Bertha (drag boat)

Bertha is a steam-powered boat built in 1844 to remove silt from the Port of Bridgwater in Somerset, England. It is the oldest operational steam vessel in Britain, and possibly in the world. It is part of the National Historic Fleet.

The boat was built, of riveted iron, in Bristol by Lunnel, G & Co copying a design, by John McLean, developed by Isambard Kingdom Brunel to deal with silt in the Floating Harbour. It is a bed leveler or plough dredger, with a large metal blade, which could be lowered at the stern of the boat, below the water similar to a bulldozer on land.

Bertha is 50 ft long and 15.5 ft wide, with a tonnage of 60 tons. The power is from a coal fired single cylinder steam engine providing steam at 40 psi. A large flywheel and drive shaft drove a single-reduction spur wheel drive. It moved by being pulled along chains anchored on the quay.

Bertha worked in Bridgwater Docks, after the connection of the Bridgwater and Taunton Canal to the River Parrett, from 1844 until 1969. The vessel was initially owned by the Great Western Railway and then British Railways. She was then taken to the Exeter Maritime Museum, where she was shown working with the help of John Selby (welder and fabricator in Spaxton, Somerset). In 1997 it moved to the World of Boats at Eyemouth where it was restored. The Eyemouth Maritime Museum closed and Bertha is now in Bristol, but not on public display.