Jean-du-Sud or
Spray?
◄Jean-du-Sud; for boats below 40'
◄Spray; for larger boats
The
overall length of the yacht is only a rough guide in the choice
between the lighter Jean-du-Sud or heavier
Spray models. The main criterion is in
fact the amount of effort required to turn the rudder.
A 40 ft.
plus boat that is well balanced and easily steered, could still use
the smaller Jean-du-Sud model (provided its freeboard
is not too high). On the other hand, a boat that is not so well
balanced and that is hard to steer, would need the larger and more
powerful Spray or Joshua, even if it is
shorter than 40 ft.
The determining factor in the choice between the two
integrated models is the rudder dimensions (total area, type, aspect
ratio), combined with the height of the horizontal axis above the
waterline. The sail balance should be also taken into account. It is
better in the final analysis to seek our opinion before making the
final decision.
How to Integrate a Jean-du-Sud
or Spray to Your Yacht
Each
CapeHorn Integrated Self-Steering is custom built. In order to
provide a perfect integration between a Spray or
Jean-du-Sud (JdS) and your yacht, the
ideal dimensions of its three main segments must be
determined. The length of the horizontal axis and mounting
tube (LMT), the height of the windvane tower (HWT) are
dependant on the specific shape of the boat's stern section. The
length of the servo-pendulum is determined by the height of the
horizontal axis above the waterline (HWL) and the rudder
dimensions.
Length of Mounting Tube
(LMT)
The
horizontal axis that links the outboard steering oar to the inboard
quadrant pivots inside a tube fastened to the hull, called the
mounting tube. Its length (LMT) is measured from the aft face
of the quadrant to the aftermost part of the hull or any of its
appendages that could be in the way of the steering oar.. The aft
end of the mounting tube should also clear the trailing edge of the
rudder if it extends aft of the hull.
In order
to determine LMT, one must first determine the optimum
position of the CapeHorn quadrant inside the boat. This quadrant can
be placed either in the lazarette or in the cockpit.
Dimensions of the Quadrant
◄Quadrant
radius is 8" (205mm) for JdS and 11" (280 mm ) for
Spray (if space is limited, an 8" quadrant can be
supplied with a Spray.) For 360° quadrant movement,
forward of the tube, a circular space ("CS") diameter of: 16"
(410mm) for JdS and 22" (560mm) for
Spray. JdS quadrant
is 1" (25mm) thick, Spr
quadrant is 1.25" (32mm). If space (inside the lazarette or in the
cockpit) is limited to one half-circle below or above the horizontal
axis, the gear will work just as well, but the possibility of
swinging the pendulum up for storage along the windvane tower is
lost.
Quadrant in Lazarette
If the
quadrant is placed inside the lazarette, its ideal position is
arrived at by taking into account both the space required for the
quadrant itself, and the lead of the control lines. The quadrant
can be mounted indifferently
above or below the horizontal axis. In many lazarette installations,
the top of the quadrant reaches a few inches below the underside of
the deck and the turning blocks can be bolted to the underside of
the deck.►►
Quadrant in Cockpit
The
mounting tube can be made to go through both the transom and the aft
cockpit bulkhead. This puts the quadrant
inside
the cockpit, against the bulkhead, often under a helmsman's seat.
This provides an installation that is both simple to perform, and
structurally strong.◄►
Space for Autopilot
Since
the autopilot only controls the steering oar, the smallest
tiller-type units can be used, even on a large boat.►
If space is limited, the autopilot can also be mounted
elsewhere and connected to CapeHorn control arm through light
control lines.
Height above Waterline (HWL)
◄If the U-shaped
metal plate linking the teak steering oar to its stock is kept above
the water, drag is kept to a minimum. This fitting extends 16"
for JdS and 21" for Spray. below the
horizontal axis and this height is considered as a minimum. If it is
higher, the length of steering oar is increased
accordingly.
Knowing
the height of the horizontal axis above the (dynamic) waterline, and
also the dimensions of the yacht's rudder, allows to optimize the
length of the steering oar and make sure the CapeHorn provides
adequate power to steer any size yacht.
Height of the Windvane Tower
(HWT)
Standard
height of the top of the windvane tower above horizontal axis is 53"
(135 cm) for JdS and 65" (165 cm) for
Spray. In most cases, this places the windvane in
clear air above the stern pulpit. This dimension can be increased to
reach over a pilothouse or bimini,►
◄or reduced to
duck under a mizzen boom.
The light air windvane reaches24"(60
cm) abovethe top of the tower,and the heavy weather vane,
17" (432 mm) (all models). (H)►
Metal
hulls
The mounting tube can be welded to a steel hull. An
aluminium mounting tube can be supplied for welding to an aluminium
hull.►
When
welding is impractical, a Delrin collar is used to bond the mounting
tube.
◄The collar
adapter is cut to the angle of the transom, the mounting tube is
bedded through it and the two halves are bolted together, on either
side of the transom.
Forward End of Mounting Tube
The
forward end of the mounting tube is held in place by two struts
(supplied with appropriate fittings) bolted at an angle between 90°
and 120° on the tube, and cut to reach either the underside of the
deck above, or a pad glassed to the hull below. A reasonable
distance between the tube support at the transom and the struts
forward ensures a strong installation.►
Open Cockpit or Stern
Platform
Instead
of being inside, the struts can be placed outside on boats with
stern platform.►

Second Pair of Struts
A second
pair of struts (extra) can be provided to ensure adequate strength
if the mounting tube extends some distance past the
transom.►
Special
Models
If there is no room inside the
lazarette for the windvane quadrant but an integrated installation
is still desired, (to allow control of the servo-pendulum by a small
autopilot), it is possible to replace the quadrant by extending the
tube housing the servo-pendulum stock above the horizontal axle so
that it works as a control arm.▼►


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