Brian Whatcott wrote:

If you are visualizing what I am visualizing, then two single acting
rams can substiture for one double acting ram.
Each s.a. ram needs to develop the full torque: one to starboard, the
other to port. There is no difference on the torque experienced by
the rudder post, as far as I can see.

Brian W


Actually, there is a difference and two pushing cylinders make it worse.
Think force vectors for a second. Lets assume we have a 72º hard over
to hard over rudder angle and with the rudder amidships the ram
intersects the centerline of the rudder at 45º. When the cylinder
extends the ram's force is opposed by two forces. One is the water
pushing sideways and the other is the rudder itself pulling against the
pintle. The sum of the two vectors is in line with the ram. As the
rudder turns away from the cylinder that angle gets narrower and the
force opposing the cylinder starts to line up with the rudder creating
more stress on the pintle than usefull turning force.

If the cylinders pull just the oposite happens. As the rudder goes hard
over towards the cylinder the turning force vector increases while the
stress on the pintle decreases.

--
Glenn Ashmore

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