MT Mastera, image courtesy NESTE OIL, click for larger image

Concept and Background

- by Lloyd’s Register’s Robert Hindley and Robert Tustin:

Bow propellers have been installed on ships operating in ice since the 1880s with the following practical effects observed:

• Encourages the ice to break ahead of the ship’s bow
• Ability of propeller to further break-up ice into smaller pieces
• Washing of ice pieces away from the ship’s hull
• Improved maneuverability of the ship in the ice
• Assistance for freeing of the ship in trapped conditions

The practical effects of bow propellers in ice can also be achieved with podded propulsion units, or azimuthing thrusters which, when located at the stern, can be rotated to pull the ship ‘stern first’ with the additional benefits of directional thrust for maneuvering in ice and flushing of ridges.

Notice the transom clears iceline, a stern-facing pilothouse, the laterally located stacks, and the fine stern entry on MT Mastera. Image courtesy NESTE OIL, click for larger image

Ice interaction when operating stern first, courtesy Robert Hindley and Robert Tustin, Lloyd's Register

Ice interaction with propeller and hull operating stern first 

Beneficial effects of stern first operation from propeller and hull ice interactions are shown above and described below:

• Ice sheet bending and breaking – the water flow into the pulling propeller causes a pressure drop under the ice sheet ahead of the stern; which reduces buoyant up thrust on the ice sheet and promotes ice breaking by bending.
• Flushing of ice ridges – by azimuthing the pod adjacent to the keel of an ice ridge the variable flow of water promotes the erosion, or flushing, of the ice ridge keel.
• Lower frictional resistance in ice – with the propeller pulling, the water flow from the propeller washes along the length of the hull. The water flow reduces the friction between the hull and the ice by lubrication.

You may wonder, so does this present a curious rules of the road situation while at night?

Not to worry, “Stern First Ice Class Ships” will have mast head, side, and stern lights for both bow first and stern first operations.

Image courtesy NESTE OIL

Lloyd’s Register announced today that the first dedicated set of rules for stern-first ice-class ships has just been published, answering the demand for technical support as industry continues to explore the potential of polar transportation routes and the new energy reserves in the far north.

“These practical rules are answering a growing demand in the market and include the use of standard operational scenarios to provide designers with a basis for prescriptive rule applications that have been validated with designers and operators of these specialist ships,” said Robert Tustin, Lloyd’s Register’s Technical Manager for New Construction in Asia.

Lloyd’s Register has had a long involvement in the development of this class of ships. Mastera and Tempera – two 106,000 dwt “double-acting” tankers owned by Neste — were built to its class in 2002 and 2003 at Sumitomo’s yard in Japan. The ships were deployed to the Baltic, where they often operate stern first in heavy ice conditions, independent from icebreakers.

Other tankers, such as Sovcomflot’s Mikhael Ulyanov and Kiril Lavrov, were designed and built for operating stern first in ice in the Arctic. These ships, dual classed by Lloyd’s Register and the Russian Maritime Register of Shipping, were designed to eventually shuttle crude from the Prirazlomnoye platform in the Pechora Sea to a floating storage and offloading unit moored off Murmansk.

The development of Lloyd’s Register’s new rules were supported and validated by leading ice-class tanker designers, key regulators and operators.

The interpretation of regulatory and other rule requirements — and validation of strength levels for the hull and propulsion units — were confirmed by a review of the current fleet of double-acting ships, ensuring that practical experience supported the rules’ development.

They offer the following key interpretations:

§         The ship is considered as a bow-first and stern-first vessel for application of ice-class rule requirements for hull and machinery
§         It is also considered as a stern-first ship for the application of navigation-related rules and regulations
§         In other cases, the rule applies to bow-first ships only

The rules also include a framework for alternative-load scenarios when unusual operations are envisaged, as well as interpretations of international regulations and classification rules based upon industry precedents, said Tustin.

Photographer Scott Barnhill and I were delivering S/Y Downtime back from Block Island and the Chemical Pioneer was in the process of dropping off their pilot as we were approaching Beavertail Light at the mouth of Narragansett Bay.  We were looking as if we would pass them port-to-port, but after they dropped the pilot off, they turned  sharply to port and were crawling along at a couple knots of speed.  It was now a crossing situation.

