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Control:
Diver Steering and Roll Control
Roll-trim buoyancy is a process by which a swimmer can control their roll orientation in
the water. A swimmer, extended horizontally in the water, can control roll orientation by
simply bending his/her body from side to side as illustrated in
Figure 5
. A swimmer’s
heavy legs at one end and the heavy head and arms at the other end will sink in relation to
the more buoyant chest area. Therefore, if the swimmer bends his/her body reaching
toward the right, the swimmer’s body will roll to the right. If the swimmer bends his/her
body reaching to the left, the swimmer’s body will roll toward the left. In this way, roll
trim buoyancy can be used to control ones roll orientation in water. This is also how
steering is accomplished while under propulsion with the DOL-Fin. As a user becomes
proficient with the DOL-Fin, they will learn how to use roll-trim buoyancy for control
without interrupting the swimming stroke.
FIG 5
Diver Bends
Towards
The Right
Induces Roll
Towards The
Right
Diver Bends
Towards
The Left
Induces Roll
Towards The
Left
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Controlling Fin Twist and Side-Slipping
A common problem many people have when first using the DOL-Fin is avoiding fin twist
and side-slip when stroking the fin. Don’t get discouraged. It is a little like learning to
ride a bicycle. It takes some practice, but once you know how to do it, it feels completely
natural.
The important thing to remember is that the DOL-Fin is a “Dynamic Oscillating Lateral-
Fin”, not a “Dynamic Oscillating Skewed-Fin”. The fin should always be stroked in a
direction that is orthogonal (90 degrees) to the span (i.e. – long axis) of the hydrofoil fin.
If the fin is twisted in roll relative to the diver’s upper body, and the diver inappropriately
strokes the fin orthogonal to his upper body rather than orthogonal to the fin’s span, the fin
may side-slip and tend to increase the amount of roll misalignment in the fin with each
down-stroke.
To become proficient at swimming with the DOL-Fin, the diver will need to learn to sense
the fin’s orientation through their feet and stroke the fin in the direction orthogonal to that
sensed fin orientation. This may take a little practice to become proficient, but before
long, the desired body motions will become automatic and happen without having to
consciously think about it.
Adhering to this method will stabilize the fin and prevent it from deviating from optimum
orientation. Until even kicking is learned, a twisted fin can be corrected by a coast period
where roll-trim buoyancy can be used to pull the fin back into position. With continued
practice, the coast can be eliminated and smooth even kicking will become completely
natural.
Deploying and Folding Fin Tips
The fin tips deploy by simply plugging them into the ends of the aluminum hydrofoil,
which places the fin in swimming configuration. To fold, simply unplug the fin tips from
the foil ends and fold over the topside of the foil. The fin tips can be secured in the folded
position by slipping rubber bands over the fin tips and foil.
