Design database

Discussion in 'Boat Design' started by Robinfly, Jan 25, 2020.

  1. TANSL
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    TANSL Senior Member

    @Robinfly, I can not agree more with you. We must forget primitive methods, totally obsolete.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    It is only as reliable as YOU wish to make it. It is your database so you're in control of its reliability or otherwise, no one else!

    So the database (that you want) is ostensibly a means for you to perform some kind of statistical analysis?

    This does indeed suggest that you're more interested in the 'numbers' for a statistical analysis, than real Design per se. An analysis of the type you are eluding to, is for those without any knowledge of said design that is being requested. Hence the need to "get some numbers" as your starting point. Remember, it would only ever be a starting point, not the end point for your design. It is a good way to start, but don't forget, these "numbers" only convey to you, just that - numbers. It is not a finished or complete answer/design.

    Trends has 2 different meanings here.
    1 - as fashion. Something that is flavour of the month, it becomes a 'trend'...then a few months later or so...gone.
    2 - a statistical definition, implying a suggestive route/answer between sets of or beyond sets of data as such.

    If 1, then these becomes statistical anomalies in your database and without knowledge of the designs and why they are as they are, it'll confuse you.
    If 2, it just provides you with possible options which lay outside your set database.

    I would suggest, you are overthinking this database and its importance. The more designs you do in your career, the more you'll understand that the database of previous designs, is a record, a time line of information from start to finish of the hows and whys and what did or didn't work, and not a series of absolutes, as just 'pure' numbers implies.
     
  3. DCockey
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    DCockey Senior Member

    What is the availability of data on hydrostatic characteristics of vessels to third parties, ie neither the designer, builder or owner?
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Minimal at best.
    You'll only ever get, if you're lucky, the displacement and the draft at that displacement.

    Look at the endless conflicting information, or rather lack of, on this thread of a well document boat. Sales values,/published values are invariably not correct.
     
  5. TANSL
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    TANSL Senior Member

    It is worth remembering here what some call the spiral of the design process, which means that, starting from certain values, the project revolves around itself, changing and refining the initial values. And I say this because I don't think that starting with certain relationships between the different dimensions and the various parameters that define a project is a serious mistake, but quite the opposite, is the procedure to follow.
    What are the correct relationships? Sales values, / published values are invariably not correct, I would not say so much, but that does not mean that they do not serve to establish initial starting values?, at all. And, on the other hand, how many designers, without 30 years of experience, make great designs? Well, I'm going to answer: the majority.
    So, @Robinfly, go ahead with your database project and don't let yourself be influenced by negative opinions that have no basis. If what you want to do is too complicated, you will realize it yourself.
     
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  6. JRD
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    JRD Senior Member

    Speaking as an ordinary (not naval type) engineer. For your first professional project focus on your systems and project management. Project filing, drawing standards, revision and change control, quality control, effective communications with your client and suppliers etc.

    Until you have several designs complete you won't really know what's worth comparing (from experience)

    Trying to create a multi factor analysis to compare objects made up of multiple 3d surfaces all operating with different mass properties in different fluids will take more work than your design. And you wont know if it works until you have completed at least two designs.

    Spreadsheets like excel are good for analyzing data but have little integrity for data management and not good at creating standard reporting and data entry.
    For storage of basic project and design data you could use ms access but a learning curve if you haven't used it before .

    Good luck with your project.
     
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  7. fredrosse
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    fredrosse USACE Steam

    I collect old books, and many have spreadsheet type data presented, for ships, boats, locomotives, engines, etc., etc. These spreadsheets gave designers a "sanity check" as to what is reasonable, and what was not such a good idea. If you want to compile a database for existing designs, you should probably start with three or more hull types (Displacement motorcraft, Displacement Sail, Planing Motorcraft, etc.), then assemble the parameters relevant to the hull type you are examining.

    For my crude study, I am interested in normal displacement motorcraft, and my spreadsheet lists:
    Length, Length Waterline
    Beam, beam Waterline
    Displacement, Light, Design Load, Heavy
    Draft
    Area of Waterplane at air-water interface
    Mid-ship Section Area, below air-water plane
    Speed in Knots
    Actual hull performance numbers for comparison

    From this data, the relevant engineering/design parameters can be calculated, such as:
    Speed-Length Ratio
    Block Coefficient
    Mid-ship Section Coefficient
    Prismatic Coefficient
    Water Plane Coefficient
    Displacement Length Coefficient (100 ft equivalent)
    Admiralty Coefficient
    Calculated Horsepower

    Then a similar spreadsheet for propeller design:

    I know there are many many additional parameters that are relevant, that is why becoming a Naval Architect is no small task, but at least this is a start. I have found my spreadsheet is fairly accurate, ranging from my 20 ft displacement steamboat up to the Texaco Georga, a 620 ft tanker I traveled on in the 1960's. You can develop and evolve your specific study area, adding more relevant characteristics, and go as deep (pun?) as you want.

