should be 3.3, say, 3^1 / 4 inches (84 mm)
outboard. This assumes that the boat’s props
are out-turning as viewed from astern. (This
is the standard and usually the most efficient
configuration.) If by some chance your props
have the opposite rotation, then you would
locate the rudder stock inboard by the same
amount.
Pulling the Single-Screw
Prop Shaft
On a single-screw vessel, you can’t place the
rudders off center. If you did, steering
response would be different for port and star-
board helm. The solution here for a standard
balanced rudder is to install a hole in the
rudder. If properly located, it will allow the
mechanic simply to disconnect the rudder
linkage and rudder stops inside the boat and
pivot the rudder 90 degrees. If the hole has
been drilled in the rudder blade at the loca-
tion shown in Figure 12-21 (at the intersec-
tion of the extended prop-shaft centerline
and the rudder-stock centerline), then the
mechanic can draw the shaft out through the
hole. Naturally, the hole has to be larger than
the shaft, but not too large—that would cre-
ate drag and reduce steering efficiency. Tw o
to 2.5 times shaft diameter is a good compro-
mise for the shaft-pulling hole diameter.
Smaller gets to be too tight, and larger is just
a waste. Also, very steep shaft angles may
require a vertical oval slot.Chapter 12:Rudder-Stock Angle, Control, and Installation Considerations
Figure 12-20.
Twin-screw
rudder location
(viewed from
astern)Figure 12-21.
Single-screw
rudder hole