NEW PILOT CUTTER DESIGN: THE “ORC”

January 8th, 2008 by JCB
Posted in Articles, Coastlines, Technical and Training | 2 Comments »

This quarter’s feature on pilot gigs illustrates how a successful design can survive unchanged for generations. The modern pilot boat is a similar example since it is still possible to order a pilot cutter whose design is basically unchanged from the first high speed cutters introduced in the 1960’s.

It was therefore with interest that earlier this year I visited the Southampton workboat show to have a look at a radical new design of pilot boat which had been brought over to the show by the St. Nazaire pilots. Called “ORC” the craft are constructed by the Bernard shipyard at Locmiquelic, near Lorient in Brittany, France. The unique feature of this boat is the beak protruding from the hull above the water line. The idea behind the beak is to improve bad weather high speed capability. With a traditional bow form, as the boat encounters a large wave, the flare of the bow causes the bow to rise up and then when the boat drops off the back of the wave the bow slams into the next one. As well as being extremely uncomfortable for the occupants, this effect obviously has the potential to cause hull damage and consequently in rough conditions speed capability is seriously reduced which in turn results in a slow slog over the waves out to the pilot transfer area. The ORC beak acts as a form of wave piercing extension to the hull which, as it enters the front of a wave reduces the tendency for the bow to rise rapidly as a result of the bow flare. With the vertical movement of the bow stabilised, the fall off the back of the wave is lessened and the “angle of attack” into the front of the next wave is reduced and the process is repeated. The design has also enhanced sea keeping properties in following and cross seas. The boats are also designed to be self righting.

St. Nazaire pilots have been operating an ORC 180 since 2001 and the boat has dramatically enhanced bad weather performance over their traditional pilot boats. Pilot Michel Catho, who attended the show with the boat, informed me that they are usually able to maintain the boat’s design speed of 27 kts in sea conditions of force 6-7 and they can even maintain full speed through the larger waves / swells encountered at the sand bar on their approach channel. The Coxswain informed me that he had actually motored through a wave at speed and apart from the bow fendering being peeled back the boat suffered no damage.

Of equal importance for a pilot boat is how the boat handles whilst alongside a ship during the pilot transfer. The hydrodynamics of some modern pilot boat hull designs have resulted in their becoming “stuck” alongside a ship which has necessitated requesting slower ships speeds during pilot transfer. In bad weather this increases the likelihood of heavy rolling developing whilst making a lee. Michel advises me that these hulls are very stable alongside and they normally transfer at speeds of around 10 – 12 kts. In good weather they have safely undertaken transfers at 15 kts which means that the majority of ships don’t have to reduce speed whilst boarding / landing their pilot.

General information

The ORC hull is available in lengths from 10 – 25 metres and the interior layout can be tailored to individual user needs. The pilots of six French ports are now using ORC boats and this year the Norwegian pilots at Hammerfest took delivery of an ORC 140. The ORC hull is not just used for pilot boats. The French lifeboat Service the Societe Nationale de Sauvetage en Mer (SNSM) are now operating 22 such craft around the French coast and the design is becoming increasingly popular in France with many other small craft sectors.

www.bernard-naval.com/

To view a video clip of the cutter in action in rough weather click here. Password ORC18