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Traditional Maritime Skills :: Slipping

Slipping

Introduction

At the Meerman Yard in Arnemuiden ships from Zeeland are regularly taken out of the water on the perpendicular slipway in order to be maintained or repaired. Historische Scheepswerf C.A. Meerman in Arnemuiden is the oldest yard in Zeeland and one of the oldest shipyards still in operation in Europe. The ships that are maintained here mostly belong to the Stichting Behoud Hoogaars, an organisation dedicated to retaining sail-powered fishing boats from Zeeland as part of our sailing heritage.

A ship belonging to the foundation Stichting Behoud Hoogaars was taken out of the water for the photographs used in this instruction.

Use

Wooden and steel ships and even GRP ships have to be taken out of the water regularly for maintenance and repairs. Yachts are lifted out using a crane but larger ships are taken out of the water on a perpendicular slipway or a parallel slipway. A perpendicular slipway is at 90 degrees (perpendicular) to the water; the ship is hauled out of the water with the bow towards the quay and is at an angle on the carriage. A parallel slipway is side on (parallel) to the water; as it is being hauled out the ship remains parallel to the water and straight on the carriages. A parallel slipway is used for larger ships; a perpendicular slipway is a good option for use with the wooden Zeeland fishing boats. In the past, slipways with a capstan were also used. 

Procedure

A perpendicular slipway is used for launching a new-build ship as well as for hauling existing ships out of the water for maintaining and if necessary repairing the area of the ship below the waterline. Here we describe the hauling out of a ship. The step-by-step procedure for slipping is as follows:

  • The first step of slipping is to clamp and secure the steel cable, which transfers the power of the winch to the carriage via a number of heavy blocks with numerous windings. The ship will later be hauled out on the carriage. To do this, the carriage is first moved to the top most position and anchored in position using the locking pin. The steel cable is fed through the blocks and tensioned before being secured using a locking pin. Leave the two locking pins of the uppermost carriage secured in order to be able to adjust the length between the two parts of the carriage.
     
  • The second step is to set the correct length and width of the carriage. The carriage consists of two parts, jointed together by a heavy chain. The carriage is constructed from two heavy square steel frames, which can move up and down the ramp rails on wheels that are mounted in the corners of the frame. Two ‘cradles’ are mounted on the frame and these can tilt forward and back on a shaft. The ‘cradles’ can therefore adjust to the shape of the ship and provide maximum support to the area below the waterline. Two heavy steel posts, protruding vertically upwards, are mounted on the side of the two parts of the carriage.
     
  • To be able to determine the correct length and width of the carriage you must first measure the ship. To do this, you measure the length between forward-most and aft-most bollards and the beam of the ship from the keel beam to the side at the position of the forward-most and aft-most bollards. (For ships that are regularly hauled out at the Meerman Yard the correct length and width are noted down on the wall in the winch cabin (the operating cabin.)
     
  • Set the correct width of the carriage by securing the two posts closer to or further away from the carriage. The post slides with a metal sleeve along a steel profile in which holes are drilled. Once the post is in the correct position you lock it in position using a locking pin.
     
  • The correct length of the carriage is set by shortening or lengthening the chain that joins the two parts of the carriage. To do this, you measure how much space there has to be between the two carriages. Use the chain hoist to lift of lower the bottom carriage. Once the correct distance is achieved between the two parts use a shackle to secure the chain between both parts to the eye. The carriage is now ready to be lowered into the water.
     
  • Using an electric winch the carriage is lowered into the water on a heavy steel cable. The winch has two handles for reeling the cable and for paying it out. The winch also has a brake. [In the past slipping was undertaken using a capstan rather than an electric winch. A capstan is a vertical windlass around which a rope can be wound. A capstan is manually operated, by inserting long poles through it and using these to turn the windlass. The Meerman Yard is busy building a slipway with a capstan.]
     
  • By using the winch to pay out the steel cable that is secured to the carriage, the carriage slowly descends into the water via the rails on the ramp. The carriage submerges completely under water, however, from the two posts you are able to see the precise position of the carriage under water.
     
  • Allow the carriage to submerse to such an extent that the ship to be hauled out can just sail over it. On the instructions of the slipway boss the skipper makes fast to the two posts once exactly in the correct position. Check that the ship is straight in line with the ramp so that it is straight above the carriage.
     
  • The winch is now used to slowly haul the ship out of the water. During this process keep a close eye out to ensure that the ship remains straight and emerges from the water at the correct position above the carriage.
     
  • When the top carriage just emerges from the water, place a large timber wedge on the ‘cradle’ on both sides, against the cutwater of the ship. The ship keel beam rests on the carriage but the 'cradles’ prevent the ship from topping over. It is important that the 'cradles' support the ship below the waterline as much as possible. The ship is now secure on the carriage and is unable to turn on its side.
     
  • The ship is now hauled out further using the winch and the steel cable which runs through a heavy block with numerous windings in order to be able to manage the forces. Haul the ship out until the carriage is close to the two locking pins.
     
  • Once the carriage has been hauled out sufficiently, secure it by inserting the locking pin into the carriage frame on both sides.
     
  • The ship is now ready for jet washing and maintenance or repair. 
 
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Tools Required

  • Ramp with rails and rollers or wheels
  • Carriage
  • Steel cable
  • Blocks
  • Winch
  • Measuring tape
  • Locking pins
  • Chain tackle
  • Shackles
  • Wedges
  • Hammer

Materials Required

None applicable


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