Definition of Sailing?

Discussion in 'Sailboats' started by Kiteship, Nov 25, 2006.

  1. Kiteship
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    Kiteship Senior Member

    I agree with Theo Schmidt (on another server) that, once you get into things like gliding, it's a slippery slope, 'cause you've brought energy storage into the equation. Pretty quickly you're refining and burning dinosaurs and calling it "sailing." Still, what if you time-limited the energy storage--the time needed to "sail" would need to include the time needed to store the energy--or to put it another way; all storage systems shall have the same potential at the end of the "sailing" journey as at the beginning? Peter Sharp's PAS (powered alternate sailing) closely skirts this issue as well.

    (Have we seen PAS here yet? It's the concept of coupling two "saiilboats" together, for instance via an extension cord, then anchoring one (with a drogue, for purists), letting it extract energy WHICH POWERS THE *OTHER* COMPONENT CRAFT. When the "end of the cord" is reached, the two components swap modes, and the entire "sailcraft" moves forward, in increments. Seems silly maybe, but this offers the ability, for instance, to sail dead upwind faster than wind; downwind *much* faster than wind, and other tricks (the bit which is extracting power has no drag--it's standing still, while the moving bit can be heavily streamlined). The version I outline is only one of many--PAS can include purely mechanical linkage, even rigid linkage; the concept is that it alternates between "extraction" and "consumption" modes to increase efficiency. Usually, the "definition" of PAS includes no energy storage allowed, but it's maybe just as "pure" to allow storage, then require the sum total potential to be the same at the "end" as at the beginning. It's thinking about PAS vehicles that's got me thinking about definitions of sailing.

    Interesting that you allow "forces" not "momentum of media," Mal. I assume you're allowing gravity, then? How about magnetic forces? Careful, pretty soon you've got electric motors in your "sailboat." ;-)

    Still, this is the best I've seen so far; I like your deterministic approach, Mal.

    Dave

    I understand your point, but we don't need multiple definitions for things like "lift," "drag," "fly," "asymptote," etc. Why do we need one for "sailing?" (OK, it seems a given to me that we aren't talking about "sail" as in "The cruise ship sailed earlier today") Perhaps I'm presuming here, but the context is moving vehicles via naturally-occurring energy sources; is it necessary--or helpful--to say so?

    We all sort of "get it" that sailing requires two media (perhaps more?), coupled together, and that it requires some sort of "gathering" device in each media. Unsaid is that the two media have to have relatively divergent momentums, or we have nothing to gather. We seem to be approaching agreement that it shouldn't involve stored energy, and (I suggest) staying away from coupled "forces" might be a good idea.
     
  2. MalSmith
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    MalSmith Ignorant boat designer

    Dave,

    It seems to me that the essential aspect of any sailing vehicle is that it has a "sail" of some kind, which is why I think it is important to try and define what a sail is. I've tried to keep the definition of a sail very broad i.e. to use it as an umbrella term for any kind of device that creates a force by effecting the momentum of a moving fluid. The fluid can be a liquid, a gas or particle stream, in order to encompass the the broadest use of the term. Perhaps it would almost be sufficient to define a sailing vehicle simply as "any vehicle which uses uses a sail to obtain it's motive force".

    Nautrally the motive force will react against another force. For a leaf being blown in the wind, the force reacts against the momentum of the leaf itself (while it is accelerating). However, we wouldn't really consider this as sailing, because the direction of motion of the leaf is not controlled. We design a sailing vehicle so that we can arrange the reactive forces in such a way as to be able to control the direction of travel, subject to the limitations of the system. In addition to this, there is usually a system for the fuction of maintaining stability. Perhaps then the essential features of directional control and stability control need to be included in the definition (depending on what you want to use the definition for).

    I don't have a problem with including gravity (gliders, solar ships), momentum(gliders, solar ships), magnetism (sail powered magnetic train??), friction (land yachts), bouyancy and of course fluid pressure as some of the possible reactive forces. Note that a "normal" sailing boat uses fluid pressure to control direction and a combination of gravity and bouancy to control stability (pitch and roll).

    Mal.
     
  3. rayk
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    rayk Senior Member

    A boat from a hundred years ago is sailing dudes. That is the root.

    Define that first and then figure out if the rest of the exotic rubbish is like sailing.

    Define *pointy head* :p
     
  4. longliner45
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    longliner45 Senior Member

    rayk ,,,your just twisted enough to be a sailor.......longliner
     
  5. Kaa
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    Kaa Wanderer

    We don't need multiple definitions for words like "lift" and "drag" because there is a very clear implied context for them -- that of physics, and specifically aerodynamics. Specify just as a clear context for "sailing" and the definition will be easier to come to.

    Generally speaking, there are two reasons for definitions. Reason one is clarity of thinking. When your mind manipulates concepts, having a well-drawn boundaries around these concepts helps a lot. This works in reverse as well -- vague or just muddy definitions lead to muddy thinking and lots of problems.

    Reason two is communication. When people communicate, they have to agree on the meaning of symbols they exchange -- defining things is the first step in such an agreement.

    Well, I think you are making this way more complicated than it should be. But it looks to be a fun game, so let's try to make up some definitions.

