h a l f b a k e r yContrary to popular belief
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If fish can move so fast by at one flick of their tails, so should boats. I suggest a large tail just like sharks have, at the rear end of boat for propulsion; Tail will move just like fish's tail. If not fast, it should be atleast very fuel efficient.
May be an improved and enlarged rudder itself
cn be used as a tail for propulsion.
http://books.google...like%20fish&f=false
[2 fries shy of a happy meal, Jan 10 2012]
http://newslite.tv/...wiggle-and-swi.html
[2 fries shy of a happy meal, Jan 10 2012]
"Caught a crab, did you?"
http://www.bhfinder...ng-Instruction.html
[normzone, Jan 11 2012]
How to Scull a Boat
http://www.jesterinfo.org/howtoscull.html
Article taken from WOODEN BOAT #100, June 1991. [baconbrain, Jan 11 2012]
(?) Hobie MirageDrive
http://www.hobiecat...atures/miragedrive/
Two pedals drive a pair of underwater fins – much like a penguin’s flippers. [baconbrain, Jan 11 2012]
Elastic Tail Propulsion at Low Reynolds Number - An ... - MIT
web.mit.edu/tonyyu/www/includes/Quals.pdf
[beanangel, Jan 12 2012]
Tubot
Tubot#1104896113 Tubot
Osphenarians apparently do this [Ling, Jan 13 2012]
yar...
Jolly-Roger_20Ram-Jet
[2 fries shy of a happy meal, Jan 14 2012]
[link]
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Well... There's an old popular science mag about using a flexible rudder to counter ballance the side-to-side action of paddling [link], and there are articles about future boats using this method of propulsion once the biomimetics are worked out, [link]. |
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...and you can google robot tuna for extra credit. |
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Thanks for links 2fries, 21Q. |
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I think two counteracting tails should give much smoother ride cancelling out jerks. Will be good for catamarans. One tail for each hull. |
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Did you never read Arthur Ransom's books when young? 'Sculling' the boat silently forward by wriggling a single oar over the transom was a regular part of the protagonists' stealth operations. |
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I happen to be working on this very idea, in real life, but I am fishboning this posting because it is mostly just a wish. It has no method at all, and seems to imply that tails are magic. |
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I've sculled boats with a single oar over the back, and it really is a good way to make a boat move. And it makes a good rudder. |
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That Star Wars Bongo, by the way, was to me one of the dumbest parts of a pretty bad movie. |
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I tried sculling once after seeing someone make it look effortless. I wound up swimming the boat back to shore. |
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Pre-internet, of course. I could probably find instructions online nowadays. |
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I've been vaguely interested in biomimetic watercraft propulsion for some years now. The biggest question is which form of aquatic animal swimming to copy:
1: Horizontal flat tail
2: Vertical flat tail
3: Long thin tail
4: Peristaltic waterjet
5: Side fins (2 or 4)
6: Wings
7: Rippling side-strips
8: Alternating folding rear fins
9: Circumferential pulsating strip
(Points to those who can find an animal for each form; extra points if some-one can find a form I missed...) |
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// Pre-internet, of course. I could probably find instructions online nowadays. // |
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I have the link in my bookmarks, and still have the paper magazine with the original article. I even disagree with the author about which sculling method--falling leaf versus knife-edge--to use in which case. Sad, innit? |
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BTW, [normzone]'s link is to sculling as in rowing for Oxford, which is done with two elegantly-crafted sculls out to the sides while sitting facing backwards on a sliding seat in a racing scull, and is an expensive competitive sport. The fishtail kind of sculling is done with one cheap oar over the back of a normal rowboat and is third-world transportation and a way to sneak up on ducks. |
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[neutrinos_shadow], your impressive list left out the semi-aquatic animals who do the dog-paddle with their feet. Not that you'd want to copy that. |
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I saw something like this idea in a sea-kayak race in Seattle once. I and a mob of other people paddled across Puget Sound and back, many of us passing a fellow who had rigged up his kayak with some kind of fishtailing sculling mechanism. IIRC, he was doing fore-arm jabs with two handles, with rods running back under his arms--they were supported by rollers on the deck--connecting to a pivot quite like the rudders on many of the other kayaks, and an oscillating arm about two feet long that had a pivoting fin sticking down, with stops to limit how much it pivoted. |
