Barbados Blackwood Screwdock (dry dock)

Our guest contributor is Keith Mackie, a South African Consulting Coastal & Harbour Engineer who specialises in Dry Docks and the Dry Docking of ships.  In December 2009 he was brought to Barbados by Caribbean Lifestyles Ltd. to survey the Blackwood screwdock and assess its potential for conservation and restoration.  Sitting in the Blackwood dock on a pile of rusty iron he found himself in engineers’ heaven.  The design of the Blackwood screwdock is a superb example of Victorian engineering, representing dry dock design at its best – good even by modern standards. Two primary elements of the design were unique: the use of power screws for lifting and trussed timber beams for the transverse girders.  Another key feature of the design was the spacing of the screw jacks which kept down the loading on individual screws and beams. Planking laid athwart each beam abuts that on adjacent beams and created a continuous working platform.

With the concurrence of Caribbean Lifestyles Ltd. an abridged version of this article was published in Civil Engineering in May 2010 and Keith read a paper at the PIANC Congress in Liverpool, UK in May 2010.  This article draws on that paper and on others of his published papers.

Here Keith Mackie shares with BajanThings some fascinating facts about the Barbados Blackwood Screwdock and what may have been possible had the dry dock mechanism been preserved.

Like the HARP space gun which has been abandoned and left to rust away, the Blackwood screwdock in Bridgetown – which was a marvel of Victorian engineering – has also been abandoned; lost to neglect and inertia, dilapidation and rot since 1984.

Blackwood screw dock in 2018. All that remains is the basin and the rusting screwlift mechanism. All the trussed beam girders made of two 20″ x 20″ baulks of greenheart timber laid side by side with each end resting on a cast iron plate at the end of the screw rods have sadly rotted away.

We would also like to thank:

  • David O’Carroll for archive photos from 1942 of HMS Black Bear on the Blackwood screwdock.  David’s father was the First Lieutenant of HMS Black Bear and during the prolonged stay in Barbados met his mother and they were married in April 1943.
  • Jim Webster for sharing his archive photos of the Blackwood screwdock and RA-II and for providing us with some notes and insight into the working of the dry dock.  We have appended Jim’s notes to the end of this posting.

Here are some archive photos of the Blackwood screwdock back in the days when it was operational:

Photos of Blackwood screwdock and HMS Black Bear from 1942:

Photos of Blackwood screwdock and RA-II from 1970:

It turns out that the screwdock concept and the shiplift system was a uniquely American invention of the early 19th century. Judging by the surviving descriptions and the remnants of the Barbados Screwdock, it was an invention that displayed all the elegant simplicity, practicality and ingenuity of the time and place of its inception.

The earliest screwdock, the earliest shiplift, was patented and constructed by Captain Jesse Hurd of Connecticut in New York in 1827 and incorporated as the “New York Screwdock Company” in 1828.

Two screwdocks were built shortly thereafter, one in Baltimore and one on the Kensington Reach of the Delaware River in Philadelphia.

The New York screwdock was suspended from eight screws of 41⁄2” (114 mm) diameter and apparently had a capacity of 200 tons. It was hand operated; it took about 30 men about half-
an-hour to raise such a vessel 10 feet (3 m).

The Baltimore screwdock was suspended from forty screws of about 5” (127 mm) diameter.

The Kensington Screwdock would seem to have been suspended from about 50 screws

The Barbados screwdock with a platform of 217’0” (66 m) by 45’6” (13.9m) is suspended from 62 screws of 41⁄2” (114 mm) diameter. The estimated capacity was around 1200 tons.

The shiplift in Barbados uses screw jacks for lifting gear leading to an elegantly simple and durable system that remained in operation for nearly 100 years. It only became derelict when the owners were liquidated and the facility was abandoned. Currently [2010] moves are afoot to restore the facility with both historical preservation and a fully working dry dock being issues involved.

The “screwdock” as it is known locally was built on the south side of an area known as the “Careenage” at the mouth of the Constitution river in Bridgetown by John Blackwood (see locality plan, figure 1). Work was begun in 1889 and the lift was formally opened on 10th March, 1893 by Miss Hay, daughter of Sir James Hay, then Governor of Barbados.

Figure 1 Screwdock Locality

John Blackwood came out from Scotland in the early 1880’s as Assistant Engineer in the employ of Messrs Grant and Morrison. Within a few years Blackwood took over the business and ran it under his own name until his death in 1904. The business was then taken over by his brother-in-law, William McLaren who ran it until the formation of Central Foundry who took over the running of the dock together with John Blackwood’s workshops on the Pier Head.

In the early 1980’s the Central Foundry was in financial difficulty when their workshops and offices with all records, including those of the screwdock, were destroyed in a fire. The company was never able to recover from this blow.  In 1984 the Central Foundry went into liquidation and the screwdock ceased operations. The screwdock has been derelict ever since.  For some time thereafter, the site was under the jurisdiction of the Coast Guard which probably explains why there appears to be almost no vandalism of the site, only deterioration.

In its early history, Barbados was one of the major ports of the new world partly, in a world of sailing ships, because of its windward position with respect to the rest of the Caribbean. Even in the 19th century, it was still a very busy port, some 1500 vessel a year calling in the 1890’s. The decision to build a dry dock in Barbados was very much a response to this shipping activity – at the time Campbell’s dock in Bermuda of 380 ft (116m) was the only other significant dry dock in the region.

In November 1887 the Barbados Parliament passed an act to authorise the lease of Government lands for harbour improvements and the construction of a dry dock. A lease for the site of the screwdock in favour of John Blackwood was only signed in February of 1899. Under the terms of the lease a construction period of two years was allowed at a rental of £40 a year. Thereafter, once the dock became operational, the lease would run for 20 years at a rental of £276.4.0. The Government reserved the right to take over the dock on expiry of the lease at prime cost less a reasonable allowance for deterioration. The cost of removing and re-erecting Government buildings, water and gas mains were excluded from the prime costs. The Government also claimed priority for docking their own vessels.

In March of 1889 a Bill was passed to allow all construction materials, including timber, cement and machinery to be imported free of duty. Permission was also given for the free use of a diving bell, centrifugal pumps and the Priestman Dredger.  The the lift was formally opened on 10th March 1893 by Miss Hay, daughter of Sir James Hay,then Governor of Barbados.

Figure 2 View of the Screwdock and the Careenage

Actual construction took far longer than the two years allowed – the whole construction period being about four years. One of the reasons given was the flooding of the works by exceptionally high tides. Since the retaining walls had not yet been built, portions of the embankments collapsed into the works. While this can only be part of the explanation for the extended delays, it does serve to suggest that the works, at least initially, were coffered and built in the dry.

The initial drive for the dock was a 100 hp steam engine with a coal burning locomotive type boiler although, for much of the time, squeeze-dried sugar cane was used as fuel. In 1953 the steam engine was replaced by a 130 hp electric motor. (HUTSON F. 1973; THRELFALL T. 1995)

Hutson (HUTSON F. 1973) gives the following docking charges as originally provided for in the lease and those ruling in 1972. These figures are in Barbadian dollars as of 1972:

Vessels not exceeding 100 register tons
For 1st day including lifting$50$150
For each subsequent day25¢ per ton60¢ per ton
Vessels exceeding 100 register tons
For 1st day including lifting 50¢ per ton$1.50 per ton
For each subsequent day25¢ per ton65¢ per ton

Elsewhere Threlfall (THRELFALL T. 1995) gives charges as embodied in the original lease of 2s per ton for lifting and 6d per ton per day for dock occupation.

