Let's
get technical...
Benefits
of the Hobie MirageDrive mechanism...
>>Eliminates drip from a
paddle.
>>The larger muscles in our
legs produce more powerful propulsion versus a paddle kayak.
>>Leaves hands free for fishing,
photography or holding a drink.
>>Correct paddle usage requires
training and practice.
>>Your feet rest naturally
on the pedals, and can move back and forth quickly and effortlessly.
>>The MirageDrive is quiet
and creates no splash. Performance
The
Hobie MirageDrive propels the boat easily and smoothly, and
reaches hull speed with minimal effort. It also generates
significant static thrust. In a "tug-of-war" between
a single Hobie Mirage and a tandem paddled kayak, the Hobie
Mirage won hands-down (pun intended). Check out the video
below!
Efficiency
Even
we were surprised at the efficiency of the MirageDrive. In
a test to compare the efficiency of the MirageDrive, we measured
the heart rates of several kayakers at varying speeds in several
paddled kayak models. In every case, the heart rate-or effort
expended to maintain a particular speed-was three to ten percent
less for pedaling versus paddling. Translation? The MirageDrive
converts the effort of the human body into forward thrust
more efficiently than a paddle! Allow us to explain.
The
MirageDrive creates less turbulence in water. This becomes
apparent when you compare the wake of a Hobie Mirage to the
wake of a paddled kayak. With each stroke of the paddle, you'll
see two vortices, or whirlpools, on the surface of the water.
These vortices are connected underwater, and there is considerable
energy in these rotating masses of water. There are vortices
in the wake of the MirageDrive, but since the MirageDrive
acts on a much larger volume of water, they are much smaller
and therefore contain less energy. To create forward thrust
on the water, a boat must move water backward. It can either
move a little water quickly, or a lot of water slowly. The
key to efficiency is to move a lot of water slowly with the
least amount of turbulence. The volume of water that the MirageDrive
acts upon is approximately proportionate to the area that
the fins sweep in one cycle, or about 226 square inches. The
volume of water that a paddle acts upon depends on the type
of stroke. A basic stroke would act upon a volume of water
proportionate to the area of the paddle, or about 90 square
inches. This is just a fraction of the area "swept out"
by the MirageDrive, which explains the difference in efficiency.
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Why
not use a propeller?
>>Human-powered
propeller drives are typically smaller and therefore less
efficient. We compared the performance of the MirageDrive
to a propeller drive, and found the MirageDrive to be faster
and more efficient.
>>Studies on tuna and penguins
show that oscillating foils such as the MirageDrive are more
efficient than propellers. Oscillating foils can make use
of vortices that are naturally shed from anything going through
the water to offset the vortices that would normally be generated
by fins. This equates to less turbulence in the water.
>>The MirageDrive fins
"feather" into the flow when not pedaling and create
very little drag; a propeller creates significant drag when
it is not spinning.
>>The back-and-forth motion
of the pedals provides a long, smooth stroke. Pedals that
go in circles on a boat have a much different feel than pedals
on a bike. On a boat, there are portions of a circular motion
that are more difficult, so the cycle is not smooth.
>>The back-and-forth motion
allows the pedals to be positioned much lower in the cockpit.
>>The MirageDrive allows
any length of stroke desired, and performs well with both
short and long strokes.
>>The pedals easily adjust
to accommodate different size pedalers.
>>The oscillating motion
allows the use of a simple chain and cable system that is
unaffected by sand and dirt, without the use of complicated
seals.
>>The fins shed seaweed
because they do not make a full rotation.
>>The MirageDrive fins
fold up next to the hull for beaching and in shallow water
by simply putting one foot forward.
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