Basic HTML Version
A
sk five drivers what the best performing car is,
and you’re likely to get five different answers. The
problem is we all have different criteria by which
we measure that elusive idea called performance.
For some, high performance means gas mileage in the 40s.
For others it means 0 to 60 in less than 5 seconds. Still others
measure performance in terms of cornering on a winding
road. For me it’s about hauling a load of hay bales or a boat.
Not surprisingly, the way we drive depends on the vehicle
we’re driving. Trying to push my three-quarter-ton pickup
through the corners is bound to end in disappointment, as
would an attempt by my neighbor to back his BMW down
the ramp to haul out a 20-foot Whaler. The way we measure
performance has everything to do with the task at hand.
So it is with dive fins. The way we outfit our feet depends
mostly on where we’re going and what we’re doing.
Variations on a theme
Dive fins come in a broad spectrum of shapes, sizes, styles
and stiffness; the particular form of our underwater footwear
shapes the performance we can expect. Let’s start with the
most basic division: full-foot style versus heel-strap. For
snorkeling in warm water, nothing is more comfortable than
a full-foot fin that slips on over bare skin. But when suiting up
in full Jersey-coast wreck-diving gear there is no doubt we’ll
want a heel-strap fin that fits over some nice, warm booties.
Length and flexibility are also important. We can think of
our fins like bicycle gears. Smaller and more flexible is like
low gear: We won’t go too fast, but there won’t be a lot of
leg strain. Longer and less flexible equates to a higher gear:
We work those leg muscles harder and enjoy the speed that
comes with our effort. It’s the same with our fins: What
we’re doing makes a difference. Longer and more rigid fins
will give us the propulsion we need when fully equipped for
fighting currents on cold-water wreck dives. Lightly loaded
for a leisurely roam on the reef, however, we might find we
can easily get the power we need with a shorter fin.
Other features also play a part in fin performance. Slotted-
fin designs have been the propulsion backbone of the dive
business for decades. The slots are said to relieve some
of the pressure on the backstroke and provide a boost in
hydrodynamic efficiency on the power stroke.
About 14 years ago split fins hit the recreational diving
market. Unlike conventional “paddle fins,” split fins sport
a cleft that allows them to assume a propeller-blade
configuration during the power stroke. The force of the blades
against the water causes them to bend into a foil shape, which
designers claim reduces drag while increasing the suction
or lifting force to enhance propulsion. Many divers find that
these fins make them feel like they’re “pedaling in a lower
gear” and moving more quickly. They find these fins great
when it comes to “highway driving” or cruising along the reef.
The downside for some divers is difficulty adapting some
advanced kicking techniques (e.g., the “helicopter turns” or
“backward kicks” used by cave divers) to the split fins. Others
find that different techniques such as “frog kicks” can be
readily used when wearing split fins. Maybe it’s just a matter
of taking our Ferraris and Porsches to the track and sorting
out our driving techniques.
Performance testing
An evaluation of fins reported in Undersea and Hyperbaric
Medicine (Pendergast DR et al., “Evaluation of Fins Used in
Underwater Swimming,” UHM 2003, Vol. 30 No. 1) found
that divers’ perceptions of fin performance are not always
accurate. According to the authors, “divers invariably ranked
the stiff fins as the best and the flexible fins as the worse,
which did not correlate with the objective evaluation of these
fins.” In other words, when using more flexible fins divers
commonly attained speeds greater than they perceived.
Still, scientific data on fin efficiency does not indicate a
clear winner in terms of true fin performance. As Pendergast
concludes, “It is clear that the venturis, vents, trauths [and]
splits in the tested fins did not improve the performance of
the fin.” Pendergast found that different strokes are needed
for different types of fins and performance may vary with the
type of kick used. Tests conducted by Diver magazine focused
primarily on the ability of divers to achieve a high speed
when swimming against a current, and these led to a similar
conclusion. Among the results was the fact that split fins
respond best to a shallow, high-speed kick. Again, we need to
adjust our technique to the type of fin we’re using, just as we
adjust driving technique to the type of car we’re driving.
Finding the best-performing fin may be as difficult as
finding the best-performing car. Is the Chevy Volt better
than the Camaro or the Silverado pickup? The answer
depends on where we’re going and what we’re doing.
Will we cruise a Caribbean reef, explore the jungles of
an underwater kelp forest, penetrate a cave system or
photograph whale sharks off the Costa Rican coast? For my
next trip, maybe I’ll pack two pairs of fins — just in case.
AD
www.alertdiver.com
|
105
If the Snorkel fItS…
The right snorkel is one that fits our purpose and style of diving.
When examining the options, consider the following:
Diameter:
Larger diameters make it
easier to breathe, especially when we’re
working hard.
Comfortable mouthpiece:
Make certain
it fits well and doesn’t chafe the gums.
Purge feature:
A purge can make it
easier to keep the snorkel clear.
Attachment:
Both security and ease of
removal are important.