridge Senior Member

    Just to throw a little gasoline on the fire, I was reading the new Small Craft Advisor, which has a piece about Ant Steward, the first man to sail around the world in an open boat. This was a lightweight 19 footer with a pretty big rig. It's a story of miraculous survival-- he capsized numerous times, lost his rig a couple of times, was wrecked on a desert island, from which the boat was shipped back to SA for repairs and then returned to the island so he could continue (s it really a circumnavigation?) was almost run down a couple of times, and so on, a whole list of semi-disasters.

    Contrast this with the circumnavigation of Cooking Fat, a Wharram Tiki21. No fuss, only occasional drama, just a good, well-executed voyage.
  8. GTO
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    GTO Senior Member


    What does such a comparison actually tell anyone?
    This ties into the mini-cruiser thread, too, by the way.

    Boats of all sizes have crossed the oceans successfully, from 5 feet upwards.
    Boats 60 feet and larger have sunk/disappeared, as have some of the smaller/tiny ones.

    The best that I can deduce from all the information I've come across is that, yes, a bigger boat is definitely safer/more stable - but no matter what size the boat, there is something out there that can make you disappear.

    For me, that "something" is what drives the debate, the search for the magic numbers. For now, there really doesn't appear to be any truly safe boat. Varients of all kinds have gone down.
    That said, I believe that if I end up in blue water on a multihull, it will be something with similar or better stability numbers than Commander Tetley's Victress. That boat was stable enough absorb forces that broke it up, but without capsizing it (although it did come close twice, see A Voyage for Madmen, Peter Nichols).

    It's not the greatest yardstick to use maybe, but no one really seems to offer up anything better.
    Surviving the southern ocean has to mean something, doesn't it?
  9. rayaldridge
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    rayaldridge Senior Member

    I probably should have done a better job of explaining what I was getting at. I was comparing two boats of roughly similar size, and the point I was trying to make is that while it's true that catamarans can capsize, an oft-overlooked fact is that it takes a lot more energy to capsize a cat than a monohull of similar length.

    Of course, it takes a lot more energy to capsize a big cat than a small cat, but other factors play into the analysis, in my opinion.

    Most folks will tell you it's not safe to cross oceans in small multis, because large multis are so much more stable, and a capsize is a certain disaster for a cruising multi. I think there's a lot of evidence to suggest than this does not make small multis unsafe, it just means that big multis are extraordinarily safe.
  10. ThomD
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    ThomD Senior Member

    Bob. sent you an email on Slim, via
  11. ThomD
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    ThomD Senior Member

    I think you have to break the dissection down into parts. Say Survivalbility, comfort, load/cruising vs. tripping, etc...

    Survivability. For me the current benchmark is the ocean rowers's boats. There are a fair number of them out there. The current center cockpit sealed ends format is a lot like a traditional Newick Val. Of course the need to deploy oars is part of all that. But that size envelope gives you an idea of the reasonable platform for ocean survival. Row boats take their time, so they need a lot of food, while sailboats should be faster but need to accomodate a lot more stuff like masts.

    Survival is really all about having an integrated platform. Why did Jones' Two Rabbits survive a hurricane while a much larger sail boat went down? Luck obviously played a part, but Wharram has always been motivated by ultimate survival issues. And Jones had modified his boat to make it even more seaworthy. A boat that can't be sunk, can't be swamped, very low risk of capsize and capsize is not fatal, appropriate storm strategies are integrated like drogues and paras, storm sails, anchoring gear, whatever. Having the whole thing organized as a piece is the key issue. There are a lot of boats, the majority really, that have given no thought to such things, and will never venture offshore. Size is very much less important than integrating everything to the intended use.

    Comfort is a big topic. But one item is the whole question of whether the boat in has a cockpit. My feeling is that the single most important seaworthiness design feature for a small boat is that it have no in-hull cockpit. Boats from Jester to Laden's sharpie Paradox, to Jones' Hummingbird all do away with the cockpit and encapsulate as much space as possible. This dramatically improves the chance the boat will not swamp. Also maximizes interior space, displacement, and aero. The organization of a sail that can be controlled from inside like Jester is much harder to do, but has obvious advantages where possible. Elimination of the cockpit, when implemented to it's full extent, makes sailing an indoor sport. And certainly it can make the boat so designed a less comfortable platform to live on, though multihull deck space can reduce the compromises.

    Whether the boat is designed for long term cruising or tripping where the emphasis is on voyages, not arrivals, will have a large effect on how big it needs to be and what shape it should have. I am interested in the tripping/touring format where the idea is to make voyages not lounging around trailer park like. A boat that makes easy speed has superior survivability, is very easy to sail, a boat designed to command the environment rather than anchorage. Possibly containerizable is an interesting project to me.
  12. Alex.A
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    Alex.A Senior Member

    sorry- being daft.....
    Like the thinking....
    Last edited: Mar 16, 2010

  13. jamez
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    jamez Senior Member

    Hi Bob, your 40 and 50 'Slims' are innovative and I feel could suit a lot of cruisers who aren't tied into the mainstream.

    Would like to see a pic of the 10 metre version you mention.
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