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Most sailing boats already have underwater sails - they are called keels and rudders. |
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no. not a keel or rudder. I'm talking about full scale
sails using large underwater (foldable so when near
coast you let them in) masts, and sails made in the
exact same form as wind sails, only underwater and
using the sea currents. |
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Perhaps because we are "sinking" the sails, a type of
"underwater kite" (upside down parafoil / paraplane)
could be used, and then no masts
would be needed. |
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"Sea Anchors" are just this, and Widely Known To Exist. |
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//the exact same form as wind sails, only underwater and using the sea currents// |
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We have discussed this here before. Wind sails only work by having something fixed in the sea or land to pull against. Sails on a hot air balloon would hang limply. |
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We're skirting "Air Yacht" again, aren't we. |
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[pocmloc] I'm not sure the balloon-sails analogy holds,
because in this case, the boat encounters resistance from
the air-water interface (which has no analog in the
balloon case). That counts as something (relatively)
fixed. Try this argument on for size, & see if it
makes any sense: |
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Wind will ruffle the water-surface into waves, such that, in
order to move forward, the boat must rise (gain
gravitational potential energy). The underwater sails will
push against this effect. Then, as the boat descends into
the trough of the wave, the wave-height effect will push
against the underwater sail. By varying the pitch (?) of the
underwater sails (I picture some sort of louver
arrangement) in phase with the waves, such that
resistance offered by the sails to the surrounding water is
greater when climbing a wave than when
descending one, it should be
possible to move the boat faster than it would move
without the sails. Slightly. |
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Now, since the wave-height effect is *directional* and not,
in general, the same direction as the current, it might
even be possible to *tack* with this arrangement.
Sluggishly. |
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No, sorry, no sense. The boats I have sailed on have been longer than, or comparable length to, the wavelengths. So they roll and pitch much more than bob up and down. |
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Also I don't see the air-water interface as in any way “fixed”. |
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Sure, but that just means you don't go sailing in
conditions too rough for the size of your boat. Wavelength
of wind-generated waves can be over a thousand meters.
But point taken: I suppose the climbing up a wave and then
sliding down into the trough business probably only happens
in storms. |
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I'll vote for this until someone tries it and says it can't be done.
There are currents. |
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A submerged digital camera would see what, exactly? The water going by? Or what the sails are doing, maybe? If so, why a camera and not strain gauges? The water gets murky, mind. |
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And a current indicator is what? A log line, perhaps? |
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This idea is one that pisses me off because it is so hopelessly vague that people gloss over the impossibilities and start believing in it like a religion. As a former sailor, both on ships and sailboats, and as a person who often poles a canoe upstream against river currents, I am going to try to point out what is wrong. |
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As was said above, sailboats already have underwater surfaces called keels, wing keels and even canting keels. If there was anything to be gained from underwater currents, the potential for progression from current technology has been wide open for hundreds of years. The fact that nobody is doing this is good indication that it will not fly. |
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Currents, out in the deep ocean, move at one or two knots, and are usually wide, unidirectional and rare. Using a current is hardly worth doing, and where it is worth doing, one simply sails a regular boat along in the current, or, if wanting to go any other way, avoids the damned thing. |
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For a sail-type boat to use a water current as anything other than something to float along with, it would have to have something outside of the current to push against. Sailboats use the wind that is out of the water, and a keel of some sort (leeboard, centerboard et c.) in the water. There may be a current in the water, but the wind is so much better that water currents can be ignored, largely, except when they present a danger. |
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To sail the water currents would require something that can reach two different water currents, and the only time I have ever been in a situation like that is when my canoe gets crossways in a river and is preparing to tip me out. Tide races in a channel are vaguely similar, and are to be avoided. The only times a sail under a boat would do any good would be in water shallow enough to rip the rig off. |
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And even then you'd need two sails with a distance between them, not just one sail sticking down, and a damned lively crew to manage them. |
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[Mouseposture]'s idea of using wave-action to push a boat is not, repeat not, the idea as posted, but could be made to work with some floats, levers and foils. It is, however, wave-surfing, practically speaking, and again, not the posted idea. |
