Definition of Sailing?

Gravity or potential energy is not required for Dynamic Soaring (DS). An RC glider DS'ing at 300 mph is pulling something like 50g turns, so gravity is only 2% of the overall forces involved.

What is required is sufficient inertia, or more precisely, a sufficiently large L/D or ballistic coefficient. This allows maintaining most of the kinetic energy in between the periodic kicks provided by the shear layer crossings. If most of the kinetic energy were to bleed off between kicks, the DS cycle could not be sustained.

 

definition of sailing

Perhaps starting with the definition of definition= "a statement expressing the essential nature of something". This is going away from describing the essential nature of sailing; it is delving into area's similar to sailing but not sailing-in my humble opinion.
I still like:
"Non-random movement as a direct result of wind pressure"

 

What about a surface vehicle equiped with a wing that provides propulsive force in the form of lift... from the wind... contrary to ....that can be propelled in any direction... contrary to the...
Sailing must be a human deflecting a moving mass...argggh wind wind dammit!
Its a guy on a boat who can make it go in any direction (usually somewhere safe to anchor with a good pub on the waterfront) just by putting a sail up. No. To simple.
Anyway I there must be a martyr/victim/fool/person rolled into this definition somehow. Or sailing will end up like NASA,where the tecchies moan about wasting money on live meat space exploration. Everyone knows no one is gonna live on Mars. Who wants to live on the moon, it must be easier but theres no point.
Where was I?

:idea:
Sailing is done on the sea in a boat with a sail. Anyone else using the word without these ingredients is just ripping off the word. And then having the cheek to say sailing needs a clearer definition!
Whoever invented ice yachts or solar sailing could have extended their genius to inventing a new word I think.
Sailing is an old definition not a broad one. And it doesnt need to get jazzed up and modern.

 

Maybe you should look up the word "essential" Doug

 

definition of sailing

Sure DG:

essential=
1) of ,relating to ,or constituting essence,
2) of the utmost importance: basic,indispensable,
necessary
------
You know- like "wind pressure" and "non-random"- in any realistic, practical, usable definition of sailing....

 

Wow! Is it just me or does the word essence seem to imply something more than "a dude on a boat on an ocean" explaination?

And I see you are getting mighty commanding with those words "realistic" and "practical" and my particular fave..."usable"

Even if we are over defining it...what is it about the fun of trying that bothers you so much?

 

definition of sailing

I'm not bothered in the least but having to explain this(or something like it) to some kid at Kelly Park on the weekend could be bothersome:
"Now, looky here kid, sailing is utilizing a decoupled flow at an interface of two fluids or a fluid and a solid, to advance a vehicle through or over one of two said media-now get out there and show us what you've learned!"
DG, you said:" Geez, this is getting ridiulous"
and I'm just agreeing with you.....

 

this is clear cut forexample

but the definition stretches couse you agree a motorboat also sails ya?
can we say a keel does? think so, think we can even say a prop does.
dont realy know if we can say an electron "sails" around hydrogen though

 

I see your point. But without that potential energy we could not have travel in the direction of the wind source. So we come back to Daves question...is that the defining criteria. how much freedom do you need in your choice of movement before you can call it sailing.
It brings to mind those characters that crossed the Atlantic from New York on a floating pile of rubbish that had a blue tarp sticking out the top. They definitely had drifting confused with sailing.

 

Doug
You say you are not bothered..but you seem very bothered.

My comments about getting ridiculous are called "having fun"...can you say "fun" ...I'll betcha' can!?

 

A boat would have to make ground against the wind I think. Thats what makes sailing so cool. You can make ground using the very thing thats trying to blow you away.
It is like trying to use gravity to climb up a wall.

 

Hmmm, and I presume you can also stipulate that both media move only parallel to each other--that is, parallel to the ground (no thermal lift)? I'd always more or less dismissed slope soaring, believing it relied on thermals/non-parallel interface in order to work. Thanks for the references.

Let's take this a bit farther afield, then and see where it takes us (I'm hijacking my own thread here, but I really want to know what Mark thinks). If all that's required is an energetic momentum differential between the media and sufficient inertia in the vehicle, well then, couldn't we use the interface--the vertical interface--between the jet stream and still air? Has anyone tried this? I can see potential inertia issues (the interface between media may be too large to carry inertia across), but wouldn't this perhaps, allow very fast, heavy devices to "sail" hither and yon? We are already experimenting with kites-flown-from-blimps as air/air sailcraft.

Or, staying with the water/wind interface (I love the old sobriquet, "Ancient Interface"), couldn't one build a "flying fish," capable of diving into water, wings folded, then swooping back into the air, spreading wings, then diving back into water to repeat the Dynamic Soaring cycle? I'm not just supposing here; the US Navy is spending significant money on extremely long range robotic reconnaissance these days. Here's a potentially very efficient "sailing" craft, which could be very, very fast as well.

Thanks for checking in, Mr. Ludd. Problem is, you bring us back to the original issue; what is the definition of sailing? If it's just your old gaff schooner on a New England Fall afternoon, what, pray tell, are those guys doing on the Wisconsin ice? They are using the identical same physics you are using, and having the identical results you are. But your name is already taken, so maybe they're "ice-wind sliding" eh? C'mon, come into the 20th century (we'll work on the 21st later). Point is, a definition both describes--and limits--that thing it defines. Do you really believe ice sailing is not sailing?

Cheers,

Dave

 

Ludd here.
Ice wind sliding... ice-wind sliding... ice wind-sliding...
Im tempted.
But after checking in the A-K volume of my encyclopedia set, Ice sailing seems a legitimate use and would appear to share something in common with sailing.
But I stand firm on solar sailing! The technology isnt even available yet. Rename it. I have my ways. To discuss this matter in private visit me aboard the good ship Spinning Jenny.

 

In order to provide a broad enough definition of sailing to encompass gliders and solar yachts, yet specific enough to eliminate devices with multiple energy conversions it is probably necessary to break the definition into parts. I would propose a definition something like this:

Sail: A plate like device which derives a force directly from a moving fluid by creating a pressure differential in the moving fluid either side of the device.

Sailing: The operation of a sailing vehicle.

Sailing vehicle: A payload carrying device which obtains directed motion by deriving a motive force from the vector sum of at least two other forces, at least one of which is obtained by using a sail.

Note that by this definition a Hydrofoil is a sail like device specifically designed for use in water, and an Aerofoil is a sail like device specifically designed for use in air.

Mal.

 

LOL. A funny thread.

Definitions are important, yes. But definitions don't exist in a vacuum, a good definition is one that serves a specific PURPOSE. For complex subjects it's possible to give several -- nay, several dozens -- definitions which will all be correct in the specific framework where the definition is used. These multiple definitions don't even need to agree with each other as long as it's clear to which context a definition belongs and as long as it's USEFUL in such a context.

Define us a context, a purpose for a definition of "sailing" and the task of formulating said definition will become much, much easier.

Kaa