stability analysis by maxsurf, rhino , and archimedes!

Discussion in 'Stability' started by pavel915, Dec 5, 2006.

  1. pavel915
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    pavel915 Senior Member

    dear all wise members of this forum;
    I am a new student in naval architecture, I am very serious about designing very nice ships; but all the help I got from my university is said to be very less;;; really!So I want to learn something from the honorable members of this forum!
    I use maxsurf academic for hulll design , and then export the GHS data by using rhino and try the analysis of stability by archimedesMB.
    But I want to know a very important thing ; that is;;;;;; while going for designing the hull in maxsuf academic and analyzing the hydrostatics and stability in archimedisMd ;;;; where should I give my attention to create a very much stable vessel? that is that will have a very good stability?
    Actually I am asking you about some ways and theory by which I can make a very much stable and nice vessel by using maxsurf , rhino and archimedisMB,

    after somedays there will be ship design project and presentation compitition in my university ; so I am in need of that knoledge!
    please help me by your valuable words and suggessions !
    thank you all!
     
  2. Mikey
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    Mikey Senior Member

    Big area, ships. Are you talking about sailing or motor yachts, or merchant ships?
     
  3. pavel915
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    pavel915 Senior Member

    I want actually imformation about Big merchant ships!
     
  4. dougfrolich
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    dougfrolich Senior Member

    Look for a book called "Stability and Trim for the Ships Officer" by John La Dage and Lee Van Gemert
    Library of Congress Catalog Card No. 56-6885
    My edition is from 1959, but it is still the most complete ref. regarding ships stability IMHO
     
  5. Tim B
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    Tim B Senior Member

    "Basic Ship theory Vol 1&2" by rawson and tupper are also good texts, as is "Ship Hydrostatics and Stability" by Adrian Biran.

    Tim B.
     
  6. Mikey
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    Mikey Senior Member

    Also try searching the internet for courses in ship building on universities, quite a few of them has good course material that is freely downloadable. American universities could have quite a lot, try searching for stability and explore links to .edu sites

    Mikey
     
  7. Guillermo
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    Guillermo Ingeniero Naval


    Pavel915
    First of all you should read some basics on Stability of Ships, if you have not done that yet, as suggested by the other fellow posters. There are many good books on the matter. Designing with Maxsurf, Rhino or whatever other program will not produce an stable boat by themselves, if you do not know the basics. Remember stability is not only a matter of forms, but also of weights, so you need to as accurately as possible know the COG at the lightship condition and then all cargo conditions and their respective COGs

    About the stability criteria to be complied with for all kind of merchant ships (including fishing ones) you'll find what you need at the IMO's "Code on Intact Stability for all types of ships covered by IMO instruments" 2002 edition. You should also take into account that for most big ships it is mandatory to also study flooded stability.

    Cheers.
     
  8. pavel915
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    pavel915 Senior Member

    dear all,
    thanks for your advices.
    actually i have studied tha basics of statical stability and stability at large angles , cross curves very well and understand them good!but dont know about damaged stabilty and flooded stability.
    now I will make a more specific question ,,,, that is-
    when I go for designing the hull in maxsurf , I try to keep my to a good stability,
    so then i frequently chek for tha hydrostatics when making the hull, I want to know about some points i have to keep in my mind when making the hull ,
    while modeling the hull I try to keep the value of KM( GM+KG) as high as possible, as i know that ; the initial stability = GM*displacement*sin(angle)
    I dont know how much right my process is;;; I want to know from you that; while I am going for making hull in maxsurf; in which parameter , and in which point should i concentrate? Is there any trick or thoroy to predict the stability just seeing the hull form and hydorstatics in maxsurf?
    Thanks to you all!
     
  9. Guillermo
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    Guillermo Ingeniero Naval

    Well, in my opinion no, neither in Maxsurf nor in any other programs. You need to know KG, as said before, and even then having a look at KM and comparing with KG only gives you a clue to initial stability, but not to ultimate one.

    Having said this, there are some parametric rule of thumb criteria that may be applied to the different types of merchant ships. You should look for that kind of info at the first stages of a design. I don't know what books and papers you have available, but as an example I have at the office an spanish book named 'The basic design of merchant ships' (Ricardo Albariño et al.) I know there are other books similar to this one, but I don't remember the titles now.
    Cheers.
     