In 1968 a high pressure water jet was acquired to speed up the cleaning of marine fouling from ships hulls and for paint stripping (ST. PIERRE GILL, C.H. 2009).

By the 1970’s, the dock was still lifting over 10 000 tons of shipping per year (HUTSON F. 1973).
In 1977, in correspondence with Andrew Hutchison (HUTCHINSON A.P. 1977) at that time secretary, later president of the Barbados Association of Professional Engineers, he stated that the original drawings still existed but that they were “very worn and unsuitable for reproduction”.

By the start of the fourth quarter of the 20th century the operations of the Central Foundry and the screwdock were coming to an end. Peter Simpson was quoted as saying that the dock was “antiquated and not easy to work” (ST. PIERRE GILL, C.H. 2009). Although ship construction was changing from wood to steel, labour rates were increasing and Barbados had lost its pre-eminence as a shipping centre, institutional and financial matters seem to have been at the heart of the problem. In the late 1970’s there were also problems with the lease of the site. Central Foundry was not able to reach agreement with the Government on this matter.

Central Foundry had suffered a number of fires, the first in 1938 and then in 1948. They were able to recover from these but it was the third fire in 1981 that ravaged the works and destroyed all the records. The firm never really recovered. In 1984 it went into liquidation and the screwdock ceased operations. It has been derelict ever since (THRELFALL T. 1995).

Context of the Screwdock
Threlfall (THRELFALL T. 1995) makes the comment that “after carefully studying some ideas embodying hydraulics, Blackwood chose a system based upon screw-jacks”. Although this quote is not explicit, this does sound rather like the Hydraulic Lift Dock of Edwin Clark (CLARK E. 1866; MACKIE K.P. 2008) built in London in 1857 – the first shiplift ever built. Clark was Robert Stevenson’s house boffin on the design of the Britannia Bridge over the Menai Staits and later his resident engineer on the construction of the bridge. His experience on that bridge seems to have been a significant influence on his choice of design. Although du Platt-Taylor (DU PLAT-TAYLOR F.M. 1949) mentions having seen it in operation as a child, it seems it was decommissioned and demolished early in the 20th century.

Blackwood’s Screwdock some 30 years later is the second shiplift ever built and, although it is currently derelict, it can be restored. It is this statement that makes the restoration of the screwdock such an important and viable proposal.

The modern, Syncrolift© style of shiplifts using steel wire rope winches was only developed in about 1957 by Raymond Pearlson.

In his paper on the screwdock Frank Hutson (HUTSON F. 1973) remarks: “It has been said that a similar dock was supplied to some country in the Far East, but where it went to and whether it is still in operation is unknown, if in fact it ever existed”. This comment has since been picked up by other commentators on the screwdock with the site being given variously as Hong Kong or Singapore often in the positive and without Hutson’s proviso.

The mechanical equipment for the dock was provided by the Glasgow based engineering firm of Duncan Stewart. A rendition of the various Scottish engineering firms involved in supplying sugar mill machinery to Barbados was given by Peter Simpson (MACKIE K.P. 2009) during an interview for the December 2009 investigations. Of significance, the firm of Duncan Stewart was only a small player in this industry in Barbados at the time the screwdock was built.

Incidents in the life of the dry dock
Although industrial accidents are to be deplored, they are of considerable value in advancing the state of the art. Hutson (HUTSON F. 1973) records four such incidents:

  • 1935: The schooner Eastern Star fell over on its side after being docked causing the death of two workmen and injury to others. She was afterwards righted and repaired.
  • 1948: M.V. Willemstad, a heavy vessel, said to have been badly docked, caused three sections to break four days after being docked and said to have caused enormous overload on adjacent sections. By working around the clock, the sections were repaired and the situation saved.
  • WWII: H.M.S. Black Bear was a converted yacht with an excessively sloping bow. This was not properly supported and some adjacent sections were broken. These were repaired in time to prevent further damage.
  • 1953: The auxiliary schooner Cachalot caught fire while on the dock. The cause was overhead welding which caused considerable damage to the engine room but there were no casualties.

Design Concept

Figure 3 Screwdock Operational about 1960 (Renolds Review)

The four diagrams, figures 11 to 14, placed at the end of this paper have been compiled from measurements made on site during the week 7th to 11th December 2009. They have been drawn to scale but only the dimensions shown are the dimensions actually measured. The rest have been inferred from various sources. The dimensions shown are given in SI metric measure although the dock was originally built to imperial measurement which is still in general use in Barbados. Measurements were made with linen tape, pocket tape and vernier caliper and, except where an original exact, rounded, imperial dimension could be inferred, are of limited accuracy.

This lift differs in concept from the earlier Clark system or the later Pearlson Syncrolift© system. Where the Clark system uses long stroke hydraulic cylinders as the lifting medium and the Pearlson system steel wire rope winches, the Blackwood uses long power screws. The practical capacity of individual screws is much less than hydraulic cylinders or winches so many more are needed and the main beams are much more closely spaced – so much so that, at least in the case of the Barbados screwdock, no intermediate grillage is needed between the beams.

Figure 4 Screwdock with Large Coaster (HUTCHINSON A.P. 1983)

The Blackwood has a very simple plan. It uses 31 screws down each side set at intervals of 7’0” (2133.6mm) and 31 sets of girders spanning between pairs of screws. Planking laid athwart the main beams provides a continuous working platform when all the beams are up.

The main rectangular plan of the dock, allowing for run-off of the retaining walls past the screws is 217’0” (66142 mm) and the clear space between copes is 45’6” (13868). A triangular space at the landward end of the pit extends its length by another 23’0” (7010 mm) to give a total length of 240’0” (73152 mm).

The civil engineering structures consist of coral block walling – a vertical retaining wall around the perimeter of the dock with rectangular, 2’0” (610 mm) wide by 2’6” (762 mm) deep vertical buttresses at 7’0” (2133.6) centres to carry the screw loads. Aside from the actual facing of the wall and the buttresses, the details of the wall construction are unknown.

The buttresses have a pair of 12” (305 mm) by 9” (228 mm) timbers placed over their tops, extending from the face of the copes to some distance behind the retaining wall face to receive the timber cope beams – a pair of 12” (305 mm) by 12” (305 mm) Greenheart baulks

The girders are constructed as trussed beams. The beam portion is formed from two 20” by 20” ( 508 by 508 mm) baulks of greenheart timber (given, in some references as “whalebone” greenheart) laid side by side, each end resting on a cast iron plates at the end of the screw rod. A cotter and washer system underneath these plates transfers the load to the screw rods. It has not been possible to examine the bottom of the plates but from photos it seems that the end of each screw rod is squared where it passes through the plate to prevent it from turning with the gear wheel and so failing to rise or fall as the wheel turns.