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The posted idea is most probably based on a common misunderstanding or two. As was said, sails need something to push against, and ocean currents are too wide for any practical vessel to take advantage of. |
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You either need two different currents, or one current and a fixed object to get some relative motion. Sailboats use the air current, wind, and treat the water as a fixed object most of the time. |
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[baconbrain] My proposal may well be dead wrong, but one
thing it's not is an entirely separate idea: rather, it's a
modification to [pashute]'s, an attempt to show it's not
outright impossible. |
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I thought one might use waves *to provide something for
the sails to push against* (i.e. in the role of a keel, or
centerboard which as pretty much everybody here has
pointed out, is a necessary complement to a sail.) In
ordinary surfing, sliding down a wave provides motive
force. I was proposing that the underwater sail provide
the motive force, and sliding *up* a wave *provide
resistance* permitting the vessel to tack at an angle to the
current. Very weak effect, probably. |
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However, I see where the confusion arose, and, in fact, my
own thinking was unclear: For the other half of every
wave-cycle, the boat would be surfing in the ordinary
sense, with motive force provided by sliding down the
wave, and resistance provided by the underwater sail
(acting, in that phase as a keel). |
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The boat would proceed on very short tacks, changing
direction with every wave cycle. Very unpleasant motion
for the crew I imagine. |
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[mouseposture]'s idea was baked some time in the late 80s. It was a small boat, with a horizontal foil underneath, pivoted near its leading edge. As the boat rises and falls, the foil flip-flops, propelling the boat forward a little like a whale's flukes. I don't think it was fast, but it worked. |
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[mouseposture]'s idea has nothing to do with *using* the underwater currents. It would use *waves*. Underwater foils spread horizontally, bobbing up and down, might let a boat move through the water, but that isn't *using* a current. |
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This is what I meant earlier. The idea is so vague, and based on some common mis-assumptions, so that people are bringing in more odd concepts. While the sailors and boat-builders like me are trying to explain purple to blind people. |
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Practically speaking, there are no currents in the ocean. The Gulf Stream is so big and slow that you can't tell you are in it, and a tide rip is a killer to stay away from. There is no current in the ocean, and you can't use underwater sails in a river. |
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If there were currents, you'd need two sails, one in each current, to do anything but drift like a barge. The idea supplies nothing toward that, it just says to put a sail under the water. |
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Look, there are some deep and slow ocean currents--you could drop a weighted board down into one, on the end of a line, and fly that board like a kite, towing your boat at a whopping knot or two. But the kite would fly out of the current in a while. So you could just drop a parachute-like thing into the current and follow it wherever it went. But you'd need a lot of line, not just a sail sticking down, like in the idea. |
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By the way, when you are in the marine supply store, getting the line, you could actually buy a weighted board that flies like a kite--it's called an otter board. You could also buy a parachute-like thing to drag in the water--it's called a sea anchor. |
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You can, at a surface boundary between two currents, work a boat to get a bit of oomph by shifting in and out of one current into the other, along the edge. It's called an eddy turn. But you couldn't go anywhere that either current wasn't already going, and you only find eddies like that near rocks in fast rivers. |
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Again: If this idea was possible, people would be doing it. Thousands of years, millions of sailors, high-technology transportation and barking-mad inventors have been messing about in boats. The technology exists, the concepts are familiar, the terms are common. It just isn't practical, even using my suggestions, and is completely impossible using the posted idea. It isn't that the creativity is lacking--there are some fuddy-duddies out there, but there are also people sailing boats they made out of cement. |
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Please, oh please do not say that you are very unlikely to come up with something new in boats, and especially not new and useful. |
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I've been told this about a few other ideas of
mine... and then they turned out not only to work
but even to have been baked. (Not referring to
recent one from today, I'm waiting to hear what
the responses to that are). |
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The main problem with the idea is that you claim
that currents are the same at all levels of the sea. |
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In the air, (for ballooning for example) it is well
known that you can catch drifts in all four
directions on a regular non stormy day. |
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Pocm did you ever do ballooning, or hang-gliding?
