GZV/ GRADE II - Enkhuizer Zeevaartschool · 2020. 2. 4. · Manoeuvring •2 Grade I Repetition...
Transcript of GZV/ GRADE II - Enkhuizer Zeevaartschool · 2020. 2. 4. · Manoeuvring •2 Grade I Repetition...
25-10-2016
1
MANOEUVRING GZV/ GRADE II
3 COURSE BLOCKS
• 1 Grade I Repetition Propellers, Rudders, Manoeuvring data, Watch keeping.
Grade II hydrodynamics, Twin Propellers, Configuration, Manoeuvring
• 2 Grade I Repetition Some manoeuvres with current, wind, anchor. Storm and shallow manoeuvres, Taking pilot, Entering Harbour
Grade II Towing at sea. Dangers of tug use in port
• 3 Grade I/ II Subjects still to discuss. Repetition Grade II subjects Exam preparation
25-10-2016
2
Hydro dynamics
Hydro dynamics is caused by fluids in motion. Here the fluid is water.
Our vessel itself, rudder and propeler are body’s under influence of this fluid in motion
Where noticable: • The behaviour of the vessel in making a turn
• Interaction during overtaking and passing another vessel
• Bankeffect
• Shallow water effect (Squat)
• Unexpected effect when using bowthruster or forward tug whilst making speed ahead
• The special shape of a rudder and a propellerblade
• Duct or Nozzle around the propeller
A1
A2
The amount of liquid passing a random cross section of a tube (river-waterflow) per time unit is constant
When the tube gets narrower, the velocity of the liquid will increase
In formula: A1 x v1 = A2 x v2
Continuity Law
v1
V2
25-10-2016
3
• ½mV2 + P1 = constant
• Which means that:
When the speed increases, the pressure in the (here)liquid will reduce When the speed decreases, the pressure in the (here)liquid increases
Bernoulli’s Law
Propellers
See book for the items:
• The Pitch
• Propeller speed
• Slip
• Suction/Pressure plane
• Right/Left handed
• Fixed/Variable
Right handed – fixed propeller
25-10-2016
4
Ship’s behaviour
• Fixed pitch
• Right handed (Rh) • Engine ahead
• Engine astern
• Left handed (Lh) • Engine ahead
• Engine astern
• Variable pitch
• Right handed engine ahead as fixed Rh pitch, engine astern as fixed Lh
• Left handed engine ahead as fixed Lh pitch, engine astern as fixed Rh
Explain the movement of the stern of a vessel equipped with a
Ship’s behaviour
CONCLUSIONS:
• The direction of the movement of the stern of the vessel is the turning direction (wheeling) of the propeller
• The wheeling effect with engine ahead is hardly noticeable, on astern however the influence is significantly
25-10-2016
5
α
Ve
(speed)
Vrpm
Lift force
Thrust
(stuwkracht)
Drag
(weerstand
Propeller and Bernoulli
• Engine full ahead • α = (optimal) angle of inflow • Lift perpendicular on inflow • Forward thrust
Water inflow
Cross section topblade RH propeller seen from above
-α
Ve
Vrpm
Lift
- Thrust
Drag
Stopping on the Lift Engine slow ahead
• Engine slow ahead, speed still high
• Negative inflow angle • Lift perpendicular on inflow • Gives a stern thrust
25-10-2016
6
-α
Ve
-Vrpm
Lift
- Thrust
Drag
Fixed RH propeller engine astern
• Engine half astern, speed still forward
• Negative inflow angle • Lift perpendicular on inflow • Stern thrust
-α
-
Ve
-
Vrpm
Lift
- Thrust
Drag
Propeller and Bernoulli
• Engine half astern, stern speed
• Negative inflow angle • Lift perpendicular on inflow • Stern thrust
25-10-2016
7
Type of propellers (also see book)
Type of Propeller - Azipod
25-10-2016
8
Type of Propeller - Propeller Duct
Type of Propeller - Water jet
25-10-2016
9
Type of propeller- Voith Schneider
Tugs and Ferries
Bow Thrusters
25-10-2016
10
Bow- and stern thrusters
Bow- and stern thrusters
• Bow- and stern thrusters can only be used at lower speeds. WHY?
• Moving backwards, the bow thruster is a great help in steering. Why?
• Your vessel is equipped with both stern thruster and bow thruster. While proceeding foreward to the berth, you like the bow to move to starboard. Which thruster do you use to achieve this movement?
25-10-2016
11
Bowthruster and steering torque
.
.