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As I said, I passed him. When he trundled in to the finish, the announcer started swooning about the guy who had "pedaled with his hands". I wanted to whack him with my paddle. |
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The fishtail man could only use his hands and arms, he had a complicated mechanism behind him, no reverse, no way to actively stabilize his boat, no way to shift hand position or vary leverage, and had nothing to lean on when docking (or when lounging about on shore). (And nothing to wave at the damn motorboat that went blindly across the race (or to whack a salmon over the head with, but that was another day).) |
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I am all for sculling, but not when done like that guy did it. |
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Whales and dolphins are easily trained with a bucket of fish. Simply harpoon a trailer hitch to one, then... dang, that's where the plan falls down. |
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I suspect that a vertical, high aspect ratio tail, like that of a
barracuda or shark, is the best of the bunch, on the grounds that
animals that use a different system all seem to be constrained
by evolution (penguins, cetaceans, sea snakes, seals, lampreys)
or specialised other than for efficient open-water travel (rays
and other bottom-dwellers, sea horses, eels). In other words,
fast fish could have evolved other methods, but didn't. |
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But tail-wagging boats, like motor vehicles with legs, is an
obvious and old idea. I also doubt that it could be significantly
more efficient than a propellor. It could conceivably be more
versatile (efficient over a wider speed range), but only if the
angle of attack were controllable. |
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or is that no.3 which covers flagella? |
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11. propulsion by farting
12. hitchhiking (think: lamprey) |
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[baconbrain], I'll have to check out your link. That's the style of sculling I was trying to do, but the story in the link I found was too amusing to pass up. |
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If you tow a rope in the water it converts the lineal forward motion into flagella-type movement. Presumably the reversal of this conversion is what is happening with flagella. |
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Waxing pedantic, are you sure you sure it was
flagellar, rather than ciliary motion? If the rope
were moving like a flagellum, it ought to get
supercoiled like a telephone handset cable, or
else require
some sort of pivot attachment to the boat.
As [Ling] pointed out, flagellae rotate
continuously without reversing
direction* about an axis running bow to stern;
flagellae beat back and forth (reversing direction)
about an axis running keel to masthead. |
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*they do reverse, sometimes, but only to steer. |
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There are two types of flagella. Bacterial ones rotate, while eukaryote ones undulate. It's a bit annoying that the same word is used for such different structures, but there it is. |
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//There are two types of flagella// |
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Waning pedantic. Thanks again [spidermother]. |
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[neutrinos_shadow], I think there could be a new entry on your list. |
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The protozoan 'mixotricha paradoxa' has a dense coat of waving cilia all over, in addition to the bog-standard large flagella at the ends. The cilia are used for propulsion. |
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The cilia turn out to be spirochetes, living, attached to the outside of the protozoan. (Thanks to Richard Dawkins.) |
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//extra points if some-one can find a form I missed...// |
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Much as I long for extra points I just can't think of a single one you didn't cover, but pondering it gave me an idea for an awesome new mechanical aquatic propulsion system... |
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I do believe this one may need a sketch.
I'll be back. |
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//extra points if some-one can find a form I
missed// |
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Osphenarians "swim" toroidally. Imagine a ring-
doughnut turning through itself; now imagine that
the hole is much smaller, and also that it's longer
from front to back, so the shape is like a grape with
a hole down its long axis. |
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So, [MB], the Tubot (link) is baked? |
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I think he means like a vortex ring [Ling].
I would have never thought that a critter could move like that. |
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Thanks for the inspiration!
[link] |
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