Figure 5 Last Remaining Trussed Beam showing Planking Athwart the Beam and Timber Keel Block.
Timber Cope Beams and Coral Buttresses can be seen in the background.

Four cast iron brackets, one on top of each end of each baulk, act as anchors for the 2” dia (51 mm) steel tie rods that dip down to about 12” (304 mm) below the soffit of the baulks. Cross pieces of 12” (305 mm) square timbers passing under the main baulks serve to transfer the load from the baulks to the tie rods.

Figure 6 Main Drive Train

The main drive, which has the option of a 1:1 or a 1:2 reduction gear box, is transmitted by shafts and bevel gears to the two main drive shafts – one on each side running down the full length of the cope. At each screw there is a worm floating on the shaft and a sliding dog clutch keyed to the shaft that can engage or disengage the worm. The worm in turn engages a worm wheel. The screw passes through this wheel. It has a bronze nut and thrust washer embedded axially in it to engage the screw and raise or lower it. Each gear set is mounted on a cast iron base plate set onto the timber cope beams exactly between the wall buttresses.

The screw itself was cut from 4” (101.6 mm) OD “bright” steel shafting. The thread appeared to be a 0°/52° buttress thread with a pitch of 1” (25 mm) although actual measurement seemed to suggest something more like 0°/62°.

Docking Operations
Some information on the practice of docking vessels on the screwdock was obtained from Mr Joe Weeks. For a period of 10 years in the 1960’s and 1970’s he had been Assistant Dockmaster (MACKIE K.P. 2009).

Other than a steel ring embedded in the concrete at the head of the dock, there is no sign that the dock was ever fitted with any dock furniture – fenders, bollards, fairleads, capstans etc. Weeks confirmed that the dock was operated so. On occasion, the vessel being dry docked would hang a few used tyres over the side or a few would be hung over the side of the dock.

Generally, six lines were used to bring the vessel into the dock and to position it. A head line was made fast to a ring set into the concrete at the head of the dock and the crew on board the vessel would warp the vessel into the dock either by hauling manually or, if available, by using an on-board capstan. Two breasting lines were used each side to position the vessel. A stern line was also used mainly, presumable, to warp the vessel out of the dock.

Mr Weeks confirmed that vessels (presumably he was referring to larger vessels such as coasters) were always brought to an even keel by flooding the forepeak tanks to avoid any sue load. As the vessel took the blocks, the water would be pumped out to lighten the vessel. This water had to be replaced on undocking as the vessel went into the water.

If a section was lowered to work on the keel, the screws to that section were marked so that the beams in the section could be brought back up to exactly the original height against the keel.
If the platform was lowered too far and sat on the bottom, the load would come off the cotters that secured it to the screws and they could and sometimes did work loose so that the beam end became effectively disconnected.

Joe Weeks reported that surge was not a problem. No docking operations, docking or undocking were done when there was rough weather at sea with a surge running up the Careenage. In fact the screw drive system does not permit of any penduluming of the platform which would bend the screw rods if it happened. If the surge got bad, the lift was kept up, clear of the water. In the event of hurricanes and severe storms, blocks of wood were inserted between the main girders and the cope beams and the lift tensioned against the blocks to fix it securely.

Joe did comment that normal surge had never delayed docking or undocking, only hurricanes and severe storms.  The deck planking was laid tight to prevent barnacles and scrapings falling through.

Staffing levels were:

  • 1  dockmaster
  • 1 assistant dockmaster
  • 6  permanent men on dockmaster’s staff including the 2 no divers. Divers only received extra pay while they were diving. At other times they assisted the rest of the staff.
  • 8 – 12 casual workers to assist with the docking as needed.

All parties assisted with the scraping and painting of the vessels

A separate department employed an engineer foreman and 6 engineers to work on the ships. These men had nothing to do with the docking of vessels.

Weeks and Peter Simpson (MACKIE K.P. 2009) concurred that it was unsafe to walk along the dock in the region of the main load concentrations when a heavy vessel was being lifted. Under these conditions, the gears and worms would emit sparks and small chips of hot metal. These sparks and chips made it uncomfortable to be near the gears when this was happening.

Central foundry made all replacement screws, bronze nuts and cotter pins. Gear wheels and worm wheels were imported. At one stage both were supplied in the wrong grade of metal and were sent back.

Joe commented that at one time during his stint, there had been a proposal to scrap the drive shaft, worm and gear system and fit each screw with its own motor.

Peter Simpson confirmed that the overall condition of the dock had been allowed to deteriorate to a dangerous level some time before the fire and before the lift was abandoned. He had in fact put in a report on the condition that was also lost in the fire. He stated that before the fire a complete set of documents including drawings of the dock were held by Central Foundry.

Nothing has survived of the bilge support system except old photos. It would appear that it consisted of Morton type sliding bilge blocks riding on inclined baulks (see figure 8). Rollinson (ROLLINSON D. 1993) states that these baulks were attached to the main girders by a metal hinge structure at the inboard end. Thus, the inclination of these slides could be varied by changing the blocking that supported the centres and the outboard ends of these baulks. With high bilge vessels, this reduced the build-up of the bilge blocks. The inclination of the slides did make it easier to pull the blocks in against hull of the vessel.

Condition [as of December 2009]

Figure 7 The Screwdock – 2007

Superficially, the dock, as shown in figure 7 is derelict and has been for 25 years. Certainly, this has caused gross deterioration of all the parts to a point where little could be reconditioned and reused. A closer examination, however, reveals a very different picture that corroborates Peter Simpson’s comments (MACKIE K.P. 2009) about maintenance towards the end.

It seems likely that the level of maintenance deteriorated with the uncertainty over tenure caused by disagreement between Central Foundry and the Government, probably exacerbated by the financial situation of the company. By the end, the screwdock had reached a stage where it was no longer safe to work and the greater part of the works needed to be replaced if it was to be brought back to a working condition. In effect it needed to be completely rebuilt. It is not surprising that the liquidators abandoned the installation. Its residual value as a working facility was virtually zero and the site – and effectively the scrap – belonged to the Government.

Figure 8 Screwdock in 1995 – 10 years after being abandoned.

A diving inspection showed the coral block walls and the buttresses to be in very poor condition. There were a number of cracks in the walling and a number of blocks missing from the buttresses (see figure 9).

In 1995 the main beams, decking and bilge support slides were still in place. All but one have now disappeared. It is difficult to tell from appearances what caused this – whether it was just deterioration or whether most of the timber was salvaged. Where stubs of timber remain at the screws, they do appear to have rotted away.

The cope beam timbers, mostly, are still coherent pieces of timber but generally in poor condition. Many of the transverse pieces on top of the buttresses, supporting the cope timbers, have failed in a manner that could be degradation but, equally, it looks very similar to the failure of overloaded timber keel block cappers (see figure 9).

Figure 9 Cope Timber and Buttresses

Both the worm and the worm wheel show a wide range of conditions from virtually new to excessively worn. The implication is that these are effectively consumable parts and were replaced frequently in a manner that allowed the levels of wear to become very variable. The excessive levels of wear in some of the parts is indicative of a deterioration in the standards of maintenance. Wear in the screws was difficult to detect in a brief, visual observation. None was specifically noted.

