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Thread: Wavepiercing Bows on Catamarans

  1. #21
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    Default Re: Wavepiercing Bows on Catamarans

    I am late on this topic, but this is even more a trend. Also the squared head sails (voile corne) .
    In my mind, the idea is to go on a straight line and get the thing out of the water friction being the no 1 adversary for performance. Also the flat bottom hulls is to be questionned. One interesting design is the Toro catamaran. It is often a question of where, when and for what are we using the hulls. In shallows, i will prefer reversed bows. The next AC cup will be a good show, it has been so far.

  2. #22
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by multihullsailor6 View Post
    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?
    Just posted the info I got on that last boat you mentioned,...over HERE
    http://www.multihulls4us.com/forums/...3&postcount=16

    Close up of bows...
    Attached Images Attached Images

  3. #23
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    Default Re: Wavepiercing Bows on Catamarans

    Visualize running downwind two of these bulbs stuck out in front of your boat - it seems obvious to me that bulbs would increase your chances of pitchpoling, if your bows get depressed to the point here there is a downward thrust onto the tops of them. Remember, the mast and sails are like a giant lever with a giant hand on them, trying to capsize or pitchpole your boat. You don't get that effect from the M&M style reverse bows. (The downward thrust effect on bulbs, I mean. The giant lever effect is intrinsic to sailboats flying sails.)
    Currently concentrating on http://earthnurture.com .

  4. #24
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by BigCat View Post
    Visualize running downwind two of these bulbs stuck out in front of your boat - it seems obvious to me that bulbs would increase your chances of pitchpoling, if your bows get depressed to the point here there is a downward thrust onto the tops of them. Remember, the mast and sails are like a giant lever with a giant hand on them, trying to capsize or pitchpole your boat. You don't get that effect from the M&M style reverse bows. (The downward thrust effect on bulbs, I mean. The giant lever effect is intrinsic to sailboats flying sails.)
    Big Cat, I don't understand your logic.

    Those bulbs would surely reduce the chance of pitchpoling down wind because they increase the buoyancy and resist depression in the waves. The opposite of thin bows with little lift.

    Also, why would reverse style bows, as mooted on the Apha 42, be of any benefit. In calm sheltered waters those bows may be good. I would not like to try them out in real seas in F6 or more. And certainly not when going downwind too fast.

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

  5. #25
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    Default Re: Wavepiercing Bows on Catamarans

    I have a question about the bow design. What will happen if you hit a big piece of floating wood or worse still: a container. With the bow angled the 'normal' way the cat will try to climb over it and (if small enough) will simply leave it behind with more or less harmful bumps. It will try to mount a sunken container but come to a more or less gradual stop. Now, with the bow in the opposite angle will the object try to climb the cat? Will it come to a dead stop when hitting a container? I'm hoping the bows are sacrificial? Any thoughts or real life experience on this?

    Eric
    Sailors do it with the wind ....

  6. #26
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by sigmasailor View Post
    I have a question about the bow design. What will happen if you hit a big piece of floating wood or worse still: a container. With the bow angled the 'normal' way the cat will try to climb over it and (if small enough) will simply leave it behind with more or less harmful bumps. It will try to mount a sunken container but come to a more or less gradual stop. Now, with the bow in the opposite angle will the object try to climb the cat? Will it come to a dead stop when hitting a container? I'm hoping the bows are sacrificial? Any thoughts or real life experience on this?

    Eric
    Gooday 'sigma' - with great respect - your "will try to climb over it" & "try to mount a sunker container" is just not true. Suggest you make a substantial contribution to this thread - & - contact your insurance council & get some hard-core factual data - as to the real facts - about 'container-collision' so the facts can/will assist all of us to prevent - one of us dieing. I am trying to get the 'insurance council' in the southern hemi. to do the same.

    All 'extended bows' are sacrificial - as you should already know.

    Thanks for keeping this topic - up-front - I really appreciate it. Ciao, james.

