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I found this too difficult to draw. I hope it translates well enough through words.
This watercraft would be a catamaran with a lowered main hull which would contact the surface of the water while in larger waves.
The re-enforced roof of this boat would be a flattened teardrop shaped water tank
tapering toward the aft.
This tank will be longitudinally baffled to keep water from sloshing side to side but can slosh freely fore and aft.
A single curved inner lateral baffle running along the upper ceiling of the tank angled toward the outlet keeps water from being able to slosh back through the intakes.
The forward struts connecting the hull to the pontoons are curved, hollow, and tapered to allow water to be pumped either manually using solar/wind energy, or with every plunge into an oncoming trough by water pressure through the narrowing inlets to the upper collection chamber/roof. The forward main hull would also contain a scoop for greater collection in rougher seas.
The rear struts, curved backwards, are also tapered and hollow allowing descending water from the upper tank to exit under individual control and pressure for maneuverability.
The fore and aft sloshing then becomes important as water pressure rear-ward will cease after cresting and descending a wave.
When the forward scoops meet the wave trough the incoming water will then be shunted over the collected water to exit through the narrowing outlets just when a ship needs the most power to cut through an oncoming wave.
Water unable to escape during this phase will be forced into the main collection chamber by gravity alone.
In this way the waves themselves could power a vessel using simple geometry of hull design.
I also wonder if vortices created by an intake diameter insufficient to accommodate the entire volume of water wanting to enter would have less resistance than a streamlined forward hull.
SpiderBoat, SpiderBoat...
http://www.google.c...RT-7tBOq0iQKz1LjhDQ
...doin whatever a spiderboat does [2 fries shy of a happy meal, Jan 14 2012]
Hydraulic Ram
http://en.wikipedia.../wiki/Hydraulic_ram
Supplying perpetual motion since 14 billion B.C. [methinksnot, Jan 17 2012]
Bad sketch.
http://s68.photobuc...rent=scan0001-2.jpg
[2 fries shy of a happy meal, Jan 19 2012]
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If I understand this correctly, water jets created backward due to sloshing of water inside the upper tank will propell the ship forward ?..Just like jet-skis. |
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"a catamaran with a lowered main hull" --so, 3 hulls? and the one in the middle is the lowest of the three? |
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Lowered main hull will introduce noticeble drag. |
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Is this dependent on wavelength? |
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With that huge tank of water mounted so high above the
waterline, this craft would require so much ballast below
the waterline as to be virtually un-steerable. |
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Someone made a wave powered boat back in the '80s that had a flip-flop foil underneath: |
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but this idea, if I understand correctly, has no moving parts - at least in the pumpless version. |
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[Alterother] It would get roll stability from its multiple hull design (leaving aside the oxymoron of a catamaran with a main hull), and probably _should_ have low pitch stability, to maximise sloshing. |
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Whoa. Ok, Yes the water leaving the tank under pressure from the taper would propell the craft but the sloshing only comes into play in rough weather.
Also the main hull would not touch water except in bad weather, say eight to ten foot swells. Sort of a less ungainly SpiderBoat [link]
It shouldn't be dependant on wavelength as the size of the waves self regulate the size of the slosh.
Ballast should not be a problem if both the tank and the hulls' footprint are spread out enough. This is why I thought a catamaran shape would be best... or maybe even a quadmaran.
I came across that wave powered boat when I did my search. It was one of those, <smacks forehead> I should have thought of that, moments. |
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It's a no-moving parts propullsion system using waves to refill the tank, and when I played through in my head how it would handle in rough weather it became clear that the sloshing could be used to advantage. |
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And in perfectly calm water? |
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With a very wide-stance 2- or 3-hull configuration, I can
see it being stable enough. But why not put the resevoir in
the hull? |
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In perfectly calm water a full tank would go for quite some time and may produce enough speed to use a hydrofoil for increased distance. If the induced foreward vortices do decrease drag like the dimples on a golf ball then it might be possible to recoup much of the lost water without sacrificing headway.
