Yacht General Arrangement

Discussion in 'Boat Design' started by monrosm@shrewsb, Mar 28, 2014.

  1. monrosm@shrewsb
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    monrosm@shrewsb Junior Member

    Simple question, why are general arrangements drawn with the bow facing the right hand side of the drawing?

    I am sure there are exceptions to the rule but a quick Google shows about 98% of drawings are done this way. (see image attached?)

    Many Thanks
     

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  2. philSweet
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    philSweet Senior Member

    Not sure why. but it would help with the lofting process, to not need a left and a right handed lofting floor. So maybe there was actually a requirement in the old British naval procurement system to do it that way.

    It might also date back to the earliest printing systems, where engravers established standards to make their life tolerable. It was a horrible job to be a plate engraver. They were usually very good artists, but often worked 16-20 hours a day cutting plates for the old presses. They had to make reverse images, also. This led to standards so people didn't complain things were backwards. Animal illustrations are the same way. Old shell books all show right hand spiral shells, even though almost all shells are lefties. The engravers had a lot of leeway in terms of how to represent details, textures, and shadows, and these sort of standards just made it much easier to be productive after 18 hours of tedium.

    One other observation - on a blueprint, the title box is in the lower right and takes up a fair amount of space. It is easier to lay out a boat on the left pointing to the right with the bowsprit sticking out over the title box.
     
  3. rxcomposite
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    rxcomposite Senior Member

    I guess it depends on what country the drawing originated from. In my stint as a surveyor, I have seen some GA drawn with the bow to the left and they have been drawn by prestigious Marine Engineering firm.

    I once asked this question and Ad Hoc explained who does what but I lost the link. It was a very long time ago. All I can remember is there is no standard.
     
  4. SleepyOldDog
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    SleepyOldDog Junior Member

    From my old PNA (1967) Chapter 1 Section 1 Para 1.2 Arrangement of the Lines Drawings ... "In the sheer plan, the ship is usually shown with its bow to the right. ..."

    I don't know of any other reason for this industry convention.

    But, just to make it interesting, submersible vehicles are "typically" shown bow left on the lines drawings. Why? Just because that's the way Rickover and GD/EB did it on the Nautilus? Now, does anybody have a drawing of Bushnell's "Turtle"? (Google images: Bow right?? I guess David Bushnell didn't get the memo...) Or, was Jules Verne's Nautilus drawn bow left?
     
  5. Eric Sponberg
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    Eric Sponberg Senior Member

    From my experience, in America, boats are drawn bow to the right. In Europe, the norm seems to be to draw boats bow to the left. I think this is just convention that has evolved over time. Personally, I draw my boats bow to the right.

    Following that logic, one wonders why boat designs from New Zealand and Australia aren't drawn upside down??? Or maybe the Aussies and the Kiwis think we draw our boats upside down.

    You can usually tell how sweet looking your design is, aesthetically if, after you draw it, you flip the drawing end for end. If the design makes sense to you and is appealing in the reverse image, then it is probably a good looking design--universally.

    Eric
     
  6. Olav
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    Olav naval architect

    I'm sorry, but I have to dissent. All drawings from European design offices, yards and other sources that I am aware of and use in my daily work show the bow to the right (exept for the case that the port side of the vessel is of importance and has to be shown on an additional sheet). A lines plan would therefor show the port side of the vessel.

    Common practice is to have x positive to fwd, y positive to port and z positive upwards. The origin is then the intersection of axis of rudder stock, centreline and baseline (usually at the upper edge of the keel).

    Right now we're working on an project with an American yacht builder and still have to get used to a coordinate system contrary to what we are familiar with (they use x positive aft, y positive to starboard and z positive downwards, with the origin at the fwd perpendicular and with z = 0 at the design waterline).

    Just my two cents...
     
  7. Eric Sponberg
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    Eric Sponberg Senior Member

    Well, first that's nice to know that European designers design bow to the right. Although, I do see a lot of drawings (publicity drawings, admittedly) with the bow to the left (do the magazines like to flip things around???)

