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longer bottom guide to a preferred length to make a new custom top suspension guide. A
disk sander works well for this. Just make sure to trim them square and with even lengths.
The length of the top suspension guides is largely a biometric fit to match the flexibility of
a person’s ankles. Therefore, most individuals will find a particular length set that they
most prefer and will not change it after that. However, there may be times when a diver
may want to change settings of their fin, such as when changing from performance
freediving to spear-fishing or photography where the swimmer’s drag profile is increased.
Selecting a suspension guide may optimize the fin to better accommodate swimming
configurations with more drag.
Swimming With the DOL-Fin:
The DOL-Fin Orca is more forgiving of a knee kick technique than are other monofins.
However, good monofin technique with straight knees and proper core undulation will
improve your overall efficiency and swimming performance. One important tip for
freedivers is to not over-kick the fin. Keep the amplitude of the fin strokes relatively small
and don’t over-bend the knees. It is interesting to note that your fin will produce a
surprising amount of speed from nothing more than flexing the ankles. Experiment with
this ankle only method, as the best stroke techniques incorporates ankle flexing with the
calf muscles in synchronization with the body undulation that is common to monofin use.
The DOL-Fins are capable of producing more thrust on the return stroke than other
monofins and if you don’t master the calf/ankle movements, you will be missing out on a
significant portion of the DOL-Fin’s capabilities. Continuous low amplitude motions of
the fin will help to keep the swimmer’s body more streamline for drag reduction and
speed.
The fin motion produces alternating patterns of starting vortices of the oscillating fin,
which forms a reverse Kármán vortex street to focus a powerful jet of water flowing
through the volume affected by the fin as illustrated in
Figure 4
. The fin motion is shown
in black. The reverse Kármán vortex street and resulting flow of water are shown in grey.
This flow of water provides an efficient generation of hydrodynamic thrust. In general,
faster DOL-Fin swimming requires a higher frequency cycle rather than a larger amplitude
cycle.
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FIG 4
Propulsive efficiency can be of benefit at any swimming speed and sometimes slowing
down has significant advantages. Particularly for freediving, incorporating two fin kicks
followed by a glide period in a repeating pattern is an effective and commonly used
method for reducing energy consumption. The two kicks together maintain the
appropriate vortex spacing illustrated in Figure 6 to focus the water flow, but it also
reduces the total power input and provides time for the muscles to relax and conserve
energy. Since the power required for propulsion rises to the third power of the speed
attained, an intermediate swimming speed is the best way to maximize economy and
distance covered on a single breath. For example, if a swimmer is to double his/her
swimming speed, he/she will have to produce eight times the power needed at the slower
speed. This high power requirement can rapidly exhaust the available air supply.
Swimming fast is fun, but it unfortunately comes at a cost.
Streamlining becomes increasingly important as a swimmer’s speed increases. For
freediving, a swimmer can substantially reduce his/her frontal cross section area and
therefore drag, by extending his/her arms in front with hands overlapping, and tucking the
shoulders in tight around the ears with the chin tucked lowering the position of the head.
Induced Flow
Fin
Motion
