Integrated Self-Steering
Integrating
Self-Steering
to the stern of a boat
ensures both a strong
and elegant installation,
part of the gear
remaining hidden inside.
It also allows to
lead control lines internally to blocks
on boat's steering quadrant,
then to jamming cleats in cockpit
for instant connect,
disconnect or trim.
Additional bonus :
when wind is unstable or inexistant,
a small tiller pilot
located inside the lazarette
drives the servo-pendulum
which still provides power
to move the rudder,
feeding on mere milliamps.
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Integrating CapeHorn
easier than it looks
- even afloat
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All necessary
fittings provided.
However, blocks
and other hardware
needed to lead lines to boat's
steering system
are not, being different in type on
different boats. |
A hole saw held perfectly horizontal
and parallel to keel cleanly cuts
hole for support tube.
Glass laminate (or weld)
aft end of tube to hull. |
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Forward end of mounting tube
supported by two struts
(supplied with appropriate fittings)
at an angle between 90° and 120°,
to reach either underside of deck
or pads bonded to hull. |
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Struts outside
on stern platform.
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Tube welded to steel hull.
Aluminium tube offered
for welding to aluminum hull.
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Welding
impractical?
Delrin collar
cut
to transom angle,
two halves bolted together,
both sides of transom. |
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Second pair of struts
added
if mounting tube extends
some distance past transom |
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Outboard rudder or boarding ladder?,
CapeHorn off-centre.
Only measurable effect of offset
felt if boom extends far aft, close to vane : boat could not sail
as close to wind when vane on leeward
side, wind received by vane being deflected by leech of sail
directly to windward ; other tack, or as soon as sheets are
eased, problem disappears.
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Reduced paddle area when heeled has no effect because when
there is heel, there is most often speed. The force
generated by the paddle being proportional to the
square of speed through water, the paddle generates much more
power than is needed; paddle area is critical only at
low speed, which produces little heel.
All struts and braces adjustable.
Slip horizontal axle through tube.
Fasten quadrant to forward end,
wind vane tower aft.
Diagonal braces to deck
support tower
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Control lines led through blocks
fastened to quadrant or disk
or short auxiliary tiller
(such as the tiller of a hydraulic system).
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To ensure ideal 2:1 ratio
between CH quadrant tilt
and rudder angle
(for 10° tilt, 5° rudder),
blocks located
from rudder axis
at distance
equal to CH quadrant radius.
From there, lines
are led
to jamming cleats in cockpit.
for instant connect, disconnect or trim.
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Vane connected
and adjusted for weather or lee helm
by pulling lines tight
and cleating them.
Releasing lines
instantly disconnects vane
for hand steering. |
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Click here to see various
internal connections
Internal connection impractical?
Control lines turn wheel
by going around stops
placed on wheel spokes
at distance
from wheel hub
ensuring 2:1 ratio
between quadrant tilt
and rudder
angle.
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Teak drum
on wooden wheel.
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Control lines
led through fairleads on tiller
located at a distance
twice
the radius of CH quadrant
(2:1
ratio),
then forward to jamming cleats.
If quadrant
is inside and tiller outside,
Control lines are led out
through holes in sides or back of cockpit;
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No room inside lazarette
for windvane quadrant ?
A tube extends
above horizontal axle,
to work as control arm.
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On a boat with outboard rudder,
gear offset
Power transmitted
to back of rudder head
through lines
led to blocks on rudder head.
Since there are no lines to it,
tiller can be lifted to vertical
(or removed)
while CapeHorn is steering,
leaving cockpit
free of obstruction.
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Norwegian stern,
servo-pendulum
connected to back of rudder
through rigid control arm
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To allow use of davits on boat with step stern,
windvane tower at forward end of horizontal axle
passing through the deck. |
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If your boat
presents a specific problem, send us photos showing its
stern and steering gear belowdecks.
We are not
without imagination and may suggest an original
solution.
Jean-du-Sud
or Spray?
Jean-du-Sud
for boats below 35'-40'
Spray ; for larger boats
Overall length of yacht
is only a rough guide
in the choice between
the lighterJean-du-Sud
or heavier
Spray models.
