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Ship Stability Teacher’s Manual
Contents
• Teacher’s Instructions
• Assessment Sheet
• Students Handouts
• Work sheets
• Answer Key
Marine Kit – 3
This activity was developed under a grant from National Shipbuilding Research Program (NSRP)
SBRCD SHIP STABILITY
Teacher’s Instructions This activity deals with the effect of center of buoyancy on ship’s stability, finding the weight of displaced water by foam model and comparing the draft of model in saline and fresh water. Kit Contents
• The kit contains a foam model, ruler, weights (washers-16), and a marker. • Students additionally need calculator, water and salt.
Set Up • This activity requires two class periods. (Day – 1 and Day – 2) • Answer key is included in the kit for the teacher.
Day – 1 • Please use the power point presentation for day -1 activity. (10 to 15 min) • Identify 3-4 students to help you with the activity. • Day-1 activity involves finding center of buoyancy and weight of displaced
water.( 40 – 45 min) • Work sheets are provided in the kit for calculations. Make additional copies of
student worksheets as needed. • Foam models are delicate. Students should be cautioned not to pierce or damage
the foam models during the experiment. • At the end of activity, please wipe the foam model and the tank. Collect all parts
and place them back in the box. • Markers are provides to mark the location of center of buoyancy. Please ask
students to wipe the mark using moistened paper towel so that next group of students can repeat the experiment.
Day – 2 • Please use the power point presentation for day - 2 activity. (10 to 15 min) • Identify 3-4 students to help you with the activity. • Day-2 activity involves comparison of draft in fresh and saline water. (40 –
45min) • For the second day, salt packet is provided. Salt must be dissolved uniformly in
the water. • At the end of the activity, please wipe the tank completely and remove any
remaining salt. • Check the kit contents for any missing or damaged part and put the contents back
in the box. • Use the assessment sheet to assess the performance of each group. MarineTech Project Ship Stability Lean Institute, ODU August 2008
1
Group No:
Names
1)
2)
3)
4)
Poor Fair Good Very Good Excellent
Quality Characteristics 1 2 3 4 5
Was the water filled to the accurate level?
Was the center of bouyancy correctly marked?
Is the volume of the water displaced correctly calculated?
Is the weight of the water displaced correctly calculated?
Was the understanding about the effect of salinity on the buoyancy adequate
Date(mm/dd/yy):
Ship Stability Assessment Sheet
This assessment sheet is to be used to evaluate of Stability calculations
MarineTech Project Ship Stability Lean Institute,ODU AUG 2008
Total Points
MarineTech projectAlok K. Verma 08/08
SHIP STABILITY
STUDENT HAND OUTS
Marine Kit – 3
MarineTech projectAlok K. Verma 08/082
Day 1: Part - A, Center of Buoyancy ( CB)
1. Fill the tank with water till
marked line. Place the model in
the tank. Check the level of
model from all sides.
2. Place the weight (three washers)
on foam model at any point and
check whether model is level with
water line.
Model not parallel to water level
MarineTech projectAlok K. Verma 08/083
Day 1: Part - A, Center of Buoyancy (CB) ( Contd.)
3. Move the weights until the
foam model is level with respect
to the water line.
4. Mark the circle inside washer
with a pencil. Remove the
washers and take the foam
model out of tank.
Model parallel to water level
MarineTech projectAlok K. Verma 08/084
Day 1: Part - A, Center of Buoyancy (CB) (Contd.)
6. Note down the X and Y
coordinates of the CB on
X-Y grid of the model.
5. Mark the center of circle
as CB.
MarineTech projectAlok K. Verma 08/085
Day 1: Part – B, Weight of Displaced Water
7. Place the foam model in
the water tank. Check the
level of model from all sides.
8. Place weights at the CB until the
model is submerged such that only
top surface remains above water.
(Make sure there is no water on top
surface). Count the washers.
Water Level
MarineTech projectAlok K. Verma 08/086
Day 2 : Effect of Salinity
1. Fill the water till marked
line. Mix two cups of salt in
the tank.
2. Place the same number of
washers at the CB (as in the
previous experiment), and
observe the change in draft.
Water Line
Water Level Level difference in red lines
indicate the draft change
MarineTech projectAlok K. Verma 08/087
Work Sheet
1. h1 = cm, h2 = cm, b1 = cm
2. A1 = 0.5 * h1 * b1 = sq.cm
3. A2 = h2 * b1 = sq. cm
4. Area = A =A1 + A2 = sq. cm
5. Thickness of foam model = cm
6. Thus, Volume(V) of water displaced by the model :
V = A * Thickness = cu. cm
7. Weight of water displaced by the model
( Density of water = 1000 kg/m3 )
= Volume * Density of water
= kg b1
h2
h1A1
A2
MarineTech projectAlok K. Verma 08/088
Work Sheet ( Contd.)8. Coordinates of Center of Buoyancy: XB = cm, YB = cm
9. Number of washers required to find weight of displaced water = N =
(Weight of each washer = 0.030 kg or 0.041 kg)
10. Weight of washers = N * = kg
(Compare the answers for weight of washers and the weight of displaced water. Are they equal ? )
Note: You can either have washers of Type-1 / Type-2 in your Kit.
Type-1 Type-2
Outer Diameter (O.D) = 50 mm Outer Diameter (O.D) = 44 mm
Inner Diameter (I.D) = 21 mm Inner Diameter (I.D) = 18 mm
Weight = 0.041 kg Weight = 0.030 kg
Answer key for Work Sheets
Marine Kit - 3
SHIP STABILITY
This activity was developed under grant from National Shipbuilding Research Programme(NSRP)
Marine Tech Project Shipyard Operations Lean Institute, ODU August 2008
1
Ship Stability Answer Key
1. h1 = 7.6 cm, h2 = 17.7 cm, b1 = 12.7 cm
2. A1 = 0.5 * h1 * b1 = 48.26 sq.cm
3. A2 = h2 * b1 = 224.79 sq. cm
4. Area = A =A1 + A2 = 273.05 sq. cm
5. Thickness of foam model = 1.90 cm
6. Thus, Volume(V) of water displaced by the model :
V = A * Thickness = 518.795 cu. cm
7. Convert units from cu. cm to cu. m
1cu. cm = 0.000001 cu. m
521.21 = 0.00052 cu. m
b1
h2
h1A1
A2
2
Answer Key ( Contd.)8. Weight of water displaced by the model
( Density of water = 1000 kg/m3 )
= Volume * Density of water
= 0.52 kg
9. Coordinates of Center of Buoyancy: XB = 6.6 cm, YB = 11.5 cm
10. Number of washers required to find weight of displaced water = N = 12 or 17
(Weight of each washer = 0.030 kg or 0.041 kg)
11. Weight of washers = 12 * 0.041 = 0.492 kg
OR
Weight of washers = 17 * 0.030 = 0.51 kg
(Compare the answers for weight of washers and the weight of displaced
water. Are they equal ? )