    Here's a simple and basic one:

    "Sailing is a method of vehicle propulsion which utilizes sails as the main method of converting wind to vehicle movement".

    Note that I said "wind". Movement on the boundaries of liquid and solid medias, etc. etc. should have a different name. If you take, say, a land yacht and put it on the bottom of a river, it should be able to move utilizing the river current as power for its sails (we'll assume suitable river bottom, suitable sails, etc.). I, however, don't consider that to be sailing and don't see much point in trying to stretch the definition of sailing to cover this.

    Now we've made some progress, but to a certain degree we just passed the buck -- we now need a definition for the word "sail". That is a more fuzzy area. A possible narrow definition will distinguish between sails and rigid wings and say something like "A sail is a sheet of flexible material that relies on pressure differential on its two sides to provide thrust". Under this definition rigid wing sails aren't really sails -- they are just wings put on their side.

    Maybe this is too narrow (although it would make lots of sense to a non-technical audience), so let's include rigid wing sails by discarding the flexibility requirement. That means, however, that we also need to think about excluding windmill-type arrangements. One way of doing this would be to specify that "true" sails must be able provide thrust statically in a local time frame. I am not sure how to phrase it more elegantly, but it means that if you freeze the sail in time it will still provide thrust, while a windmill would not -- it needs to rotate to do something useful.

    Here however, we are entering the lands of angels dancing on pin heads. It can be an agreeable form of mental ************, but if you want something actually USEFUL to come out of the exercise, we should have already specified a clear purpose and context to a definition a few paragraphs before :)

    Kaa
     
  6. Kiteship
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    Kiteship Senior Member

    What you offer--and many others as well--is a description of something you observe. I see a creature with wings, moving through the air. I shall call it "bird" and define it as a creature with wings, which moves through the air. These are not definitions, they are descriptions. A definition for "bird" would include its taxonomy, its anatomy, likely a history of its evolution. It might address the aerodynamic capabilities of the creature's wings, bones and musculature; and the fact that it's primary mode of flight is flapping, not fixed wings. Curiously, the actual definition of "bird" does not require flight, as we all know. If I used your method for defining "bird" surely no penguin, or emu would be a "bird."

    Dave
     
  7. rayk
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    rayk Senior Member

    Flightless birds
     
  8. Kaa
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    Kaa Wanderer

    Funny, I would say that "its taxonomy, its anatomy, likely a history of its evolution" belong to an extended description, but certainly not to a definition.

    Let's try it from another angle. The function of a definition is to create a boundary -- to separate something from something-else. We want to define what a bird is in order to separate birds from mammals, reptiles, etc.

    What are things (concepts) that you want to delineate sailing from?

    For example, we want to separate sailing from drifting. A lot of things move because they are pushed by the wind or the current but we won't call it sailing. We want to separate sailing from poweboating even in cases where the boat mounts a wind generator and ultimately uses the wind energy for moving.

    Between sailing and what else do you want to draw a clear boundary?

    Kaa
     
  9. Kiteship
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    Kiteship Senior Member

    OK, this is a useful direction; let's have a look. First, it's not what *I* want; a definition doesn't exist to suit a single person's wishes. We don't define "bird" just to suit Mr Audubon's sensitivities.

    Boundaries are good. For instance, a definition for "sailing" ought to separate drifting versus sailing, as you suggest. It ought to separate sailing from "wind powered vehicles," for instance (a wind turbine, afloat or ashore, charging batteries later used to power a runabout is a "wind powered vehicle". It is not a sailboat. Ask yourself why?)

    Without a concept of stored energy--and a disallowance of same in "sailing" you wouldn't be able to delineate the two (I've talked about this earlier int he thread)

    Problem here is we come back to descriptions. If I tell you I think sailing ought to discriminate between stored energy and non-stored energy, you can simply add it to your description, and we're only a tiny step closer to a definition (and that's presuming you actually agree that stored energy isn't "sailing" Some canting keel guys might disagree...) Definitions should be simple; "lift" is a force perpendicular to the flow of a fluid medium; "tangent" is the ratio of two sides of a triangle, etc.

    "The exchange of momentum between two media and a vehicular device for the purpose of directed travel" might work. I started this thread, and didn't want to be presumptuous--and I didn't want to "defend" my own definition, since, after all, I hardly have the authority. There's been a lot of great input so far; I'll try to boil it down to a short description, and maybe we can pick at that.

