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Thread: Wavepiercing Bows on Catamarans

  1. #61
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    Default Re: Wavepiercing Bows on Catamarans

    Am I mistaken that Lock Crowther eventually gave away the concept of bulb bow as his experience with them built up?

    Certainly wave piercing are in vouge now.

  2. #62
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by searenitysail View Post
    Somehow I think this concept in hull design has gone beyond a fashion statement!

    When its used on a 9.2T condomaran cruising boat fitted mostly with LAR keels its a fashion statement, same as curved boards.
    Last edited by dennisail; 19th December 2013 at 01:17 AM.

  3. #63
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    Default Re: Wavepiercing Bows on Catamarans

    dennisail,

    Thank you for the clarification.

    It appears that the speeds attained in the sailing trials for the Alpha 42 might be a little better than for a condomaran, as that is what you are apparently referring to the Alpha 42 as.

    I am not sure Gregor had a speed demon in mind when he developed the concept and design of the Alpha 42. According to the web site, ...The Alpha 42 is a true dual purpose yacht: She can be an entry level boat for the first time owner as she is easy to single hand and maintain yet on the other hand represents a capable and tough ocean going cruising multihull that can take a live aboard family safely around the world. Charter operators will appreciate the Alpha 42′s spacious deck and entertainment spaces as well as her large proportioned interior and flexible layout options which can sleep up to 10...

    You appear to be making a lot of suppositions in your claims and opinions here, and on the 13-page thread you started elsewhere, without stating your background. I have readily admitted my lack of expertise or knowledge of the subject and have not made any claims or taken any position, nor made any disparaging remarks or innuendoes; I have only contributed comments or information to this thread.

    I guess we will have to wait and see what actual tests have to say about the performance of any cruising catamaran with reverse bows. It seems that in this day and age of computer simulations, there may be some justification other than as a marketing ploy.

    Good luck with your own build; you are evidently doing some research. Please let us know what design you finally choose to build and why, and keep us up-to-date with pictures; a lot of members have the same dream as you, and your efforts can only help them in realizing their own dreams.

    BTW, I think it is probably time to yell THREAD DRIFT since it appears Brian wants to discuss bulb bows.

    So, I am out of this thread since I won't own a sailboat with a bulb bow (or even be able to afford one with a reverse bow). This was a nice diversion, though, after hauling Searenity on Monday.

    Bye,

    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

  4. #64
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    Default Re: Wavepiercing Bows on Catamarans

    I have no qualifications in naval architecture, but I am entitled to my opinion as much as anyone else that posts on the net. However plenty of people with qualifications did post in my thread.

    My opinion is that reverse bows on a heavy charter cat are quite a bit different than when used on a foiling americas cup racing boat. You appear to believe there is no difference, and you are entitled to have that opinion as much I am to the contrary.

    Chees.

  5. #65
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by downunder View Post
    Am I mistaken that Lock Crowther eventually gave away the concept of bulb bow as his experience with them built up?

    Certainly wave piercing are in vogue now.
    Lock Crowther used bulb bows as a quick fix to make his early designs more buoyant forwards, as they were very prone to pitching - which is one reason there were very few seen in the UK

    His later designs had a more refined hull and so didn't need to have bulb bows, the buoyancy was "built in'

    Richard Woods

  6. #66
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    Default Re: Wavepiercing Bows on Catamarans

    These two photos are of a 20 year old 26ft Shuttleworth cat which originally had vertical bows. No problems for 19 years. Last winter the owner changed to ram bows with the predictable result, each bow was damaged in two separate incidents.

    Fortunately the "real" bows are still there, so no leaks.

    And the fact that it is a small light boat meant the damage was much reduced when compared to a bigger heavier boat

    Richard Woods
    Attached Images Attached Images

  7. #67
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by Woods Designs View Post
    Lock Crowther used bulb bows as a quick fix to make his early designs more buoyant forwards, as they were very prone to pitching - which is one reason there were very few seen in the UK

    His later designs had a more refined hull and so didn't need to have bulb bows, the buoyancy was "built in'

    Richard Woods
    Thanks Richard.

    Thought there was a reason no designers have been using them in more recent years.

