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ContinuousWave: Small Boat Electrical
Big Boat Electronics
|Author||Topic: Big Boat Electronics|
posted 03-24-2012 11:21 AM ET (US)
Recently we spent a week aboard the 600-foot motor-sailing yacht WINDSURF. MSY WINDSURF is registered in the Bahamas, and the master has a policy of an open bridge when at sea. (Regulations restrict bridge access when not underway or when maneuvering in a port.) MSY WINDSURF was typically underway and at sea in the evening, and we took advantage of the open bridge policy to visit a few times after dinner. It was very interesting to see the electronics on the bridge of a modern vessel. And also to see the use of traditional methods of navigation and plotting.
All ship positions, course lines, line-of-position observations, and other information of navigation were plotted in pencil on paper charts, using the official charts of the nation in whose waters we were navigating. The paper charts were also annotated with ranges showing distance off various islands in order to clearly show areas in which discharge into the sea of certain categories of material would be prohibited. It was surprising to see that the traditional paper chart and pencil course line was being maintained in this age of electronic navigation.
To assist the navigator there were two very large electronic chart display and information system (ECDIS) units. These ECDIS units had mammoth LCD displays, probably about 24-inch or more. The ECDIS showed the ship position in the center of the display with vector graphic chart cartography. In addition, the position of other vessels obtained by AIS transmission was also shown. On the right hand side of the display a great deal of information was displayed in a long table. In addition to the current course over ground, vessel heading, and speed over ground, the ECDIS showed the estimated time of arrival at the destination, and the minimum speed needed to reach the destination at the planned time of arrival.
MSY WINDSURF is a sailing vessel, and we had plenty of breeze during our trip. It was typical for WINDSURF to be making 10-knots under sail. However, a few evenings the breeze was light, and we would ghost along at 5 to 6-knots. The ECDIS would compute the speed needed to reach the destination on schedule. When the required speed began to climb to over 11-knots, the engines would be brought on-line to motor sail to permit the schedule to be maintained. Also, while sailing, the vessel heading and course over ground were often not aligned due to leeway from the sail propulsion.
It was quite fun to see the lights of another ship on the horizon, then go to the ECDIS to discover what ship it was from its transmitted AIS information. Of course, not every vessel has AIS.
The bridge also had two very large RADAR plan position indicator (PPI) displays. When underway at night these displays received a lot of attention. There were two different types of RADAR sets in use. One of them seemed to show weather phenomenon better than the other. We could see echo returns from a squall about ten miles away.
There was also a fathometer on the bridge. During my visits we were in deep water, and no bottom echoes were displayed. As the bridge would be closed during approaches to harbors, I never did see any bottom echo on the fathometer. I know that during one approach to an anchorage we had to transit a narrow channel with only about 30-feet depth in the center. The MSY WINDSURF draws about 17-feet, so I bet there were some eyes on the fathometer that afternoon. As one experienced mariner once told me, the fathometer is not really needed--they pay the captain to know how deep it is.
There was also a very elaborate control panel and annuciator panel that controlled the navigation lighting and showed the status of all the navigation lamps on the vessel. When under sail only, the main mast showed RED over GREEN all-round lights. (Cf.: http://www.navcen.uscg.gov/?pageName=nr_25c.) It was a quick way to for us to tell if we were motor-sailing. If the RED over GREEN was showing we were just on sail power.
The bridge crew were all very gracious and receptive to our visits and questions. To be able to get on the bridge added a great deal of fun to our cruise, and it gave me a chance to see modern big-boat electronics in action.
posted 03-24-2012 10:07 PM ET (US)
I find it interesting that the big boys keep a plot on a paper chart. Now I don't feel like I'm the only one paranoid about electronics.
posted 03-25-2012 08:59 AM ET (US)
The MSY WINDSURF also has a voyage data recorder (VDR), require nowadays by international regulations. The VDR includes a voice recorder that tries to capture and record all audio on the bridge, including I suppose the often silly questions of the passengers.
In many places in promotional and descriptive accounts, the sails of the MSY WINDSURF are described as being "computer operated." A large control panel on the bridge provided remote controls for the sails, but there was no computer control of them. The bridge crew unfurled the sails and set them as appropriate for the wind and course. The process was not under automatic control or supervised by any computer algorithm. I learned this when a fellow passenger remarked to the Master about the "computer-controlled sails." The master corrected her and explained that the sails were controlled by the bridge crew, not a computer.
I also got a one-on-one tour of the engine room from the Chief Engineer. This was quite fun, too. There are four Wartsila (Finnish) six-cylinder diesel engines that drive alternators. The alternators produce 440-VAC. Each diesel alternator can produce about 2.2-MW. When the ship is at anchor, typically only one diesel is run. The normal ship electrical load is about 1-MW. The Chief explained that is actually was a bit of a problem, as the 50-percent load was not particularly good for the diesel. The engine would tend to build up combustion chamber deposits at that load, if the normal marine heavy diesel fuel were used. The Chief said they run a lighter weight diesel, more like the grade you'd get for a diesel automobile engine, to keep the combustion chamber deposits from building up due to the chronic lighter load.
When the ship is underway under engine propulsion, a second diesel is run, and when the ship is maneuvering, a third is brought on-line so that there is plenty of reserve power. An electrically operated bow thruster is also likely to be used then, adding considerably more electrical load. A fourth diesel engine is typically not run, and is often undergoing maintenance. There is a rotation sequence used so that all four engines are run and the hours shared. As it happened when I was visiting, No. 4 was being worked on, and a very prominent red sign was hanging over its controls warning "DO NOT START."
The alternators provide power to two propulsion motors, which are constant-speed AC motors, each rated about 1.8-MW. Each propulsion motor drives a gear-reduction mechanism, which in turn drives a propeller shaft at a constant speed of 150-RPM. The propeller is a variable pitch design. When the bridge moves the engine controller, they are actually moving the propeller pitch. When the MSY WINDSURF is sailing, the propeller pitch is set to feather so as not to create drag. The propeller shafts have brakes to lock the shaft from windmilling in the water stream. This prevents the shaft turning at a low speed, which would create problems for the lubrication of the shaft bearings, and also from creating vibrations when sailing.
The engineering plant also makes fresh drinking water using a reverse-osmossis process. A small evaporator also makes a lower grade freshwater, called technical water, for ship use such as washing the decks.
By the way, the MSY WINDSURF does actually sail quite a bit. The sails were up and drawing about 88-percent of the time we were underway. We were under sail-only about 35-percent of the time underway. This data was relayed by the Master from his Chief Officer who provided the statistics. As the Master explained, we could sail more if we liked, but then our one-week cruise itenary might take three-weeks to sail. To keep to a schedule, they have to motor-sail at times. They usually motor-sail late at night when the passengers are asleep. There is a bonus to this, too. The MSY WINDSURF has stabilizers to reduce roll motion. The stabilizers work more effectively at higher boat speed. Motor-sailing at over 10-knots lets the stabilizers work better, giving the passengers a better night's sleep.
posted 03-25-2012 09:16 AM ET (US)
I forgot to mention the satellite feeds. We received HBO, CNN, and ESPN via satellite receivers. We were in Latitude 16-N to 18-N much of the time, and I think we were out of the main ESPN downlink footprint for the USA feed. We got a version of ESPN that essentially showed non-stop soccer games. No NHL hockey available.
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