Figures 10.1 and 10.2 show various bow door and ramp arrangements. Figure 10.1 Bow door arrangements. Figure 10.2 Ramps in stowed position. The visor concept became quite common from the 1960s. Clam doors were initially considered more complicated and before 1985 were incorporated only in a small number of ferries.
Most larger ferries built since then, however, have clam doors.
The length of the ramp was determined by the distance to the landing on the jetty and the position of the hinges. The position of the hinge point was in turn determined by the desire to have the ramp serve as an upper collision bulkhead. The history of compliance with this requirement is covered in Chapter 18. The available deck height was often too low to allow the ramp to be raised to a closed position. The solutions developed were then either to let the ramp protrude above weather deck level and be enclosed in a housing, or to divide the ramp into two sections with a hinge arrangement in between.