Figure 10 Worn & New Worm & Gear – Note the slightly different patterns of wheel castings used.

A peculiarity of the facility, as it is now, is the use of spur gears for the worm wheel. Proper practice is to use a specially formed gear for this duty. The most likely explanation is that the facility, as originally built, did use proper gear wheels but at some stage it was found expedient to use spur gears as replacements. This inappropriate usage does explain the high levels of wear seen and the comment by Weeks and Simpson that under heavy load, the worm and wheel emitted a shower of sparks.

Although the upper portions of some of the screws don’t look too bad, reconditioning them would probably weaken the threads unacceptably; also, the lower portions of rods have corroded to a point where none can be reused. Further investigation will be needed to see whether any of the lower cast iron base plates at the ends of the screws can be reconditioned. Given the length of their immersion in the sea, this is unlikely.

The cast iron base plates to the worm and wheel drive assemblies and the cast iron plumber blocks all look as if they could be reconditioned and reused; so too the sliding portions of the dog clutches. The condition of the shafting is questionable. Many sections have been reversed and remachined to extend their life.

The whole of the drive, the motor, switchgear, bevel gears and the gear change, has deteriorated to a point where it cannot be used or even reconditioned. The only exception is the main worm reduction box. These units are enclosed and proverbially robust so it is most probable that it can be reconditioned.

In his 10 years on the lift, Weeks was involved in replacing three of the timbers of the main girders. He remarked that none of the beams he had replaced was replaced again in his time. Some of the beams had dates of 25 years and older carved on them during that time (MACKIE K.P. 2009). This comment needs to be read in conjunction with the list of incidents given by Hutson (HUTSON F. 1973) and the failure of beams.

Restoration initiatives and the value of restoration
Concern for the screwdock dates back to at least the time of its abandonment. The following is an extract from a public letter (FRAZER H.S. 1984):

“I have just seen this article about this most extraordinary and unique Bridgetown Screw lifting dock. It is almost a wonder of the engineering world, sitting there unknown to Bajans and visitors!”

Over the years the Barbados National Trust, the Barbados Museum and Historical Society and various departments of Government have expressed an interest in the dock and variously in its preservation.

A notable feature of all this correspondence was the lack of knowledge of the practice of engineering in general and of dry docking in particular and a pedestrian mindset geared to the costs and practices of museum level preservation not to full industrial restoration. This is not surprising since the costs and levels of expertise that must be mobilised for the installation and operation of industrial facilities are orders of magnitude greater that of preservation of remnants of an abandoned facility. It is worth keeping in mind that generally, the practitioners at either end are immersed in their own issues and it is difficult for them to conceptualise the immensity of the gap between them.

The centenary year of the screwdock, 1993, saw the submission of two reports. In both studies, the screwdock site was still used by the Coast Guard as a base and this severely constrained the scope of these reports.

In late 1992 the Barbados Museum and Historical Society, the Barbados National Trust, the owners of buildings adjacent to the screwdock and the Commonwealth Development Corporation in conjunction with a number of business and financial institutions in Barbados entered into a working agreement and submitted a proposal to the Ministry of Housing and Lands (CDC 1993). It was based on reactivating the old buildings and warehouses in the run-down part of town adjacent to the screwdock and had been prepared by a team from the project group after visiting similar facilities in Britain and North America.

The focus was restricted to commercial tourism with a “Timewalk” experience of Barbadian history together with a museum and otherwise the usual tourist oriented shopping, restaurant and entertainment mall. The whole was to be integrated with the development of commercial tourist boating and yachting in the adjacent Careenage. Provision was envisaged for an initial clean up the screwdock site to integrate it with the mall development. However, it was expressly stated that even if the screwdock was restored to a point where it could lift light vessels, it would no longer be used for dry docking purposes.

The following are extracts from the response of the office of the Permanent Secretary:

“It is recognised that, at this point in time: –
(a) The isolated restoration of the dry dock has little potential for success;
(b) the proposals for the Time Walk Centre would complement those for the restoration of the historical dry dock;
(c) the restoration of the dock should not be divorced. from the adjoining private sector development; and
(d) restoration in this historical context should not be interpreted to be that the screw-lift mechanism will be capable of functioning in its original state, but rather that the proposed restoration will ensure the-long term protection of this valuable National asset and that public interpretation of it will be possible”.

The other report was compiled by David Rollinson (ROLLINSON D. 1993) and submitted to the Barbados Museum and Historical Society and the Barbados National Trust and integrated with the CDC work. The core of his report consisted of a heritage assessment and a condition survey.

He adopted the Evaluation Criteria used by the Ontario (Canadian) Heritage Properties Assessment programme for his heritage assessment of the screwdock site. Seven basic criteria were used: design, history, environment, social value, integrity, and archaeological and cultural landscape leading to the following summary:
1. The screw-lift mechanism located at the Bridgetown Dry Dock is thought to be the only one of its type in the world.
2. The Bridgetown Dry Dock is a significant cultural landmark for Barbados.
3. The Bridgetown Dry Dock is a significant landscape element on the waterfront of Bridgetown.
4. The introduction of the Dry Dock and its subsequent use played a significant economic, commercial and cultural part in the daily life of Barbados for almost one hundred years

Rollinson’s condition survey was done in 1992, less than 10 years after the facility was abandoned, nearly 20 years ago. At the time, the whole of the platform was still in position and his report rated it poorly. He was sceptical of the condition of the timber and reported that virtually all the metalwork to the platform was badly corroded and no longer serviceable. This was in contrast to his assessment of the fixed structure of the walling and timber cope beams and the mechanical drive and lift system. He reported the walling to be in good condition and the timber copes to be salvageable. This is certainly not the case today. His assessment of the mechanicals as being able to be put back into service completely failed to recognise the crippling effect of wear, lack of maintenance and inappropriate repair or substitution in the last years of operation of the dock before it was abandoned.

He made a highlighted note in his report that: “The screw threads used on the lifting mechanism will be Whitworth”. It is not clear whether he meant the main lifting screws which is manifestly untrue or he meant the holding down bolts and other fasteners which is probably true. He recommends that only Whitworth be used for any restoration work to maintain authenticity.

In various parts, his report contains the following highlighted notes that are very germane:

  • “No partial or complete restoration should ever be undertaken if an arms-length review of the proposed work leads to concerns about a successful completion.
  • “Work should not proceed without a formal restoration plan that includes financing details.”
  • “For reasons concerned with structural integrity, historical conservation, interpretation and public safety no consideration should be given to returning the dry dock to commercial-scale operation.”

The first two comments are almost self-evident and certainly valid; the third only to the extent that it hangs off the first two. In fact, if the first two can be satisfied and structural integrity and public safety assured, then issues of historical conservation and interpretation can only be achieved by the full restoration of the screwdock and its return to commercial operation. As discussed below, the physical substance of the individual parts is of little conservation value. An enormous conservation potential resides in recognising the elegance of the design of the coherent whole, independently of the parts, and in particular, in preserving the dynamic aspects that can only be done by operating the dock.

A current initiative to restore the screwdock is being led by Caribbean Lifestyles Ltd who have obtained an appointment from Barbados Tourism Investments (BTI), a government agency falling under the Barbados Tourism Authority to conduct a preliminary study.

