V-Drive Maneuvering - Regal 3760 Owner's Manual

V-DRIVE MANEUVERING

Twin-screw (sometimes called twin-inboard or V-drive)
boats use twin rudders located directly behind each
propeller. These propellers are counter-rotating which will
balance steering torque. On Regal twin-screws the port
propeller is left-handed and the starboard propeller is right-
handed. Mark the propellers in case they need to be
changed or repaired at some point as they could be
mismatched on reinstallation since they both fit the shaft.
Moving forward with the starboard engine for a port turn,
the propeller offset from the centerline enhances
significantly to pushing the stern to starboard.
In reverse, the starboard propeller throws it thrust energy
toward the starboard side of the hull to assist in turning
the stern to port. The port propeller reversing, throws its
thrust against the port hull side to assist the pivot of the
stern to starboard.
The important ingredients in turning and steering are
combined by the outward turning propellers. The steering
result is used in the same direction as the turning movement
caused by the off centerline propeller location.
GATHERING HEADWAY
As opposed to a boat with a single propeller, if the V-
drive transmission of a twin-screw vessel are put in gear
together, the vessel will make headway without the
tendency to pull to the port or starboard. Of course the
throttles must be in the same rpm range as read on the
tachometers. This factor is very basic to this type of vessel
having superior handling and control in tight spaces along
with being able to handle wind and current much more
adequately than single screw or outdrive boats.
TURNING
When you have two propellers available it provides the
skipper a means of shifting one propeller or the other
forward or reverse without the assistance of the rudder.
When maneuvering at slow speeds the steering wheel is
not normally used; the skipper uses the shift and throttle
controls to control the vessels actions.
A vessel's stern may be pushed to one side or the other
by moving ahead or reversing with just one propeller. A
bit of headway or sternway does accompany the turning
motion. You can gain the most turning effect by energizing
one propeller forward and the other propeller in reverse.
One advantage of a twin-screw becomes evident when
you can turn the vessel in a circle just larger than the
vessel itself. As an example, to turn to starboard, the
rudders can be centered, while the port engine moves
forward and the starboard engine reverses. If you want
an even tighter turn, use the rudders.
Begin this type of turn with the engines at idle or in gear
at the same rpm ( revolutions per minute). For a starboard
turn, put the port shifter in forward and the starboard
shifter in reverse. When the vessel starts to turn, it may
begin to make headway. This relates to the boat and
propeller design. As a result, you may have to advance the
port throttle somewhat to increase the rpm of the reversing
starboard propeller.
When the port engine speed is increased somewhat, the
circle is bigger and the vessel makes headway. If the port
engine speed is decreased, the circle becomes larger, but
the vessel goes sternway as the reversing starboard
propeller pulls it around, stern to port.
BACKING DOWN
The skipper of a twin-screw vessel has a great advantage
over other boats because they can be steered with the
rudders when backing down. The benefits are less than
moving forward because the propellers thrust is directed
away from the rudders rather than at them.
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Chapter 6