Rate of Turn in Risavika
Rate of Turn
Technique
Rate of Turn in Risavika
Rate of Turn
Technique
Rate of Turn in Risavika
STCW 95
Rate of Turn in Risavika
The perfect ROT
The objectives:
Know how to
estimate the ROT
When to execute the
“wheel over” in order
to follow the planned
track
Control the ROT
according to the
speed
Control the speed for
port entry
A perfect ROT
turn
Rate of Turn in Risavika
The formula:
The circle is: 2r
ROT 360
o
/
2r*60/V =
6
o
*V/ 2r = 3V/ r since
3,14..
2r
r
V
ROT = ----
r
Time to sail 360
o
:
2r * 60
(to get the answer in minutes)
/
V
(velocity
)
ROT= Velocity/Radius or
V/R
Rate of Turn in Risavika
2r
r
V
ROT = ----
r
Let’s say the decided radius
is 0,3 n.m., and the speed is
8 knots
0,3 1/3 instead of 8/0,3
ROT = 8: 1/3 = 3*8 =
24
o
/min
The ROT at radius;
(0.5) ½ = 2*V
(0.3)
1
/
3
= 3*V
(0.25)¼ = 4*V
and so on
Some
simplifying:
r 0,5 = 1/2
r 0,3 1/3
r 0,25 = 1/4
r 0,2 = 1/5
Rate of Turn in Risavika
How to plan?
Tools?
Rate of Turn in Risavika
357
o
1/
2
n.
m
.
Parallel transfer the
courses
12
6
o
r =
1/2
1/2
n.m.
The question is when to put the
wheel over, and how to perform
the turn?
Pu
t
th
e
di
vi
de
rs
he
re
Map of area
Rate of Turn in Risavika
3
5
7
o
12
6
o
r =
1/2
As a rule of thumb :
Wheel over, 1 ships
length before the
pivot point should
leave the course.
Speed 10 knots,
ROT = 2 * 10 = 20
o
/min
As the speed drops; keep the ROT =
2 * V
Set priority:
1
Use rudder to
obtain decided ROT
within the
time of
sailing one ship
length
2
Adjust ROT
according
to the drop
of speed
a) by adjusting the
rudder-angle, or
b) in order to decrease
the speed faster,
reduce the effect on
the propeller and
adjust ROT with
the rudder
How to
sail?
Position to leave
357
o
Rate of Turn in Risavika
Execute the ROT according to the
plan
Rate of Turn in Risavika
Briefing Completed
Any Questions?