There was deep water all around and from my perspective, it appeared we were the stand-on vessel.

I radioed the ship to clarify their intentions and to see how they held us for a CPA.  The english-speaking (quite likely American) mate on watch quickly responded and said that they were about to resume their outbound voyage and asked that we alter course and come down their starboard side.

Roger that.

It was a no-brainer situation, and taking their stern was the obvious choice, BUT, I knew that if I altered course to port without communicating that with the Chemical Pioneer, I would have been in violation of Rule 17(c) of COLREGS, and most certainly taken a severe beating from the gCaptain readership.

So, any comments from the peanut gallery?

by Captain John Denham

A frequent situation popping up, expectedly in many areas in Asia and popular fishing grounds is to find oneself approaching a multitude of small boats and maybe even a steamer or two. I routinely encountered a similar situation when entering from the Golden Gate on weekends into San Francisco Bay: a mass of white sails and some patches of blue water. Taiwan, Korea, Japan, France and England all have at least one such congested night mare.

As you know, the steering and sailing rules apply to you and only one other vessel at a time. It is perplexing because most of us are faced with a common problem; make the ETA. The courts have proclaimed: No vessel has the right of way through another vessel; therefore that eliminates an option. The person directing the navigation of the vessel is faced with many situations and only one solution for each problem. Therefore one must have a plan; a survival plan. The most important element in developing the plan is to determine who is the executor? My recommendation is, the Captain. To delegate, or assist, supervise or advise another is to further complicate a difficult situation. As captain I do not want to see how Jim or Harry will resolve a situation, I want it safely managed and with as little confusion as possible. Training juniors in such cases is best done by them watching and learning, and if perchance one errs, well, they may be a friendly witness.

Radar is useful in determining the path of least opposition and can also provide useful information as to the wind effect and sea conditions (watch the sea return). I would not attempt to maneuver with an opponent using radar information alone. An approaching vessel’s maneuvers may not be indicated on radar until well after his green light has turned to red. A proper ship handler will have knowledge of his vessel’s maneuvering characteristics and engine performance, i.e., at what speed does one lose steering capability? How long does it take to go from ahead RPM to astern RPM?

My plan is:

1. Captain will have the conn

2. The engine(s) are prepared to maneuver

(a) understand the operating procedures for obtaining emergency orders and how to stop propeller rotation.

3. A proper lookout is posted where he can best see, hear and report and has been instructed.

4. Communications (lookout reports, phones and radio) will be handled by another officer.

5. Illumination is available

6. BRM is informed and involved.

When towing, or in large ships one must consider the entire length (LOA) and be aware that any risk of collision (steady bearing and decreasing range) applies to the entire length of the vessel and or flotilla.

I have observed some experienced ship handlers reach for the ship’s whistle and irritatingly sound the danger signal as a warning (Lookout you dumb S.O.B.), whereas Rule 34(d) implies “failure to understand the intentions or actions of others, or is in doubt.” Nothing else. The courts have many times found: if one is in doubt, proceeding is not an option. However there is also support for: to do nothing displays unskillfulness. Therefore my practice was to sound a long blast on the whistle to attract the other’s attention and thereafter if needed, as advised by an old river pilot, “Sir, I suggest you back your engine smartly.”

Timely arrivals are “job keepers” and managers love old “On Time Joe” Also, pilots can not make up two hours in the bar channel, and, maritime lawyers love Rule 6, specially the congressional language in Senate Report 96- 979: ” it means that speed in any condition is intimately related to the immediate circumstances at hand.” And, “vessels are to proceed at a safe speed at all times.” The inference and language relates to visibility but the law as argued and accepted includes wakes. The courts have found that speed must be safe at all times under all conditions for everyone, which includes that 32 foot yawl, safely moored near Rincon Point that you passed 20 minutes ago 15knots.

Captain John Denham is a veteran of 66 years maritime experience in seamanship, ship handling, navigation, piloting, and education. he is also author of The Assistant and DD 891 .