High-Speed Pentamaran Yacht

Discussion in 'Boat Design' started by High Life, Jan 23, 2013.

  1. High Life
    Joined: Dec 2012
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    High Life Junior Member

    An simple and innovative concept from BMT Nigel Gee:
    media.bmt.org/bmt_media/bmt_images/62/BMTNigelGeeVeloce2.jpg

    BMT in Yachts | Concept design, naval architecture and inspection http://www.bmtyachts.com/?/411/746/1760
     
  2. groper
    Joined: Jun 2011
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    groper Senior Member

    Hehe... if they think they can load this sucker up with all the mod cons in triple decker fashion and still maintain a good Displacement length ratio, my name is santa claus...

    No amount of "hydrodynamic optimization" in the area of reducing wetted surface area is applicable here, what the "air sponson" is not carrying, the other hulls must carry by sitting deeper in the water...

    There is no magic in efficient designs, they must be light, long, and slender... the rest is just hot air...

    Yikes! i just read this from the site ;

    Project Véloce is based on a 130m platform capable of over 40 knots. The beam of 30m offers significantly more internal area than on an equivalently sized monohull leading to exceptional internal spaces with true flexibility in configuration of the layout.

    The propulsion system features a CODOG (Combined Diesel Or Gas) plant producing approximately 44MW of installed propulsive power, delivered via waterjets offering outstanding maneuverability and acceleration. For low and medium speed operation twin 20V8000 diesels are utilised providing efficient long range operation whilst for sprint speeds a single LM2500+ pushes the speed beyond 40 knots.


    I dont think they care too much for efficiency... absolute opulence like this is criminal...
     
  3. Lister

    Lister Previous Member

    Well said Groper. A bunch of lie with just a rendering and arrogant text to attract suckers.
    They are numerous "genius patented" like that. It is sad. It confuse high end customer who needs more than everyone real guidance.
     
  4. tomas
    Joined: Nov 2012
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    tomas Senior Member

    44 MegaWatts ?? !!


    That is greater than the power-plants used in the 6,000+ passenger cruise ship "Oasis of the Seas", consisting of 3 x Wärtsilä engines of 13.86 MW each.

    Yes, criminal seems an apt term.
     
  5. Manie B
    Joined: Sep 2006
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    Manie B Senior Member

    Well when I read their website I also could not believe my eyes.
    Bad news for such a big company to slip up so badly
     
  6. El_Guero

    El_Guero Previous Member

    It is just a big fancy trimaran ....

    The forward amas are in front of the rear amas .... BAD design. There should be one flowing ama. As it is, there is a separation between the two floats .... and that would mean a LOT of drag when the front ama gets submerged.

    IMHO.

    wayne
     
  7. Number4

    Number4 Previous Member

    I am afraid that in my ignorance I am not beeing so outraged.
    The power seems to be comparable to another ship of similar dimensions and performance.
    The forward amas contact the water when the vessel is turning or there is a heavy sea, which would imply a reduction in speed, and therefore the drag penalty is not so great.
    I am imagining that the second set of amas will only come into contact with the water less than 1% of the time. So surely a reduction of drag for more than 99% of the time is a success?
    They also state that most of the time it will use less than 16MW of power.
    Maybe they do have a clue after all???


    http://www.bmtyachts.com/?/411/746/1760

    Project Véloce is based on a 130m platform capable of over 40 knots. The beam of 30m offers significantly more internal area than on an equivalently sized monohull leading to exceptional internal spaces with true flexibility in configuration of the layout.

    The propulsion system features a CODOG (Combined Diesel Or Gas) plant producing approximately 44MW of installed propulsive power, delivered via waterjets offering outstanding maneuverability and acceleration. For low and medium speed operation twin 20V8000 diesels are utilised providing efficient long range operation whilst for sprint speeds a single LM2500+ pushes the speed beyond 40 knots.


    http://www.ship-technology.com/projects/benchijigua/

    Austal's largest Trimaran, the Benchijigua Express, was delivered to the European ferry company Fred Olsen in May 2005. It serves the islands of La Gomera and La Palma and the port of Los Cristianos in the south of Tenerife.

    The vessel is 126.7m in length overall and 114.8m at water level. It has a beam of 30.4m, a hull depth of 8.2m and a 4m draught. The trimaran registers a deadweight of 1,000t.

    The designers were given the challenge of building a vessel that could carry 500t deadweight and achieve a speed of 40.4 knots (32.8MW). This would require four 8.2MW engines working at 90%. These four engines are positioned in two separate engine rooms in the trimaran’s central hull. The designers selected MTU 20V8000 engines which generate 8,200kW at 1,150rpm, although the operator has the option to upgrade these to a 9,200kW output; this will involve the incorporation of turbochargers and a new fuel pump.
     

