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Technical Data: Rudder
Rudder Blade
- A
‘balanced area’ rudder is important. An unbalanced rudder can cause the
servo to act inconsistently and cause it to fail. They chatter when turned on.
The area in the leading portion (that area forward of the shaft axis) has to
be considered. This aspect shall be elaborated upon.
Rudder Shaft
-
Generally these are 4 mm diameter, although 3mm diameter have been sighted.
Stainless Steel shops sell these items.
Rudder Shaft Tube
- These are commonly brass and are available from Hobby shops. A brass washer
is soldered onto the tube on the inside side where it leaves the hull. This
permits the firm fixation by epoxy glue and cloth. Low friction bushes are
known of.
Rudder Arm - A Dubro
fitting
Pushrods - are generally 1.6 mm
diameter Stainless Steel welding rods, from Welding Supply outlets. Although carbon
tube with heavy duty ball links provides a more positive relationship
are also an option, there are not permitted in some class rules. Ball Link
DUB884 Heavy
Duty 4-40 Ball Links and horn assembly connecting the servo to the rudder will reward
you every time you sail. Not only will the rudder centre precisely on each
tack, but as your yacht is hard pressed, reaching and on the run, the chances
of ‘broaching’ due to a sloppy linkage, or a servo which is not capable of
holding the rudder exactly where you command it will be minimised.
Starting at the stern, make sure the rudder post and stern tube are a good
fit and apply waterproof grease. Use a metal horn such as the SAILSetc 68b.
Keeping the rudder servo near the centre of the
boat helps to reduce tacking inertia but it means a longer pushrod will be
required. Using carbon tube with heavy duty ball
links each end is the best way of achieving the absolute minimum slop.
Now the SERVO end! Firstly the output arm, either metal available from K.
Bits. or use the large plastic disc supplied with Futaba servos which is far
stiffer than the plastic arm type which is more
likely to twist under our duty.
When choosing a servo for the rudder function.. and we only need one, it
pays make the right choice. The Futaba P-S9303
High Torque buggy servo should be at the top of your list.
Seriously powerful 7.2kg/cm,
Water and dust resistant, dual ball raced, metal geared, 0.19sec/60 deg,
coreless motor and in a small case (40.5x20x39.5mm) weighing
64.5g
the 9303 has to be the serious competitors choice for all weather sailing.
Next would be the Futaba P-S9202, helicopter servo, lower priced but still with high torque and an
excellent specification. Torque 5.0kg/cm,
Water and dust resistant, dual ball raced, 0.22sec/60 deg, coreless motor and
in a slightly smaller case weighing 50g.
Still has the incredible holding power required, designed for heavy duty and
is suitable for yachts.
Still with a coreless motor the standard Futaba
P-S9001 comes with ball raced output, torque
3.9kg/cm,
0.22sec/60 deg and weighs 48g.
If force 8 ‘C’ suit sailing is not quite your scene! then the 9001 will
serve you well.
At the budget end of the range the Futaba
S3001 still features a ball raced output, torque
3.0kg/cm,
0.22sec/60 deg and weighs 45.1g.
But if cost is really at the far end of the list the ultimate servo has to
be. the Futaba P-S9204 with its
massive 9.5 kg/cm torque, and
0.19sec/60 deg, coreless motor, dual Ballraced, precision cut aluminum gears,
all in a normal size, dust/water resistant servo case. A truly professional
servo designed for the extreme duty of i.c. buggies and power boats, this
servo will suit all classes of yacht.
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