Dun Laoghaire arrival. © Gordon Hislip
Stena Line's first HSS, the Stena Explorer, entered service on the Holyhead - Dun Laoghaire service on 10 April 1996 when she sailed from the Irish port at 0653hrs under the command of Capt John Roberts. Her first day in service was greeted by perfect weather and some very busy crossings. Her second sailing from Dun Laoghaire saw 1,109 passengers and 223 cars loaded in little over 10 minutes.
The big boast of the HSS was her seakeeping qualities, her designers claiming that she would sail in seas of up to eight metres and still provide her passengers with a comfortable journey at full speed. For her delivery voyage from Finland to the UK Stena Line could not have wished for better weather conditions - NE Force 9-10 winds in the North Sea. She performed magnificently. indeed, on arrival at Holyhead on 21 February, a piece of unsecured timber which had been used as a fender was still in place resting on her transom! In service, her Maritime & Coastguard Agency Permit to Operate restricts her operation to waves of up to four metres significant.
Photo: Seen from the South Stack, the Stena Explorer speeds towards Dun Laoghaire on yet another crossing of the Irish Sea. © Capt Simon Mills.
The Stena Explorer, with a top speed of more than 40 knots, takes much of its technology from the world of aviation. The smaller of the two different types of gas turbines are used in the Swedish Airforce's fighter, attack and reconnaissance aircraft, the Saab Gripen, while the larger of the two types is used in the long-haul Boeing 747 aircraft. There are several reasons why Stena's designers elected to use aircraft engine type gas turbines as the power source for the new Stena HSS 1500. They produce cleaner exhaust fumes than conventional diesel engines, require less space, weigh less, have a high level of operational reliability and are virtually vibration-free. However, they are also incredibly thirsty engines, something which troubles the craft ten years on.
The General Electric manufactured gas turbines on the Stena Explorer were rebuilt for maritime use, with each of the two hulls containing two types, one large and one small. The larger develops approximately 30,000 horsepower at 3,600 RPM, while the smaller develops approximately 20,000 horsepower at 6,500 RPM. The maritime versions of the gas turbines are powered by a light diesel oil with a very low sulphur content. The gas turbines, including the power turbines, are completely encased in fire and soundproof containers, known as turbine modules. Each of the two hulls contains two turbine modules - one large, one small.
In narrow waters the HSS 1500 can be powered by the two smaller engine packages, giving a maximum speed of 25 knots. When the larger modules are in operation, the vessel has an approximate top speed of 32 knots, and when all four modules are operating at full power, the ferry's speed can exceed 40 knots.
Taken on an extremely clear
day in May 2004, the Stena Explorer with the
The four KaMeWa water jets, two in each aft section of the vessel, draw in water through inlets in the ferry's bottom. The impeller is located inside the units in a space sufficiently large for a fully grown man to stand upright.
Right at the back of the water jet units lie the massive steering and reversing drives. Each steering drive can be turned 30 degrees to starboard or port and thus steer the ferry in the desired direction. The HSS 1500 reverses by dropping massive scoops aft of the nozzles through which the water jets are angled diagonally downwards and forward.
A new docking technique to speed loading and unloading, as well as a system for storing supplies, was among the unique features of the Stena Explorer, enabling her to be turned around, re-stored and re-fuelled in just 30 minutes and if required. The linkspan for the HSS was a completely new design, which also includes a quick coupling with fuel, fresh water and waste water pipes.
When the HSS docks in Holyhead and Dun Laoghaire, she reverses in towards the linkspan. The reversing manoeuvre is made easier by the ferry being fitted with navigation equipment, which can determine the position of the ferry to within one metre, four TV cameras, and a bow thrust in each hull. Once the HSS has made contact with the linkspan's fenders, the quick couplings are connected on either side of the ferry's stern, pulling it automatically into the correct position so that gangways, drive-on ramps and quick couplings fit. The ferry's massive beam and a specially constructed aft fender, which prevents the ship from moving sideways - mean no additional moorings, such as ropes, are required. Once berthed, rapid loading and unloading is achieved by using the ferry's four stern doors. Thanks to the massive beam, cars, coaches and trucks turn around on board in a wide U-turn. Three of the doors are used simultaneously during loading. Two of them lead into the ferry's main loading deck, while the third leads cars up to an extra pontoon deck situated above the main deck, via a ramp. Three doors are also used during unloading as vehicles drive through the 180-degree curve on-board.
Foot passengers go on-board and ashore along two parallel glazed passenger gangways, located on either side of the linkspan, so avoiding stairs and other barriers.
Helping to keep docking time to a minimum is a container system for supplying the on-board restaurants and shop. Two containers are loaded on to a traverser running on rails on the outer roof of the ferry. The restaurant container is lowered through an outlet in the bow roof, whilst the container with the shop articles has its place in the stern. Both of the containers stay on board until stocks need replenishing.
Heavy cost of fuel
For her tenth year in operation Stena Line announced a revised timetable for the Stena Explorer. A decline in tourist volumes as a consequence of competition from low cost airlines and other ferry operators and, more importantly, very high fuel costs, which had doubled in just 18 months, combined to force Stena Line to take action. The new order was for two HSS round trips a day, year round from 25 September 2006 with the flexibility to increase trips of the Stena Explorer when needed. During the summer months a two-trip timetable operates on Monday - Thursday inclusive and a three round trip timetable on Friday, Saturday and Sundays.
The Stena Explorer overtakes the relief Stena Transporter off Holyhead, 4th October, 2007. © Mike Griffiths
As fuel costs soared to $147 for a barrel of crude, and the global economy went into freefall, a further reduction in service was announced in October 2008. With effect from 10th November, the ship's schedules fell to just one round trip per day, except for the Christmas and New Year holiday period when the vessel double tripped.
Swinging for the berth in Dun Laoghaire, 17th March 2009. © Gordon Hislip