Challenge: Captain's License Questions

[over40pirate]

And the answer is..............
Rudder hard over.
Only took me 1.5 hours scrolling thru the questions.

Here is a great site with more questions and answers than you want to see!
Thank God, I'm only taking a 200Ton test!
USCG General Deck Questions: Master's License (QUESTION)`

[GordMay]

Originally Posted by over40pirate

And the answer is..............
Rudder hard over.

Hard over - which way?
Why?

[speciald@ocens.]

Some of the "correct answers" in the CG exam are wrong. We were taught what the answers expected were even if they were the wrong answers when I took a course at the Mariners school 2 years ago.

[LtBrett]

I have a twin screw powerboat and can affirm that rudder hard over is the right answer. Propellers are more efficeint in forward than reverse. If you don't vector some of your prop wash to the side or throttle up a touch on the reversing engine, you will start gaining headway. Furthermore, your kick from the propwash against the rudder is not insignificant when it comes to making you turn faster. Here's a quick summary of maneuvering without way on:
left twist: stbd ahead, port back, rudder hard left
right twist: port ahead, stbd back, rudder hard right
crab right: port ahead, stbd back, rudder hard left
crab left: stbd ahead, port back, rudder hard right

The convention the cg uses when they say sunset to sunrise, they mean night. Sunrise to sunset means day.

Brett

[Ex-Calif]

Port engine forward. Starboard engine reverse. Rudder to starboard. Why not?

I have an issue with the "daylight" - There is no definition for daylight. There is a definition and published time for sunrise and sunset for every lattitude and date on the planet.

There is a defined time for lights - sunset to sunrise - would it not make sense to display day shapes when not displaying lights?

Caveat mariner - I don't know the answers...

[nigel1]

With an hour to spare between anchors this morning, tried an experiment in turning a twin screw boat through 180 degrees, once with rudders midships, and again with rudders hard over.
The boat is a 16000 hp anchor handling tug, twin screw variable pitch props, with twin becker high lift rudders.
Props are in Kort nozzles, so transverse thrust/prop walk has no effect
In each case the turn was made starting with the boat all stopped, and head to wind. Movement of the boat was observed on a Kongsberg K-POS dynamic positioning computer, with dual DGPS inputs, and a known accuray of within 0.5 meters. The vessels centre of roatation was used as reference point, and to keep things fair, the engine going ahead was limited to 30% prop pitch.
In the case of turning with rudders midships, the turn took 4 minutes, and the greatest rate of turn noted during the exercise was 50 degrees per minute.
In the second test with the rudders hard over, the turn was completed in 2 minutes, and the greatest rate of turn noted was 100 degrees per minute.
In both cases, the vessels centre of rotation stayed with 3 meters of the start position.
In the first case, 30% astern pitch was needed to prevent the vessel making headway, in the second case, 10% astern.
Using the rudders makes the turn quicker and cheaper.
So far as I know, as soon as the prop giving ahead thrust is used, it puts a flow of water over the rudder, and as soon as the stern of the boat starts to swing, that flow is increased.

[sigmasailor]

Originally Posted by nigel1

Using the rudders makes the turn quicker and cheaper.
So far as I know, as soon as the prop giving ahead thrust is used, it puts a flow of water over the rudder, and as soon as the stern of the boat starts to swing, that flow is increased.

The above works if the rudder is aft of the props.
I was on a (twin prop/rudder) cat where the rudder was in front of the prop. Backwash from the prop had little turning effect on the rudder. When we were playing around (we did not have the nice toys you have) we saw little difference but did note the rudder was pushed (with quite some force) to one side (depending where is already was and sometimes a big surprise) by the prop when reversing. After some trials I simply locked the wheel dead center and just used the props.
I guess there are more factors that the exam question has in mind.

[MarkJ]

Originally Posted by nigel1

.
The boat is a 16000 hp

Showoff!

Great info, and thanks for doing the experiment I hope it was kinda fun!

