How big can a yacht be (max length) and why (CFR, etc..)?

Discussion in 'Boat Design' started by Smoothride, Sep 29, 2006.

  1. Smoothride
    Joined: Sep 2006
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    Smoothride Dog Owner

    Hello All;

    How big can a yacht be (max length) and why (CFR, etc..)?

    As I'm sure you guessed, I'm a new student, and wonder what a non-NA, read that Yacht/Boat designer can use as a max length we're allowed to design to...?? Do the figures change if it's used commercially, for passengers, or for fishing or towing? I'm sure this gets very technical, but salty designers may be able to come up with a rule of thumb for me/others.

    This is a question I've pondered lately. I've read/heard 198 feet max. I just read 125 feet in a textbook. Is there a CFR that dictates the max length?

    I was on the Star of India the other day, found she was about 205 feet long, and wondered if I would ever be allowed to design her, theoretically. Hmmmm...

    This is meant to be a fun question only!! ;)

    Good Times,

  2. Dan S
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    Dan S Junior Member

    are you asking if at a certain length, its considered a ship, and not a yacht?
  3. MikeJohns
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    MikeJohns Senior Member


    You can design what you like, but unless you are an Engineer you will need to get commercial vessel design certified usually by one of the societies and design to their rules rather than submitting specific calcs.

    Where's Kalifornia?

  4. Smoothride
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    Smoothride Dog Owner

    Mike and Dan;

    Kalifornia = a movie from a while back, but I'm living in Socal right now.

    Yes sir, I should have put in the post "where does the ability to design a yacht end (for yacht designers), and where does a the ability to design a ship begin (for Naval Architects)?"

    So where do people get 198 feet or 125 feet?

    Roger that, I am an engineer, but that was 11 years ago, I'm not a PE or anything, at least not yet. I may have to try and take the FE/EIT exam at some point, and then work in a design office to get my PE some day... Then I would be pretty complete. Until then, I wouldn't be able to do anything with ships, I believe, and that's where I'm coming from with this question. Is that about right?


  5. alienzdive
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    alienzdive Junior Member

    A good theoretical answer to your question would be along the lines of this.

    The largest single masted superyacht is around 160 feet, can not remember the exact length. However the stresses involved on the rig and winches for example were theoretical and never tested. The manufacturers of various products had to invest much money and time to develop new products. This was all added on to the cost of the boat. The owner was happy to pay for the r&d so that he could have the biggest. Many new concepts had to be devised for this to eventuate. There will always be someone coming out and asking for bigger, but this would require much more investment again. The technology is now there because of this to build to that length. However to go further will require a new billionaire with a large wallet to commision such a vessel.
  6. Smoothride
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    Smoothride Dog Owner

    For commercial purposes (say, for fishing vessels), is there a limit imposed upon yacht/boat designers?

    For instance, if some Russian fishing company wanted a 210 foot vessel, could a non official naval architect do it?
  7. Raggi_Thor
    Joined: Jan 2004
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    Raggi_Thor Nav.arch/Designer/Builder

    I think anyone could do it as long as a classification society (DNV, Lloyd's or similar) could approve it OR you didn't need insurance :)
  8. CDBarry
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    CDBarry Senior Member

    The rules regarding engineering licensure are up to the locality. California does not license naval architecture or control it.

    The applicable Coast Guard regulations depend on many issues of size, service regulation, etc. US Fishing vessels over 24 meters have to meet stability requirements of 46 CFR 28.500, etc. and some states might interpret preparation of the calculations as requiring a PE, though this is also subject to various exemptions. This regulation (and probably international homologized regulations as well) also requires that the vessel have one compartment subdivision, and certain other aspects of stability which yacht designers are not generally capable of handling.

    Many entities obtaining vessels, though, may require PEs independently - underwriters might require PEs to sign off stability calcs for fish boats, for example, at least one major US superyacht builder wants all work signed off as well, and I got my first license when the firm I worked for got a contract designing a fireboat which had to be certified by a PE (we had several, so it wasn't an issue, but it was a lesson for me).

