## *Sample Free Surface Correction Problem SS American Mariner*

*Sample Free Surface Correction Problem SS American Mariner*

The SS AMERICAN MARINER is ready to bunker with drafts of FWD 15′-05″, AFT 21′-03″. After all bunkers are on board, soundings indicate the tonnages shown.

Use the white pages of The Stability Data Reference Book to determine the free surface correction.

- Answers:
- A. 1.05 feet Incorrect.
- B. 1.15 feet Correct.
- C. 1.25 feet Incorrect.
- D. 1.31 feet Incorrect.

**Step 1:**- Calculate Mean Draft.
- 15′-05″fwd + 21′-03″ aft = 36’08”
- Mean Draft: 36′-08″/2
- Mean Draft =
**18’04”** **Step 2:**- Using the
*Hydrostatic Properties*table (Sheet 3) for the SS American Mariner (White Pages), calculate the Total Displacement (S.W. Tons) for the vessel before loading bunkers with a mean draft of 18’04”.

**Step 3:**- Add up all the bunker totals for each tank. The sum of all bunkers equals
**3024.8 tons**.

- Add up all the bunker totals for each tank. The sum of all bunkers equals
**Step 4:**- Add the displacement of the vessel before loading the bunkers and the sum of all the bunkers to find the ship’s final displacement.

- 12,000 tons + 3024.8 tons =
**15024.8 tons**

**Step 5:**- Refer to the
*Table for Free Surface Correction and Tank Capacities*(Sheet 4) to calculate the free surface moment for each tank. On the S.S. Mariner , a tank is considered FULL if the tank is at least 97% full. Any quantity less than 97% full or an empty tank is considered SLACK.

- Refer to the

- In the column
*F.O. Tons*under*Tank Capacity*, the table gives you the capacity of each tank at 97% full. This is the column you will compare your loaded bunkers in each tank with to verify if a tank is considered FULL or SLACK. For example, DB 1 CL is loaded with 48.2 tons of bunkers. The tank capacity at 97% for D.B. 1 CL is 48.2 tons. Therefore, the tank is considered FULL and its free surface correction is 67. Conversely, D.B. 4 CL is loaded with 208.6 tons of bunkers. The tank capacity at 97% for D.B. 4 CL is 224.1 tons. Since 208.6 tons is less than 224.1 tons then D.B. 4 CL is considered SLACK.

*Now find the free surface moment for each tank.*

*Now find the free surface moment for each tank.*

- Next, find the total sum of free surface moment which equals
**17,309 foot tons**. **Step 6:**- Find the free surface correction in feet by dividing the total free surface moment by the final displacement of the vessel.
- FS(corr) = 17,309 foot tons/15,024.8 tons
- FS(correct answer) =
**1.15 feet**

*There are 19 questions in the online study on this subject under.*

- Deck Department
- All Deck Examination Questions As of March 24, 2014 Regulations
- Deck General – Safety
- Stability and Trim Problems With ST-Tables
- Free Surface Correction, Mariner Class

- Stability and Trim Problems With ST-Tables