Ainscough lifts abandoned vessel
29 November 2021
In the UK, Ainscough Crane Hire’s heavy cranes team partnered with Gilpin Demolition and Dorset Council to remove a sunken fishing vessel from Weymouth Harbour.
Ainscough used a Liebherr LG 1550 lattice boom truck crane rigged in SLDB configuration with a 42 metre main boom, 160 tonnes of main counterweight and 140 tonne tray counterweight. Additional 7.5 x 2.2 metre steel mats were laid down and a 100 tonne capacity Liebherr crane was also used for the rigging.
The boat, called FV Gitte and built in 1982, was formerly a Danish trawler 17.7 metres long. It had been moored in the harbour behind Weymouth Pavilion since being discarded in March 2020.
Harbour staff from Dorset Council had been pumping water from the vessel on a weekly basis to stop it sinking. In March 2021, permanent pumps were fitted and monitored daily but it was insufficient to stop the vessel sinking at the start of October.
After it sank, equipment was put in place to minimise damage, including 25 metre and smaller absorbent booms, and seven absorbent netting bags.
At this point, the Council enlisted Gilpin Demolition to manage the removal and ultimate dismantling of the vessel. Ainscough was appointed by Gilpin to complete the lift from the harbour.
A survey of the vessel estimated its weight at 73 tonnes. Uncertainties over the amount of water that could be pumped out before and during the lift meant Ainscough planned for a 115 tonne lift.
No exact drawings were available of the vessel so Ainscough planned where to sling the boat based on a combination of information from the survey and historical details related to similar vessels. This entailed a system within the lifting tackle which allowed the altering of the pitch of the boat as it came out of water.
The boat was steadily lifted until it gained weight. At 80 tonnes, it was high enough to put pumps in to remove more water. Its final weight, with as much water removed as possible, was 83 tonnes.
A 60 tonne air hoist was incorporated into the lifting arrangement and the preparation team included commercial divers.
Patrick Denby, heavy cranes contract lift manager at Ainscough Crane Hire, said, “This lift presented a few challenges. The vessel being submerged in the water, combined with there being scant official detail regarding its dimensions, meant we had to factor in a range of uncertainties and plan accordingly.