    A yacht, which is by definition a pleasure boat, can be any size, but also, they are often registered as commercial vessels, which may require some special certification. Most super yachts are MCA certified as small passenger vessels, for example, which allows them to be chartered more easily.

    So, for example, a pleasure boat registered as such can be designed by anyone up to a fairly ridiculous size, but a small passenger vessel over 49 passengers regardless of size, requires submission of calculations using skills that typical yacht designers won't have, as does a submarine taking a single passenger for hire.
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  9. Smoothride
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    Smoothride Dog Owner

    CD Barry;

    Thank you sir, very much for the imformative reply. I wasn't totally sure which CFR to reference, but you have enlightened me (I'm used to 46 CFR part 61/91/135 etc...).

    While working for a small boat design office (, we had a subcontractor do intact damage stability. FE analysis was also done by a sub. for loads imposed on the structure/skin (it was all carbon fiber). This was to be a navy demonstrator for a new hull form.

    Thanks again for the reply sir, as always, your viewpoint is right on the money, and is very insightful to myself and others! :)

    Best Regards,
  10. webbwash
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    webbwash Junior Member

    the size of a "yacht" can only be related to the depth of your pockets --

    Onassis had a very healthy pocket book as well as being well connected in the shipping industry and therefore his "yacht" was rather like a medium sized passenger ship, but it was still a "yacht" for PERSONAL use, unlike said passenger ship which is for hire and usually for a corporation or business.

    "Christina O" at 325 feet was considered one of the premier yachts in the world for her times and continues on today --

    So do you want to build a ship or a boat which can be carried aboard a ship or just some holiday junket seeker for the nearly rich and quietly famous.

    Anyone can build a boat -- it takes a craftsmen to build something to stand the test of time. Design away and then get the Classification Societies to sign off on it and you won't need to get the PE license, just know that it may be a lot easier if you do have it, or at least the training and experience, to discern if the people you have hired are doing the job they were asked to do.
  11. china
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    china Junior Member

    the word "yacht" originates from the word "jat" pronounced "jot" an old viking word for fast hunter. as they used their boats for battle and hunting. so even if your ship is big, as long as it is a fast hunter i supose you can call it a yacht.
  12. marshmat
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    marshmat Senior Member

    Sr, to add my thoughts on your original question:
    Once a certain level of complexity is reached, it's generally not possible or practical for one engineer or architect to design the entire boat. On a superyacht, the lead NA might do the hull, the styling, the general layouts, and the general structure- but there's also the engines, the piping, the electronics, the ten thousand subsystems, all of which are designed and double-checked by other engineers working under the lead NA. By the time you get to be lead NA on such a project, you probably have decades of designing experience under your belt. The classification societies have to be appeased, in addition to the designer having confidence in his work and having the qualifications to be there. Engineering a megayacht is never the work of one person. When there's 75 lives and $100 million of boat on the line, no engineer worth his salt will work on his own.
  13. SteamFreak
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    SteamFreak USMM

    He hits the nail on the head... as long as the vessel is not intended commercial use and insurance isn't something your interested in, a yacht can be as big as you like... but in reality, 200 feet is a huge undertaking and a firm understanding of material strengths and stresses, as well as stability. Even in the Med and Carib, you don't often see vessels much larger than 150' just because the cost of building and operating such a boat, much less keeping it in good shape.
  14. Smoothride
    Joined: Sep 2006
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    Smoothride Dog Owner


    Thanks for the replies gentlemen! No way would I ever take on designing a 200 foot anything alone; just seeing what types of vessels I'd be able to help design/attractive to an employer to help design. I'm a big fan of having at least two sets of eyes scan everything in the industry I'm in.

    I have a definite interest in the design of commercial boats and eventually, ships. I think I would really be satisfied by a career where I helped design both in that order. Along the way, I'll have to update my engineering degree, take the EIT/FE test, and eventually PE. Good times.

    I haven't had coffee yet, so I hope I don't sound drunk...


  15. dskira

    dskira Previous Member

    The real question is :How large is you bank account :?: :cool:
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