Manual pumping would be required after that using solar or wind energy. |
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Having a reservoir in the hull rather than up top would be less effective because the water would fall from a lesser height and the tapers on the struts would be more pronounced.
The counter oscillations from the slosh factor would also be mitigated. Why damp them when you can use them? |
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hmmm tethered magnets surging back and forth through windings within the tank would also produce electrical power. |
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mitigated, that's my word of the day |
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Thats water falling from height of 3-4 meters ; I doubt if the thrust from water jet would be sufficient. |
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Even if it were, the thing would still be a bloody bitch to
steer. I can tell you from much experience that boats
shipping large amounts of water do not turn dimely. |
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It's not just water falling from 3-4 meters, it's a large volume of water wanting to fall from 3-4 meters and being restricted from doing so. |
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Large ships should not need to turn dimely, (nice adjective btw), there is no reason that exhaust nozzles couldn't swivel allowing one to point point ahead while the other vented behind for dimeliness of turnitude while maneuvering close to port. |
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I'm pretty sure that it'll work. I could probably make a mock-up from plastic pop bottles. |
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This idea reminds me why editorial staff is used by scientific
news. |
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//This idea reminds me why editorial staff is used by scientific news. // |
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To spread the blame around ? |
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"So we're all agreed then... a car that goes 280 miles on battery power then 20 miles on its range extender using a gallon of gas gets 300mpg." |
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Only height determines pressure, Nothing else, not even volume. It could be ocean size tank or glassfull water, it would fall at same pressure through nozzle. I think this is a physics issue. |
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Interesting point. I think you're wrong. Physicists? |
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//Only height determines pressure, Nothing else, not even volume.// |
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Really? So if I hold my hands over two identical tapered hoses that lead to two identical 10,000 liter tanks but one is full and one contains only 50 liters, both hands will hold back the water equally?
I'm not sure I understand the problem. |
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Subtracting all of the wave catching/slosh factor/baffles and such, just a suspended tank full of water released under pressure from a tapered hose would push a catamaran in calm water until most of the water ran out, yes? |
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The only physics problem I can see is if the design would be able to keep that tank full while in waves using shape alone... and if I'm right about using counter oscillations to help *scoot* through the waves the way using ripples of your body will scoot a bell-hop's cart through a lobby without moving your feet. |
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Another aspect occurred to me. If the intakes were valved then every gulp of water would also pressurize whatever air is in the tank for a little extra thrust. |
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//So if I hold my hands over two identical tapered hoses that lead to two identical 10,000 liter tanks but one is full and one contains only 50 liters, both hands will hold back the water equally?// |
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Yes, provided height of both tanks is same; (obviously other two dimentions, length and breadth of 10,000 liter tank will hve to be much larger). The length and bredth of larger tank is irrelevant. |
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Others on HB are welcome to chip in. |
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Wait a minute, it's not the height of the tank that matters, it's the difference in height between the free water surface and the point where pressure is measured. So the tank with 50 litres will certainly show a lower pressure, if the tanks are identical - because the free water surface will be lower. |
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A tank with a 1 m² footprint containing 10,000 litres and a (skinny, pipe-like) tank with a 0.005 m² footprint containing 50 litres will both have the same water height of 10 m, and the same pressure at the bottom, 1 bar greater than atmospheric at STP. |
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However, height only provides a pressure differential, not an absolute pressure. Other things contribute to the pressure - otherwise water pistols and propellers wouldn't work. |
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Sloshing, in particular, can produce pressure greater than that given by height alone. This can be demonstrated with a narrow-necked bottle half filled with water. |
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//It's not just water falling from 3-4 meters, it's a large volume of water wanting to fall from 3-4 meters and being restricted from doing so.//
The discussion relates to this sentence by [2Fries]. |