Proposed Restoration
Today is pleasantly surprising to discover how many people in Barbados know about the screwdock and how all are very positive towards the idea of the restoration of the dock. By and large they are all aware of the special nature of the dock in the context of the history of dry dock engineering and the need to preserve it as a special part of Barbados history.

First prize will be the complete restoration of the screwdock to a fully operational dry docking facility. Given the current condition of the screwdock, this will involve a complete reconstruction of the screwdock, even if some of the existing parts, such as the screw-drive base plates can be salvaged and reused. It is anticipated that the cost would be in the same order as that of an equivalent size conventional shiplift – in the order of US$ 4 to 7 million.

Currently, plans have been mooted to develop a waterfront and marina in the area of the screwdock that may influence preservation planning. While such development would probably be amenable to museum/mall type use of the screwdock area, there may be problems with the activities associated with an actual working dry dock. This is not insurmountable. A similar situation exists at the Victoria & Alfred Waterfront in Cape Town with dry docking facilities within their precincts and they have been able to resolve the problem by sound management procedures and construction detailing of structures around the site. They do comment that before dry docking the vessel, the dock operator must conclude binding contracts between himself and the boat owner and his agents and contractors with regard to the necessary special working conditions.

Under the full restoration approach, most of the original construction would be replaced. This raises a major issue of authenticity. However, this is not as drastic as it may sound. During the working life of the lift of nearly 100 years, most of the parts have been replaced as part of normal operating procedures. It seems probable that many are no longer the same as the original parts.

A rebuild of this nature, strictly, would only be a hundred year service or refit and completely within the bounds of normal operations. Provided it sticks closely to the original design, it cannot be seen as “inappropriate” interference. The scope of the rebuild needed is, in large measure predicated by the hiatus in maintenance that happened in the last decade or so of its previous operation. A rebuild of this nature would also be an opportunity to correct inappropriate changes that have taken place, such as the use of spur gears. In a case like this, it is worth keeping in mind the distinction between preserving the decrepit remains of the original parts and preserving instead a working record of the original concept.

There are two major commercial justifications for recommissioning the screwdock. If it is run as a commercial dry dock it will be essentially self funding although it will need government backing to get it going as discussed below. Another aspect is the apparent robustness of the system. It consists of heavy, robust parts, easily understood, that remained in operation for nearly 100 years in a relatively remote area. There is a good probability that the Blackwood screwdock system is ideal for the Developing Areas of the world as an intermediate between the Morton type slipway and the Pearlson type steel wire rope shiplift. A restoration project will evaluate and highlight this aspect.

A sine qua non for this approach, from a historical and heritage point of view, would be to follow faithfully the original designs of John Blackwood. This in turn means a comprehensive research into the state of engineering technology available to Blackwood in the 1880’s and the extent to which modern technology has changed. Given the basic nature of the system, it is likely that it was already quite mature at that stage and has changed little in the interim. In parallel with the historical research, a comprehensive design study of the original structure and mechanism is needed both to understand the system and to highlight any design changes that must be made, for instance, the problem of breakage of beams or the availability of materials such as beam timbers.

A further essential requirement from a preservation perspective if the full restoration route is followed will be the compilation of a comprehensive set of documents covering drawings, specifications, materials, design calculations and operating and maintenance manuals. Multiple copies of these must be deposited where they will always be safe to avoid the loss of documentation as happened in the Central Foundry fire in 1981. They must, however, always be readily available to the operators of the facility to ensure not only the safety of the dock but also continuity of authenticity.

This raises a very important issue. Neither competent dry dock engineers nor restoration engineers are common nor are either of these fields well documented. If the facility is to be restored to a working dry dock then the operators will need to be practical people not especially skilled in either of these two disciplines. Faced with the type of inconvenient problems that continually arise in this type of industrial installation, without specialist skills, they are liable to adopt ad hoc solutions. These in turn are likely to accumulate until the facility is neither safe nor authentic. Providing complete documentation alone is a necessary but not a sufficient provision to prevent this kind of drift. Other mechanisms will need to be put in place to guarantee continuity, starting with the charter of the operating institution.

One approach to the management of the restored facility would be to set up some sort of International Dry Docking Institute as the entity to lease and operate the dock and to do so as an essential adjunct to the wider interests of the institute. There is nothing of this nature in the world today and, given the Cinderella status of dry dock technology, there is a real need for an institution of this sort to advance the state of the art. It will take an international campaign – initially in the shipping, ship building and ship repair world – to set up an institute of this nature and this, in turn, will yield international publicity for the Barbados screwdock and the Barbados efforts to restore it.

While operations and maintenance are artisanal activities of limited sensitivity, an institute would involve professionals who both understand the technology of the screwdock and its historical significance and be very jealous of their asset, its integrity and its authenticity. Although the scope of such an institute needs to be worked out, it could act as a repository for dry dock technology, including that of the screwdock and allow aspiring dockmasters to serve internships involving both working on the operations and maintenance of the screwdock and receiving classroom training in the subject. The screwdock itself, in its original form, will provide an excellent training in dry docking, involving aspects applicable to all types of dry docks.

Funding, ownership and operation are the next issues that must be addressed. By and large, ship owners will tolerate a docking charge, on average in the order of 10% of the spend on the work on the vessel while it is in dock. Generally, particularly on smaller units like the screwdock, this will only be enough to cover the cost of operation and maintenance. Hence a dry dock run as a common user facility will always run at a loss if it is burdened with the capital cost of the facility. Only ship repairers and National Governments can afford to own dry docks; the former because of the control it gives them over their business, the latter by virtue of the increase in tax revenue and other social benefits flowing from the ship repair activity (MACKIE K.P. DEANE R.F. 2006).

Private ownership by a ship repairer would be unacceptable in the case of the screwdock. A major objective is the restoration and preservation of the original Victorian structure and mechanism and it would be very difficult to ensure that a ship repairer owner both maintains the facility and refrains from altering it. The Government of Barbados, on the other hand, can afford to write off the capital investment – at least from the point of view of direct return on investment – and place the ownership in some sort of operating trust. The Government is also well placed to seek heritage grants to contribute to the capital cost. Hence any entity set up to operate the screwdock will need to be responsible not only for operation of the dock but also for preserving the integrity of the restored dock and it needs to be unencumbered by the capital cost of the facility to do this.

The water area is still the property of the Port Authority and they will have to come on board to ensure that they do not attempt to levy anything more than a nominal rental for the water area (MACKIE K.P. 2009).

A market study of the demand for dry docking and ship repair – whether there is enough demand to keep the dock fully occupied for most of the year and the nature of that demand – must be part of the studies of funding issues. A significant adjunct to this study must be an economic assessment of the benefits to the Barbados economy, particularly to industry and tourism and the extent of the tax flows into the Barbados Treasury that can be expected. This latter will establish the justifiable extent of Government finance for the restoration.

