As cruise ships continue to grow in size and number, the theatres built for them do, too. Despite such changes, however, some basic rigging challenges remain.

On larger ships, the theatre's fly tower is three or four decks (30' to 40') high, 20' to 30' deep, and 25' to 40' wide, typically with a mixture of scenery battens, lighting trusses (fixed or motorized), curtain tracks, and scenic roll drops. Most stages have some limited backstage or wing space, although some do have wide wings or rear stage scene dock areas. Notably, the Princess Grand class ships have deep wings either side of the stage; the full width of the stage, including wings, is about 100', a surprise to many who see it for the first time. The stage will typically have a proscenium opening, possibly with a thrust stage or an orchestra pit with a lift, or it might be more open. Stage revolves are common, as are stage lifts; sometimes these are combined with lifts built into the revolve.

A typical cruise ship costs around $400 million to $800 million to build. The economics are such that the ships are in service 365 days a year, apart from short maintenance periods every couple of years. Cruise lines work hard to plan capacity and sail with close to full occupancy. So every crewmember occupying a cabin represents a loss of income. This means that stage crewmembers are expensive, not because of salaries but because of the cost of accommodating them. The number of technical crew used to operate the facilities has to be kept to a minimum. This is one reason why the stage systems, including rigging, are highly automated. All the rigging systems are usually motorized and controlled by a computer system operated by one person.

The largest technical issue for stage rigging aboard a cruise ship is, of course, movement, as the ship rolls and pitches. Although this movement is only very subtle most of the time, it is enough to cause potential problems. The bottom of a line suspended 30' from the top of the fly tower will move about 7" for every degree change in angle. A fly tower full of suspended equipment would smash itself to bits very rapidly if this movement were not restrained. As the ship moves up and down, over the waves, the acceleration has the effect of either increasing or reducing the force of gravity. In normal conditions, this effect is small, but in stormy conditions, it can be considerable, especially at the front of the ship, where the theatres are often located. The theatre equipment has to be strong enough to withstand the extra forces and repeated movement, which could cause fatigue failures if not designed and manufactured accordingly. It also has to be strong enough to survive greater forces during bad weather. Even though it is not expected to operate in these extreme conditions, the equipment must not get damaged during turbulent periods.

To avoid the problem of suspended scenery and equipment swinging around and damaging itself, all such equipment is guided. Typically, this is a simple T-shaped guide as often used for passenger lifts, or sometimes a simple section of Unistrut channel with a PTFE layer running inside. One of the limitations of typical installations is that the battens and scenery are only guided in the top half of the fly tower. This works fine for normal show moves, but if the batten is brought to stage level for maintenance or to change what is attached to the batten, it has to be disengaged from the guide and then reengaged when it is raised again. This can be fiddly and usually requires additional crew to align the guide with the track.

Stage Technologies, for example, has developed a system to get around this. The TanJent system has a vertical track in the top half of the fly tower that is connected by a curved section of track to a horizontal storage section, running across the top of the fly tower. A rigid chain arrangement with guide wheels is attached to the end of the batten and runs inside the track. The batten can move through its whole travel without manual intervention. This saves crew time when making changeovers.

Maintenance is another important issue on cruise ships. In operation every day of the year and with limited staff, ships have limited time and resources available for routine maintenance. The equipment can also be quite difficult to access, making things even more difficult. An ocean liner will typically be at its homeport for about 10 hours every week or so during a cruise schedule. This is often the only time available for contractors or suppliers to get aboard for maintenance. Visits to other ports can be arranged in emergencies, but these are often harder to reach, and the ship may only be there for six to eight hours. It can be difficult to do significant work at sea, as the theatre is in use. Overnight working is limited due to problems of noise transmission to cabins; noise travels well through the steel structure. It can also be difficult to arrange for service technicians to sail with the ship due to accommodation shortages, as cruise ships often sail with full occupancy.

Challenges all around — but at the end of the day, safety is paramount in designing and installing these systems, even when the job has to be done as quickly and efficiently as possible.

Matthew Tonks is based in London at Stage Technologies Limited, installer of over 300 rigging systems on some 25 cruise ships over the last 12 years, including the recent Queen Victoria from Cunard which went into service in December 2007.