Taking the lines of an existing hull

Discussion in 'Boat Design' started by waterman, Aug 9, 2005.

  1. waterman
    Joined: Feb 2004
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    waterman Boat Geek

    I'm looking for the procedure of taking the lines of an existing hull. I would like the procedure/ methodology to be clearly defined, from set-up to actual measuring. Does anyone know of a post or website elaborating the procedure?
  2. ErikG
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    ErikG Senior Member

    This subject have been talked about quite a lot in these forums.

    SPLASHING a design is not seen to friendly around here as someone most certainly owns the design in question and would be happy to sell you drawings for it.

    If it's for a design where the designer is no longer alive then I'd advise to get in touch with his/her relatives and ask for permission.

    If it's a really old design chanses are that the drawins are kept at a maritime museum or equivalent and you should contact them for furrther info.

    Not trying to be a prick here, but designers design boats for a living, and Using their designs without permission is not at all very nice.
  3. Thunderhead19
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    Thunderhead19 Senior Member

    Not that I want to encourage "Splashing", but sometimes it is necessary to reverse loft the lines down to the floor. Especially when a boat needs extensive repairs, or it was built one-off and proper drawings either no longer exist, or were never made in the first place. The british admiralty used to do this all the time. Most ships were built without drawings in the early days of fighting sail, and each time the admiralty aquired a new ship, it's lines were taken down and a complete set of drawings was made. I do it all the time, because the people I have worked for people who think planning and pre-design are a waste of time, and that actual building is the only "real" work.
  4. fcfc
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    fcfc Senior Member

    I do not remember where I saw this article (french or german web), but it spoke about digital camera (not too many pixels, in the 3 million range, if memory good, but with a very big image captor, not the usual (even high) end public camera). and a specialized software. They put about some dozen of marks on the hull, take some snapshosts at various angles. (total duration about half an hour), involve no measurement at all). put all snapshots in the PC, and then got within minutes the (nurbs) lines of the boat within an accuracy of 0.1 inch. Could even take partial lines from a wreck.

    The paper was written by an expert for forensic analysis after accidents.
  5. Thunderhead19
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    Thunderhead19 Senior Member

    I remember that website on photogrammetry. The other option is a software package called Photomodeler. It's just all so expensive and bothersome. All it takes is a plumb bob and line, a sharpie, a friend and a long measuring tape. A laser level or laser line helps and they are inexpensive. The other option is using a theodolite (transit level) .
  6. RThompson
    Joined: Nov 2004
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    RThompson Senior Member

    As ErikG and Thunderhead have said: Splashing a design is TOTALLY uncool.
    once upon a time it may have been standard development procedure for some people.
    Other people put a lot of effort (and money) into devising the optimal set of compromises for their given problem. To copy it directly is nothing less than common theft. Having said that, there are legitimate reasons to measure a boat.
    Also, I challenge anyone to come up with a (new) original idea... :)

    AH HAA! you are not alone!
    In fact my experience is that there are many builders using the Visual Engineering approach to design (incorporating an eye-ometer and precise Arm Waving), as there is builders using the latest pencil and paper. Heck, some mad futurists even go to the extreme of an electric calculator, EVEN A COMPUTER!!! (but I think thats just a bit of a fad)

    I measure lots of parts besides hull shapes, I'v tried so many methods - digital scanners, elaborate frames, straight edges and string lines, large squares and tapemeasures - all sorts of things.
    It has boiled down to two options.
    1. Spend the money and contract/hire a 3d laser scanner, then measure as many things as you can in the time available ,take lots of notes.
    2. Spend the time to ACCURATELY and PRECISELY measure using string lines, plumbob's and squares. Each object will probably require a different approach. It tends to be easier if you have a female mold available.
    For a hull I would suggest learning how to draw hull lines first. Once you know that - with a bit of lateral thought you will find a way to take lines off a hull using whatever you have at hand.
    I'v tried using camera's and photo type modellers. It seems you have to spend significant money for it to be effective.
    Sorry I'm not more help than that.

    ps what I said about computer design being an extreme thing to do? Mmm, I may have been pushing it a bit... :D
  7. waterman
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    waterman Boat Geek

    Keep to the question, don't make up scenarios

    Thanks to all who answered the post.
    Not to be a prick here, but there are many other reasons besides "splashing" to take the lines of a boat.
    Photogrammetry is an easy solution that I ultimately will pursue due to accessibility of good equipment.
    However, what I was seeking was old school knowledge and a set of clear procedures. I've read several articles on the topic, however, they often are light on key parts of the setup and details.
    Actually, the procedure isn't that hard, I just didn't want to re-invent the wheel and repeat mistakes (waste time).
  8. gerson
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    gerson New Member

    try to create a tri-dimensional grid and then measure the values of each 60 cm lwl(the straight line).
    you are going to draw a lot of sections and plans but then you can rebuilt the specific part of a vessel.
    it"s like modelling.
  9. Nautiscan
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    Nautiscan New Member

    Nautiscan is specialized in boat reverse engineering.
    we use laser tracker technology for make precision design of existing yacht.