  7. #27
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by James Val Jackson View Post
    Gooday 'sigma' - with great respect - your "will try to climb over it" & "try to mount a sunker container" is just not true.
    Don't think Tony Bullimore would agree with u James after his crash into a wharf

    Mike

  8. #28
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    Lake Macquarie, NSW
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    Default Re: Wavepiercing Bows on Catamarans

    To go back to the original question, Lock Crowther put the bulbs into his designs to eliminate the hobby horsing in short seas. When a boat has a swept forefoot this can match the shape of the oncoming wave and you experience a 'sea crash' , you also temporarily loose bouyancy when the bow has no water under it prior to the crash. By having a submerged source of bouyancy you can lessen the effect of the oncoming wave and the bulb resists the tendency to move up and down in the water like a shock absorber. Wahoo is currently having a small cabin fitted to provide some shade on the longer voyages planned by the current owner, would you like some pics of the bow shape ?

  9. #29
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by 3timesbetter View Post
    . . . Wahoo is currently having a small cabin fitted to provide some shade on the longer voyages planned by the current owner, would you like some pics of the bow shape ?
    Yes please!

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

  10. #30
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    near Seattle
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by dmmbruce View Post
    Big Cat, I don't understand your logic.

    Those bulbs would surely reduce the chance of pitchpoling down wind because they increase the buoyancy and resist depression in the waves. The opposite of thin bows with little lift.

    Also, why would reverse style bows, as mooted on the Apha 42, be of any benefit. In calm sheltered waters those bows may be good. I would not like to try them out in real seas in F6 or more. And certainly not when going downwind too fast.

    Mike
    Hi, Mike - Extending the bows with bulbs will indeed resist depressing them, but when you do depress the bows, the water is now pushing down on the top of the bulb. This is what happens when you depress a lee bow to the point where the deck is under water. Once that happens, the sea is pushing the bow downward instead of upward, because of the boat's momentum. In effect, the bulb is a lever - it pushes upwards to begin with, and as the boat starts to pitchpole, it pushes downwards.
    Currently concentrating on http://earthnurture.com .

  11. #31
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by BigCat View Post
    Hi, Mike - Extending the bows with bulbs will indeed resist depressing them, but when you do depress the bows, the water is now pushing down on the top of the bulb. This is what happens when you depress a lee bow to the point where the deck is under water. Once that happens, the sea is pushing the bow downward instead of upward, because of the boat's momentum. In effect, the bulb is a lever - it pushes upwards to begin with, and as the boat starts to pitchpole, it pushes downwards.
    Gooday 'B-C' Trust the weather & sailing is great - where you're at ! !

    As the top surface of bulbs are usually very hydro & aero dynamically shaped - what % of down force in foot/lbs - compared to the lift generated by the extra foot/lbs of floatation generated by the extra submerged bow - do you think the bulb exerts in real terms other than pure theory ??? I suspect that there is a real figure here but don't believe it's is a significant amount. I'd sure be interested in your & others opinions on this matter. Thanks - ciao, james

  12. #32
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    Default Wavepiercing Bows on Alpha 42

    Got to see the first hull produced for the Alpha 42 last night.

    FYI.

    Marshall
    Attached Images Attached Images
    "People sail for fun and no one has yet convinced me that it's more fun to go slow than it is to go fast." -- Dick Newick

  13. #33

    Default Re: Wavepiercing Bows on Alpha 42

    Quote Originally Posted by searenitysail View Post
    Got to see the first hull produced for the Alpha 42 last night.

    FYI.

    Marshall
    Cough cough...


    Attached Images Attached Images

  14. #34
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    Default Re: Wavepiercing Bows on Alpha 42

    Quote Originally Posted by Sully View Post
    Cough cough...
    Yeah, You could still smell the fumes!

    Marshall
    "People sail for fun and no one has yet convinced me that it's more fun to go slow than it is to go fast." -- Dick Newick

  15. #35

    Default Re: Wavepiercing Bows on Alpha 42

    Quote Originally Posted by searenitysail View Post
    Yeah, You could still smell the fumes!

    Marshall
    Ha ha ha!! That is the best laugh I've had in weeks!