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I know; and a head of 3-4 metres limits the nozzle velocity to 6.64 - 8.85 m/s, all things being equal, regardless of the size of the tank. Sloshing could add to that somewhat, by a hydraulic ram effect. |
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On the other hand, that range of velocities is quite respectable; you won't win any speed records, but it'll get you where you're going. Rate of flow is the fissing* variable if thrust is to be calculated. |
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I did a sink test of this principle, and it works just fine. (Not the wave-powered scooping part, just propulsion using a jet of water from a tank using gravity alone). Apparatus: a small yoghurt container with a hole near the bottom, filled with water, placed on a catamaran made from a slab of polystyrene across two rectangular takeaway containers. |
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*Fissing variable, or splitting variable, a quantity that determines whether a result will go one way or the other, in this case, practical or not. Definitely not a fisstype. |
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Now I'm thoroughly confused. |
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So, it 'will' work in real life the way it works in my head, but, only 'because' I am mistaken about the basic physics principles involved? |
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I think I'll have that second cup of coffee now please... |
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[2 fries], If one is diving in a sea, water pressure increases with the depth. Size of the sea is irrelevant. It could be a ocean, sea, lake, pond or a pipe hung vertically; It does not matter. |
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So IMO, thrust will be negligleble; To add to that weight of the large water tank will slow things further. |
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[-2fries] - re the pressure / height / volume thing, search on "hydrostatic paradox". It's called a paradox because - well, you're not the first to whom it looks weird. |
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It will move allright, just very slowly. [Spidermom] just prototyped it so: BAKED!
[Spidermom], [Spidermom] doin' whatever [Spidermom] does. |
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Hang on, I just prototyped the bit where the water exits a tank in a jet, and provides thrust. |
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I still don't quite understand the purpose of the ascending and descending hollow struts. If you're thinking that it will be easy to get water up into the tank, because the "whole ocean" (or at least a great big wave) is pushing on a thin and light bit of water, and conversely, that it will exit powerfully because a great big tank-full of water is pushing on another thin, light bit then you're mistaken, as that would imply the potential for perpetual motion; that might be what the others are objecting about. |
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On the other hand, it's plausible that the kinetic energy of the wave could be converted into pressure, then back into kinetic energy of a smaller, faster-moving flow, thus allowing water to reach a height in the vessel greater than that of the waves themselves. While that sounds convoluted, it's a real effect, and is how wave-driven blow holes work. |
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Yes, I got that part to work. I knew it would, but I like to check that I'm not completely crazy. |
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Take a funnel, narrow end up-most. Plunge it vertically into water, in a fairly controlled manner, right up to the neck. If you get it right, the rising water within the funnel kind of splats into the constriction at the base of the neck, and some water spurts out the top, to a height of a foot or so above the main water level. The effect should work just the same regardless of whether the water, or the funnel, of both are moving. |
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So your boat does have potential to work much as you describe it - as long as it is understood that it's not just about pressure, but rather a kinetic, or sloshing, or hydraulic ram effect that squirts the water up into the tank, and similar sloshing is the only potential advantage of a large reserve of water in the upper tank. |
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([SM]: Exits to lemon tree) |
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The principle is well known - Hydraulic Ram (linky dink). But the energy has to come from the waves, not the movement of the craft (otherwise something very terrible might happen). |
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<Zim> My business ... Is done! </Zim> |
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I mentioned the term 'hydraulic ram' up there ^, but wanted to confirm the specific instance of a tapered tube interacting with a free body of water (rather than, say, the sudden interruption of flow through a pipe.) It's also just nice to be able to model these things physically, for piece of mind and ease of understanding. |
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And yes, the energy has to come from the waves; whether it's the waves slamming into the ship, or the pitching ship slamming into the waves, is immaterial though. |
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I should add that although I think this will work, it will be a rather weak effect, as the directed thrust due to the jet will be small compared to the forces of interaction with the waves. |
