2.6.3
Technical description of the bow ramp

The bow ramp was designed as a grillage with 4 longitudinal and 6 transverse webplated beams. The ramp plating was reinforced by rolled stiffeners. The dimensions were:

Length = 8225 mm
Breadth = 5500 mm
Weight = ca. 12.1 ts

At the fore part of the ramp 8 sloping flaps were fitted, which automatically extended when the ramp was opening. Each sloping flap worked independently of the others in order to compensate for heeling of the ship as long as the list did not exceed 2°.

The ramp was approximately 1.5 m longer than there was deck height available, thus was extending the forecastle deck in closed position by that distance. This extension was enclosed by the 'ramp house'.

The ramp was connected to the vessel's A-deck by means of 4 hinges of which the 2 outer ones were provided with spherical bearings and the 2 inner ones with bronze bushings. The bolts were of stainless steel.

The ramp was closed by the 2 hydraulic cylinders until the opening was only about 45 mm and the dead centre had been exceeded, thereafter 1 hook at each side of the vessel moved forward, engaged mating lugs at the upper end of the ramp and the ramp was hydraulically pulled tight against the rubber packings.

Then 4 conically shaped securing bolts moved from vessel's side into mating pockets at the ramp side, one after the other with audible noises. Once the bolts were fully extended contact was made with magnetic limit switches, switched in series which activated the green indicator light at the car deck control panel. This means that the green light was only activated if all 4 bolts had contacted the respective sensors. The 2 hooks and 4 locking bolts of the bow ramp were activated by means of one lever only and the system functioned in such a way that at first the hooks moved out and pulled the ramp tight against the rubber packings and thereafter the side bolts, one after the other, were activated.

The movements of the locking hooks of the bow ramp (ramp hooks) are shown on a drawing attached as Enclosure 2.6.3.77. It reveals that the ramp has to be closed by the actuators until there is an opening at the top of no more than 45 mm whereafter the locking hooks engage the mating lugs of the ramp. The particular contour of the hooks was chosen to ensure that when a force was applied a bending moment in the hooks became imposed which pressed the hooks against the pins of the mating lugs, i.e. the hooks could never spring off the pins. Only by plastic deformation after respective load exposure could this locking mechanism fail. Calculations of the hook by means of a FEM-model with contact elements between hook and pin - see Enclosure 2.6.3.78 (2) - revealed that plastic deformation commenced at a load of ca. 27 ts. and a so-called "plastic hinge" was built up. In summary it might be concluded that the failure-load of one ramp hook was in the range of ca. 30 ts., whilst the breakloads of the ramp pockets for the securing bolts have been calculated with ca. 15 ts. each. Consequently the total load required to break open the intact and properly secured bow ramp would be in the range of 30 ts. x 2 = 60 ts. plus 15 ts. x 4 = 60 ts., thus in total = about 120 ts. The weight of the empty visor is 55 ts.

Around the ramp opening rubber packings housed in flat bars welded to the bulkheads were arranged which should have kept the closed ramp watertight (weathertight).

 

2.6.4
Technical description of the stern ramps

The stern ramps were designed as grillages with 4 longitudinal and 5 transverse webplated beams. The ramp platings were reinforced by rolled stiffeners. The ramp dimensions were:

Length = 6500 mm
Breadth = 5500 mm
Weight = 11.5 ts

At the upper part of each ramp 9 sloping flaps were fitted, which always remained extended, also when the ramps were in closed position. Each sloping flap was 1.5 m long and had an independent flexibility in order to compensate for heeling of the ship as long as the list did not exceed 2°.

The ramps were connected to the vessel's A-deck by means of 4 hinges of which the 2 outer ones were provided with spherical bearings and the 2 inner ones with bronze bushings. The bolts were of stainless steel.

The ramps were closed by two hydraulic actuators each until the opening was only about 45 mm and the dead centre had been exceeded, thereafter 1 hook at each side of the ramp moved forward, engaged mating lugs at the upper end of the ramps and the ramps were hydraulically pulled tight against the rubber packings. Then 3 steel cams, extending the bulkheads to both sides of the ramps, moved - hydraulically operated - underneath steel pads fitted at the sides of the ramp. Thereby the ramps were pressed tight against the rubber packings fitted in steel bars welded to the bulkheads around the ramp openings.

The movements of the locking hooks (ramp hooks) are shown on a drawing attached as Enclosure 2.6.3.77. The particular contour of the hooks was chosen to ensure that when a force was applied a bending moment in the hooks became imposed which pressed the hooks against the pins of the mating lugs, i.e. the hooks could never spring off the pins. Only by plastic deformation after respective load exposure could this locking mechanism fail. Calculations of the hook by means of a FEM-model with contact elements between hook and pin - see Enclosure 2.6.3.78 (2) - revealed that plastic deformation commenced at a load of ca. 27 ts. and a so-called "plastic hinge" was built up.

It might be thus concluded that the failure-load of one ramp hook was in the range of ca. 30 ts., whilst the breakloads of the steel pads for the securing cams have been calculated with ca. 15 ts. each. Consequently the total load required to break open an intact and properly secured stern ramp would be in the range of 30 ts. x 2 = 60 ts. plus 15 ts. x 6 = 90 ts., thus in total = about 150 ts.

 

2.6.5
Passenger and pilot doors

The vessel was also fitted with 4 passenger doors, one each at the port - and starboardsides of decks 4 and 5 in approximately midships position. The dimensions were 2.5 x 2 m. Each passenger door was operated by an hydraulic cylinder and a link system, so that the doors were opening parallel to the ship's side and then moved aft.

Furthermore 1 pilot door was installed each at the port - and starboard-side of the car deck slightly aft of midships. These doors opened 90° towards the center line of the ship.

The doors were locked to the ship by 4 wedges each, which were compressing the rubber packings in order to give a suitable sealing. The wedges were hydraulically operated.

For further details see Enclosure 2.4.2.31.