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  8. groper
    Joined: Jun 2011
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    groper Senior Member

    The point is, theres no free lunch with buoyancy... by keeping the second pair of sponsons clear of the water, the immersed ones must be "more immersed"... All they have done is reduced the aspect ratio of the immersed sponsons.

    So, each immersed sponson is shorter and would need more draft or beam for the same buoyancy ... Unfortunately, by decreasing the immersed sponson length to beam ratio, it will make it less efficient than if it had only 1 pair of longer sponsons...
     
  9. El_Guero

    El_Guero Previous Member

    DANG!

    Why couldn't I have written it like Groper did ....

    :idea: Can I quote you?
     
  10. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    The one caviat Grouper is if the boat has to be designed to a class rule that requires X amount of reserve stability, which is far beyond the amount that the boat would normally need. In this case the extra sponsons could be providing the displacement required to meet the rule as opposed to meeting normal operational requirements.

    For instance is there was a class rule that requires a vehicle to remain upright at rest. It's a fine rule if you are designing a car with four wheels, but if I want to design a bike, I may choose to add training wheels as a rule beater. They have nothing to do with normal operation, they just allow the vehicle to meat the classification specs in an unorthodox way.

    If this is the case, this is just another in a long line of rule beaters. Where bizarre design choices are made to meet the rule.
     
    Last edited: Jan 25, 2013
  11. Number4

    Number4 Previous Member

    From
    http://www.bmtyachts.com/?/411/746/1760
    Conventional stabilised monohulls typically require relatively deeply immersed and long sponsons to meet damaged stability requirements and these can incur significant resistance penalties. The Pentamaran overcomes this by having two pairs of sponsons; a very short and shallow pair aft and a forward pair clear of the static water surface. These forward sponsons only become immersed as the vessel heels, consequently stability characteristics are maintained with no resistance penalty. The Pentamaran offers a wide bodied and stable platform with outstanding seakeeping characteristics whilst retaining minimum speed loss in higher sea states.
    BMT has undertaken some US$5 million worth of testing on numerous Pentamaran designs and the technology is now fully mature. Further development of the Project Véloce design is currently underway. "

    As far as I am concerned, this makes perfect sense.

    If you are going to call out a highly reputed naval architect and ship building company to the world, and accuse them of lying and false advertising, please back this up with some facts and figures, otherwise you are guilty of slander.

    So far I am not buying your claims.
    Please post a link to a ship you have designed to make me change my mind.
     
  12. Number4

    Number4 Previous Member

    The analogy of a child's bicycle with stabilisers is very good. They have invented a set of two stage stabilisers, that weigh the same as a single pair, but for more than 99% of the time have less drag.
     
  13. groper
    Joined: Jun 2011
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    groper Senior Member

    Stumble, you maybe correct in that its a "rule beater"... However, if that were the case, im sure there are other ways around the problem. Its also at odds with the other circa 130m passenger ferry tri posted eariler in the thread, theyve done it without the extra 2 "airborne sponsons"...

    Have a think about it... if these sopnsons are not immersed, they are not carrying any of the boats weight. The weight is still there tho, isnt it... So the entire ship mass, is carried by the main hull and the other 2 immersed sponsons. Their wetted area has increased in order to carry the weight, in comparison to if the "airborne sponsons" were immersed. So theres no free lunch here in terms of drag...
     
  14. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    This is a case which can be studied with Leo Lazauskas' Michlet software, being a combination of very slender hull forms. In that way we could be able to get out of the realm of guesswork and enter the world of actual numbers. A trimaran with long shallow amas vs. one with short but deeper amas.
    I can give it a try tomorrow, but if someone else wants to do the homework in the meanwhile, I won't complain. ;)
    Cheers
     

  15. Number4

    Number4 Previous Member

    Hi daiquiri,
    I look forward to your results. However, the blurb states "The Pentamaran overcomes this by having two pairs of sponsons; a very short and shallow pair aft and a forward pair clear of the static water surface."
    Can you run the program with more wetted area in the main hull, and less in the amas?

    Hi groper,
    I take your points. I am completely out of my depth on this. But my uneducated brain thinks they may be on to something. They are claiming to have reduced the wetted area of the amas. This implies it has been transferred to the main hull, which surely is a step in the right direction?

    Damage stability requirements
    http://www.mek.dtu.dk/Tema artikler/New_damage_stability_requirements_for_ships.aspx
    http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA306057
    "Damage stability and reserve of buoyancy are both very important indicators of
    the ship's survivability, but generally, damage stability could be more important because a ship without sufficient stability after damage will capsize, even though it may have enough reserve buoyancy to remain afloat."

    Best Wishes,
    Adam
     
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