  16. #36

    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by multihullsailor6 View Post
    Since seeing Francis Joyon's trimaran "IDEC" bowling along at high speeds I have become interested in wave-piercing 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?
    www.whichcat_multi.com here who can hopefully bring this topic to the fore.

    I sailed a Tornado Olympic Cat that must have had wave piercing hulls because I used to pierce the waves a lot and pitch-pole doing it in the middle of a race.

    You can watch the America Cup Cats doing wave piercing now, same as the Tornado.

    I was going to buy a Conser 47' until I looked closely at the 3' 6" high bows that are wave piercing and came to the conclusion that driven hard to windward, reaching or downwind, the Bows would dig in just like the Tornado or America's cup Cats and pitch-pole.

    I am convinced that 3' 6" of Bow is NOT ENOUGH to stop the bows digging in, even though the hulls are narrow and the transom is very narrow, just like the Tornado, so it will nose dive at speed.

    The New Zealand Young design Cats have Wave Piercing Bows but, that is another story, forward raked bows move the buoyancy forward and low but with high freeboard, a far cry from the Conser 47' which talks of 30 knots boat speed, downwards if you are not careful.

    Lets get this Wave Piercing hulls thing talked about once and for all. It's no good one designer doing his thing (John Conser) and we go nose diving.

    Let us Cat sailors get this subject sorted.

    The pictures you show are very Prout in design. I have a feeling that is not the way to go but the forward rake bows look like that will work.

    If this topic does not talk the hind leg off a donkey, nothing will.

    I am proposing Forward raked Bows, narrow hulls and Transoms with steps that can be Pooped, dumping a ton of water on the back end as the way to go. (That will keep the bows up) So will Lock Crowther design bows with forward raked bows, where is that Son of Lock Crowther???

    Regards

    www.WhichCat-Multi.com

  17. #37
    Join Date
    Oct 2008
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    I'm from Bermuda, CareFree currently in Grenada
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    Default Re: Wavepiercing Bows on Catamarans

    Ted Clements' thoughts on wave-piercing bows from his website here:
    http://catamaranconcepts.com/2012/09...piercing-bows/

  18. #38
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    Default Loch Crowther's Wahoo...bows

    Quote Originally Posted by 3timesbetter View Post
    To go back to the original question, Lock Crowther put the bulbs into his designs to eliminate the hobby horsing in short seas. When a boat has a swept forefoot this can match the shape of the oncoming wave and you experience a 'sea crash' , you also temporarily loose bouyancy when the bow has no water under it prior to the crash. By having a submerged source of bouyancy you can lessen the effect of the oncoming wave and the bulb resists the tendency to move up and down in the water like a shock absorber. Wahoo is currently having a small cabin fitted to provide some shade on the longer voyages planned by the current owner, would you like some pics of the bow shape ?
    Lets see, these pics never did happen. Here are a few
    Crowther_Wahoo_.jpg

    Profile 60.gif

    Little better view of the Wahoo
    http://www.boatdesign.net/gallery/sh...406/ppuser/399

    Lock Crowther's 'tulip bow'
    http://www.sailmagazine.com/images/a...ailjermain.pdf
    Last edited by brian eiland; 20th March 2013 at 04:20 PM.

  19. #39
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    WashDC, Annapolis, Thailand
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    Default Re: Wavepiercing Bows on Catamarans

    BULB (BULBOUS) BOWS on Multihulls,.... Why?

    http://www.boatdesign.net/forums/boa...tml#post482009

  20. #40

    Default Re: Wavepiercing Bows on Catamarans

    I think some of these are effective, or I imagine they are, simply because they increase the waterline length. The hydrodynamics of bulbous and wedge bows at speed is a bit complex. Some have added a bulb to prevent hobby horsing, or to reduce it. There are limitations to any design using flat sheets which preclude compound curves. Everything is a compromise to some extent. It would be great to slice through waves with no loss of momentum and yet have plenty of weight carrying capacity--but water is heavy stuff and takes some time to get out of the way at higher speeds. The usual way of avoiding this is to go over it--hence planing hulls, but for sail boats we simply have to get our wetted surfaces to slip through the water as easily as does a shark or a whale.

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