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Wavepiercers, Trimarans, SWATH and such...

Discussion in 'General Catamaran Discussion' started by YachtForums, Jun 27, 2004.

  1. YachtForum

    YachtForum YachtForums Publisher

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    Interesting. My first thoughts are... the boat will need to be kept extremely light to achieve these figures, which will sacrifice ride quality. However, a wave-piercing, narrow hull form would help compensate for this.

    While the cruise speed sounds reasonable, the top speed sounds a little optimistic. The first hurdle is getting a 74' boat to plane with 1250 hp connected to a single waterjet. Marginal, but not impossible, IF... the boat was simply a shell, with engines, tanks and running gear, coupled with a shallow deadrise hull... the figures are sustainable. As a fitted-out yacht, with all the trimmings... I think weight will be a critical factor.

    It's seems piercing mono hulls are the latest industry darling, but we have to keep in mind... they're not for everyone. Just people with an endless supply of windshield wiper blades. ;)

    Still... I love the design. Thank you for bringing this to YF Innomare!
  2. Yacht News

    Yacht News YF News Editor

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    That is a very daring design...but what i find is that they are alot of designs however, not alot of piercer yachts in actuality...SPIRIT...?(she is a Cat piercer)....anything else..on the mega yachtmarket like her...or mono hull piercers?
  3. YachtForum

    YachtForum YachtForums Publisher

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  4. Yacht News

    Yacht News YF News Editor

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    Yes Carl, i didnt remember the Sigma project.....Question thoough? so all true wave piercers have to have the piercing points low to the waves?....and since Sigma's bow is so high.....this is what you mean that she wouldnt really be considered?...I'm not so sure if you get what i mean?
  5. OutMyWindow

    OutMyWindow Senior Member

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    Wow, that Earthrace 151m design is truly something!!. I hope someone builds it.
    If it pulled into Monaco Harbour, the other homogenized mega yachts would sink themselves out of fear.:eek:
  6. YachtForum

    YachtForum YachtForums Publisher

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    If you take a close look at Sigma, you’ll see the hull is actually rather conventional, with a standard rise and flair leading up to the bow. The only difference is the bow is swept back from the waterline, giving SIGMA’s bow some piercing attributes, i.e. offering less lift and resistance against oncoming waves.

    As the name implies, wave-piercing hulls are designed to go “thru” waves, not over them. Typically, these hulls are optimized for sub-surface operation with an emphasis placed on reducing acceleration & motions of waves at the water line and above. By sweeping the bow backwards from the waterline, an oncoming wave encounters less resistance in contrast to a conventional forward-flaired bow. Essentially, an oncoming wave washes over the top of the deck and dissipates, as opposed to being displaced outward by a conventional bow. This results in lift on the bow, including acceleration and deceleration forces that add resistance against momentum.

    Another key element in these designs is reducing the cross section of the hull that will be subject to wave penetration at or above the waterline. To better facilitate this, a significant portion of the hull is concentrated beneath the waterline, and the cross section of the exposed hull near the waterline is limited. Essentially, a hydrofoil works the same way, because lift is being generated on a sub-surface level… where there is no turbulence. Basically, a wave-piercer is much like a SWATH design or “Small Waterplane Area Twin Hull”, originally invented by “Crazy Canuck Creed” back in the 1940’s. A label he earned because he was ahead of his time.
  7. Billy1119

    Billy1119 Senior Member

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    Now I didn't read the whole thread (maybe it's been mentioned), but this looks like White Rabbit. I do realize this was posted before it was launched. I don't know who, but what I read was the main reason for the build was for increased stability because the owner got seasick easily. Hope it helped him out...
  8. YachtForum

    YachtForum YachtForums Publisher

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  9. Billy1119

    Billy1119 Senior Member

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    Oh yes, forgot about that thread. Is that what the search function is for?? :eek:
  10. EnigmaNZ

    EnigmaNZ Member

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  11. Billy1119

    Billy1119 Senior Member

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    Wow, looking at some of the content in that link simply gives me a headache. I think it's a little out of my league, although I can't know for sure because I have no idea what it is. ;)
  12. EnigmaNZ

    EnigmaNZ Member

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    I skipped over the equations and jusr read the results, could that be cheating, anyway, it does also show that there is more to being a naval architect than coming up with nice designs, whew.
  13. AMG

    AMG YF Moderator

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    Not a Naval Architect, but I have been reading a lot of such research and often it ends like this one, "it is up to the captain".

