Development
Davits were first devised in about 1600 for use byLifeboat types
Davits are designed to fit into deck spaces that the naval architects deemed necessary: * Radial (obsolete) – Hand powered davit. This type was used on the lifeboats of the RMS Lusitania. Each arm must be rotated out manually; uses manila rope falls. Goose-neck shape to the arm that is swung out. * Mechanical (obsolete) – This type is like the radial davit, but both arms are moved out at the same time using a screw system; uses manila rope falls. An example is the Welin Quadrant davit type used onComponents
; Liferaft: These can be enclosed, partially enclosed, or open. (There are pictures of these on the page already so no description is added) ; Frapping lines: These lines are used on all davits except the fixed and freefall davits. The frapping lines are used to pull the lifeboat over to the embarkation deck along with the tricing pendant to be loaded. ; Gripes: Ropes used to hold the lifeboat in the stored position while underway. ; Tricing pendants: Lines used to initially pull the lifeboat over to the embarkation deck so that the frapping lines can be connected. ; Falls: The wires which lift or lower the lifeboat are known as falls.Release mechanisms
There are three basic systems used to release the lifeboat from the davit. (Coast Guard Questions are for the Rottmer, On-Load releasing gear)Murphy, J. (2009). U.S. Coast Guard license examination preparation for the professional mariner . Wareham, Massachusetts: Academy Publishing Company. Retrieved from http://mdnautical.com/murphy-s-deck-officers-guides/7-murphy-s-deck-officer-study-guide-7-lifeboatmen-2009.html. ; On-load: For this style of release mechanism, the lifeboat can be released at any point from the davit. This type of system allows a lifeboat to be released when it is not in the water, whether this is because of the emergency or an accident. Because of this, during an evacuation the release mechanism must be watched to make sure there is not an accidental activation.Wankhede, A. (2010, december 22). Types of lifeboat release mechanisms & solas requirements for lifeboats. Retrieved from http://www.marineinsight.com/misc/maritime-law/types-of-lifeboat-release-mechanisms-solas-requirements-for-lifeboats/. ; Off-load: This release mechanism requires the weight (load) of the lifeboat to not be on the hook when it is released. This includes the Titanic-era Monomony hook design that requires someone to remove the hook from the lifeboat by hand. But this type also includes the hydrostatic system many lifeboats use now. For this, a float is raised up and engages the release once the craft is in the water to the right depth. ; Free-fall: This type of release mechanism is very basic. The (enclosed) lifeboat is on a ramp and slides down and off of the ship when engaged. This is done by pumping a lever that is inside the lifeboat by the pilot. If there is not enough hydraulic pressure to release the stop fall, a pump on the inside must be rotated to build up the hydraulic pressure to release the lifeboats stopfall hook. Once the stopfall hook (hook attaching the lifeboat to the davit that holds it to the ship) is released the lifeboat will slide off the ramp and into the water. This type of lifeboat is more common due to its quick deployment and ease of operation.Procedure
For all lifeboats using a roller gravity davit and Rottmer releasing gear, this is the procedure: # Make sure the davit tracks are clear of debris # Remove the lifeboat cover if applicable # Put in the lifeboat plugs # At this time the Rottmer releasing gear is checked to be secure. # Attach the sea painter to the bow of the ship. # Remove the gripes from the lifeboat. # Make sure the gripes preventing bar is free from the track. # Have the assigned brake man life the braking bar and lower the lifeboat to the embarkation deck. # Now that the tricing pendants have pulled the lifeboat in close, attach the frapping lines to the wire falls by passing them to a worker who is on the lifeboat. # Load the lifeboat. Load one person at a time and seat them so their weight is distributed between the two sides. # Have the brake man raise the lifeboat slightly so the workers can release the tricing pendants. # Brake man lifts bar and lowers the vessel into the water. # Operate the Rottmer releasing gear and release the davit on the crest of a wave. # If ship is sinking, pull toggle pin to release the sea painter from the ship.Suny Maritime College. (2011, 30 03). Lifeboat rotation . Retrieved from: http://www.sunymaritime.edu/media/documents/2011/3/30/Lifeboats - Work Equipment.pdf During this procedure, if the lifeboat has air-cooled engines start it at the beginning. If it has a water-cooled engine start the engine after the lifeboat is in the water.References
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