Future Fleet
Science Topics: Buoyancy, Density and Volume
Future
Fleet
SESSION ONE
History of Failed Ships
History of Failed Ships
• What is the economic cost of a failed ship
design?
Student Responses
History of Failed Ships
• What is the human cost of a failed ship
design?
Student Responses
History of Failed Ships
• How can the tragic losses in the article be
prevented?
Student Responses
History of Failed Ships
• Is it possible to know how much a ship will
cost before you build it?
Student Responses
History of Failed Ships
• Can an unsinkable ship be designed?
Student Responses
History of Failed Ships
• Is it possible for a tragedy at sea to happen
today, even with current technology?
Student Responses
Lets Explore
Exploration Teams
• Assigning the teams
• Roles
– Task manager
– Activity recorder
– Life Line
– Evaluator
Task manager
• Keep group members
focused
Activity recorder
• Records what the group
does and what
questions the members
have
Life Line
• Can leave the group to
seek help
Evaluator
• Judge the
effectiveness of the
group
• Report back only to
the group
The Stations
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How Metal "Boats" Float (5 min)
Liquid Density and Lava Lamp (5 min)
Soda Can Pirouette (5 min)
Students should move to their teams
now and begin the exploration
TIME IS UP
Please return to your seats
REPORT
• Each group should now report on the
following:
– Name one thing you learned that has not been mentioned yet
Student Responses
Definitions and Calculations
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Density
Displacement Mass
Buoyancy
Center of Gravity
Center of Buoyancy
Metacenter
Density
- The degree of compactness of a substance
- Mass per unit of Volume
D=M/V
Solve the equation for mass
M=D x V
Mass can now be calculated
The Density of Water
Density is influenced by depth, temperature,
and salinity.
Look at the Salinity Map
Salinity Map
Look at the Temperature Map
Temperature Map
Displacement Mass
The mass of a fluid (as water)
displaced by a floating body (as
a ship) of equal mass
To stay afloat
A 460 mega
kilogram
ship
Needs to
Displace
460 mega kilograms of water
The Calculation of Displacement Mass
1) Find the density of water of operational area
Density is influenced by depth, temperature, and salinity
We will use about 34 PSU*
Salinity as an
operational area
We will use about
30 degrees Celsius as
an operational area
Salinity Map
Temperature Map
At 20m depth the density will be
1.021 g/cm3
*PSU * Salinity is measured by conductivity (how easily electricity flows through a seawater sample).
The Calculation of Displacement Mass
2) Find the volume of water being displaced
Take the cross sectional area height x width
30m
30 m x 5m x 3m
and multiply by the 3rd dimension
to find volume
5m
3m
This gives us a Volume of 450 m3
The Calculation of Displacement Mass
3) Find the displacement mass M = V x D
Volume of Water (cm3) x Density (g / cm3)
(450 m3 x 1,000,000 cm3 / m3 ) x 1.021 g/cm3
459450000 g
Weight vs. Mass
- Weight is a force
- Force in general is mass times acceleration
So the volume can displace a mass of 459450000 grams
or a weight of
459450000 g x (1kg/1000 g) * 9.8 m/s2 =
4,502,610 N
or
459450000 g x (1kg/1000 g) * 2.2lbs/kg=
1,010,790 lbs or 505.4 Tons
Buoyancy
What is Buoyancy?
Buoyancy is the upward
force that a fluid exerts
on an object less dense
then itself.
As mass is added, the boat displaces
more water until the weight of the
displaced water equals the weight of
the boat; then the boat sinks.
Archimedes's principle.
Put picture of floating boy here
An object immersed
in a fluid is buoyed up
by a force equal to
the weight of the fluid
displaced by the
object.
Summary of Buoyancy and Displacement
30m
5m
3m
A 500 Ton ship needs to displace a
volume of 450m3 to avoid sinking
Displacement of irregular shapes
Use graph paper
to approximate the
cross sectional area
Then find the
displacement mass
Center of Gravity
What is the Center of
Gravity?