Next experiment: 100% thrust Full 360 in 5 seconds?


Mark

[nigel1]

Originally Posted by MarkJ

Showoff!

Mark

Being really extravagant, and using both bow thrusters, and both stern thrusters in addition to props and rudders can do 360 turn in about 1 minute, but I tend to get a bit giddy and then throw up, makes an awful mess on all the nice gadgets on the bridge.'
Tends to upset the cook as well as most of the galley ends up on the deck.

[Pelagic]

I really hate to burst the US mariners training bubble but I have dealt with a few US officers who seem to have focused on finding the quick answers rather than knowing the subject.

When it comes to COLREGS that means you know and “understand” them intimately.

Not just memorizing a number of vague multiple choice answers from a stock list of possible questions.

Understand the purpose, study the court cases of marine casualties where that rule was involved and remember the findings.

Example:

USCG Question:
When should navigational lights be turned on?

Your Answers: From Sunset to Sunrise

Wrong and Incomplete! .... Since this is the Challenge section…..


Can anyone tell me why?



(Hint … it is wrong in more than one way)

[Misiu]

Originally Posted by nigel1

Being really extravagant, and using both bow thrusters, and both stern thrusters in addition to props and rudders can do 360 turn in about 1 minute, but I tend to get a bit giddy and then throw up, makes an awful mess on all the nice gadgets on the bridge.'
Tends to upset the cook as well as most of the galley ends up on the deck.

Don't upset the cook

Nigel - thank you for the experiment and clarification. Very well described
Throwing up is the only part from your post I have experience with.
Glad I learned. I was in amidships group before...

[unbusted67]

Originally Posted by Pelagic

I really hate to burst the US mariners training bubble but I have dealt with a few US officers who seem to have focused on finding the quick answers rather than knowing the subject.

When it comes to COLREGS that means you know and “understand” them intimately.

Not just memorizing a number of vague multiple choice answers from a stock list of possible questions.

Understand the purpose, study the court cases of marine casualties where that rule was involved and remember the findings.

Example:

USCG Question:
When should navigational lights be turned on?

Your Answers: From Sunset to Sunrise

Wrong and Incomplete! .... Since this is the Challenge section…..


Can anyone tell me why?



(Hint … it is wrong in more than one way)

It is wrong because "(c) The lights prescribed by these Rules shall, if carried, also be exhibited from sunrise to sunset in restricted visibility and may be exhibited in all other circumstances when it is deemed necessary." and to answer your question more specifically: so people can see you when it is dark out.

[Lodesman]

I imagine the USCG probably has a "suggested" reading list from which they would get most of their questions. Obviously colregs for the rules questions, but likely one of the better known ship handling texts for the manoeuvring questions, such as "Ship Handling" by D.J. House or Crenshaw's "Naval Shiphandling". The turning at rest question obviously applies to the typical commercial ship twin-screw arrangement with rudder(s) aft of the screws; it won't necessarily work for every boat/ship.

[Tempest245]

Originally Posted by Ex-Calif

Port engine forward. Starboard engine reverse. Rudder to starboard. Why not?

I have an issue with the "daylight" - There is no definition for daylight. There is a definition and published time for sunrise and sunset for every lattitude and date on the planet.

There is a defined time for lights - sunset to sunrise - would it not make sense to display day shapes when not displaying lights?

Caveat mariner - I don't know the answers...

I believe, Daylight means in the light of day.. or better... with good visibility.

Since lights must be turned on in time of poor visibility...and poor visibility can occur anytime after the sun has risen and before it has set....daylight is appropriate terminology for describing when shapes should be displayed.

I suppose you can display shapes from sunrise to sunset..but you better turn your lights on when visibility is poor. Shapes alone won't cut it.

[HaroldRamis4329]

I know this is late to comment, but Lodestone is correct..........how the vessel handles varies greatly with design. If you put right full rudder on an LCM-8, port screw in reverse, starboard screw forward, a mikeboat will "walk" to the left. All vessels will not do that.