Vlissingen Navy Drydock

Vlissingen Navy Drydock is a dry dock in Vlissingen. It is the oldest dry dock of the Netherlands, and is now a tourist attraction known as .

Context

Docking in the 17th century In the 17th century, being in ordinary was the normal condition of a warship. It meant that the warship was stripped of rigging and guns, and did not have a crew. A wet dock was the ideal location for a ship in ordinary, because it shelters a ship from the waves and tides. At the time, dry docks were a recent invention. They were found to be especially useful for inspecting and maintaining purpose built warships, the design of which had recently began to deviate from merchant sailing ships.

The wet dock

The Dutch navy was organized in 5 admiralties. Each required a suitable place to store its ships when they were in ordinary. The Admiralty of Zeeland already had a small wet dock and port since 1614. This did not suffice, because in winter many warships stood at the bottom when they were in port.

In 1687 Stadtholder William III sent a letter to the States General requesting approval for the Zeeland Admiralty to raise a loan to create a large wet dock. The reason given was that otherwise the warships of the admiralty would completely decay. The proposal was approved, and LA Cornelis Evertsen the Youngest and two engineers visited Vlissingen and Veere to determine where, and how the wet dock should be built.

The Vlissingen city government had some reservations. These centered on the removal of some private shipyards that had been founded around the existing dock, the commercial use of the wet dock, and the height of the city's contribution. After threats that the dock would otherwise be made in Veere, the city agreed in April 1688. The council soon after also gave permission to demolish the old Rammekenspoort, that was obviously in the way. The new and much larger wet dock was started in 1687 and finished in 1693.

The Dry Dock

Location

When the first dock was completed in 1614, it was connected to a part of the city moat located where the dry dock now is. In turn the city moat was connected to the shallow harbor Pottekaai by means of a lock called Leeuwensluis, which was later replaced by a stone sluice. This sluice had two big sewers with gates, by which water could be led to clean and keep the Pottekaai up to depth. Of course, at high tide, water could also be allowed to flow in the other direction. In spite of becoming a sluice, the construction retained the name 'Leeuwensluis'. One can suppose that this Leeuwensluis and its successor had lock chamber that enabled them to discharge so much water at once, that it had a flush effect. The 1750 map shows two sewers.

This connection made the stretch of old city moat an ideal location for the present dry dock. The traditional way to empty a dry dock was to put a ship in at high tide, and then to get rid of most of the water by letting it flow out at low tide. Of course the latter could not be done on the dock side. However, the Pottekaai was a tidal harbor, and so a dry dock at this location would allow ships to enter from the wet dock side, while using the tide from the Pottekaai side.

Design and construction The design of the dry dock was made by Captain John Perry in 1697. Perry (1670-1733) was an engineer later known for his book The State of Russia under the Present Czar (1716) and other works. In 1704 the decision to build the dry dock was taken, and a budget of 37,000 guilders was allocated. Construction started in 1704 and was finished in 1705.

Characteristics The dry dock has a ship shaped form in order to lessen the amount of remaining water that had to be pumped out. This was quite relevant, because pumps were driven by a horse-mill. The maximum length of ships that could dock was 180 feet, enough for any Dutch warship. The closure was done by regular lock doors. Commercial ships could use the dock for 10 stuivers per feet for 8 days.

In the 1830s an investigation showed that the old foundation of the dock consisted of three heavy fir beams in the length of the dry dock, close to each other. On top of these and perpendicular were fir 'kespen'. In the center these were supported by oak beams in between.

First Navy Service period (1705-1745)

Problematic service After the dry dock was taken into use, it soon showed problems. The main problem was that engineers were not able to sufficiently keep the water from the wet dock out of the dry dock. The result was that there was always water on the floor of the dry dock. The solution for making a waterproof lock gate for a dry dock was the ship caisson or ship-door invented in France in 1683, but this solution was not applied.

In 1737 an amount of water suddenly welled up near the doors, and in 1738 the same happened on the other side. There were some repairs, but these were not completely effective. The naval shipworm also played its part, and from 1737 to 1745 the dry dock gradually fell into disrepair.

In 1744 the sea lock, which closed the wet dock became unusable, and then the dry dock fell in further disrepair, because it could hardly be used till the sea lock had been repaired in 1753. A memorial stone has 1745 as year that the dry dock closed down.

Out of service (1746-1834)

Possibility of repair In 1762 orders were given to repair the dry dock's doors, and to clean the dock. In 1763 the whole, but especially the sluice 'Steenen Beer' or Leeuwensluis, was in such a bad condition, that the Pottekaai harbor could no longer be kept up to depth by draining through the lock. Multiple options were then considered. First was a complete renovation of the dry dock for 30,000 guilders. Second, abandoning it by constructing a dam., The third option was to do some maintenance and to repair the sluice. This last option, costing 9,570 guilders was chosen.

In 1766 Stadtholder William V, Prince of Orange proposed to repair the dry dock for 13,656 guilders, but this was not executed. By 1774 the walls of the dry dock were in complete disrepair. That year, and again in 1777, plans for action came to nothing.