    I was trained with a coordinate system to start at the forward end of the waterline--Stattion 0. Positive X goes aft, positive Y to starboard, and positive Z goes up from the base line, and the base line is below the hull, not necessarily tangent to the bottom of the hull, but frequently so. You designed your hull to either 11 or 21 stations of equal increments so that you could easily calculate hydrostatics by hand using Simpson's Rule. Now, in 3D drawing, waterline length doesn't mean very much and you are not restricted to equal stations. So my X position is at the extreme front end of the stem, on the hull centerline, and the baseline is tangent to the bottom of the canoe body. The origin is where X and Z intersect at the baseline, X is positive going aft, Z is positive going up through the hull, and Y is positive to starboard.

    Eric
     
  8. Olav
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    Olav naval architect

    Eric,

    maybe there's some difference between small boat designers and people who make their living in the commercial vessel or superyacht industry (the latter is where I bring home the bacon).

    Magazines... well... They often modify the drawings they get from yards and designers and make them more easily readable for the average Joe (i.e. colourized with shadows and highlighted areas etc.). Maybe they also flip the direction of the bow, which may be due to layout considerations. As you probably know or have noticed, photographs of people are usually arranged in such a way that the person looks towards the binding and not "away" to the outer edge of the page and thus "out of the magazine". I can imagine they sometimes apply the same principle to boat drawings. ;)
     
  9. DCockey
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    DCockey Senior Member

    The majority of small boat plans I've seen (generally under 65 ft / 20 m) have the bow to the right but a few, particularly plans from the early 20th century, have the bow to the left. Several designers such as Starling Burgess have used both bow to the left and bow to the right.

    "Bow to the right" appears to be have been the established convention for large vessels since at least the end of the 18th century. All of H. F. Chapman's plates in Architectura Navalis Mercatoria have the bow to the right as well as other 18th century drawings I've seen photos of.

    The coordinate system with the origin at the fore end of the design waterline as described by Eric appears in a number of texts and references on small craft design by European as well as North American authors.

    For larger vessels there does not appear to be a firm consensus on where to start numbering stations from, the forward perpendicular or the aft perpendicular. Principles of Naval Architecture, Volume I, 1988 says:
    Body plan stations are customarily numbered from the bow, with the FP designated as station 0. In Europe and Japan, however, station 0 is often located at the AP, with station numbering from aft forward.​

    ITTC Symbols and Terminology List Final Version 1996 is silent on station numbering and provides alternative terminology for defining hydrostatic locations as distance from forward and aft perpendiculars respectively; for example
    XAB Longitudinal center of buoyancy from aft perpendicular Distance of center of buoyancy from aft perpendicular
    XFB Longitudinal center of buoyancy from forward perpendicular Distance of center from forward from forward perpendicular

    ITTC Symbols Version 2008 provides definitions for centers based on a "reference point"; for example
    XCB (ships, hydrostatics, stabil-ity) Longitudinal centre of boyancy (LCB) Longitudinal distance from reference point to the centre of buoyancy, B
     
  10. rxcomposite
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    rxcomposite Senior Member

    Getting HOT. Now we are into station numbering. From FP or AP?

    And nobody said about the station/frame to be of equal spacing except for the convenience of using the old system of Simpson's rule.
     
  11. viking north
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    viking north VINLAND

    Could be nothing more than the majority of engineering/drafting is carried out by right handed people,we read from left to right thus point the vessel in that direction subconsciously orienting it for what it is deigned to do " Go to Sea, away from the viewer. In comparison have you noticed many, possibly the majority of old sailing ship paintings are shown bow pointing left toward the viewer as if returning home , back to port.
     
  12. rxcomposite
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    rxcomposite Senior Member

    Could there be a connection? The Japanese reads from the back to the front. And yes, the Arabs too.
     
  13. rxcomposite
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    rxcomposite Senior Member

    If it is pointing to the binding center, it is "going in". If it is pointing out towards the papers edge, it is "going out". ;)
     
  14. rasorinc
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    rasorinc Senior Member

    It is all very simple of course. It is based in the ancients study of the relationship of the Earth relative to the Moon and the Sun according to Plato's great friend Mercury. Good Night all.
     

  15. PAR
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    PAR Yacht Designer/Builder

    It's simply traditional and there's no good reason for this orientation. I find it easier to view lines with the bow facing the left, but am accustomed to bow right too. It might be that the Admiralty insisted on it a few centuries ago or something equally as devious, but not as probable as one might think.
     
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