The center of gravity is
the geometric property
that represents the
average location of the
weight of an object.
We can balance the
scale by moving the
fulcrum to the center
of gravity.
How do we find the Center of Gravity?
1) Hang the object from a
point
2) Hang a weighted
string from the point
and when it comes to
a rest draw a line
3) Repeat with another
point on the shape
Center of Buoyancy
• Is the center of gravity of the displaced water
• The center of buoyancy changes as the ship rolls and
pitches
• The balance between center of buoyancy and center
of gravity affects stability of the ship
Metacenter
Ship
Water
Center of Gravity
Center of Buoyancy
Ship rolled at
a small angle
Line of force for new center
of buoyancy perpendicular
to water line
New center of buoyancy
The intersection of the two lines
of force form the metacenter
M
G
The distance from the
metacenter (M) to the
center of gravity (G) is
called the metacentric
height (GM).
Metacenter
• A positive GM is needed to make a stable ship
• The higher the GM the more stable the ship
• The higher the GM the faster the ship will
right itself. If this number becomes too high
the ride will become rough.
Elaborate
• Work in your teams to
come up with general
guidelines for ship
design.
Exit Ticket
• Find the displacement of mass of a ship
segment with cross sectional dimensions of
30m by 8 m and a length of 10m.
Student Responses
SESSION TWO
Build a Prototype
The Littoral Class
• Future Ships of the Navy
The Littoral Class
• Why did the Navy use two different designs?
Student Responses
The Littoral Class
• What need is the Navy trying to address?
Student Responses
The Littoral Class
• What aspects of the design of the ships
address the needs of the Navy?
Student Responses
The Littoral Class
• Why do you think using all new 21st century
technology was important to these features?
Student Responses
LCS and Pirates
Click me to see Somalia
Click me
To see
video
The Littoral Class
• How could the LCS class ships help support
operations in the region?
Student Responses
The design requirements
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Length must be 128 cm
Width 32 cm
Displacement depth 4.3 cm
Hull shape up to the
designers but ship must be
stable and must displace its
weight in water
Design Time
Planning and calculations
Build Time
25min
35min
Evaluate
• The students will work in their design team on a brief
description of their prototype.
• In this description the students should address the aspects of
their prototype that are most closely related to a real ship
(displacement and buoyancy).
• Students should then give themselves a confidence rating.
This should represent how successful the ship will be in a full
scale prototype. Focusing only on aspects related to a real
ship, students should answer the question - “Is the design of
their prototype worth spending several million dollars to test
at full scale?”
• The students should answer the question - “Is the design of
their prototype worth spending several million dollars to test
at full scale?”
SESSION THREE
Testing our Design
Presentations
• Each group will have 3 minutes to present
their design to the class using the evaluation
from Session 2
Evaluation of design
• Each team will put their prototype in the water tank
and have it tested by the instructor.
• All students will record data on a rubric for each
prototype.
• There are three categories:
o Percentage error between predicted water line and actual
water line (tank can have dye or food coloring in it to help
denote the actual water line for measurement)
o Stability test under wave creation. Three levels of intensity
for waves should be tested by dropping a weight in the
water a short distance from the ship.
o Overall design appeal and creativity – this is subjective
Improving on design
Teams are to go back together and reevaluate
their calculations to determine the following:
• Explanations for percentage error
• Stability of their prototype and what
improvements could be made
• If they were to make another prototype what
would they do differently?
The Littoral Class
• We looked at stability and buoyancy. What
other variables might have to be addressed in
building of a prototype?
Student Responses
The Littoral Class
• How will designing versatile and flexible ships
prepare us to handle the future?
Student Responses
The Littoral Class
• Given the safety concerns about some
modern cruise ships, how might one prevent
future accidents like the Costa Concordia?
Student Responses
Congratulations
on finishing
your designs of