  8. #68
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    Default Re: Wavepiercing Bows on Catamarans

    The Boat from Norway, is a MYD 35, and it was rebuild with "Bulbs" and HYD propulsion back some time, and the owner is saying that it did reduce "Pitching" a lot "Glenn Halnes" was the owner. he also did cut down the mast with 1.1meter, and gave the main a Flathead sail.

  9. #69

    Default Re: Wavepiercing Bows on Catamarans

    The story of the abandoning of the new Alpha 42 “Be Good Too” [see http://www.wavetrain.net/news-a-views/558-helicopter-evacuation-abandoning-be-good-too ] begs the question of the suitability of wave-piercing bows that are becoming more and more prevalent on catamarans. The new boats are elegant looking and reportedly are performing very well…remember the America’s Cup racers? But “Be Good Too” succumbed to the slamming of a large wave directly on the bow, hitting it hard enough to stop the boat and drive it backwards enough to damage the rudders and their control apparatus, terminally disabling the boat. The on-board testimony addresses the impact on the salon windows. One can imagine it impacted the forward part of the bridge-deck heavily as well.
    The question is would conventional bows with overhang and thus reserve buoyancy have lifted the boat to where the wave would not have had as great an impact? Designers need to address this with analysis and/or test results.

  10. #70
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by Woods Designs View Post
    These two photos are of a 20 year old 26ft Shuttleworth cat which originally had vertical bows. No problems for 19 years. Last winter the owner changed to ram bows with the predictable result, each bow was damaged in two separate incidents.

    Fortunately the "real" bows are still there, so no leaks.

    And the fact that it is a small light boat meant the damage was much reduced when compared to a bigger heavier boat

    Richard Woods
    Interesting case study and pics Richard.

    Brian

  11. #71

    Default Re: Wavepiercing Bows on Catamarans

    Yes, you could be right wave piercing (or axe) bows only give a performance benefit within a very small speed, wave window. I also wonder about the differences between their application mono vs multi in this respect. A mono only experiences the effect of one wave but a multi has to cope with two waves acting independently on each bow, in small waves is no big deal, but in bigger waves this must have an destabilising effect on the steering with one bow then the other tending to wave pierce. Wonder how this would influence control when surfing in big waves?

    But more to the point what happens when moving slowly in big waves? Axe bows could have very undesirable effects. For example in the trough of a wave train the axe bows (or bow) would, "wave pierce", forcing the boat downwards and concentrating the wave impact and forces on to the wing and superstructure. Compare this to a more conventional overhanging bow or even a vertical stem with flare, that would do the opposite directing the wave forces downwards and the boat will rise up over the wave, (assuming the deck is shaped to shed water) and the boat will stay on top of the wave.

    Was this maybe what was happening on the Alpha and why the boat was stopped so abruptly and the saloon windows were leaking?

  12. #72
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    Default Re: Wavepiercing Bows on Catamarans

    The reports on the Alpha 42 was that it was a large breaking wave that hit them. The bow shapes, in that case, had nothing at all to do with it - a breaking wave would have broken over any bow shape the same.

    The saloon windows were leaking because they were poorly engineered and installed. Neither the bow shapes, nor the breaking wave, had anything to do with that.

    The rudders bent because…well we don't actually know - but it again seems like a combination of poor engineering and installation. The bow shapes had nothing to do with that either.

    Personally, I think the Alpha 42 bow shapes are marketing gimmicks and esthetics. "Wave piercing" in this instance is simply marketing speak. They are not radical at all, or functionally much different to normal bows. I think the problem here is that people are looking at the Alpha bows and thinking about similar bows on racing boats. They have little in common, other than a passing resemblance.

    Mark
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  13. #73

    Default Re: Wavepiercing Bows on Catamarans

    I disagree with Colemj when he says" They are not radical at all, or functionally much different to normal bows". Hey dude have you ever sat on your tramp and watched the water on your bows and notice how much friction is being put upon your Manta with its thick bow entry. That plus the whisker wires from the bow sprit probably slows you down quite a bit and I'm not an engineer but I'd guess at lease a third of a knot. Alpha has the correct idea with the bows and I really like the feature with the sprit connected to the main beam, no whisker wires.

