Navy Shiphandler's Guide Flashcards
List your controllable and uncontrollable forces
Controllable
- Lines
- Anchors
- Tugs
- Engines
- Rudders
Uncontrollable
- Wind
- Current
- Bernoulli Principle
A ship using half its power can make up about 80% of its max speed. Why?
Resistance of the sea on the hull increases sharply with speed increase. The ship will accelerate to where the thrust generated will balance with the resistance created.
Which way do the screws rotate on a CG? What effects does that have for MOB? Is this normal for twin screw ships?
CGs turn inboard. It pushes things away from the ship when they approach the screws from the surface. Most ships rotate outboard.
How does a rudder work to turn the ship? Assume a RIGHT turn.
- Moves the stern of the ship in the opposite direction of where the ship wants to turn.
- to turn right, the rudder swings right
- this creates a pressure differential on the rudder, with a higher pressure to STBD and reduced pressure to PORT
- the resulting force moves the stern to PORT
- creates a drift angle that creates a pressure on the port bow of the ship
-combination of pressure on the bow and stern cause the ship to turn to STBD.
Why is a rudder much less effective when backing?
The rudder works by absorbing and deflecting the proper wash. The wash is absent when backing.
As the rudder angle increases, the turning force ____ and drag ____.
TF–decreases
Drag–increases
Define tactical diameter
The lateral transfer a ship will travel when executing a 180 degree turn
Define advance
The forward transfer a ship will move when executing a 90 degree turn
Where is the pivot point if:
1) moving ahead
2) backing
3) DIW with tug pushing the pow
4) ship moving ahead with a spring line to the pier
5) ship going ahead against an anchor led through bow chock
1) 1/3 of the way toward aft
2) aft-most point
3) 2/3 of the way toward aft
4) close to the bow
5) directly on the bow
When would you utilize a spring line from the bow to the after-ish part of the pier for maneuvering? Which line would this be?
When you desire to push the stern from the pier for an underway without tugs. Line 2
What is the main factor that drives the placement of the pivot point?
It will move towards the resistance against the ship. Ship is moving forward–water is resisting the bow’s movement–pivot point moves forward.
What is the difference between an APU and a thruster?
APUs are train-able
Thrusters are stationary
How would you use an APU?
Oppose the APU to the ship’s engines, which would push the ship sideways into a slip
How would you use a bow thruster?
Used to control the direction of the bow balance this with an engine twist to push the ship sideways into a slip
How are lines numbered on the CRUDES?
1-6 from bow to aft ON THE SHIP
What are the names of the lines on the ship?
1) bow line
2) after bow spring line
3) fwd bow spring line
4) after quarter spring line
5) fwd quarter spring line
6) stern line
How effective are APUs and thrusters as the ship gains speed?
Less effective
On a CVN, what’s the rule of current and wind?
20 kts of wind = 1 kt of current
On a CRUDES, what’s the rule of current and wind?
30 kts of wind = 1 kt of current
What are 2 methods of understanding wind speed OFF SHIP when pulling into port?
Wind flags
Current ripples pushing past buoys
On a CRUDES, how will the ship tend when being pushed by a BEAM wind? Why?
Bow will be pushed away from the wind.
More surface area in the FWD half of the ship for wind to influence.
Which is easier to handle–a current coming from AHEAD of or AFT of the ship? Why?
Ahead. It increases the wash over the rudder, this increasing rudder effectiveness.
How do anchored ships tend to move when it’s windy?
Swing over to face INTO the wind
What is Bernoulli’s Principle? What does it mean?
It’s a conservation principle:
“The sum of the energy of velocity, the energy of pressure, and the potential energy of elevation remains constant.”
If you increase velocity of the fluid hitting your bow, it will create a decrease in pressure on the other side of the bow, which means your bow will tend towards an area of lower pressure.
Apply Bernoulli’s Principle to UNREP.
- Fluid speed increases when fluid is forced through a narrow/restricted area.
- The increased fluid speed therefore decreases fluid pressure
- This is called the VENTURI EFFECT.
- When your ship is next to an UNREP ship, the fluid between the ships increases speed as it travels from between the bows to between the sterns.
- This causes a length-wise decrease in pressure where the pressure between the bows of the ships remains greater than the pressure located at the sterns of both ships
- Overall, this causes a reduction of pressure along the inboard sides of both ships
- This causes the ships to want to get sucked towards each other (don’t forget water initial water pressure did not decrease along the outsides of the ships, which means it’s at a higher overall pressure on the outsides of the ships, which causes the ships to want to tend towards the direction between the two ships
How does the VENTURI EFFECT change when speed increases?
The effects increase.
How does the VENTURI EFFECT change when the ships move closer together?
Gets stronger (further reducing the area increases the speed which decreases pressure in between the ships even further)
You’re in shallow water. Is your rudder more or less effective?
Less
You’re still in shallow water. Why does SQUAT happen (BERNOULLI)?
Shallow water means you’ve restricted the area between the ground and your ship. Therefore if you increase the speed, the pressure will drop from its highest point at the bow to a low point at the stern. That causes your stern to sink.
What’s the difference between giving a STANDARD/FULL rudder order and a HARD rudder order? Why?
STANDARD/FULL are prefaced with a direction, and are said second. “LEFT Standard Rudder.”
HARD is stated first to ensure the Bridge Team understands the urgency and necessity of expedient action. “HARD LEFT Rudder!”
What should RPM be if you need to do an EMERGENCY increase in backing/ahead bell?
999
What is the equation for the Invisible Distance under the bow?
I = (B*D) / (A-B)
A = Height of Eye (where you are) B = Height of Bow D = Distance from Bridge to Bow I = Invisible Distance