Today we opened up a Flickr account.

We will try to upload some nice shots of ships passing by just meters away.

Our first pictures :

This could have ended so much worse.

International Marine Consultancy will save you a lot of time and money. If you need to have anything towed from or to anywhere in the world, there’s no longer any need to contact various contractors and do a lot of planning to get the job done. All you have to to is get in touch with IMC and let us work out the details for you.

International Marine Consultancy:

- supervises your project from A to Z, from contracting to crewing, from appointing agents to customs clearance
- is totally independent from any tug operator
- is very well connected to tug owners around the globe
- provides cost-effective solutions you didn’t think of
- always has a pro-active mentality, thinking ahead, together with you

Please feel free to contact us for any towage inquiry you might have.

Next up in our Propulsion series are the Azimuth Thrusters.

© Siemens AG

Azimuth thrusters are electric podded drive systems, which are mounted on a 360 degree rotating shaft under the ship. There is no rudder required in an azimuth system and hence, the underwater dynamics are improved which not only increases manoeuvrability, but azimuth thrusters also include the advantages of combined engine systems.

Tugs and supply boats, where precise directional control is required, often in tight spots, were the first “proper” ships that were fitted with azimuthing systems, where the propeller could be rotated around a 360 degree horizontal axis. This required some quite complex shafting and bearings with the propulsion shaft having to be aligned from a horizontal axis, to a vertical axis (around which the unit rotates) to the horizontal axis of the propeller itself.

The principle of what might be called “dynamic” positioning, with total control of a vessel’s movements, independent of external assistance from tugs is very attractive to cruise ship operators, and thus has emerged the development of the “podded” propulsion unit, which are very large azimuthing propulsion systems in which the whole propulsive power of big ships can be fully directional. Cruise ships often have to get into confined ports where tug assistance is not necessary, or even lay off a port where the water is too deep to anchor. The total manoeuvrability which is available from azimuthing “pods” is hugely appreciated. Moreover, the giant rudders and separate steering gears which would normally be fitted to such ships are no longer necessary, and it may be possible to dispense with some of the lateral thrusters which would be required for a conventionally propelled cruise ship.

There are two major variants, based on the location of the motor:

1. Mechanical transmission, where the motor is inside the ship and power gets transmitted to the propeller via bevel gears. The motor may be either a directly mechanically connected diesel engine, or an electrical motor getting its power from generators run by an electricity producing engines (usually diesel engines) elsewhere in the ship.

2. Electrical transmission, where the electrical motor is in the pod itself, directly connected to the propeller without gearboxes. The energy used to drive the motor in the pod is produced by machinery inside the vessel, usually by diesel engines or gas turbines which drive electric generators, in a system comparable to that used by diesel-electric locomotives. Invented in 1955 by Mr. F.W. Pleuger and Mr. Friedrich Busmann (Pleuger Unterwasserpumpen GmbH), ABB Azipod was the first product using this technology.

The Azipod propulsion system improves the steering behaviour. It can be built for pushing or pulling operation, and low or high speeds. When Azipod units are installed in the stern and bow, the ship can do sideways manoeuvres (or azimuthing) the ship can go astern by changing the direction of rotation of the propeller or by rotating the azimuth angle 360 degrees. Additional manoeuvrability may be attained by changing the azimuth elevation. Using azimuth thrusters, the crash stop distance can be halved compared to conventional propeller systems.

sources: Ship Technology, BIMCO

With natural oil and gas reserves dwindling, renewable alternative energy sources are in high demand. Wind power is one of the most cost-competitive renewables today.

The Q7 wind farm, a 120 MW offshore wind park, comprising 60 Vestas V-80 wind turbine generators, is being built about 23 kilometres offshore from IJmuiden, in block Q7 of the Dutch Continental Shelf. The sixty wind turbines, each with a capacity of 2 Megawatts, will be placed at a depth of 19 - 24 metres. Q7 is located furthest offshore and placed in the deepest water.

The project, owned and developed by group companies of ENECO Holding N.V. (“ENECO”), Econcern BV (“Econcern”) and Energy Investment Holdings (“EIH”), is built by Vestas Wind Systems A/S (“Vestas”) and Van Oord Dredging and Marine Contractors B.V (“Van Oord”) under separate construction contracts, and will initially be operated by Vestas Offshore, an affiliate of Vestas, under a 5-year warranty, operations and maintenance contract. Construction started this summer and is expected to be completed by 1 March 2008, for a total investment cost of EUR 383 million. It will sell electricity to ENECO Energy Trade B.V, an affiliate of ENECO and will benefit from the Dutch regime supporting investments in renewable energy projects in the Netherlands. It will produce approximately 400 GWh per year, enough to supply 125,000 households, and avoid the emission of 225,000 tons of carbon.

IMC can deliver a diverse marine spread required for offshore wind farm projects, including (crane) barges, tugs and crew tenders.

Below you will find a small photo impression of the project.

Pictures © Arie Ros

In our Propulsion- series we now discuss a second system, Voith-Schneider.

The Voith-Schneider propeller is a specialized marine propulsion system. It is highly maneuverable, being able to change the direction of its thrust almost instantaneously.

Over 80 years ago this ship’s propulsion system, the only one of its kind in the world was developed by Voith from an idea by the Austrian engineer Ernst Schneider. It allows thrust of any magnitude to be generated in any direction quickly, precisely and in a continuously variable manner. It combines propulsion and steering in a single unit.

From a circular plate, rotating around a vertical axis, a circular array of vertical blades (in the shape of hydrofoils) protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal gear changes the angle of attack of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, very similar to the collective pitch control and cyclic in a helicopter.

© H.G. Hogeboom

Unlike a Z-drive (where a conventional propeller is tilted on a vertical rudder axis) changing the direction of thrust with a Voith-Schneider drive merely requires changing the pattern of orientation of the vertical blades. In a marine situation this provides for a drive which can be directed in any direction and thus does away with the need for a rudder. It is highly efficient and provides for an almost instantaneous change of direction. These drives are becoming increasingly common in work boats such as fireboats and tugboats where extreme manoeuverability is a very useful characteristic.

Z-drives (and Kort nozzles) have both advantages and disadvantages when compared to cycloidal drives. The Z-drive is less efficient and slower to maneuver, but is likely to be significantly cheaper in both the long and short term. A choice is made on the basis of perceived performance requirements. Also the blades of the drive protrude from the bottom of the hull making shallow water operation a problem.

A low accoustic signature favors the device’s use in minesweepers.

sources: Voith, Answers.com

We intend to highlight some of the various propulsion systems frequently used on tugs. Today we start with the Kort nozzle.

The term “nozzle” is derived from the Middle English noselle, meaning “nose”. Interestingly, “nozzle” also remains in the English language as a slang term for “nose.”

The Kort nozzle is a shrouded, ducted propeller assembly for marine propulsion invented by Ludwig Kort. The hydrodynamic design of the shroud, which is shaped like a foil, offers advantages for certain conditions over bare propellers.

Kort nozzles or ducted propellers can be significantly more efficient than unducted propellers at low speeds, producing greater thrust in a smaller package. For the bollard pull it may produce as much as 50% greater thrust per unit power than a propeller without a duct. Tugboats are the most common application for Kort nozzles as highly loaded propellers on slow moving vessels benefit the most.

The additional shrouding adds drag, however, and Kort nozzles lose their advantage over propellers at about ten knots (18,52 km/h).

Kort nozzles may be fixed, with directional control coming from a rudder set in the water flow, or pivoting, where their flow controls the vessel’s steering

sources: Wikipedia, Everything 2, US Patent no. 2,139,594