Constanzi Stern of the Queen Mary 2

Discussion in 'Boat Design' started by Raffaele Frontera, Jul 22, 2018.

  1. Raffaele Frontera
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    Raffaele Frontera Naval Architect

    Dear all,

    I would like to know the reason of the Constanzi stern of the Queen Mary 2, which have been in your opinion the reason of the designer to create a mixed stern.

    Thank you in advance,

    Raffaele

    queen mary2 https://ibb.co/e0yuzJ
     

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  2. TANSL
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    TANSL Senior Member

    It was necessary to add aft buoyancy. It is the solution to a design error.
     
  3. bhnautika
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    bhnautika Senior Member

    Tansl an error, really! More like a compromise, having a classic rounded stern but enabling modern propulsion systems, azimuth thrusters maybe, longer waterline etc, I think this type of stern has been proposed for other ships.
     
  4. JamesG123
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    JamesG123 Senior Member

    They really built her like that? It looks like a CAD model made by someone who didn't know how to merge meshes.
     
  5. Rurudyne
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    Rurudyne Senior Member

    It looks like the lady is sitting on a barstool in a bustle.
     
  6. TANSL
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    TANSL Senior Member

    @bhnautika, do you think "that" improves the stern hydrodynamics ?. Who can think of designing a boat with a grain in the back ?. Change in the original propulsive system ?, No new system could compensate for the losses caused by that bulge, not to mention the improvements, undoubted (???), which provide the ship to maneuver.
    Maybe I have not understood your reasoning well.
    That type of stern has been proposed for several vessels (that's true), after launching, when they have had a problem in estimating the weight or its center of gravity. In the boats you have to take a very, very rigorous control of the weights and that has not always been taken into account.
     
  7. alan craig
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    alan craig Senior Member

    Just Wikipedia it:

    Payne's initial intent was to make the ship's stern profile with a spoon shape, similar to that on most previous ocean liners, but the mounting of the propeller pods required a flat transom. The compromise was a Constanzi stern — a combination of the two. The final design was agreed upon, as a Constanzi stern provides the transom required for azimuthal pod propulsors, and provides better seaholding characteristics in a following swell than a standard transom stern.[25] In common with many modern ships, both passenger and cargo, Queen Mary 2 has a bulbous bow to reduce drag and thereby increase speed, range, and fuel efficiency.
     
  8. bhnautika
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    bhnautika Senior Member

    Tansl have a good look at the picture again. The curved stern is at best a cosmetic touch to a flat transom,it is above the waterline so “stern hydrodynamic” may not be relevant in all situations . I am at a loss to see any “bulge”, the waterline runs smoothly to the transom. This ship was designed this way and I don’t think there was a oops we forgot this and that in the weight schedule.
     
  9. TANSL
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    TANSL Senior Member

    (OK there is no bulge, I used the word inadequate). Well, if the ship was designed like that, I should shut up and apologize for speaking more than I should.
    Do you really think that form 1, of the figure, has better hydrodynamics than form 2? I do not think so. I also do not understand why it was decided to project a rounded stern, which is very expensive and loses a lot of space, being able to make a normal transom stern, and especially taking into account that the possible disadvantages or advantages of the submerged part of the transom were already unavoidable.
     

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  10. Raffaele Frontera
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    Raffaele Frontera Naval Architect

    Thanks everyone for the technical comments,

    much appreciated.

    I found really interesting the last comment of TANSL, because it is exactly the point of my questions:

    1) The transom it was choose for the AZIPOD? Ok.. why then they need a transom stern?
    Even if they are better for AZIPOD, why hydro-dynamically talking it should be preferred a transom instead of a rounded stern?

    2) If there is a good reason then why rounded stern above WaterLine?

    3) Which is the goal of the designer here?

    4) Looking into the streamline that I tried to draw in the picture attached, in my opinion there is no a good hydrodynamic principle, I mean or you are Leonardo Da Vinci to understand the turbulence so well organizing 4 AZIPOD in such "open"water or just you are trying to couch more water that you can with 4 AZIPOD below a transom stern, without taking care so much of the tangential speed, so vortex, so vibration..

    To all of you my points, so curious about your opinion.

    I am glad that I raised a good subject which bring into this forum not only concept design of boat but also of vessels.

    Thanks a lot

    Raffaele
     

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  11. Rurudyne
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    Rurudyne Senior Member

    It may have little to do with hydrodynamics. It may just be a matter of having room for the mechanicals in the given space allotted (as well as servicing them).

    A longer cruiser stern with the azipods where they are would have probably looked great compared to what she has got. Even if just a little longer.
     
  12. gonzo
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    gonzo Senior Member

    It keeps the look of the stern similar to the Queen Mary.
     
  13. Raffaele Frontera
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    Raffaele Frontera Naval Architect

    Hi @gonzo but do you think that make sense her stern?
     
  14. Rurudyne
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    Rurudyne Senior Member

    Yeah. Kinda like the non-functional paddlewheels on some of these casino things plying the Mississippi.

    It's not something passengers will notice while onboard.
     

  15. gonzo
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    gonzo Senior Member

    I think it makes sense from the marketing angle.
     
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