  10. tananaBrian
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    tananaBrian Junior Member

    I'm confused. If your school has you calculating GMt (KMt etc) and you have a design project coming up, then why haven't they covered the basics of form and weight stability and how varying both impacts the ship's stability? And if they have, then I would suggest you go back and give it some more thought on your own so you learn to reason through the issues without having someone hand you answers. Sorry to be so rough, but I think the best way for you to learn about stability is to go vary those factors on your own and witness the results yourself. The software's making it to easy for you I think.

    As far as stability when downflooding is occurring, I know that I once found an excellent 300-page (or so) training document from the US Navy on ship stability and it included a LOT of info on damage and the results on the ship's operation and stability. After all, navy ships do get damaged, right? But in any case, I'd seriously go back and draw some drawings, vary the parameters yourself, and then see the affect on GZ v. Heel and initial stability curves and on GMt. I really think you should do that before getting too much further. A good weekend ought to be enough time ...plenty of time.

    You should also understand how a boat heels in response to various sea states versus the transverse metacentric height ...What kind of GMt will be too stressful on the boat? What kind of GMt will make people sick? What kind of GMt risks using up 90% of your freeboard every time a swell passes by? How do you know if you've come up with a "good" GMt or not? What can you do to correct each of these situations? Draw pictures and make sure you understand what a higher or lower GMt really means in terms of the ship's response to wind, waves, and swells and how you go about changing a boat's GMt.

    One hint that I will give you however is that you should, and this is a very strong suggestion, get as much stability information as you can from ships that are similar in size and arrangements and type as that which you will be designing. On some numbers, there isn't any perfectly correct or perfectly wrong answer and you should aim for solutions that are similar to known-successful ships instead ...or start there and vary if you must, being able to explain exactly why you chose to vary.

    Most of all, have fun. These ARE the good ol' days.

    Brian



     
  11. tananaBrian
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    tananaBrian Junior Member

    PS: By the way, your statement "while modeling the hull I try to keep the value of KM( GM+KG) as high as possible, as i know that" is a wrong answer ...do you know why?

    Brian
     
  12. Ironmaster
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    Ironmaster Gold Member

    Hello everybody!!!

    I guess I have quite similar aims as Pavel. I want to design sailboats....or "unpowerboats" as I prefer to call them. However before being able to do that properly I need to absorb more knowlegde.

    What books on boatdesign/yachtdesign are the ones that the professionals and students here would particularly recommend?

    Also......as someone has suggested some universities might have some high quality teaching material/course material available on their websits. Maybe we should work together and create a thread which compiles links to the best university URLs?
     
  13. tananaBrian
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    tananaBrian Junior Member

    As you'd guess when there are so many years, truly ...centuries, of displacement hull design in this world, there are a lot of books to pick from. One that I find is a good start for people yet dives deep enough to be useful is:

    Preliminary Design of Boats and Ships, by Cyrus Hamlin, N.A.
    ISBN: 0-87033-391-7

    That said, you should also study beams and plates, deflection, basic mechanics of deformation and deflection, etcetera. Dave Gerr has reasonable rules of thumb on scantlings and generalized scantling calculations in his book "The Nature of Boats". There is also Ted Brewer's book, "Ted Brewer Explains Sailboat Design". Or "Skene's Elements of Yacht Design", etc etc.

    Have fun!

    Brian
     
  14. MikeJohns
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    MikeJohns Senior Member

    Ironmaster

    Download the ABS scantling rules (free from eagle.org) for offshore racing yachts(ORY). That will explain the structural requirements, then get hold of "principles of yacht design" Larsson & Eliason as they apply ORY to a demo design.

    Then read "Seaworthiness the forgotten factor " by Marchaj

    Also I would recommend "Design of sailing yachts" by P Gutelle which is an organisation of Marchaj's more scientific works.

    Once you have that lot under your belt you can start asking some deep meaningful questions here.

    Good luck
     

  15. Ironmaster
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    Ironmaster Gold Member

    Thanks for the hints

    Mike & Brian,

    Thank you for the hints on books. Currently I am reading The Nature of Boats by Dave Gerr. It´s seems to be a good place for a novice start. I plan to obtain copies of the books you suggested. This garantees I will have some good stuff to read during the cold an dark winter (while other members of this forum are cruising their yachts in the South Pacific or the Caribean).

    Fair Winds

    Ironmaster
     
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