New to cats

Discussion in 'Multihulls' started by davekf, Feb 17, 2009.

  1. robherc
    Joined: Dec 2008
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    Location: US/TX

    robherc Designer/Hobbyist

    Your cat heels too, just in a different way than a monohull. In a cat, you have to watch the hulls. The more heeling moment, the deeper the leeward hull submerges, and the higher the windward hull rides. With experience, you'll learn how to gauge when you're about to fly the windward hull & need to reef. Until then, play it safe 'till you're comfortable enough with the boat to test that limit. :p
     
  2. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    front space use

    Starship Moonbeam 24’

    [​IMG]

    http://www.starshipcatamarans.com/html/moonbeam_24.html

    Angélique.
     
  3. SunKing
    Joined: Apr 2008
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    Location: Florida, USA

    SunKing New Member

    Hello, I thought that this group here might help. I am looking for a 25-35 foot express sailcat. the problem is, I cant find one in the States at least not what I want. So hear me out and please give me any ideas.

    I dont need bluewater, I am on a large river. I currently own a 26' Twin Vee. I know that motor and sailcat hulls are entirely different but I like the platform. i dont need a salon but prefer a large covered cockpit rear. I like an elevated wing deck for visibility but I dont need to live in the hulls. maybe some berths, potty, stowage but thats it. It is just a day cruiser primarily with the ability to camp out. A party boat mostly.

    I am CHEAP. I dont want to build anything from scratch but a kit or a rebuild of a wrecked vessel would probably be better. I am in the marina business so I have access to carpenters, glassers, mechanics, etc. but i am mainly looking for some ideas. Thanks!
     
  4. mdcf
    Joined: Mar 2009
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    mdcf Junior Member

    I'd be interested to know why this sort of design is not seen on cruising/racing cats, you could potentially regain more volume in the interior - similar to a tri but only have two wetted hulls. You'd avoid the rocking motion of a tri. It seems odd that high speed powered cats are off in this direction, whereas high speed sailing cats are going in another.
     
  5. catsketcher
    Joined: Mar 2006
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    Location: Australia

    catsketcher Senior Member

    Been done

    Hello

    The idea of a cat with a large centre pod much like a flying hull was designed and built in the 80s I think. It was a well designed attempt by Dereck Kelsall and sponsored by VSD. It was not taken up by other designers.

    The use of a nacelle to store fuel or an engine, give headroom etc is still done. There are problems. On my single motor cat I like the engine nacelle to be raised when sailing so that it doesn't slap the water.

    You can learn a huge amount by seeing the mistakes of the past - try getting your hands on a heap of old mags and see the evolution of the modern cat. They are the way they are for a reason.

    cheers

    Phil Thompson
     
  6. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    mdcf

    It would be interesting to see a "3rd bow" as such, like on the Wavepiercer. However the reasons for the 3rd bow on a high speed cat, would be very different from that of a sailing cat.

    Especially considering that in the private/luxury market is more prone to a clients "individual" personal stamp on the design than one gets in the commercial field. A mans "dream" may be another mans "nightmare"...!!
     
  7. mdcf
    Joined: Mar 2009
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    Location: New York

    mdcf Junior Member

    Thanks,

    I can see that rounded nacelles would give rise to a slapping, what strikes me with the large power cats is that they use a very sharp entry, I guess to reduce the effect of the slapping, they apear to the eye to be sharper than is typically used on a deep V hull, I guess driven by the fact that they don't have to get the boat onto the plane. The other feature that is seen is the notched entry in the two hulls, where the submersed hull extends forward of the entry point of the hull. I was wondring if anybody has an explination for these features.

    Mike
     
  8. mdcf
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    mdcf Junior Member

    So true,

    for what different reasons whould they differ between a power cat a sailing cat?
     
  9. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    mdcf

    Well, that is a very subjective and a personal reply, only the owner of "their dream" can answer that.

    But referring to the 3rd bow on the wavepiercer.
    When the wavepiercer concept was developed and tried in Sydney many years ago, all seems well. Long slender hulls, "cutting" through the waves. Just low buoyancy and smaller water-plane area so the motion created by waves is minimised. The early designs used long slender hulls, so their L/B was high. Longer more slender vessel, all types, have lower vertical accelerations, that's nothing new.

    However during a routine sailing, with a passenger carrying wavepiercer, can't remember the exact date late 1980s i think it was, in a large following quartering sea the stern was lifted and the lack of buoyancy up fwd made the hull 'submerged' and create a very large angle of heel. The vessel stopped suddenly and nearly capsized. The raft structure/superstructure buoyancy was what ultimately that saved it. This is what is now termed bow diving or deck diving.

    So, the 3rd bow was introduced to prevent deck/bow diving. The 3rd bow regains the 'lost' buoyancy from the slender hulls up fwd.

    However the hull variants since those early days are no longer truly long and slender as they once were. So the 3rd is more "marketing" tool, to say it is "safer", even though it does now aid as a bow door on the RoRos.. Just raising the freeboard at the bow does the same job!
     

  10. mdcf
    Joined: Mar 2009
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    Location: New York

    mdcf Junior Member

    Thank you for taking the time to answer, that is a great history lesson.
     
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