The capacity of the dock is another issue that must be resolved. Given the dimensions of the dock, it could probably accommodate steel vessels in the order of 1500 to 1600 tons docking displacement. This implies a Lloyds Nominal Lifting Capacity of say 1550 tons or 50 tons per beam and a Maximum Distributed Load per beam of 75 tons (MACKIE K.P. 2007). It seems unlikely that the beams could sustain such loads. The historical breakages under load reported by Hutson (HUTSON F. 1973) seems to corroborate this. With all due regard for authenticity, it may be necessary to strengthen the beams by an appropriate method, as, for example, by sandwiching the timber between steel plates. Plates on the sides and centre between the timbers would be least visible. It will be important, however to check the flexibility of the beams and the effect this has on load redistribution.

In a trial design, albeit using modern metals, a safe load on a 100 mm diameter screw was determined to be 66 tons, equivalent to a vessel of 2700 tons on the Blackwood screwdock (WHITTACKER R. 1992). Whittacker comments that the screws should be fitted with standard sacrificial anodes to limit corrosion to their lower ends (see figure 9).

Restoration of the retaining walls and buttresses is likely to be another major expense although it will not be possible to determine the scope of the work without more extensive investigations, including core drilling. The immediate, modern reaction would be to rebuild the walls and buttresses in reinforced concrete. Aside from not being authentic, there is the risk, over a long period, of reinforcement corrosion. It may be worth investigating retaining the unreinforced, solid masonry approach and repairing the exposed face with coral blocks and pressure grouting. The timber copes could be reconstructed in reinforced concrete but the same comments apply here.

Greenheart timber will be essential for the restoration if it is to remain authentic but the supply of this timber may be problematic particularly in the large sizes needed for the main beams. Previously replacement baulks were ordered at about 54 ft long (16.5 m) and cut to length to cut away the split ends. It would seem that replacement timber baulks can be obtained but with great difficulty and at great cost. Obtaining all the necessary timber may take one to two years since most of the large trees in the forests of Guyana have been felled and suitable trees must first be identified in the forests (MACKIE K.P. 2009).

If timber is used in the reconstruction, it will need to be replaced at intervals. The screwdock will need a steady supply of heavy timber baulks to maintain both structural integrity and authenticity. The matter of continuity of supply in turn, leads into the fields of forestry and the timber industry – fields outside the scope of this paper but matters that must be addressed if the dock is to be restored. It means that there must be a programme to secure reliable sources of timber. This in turn would lead to a general support for the practice of sustainable forestry. Given that a project to restore the screwdock can generate a lot of publicity, a linkage would lead to a synergistic increase in publicity for both the restoration project and for sustainable forestry.

Rollinson, in referring to the need to replace some cast iron components, referred to “fabricating” replacements. This comment very much reflects the modern situation where civil and structural engineers are expert at casting concrete but are no longer able to design or specify cast metal. Authentic restoration demands that only cast or machined metal be used – no fabricated metal. Again, where Rollinson does suggest cast metal, he suggests using the original as the pattern. It is impractical to do this. The pattern has to be accurately made to a specific, slightly larger size to allow for cooling shrinkage of the hot metal.

A point worth keeping in mind with respect to conservation: the full restoration and resumption of operations suggested here is essentially four-dimensional. The mere conservation of actual parts is only three-dimensional. Mostly these are replacements and anyway the elements of the lift are pretty much standard technology, still current today. It is the overall design concept, independent of the components, that is unique; the simplicity and versatility, elegance and efficiency of its layout and the effect on the actual dynamics of dry dock operations that is deserving of conservation. If only the physical, three dimensional components are preserved in a museum, expressly precluding resumption of operations as has been proposed by a number of commentators, then the preservation of all this dynamic component is lost. Only commercial operations that can do this and justify the cost.

Restoring the screwdock to a working dry dock will ensure that there is no loss of contact, connection, with the age when the lift was originally built and avoid creating the impression of ancient, superseded technology of historical interest only and not applicable to today’s industry. In fact, the technology actually used in the Blackwood screwdock lift was substantially mature at the time it was used and many of the parts are almost, if not actually still available “off the shelf”. Power screws (the form used in the screwdock), gears, shafts, plumber blocks etc. are still essentially the same today and, where they are needed still used. The trussed beams used for the platform, although no longer common today, are in a very real way a forerunner of the modern reinforced concrete beam. The screwdock, as it is, serves not only to connect us with the Victorian era but also to show us the essential components of technology still used today, albeit often concealed by covers.

If the restored dock is set up as a common user facility, very little space is needed around the dock. All machining and fabrication can be done off-site. The resulting clear space lends itself to an adjacent maritime museum and perhaps a restaurant or tea room overlooking the dock.
However, some sort of security around it will be needed if the public are to view the dock and docking operations. There will have to be proper security surrounding the dock to prevent incidents and injury to the public and restrictions on the kind of operations that can take place. If the waterfront/marina type development does go ahead, this sort of constraint on dry dock activities should be compatible with the requirements of developers.

Currently the site is the property of Barbados Tourism Investments, an agency of the government. It would be appropriate for them to set up a trust to own and manage the dock on a public utility, common user basis, where every ship owner is free to appoint whomever he pleases to work on his vessel. If the tariff of fees for the use of the dock, the docking charges, is set to a reasonable rate then these should cover the costs of operation and maintenance with a small profit sufficient to stay in business. They will not, however cover the costs of amortising the capital expenditure of the restoration.

Finally, there is the purely emotional impact of heavy, simple Victorian machinery, particularly when one can get up close and perhaps even touch it. If one is sitting nearby drinking tea and the dock is actually operating, lifting vessels in excess of 1000 tons displacement, the effect is enormously enhanced.

In its own way it can have the same cathartic effect often claimed for the touching or handling of animals such as dogs or horses or sitting watching the power of water in heavy surf. This has certainly been my experience of the week spent surveying the facility – an experience not just emanating from my specialisation in this field of engineering but a true “oh wow” visceral emotion.

Figure 11 General Arrangement Plan
Figure 12 Cross Section through the Dock
Figure 13 Detail of Worm & Wheel
Figure 14 Detail of Screw

Some additional Blackwood screwdock insight provided by Jim Webster

Engineering Details

  • The Blackwood Screw Dock measures 240 feet long, is 46 feet wide and has a 13 foot draft. The first 217 feet was fitted with 31 individual sections or platforms, 7 feet wide, each section is formed by two large Greenheart beams 2 feet wide reinforced by 2 inch steel rods – the last remaining one is visible. Each section is numbered and has a clutch on the shaft which drives the dock and which allows each section to be raised or lowered independently.
  • The sections are floored over and each one can be raised or lowered. Every alternate section is fitted with adjustable arms which can also be raised or lowered depending on the vessel. These arms were known as ‘knees’ and would frequently snap under the strain of the lifting process. The Central Foundry company in Barbados would fabricate and then replace many of these ‘knees’ each year.
  • The sections are supported at each end by 4 inch diameter screws which are 23 feet long with base plates and cotters below the beams. These screws were all originally imported from England and as time went on spares were sometimes imported unthreaded as threading could be done locally at the Central Foundry company. When the dock was fully out of the water the screws were fully extended. When the dock was in the water the screws were all retracted into the surrounding walls. You can see two screws lowered close to the entrance of the screwdock.
  • On both sides of the dock are massive retaining walls on which are fixed large green heart beams forming the ‘Camshores’. These would constantly need reinforcing as the pressure of the lifting would take its toll on the structure.
  • The large wood beams were 18 inches square and came from far in the interior of the forests of Guyana and Suriname. There are large spare pieces of this wood still around today in various marine locations in Barbados.

