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Old 31-05-2010, 18:09   #1
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Twin Screw Simulator

I just started a new job as a deckhand aboard an 80 ton twin screw tour boat. As part of my job I will be required to have the ability to get this boat on and off the dock safely in case the captain is unable to do so. My training is next weekend and I am a little nervous about it because I have 0 hours aboard a twin screw boat and 0 hours docking anything over 15 tons, does anyone know of a twin screw simulation program? Ship sim doesn't seem to want to boot up on my computer.
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Old 31-05-2010, 18:19   #2
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#1 SLOW IS PRO

#2 SPRINGING OFF IS SOMETIMES THE BEST WAY

#3 ASK THEM TO LET YOU MANEUVER THE BOAT IN AN OPEN AREA SO YOU CAN GET THE FEEL OF IT

#4 USE ENGINE ONLY....NO RUDDER.
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Old 31-05-2010, 18:48   #3
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Slow is GOOD!

There is a technique called "walking" a twin screw. Some boats do it better than others, depending on many factors such as weight, propeller type, rudder type, etc.

To leave the dock, the dock side engine is put in forward. The outside engine is put into reverse.
The wheel/stick is turned to make the boat turn into the dock. That causes the propeller wash over the rudder mover the stern of the boat away from the dock. The outside engine in reverse will "pull" the bow away from the dock. You have to adjust the power carefully on each to make it work together and that takes some practice. GO SLOW!!!

Congrats on the new job and vessel to learn!
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Old 31-05-2010, 19:20   #4
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When we leave the dock the captain usually puts thrust on the outboard engine nosing the bow into a piling forward of the boat. I believe he has the rudder turned so that the bow will go into the piling too. This kicks the stern out and we back away from the pilings. I had never heard of anyone doing this before but hey it definitely works. I don't think I will be getting the boat off of the dock just onto it.
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Old 31-05-2010, 19:40   #5
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I'm guessing the boat is about 75 feet long, 3-4 ft draft, diesel engines? Do you know the direction of the screws? And does it have 1 or 2 rudders? Assuming fixed pitch props, outward turning (when going forward port is CCW, stbd CW when viewed from astern) you can make use of assymetric thrust and prop-walk and the vessel will be quite handy.

In addition to Seaking's tip about walking - turning at rest: for a turn to stbd, go ahead on port engine, astern on stbd engine and rudder to stbd. If you start making headway, bump up the revs on stbd, or reduce the revs on port. Vice versa for port turn. The pivot point will be near the bow (or within 1/4 ship's length from the bow) when turning at rest - so steer the bow to where you want, stop, then move the stern left or right around the bow. In practice if going alongside slowly approach at a narrow angle (15 degrees); stop when the bow is a couple feet from the jetty, then a turn at rest moves the stern into the jetty. Portside approach, turn to stbd - the bow will stay planted and your bum will swing into the jetty. Just before you get parallel to the jetty, stop the swing by reversing the engines temporarily. Tie off and graciously accept the praise.
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Old 31-05-2010, 19:50   #6
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Sea King,

My boat works in the opposite direction that you describe. Dock side engine reverse and outside engine forward will move the stern off the dock. The bow thruster will push the bow to keep it parallel to the dock.

The best advice is to go slow. If you give it about one or two seconds of idle thrust, you will know for sure without creating a problem. You also have to consider wind and current conditions that may apply. Hopefully you are in a location where they are not significant.

My pivot point is about 45% back from the bow. The first thing to do if you can, while away from the dock is to put one ahead the other astern and observe where the pivot point is. This, and the direction of walking thrust is something that you need to know to dock it smoothly. They all have differences.
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Old 31-05-2010, 19:57   #7
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What do you mean "a turn at rest"? Are you talking about putting the props opposite eachother? The boat is 94 ft loa and is 9 ft draft. It has 2 servo rudders, fixed pitch inward turning props and is a diesel electric hybrid.
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Old 31-05-2010, 20:05   #8
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So yes I appreciate all of the verbal advice but I would like to try to practice on a sim. Does anyone know of one?
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Old 31-05-2010, 20:13   #9
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Turn at rest means with one forward the other reversed the boat rotates without going ahead or asterrn. Usually the forward prop is stronger than the reversed and you creep forward. So manuever with a little burst of both followed by, likely a bit of reverse to hold position with respect to the dock.

I think that you will get this sort of info specific to the particular boat, and you will find it easy to learn if you do it all slowly. That gives ample time to correct and fine tune the approach or departure.

Have fun. It is easier than it sounds. Especially if you understnd the go slow part.
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Old 31-05-2010, 20:14   #10
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What do you mean "a turn at rest"? Are you talking about putting the props opposite eachother?

Yes - so that the boat turns without headway or sternway.

Must have a narrow underwater profile to have a 9ft draft.
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Old 31-05-2010, 20:17   #11
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Some of the major training facilities have sims, but I they are for deep-sea sized vessels. I expect that your sim is your vessel at 80 tons.
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Old 31-05-2010, 23:20   #12
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Its a TOUR boat! Use every Horse Power it has! Ignore every other boat on the water and head for the dock FAST. Slam the bugger in astern HARD and crash into the dock to check for rot.


You'll be a natural.


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Old 01-06-2010, 07:08   #13
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Quote:
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Its a TOUR boat! Use every Horse Power it has! Ignore every other boat on the water and head for the dock FAST. Slam the bugger in astern HARD and crash into the dock to check for rot.


You'll be a natural.


Mark
Such a cheap shot.
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Old 02-06-2010, 16:34   #14
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I suspect that for a sim program to be of much value it would have to be tailoyed to that particular boat-there can be significant differences in handeling from boat to boat
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Old 02-06-2010, 19:02   #15
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I don't know about home PC sim's but in the large marine bridge simulators the individual characteristics of the ships are programmed in and are quite realistic. It's apparently fairly expensive to have a ship type programmed, but the sim does feature a few stock models that are representative of: a tug-boat, a deep-sea, a ferry, etc.

Someone mentioned asking for some manoeuvring practice out in open water - it's a very good idea. You can also toss in a life-ring to act as your 'dock'. Certainly good to build some appreciation of the boat's handling characteristics and gain some confidence.
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