Codling Lanby Transfer
Harold McClenahan explains how it was
done
EARLY IN September 1998 ILT Granuaile placed a
refurbished Lanby on the Codling Bank, off Co Wicklow, and removed
for overhaul and re-painting the dirty Lanby that had been there
for the previous two years. The previous month Granuaile had laid
new moorings and recovered the used mooring from the Lanby. Her
task was now to place the refurbished Lanby on station.
This is one of Granuaile's more involved routine operations. The size and the circular shape of a Lanby makes it necessary to take specific precautions when towing and manoeuvring it into position. While circular structures are generally stable when stationary, they are unpredictable and erratic when moving through the water. When one considers that the structure weighs over 85 tonnes it will be appreciated that good weather conditions are vital for Lanby operations.
On the day of this operation the wind was light and the sea state unusually calm. As the Codling station is in an area of strong tides it is important to commence work just before slack water.
Lanby mooring system comprising 220 metres of 44mm stud-link chain, connected to a 3 tonne sinker and a 4 tonne anchor resting on the sea bed. The total weight of the chain (excluding the sinker and anchor) is 91Ž4 tonnes. The anchor secures the mooring to the sea bed, while the sinker acts as a damper to minimise the pull of the mooring chain on the anchor. The recovery chain enables the mooring to be hauled on board the service vessel.
Towing the clean Lanby from Dun Laoghaire at 6 knots with two 5 inch polypropylene hawsers, Granuaile proceeded to the Codling station so as to arrive one hour before slack water, which was to be 12.30 pm.
The good conditions on this occasion meant Granuaile could secure both Lanbys alongside without causing damage to Granuaile, or to either of the Lanbys.
With both Lanbys secured alongside the ship the mooring chain was brought on board Granuaile by attaching a wire rope to the recovery chain which is connected to the Lanby's main mooring chain, and hauling it in. The end of the Lanby mooring was then secured to the deck, and disconnected from the dirty Lanby by the ship's carpenter. With enough mooring chain securely on board to allow sufficient slack, the end of the mooring chain was passed underneath the ship to the opposite side by means of a heavy-duty line.
So as to avoid the chain running out at high speed a series of light rope lashings was placed along the 50 metres of slack chain. As the weight came on each lashing the order to cut was given and control maintained. After what seemed an eternity, the end of the Lanby mooring showed above the water on the port side. The mooring was hauled in and secured to the deck, ready to be connected to the clean Lanby.
The connection of the main moorings to the Lanby tail was made using the age-old and proven head-up method. This entails heating the pin of a 44mm clenching shackle to a temperature that allows the metal to be beaten by sledge hammers and evenly spread across the shackle face. Carpenter Jim Corbin is the man for this job and he takes great care to ensure that the pin fits tightly.
After connecting the mooring chain to the clean Lanby, the Lanby's position was checked using the Global Position Fixing System and differential correction stations (dgps). When Captain McCabe was satisfied that the Lanby was on her correct station and the foredeck personnel were ready, the order to slip the moorings was given.
Before departing from station a team of Lighthouse Depot Technicians made final checks on the machinery and the remote control and monitoring equipment on the clean Lanby. When the checks were completed and all hands brought on board, courses were set for Dun Laoghaire with the dirty Lanby in tow.
Lanbys (Large Automatic Navigational Buoys) were first established on the Irish coast in 1976 as replacements for lightvessels. They are invaluable as highly visible aids to navigation and are also very cost efficient.
The normal sized navigational buoy used around the Irish coast is 10 feet in diameter but Lanbys are 40 feet in diameter. Lanbys are equipped with a powerful flashing light, electric fog signal, and a radar transponder beacon (Racon). Electric power for these aids to navigation is provided by duplicated diesel generating equipment and sufficient fuel is stored in the Lanby to last for more than a year. The Lanby can be refuelled at sea.
The Lanbys are remotely monitored and controlled from the Lighthouse Depot, Dun Laoghaire.
This is one of Granuaile's more involved routine operations. The size and the circular shape of a Lanby makes it necessary to take specific precautions when towing and manoeuvring it into position. While circular structures are generally stable when stationary, they are unpredictable and erratic when moving through the water. When one considers that the structure weighs over 85 tonnes it will be appreciated that good weather conditions are vital for Lanby operations.
On the day of this operation the wind was light and the sea state unusually calm. As the Codling station is in an area of strong tides it is important to commence work just before slack water.
Lanby mooring system comprising 220 metres of 44mm stud-link chain, connected to a 3 tonne sinker and a 4 tonne anchor resting on the sea bed. The total weight of the chain (excluding the sinker and anchor) is 91Ž4 tonnes. The anchor secures the mooring to the sea bed, while the sinker acts as a damper to minimise the pull of the mooring chain on the anchor. The recovery chain enables the mooring to be hauled on board the service vessel.
Towing the clean Lanby from Dun Laoghaire at 6 knots with two 5 inch polypropylene hawsers, Granuaile proceeded to the Codling station so as to arrive one hour before slack water, which was to be 12.30 pm.
The good conditions on this occasion meant Granuaile could secure both Lanbys alongside without causing damage to Granuaile, or to either of the Lanbys.
With both Lanbys secured alongside the ship the mooring chain was brought on board Granuaile by attaching a wire rope to the recovery chain which is connected to the Lanby's main mooring chain, and hauling it in. The end of the Lanby mooring was then secured to the deck, and disconnected from the dirty Lanby by the ship's carpenter. With enough mooring chain securely on board to allow sufficient slack, the end of the mooring chain was passed underneath the ship to the opposite side by means of a heavy-duty line.
So as to avoid the chain running out at high speed a series of light rope lashings was placed along the 50 metres of slack chain. As the weight came on each lashing the order to cut was given and control maintained. After what seemed an eternity, the end of the Lanby mooring showed above the water on the port side. The mooring was hauled in and secured to the deck, ready to be connected to the clean Lanby.
The connection of the main moorings to the Lanby tail was made using the age-old and proven head-up method. This entails heating the pin of a 44mm clenching shackle to a temperature that allows the metal to be beaten by sledge hammers and evenly spread across the shackle face. Carpenter Jim Corbin is the man for this job and he takes great care to ensure that the pin fits tightly.
After connecting the mooring chain to the clean Lanby, the Lanby's position was checked using the Global Position Fixing System and differential correction stations (dgps). When Captain McCabe was satisfied that the Lanby was on her correct station and the foredeck personnel were ready, the order to slip the moorings was given.
Before departing from station a team of Lighthouse Depot Technicians made final checks on the machinery and the remote control and monitoring equipment on the clean Lanby. When the checks were completed and all hands brought on board, courses were set for Dun Laoghaire with the dirty Lanby in tow.
Lanbys (Large Automatic Navigational Buoys) were first established on the Irish coast in 1976 as replacements for lightvessels. They are invaluable as highly visible aids to navigation and are also very cost efficient.
The normal sized navigational buoy used around the Irish coast is 10 feet in diameter but Lanbys are 40 feet in diameter. Lanbys are equipped with a powerful flashing light, electric fog signal, and a radar transponder beacon (Racon). Electric power for these aids to navigation is provided by duplicated diesel generating equipment and sufficient fuel is stored in the Lanby to last for more than a year. The Lanby can be refuelled at sea.
The Lanbys are remotely monitored and controlled from the Lighthouse Depot, Dun Laoghaire.