At first glance the Nautical Slide Rule is simply a tool used to solve speed-time-distance problems. The real power of the tool though, is hidden, consider this: (from Hutchins (PDF))
"At this end of the technological spectrum at least, the computational power of the system composed of person and technology is not determined primarily by the information-processing capacity internal to the technological device, but by the way the technology exploits the cognitive resources of the task performer."
"Cognitive resources of the task performer" - that's the key. In practical terms, when I arrive on the bridge at 3 a.m. prior to port arrival I check the speed required before I have that first cup of coffee, cognitive resources are sometimes short of what is required to reliably solve the problem. Using the slide rule gives me confidence that I fully understand the situation in just seconds. I can hold the solution in my hand and by moving the dials slightly I can literally get the "feel" of the problem and solution. Using the slide rule has been compared to the practice of rearranging scrabble tiles to search for words.
The full power of the nautical slide rule becomes more apparent when put to use.
-The solution found can be quickly rechecked in a glance as opposed to having to repeat the operation as is the case with a calculator.
-In the case the ship's speed may be within a range, for example when "loading up", (slowly increasing speed) the range of solutions can be quickly seen by moving the dial over that range.
-The solution is in the same form as it will be used, distance on the dial is related to distance on a clock or the distance on the chart itself
- In the case where the solution is changing, for example if speed required is 12 knots but the ship is doing 13 knots, the rate of change of the solution can be sensed by resolving the problem, which can be done in just seconds.
- The precision of the solution is consistent with the precision of the inputs
- Using the slide rule significantly simplifies the problem and reduces the chance of error. In the words of a scientist (From Hutchins):
" The navigation tools do not improve cognitive abilities but simply make them easier and less prone to error. They map the problem into a domain where the solution is more readily apparent.",
Risk Ready Reckoner from Bob Couttie's Marine Accident Casebook
The Document above can be downloaded as a DOC file here -Bob Couttie has it as a PDF at his site (next link)
Update below:
Getting mariners to use yet another check list can be a tough sell. The Risk Ready Reckoner recommended by Bob Couttie however could literally be a life saver.
Just because there are safety procedures in your ship’s safety management system and various bits of bumf aboard doesn’t mean that you can’t develop your own safety system, one that belongs to you and which you use. Say hello to the Risk Ready Reckoner.
Bob also has an example of a hidden risk at Engineer Scalded - Risk not Mapped. The risk in this case was a pipe to an open tank that was plugged and unexpectedly filled with steam. It would have been difficult to uncover the risk in this case with a simple risk checklist, perhaps only previous experience would have uncovered this hidden threat.
There are some more sophisticated risk assessment tools available at this site: Step Change in Safety - A UK gas and oil site. This site includes the Task Risk Assessment Check list which is considerable longer then but more comprehensive then the Risk Ready Reckoner. The Task Risk Assessment Guide also at that site, is even more involved but I think it would be worthwhile going over with the senior officers. It might increase appreciation for risk assessment.
A captain I once sailed with had a term for mariners who felt they were too good to use checklist but often used unsafe practices. He would say that they were "so good they're brain dead".
K.C.
UPDATE:
In comments, Bob Couttie has pointed out that the Risk Ready Reckoner is aimed at all crew members, not just senior staff I had missed this and is an important point. From the Marine Accident Case Book. Read Make 2009 a Year of Safety Ownership
2009 should be SOS Year: Seafarer Ownership of Safety Year, a year in which active and positive efforts are made to give seafarers a sense of ownership regarding their own safety, that of their crewmates and their vessel.
Back in April I put up a post "Normal Accidents" - I am getting ready to go back to work and last night I was as Amazon.com buying some books for the trip. One of the books I bought is about HROs - "Managing the Unexpected: Resilient Performance in an Age of Uncertainty" - Review here ,
Some mariners have not yet embraced Bridge Resource Management - I've heard the arguments against it -my answer - go tell Captain Sully.
