Lesson 4.3 Loose Water G B M B1 G2 Z Z2 G3 Z3 So far the stability that we talked simplified all equations assuming that water does not shift. Reality would tell us that this is not true. Allowing a liquid to move about in a ship in a seaway is a great detriment to the stability of your ship.

SAILOR’S CREED “ I am a United States Sailor. I will support and defend the Constitution of the United States of America and I Will obey the orders of those appointed over me. I represent the fighting spirit of the Navy and those who have gone before me to defend freedom and democracy around the world. I proudly serve my country’s Navy combat team with Honor, Courage, and Commitment I am committed to excellence and fair treatment of all.” Honor, Courage, and Commitment as we have have just seen were attainable virtues, back then as they are now, that have been demonstrated at the highest level through out our history and are on display right now at every watch station around the world. Our Navy’s history is rich and full of displays of valor, sacrifice, and honorable conduct in dangerous, difficult and even hopeless circumstances. These virtues and values have prevailed. Possibly one of the leading reason our Sailors today, do not identify with our Core Values more quickly is our shallow sense of our heritage, history and traditions. 1

CREED OF THE UNITED STATES COAST GUARD “ I am proud to be a Unites States Coast Guardsman. I revere that long line of expert seamen who by their devotion to duty and sacrifice of self have made it possible for me to be a member of a service honored and respected, in peace and in war, throughout the world. I never, by work or deed, will bring reproach upon the fair name of my service, nor permit others to do so unchallenged. I will cheerfully and willingly obey all lawful orders. I will always be on time to relieve, and shall endeavor to do more, rather than less, than my share. I will always be at my station, alert and attending to my duties. I shall, so far as I am able, bring to my seniors solutions, not problems. I shall live joyously, but always with due regard for the rights and privileges of others. I shall endeavor to be a model citizen in the community in which I live. I shall sell life dearly to an enemy of my country, but give it freely to rescue those in peril. With God’s help, I shall endeavor to be one of His noblest Works… “ I am proud to be a Unites States Coast Guardsman. I revere that long line of expert seamen who by their devotion to duty and sacrifice of self have made it possible for me to be a member of a service honored and respected, in peace and in war, throughout the world. I never, by work or deed, will bring reproach upon the fair name of my service, nor permit others to do so unchallenged. I will cheerfully and willingly obey all lawful orders. I will always be on time to relieve, and shall endeavor to do more, rather than less, than my share. I will always be at my station, alert and attending to my duties. I shall, so far as I am able, bring to my seniors solutions, not problems. I shall live joyously, but always with due regard for the rights and privileges of others. I shall endeavor to be a model citizen in the community in which I live. I shall sell life dearly to an enemy of my country, but give it freely to rescue those in peril. With God’s help, I shall endeavor to be one of His noblest Works… A UNITES STATES COAST GUARDSMAN. ” Honor, Courage, and Commitment as we have have just seen were attainable virtues, back then as they are now, that have been demonstrated at the highest level through out our history and are on display right now at every watch station around the world. Our Navy’s history is rich and full of displays of valor, sacrifice, and honorable conduct in dangerous, difficult and even hopeless circumstances. These virtues and values have prevailed. Possibly one of the leading reason our Sailors today, do not identify with our Core Values more quickly is our shallow sense of our heritage, history and traditions. 1

We must walk before we can run! Lets review HW problems #1, #2, #3 and Lesson 4.2

References NSTM 079 Volume 1 NTTP 3-20.31 Damage Control Book, section II (a)

ENABLING OBJECTIVES Explain why FSE impairs stability. Compute FSE. List methods to reduce FSE. Explain why FCE impairs stability. Compute FCE. Describe pocketing, surface permeability, size of hole, and venting on FSE and FCE. Correct stability curve for FSE and FCE.

CLASS TOPICS 1. Free Surface Effect 2. Example 3. Free Communication Effect 4. Example

FREE SURFACE EFFECT G B M B1 G B M B1 G B M B1 G B M B1 G B M B1 G B M Z Free surface is the surface of any liquid partially filling a compt which tends to remain horizontal as the ship rolls. Q: Causes? Flooding Fuel tanks Lube oil tanks Water tanks Etc

FREE SURFACE EFFECT GZ2 = GZ3 G B M B1 G2 B1 G2 G B M G B M B1 G2 G B As we heel over, the water will NOT stay level. Principles of FSE: A)Shifting wedge of water. Athwartships shift of weight Results in a shift of ship’s KG Greater Inclination results in a larger wedge and a greater shift in KG GZ2 = GZ3

B M B1 G G3 The ever changing position of KG presents a problem in computer a lost in righting arms. Solution: Extend the lines of action of force of gravity upward. The point at which all of the lines intersect is known as the virtual position of “G” (for small angles of heel).

B M B1 G G3 GG3 To better calculate this we move G up to G3 and call it a “Virtual Rise in the KG” since it doesn’t actually move. The reduction in righting arms determined for each actual shift of G will be the same as if G rose to the virtual position.