1783 report

In May 1783 a commission issued a report about Vlissingen naval base. With regard to the dry dock it said that it was too far away from the workplaces, warehouses, and exit of the harbor. Also ships had become bigger, and so it could not be used for ships of the line of 60 and 70 guns. However, restoring the wet dock was more important. After that, it would be time to look at the dry dock.

1795 report After the Batavian Republic was founded, another commission made more specific remarks about the dry dock. Vlissingen was the most suitable place for a dry dock, because of the high tidal range. A dry dock would preserve many ships, and lead to better and cheaper repairs.

The French Time During the French period there were again plans to fix the dry dock. A plan showed a sluice which had been moved 9 m outward, and two new buildings, probably for a steam engine and equipment. It would have resulted in a 78 m long dry dock, probably 17.5 m wide.

Rebuild (1834-1838)

Investigation and new design After the French left, nothing much was done at first. Meanwhile, the condition of the Leeuwensluis (Steenen Beer) became so serious that it might break, and flood both dry and wet dock. It led to the construction of a dam on the wet dock side of the sluice. In 1834 works in the wet dock made that the water level in the dry dock became so low, that Engineer A.E. Tromp performed an investigation of the dry dock.

Tromp next made a design for a rebuild with use of a ship caisson and steam power. It would also lead to the dock becoming longer, so that the new larger ships of the line could use the dock. A less obvious change was that Tromp created a shallow step near the top by making the top of the inner sides lower than the street level. Approval for rebuilding the dry dock so it could service ships of the line of 84 guns came in on 31 December 1835.

Construction

The rebuild of the dry dock would take place in three phases. The first phase was tendered on 26 March 1836. It started with the construction of two dams on the outside of the dry dock. Next everything was excavated. A foundation was made for the walls that would hold the ship caisson, and the foundation of the dry dock itself was repaired and reinforced. The camp shedding got new woodwork. This cost 43,000 guilders, and was done by D. Dronkers from Middelburg. The navy supplied the materials. By June 1836 the dams were under construction in the wet dock and in the Pottekaai, which would close of the dry dock. On 29 November 1836 a hurricane hit Vlissingen. It toppled the heavy piledriving machinery, seriously hurting two workers.

The second phase would start in 1837, but was already tendered on 1 September 1836. These orders included the brickwork of the ship lock, the drainage sewer, and the pit for placing the steam engines. This time the tender included most materials. The order was won by J.J. van Uije for 47,000 guilders. By March 1837 pile-driving, the earth works and shoring were ready. Brickwork and work to replace the Leeuwensluis was about to start. By June 1837 brick work had advanced significantly. On 2 July 1837 the king visited Vlissingen and the dry dock. By August the second phase was almost finished. On 18 August 1837 Prince Frederick visited the dry dock, and the ship caisson which was under construction at the shipyard. By November 1837 the dry dock was practically finished, with work on the steam engine still underway.

The third phase consisted of the works on the Leeuwensluis. The last part of the works was delayed by a very severe winter. On 10 March 1838 there was a tender for making the upper camp shedding, a fence to close the terrain and for the removal of the dams. On 30 May 1838 the ship caisson was placed, and the steam engine was almost ready. The total cost of the rebuild came to 176,005.80 guilders.

The new dry dock

The caisson lock is a construction that holds a ship caisson. For this purpose its sides and floor have four rabbets. Each rabbet was 60 cm wide and 21 cm deep, and made from stones which had been carefully set and attached. An old model ship caisson then had two edges that fit these rabbets, allowing to vary the size of the part of the dock which had to be pumped dry. On the outside of the ship two memorial inscription were placed.

The caisson lock was 14.50 m long. At street level it was 17.50 m wide. The center of the inverted arc was 1.29 m below ebb. On the sides of the arc, this was 0.96 m. The radius of the arc was 13.445 m. The flat sides above the arc fell back at a slope of 18 degrees, and came to 4.98 m above ebb.

The discharge sewer and pit for the engines was dug simultaneously with the caisson lock. The pumphouse was built above the pit, and housed a regular low-pressure Watt steam engine of 18 hp. It powered a double suction pump of 60 cm diameter. With 13 strokes a minute, and 0.283 m3 a stroke, it emptied the dry dock in 6 hours, if water had first been let out via the Leeuwensluis.

The Leeuwensluis or Steenen Beer had to be repaired by the state if would be demolished in order to extend the dock. This was done when it was replaced by a dam with a brick closable culvert. The culvert was 11 m long, 1 m wide and 1.5 m high in the center of its arc. Its walls were 1 m thick. On both sides the sewer had gates. On top the dam was 10.80 m wide. The municipality was compensated with 14,000 guiders for the loss of the ability to keep the Pottekaai harbor up to depth by means of the Leeuwensluis. The stretch of floor of the Leeuwensluis which became available for the dry dock was then reinforced with a foundation, so it could serve as an extension of the dry dock.

New dimensions