Friday, 2 April 2010

Medway Queen - Rebuild of a Dunkirk Veteran Part 3

Update on Progress at the Albion Dockyard, Bristol.
(Words G Stewart - Pics Dave Elms)

Almost 12 months have passed since our last article on this historic project and work has been continuing apace at Albion Dry Dock, Bristol.

Time to catch up then!!

On Thursday 15th October this project reached a major milestone when the first hull block was removed from the fabrication shed and placed onto the keel blocks in the drydock. More on this story can be found on the Medway Queen Website

Fabrication has continued in the dry dock with more blocks being added.

Click on an image to view a larger version

Jan 2010

A rivetted hull requires a frame onto which the plating is rivetted. This frame consists of vertical sections (which are formed into the correct profile to give the hull the correct shape) and transverse frames which run port to starboard and are fixed to the vertical items. The vertical frames are in turned rivetted to keel.
The shot below shows frames for the forward section of the hull ready to be erected.

The next photo below shows the hull in dry dock from the framed bow back to midships - with a section still to be framed. Note the smooth curve in the transverse frames - this is called camber and adds strength to the structure. In the case of open decks this also assists with drainage to the scuppers during inclement weather.

Another view of the hull looking from the after end. The two large bulkheads in the foreground of the shot divide the engine and boiler compartments. Note the opening for an access door.

A close up shot of the forementioned bulkheads. The one being positioned in the foreground is the screen bulkhead which will support the transverse heavy beam onto which the main engine entablatures will attach - the exact part is labelled 'B' in Part 2 of this series.

Back into the workshop for the next shot - here we see the top half of the "fore peak" bulkhead. The fore peak is the very front of the ship which terminates with the stem. This bulkhead incorporates a watertight access door. This piece will fit between the Main & Promenade decks and is situated on top of the bulkhead which forms the back of the anchor chain locker.

The "enclosure" in the right of the shot will be the Spirits Locker.

Feb 2010

Moving on this next shot from the dock floor shows most of the frames from the stem to midships have been erected to Main Deck Level.

This next shot shows the two heavy frames which will provide support the main engine entablatures and in turn the crankshaft and paddle shafts. As well as the forementioned support function this section of the ship must be heavier built as it has to withstand the thrust generated by the propulsion system which will drive the hull through the water - too light and the frames may distort causing misalignment or in an extreme situation structural failure.

As hull fabrication continues focus is slowly but surely turning to the machinery. Large items such as the Main Engine Block and Condenser must be installed in the hull before fabrication reaches a stage which precludes the easy installation of these pieces but before this can be carried out the pieces must be inspected and remedial / replacement works effected as required.

This next shot shows the Main Engine Cylinder Block in the workshop ready to be assessed for refurbishment. The steam enters the HP cylinder via the HP Valve. The pressure at which it is admitted is regulated by the Main Steam Inlet Valve which is in turn connected to the throttle lever. Controlling this determines how fast the engine will operate. The spent steam from the HP travels to the LP via the route shown by the blue arrow. It is then used by the LP cylinder and
finally condensed back into water and returned to the Boiler Feedwater Recovery System for re-use.

The equipment shown below is part of the Boiler Feedwater Recovery System. This is the air pump and it takes the output from the condenser, de-aerates it and passes it onto the hot well, which is the holding tank for recovery boiler feedwater. As with most ancillary equipment the air pump can be driven either by its own little steam engine or via a linkage from the Main Engine. This usually depended on the engine builder or the spare steam capacity available from the boiler to drive the ancillary equipment.

Finally we look at a boiler feedwater pump which, as the name suggests, pumped water into the boilers to be converted to steam to drive the ship. Medway Queen appears to have had only one of these but some ships (eg Waverley) had two which operate on a rota basis. It is these pumps which make the familiar whooping noise on Waverley.

So the works proceed apace - thanks once again to Dave Elms for providing the shots. If you want more information why not visit the Medway Queen Shipyard Blog or look in on the Albion Drydock Webcam

Gavin Stewart