Benefits
of the Hobie MirageDrive
The
MirageDrive is simple and easy to use. Your feet rest naturally on the
pedals and you pedal effortlessly back and forth... just like walking. The
larger muscles in our legs produce more powerful propulsion versus arms using
a paddle. In addition, correct paddle usage requires training and practice. You
also stay drier as pedaling eliminates drips that you get from using a paddle. The MirageDrive is quiet and creates no splash. The Hobie MirageDrive leaves
your hands free for fishing, photography or holding a drink.
Let's
get technical...
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.
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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