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Also, we are discussing two means of getting water into the tank - the ram effect, and the irrigable bow syndrome (the rough-weather scoop). These might be better kept separate, rather than filling the tank in parallel as described. This is because the water in the ram tubes is already moving quickly, and might as well be jetted directly out the back, rather than needlessly and wastefully being stored as potential energy in the tank, whereas the scooped water inherently needs to go through a gravitational potential stage. Trying to combine them is a bit like trying to combine static and current electricity; in theory you could, but it's inherently problematic. If I were to attempt a complete working model, I would concentrate on only one of these at a time. |
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[+] but I'm not sure there is any ram effect: the water is moving up and down not forward. |
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The ram effect does not respect orientation. A vertical ram would work just fine. You just need to redirect the thrust - in the original idea, indirectly via a storage tank, in my suggested variation, via a simple right angle bend. |
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The simplest conceptualisation I can come up with is a funnel, wide opening facing downwards, with a bend in the neck, such that the narrow opening faces backwards. As the wave slams up / boat slams down, water is forced up the funnel, does a bend, and shoots out the back. |
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Again, the thrust would be puny compared to the direct force of the waves, but since it is directed, the craft should make net progress in the desired direction. |
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([FlyingToaster], I appear to have been infected with your //^// meme, which amusingly seems to mean "the comment I refer to is one that was posted prior to this comment" (as opposed to ...?). Flattery, form of, sincerest, yadda yadda.) |
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^quite, but I contracted it from somebody else here. |
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Ah ok. I should read more thoroughly before posting.
Irregardleslly, we are yet to discuss the practicality of this
in the real world - methinks that all you need is a weak
headwind and the whole endeavour is sunk. |
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//irrigable bow syndrome// |
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I really appreciate the feedback. I swear the conversations on this site are the ultimate learning tool because they stick, y'know? |
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I didn't know that it was called the hydrolic ram principle, I just knew that water traveling down a tube of narrowing diameter exits under pressure and this would let wave energy to lift jets of water to the height of the tank. |
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The hollow struts are just a means to convey and pressurize the water on its inflow and outflow. Combining these shapes into the framework of the boat itself minimizes weight and could theoretically allow the entire contraption, boat, tank, pipes and all to, not only have no moving parts but also, be made all from a single piece. |
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Hydrostatic paradox isn't messing me up. It means that a smaller, taller tank could be just as effective as a larger one though, which is cool. Thank you for that. Very interesting reading. |
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I think you'll be surprised at the thrust this could acheive, but that slosh-factor is key. |
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When a boat crests a wave it speeds up a bit on the descent. When it impacts the trough all of that forward momentum is counteracted and ballances out at less than equal near the crest and wave pushes boat.
By having the weight of the stored water slam into the leading edge of the tank a split second after the hull itself loses its forward momentum then that counteraction will no longer be equal and I have a feeling that this slosh effect alone, given the right shape of arc and tank, could scootch a boat slowly in large waves with no intakes or outlets at all. |
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By incorporating the top lateral shunt baffle, water is fed to the cone shaped outlet chambers just as the already stored water impacts the front of the tank. It merely keeps the system charged with water by circumventing Gravity and Newtons second law just long enough for the weight of the return-slosh to hammer home the pre-charged outlet chambers at the same instant that the boat needs the greatest thrust to crest the next wave. |
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By adding valves, air pressure enters the equation, and I still have yet to find anything pertaining to research done on the golf ball dimple effect in a liquid that might lessen drag using vortices caused from insufficient intake flow. |
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Assume your boat weighs nothing more than the water it holds. Your 10 tonnes of water will move your 10 tonne boat about 5m. |
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It might be better if the sloshing under the hull drives a floating piston that powers a compressor. |
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A catamaran with 3 hulls is a trimaran. |
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//Your 10 tonnes of water will move your 10 tonne boat about 5m.// |
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How was this number arrived at?