FREE SURFACE EFFECT B3 x L FSE = 12 x 35 x Wf MOMENT OF INERTIA = SHIP'S DISPLACED VOLUME B = BREADTH OF COMPT L = LENGTH OF COMPT Wf = SHIP'S DISPLACEMENT

POCKETING - SHALLOW Some ways to limit Free Surface Effect

POCKETING - ALMOST FULL This is why most tanks are kept full or empty, we try to minimize the amount of half full tanks.

POCKETING (NO POCKETING EXISTS)

SURFACE PERMEABILITY This can be engines, machinery for flooding. Also, baffle plates in a fuel tank

SLUICE VALVES - Closed

SLUICE VALVES - Open

FREE SURFACE EFFECT Independent of the depth of the liquid Greater w/ increased length and width of the compartment Increases as draft decreases (de-ballasting) Can be reduced by pocketing FSE is independent of amount of water (that affects weight additions/removals) Increases as draft decreases because of lost of displacement. Remember that ship’s displacement is in the denominator so if that decreases…the FSE increases. The equation calculates worse case scenario, does not take into account Pocketing and permeability.

CLASS TOPICS 1. Free Surface Effect 2. Example 3. Free Communication 4. Example

Wo = 3500 LT 25 FT FWD AFT PORT STBD 4 FT Answer= .46 FT 30 FT FSE?

FSE = B3 x L 12 x 35 FT3/LT x WF FSE = (30 FT)3 x 25 FT 12 x 35 FT3/LT x 3585.71 LT FSE = 675000 FT4 = 1505998.2 FT3 .45 FT

CLASS TOPICS 1. Free Surface Effect 2. Example 3. Free Communication 4. Example

FREE COMMUNICATION EFFECT FREE COMMUNICATION EFFECT G B M

FREE COMMUNICATION EFFECT FREE COMMUNICATION EFFECT G B M

FREE COMMUNICATION EFFECT G B M G2 G4 B1 G5 Z5 G3G5 G3 Z4

FREE COMMUNICATION EFFECT FCE = B x L x Y2 35 x Wf B = BREADTH OF COMPT L = LENGTH OF COMPT Y = DIST FM SHIP C/L TO COMPT COG. Wf = SHIP'S DISPLACEMENT FREE COMMUNICATION EFFECT

FREE COMMUNICATION EFFECT (All 3 must exist) COMPARTMENT OPEN TO THE SEA COMPARTMENT PARTIALLY FLOODED COMPARTMENT OFF-CENTERLINE OR “UNEVEN” ABOUT THE CENTERLINE

COMPARTMENT OPEN TO SEA COMPARTMENT PARTIALLY FLOODED Y = 0 NO F.C.E. .

Free Communication Effect Size of the hole will reduce FCE. (Formula assumes entire skin of ship is “open to sea”) Venting will reduce FCE. (More air transfer = more water “communicating” into the compartment.) Increases as draft decreases (de-ballasting) Can be reduced by pocketing FSE is independent of amount of water (that affects weight additions/removals) Increases as draft decreases because of lost of displacement. Remember that ship’s displacement is in the denominator so if that decreases…the FSE increases. The equation calculates worse case scenario, does not take into account Pocketing and permeability.

CLASS TOPICS 1. Free Surface Effect 2. Example 3. Free Communication 4. Example

y = 20 ft – 14.5 ft y = 5.5 ft 40 ft Wo= 2880 LT L = 28 FT Depth = 4 ft B = 29 FT 40 ft 20 ft y = 20 ft – 14.5 ft y = 5.5 ft 28 FT 14.5 ft Overall effect? New Wf=2880+92.8=2972.8 FSE= .55 ft Y=5.5 FT FCE= .24 29 FT wFLOODING = 28 FT * 29 FT * 4 FT 35 FT3/LT wFLOODING = 92.8 LT WF = W0 + wFLOODING = 2972.8 LT

B x L x (y)2 35 FT3/LT x WF .24 FT FCE = FCE = 24563 FT4 104048 FT3 29 FT x 28 FT x (5.5 FT)2 35 FT3/LT x (2880 LT + 92.8 LT) FCE = 24563 FT4 104048 FT3 FCE = .24 FT

Quiz… Why does FSE impair stability? ANS: Horizontal weight shifts off centerline cause a “virtual rise” in G, reducing GM. Factors that reduce FSE? ANS: Compartment size, pocketing, baffle plates, surface permeability, sluice valves, venting. Which variable is the “determining factor” in the FCE equation? ANS: “Y” the distance from the ship’s centerline to the compartments center… it is squared.

Quiz… What three factors must be present for FCE to exist? ANS: 1) Off centerline or Uneven about centerline. 2) Open to the sea 3) Partially flooded.

Instructor will now… Assign Practice Problems for lesson 4.3 (Stability Problems #4, #7. Try problems #8, #11) Read Student Guide!! Homework # 2 Due end of class TODAY!