Saturday, 17 February 2018

Rolling, rolling, rolling - moving HMCS SACKVILLE into the Sub Shed

After being hoisted out of the water on Fleet Maintenance Facility Cape Scott's (FMFCS) Syncrolift platform on February 11th, SACKVILLE's hull was cleaned of marine growth and prepared to transfer into the adjacent Captain Bernard Leitch Johnson submarine maintenance building in HMC Dockyard (hereafter referred to as the "sub shed" or simply the "shed").

By the morning of February 15th, SACKVILLE was ready to transfer into the shed.

Thursday morning was sunny, so I got some better photos of SACKVILLE on the lift. She also looks a bit cleaner.

SACKVILLE points towards the sub shed which she will soon enter. The army of bogeys under the ship can be seen here.

The view from inside the shed, looking out. The bogeys to the right are connected to the tow motor, and straddle inner two of the four rails. The tow motor will push these bogeys, and the attached tow bridle, out to join to the bogeys under the ship. The brow is still fitted in this photo.

An HDR image made from two different exposures - it turned out pretty good, considering I took the two exposures hand-held, and not from a tripod as I should have. Throughout the transfer, I had issues with the different exposures between the interior of the shed and the bright sunny day outside. The tow motor's traction chain is running along the centre of the image here.

A plated-over hull penetration below what would have been the chain locker or store. I'm not sure what it was for - it may have been associated with SACKVILLE's postwar career.

These hull penetrations are just aft of the bow slope transition, and are roughly where the original Type 123 ASDIC would have protruded below the hull. I'm not sure why there are two, though some of the early sonar sets required penetrations for more than one transducer. Again, both of these may not have been original.

Looking forward along the port side, showing the bilge keel, blocking, and bogeys. There are several of these plates on the hull that stand an inch or more proud of the hull surface. Four anodes are also visible.

It is important that the ship's hull be well supported during the move, so workers pounded shims into any gaps between the hull and the blocking.
The system for transferring the ship into the shed is fairly simple. Four rails run from the Syncrolift platform into the shed, and the bogeys which support the ship's weight straddle either the two outer sets of rails, or the inner set. The tow motor that propels the ship along the rails straddles the inner two rails.

The outer end of the traction chain that the tow motor grips to propel itself, with SACKVILLE in the background. During the transfer, the chain will be under considerable tension, and this presents a hazard to people in close proximity to the chain if it were to fail or snap. During the transfer, only FMFCS staff were allowed to remain in the work area.
Unlike a train locomotive, which uses the friction between its drive wheels and the rails to propel the train, the tow motor grips a heavy chain (I will refer to it as the traction chain in this post) that runs between the two inner rails from an anchor post at the inshore end of the shed to an anchor post at the inshore end of the lift platform.

The yellow post at the end of the traction chain is the outer anchor post, which allows the tow motor to pull itself out to the wharf. The tow motor can not go out onto the platform itself, as it can not pull itself beyond the anchor post.
In order to hook itself up to the bogeys under SACKVILLE, the tow motor pulled itself out to the Syncrolift platform along the traction chain.

The orange tow motor, at left, is now in position. It has pushed a series of bogeys and a tow bridle out onto the Syncrolift platform to bridge the distance between itself and the bogeys under SACKVILLE, and workers have connected the two sets of bogeys.
Once everything was connected, and non-essential staff were directed to designated observation areas, the transfer began. I was allowed to view the transfer from the mezzanine platform inside the sub shed, but was not allowed down to the shed floor during the transfer.

The transfer has begun, and the tow motor has moved back inside the sub shed. SACKVILLE is still on the platform in this photo.
There were several pauses during the transfer operation to confirm that SACKVILLE was still well supported by the blocking.

The view looking inward, with SACKVILLE now inside the building.

There are several levels within the sub shed, and this photo was taken from the highest level.
Once SACKVILLE was fully inside the shed, and the tow motor could not proceed further without hitting the end of the building, the intermediate bogeys between the tow bridle and the bogeys under the ship were removed to shorten things, and allow the tow motor to get closer to the ship, in order to bring SACKVILLE in a bit further. There are several overhead bridge cranes that span the width of the shed, and one of these was used to lift the bogeys out of the way.

One of the intermediate bogeys is lifted out of the way.

The tow motor is at the inshore end of the traction chain, which is attached to the inshore anchor post that is just outside the shed, through the dark opening just to the right of the motor. The anchor post itself is cast into a large block of buried concrete. The tow bridle is attached directly to the bogeys under the bow of the ship.
Once the ship was in position, I was allowed back down to the shed floor to get some more photos of the ship inside the shed. 

The tow motor is at the inshore end of the shed, and the yellow overhead bridge cranes can be seen behind the ship.

A view from the mid-level mezzanine platform of the starboard bow.

Compared to the previous photo, this was taken from the upper platform, which is just below the overhead bridge crane track. Some of the photos make the ship look like a model.

Another photo from the upper platform showing the ship from aft, with the brow (gangway) now fitted. It was lifted into place by one of the bridge cranes. The man pulling out the safety net is standing on the mid-level mezzanine platform.

A wider-angle photograph, showing the scale of the shed's interior, including the upper level translucent panels to allow in natural light.

A floor level image from aft.

A wider angle image from floor level, with the yellow bridge cranes visible at the top of the image.

A panoramic image from my phone. Until I viewed her from above, I never realized SACKVILLE's pendant number was painted on top of her radar enclosure.

Two FMFCS staff stand between the transfer rails, alongside the traction chain.
Now that SACKVILLE is inside the shed, her refit can begin, and is expected to last several months at least.

A complete gallery of my processed images of SACKVILLE's lift and transfer is linked here.

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