Powering the Screwdock

  • Originally the line ‘shaftings’ were operated by a twin cylinder 100 horse power steam engine which obtained its steam from a coal burning locomotive type boiler. The coal windows where the coal was shovelled into the steam engine remain today and are highlighted on the Eastern wall. The piles of coal were stored on the exterior of the southern wall behind the coal windows.
  • This would have been an extremely untidy and cumbersome method of providing power but in the day it did the job.
  • When the engine was under full power the smoke from the coal burning was stifling. There was a very tall chimney, with a cap on the top, to move the thick black smoke away from the dock.
  • With the implementation of electricity the old steam engine was scrapped in 1953 and replaced by an English built electric motor which can be seen at the facility today. For many years the old steam engine was kept at the site just in case the Electricity supply was unreliable.
  • The method of docking was to ‘raise up’ the number of sections based on the length of the vessel, above the water level. Specific planning of maintenance work required by boat was very important to ensure that revenue and efficiency was maximized for the facility.
  • Many times there would be two separate boats on the dock with the one taking the longest in the front and sometimes multiple ‘liftings’ could go on behind this boat if needed.

The lifting process – preparation

  • Lifting the wooden platform involved many men and careful precision was key to a successful lift. Two weeks prior to the lift detailed hull drawings were required and then a specific date and time would be set with the boat owner. Sometimes the boats would be docked close to the facility for a quick entry.
  • In the steam days the boiler would be ‘fired up’ at 4:00AM for a 7:00AM lift. 80 lbs of pressure would give enough for a successful lift. If the steam was too low the foreman would shout one word ‘Steam!!’ and on this instruction more coal was carefully added to the furnace – too much coal and the fire subsided as did the pressure – there was a delicate balance.
  • In the latter days the Electric motor made this process a little easier and the preparation time shorter.
  • All of the metal screws and the shafts would require constant applications of heavy oil to them to ensure that they moved easily in the lifting process and also to avoid surface rust due to the salt water environment of the dock.
  • The vessel would enter the dock with six ropes – one bow, one stern, two starboard side and two port side. All of the ‘rope men’ applied pressure on the ropes to keep the boat in place. The bow line was tied to the large metal ring at the front of the dock and the boat would be pulled forward from the men on board the vessel.
  • Once the boat was in place, the divers would enter the water and would instruct the foreman to raise a specific beam – each beam had a number – so that this beam would be raised to gently touch and make primary contact with the first point on the hull of the vessel.
  • This was done very carefully and in sequence – section by section. Once a number of sections were touching the hull, the ‘chocking’ would start by the skin divers with the large blocks of wood in various sizes – the smallest being just one inch thick ! The blocks were held in place by 6 inch ‘dogs’ on the floor of the dock underwater. Once this critically important process was complete the vessel would become secure. This process was known as ‘hogging’.
  • Once everything was secure the entire dock would be raised just ‘one inch’ to ensure that the vessel was perfectly level before anything else happened.

The lifting process – Raising the vessel

  • The ‘lifting foreman’ would be the sole person and the ONLY coordinator of the final lift instruction. All roads led to him! He would stand on the dock at the head/front of the Screw dock so he could see right down both sides of the vessel.
  • One final check and then the lifting foreman would give his final single instruction shouting loudly ‘UP!!’- at times he used a piercing whistle – One long loud blow – to advise the numerous people involved in the operation that the lifting process had started. All divers were instructed to get out of the water.
  • Once the lift started there was an atmosphere of excitement. The engine started to feel the pressure of the weight and the electric motor would start to spark like ‘starlights’, the smoke and fumes of the machinery under strain filled the air with anticipation. The wood would also start to creak with the weight. The water would be streaming off of the Screwdock’s massive wooden platform.
  • The vessel would also be creaking with the abnormal movement of dry land effects. The greenheart beams were known to appreciably deflect the weight across the length of the wood.
  • The noise of the screws, the motor and all of the creaking would fill the air in Bridgetown. The screws would many times spark and make a loud shrieking and metal grinding noise.
  • Once the lift was complete and the all clear given all of the ropes were thrown back on board and the ladders were brought onto the dock so that access to the vessel would be easy. The now exposed dock floor would start to dry out.
  • The specific repair would commence as soon as possible. The casual team would start the process of removing the barnacles from the hull which sometimes had been attached to the ship for years and were very hard to remove. Hull repair and painting would commence as soon as possible.
  • The dock Engineers would address the more technical work – the propeller shafts, rudder work, engine work and other tasks that were requested whilst the vessel was out of the water.

Unfortunate disasters

  • Sadly there were a number of disasters – In 1935 the Schooner Eastern Star fell over causing death to two workmen and injury to many others. This would have been the first major accident at the facility and must have been a devastating blow. The teams of workmen who laboured daily at the facility had a close bond as so much time was spent together at the facility.
  • During the Second World War the screwdock was kept very busy repairing Submarine chasers and other small craft attached to the British Navy in Trinidad. Three chasers were in the Careenage about to be docked when the S.S Cornwallis was torpedoed in nearby Carlisle bay.
  • Security during the war years was very tight and all workers had to wear identification badges. On one occasion Mr Cyril Gordon Crawford the manager of the workshop was refused entry by the security detail as he did not have his identification on him. This caused a significant stir in the Bridgetown working community
  • In 1948 the M.V. Willemstad was badly docked and broke three sections, four days after being lifted causing tremendous load and strain to the remaining sections. The repair process would have been tedious as the vessel still had to be completed on the dock and then lowered back into the water. The sections of the dock then had to be repaired after the vessel was launched. Luckily there was no loss of life in this accident.
  • In 1953 the auxiliary Schooner Cachalot had a fire in the engine room apparently due to overhead welding and ended up with great damage to the ship – thankfully there were no casualties. This fire was always surrounded with controversy as the engine room had been recently taken out and a new one was about to be put in – therefore there was nothing to burn – but burn it did. The dock team used the nearby fire hoses to little effect and then the Bridgetown fire brigade were called – putting hundreds of gallons of water onto the fire and into the ship’s hull, but the burning continued. In fact so much water went into the ship’s hull that there was concern that the weight of the vessel and the added water would damage the dock. The dock team then had to drill holes with manual hand drills into the hull of the ship to drain the vessel of all of the water. This fire was the only one recorded and this put financial pressure on the Screwdock.
  • A few years later the H.M.S Black Bear was also docked badly and caused damage to the dock.