    Good luck
     
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  8. Robinfly
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    Robinfly Junior Member

    Long text but
    Very interesting point of view. Thank you for your explanation.
    May I ask which type of vessels do you design?
     
  9. gonzo
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    gonzo Senior Member

    I think that having a record of construction times and cost is a very valuable piece of information.
     
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  10. Robinfly
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    Robinfly Junior Member

    Many thanks for your advice. I'll definitely keep that in mind.
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    Anything from 5m up to around 70-80m, fast ferries, paramilitary boats, crew boat, patrol boats, house boats, link spans etc..

    The thing about a database, as I have noted previously, it is all about what YOU want the database to be.... Fredrosse above notes the parameters that he is interested in. Thus what are yours?

    But a database like these, are just a series of absolutes. They provide a set of parameters of "similar" types of boats. They are useful for initial guidance, especially in the absence of any starting point of your own.
    But the problems is, as noted above, lets say you want to design a fishing boat. The client says I want a boat that is 20m long and does 35knots. You search your database of Fishing boats, and find that there are none that fall into your client's requirements all are say only 15-20knots - so, what do you do?? Or another client asks for a fishing boat of say 20m, but carrying 100 tonne payload. You search your database again and find that all the fishing boats in the 20m range have payloads of say only 20 tonne....again, what do you do? Do you say to your client - sorry it cant be done, because there are no other fishing boats of that speed, or that payload?

    Of course not. But that is the point of the database, it is just a series of absolutes that convey nothing other than design and requirements, the SOR, of other clients, not yours!

    As JRD notes:
    And so after a period of time, you will start to use that database less and less because you have your own, which also has your own inputs and history of the hows, whys and whens. The important parts of the design that are not so easily tabulated in a spreadsheet. So the database becomes your own database of your own designs which since you have designed them, you have, or should have, near instant recall of what does or doesn't work easily and satisfies an SOR - that's called experience. And if an enquiry and requirement, the SOR, sits outside your now full database of your own deigns, then like the example above...say a fishing boat of 20m carrying 100 tonne....your knowledge and experience of DESIGN, will guide you of how to design it. The database in that sense then becomes superfluous!

    So a tabulated database of other people's designs for other people's requirements is interesting in itself....but how relevant is it to your client and how much will it really assist you in the end? Because take it to its next logical conclusion....if there is one design in your database that fits your client's perfectly...do you copy it...if so, you may be liable for IPR/copyright issues, or, just ask that designer for a copy of the design and pay them royalties?
    Or...
    ...just use your own knowledge and experience from previous designs...and design your own! As a naval architect, that is what you are trained to do...DESIGN.
     
    Last edited: Jan 30, 2020
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  12. rxcomposite
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    rxcomposite Senior Member

    No need to get a database or get a sufficient data of a large number of ships. The work has been done before.

    Principles of Naval Architecture has a table in volume Resistance and Powering by Linblad and Todd. It list the principal dimensions, ratios and coefficients of more than 100 ships recorded. It is a "design lane" from which a range of Cp and length to displacement ratio is given based on speed to length ratio. Similarly, there is also the Watson and Gilfillian line from Practical Ship Design which list a table based on ratios and coefficient and includes bulbous bows. If it is not a ship, W & G list the Cb of boats or types of "slow" boats.

    PNA has a range of hull forms that has been tank tested from displacement hull form, semi displacement, planing hulls, and some catamarans. You choose the hull form based on the Fn you will be operating on. Several hull forms that have been analyzed is also available from SNAME.
     
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  13. Robinfly
    Joined: Dec 2019
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    Robinfly Junior Member

    Thank you for answering and sharing your thoughts.
    Replies from all of you are of a huge help to get better understanding of what approach I should take.
     
  14. JosephT
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    JosephT Senior Member

    If you are into 3D CAD, most of the better solid modeling software offers features to:

    • Define a set of boats, hulls or ships using requirements and design parameters that you define and follow industry best practices.
    • During the design process you can adjust the beam, length, number of decks, bulkheads and MANY other features using these tools.
    • Once you have a baseline hull for each type of boat/ship, you can then easily perform a save as and create new derivatives of each design.
    Additionally, many of these 3D CAD tools are integrated into a design database. Today, these databases are referred to as product lifecycle management (PLM) systems, which automatically build the bill of material when you save an assembly, and does MANY other things too. So if you really want a true design database I would suggest studying the better 3D CAD & PLM systems available on the market. They are becoming more affordable each year for smaller companies. Most medium and large companies use them too. Below is the one I have used the most (NX Ship Design + Teamcenter).

     
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  15. JosephT
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    JosephT Senior Member

    You are correct TANSL. I would start with a small set of project vessels that I found interesting (e.g. canoe, fishing boat, patrol boat, cargo vessel). Each would have its base set of standard design parameters. From here you can make new versions of these vessels. If I were to design larger than a small recreational boat I would manage all the assembly and part files in an integrated database (e.g. PLM system). There is just too much information to keep track of.
     
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