P
P
P= Pressure point Short and long arm of a couple
RUDDERS Workings
• Effectively wake bent
• Minimal drag = small rudder angles, achieved by a wing shaped profile giving a Lift force
vertical foil
25-10-2016
12
Rudder types – Spade rudder
Rudder types – Flap rudder
25-10-2016
13
Rudders - Mariner Semi Balance Rudder
Upper part: Wing Profile (compare with
Oertz rudder)
Lower part: Balance
Rudders – Fishtail Rudder
25-10-2016
14
Rudder and forces
• What movements makes a vessel after giving starboard rudder
• Leaning shortly over to starboard
• Turns to starboard
• Tranverse movement to port (kick)
• Leaning to port during turn
• Loss of speed
• Explain with the book these movements of the ship
Manoeuvring data
• Turning circle difference deep and shallow waters !
• Stopping distance in the formular: mv2 !
compare with advance turning circle !
• Speed tests • MOB manoeuvres tests Williamson turn test on bridge
• Zig zag tests For checking course stability
25-10-2016
15
Turning circles – stopping distance
Know the expressions. Explain why diameter turning circle larger in shallow water. Explain speed reduction. Why speed reduction less in shallow water? And so on
25-10-2016
16
Speed reduction
Crash Stop
Crash stop vessel Full ahead-full astern Speed 12 knots Q: In how many minutes stopped? (7½ mins) Q: In what distance? (1100 meter) Q:After how many minutes speed 4 knots? (4½ mins)
25-10-2016
17
Controlled stop with engine and low frequency rudder cycling (only effective on deep water)
stopped
By using the Stopping on the Lift principle(reduce revolutions of the propeller step by step) as well as speed reduction by the drag of the rudder and vessel. The final astern manoeuver should be given to stop the vessel and to turn the vessel into the original heading (depending left/right prop)
Chapter 4 Standing and handing over the Watch
25-10-2016
18
The watch
• Standing the watch is taking care of navigation and act when needed
• Warn the captain instantly upon any doubt as to safety
• The watches 0-4 middle watch
4-8 morning watch
8-12 forenoon watch
12-16 afternoon watch
16-20 evening watch
20-24 first watch
The watch
• Handing over the watch • be in time to consider the oncoming navigation
• Handling over: al relevant information as course(s), speed, drift, ships, lights, dangers, and so on
• Heading and course both given in figures 150 = one five zero • What’s the difference between heading and course
• REPEAT ALL and what does it means • Hard a starboard Starboard a bit Starboard a bit more
• Starboard 30 Ease to 20 Midships
• Steady Steady as she goes Course 3 4 5
25-10-2016
19
GRADE 2 TWIN SCREW
• Twin propellers (two screws) improve 1. operating reliability and 2. maneuverability.
• With twin props the shafts mostly are at equal distance from the center line. The further the shafts are away the easier the ship will turn
• The propellers can be inturning or outturning . Fixed or variable.
• Most vessels are equipped with outward rotating fixed propellers, or inward rotating variable propellers. WHY?
• The maneuverability is improved when the vessel is equipped with two rudders and a bow thruster
25-10-2016
20
Outturning fixed propellers - one rudder • Port propeller left handed
• Starboard propeller right handed • Turn over starboard with port engine
ahead and sb engine astern • Two momentums are effecting the
propeller: • One because of one propeller
reversing while the other one is still in forward gear
• The other one due to wheeling propeller effect.
• Both momentums together will increase the turning.
• With slow speed the rudder to starboard has none or little effect
25-10-2016
21
Inturning fixed one rudder • Port propeller right handed
• Starboard propeller left handed
• Turn over starboard with port engine ahead and sb engine astern
• Two momentums are effecting the propeller:
• One because of one propeller reversing while the other one is still in forward gear
• The other one due to wheeling propeller effect but now counteracting
• So both will oppose each other and therefore making turning more difficult or even impossible
Mooring and unmooring twin screw
• Fixed inturning
• Fixed outturning
• Variable pitch inturning
• Variable pitch outturning
• With • one or two rudders
• bowthruster or bow-and sternthruster
• bowsprit
• Non parallel propeller shafts
25-10-2016
22
Unmooring 2
conventional twin screw ship fixed-outturning
starboard port
right handed propeller
left handed propeller
25-10-2016
23
one propeller (sb) working ahead
one propeller (sb) working astern
wheel effect
25-10-2016
24
one propeller (sb) working astern, the other propeller (port) ahead
wheel effect
when the rudder force is also applied the vessel will rotate even faster
25-10-2016
25
Inward turning fixed pitch propellers
starboard port
right handed propeller
left handed propeller
Inward turning fixed pitch propellers one propeller (sb) working on astern
wheel effect
When the vessel has inward turning propellers the momentum between the two propellers is outweighed by the wheel effect
25-10-2016
26
Traverse with outward turning propellers without bow thruster
Port engine/prop/rudder pushes stern to starboard Starboard engine /prop pulls the stern backwards and to port Only with little or no wind!!
Traverse outturning fixed props with the aid of a bowthruster
25-10-2016
27
2 x Traverse inturning fixed props with the aid of a bowthruster