Two canoes supporting a fifty gallon tank will travel much, much farther than five meters on a single tank load given no outside factors, so I don't see how that could be correct. It's all about scale and drag. |
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The sloshing could float a piston and that's a good idea, but it's not this one. |
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I used the term Quadmaran to indicate possibly using four pontoons.
If a dual catamaran articulated slightly in the middle then thrust while on the upward side of a wave could be maintained for a longer period of time. |
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This contraption uses waves and gravity more than thrust and in fact should vent no water at all while descending a wave.
The boat moves forward and gains speed on its own while travelling down a wave, this shape just lets it vent all of that stored energy from the last wave to plow through the next one and keep a little bit of its momentum.
The craft now descends the next wave with the tiniest little bit of captured forward momentum it would not have otherwise had and its speed should increase cumulatively until it reaches a maximum determined by wave length, amplitude, drag and wind... and future tweaks on the shape. |
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As long as it can scoop more water than it needs to vent in order to overcome the drag from the scooping then... the dang boat will scootch. |
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What is going to be the size of tank ? That is important. |
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Are you suggesting that boat can move even without a tank, just on momemtum gained while riding down a wave ? |
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Also, what happens when there are no waves ?... |
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hmmm, I don't know the best size of tank. The cad program I've got didn't come with numbers... |
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I am not suggesting that a boat can move even without a tank, just on momemtum gained while riding down a wave at all.
I am suggesting that with a sealed tank of the right shape, arc, and ratio of water to air a boat could make headway in moderate waves without any propulsion system at all.
I don't have any other words to describe what I mean but the ones I've used. I don't know the names of the principles involved in making waves play off one another but the strength of the waves determines the strength of the effect once you overcome drag. |
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When there are no waves you expend the tank for as long as it will go, it lightens the load and you fire up a motor while you wait for wind. |
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I spent an entire summer on the ocean once and I think there were two calm days.
This would make for substantial fuel savings. |
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Ok I did a sketch anyway.
It's a bad sketch but it might help to visualize. [link] |
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Just a couple more thoughts a'fore this sinks to them briny depths... |
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//Your 10 tonnes of water will move your 10 tonne boat about 5m.// |
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um... you meant miles didn't you?
I'm such a dipshit sometimes. Sorry. |
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- If the lateral baffle had flex then the air-to-water ratio in the main tank and the amount of in-flow could be strictly maintained. |
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- If enough speed were gained to raise up on hydrfoils then the twin jets could be combined to vent as a pressurized stream from the entire width of both the fore and aft hydrofoils by adding two more hollow struts connecting the rear of the tank to the front of the pontoons. |
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I don't know how to do the correct calculations, but in space, your boat would travel forever. However in water, you have to displace the same amount of water as you are carrying (plus the boat weight). |
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For example, if you are moving at 1m/s carrying 10 Tonnes of water, it's the same as being a stationary boat with 10 T of water pushing you at 1 m/s. How much water do you think you would have to expel to counter that and maintain your 1 m/s? |
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I'd love someone to do the actual calculations. |
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I can't help you there, but I would like that too. |
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The thing is, it won't need to vent any water to use counter-acting waves to create movement in a fixed direction.
The venting is just icing on the cake. |
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It all comes down to the arc made by the hieght of the tank from the pivot point, and the shape and timing of distribution of stored potential energy from the previous wave determined by the shape of the tank. |
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I just know it works in my head.
That it popped in there full-blown while I was daydreaming about sea critter propulsion,
and that this type of brain-fart usually indicates that it'll work in the real world too, so I would very, very much like to see this one made.
The chances of me being able to pull it off without number crunching ability using garbage, hot-melt glue and holding my tongue just the right way are slim, so if someone out there has the know-how then... bake this. |
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Do it for the wee salmon.
Do it because you can.
Do it for all the little people.
Do it for the unborn children. |
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