1. Impaired Stability

2. Objectives Definitions Addition of Topside weight
Loss of Reserve Buoyancy
Flooding (Solid and Partial)
Free Surface Effect
Fuel consumption
Running aground

3. Definitions Roll: Back/forth motion transversely
Pitch: Back/forth motion longitudinally
Yaw: Side to Side motion
List: Difference between Port and Stbd draft (ie: constant heel)
Trim: Difference between fwd/aft draft
(ie: constant pitch)
Center of Flotation: Point about which ship trims

4. Addition of Topside Weight
Some unauthorized/additional topside weight often occurs:
Icing, Ammunition, Cargo, etc.
Effects:
Reduction in reserve buoyancy
Upward shift in G
Reduction of GM (metacentric height)
Reduction of righting arms
Loss of freeboard from increased displacement
Decreased stability

5. Loss of Reserve Buoyancy
Can occur due to:
Poor maintenance
Failure to close fittings properly
Improper ballasting
Enemy action (torpedo, missile, mine, etc.)
If hole occurs above waterline, still reduces reserve buoyancy because of ship motion
Must restore watertight integrity ASAP

6. Three Categories of Flooding
With respect to boundaries:
Solid
Partial with boundaries intact
Partial in free communication with sea
With respect to height of ship:
Weight of flooding above G
Weight of flooding below G
With respect to ship’s centerline:
Symmetrical flooding
Off-center flooding

7. Solid Flooding Def’n: complete flooding of a compartment
Can occur only if compartment is vented
More likely to occur below waterline
Effects:
Increased draft (like added weight)
Decreased reserve buoyancy

8. Partial Flooding (Boundaries Intact)
Partial flooding means surface of flooding water lies between deck and overhead
Boundaries of compartment remain watertight
Affects stability of ship by:
Effect of added weight (high or low, on or off center)
Free surface effect (breadth of surface)

9. Free Surface Effect Compartment partially-filled with liquid
Surface of liquid tends to remain level as ship rolls/heels “free surface”
“Loose water” in compartment (not tank)
Causes reduction in GM stability

10. Free Surface Effect

11. Free Surface Effect
Causes shift in G as ship moves righting arm shrinks
Effect reduced by:
Installation of longitudinal bulkheads
“Pocketing”
Filling compartment solid

12. Partial Flooding (Free Communication with Sea)
Sea flows in and out as ship rolls
Most likely will occur when there is a large hole that extends above and below the waterline (or if compartment is vented)
Ship can assume a pronounced list as more water is taken on

13. Partial Flooding (Free Communication with Sea)
Water level in compartment tends to settle at sea level
Ship’s stability SIGNIFICANTLY affected by:
Added weight of water
Free-surface effect
Free-communication effect

14. Fuel Consumption
As fuel is consumed, a reduction in stability occurs due to removal of fuel from fuel tanks (tanks usually below G)
To ensure stability maintained, as storage tanks empty, they are filled with seawater
Seawater pumped into STORAGE tanks only (not SERVICE tanks)

15. Running Aground Running aground is BAD:
“Career limiting move”
Adversely affects stability
In general, don’t attempt to back off once grounded even more damage
Enough said

16. Any Questions?