    What I am more interested in and also been through a lot without certain conclusions, is how to avoid producing wake? I could imagine a boat with little wake will also produce less motion that cause seasickness.

    Where I live we need passenger ferries that are pretty fast, 20-30 knots, carrying 200-300 pax and still producing small and soft waves that don´t erode the islands and disturb small pleasure boats.

    It should also go with a minimum draft and be able to go in with the bow to pick up passengers. They are landing every 5-10 minutes.

    Hovercrafts would be perfect if they were not so noisy, but maybe a wavepiercer would work...?

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    Last edited: Sep 7, 2006
  14. EnigmaNZ

    EnigmaNZ Member

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    Over here in the Marlborough Sounds in New Zealand, it has been found that high speed ferries, the 98m Incat is used currently, produce shore damage from their wake to the extent they have had their speed cut to less than 18k in places. WP are not necessarily kind on the enviroment. The scientific reasoning is here

    http://www.marlborough.govt.nz/content/docs/documents/CroadandParnellS32Analysis.pdf

    Sheese, Sweden is all little islands, didn't realise it was to that extent, I really must get out more, hehe. I would suggest swath but too much draft.

    http://www.bullshooter.com/jmart/cloudx/
    Last edited: Sep 7, 2006
  15. AMG

    AMG YF Moderator

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    Thanks for this interesting link. I have been reading Danish and Norwegian studies on fast ferries, mainly catamarans, which are causing unexpected and severe erosion on beaches.

    We have from this summer tried a small number of "low wash" zones instead of speed limits. The result is mainly that the ferries and larger yachts slow down when people are present to see them, but still create wake when nobody is around...:rolleyes:

    As I live at a narrow passage I can see the difference in wash from all kinds of boats and speeds, and I have observed what I call a "Tsunami effect". Certain boats, like a 35´Coast Guard speedboat we have, when going 30 knots or more, can produce really "strong" waves that hit hard and raise high, while other similar boats at that speed creates almost no wake. I guess it is the weight of the boat that matters, despite they seems to ride as any other speedboat.

    Also the ferries are quite different from each other, some create wake that looks innocent but crashes hard to the shore, like tsunamis...:eek:

    On SWATH, they have too much draft to be used here, but I guess they have the sweetest motion for the passengers.
  16. Innomare

    Innomare Senior Member

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    more on wakes

    I once saw a huge 250 m tanker and a small 30 m patrol boat sailing one after the other on the canal coming from the port of Rotterdam. Both where going at the same speed (around 10 knots). The remarkable thing is: the 20.000 ton tanker had almost no stern wave, while the 100 ton patrol boat was creating a much larger stern wave (0.5-1 m).

    The main reason is the immersed stern area. The tanker had no immersed stern area and the streamlines could follow the hull nicely all the way, while the patrol boat was a typical hard-chine hull sailing at the "hump speed" (just before planing, with lot's of trim). The low pressure "hole" dragging behind its stern created a large stern wave.
    I wouldn't be surprised if the patrol boat was burning more fuel per nautical mile than the 200 times bigger tanker.

    Bruno

    Naval Architect
  17. Garry Hartshorn

    Garry Hartshorn Senior Member

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    Low wash cat in service on Sydney Harbour

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  18. tartanski

    tartanski Member

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  19. catmando

    catmando Senior Member

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    What is the problem with those Frenchies??? If I click on the English flag it will not let me in the site. Only clicking the French flag will do that but the language is French which I can't read.:rolleyes:
  20. K1W1

    K1W1 Senior Member

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