  10. Raggi_Thor
    Joined: Jan 2004
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    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    For small open boats one method is to use a line from stern to stem and measure distances and angles from this line to each chine in a hard chine boat like Norwegian lapstrake (clinker) rowboats. This method is used by museums to document historic crafts.
    For larger boats a vertical reference plane parallel to the keel is used with a laser measure (don't know if you call it that).
    You can measure distances in a grid pattern (waterlines and stations) or just make a "point cloud" to use in for example Rhino to recreate the shape.
  11. Nautiscan
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    Nautiscan New Member

    The used method depends on the result that is wanted to be obtained. Nautiscan guarantees inferior errors of measurement to 0,2 milimeter for the entire boat and of 0,005 milimeter for the single point.
  12. longliner45
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    longliner45 Senior Member

    when you go to work ....do you exspect to be paid?I always try to put myself in the other guys shoes. and never do anything that I cant look at myself in the mirror over. stealining a candy bar is wrong no matter what you say or do to justify it ( had a good *** wippin fer that at 9 yrs old) what Im saying is is that these guys make their living by design. It may seem minor but somewhere down the line your taking food out of thier babys mouths.I dont think your a bad person .your just trying to get by cheap, thats ok, but if you ask ,,,,,,,they will probably give it to ya fer free.be good .longliner
  13. Guillermo
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    Guillermo Ingeniero Naval

    As other posters said before, "Splashing" is not the main reason for a hull's measurement. Hull repairs, racing VPP or stability assesements are quite common reasons to measure a hull.
    Some of the wooden boatbuilders I know do not follow lines plans to build the boat, but half models. From those they take the frames profiles to build, but usually they adjust bow and stern sections on the real thing with battens. So, in order to be sure of lines before assessing stability for those boats, I usually check the sections. Also sometimes is needed to get the lines plan for an old boat with no drawings available at all, etc. Not to say if you are an IMS measurer, dealing with an unlisted boat model.
    Depending on size of the boat and precision wanted, diverse measurement tools are needed. The most precise are laser scanners of millions of points, but their very high cost is almost impossible to justify for a NA usual work. Topography instruments and some industrial laser measurers are other options quite less expensive, but anyhow not so cheap.
    To measure a boat of, let's say, 20 m length and 3 m moulded depth, the use of pendulums, strings, battens, levels and the like is quite difficult, may times needing scaffoldings and manwork, not always available on time when you have to measure a hull between tides in a ramp or when in a boatyard where other works are taking place.
    So I conceived and built a simple and efficient measurement tool using a laser distance measurer (0,5 mm precision, 30 m reach in daylight), firmly fixed to a digital angles measurer (0,1ยบ precision) and then mounted on a topography tripod with levels. The apparatus is displaced along a parallel (or even dodged) line to the CL of the boat at a known distance, carefully positioning it at every section wanted. Several measurements at each section are gotten, from keel to sheerline, and then, thanks to a very simple Excel sheet, converted from polar to XY coordenates later used for CAD drawings. Physical construction of the apparatus induce some corrections to be introduced to get accurate results, as well as an initial calibration against a known coordinates point at every section ('hand' measured).
    It's cheap (the whole bunch costed less than 500 bucks), easy and quick to use (much more than pendulums, meters and the like) and with enough precision to my purposes.
    Is needed to say a reasonably good flat ground surface is required to get a satisfactory result. Keel or designed water level angle to horizontal, require to be considered also when transporting points to the CAD drawings.
    As an auxiliary tool I use also digital photography for bow & stern profiles, and other details, working afterwards over them with CAD.
    I hope this helps.
  14. dereksireci
    Joined: Jun 2004
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    dereksireci Senior Member

    3D Measure

    If you don't mind paying somebody, go to 3dmeasure.com.

    He did some high performance stuff for us and I think it was pretty good.

    I saw a method of doing it by setting up a grid on the floor and using an articulating arm to get the points. I think it was in one of my wooden boat books. I'll look in my stack.


  15. water addict
    Joined: Jun 2004
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    water addict Naval Architect

    are the original lines not available from the designer?
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