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Hovercrafts need somewhat smooth terrain.
Helicopters
require a lot of power and need to go high to be safe.
The Ground Effect Tricopter is something in between.
It
relies on ground effect to lift off the ground. This
reduces
the power requirement. It has three rotors that are
shielded
with a wire mesh, somewhat similar to what
you
see on airboats. It will fly at around 6 feet above
ground
or water.
The three rotors make it stable. The engine is located
in
the center of the craft, with a vertical drive shaft.
This
shaft contains three pulleys with three drive belts that
drive the three rotors.
Each rotor also has a diaphragm iris below it. By closing
the diaphragm, the power to that rotor can be
reduced.
A ring around the rotor keeps things efficient. By
varying
the relative power to the three rotors, the craft can
be
tilted. By doing this, the direction of thrust is tilted
from
the vertical axis and the craft will move horizontally.
Microcontrollers control the amount each iris will close.
With the aid of accelerometers, this can make the
craft
responsive and stable. It will be able to go from full
speed
to a stop without oscillating.
Obviously, you want to be able to not just change
horizontal direction, but also to turn. I'm not sure what
the best way is to make it turn. Perhaps it can turn by
pulsing the engine power.
It would not surprise me if this idea has been described
in
Popular Mechanics in 1902.
DC-3 on floats? We already got one!
http://www.oocities...pids/3870/dc3-2.jpg
Charter service out of Moosehead Lake at Greenville, ME [Alterother, Dec 21 2011]
Pedal-Powered Ekranoplan
Pedal_20Powered_20Ekranoplan
Great fun. [Alterother, Dec 21 2011]
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Annotation:
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A prototype "airbike" on almost exactly these principles has
been demonstrated in Australia … try Googling. |
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a) even number of rotors, not odd. |
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b) I wouldn't bet on getting enough ground effect for a 6ft altitude. |
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c) steep hills, which would be navigable by 'copter or hovercraft, will be impossible. |
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(I haven't had a full cup of coffee yet, so a) & b) might just be my brain tossing crap out) |
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Helicopter: helico- (spiral), -pter (wing). |
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Tricopter: trico(t)- (knitted), -pter (wing). |
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The Ground Effect Rotor Craft, or GERC, is a concept I came up with (at least to a theoretical level) about 11 years ago, only my idea was to use a single main rotor, with a standard helicopter-style tail rotor. But having 3 (or 4) lift rotors makes sense.
Get yourself an RC quadracopter, modify it, and see how well it might work. |
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Sorry, but stuff with wings works better..and took me a long time to work out why...wings are lift accumulators if you'll pardon the analogy. |
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//Each rotor also has a diaphragm iris below it. By closing the diaphragm, the power to that rotor can be reduced.// |
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Wouldn't it be easier to alter the pitch of the rotor blades or reduce the power going to the rotor in the first place? |
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Keeping them at the same speed or angle is a bit tough as there's still the reaction of the air being pushed down and just blowing it against a closed diaphragm seem either wasteful in energy and it means a stronger and heavier airframe as the diaphragm has to be strong enough to withstand the air pressure from the rotor. |
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Or am I misunderstanding this? Drawing please. |
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//lift accumulator// I think effective GE altitude is the chord of the wing... so on a helicopter you'd be looking at 6" not 6'. |
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/I'm not sure what the best way is to make it turn/ |
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Wouldn't tilting it make it turn also? |
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I took //turn// to mean yaw. The biggest difficulty might be in preventing it from turning, since it is a fermion, so to speak. |
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// alter the pitch of the rotor blades or reduce the power // |
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Pitch control is superior to power control - Igor Sikorsky demonstrated that pretty conclusively. |
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An iris will cause huge amounts of rotor flutter and backwash, maybe even causing rotor stall at certain critical combinations of RPM and airflow. NOT good. |
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// on a helicopter you'd be looking at 6" not 6' // |
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Sort of right, but not applicable to rotary wing design, either helicopters or Flettner wings. |
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// Wouldn't tilting it make it turn also? // |
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Yes. Beware gyroscopic effects. The trick there is contrarotating impellers, but the hub forces can still be distressingly large. |
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The proposal falls into the awkward gap between an PCV and a GEV. Go talk to the Ekranoplan designers. |
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Aaach, quit whining. You saw the sign when you came in here, the one that said "HalfBakery: No Exit". |
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Don't make out that it's anyone's fault but your own. |
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Did I say I was upset about it? I'd chew off my own right
arm--well, I'd chew off somebody's arm, anyway--for the
chance to argue about Ekranoplans again, especially if I
get to use my double-Catalina allegory model... |
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Ah, the Consolidated PBY-5A and its heirs and successors. A DC-3 with the added benefit that if you're hungry, you can land on any handy body of water and go fishing. |
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<sputter> a PBY-5 is in no way shape or form related to a DC3 excepting both could be described as "medium-sized twin-radial aeroplanes of a certain vintage which usage has survived". |
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If you just want to go fishin' some people have put DC3's on floats. |
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[Ao] mitigated wingtip vortices (very nice) and an assumed inertia-related robustness dealing with oopsies while negotiating banking turns ? |
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(on another note when did the "resize" corner appear in the anno-posting box ?) |
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They use the same Wright powerplants. They have a similar modest wing loading. While their handling is very different, their cruise speed and endurance are not dissimilar. |
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Both were tough, resilient, and much loved by their crews. |
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I think if you'll notice the Cat' is almost twice the weight and wing area of the Gooney Bird... and an amphibian... and using the same engines, you'll find that there's no way their cruising speed is going to be similar. |
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They're more or less the same length and wingspan, and they use the same engines... which easily describes 20 other vintage aircraft. |
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// the Cat' is almost twice the weight and wing area of the
Gooney Bird... // |
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Which is why I rejected the C-47 in my comparison study.
It was a nice coincidence that the PBY's wing profile is very
similar to the B-24's. |
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Ah, a deezeesree on a-floats? We already got one, you
see? |
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</outrageeeous franchman> |
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//coincidence// yes, that the Consolidated PBY's wing is similar to the Consolidated B24... |
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Meanwhile what's this about comparing a PBY to an Ekranoplan ? |
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I wasn't comparing a PBY to an Ekranoplan. I was
comparing two PBYs to a B-24. See <link>; it's around the
middle of the anno thread. |
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//two PBYs// No, they'd have to have it on a line. |
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Not if they was from the Pacific thee-ater, they wouldn't! |
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Ah I see... I thought you wanted to stick a PBY5 body on both sides of a single, twin-engined section of PBY wing to make an ekranoplan. |
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