  14. #74

    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by victor View Post
    I disagree with Colemj when he says" They are not radical at all, or functionally much different to normal bows". Hey dude have you ever sat on your tramp and watched the water on your bows and notice how much friction is being put upon your Manta with its thick bow entry. That plus the whisker wires from the bow sprit probably slows you down quite a bit and I'm not an engineer but I'd guess at lease a third of a knot. Alpha has the correct idea with the bows and I really like the feature with the sprit connected to the main beam, no whisker wires.
    So you would agree with what Calculator and I am suggesting and that maybe the bow shape contributed to the Alpha's problems.

  15. #75
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    Default Re: Wavepiercing Bows on Catamarans

    Even if most people think it is one reason or another. It does not mean they are correct, given the limited knowledge of this boat and how it's design actually functions.

  16. #76

    Thumbs up Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by Peter View Post
    So you would agree with what Calculator and I am suggesting and that maybe the bow shape contributed to the Alpha's problems.
    Not that sure that aerodynamic bows would cause the vessel to go backwards in a wave trough. I do know that in certain wave conditions coming off a wave can drive the boat back and if the rudder position was hard over caused by in attention by the helms person or autopilot error you can hurt the rudder.

  17. #77
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by victor View Post
    I disagree with Colemj when he says" They are not radical at all, or functionally much different to normal bows". Hey dude have you ever sat on your tramp and watched the water on your bows and notice how much friction is being put upon your Manta with its thick bow entry. That plus the whisker wires from the bow sprit probably slows you down quite a bit and I'm not an engineer but I'd guess at lease a third of a knot. Alpha has the correct idea with the bows and I really like the feature with the sprit connected to the main beam, no whisker wires.
    They are neither radical nor functionally much different than other bows.

    Their general shape harkens toward wave-piercing bows of racing boats, but their construction is little different from other catamarans. Go look at some pictures of true "wave piercing" bows on race boats and tell me what you think.

    Look at the attached picture. That entry is the same thickness/fineness as our Manta, as well as many other catamarans. The volume higher up is actually greater than our boat (which is good - I wish we had more volume there).

    It is obvious you have never seen a Manta, because I don't know of any with whisker wires or sprits.

    My point, that you are in disagreement with, is that the bow shape of the Alpha 42 did not contribute to any of the problems that they experienced.

    Are you now saying that the bows on the Alpha 42 actually did cause all of their troubles?

    Mark
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    Last edited by colemj; 25th January 2014 at 02:26 PM.
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  18. #78
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    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by colemj View Post
    They are neither radical nor functionally much different than other bows.

    Their general shape harkens toward wave-piercing bows of racing boats, but their construction is little different from other catamarans. Go look at some pictures of true "wave piercing" bows on race boats and tell me what you think.

    Look at the attached picture. That entry is the same thickness/fineness as our Manta, as well as many other catamarans. The volume higher up is actually greater than our boat (which is good - I wish we had more volume there).

    It is obvious you have never seen a Manta, because I don't know of any with whisker wires or sprits.

    My point, that you are in disagreement with, is that the bow shape of the Alpha 42 did not contribute to any of the problems that they experienced.

    Are you now saying that the bows on the Alpha 42 actually did cause all of their troubles?

    Mark
    Watching the vessel sitting in the water during the helo rescue I suspect the bows had nothing to do with their problems.

    Agreed that the water leaks and rudder problems were engineering/construction issues.

  19. #79
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    Default Re: Wavepiercing Bows on Catamarans

    Winter day, killing time, Searenity on the hard, so browsing multihulls.

    And what do I find?

    I have been in and out of this thread, so I don't know if this picture was posted or not.



    http://www.catamarans.com/sales_port...g-search-boats

    1984 Melrose Marine. Sorry, never heard of them.

    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

  20. #80

    Default Re: Wavepiercing Bows on Catamarans

    Quote Originally Posted by searenitysail View Post
    Winter day, killing time, Searenity on the hard, so browsing multihulls.

    And what do I find?

    I have been in and out of this thread, so I don't know if this picture was posted or not.



    http://www.catamarans.com/sales_port...g-search-boats

    1984 Melrose Marine. Sorry, never heard of them.

    Marshall
    Nice looking boat. We saw her a couple of years ago on the Cheseapake. Don't think those would be considered wave piercing hulls, more likely bulbs on the bows to stop pitching. Something Crowther was well known for.

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