    Dave
     
  10. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Someone should perhaps ask the OP to fess up as to WHY he started this thread..... THat will give us all some idea of where he is going.
    The fact that his handle is "Kiteship" might give some indication that he is seeking approval for calling a kite-powered ship a "sailing" ship - or not.
    So, Kite, what is it?
    I don't think for one minute that anyone is going to argue with a kite-powered boat being a sailing boat, but you never know. Insurance companies might argue it, coz they are as wierd as lawyers (apologies to any insurance folks in here) and need to create smaller pigeon-holes to exclude people from.
    Personally, if it doesn't use a stored energy device for propulsion, then it must be a sailing boat/craft/ship, no?
    And I do not exclude such things as canting-keel boats with engine-driven systems, because they CAN sail without the ebngine, just not as fast, and because the keel-canting mechanism on its own will not move the boat
     
  11. Kiteship
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    Kiteship Senior Member

    Thought I'd been clear about that. No, I don't need validation regarding kites and ships--I'm OK with that (though I have in fact been told that kite sailing isn't "sailing!" I considered the source and took no offense... ;-) My signature is my business; see www.kiteship.com

    I'm an amateur scientist (or heck, maybe I'm a pro--I get paid to do what I do), and like a lot of scientists, I find enjoyment in turning things over and taking them apart. I'm a long standing member of the Amateur Yacht Research Society, am in fact, running a parallel thread there right now. I take things apart so that I can develop a better understanding of the things around me, the better to design or discover new ways of putting things together, discover new things, and develop new insights about things I already "know" are true. (the cliche about "The older I get the less I am sure of" is absolutely true!) I've already unlearned several mis-truths since this thread started; I expect there'll be more.

    (Just for the record, I've been sailing since I was little--maybe 40 years now. I sold my first design nearly 30 years ago; have been a pro boatbuilder, pro fisherman (offshore albacore jig boat), mechanic, designer, sailor and general layabout. Plus the usual carpenter, electrician, husband and father that fills the time for us all. I like kites, and other "unusual" approaches to sailing. I have a couple of patents in the field, and run a company trying to put kites onto ships. Mostly, I'm just curious. Drives the wife nuts--and some here, it seems.)

    Thanks for your "wide" POV regarding sailing, SD, but even there you display the limits of your own sailing "box." Why d'you presume I'm only interested in sailing which involves wind over water? That's only one of at least 6 sailing contexts. The others are at least as fascinating--and as full of surprise traps, contradictions and opportunities, as the one we make our living with.

    (And no, dammit, canters are *not* sailboats. Darn cheaters! Oh, sorry, was I being shrill there? ;-)

    Dave

     
  12. longliner45
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    longliner45 Senior Member

    ok I read your site ,,looks really cool ,you shold sell alot of them now that fuel prices are high ,,,I may get on for my boat ,,,,but as for sailing ,,you must be in controll of your vessal ,,free to go here and there ,,and against the wind,,,I can see it now,,500 ft of sail plus a spinniker ,,and the mother of all kites heading south on the trades,,,,,how much do these cost? longliner
     
  13. Kaa
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    Kaa Wanderer

    Well, first, definitions can be useful to suit a single person and second, again, you haven't defined a conversation in which such a definition will be useful. I've talked about it a bit in a post above.

    See, I think of definitions as being rather arbitrary. The fabric of reality is certainly not even and uniform, but overlaying mind-created concepts on top of it can be done in many different ways and the boundaries you draw are not necessarily well-defined.

    People who come from math, or physics, or engineering backgrounds are usually uncomfortable with this fuzziness and arbitrariness. They tend to believe in objective "Truth" and in the existence of "correct" definitions. People who come from the humanities are, generally speaking, more cognizant of the fluid and uncertain character of maps that human mind uses to understand reality.

    It seems to me that you are trying to get a physics-like definition for sailing and are unwilling to come to grips with the idea that the concept of sailing is broad, ambiguous, and likely means different things for different people. I continue to think that you can't produce a universal definition of sailing that will be equally useful anywhere. You need to specify a purpose and a context.

    Consider a boat that has a windmill mechanically coupled to a propeller or a paddle-wheel. No energy is being stored. Is it sailing?

    Definition is a subtype of description. And simple definitions work only for simple concepts. By Occam's Razor we would *prefer* a definition to be simple, but a useful long definition is better than a short, but useless one.

    "You should make it as simple as possible, but not simpler" :)

    Kaa
     

  14. MalSmith
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    MalSmith Ignorant boat designer

    Consider the case of a Flettnet rotor, which is vertical cylinder that is rotated by some mechanical means. The Flettner rotor develops lift due to the magnus effect. Otherwise it behaves as and is used if it were a conventional sail. A Flettner rotor ship must be tacked into the wind like any other sailing vessel, and I think that most poeple would accept that the method of operation of a Flettner rotor ship is called sailing. Hence the need for the definition of a "sail" to be fairly broad.

    Considering windmills, things get a bit nmore complicated. The blades of a traditional windmill are called sails. Under the terms of the broad definition for a sail that I have proposed previously, they are indeed sails. However, I don't think anyone would call the operation of a windmill "sailing". If you attach a windmill to a boat and mechanically link it to a propeller, are you "sailing" the windmill boat or not? Conventional fixed sail boats and a windmill boats are actually very similar. Both couple aerofoils to hyrofoils in order to be able to move in any direction including straight into the wind. The difference is that a windmill boat is a rotational device and a fixed sail boat is a linear device. Because the fixed sail boat is a linear device, the whole device must be moved in zig zag pattern (tacking) in order to advance straight into the wind. On windmill boat, the hull can advance satight into the wind because the sails and foils can be moved independently of the hull. Personally I consider a windmill boat to be a sailing vehicle. If you don't however, then the difference comes down to the fact that the fixed sail device must be tacked into the wind.

    Mal.
     
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