Casco Bay Boaters Blog has an interesting post - GPS Not the Answer .. Most mates know not to rely upon GPS alone. On the other hand I sailed with a captain who forbid the use of the GPS while in confined waters, I don't think that is right either.
My view is, there is no navigation situation where I would completely abandon the use of the GPS, with the caveat that I would never rely upon it entirely.
In the open sea we use GPS but verify the position with a comparison to the DR. At the pier on the other hand, if we want to know if we are still alongside, we go out on the wing and have a look. In between, on the transit from the open sea to the pier, the role played by the GPS shifts from being the primary method (with verification by other means) to becoming a means to verify the position obtained using other methods. As we approach the coast, at some point we shift from the GPS as a primary source to the use of radar and other means but still continue to use the GPS to insure we have not made a gross error. Even in a narrow channel I may not completely stop using the GPS, for example when I see that I am being set by the wind or current, a glance at the GPS course over the ground (COG) will quickly verify what I am seeing visually
Even relying upon the GPS as a backup however can hinder the ability to see clues in the environment that can aid in spatial orientation. As I gain experience in an area it becomes easier and easier to orient myself with visual landmarks. With each transit of an area I try to decrease the amount of assistance required from the GPS and increase my familiarity with local landmarks
When the tanker Sirius Star was hijacked some in the media expressed surprise that a supertanker could be boarded by pirates using open boats. This picture shows however the height to be scaled is not all that far. It looks difficult but not impossible. A ladder equipped hooks at the top may have been used. There are likely a good number of people in Somalia who would be willing to give it a try for a share of three million dollars.
K.C.
UPDATE: Sekulich , in comments points out that this photo is somewhat misleading, I agree. I intended to illustrate that the freeboard of a loaded tanker is less then what people may think. Not shown is, for one, the powerful wash that comes off the prop of a ship at full sea speed. It is much more difficult to board a tanker at full speed in the open sea then at anchor on a calm day which is what the photo shows
Look out the window. That's my message to new third mates. More then that, gain experience in the interpretation of what you are seeing.
I honestly don't understand why almost all new third mates have such a strong preference for using the radar when the situation can be more easily understood visually.
In aviation new pilots must first learn to fly a plane using visual flight rules and then later gaining an instrument rating. New mates on the other hand seem bound and determined to navigate entirely by instruments. My message to them is the same one I gave the mate that night in Alaska - Look out the [expletive deleted] window.
They are generally considered to be unexpectedly high waves which in some instances come from a direction different from the predominant waves in the local are
The wave that came aboard was not much bigger then the ones previously encountered. An experienced mariner should not have been surprised to ship water in that sea. In fact the informed mariner should expect an occasional wave twice as high as stated in the forecast (for details, see below). So - no rogue in this case.
Here is another example of a boat being struck by an unexpected wave, in this case fishing vessel The Aleutian Ballard jogging in reported 40 kts seas and 60 kts winds in the Bering Sea - this clip is from Deadliest Catch:
In this case the wave that struck from the starboard does seem larger then the sea at the time and it apparently came from an unexpected direction. Was it a rogue? A case could be made that it was but it is not uncommon during heavy weather to encounter two separate swell systems. The boat may have been struck by a breaking wave from a second, larger, swell system.
An unexpected wave is not necessarily a rogue (as seen in the case of the yacht). This raises the question, what size waves should a mariner expect to encounter at any given time? The answer is, as stated above, we should expect an occasional wave twice as high as stated in the forecast.
From the OPC again:
The wave height most commonly observed and forecast is the significant wave height. This is defined as the average of the one third highest waves. The random nature of waves implies that individual waves can be substantially higher than the significant wave height. In fact, observations and theory show that the highest individual waves in a typical storm with typical duration to be approximately two times the significant wave height.
a forecast of 10-foot seas in open waters means a mariner should expect to encounter a wave spectrum with many waves between 6 and 10 feet along with a small percentage of waves up to 16 feet and possibly even as large as 20 feet!
