Wednesday, December 24, 2008

Rigging Accommodation Ladders Aboard Ship

Ships are fitted with accommodation ladders that can be rigged and lowered over the side. These ladders provide a way for boarding or leaving an anchored vessel. Some accommodation ladders can be modified for use on a pier or barge. If more than one ladder is rigged, the forward accommodation ladder is the quarterdeck and reserved for officers and ceremonies. The after ladder is used by work details and crew liberty parties. The accommodation ladder, has an upper and lower platform that is connected by the ladder and supported by either a chain or wire bridle and bail hanging by a pendant.

Another method is the use of a metal bail shaped like an elongated upside down letter U which holds the ladder by a pendant rigged to the side of the ship or from a J-Bar davit. The lower platform of the accommodation ladder has additional parts that must be rigged. An H-Frame equipped with fenders is rigged to the outboard side of the lower platform. This H-Frame is where boats can come alongside to pick up or discharge passengers. The inboard side of the lower platform is fitted with ports called shoes, that when rigged hold the ladder in the proper position off the side of the ship. The shoes have pads attached to their ends to help prevent damage to the ship or the ladder. The lower platform also has turnbuckles, and in some cases, pendants to restrict the fore and aft movement of the ladder. The upper platform is supported by a brace known as a wishbone.

A single-sheave block is attached to the underside of the forward outboard comer of the upper platform. A line is rigged through this block which acts as a sea painter to keep a boat alongside in position with the accommodation ladder. A toggle between the strands of the line prevents the line from running up into the block and becoming inaccessible to a boat. There may be some accommodation ladders made of steel still in service, but for ease of handling, the Navy has changed to aluminum. When an accommodation ladder is secured for sea, everything is rigged in, disassembled in most cases, and stowed in brackets either on the rail or along a section of the superstructure. All of the smaller portable parts are stowed in a gear locker close to where the ladder is rigged. You should make sure all parts are on hand and that the toggle pins and bolts are seized with short sections of wire and attached to the ladder to prevent them from being lost over the ship's side.

The next step is to rig the upper platform. Remember to be careful in lining up the brackets when you are engaging the bolts. Many a hand injury has occurred from careless rigging operations. Once the upper platform is in place, the next step is to secure the ladder to it. Some ships have the ladder stowed against the rail. To attach this type ladder, you use a series of outriggers (arms swung out from the ship) to lay the ladder on and seat the ladder to the upper and lower platforms. On ships that do not have outriggers, the J-Bar davit can be used to support the ladder over the side to attach it to the upper platform. Another method is to use a ladder that engages pad eye. Depending on the type of the ship, rigging will vary. Now that you have the ladder attached to the upper platform, the lower platform and the H-Frame must be rigged. It is easier if the H-Frame is rigged to the lower platform while it is still on deck. Once the H-Frame and the lower platform are rigged on deck they must be worked over the side to attach to the ladder. This can be done by using the falls from the J-Bar davit or from some other attachment point. The ladder is now taking shape and nearly ready to lower. Rig the bail and bridle to the ladder and attach the wire pendant between the bail and the J-Bar davit. On some ships, the pendant is rigged between the bail and a pad eye alongside the ship.