The Electricity House

  • This Electricity house would have been erected in 1953 as the Screwdock transitioned from steam power to Electricity. The Coal and steam process was a proven and dependable method of power.
  • What you see here today is untouched from when this facility was set up in 1953. Sadly it has been exposed to the weather for many years but the main components can still be seen.
  • In the day this would have been a complex Electricity house and in 1953 there was a single manager responsible for looking after the Electricity powering process.
  • The volume of electricity required for lifting the Screwdock was significant and hence there are two main switches which had to be manually engaged – very carefully.
  • The Barbados Light and Power Company was established in Barbados in 1911 and was focussed on supplying domestic electricity to the Island in its initial existence. It was thought that the Screwdock would drain the power supply to the Bridgetown area during the lifting process and the Coal and steam process was a time proven alternative. This decision to move from coal to electricity must have been a decision that was not taken lightly.
  • The main Electricity line coming into this house is about two inches thick. This would have been normal gauge in the 1953 time period for supplying a large user of power.
  • Measurement of Ampere’s to the motors was key to this process as too much electricity could potentially burn out and ruin the expensive motors. The original Amp gauge still remains today

The Electric motor house

  • This area has been exposed to the elements for over 40 years. The level of rust is significant but this current layout is the exact layout as when the dock was in operation.
  • The large motors were all imported from England. The rods and the shafts were also imported from England. The transfer wheels that drove the long and large shafts all required extreme precision as there was no possibility of a margin of error.
  • All of the screws, gears, dog legs, cog wheels and shafts were fabricated in England. In later years these were fabricated by the local company – The Central Foundry.
  • The engine would drive the large shafts which in turn rotated the screws, which in turn lifted the huge dock floor when they were engaged.
  • The switch gear had three functions – neutral, up or down. This was all done by the switch gear operator. There was a small special house built for him at this facility. This role was an important one at the dock.
  • In the 1950’s the entire full-time team at this facility consisted of 6 Engineers and 12 dock staff. There were a large number of men who came from the nearby surrounding areas to assist with the casual work. Mr Holder was the main team man who gathered the casual workers from the Nelson street and Wellington street area. The foreman was Mr Darnley Griffith who was succeeded by Mr MacClean and then Mr Joseph Weekes until the closure.

The end of an Era

  • Sadly the detailed records and all of the files of this facility were all destroyed in three major fires that occurred at the Central Foundry during the life of this facility.
  • The Central Foundry business eventually collapsed in the 1984 and the sudden end of the Screwdock occurred shortly after their collapse.
  • The last vessel ‘officially’ on the Screwdock was the ‘Ecstasy’ – a wooden inter Island schooner – in fact she was still raised on the dock when the company folded! The remaining staff were separately compensated to complete the job and lower her safely back into the water.
  • The last vessel that was ‘unofficially’ lifted after the closure was the first Tiami Catamaran. Workmen from the collapsed company were sought out by the then owners of Tiami Cruises to execute the unofficial lift. This was the last time that this lift was ever used.
  • The facility was looked after by the Barbados Coast Guard until the current company ‘Attractions of Barbados’ – A Foster & Ince Cruise Services company – was entrusted with the facility in 2013 by the Government of Barbados.

Additional Blackwood screwdock photos

Here are some additional photos of the Blackwood screwdock by Chris Brady on flickr.

Useful References

  • Clark, E. (1866). The Hydraulic Lift Graving Dock, Min Proc ICE, vol 25.
  • Du Plat-Taylor, F.M. (1949) Docks, Wharves and Piers – Eyre & Spottiswoode
  • Hutson, F.C. (1973) The Bridgetown Dry Dock – The Journal of the Barbados Museum and Historical Society
  • Hutchinson, A.P. (1977) Personal correspondence with K.P. Mackie
  • Hutchinson, A.P. (1983) The Bridgetown Screw Lifting Dock – an engineering relic. Barbados Association of Professional Engineers
  • Frazer, H.S. (1984) Letter to Ulric Rice, Barbados Advocate.
  • Whittaker, R. (1992) Mechanical Systems of Dry Docking – Dept. Mech. Eng., University of Cape Town
  • Commonwealth Development Corporation (CDC) (1993) Barbados Maritime Centre
  • Rollinson, D. (1993) Heritage Review; the Bridgetown Dry Dock, Bridgetown, Barbados. Submitted to the Barbados Museum and Historical Society and the Barbados National Trust
  • Threlfall, T. (1995) Forgotten Centenary? Blackwood’s Screw Lifting Dock at Bridgetown, Barbados. The Mariner’s Mirror Vol 81, pp 213 – 217, London,
  • Mackie, K.P. (1999)(1) Small Mechanical Dry Docking Systems – COPEDEC V – Cape Town
  • Mackie, K.P. (1999)(2) Corrosion in Mechanical Dry Docking Systems. 14th International Corrosion Congress – Cape Town
  • Mackie, K.P. (1999)(3) The Practice of Dry Docking Ships – Part 1. Dock and Harbour Authority, London, vol 80 no 896-900
  • Mackie, K.P., Deane, R.F. (2006) Issues in Dry Docking – Economics, Shiplifts, Slipways and Keel Blocks – 31st PIANC Congress, Lisbon.
  • Mackie, K.P. (2007) Dry Dock Manual – Private Publication
  • Mackie, K.P. (2008) Blackwood’s Screw Jack Shiplift. Its Place in the History of Dry Docking and Shiplifts. Barbados Association of Professional Engineers
  • Mackie, K.P. (2009) Manual of Basic Coastal & Harbour Engineering – Private Publication
  • St. Pierre Gill, C.H. (2009) The Historical Significance of the Bridgetown Screwdock. Submitted to Caribbean lifestyles Ltd.
  • Mackie, K.P. (2009) Record of Interviews, Investigations and Recommendations submitted to Caribbean Lifestyles Ltd.
  • Bentley, S. (2010) Personal communication with Harbourmaster, Victoria & Alfred Waterfront

Responses to “Barbados Blackwood Screwdock (dry dock)”

  1. Andrew Simpson

    Amazing feat by our predecessors and admirable documentation. I’ve often wondered why no one has instituted a modern mechanism, using ballasted tanks that would be filled with compressed air, to effect the lift of even small vessels. Key aspects of the old screwdocks might be preserved as a heritage attraction and others used to support shade for those working beneath.

  2. barbadiantours

    Remember going there with my Dad to get his fishing boats (built by Mr.Babb and his brother and son – the boat builders) worked on and even for just boarding and disembarking after going down the West coat on boat picnics when it was all trees and mangroves down there except for Sandy Lane 1960-66 and till 1970

    Did my speedboat license from the Coast Guard station there in 2005

  3. I have visited the dock in the the last few years as it has an important role in my family history! The story was that HMS Black Bear an armed motor yacht based in Trinidad was put on the screw dock for repairs about 1942 or 1943.

    My father was First Lieutenant of the Black Bear and during the prolonged stay in Barbados met my mother and they were married in April 1943. I was told that the dock had been broken by the weight of the yacht but the posting suggests that the dock damaged the yacht! This sounds quite likely as I have pictures of the Black Bear when it first entered naval service in 1940 and then later during the war. From a slender pointed bow it took on a blunt aspect. The story explains why this change was made to the yacht.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Subscribe to BajanThings

If you would like to be kept informed when there are updates to BajanThings please click here to subscribe to the BajanThings e-mail update notification. Whenever there is new content added to BajanThings you will receive an e-mail telling you of the update.

SOLV Technology - Find . Inform . Engage.

A BajanThings Recommendation
Barbados Island life: photographs and stories by Craig Burleigh that celebrate Barbados island life in the 1970s

Notice Board

Contact BajanThings