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Thread: Wavepiercing Bows on Catamarans

  1. #1
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    Default Wavepiercing Bows on Catamarans

    Since seeing Francis Joyon's trimaran "IDEC" bowling along at high speeds I have become interested in wavepiercing bows on cruising sailing catamarans.

    So far I have only come across a handful (from top left in below pictures):
    - "Zephyra", a homebuilt 15m cat
    - "Victorinox", a KKG built 15m cat
    - "Wahoo", an Australian (?) 16m (?) cat
    - a Norwegian cat of 11m.

    Does anyone have info on more and pictures thereof?
    Attached Images Attached Images
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  2. #2

    Default Re: Wavepiercing Bows on Catamarans

    Good spotting, haven't seen that on sailing cats.

  3. #3
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    Default Re: Wavepiercing Bows on Catamarans

    Wahoo was a crowther design and a number of loch's boats had slanted and tulip bows, a fair bit more expensive to build, so thats why you dont see them on production boats.

  4. #4

    Default Re: Wavepiercing Bows on Catamarans

    Those look more like bulb bows to me. They work very well on ships, they reduce bow wave propagation and thus drag.

    But AFAIK they have to be designed to work at a specific speed - which is fine for a motor driven ship, but not so useful on a sailing boat who's speed is heavily dependant on windstrength and point of sail, and so highly variable.

  5. #5
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    Default Re: Wavepiercing Bows on Catamarans

    44C,

    I would think the bows of both "Victorinox" and the Norwegian cat in my pictures are not bulb bows (which were also tried on some Prout cats) but clearly forward hull extensions without the weight of the hull material. I think this is a clever way of achieving a longer waterline thus more speed and having the wave seperated before it reaches the actual hull and thereby most probably also reduce spray.
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  6. #6
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    Default Re: Wavepiercing Bows on Catamarans

    Does the Schionning G Force count as a wave piercing bow?




  7. #7

    Default Re: Wavepiercing Bows on Catamarans

    Victorinox looks like a Novara 44 with an entirely diffrent below waterline hull glassed on. Looks really strange out of the water.

  8. #8

    Default Re: Wavepiercing Bows on Catamarans

    Geoff Schionning has designed a number of his G Force cats with a reverse bow and Tony Grainger has now got in on the act with some of his new designs.
    I think I recall Tony (or maybe someone else) making comment that the design reduces weight in the bows, but decreases reserve bouyancy if the bows are pushed under.

    The G Force cats are very quick, but then they were designed with a very long narrow waterline and good sail area, not sure how much impact the bows had.

    Peter

  9. #9
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by spiritcat View Post
    Geoff Schionning has designed a number of his G Force cats with a reverse bow and Tony Grainger has now got in on the act with some of his new designs.
    I think I recall Tony (or maybe someone else) making comment that the design reduces weight in the bows, but decreases reserve bouyancy if the bows are pushed under.

    The G Force cats are very quick, but then they were designed with a very long narrow waterline and good sail area, not sure how much impact the bows had.

    Peter
    Morelli & Melvile also use reverse bow on crusing cats. Also a style thing.

    I think Crowther was first to use bulb bows on his cats but eventually went away from the concept.

  10. #10

    Default Re: Wavepiercing Bows on Catamarans

    I saw a crowther on the hard and the guy was fitting bulb bows by havind some say 150 mm plastic pipe cut to fit the hull and a plastic ball in the end. This was all glassed over. He said some story about the boat hobby horsed alot because the centre of bouyancy was too close to the centre of mass and this was the reason he was increasing the bouyancy in the bows.

  11. #11
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    Default Re: Wavepiercing Bows on Catamarans

    A little over 20 years ago Prout tried bow bulbs. AFAIK, it was a failure. I spoke to one boat owner who had them on his new Prout back then and he told the story of hitting a partially submerged shipping container one night while on a passage across the Indian Ocean. The collision tore the Port bow bulb off the boat. It was sacrificial, so no boat damage, but performance wise, he didn't notice any difference at all over thousands of miles, and in the end removed the starboard bow bulb himself.

  12. #12

    Default Re: Wavepiercing Bows on Catamarans

    Hello, Im Doug Prince (President and Founder of sailingmachines.com)
    I was involved w/ the Victorinox Project- from the design to the final delivery... Even had her up to 23knts... what do you need to know???

  13. #13
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by sailingmachines View Post
    Hello, Im Doug Prince (President and Founder of sailingmachines.com)
    I was involved w/ the Victorinox Project- from the design to the final delivery... Even had her up to 23knts... what do you need to know???

    Hello Doug, welcome. Good to see you here. As you can see above there is general interest in the bow line shown in the OP's original post.

    Did the different bow style cause a marked difference in performance? And if so, do you know why it is not generally adopted on all the new designs?

    Thanks

    Mike
    Nothing works on an old boat, except the skipper.

  14. #14
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    Default Re: Wavepiercing Bows on Catamarans

    Hi Doug,

    Welcome on board!

    Can you advise whether "Victorinox" is a lengthened Novara 44 as mentioned above or is in fact a new design by Dr May? Did the wave-piercing bows produce a faster softer ride through the water / waves?

    I am looking at having bow and stern extensions a la "Victorinox" fitted to my cat, currently toying with glassed-over foam as material.
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  15. #15

    Default Re: Wavepiercing Bows on Catamarans

    I fitted bulb bows to the floats on my Kelsall tri many years ago to copy Crowther tris. Made them out of plastic water pipe, foam filled and glassed on. Entirely sacrificial!
    In my opinion, (not scientifically measured), they reduced pitching somewhat and the bow wave was reduced when they were fully depressed.
    However they were often only partially depressed when they just created spray and probably slowed the boat down!
    Eventually I lost the hemispherical front of one of them. I temporarily replaced it with an alloy cooking pan!!!!!
    After that I removed them both and I suspect performance in light airs is improved, altho the Kiwi prop contributes to that!!
    in fact in the above pic, the port bulb is present and the stbd bulb is wearing it's alloy hat!!

  16. #16
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by 44C View Post
    Those look more like bulb bows to me. They work very well on ships, they reduce bow wave propagation and thus drag.

    But AFAIK they have to be designed to work at a specific speed - which is fine for a motor driven ship, but not so useful on a sailing boat who's speed is heavily dependant on windstrength and point of sail, and so highly variable.
    I agree.
    Currently concentrating on http://earthnurture.com .

  17. #17

    Default Re: Wavepiercing Bows on Catamarans

    Here's a bulb on a 50' tri that's for sale.
    Attached Images Attached Images

  18. #18
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    Default Wavepiercing Bows on Journey 46 LR

    It will be interesting to see how these bows work...in heavy conditions.

    http://www.multihulls4us.com/forums/...3&postcount=46
    Attached Images Attached Images

  19. #19
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    Default Re: Wavepiercing Bows on Catamarans

    Just to confuse the issue and hijack the thread, check this out:
    http://gcaptain.com/damen-launches-w...essels-seazip/

    They are called "Double Axe Head Bows" and are said to reduce the effect of waves on speed and pitch stability.

  20. #20
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    Default Re: Wavepiercing Bows on Catamarans

    I think wave piercing bows are meant to reduce the destabilization effects of hobby-horsing over wave trains, and bulb bows were intended to increase the effective waterline of vessels without increasing skin drag and construction costs of just building it bigger.

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