Home » , » the effect on the ship's center of gravity from docking, beaching, or grounding

the effect on the ship's center of gravity from docking, beaching, or grounding

EVALUATE shipboard stability by evaluating weight and moment considerations.


DESCRIBE initial actions required to preserve stability during an unintentional grounding with respect to ballasting, weight additions, weight shifts, and jettisoning.
CALCULATE the effect on the ship's center of gravity from docking, beaching, or grounding.
 DESCRIBE the hull stresses created and the appropriate actions to alleviate them when docking, beaching, or grounding.
 DESCRIBE and CALCULATE critical draft.
 DESCRIBE the contents and usage of the Docking Plan, Hull History, and Hull Penetrations Drawing when planning a drydocking.
 DESCRIBE the Docking Master's responsibilities to the ship, and the crew's responsibilities to the Docking Master regarding the addition, removal, or movement of weights while in drydock.
 DESCRIBE the problems associated with the unavailability of the ship's firemain system while in the drydock.
 STATE various compartments which must be sounded or observed during docking and undocking.

Situations in which drydocking may be required for your vessel:

OVERHAUL - Scheduled overhauls as established by CNO. The Fleet Modernization Program (FMP) has extended the overhaul cycle which varies from ship to ship, sometimes as long as 7 years.

EMERGENCIES - Serious hull damage following a collision, grounding, or battle damage. Often necessary to prevent the ship from sinking.

REPAIRS TO UNDERWATER FITTINGS - Any underwater work beyond the capacity of divers.

REMOVE FOULING OF THE HULL - Marine growth resulting in loss of speed, greater fuel consumption, and reduced plant efficiency. Due to funding, this is now the least common reason for drydocking. Navy Divers have the capability to clean the hull while the ship is still afloat.


1. Remind your CPOs that docking will be a good opportunity to overhaul or replace the skin valves in your division�s compartments.

2. Order any replacements for skin valves, be sure to get requisition numbers from Supply.

3. Route a memo to the MPA, AUX-O, ASWO, and WEPS so that they can do the same, but make it clear that they will be responsible for obtaining and replacing their own skin valves.

4. Ensure all jobs required to be done to your systems and gear are in the ship�s CSMP file so that they will be picked up in the contract.
The DCA is responsible to ensure the following services are written into the contract:
60 Hz, 450 VAC
250 VDC
CHT Connections
LP Air
Sea water service for diesel or A/C plant
All details are worked out in advance by the Docking Master, SUPSHIPS representative, and the Commanding Officer. Although the following details may not necessarily be your responsibility, they are considerations for docking:
1. Time and date of docking
2. Tugs and pilot to be used
3. Whether bow or stern enter the dock first
4. Proper conditions of list and trim
5. Handling of lines
6. Record of tank soundings before the ship is drydocked
7. Gangways to be used
8. Utilities to be furnished to the ship, such as electric power, steam, and water
9. Sanitary services to be provided
10. Garbage and refuse disposal facilities needed
11. Drydock safety precautions
12. Pumping plans or other instructions or operating directives for ballasting/deballasting floating drydock with or without ship in basin.

The Commanding Officer shall furnish the Docking Master or SUPSHIPS representative with the following information:
1. Place and date of last docking
2. Last docking position
3. Date and file number of last docking report
4. Number of days underway since last docking
5. General itinerary of ship movements (if not classified)
6. Paint history for last complete painting
7. History of touch-up painting
8. Ship weight distribution (including tank sounding
9. Offload supplies and hazardous stores
10. Lock screws in drydock position
11. Have 0� list and no excessive trim as per NSTM 997
1. Ensure Dry Docking Bill is completed.
(Details in OPNAVIST 3120.32A SORM pg. 6-65)
a. Provide last plan to Docking Officer
b. Ship has no List
c. Ship has less than 1% Trim
d. Retract all moveable hull appendages
e. Minimize Free Surface Effect - all tanks full or empty
f. Deliver list of all hull fittings below the waterline to the Docking Officer.
2. Hull Board will meets prior to both docking and undocking
a. Hull Board members - CHENG / 1st LT / DCA / OPS / ASWO
b. Review Docking plan, Hull History, and Hull Penetrations Drawings
1. Responsibility for the ship shifts from the Commanding Officer to the Docking Officer when the first part of the ship crosses the plane of the drydock sill.
2. Once the ship is positioned in drydock, dewatering of the dock begins. As the ship just touches down on the blocks, pumping is stopped. Divers will verify that the ship is properly resting on the blocks, and that the blocks are in the correct location. Upon verification, dewatering will continue.
3. When the dock is pumped dry, members of the hull board conduct an inspection with the Docking Officer.
a. Ensure ship is positioned properly in the dock
b. Ensure all shores in place
c. Note condition of propellers, rudders, overboards, intakes, and other projections
d. Note condition of zincs/cathodic protection anodes
e. Note details of any known or observed damage
4. NSTM 997 Section 2.11 requires the Docking Master to ensure adequate shoring and side blocking is installed to resist earthquake or hurricane forces.
1. DCA will maintain Dry Weight Log, a log of all weight shifts, additions, and removals in excess of 500 lbs.
2. Ensure all removed skin valves are replaced with blank flanges and that no liquids are discharged to the dock without consent of the Docking Officer.
1. Prior to undocking, the Hull Board will:
a. Inspect compartments and tanks below the waterline to verify tightness.
b. Ensure all valves below the waterline are secured.
c. Thoroughly inspect hull and projections.
d. Inspect drydock for chemicals or debris which might pollute the environment, clog intakes, or cause other damage as the ship is refloated.
2. The following spaces are continuously checked for flooding as the ship is refloated:
a. Spaces in contact with the keel and side blocks
b. Tanks and voids
c. Any space with external hull fittings

Write to me at marinenotes4u@gmail.com,283928@gmail.com.::MK::.

Facebook:Marine NotesTwitter:ACMWCTRss:ACMWCT
Marine Notes - MMD Exams India and Baiscs
URL: HTML link code: BB (forum) link code:
© Marine Notes - MMD Exams India and Basics (M&K Groups Ltd)


paper dewatering screw press said...

you have good knowledge regarding this firm. we are happy to see this. we will wait for next post.

Marine Notes said...

Thank you sir. sure.

Facebook Marine Notes
Twitter Marine Notes
Rss Marine Notes


Follow by Email