The main criterion is in fact the size of its rudder
and the amount of effort required to move it.
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.
Determining factor in the choice
is the rudder dimensions (total area, type, aspect
ratio), combined with height of horizontal axis above
the waterline. Sail balance should be also taken into
account.
Mounting tube (OD)
JdS 2.5" (62 mm), Spr
3.5" (89 mm)
Stock of steering oar JdS 1" (25
mm) Spr
1.25" (32 mm)
Width of paddle
JdS 5" (127 mm)
Spr 6" (152 mm)
Paddle length proportional to boat's rudder
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How to measure |
To
custom-build a CapeHorn
four dimensions needed:
-LMT (Length of Mounting Tube)
-HWT (Height of Windvane Tower)
-HWL (Height of horizontal axle above WaterLine)
-Average height and width of rudder
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Length of Mounting Tube (LMT)
Horizontal axle links outboard steering oar
to inboard quadrant
pivoting inside tube passing through hull
called Mounting Tube.
Its length (LMT) is measured
between aft face of CapeHorn quadrant
to aftermost part of hull
or any of its appendages
that could be in way of steering oar..
Aft end of the mounting
tube should also clear
trailing edge of rudder
if it extends past hull.
To measure LMT,
first determine
the optimum position of CapeHorn quadrant
in lazarette or cockpit.
Dimensions of Quadrant
Quadrant
radius :
-JdS : 8" (205mm) 1" (25 mm) thick
-Spray :11" (280 mm ) 1.25" (32 mm) thick
For 360°
quadrant movement, circular space (CS)
needed at forward end of tube :
- 16" (410mm) diameter for JdS
- 22" (560mm) for Spray
If space (inside lazarette
or in cockpit) is limited to one half-circle below
or above the horizontal axis, gear will work just as
well, but possibility of flipping pendulum up
for storage along windvane tower is lost.
If
only a few inches short, a smaller quadrant is supplied.
Performance is not affected and ideal 2 : 1
ratio between quadrant tilt and rudder angle is
retained if blocks on steering quadrant (or aux.
tiller) are placed at a distance (from rudder axis) equal
to CapeHorn quadrant radius. Only load on control lines and blocks is increased.
If
Quadrant inside lazarette,
Ideal position arrived at
by taking into account
both space required for quadrant itself,
and lead of control lines.
Quadrant mounted indifferently above or below
horizontal axle.
In many lazarette installations, top of quadrant
reaches a few inches below deck
and turning blocks can be bolted under it. |
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Mounting tube
through both
transom
and aft cockpit bulkhead, locates quadrant
in cockpit, (often under helmsman's seat)... |
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...ensures both simple and
strong
installation,
both ends of tube
supported by a bulkhead.
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Leave room for
autopilot connected
to co-axial control mechanism
in front of quadrant.
Since autopilot
only controls steering oar, smallest tiller-type
unit steers regardless of boat size, feeding on mere
milliamps.
If space is limited, autopilot can be located
elsewhere and connected to control arm through
blocks and light lines (with bungee pulling the other way).
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Height above Waterline (HWL)
If U-shaped metal plate
linking steering oar to its stock
is kept above water,
drag kept to minimum.
Plate extends below
horizontal axle
13" for JdS
19" for
Spray
This height is considered a
minimum.
Knowing height
of horizontal axle
above waterline and dimensions of yacht's rudder
ensures steering oar provides adequate power
to move rudder in
all conditions,
with minimum drag.
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Standard Height of Windvane Tower (HWT)
(above horizontal axle)
-JdS: 53" (135 cm)
-Spray:65" (165 cm) |
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In most cases
locates windvane
in clean air.
Increased
to reach over
pilothouse,
bimini
or arch |
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reduced
to duck under
mizzen boom.
Arch
high enough,
vane kept below, |
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Light air vane
extends
24" (60 cm)
above top of tower,
heavy weather vane,
17" (432 mm) |
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See a complete installation of a Spray on a Valiant 40
Suite : Outboard Models
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