So in a typical storm we can expect a wave approximately twice as high as the height used in the forecast. So what is a rogue?
A rogue wave estimated at 18.3 meters (60 feet) in the Gulf Stream off of Charleston, S.C. At the time, surface winds were light at 15 knots. The wave was moving away from the ship after crashing into it moments before this photo was captured. Photo from NOS
A common definition of a rogue is a wave that is more then twice the significant wave height this is the definition found in Wikipedia.
Digging a little deeper and looking at some other definitions of a rogue wave, the photo above comes from this National Ocean Service site. They define a rogue as follows:
Rogues, called 'extreme storm waves' by scientists, are those waves which are greater than twice the size of surrounding waves, are very unpredictable, and often come unexpectedly from directions other than prevailing wind and waves.
This makes the case for calling the wave that struck the Aleutian Ballard a rogue stronger. We don't know if the forecast included a large swell from that direction but in any case it is not possible to predict when a wave in the open sea will break.
The weather services intended audience for forecasts is the mariner. Scientist and engineers are interested in the phenomena of rogue waves as well. They create and use their own definitions. For example the book "Rogue Waves" By Michel Olagnon, Marc Prevosto differentiates between what they call classic extreme waves and rogue waves.
Classic extreme waves are rare members of a population of wave events defined by modeling the surface process as a piecewise stationary and homogeneous slightly non-Gaussian random field.
In other words classic extreme waves are rare waves that fit inside the forecast model.
Freak (rogue) waves are defined as:
A freak wave event is an event that represents an outlier (crest height, wave height, steepness or group of waves) when seen in view of the population of events generated by a piecewise stationary and homogeneous second order model of the surface model.
In other words waves that are not predicted by the model, an outlier.
This leaves us with the following:
1. The unexpected wave. - Waves that strike the uninformed and the unwary are often bigger then expected. These waves may be both common and easily explained.
2. Freak or rogue - These terms are defined in different ways. They are unexpected and sometime not understood.
3. Extreme wave - Sometimes used interchangeable with #2 but also may mean waves that are rare and while the may be unexpected, can be simply explained.
So, the unwary yacht was hit by an unexpected wave and the Aleutian Ballard - well, it got slammed by what mariners call "a big one".
I linked to captbbrucato just a couple of day ago (here). I though reading his blog was like having a cup of coffee with a tug captain. Now it's is time to have a beer and learn what a "Bell Ringer" is - at No Really, This is No S**t
This story is not new, but is very interesting : Read the excellent summary at the Monitor Not your average comedy. The vessel had to be taken into tow.
A LARGE car carrier was disabled by an inadvertent release of the ship’s fire-extinguishing equipment and was nearly wrecked on the Wolf Rock in the English Channel, a Marine Accident Investigation Branch report has concluded.
This is an interesting story for several reasons. CO2 was released into the cargo holds and engine room during the working day. This turned out to be a difficult emergency that does not fit into common emergency drill scenarios. Another interesting thing was the root cause was that procedures used were unclear.
One lesson learned is this: If unclear procedures are discovered during routine maintainance they should be corrected.
I got cold just looking at them. Here is a photo to look at till you warm back up.
The Resolute wood stove made by Vermont Casting Photo by K.C. .
I was at sea a couple of winters ago and I heard on the news that Northern New England was having a severe cold spell. I called my uncle from a phone booth on the pier at Hiroshima and asked him if he was cold. He lives in a big old farm house with a Queen Atlantic in the center of the kitchen. He said "Nope, it's nice and warm standing here by the stove chucking wood in."
Below is a photo showing the stack gas temp - red-lined at 480F.
Stack gas temp red-lined at 480 degrees F.
If we were towing we might take a couple of turns off. - Here at the house we don't back off till the cat has to move away from the stove.