Experience shows that a kite flies quite nicely
from a balloon, and so a para-foil even in the same
wind you are in could add a nice boost. Balloons
tend to go pretty slowly, compared to the wind. |
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I do not have much boating experience, but do
have swimming experience at the beach (and
perhaps that's what makes all the difference).
There are undercurrents going sideways, and top
currents sometimes going in opposing directions.
There are definitely different speeds at different
hights. Is this not so? |
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BTW bacon, did you ever invent anything? |
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[2fries], you are very unlikely to come up with anything new in the world of anything, especially not new and useful, because people have been doing things for a very long time now. |
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We all are familiar with innovation in one field leading to new inventions in other fields with the faintest of relations. We need people constantly reassessing the overall landscape of materials and inventions, lest a potter's wheel never becomes a chariot. |
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[pashute], I have no patents of my own to refer you to, but I could give you about eleven of my dad's. I have described my qualifications as regards boating, and can add that I have won a few kinetic sculpture races, and used to hang out at the Center for Wooden Boats in Seattle, where I rowed and sailed on my days off from my job of building sea kayaks. But that's all online fluffery, for all you know. |
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Which is why I described what is wrong with the idea as posted, and explained how it could almost be made to work through radical modification. If you cannot understand what I have already written, there's not much I can do but huff off, muttering obscenities. |
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There are many people who imagine that a balloon could be fitted with sails and maneuvered around the sky. That cannot be done, although, as you say, there are layers of currents in the sky and a kite rig would sort of work (although nobody is doing it). |
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I know about wind layers quite well, thank you. I have watched a solar balloon that I launched from Seattle's Gasworks Park go up to the east, course madly across to the west, then sink and drift eastward almost back to me. I have even flown a kite up out of Jones Beach off New York City, tied a cluster of balloons as a drag to the line and watched it go up and away. |
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But the posted idea does not mention lines and kites, it mentions sails, which are traditionally on masts, and a camera, which implies short-range viewing. I do not say that an underwater traction-kiting arrangement wouldn't work, I even suggest it, but point out that it would be very slow. The technology .... |
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// go up to the east, course madly across to the west, then sink and drift eastward almost back to me // |
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Our extensive (VERY extensive) experience with Fire Balloons, pyrotechnics suspended from free-flying Helium balloons, and (even better) pyrotechnics suspended from free-flying Hydrogen balloons entirely confirms what you say. |
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The thing with the pyrotechnics suspended from free-flying Hydrogen balloons coming almost back to the launch point is a bit disconcerting, to say the least. Important tip - keep an air rifle handy. |
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Dang that sounds like fun. |
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Is it just me or is it getting harder to find info in the first few hits on this inter-thingy? |
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I'm pretty sure I that read that the first successful circum-global balloon flight used a large kite-type fore-sail, but i can't find it anywhere. |
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//you are very unlikely to come up with anything new in the world of anything, especially not new and useful, because people have been doing things for a very long time now.// |
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Aw jeez, now you done it.
//world of 'anything'//... really?
anything... |
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brain... first, thanks for pointing those points out
in extra clarity. You are correct that when I posted
the idea I was unaware of the info from [poc] ("we
have discussed this here before...". The question,
as you see from other's remarks, is what the
attitude of your answer is. If it is "yeah we
thought of this already. Won't work" then you are
just discouraging. If it is: "Sorry to say, but this
has been baked" like spider and mouse, or even if
you had only left at the "This idea is one that
pisses me off because it is so hopelessly vague
that people gloss over the impossibilities and start
believing in it..." with your explanation but
without the " If there was anything to be gained
from underwater currents, the potential for
progression from current technology has been
wide open for hundreds of years. The fact that
nobody is doing this is good indication that it will
not fly." - then your anno would be constructive. |
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I added an [Edited] section to the idea, about
these points.
section with continuation. |
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