CD&RB Report Ammended

7/27/2019 CD&RB Report Ammended

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STUDY OF THE EXISTING DESIGN AND FABRICATION OF

PROTOTYPE UNDERWATER SCOOTER FOR MULTI-

PURPOSE UNDERWATER OPERATIONS BY SSG (N) AND

PAK MARINES

CONCEPT DESIGN AND REVIEW BOARD

REPORT

Group members Supervisor

S/LT BILAL ASIF PN 7902(Group Leader)

S/LT SULAIMAN AMJAD PN 7891

S/LT SOHAIL KHAN PN 7895

S\LT OWAIS MALIK PN 7907

CAPTAIN DR. NADEEM AHMED PN

Pakistan Navy Engineering College

National University of Sciences and Technology


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Table of ContentsAbstract .......................................................................................................................................... 4.

Aim of project ................................................................................... Error! Bookmark not defined.

Cost reduction factor ..................................................................... 4Error! Bookmark not defined.

Problem Statement .......................................................................... Error! Bookmark not defined.

Scope................................................................................................. Error! Bookmark not defined.

Introduction.................................................................................... 6Error! Bookmark not defined.

Historical Background ...................................................................... Error! Bookmark not defined.

Literature Review ........................................................................................................................... 7.

Crane operated: .......................................................................... 7Error! Bookmark not defined.

underwater History in military:..................................................... Error! Bookmark not defined.

The RotterDam Boat ..................................................................... Error! Bookmark not defined.

Underwater chariots................................................................................................................... 8.

Modern Forms Of Underwater Vehicles.......................................... Error! Bookmark not defined.

The Underwater scooter............................................................... Error! Bookmark not defined.

Future Concept in Underwater Scooter........................................... Error! Bookmark not defined.

The Underwater Car.................................................................. Error! Bookmark not defined.

3- seater submersible fighter plane ......................................... Error! Bookmark not defined.

Underwater Scooter In Pakistan ........................................... 11Error! Bookmark not defined.

Principles Of Underwater Scooter ................................................... Error! Bookmark not defined.

Archimedes principle ................................................................ Error! Bookmark not defined.

Explanation ............................................................................... Error! Bookmark not defined.

Positive buouancy ................................................................................................................. 13.

Negative Buouyancy ................................................................. Error! Bookmark not defined.

Neutral buoyancy...................................................................... Error! Bookmark not defined.

Stability ................................................................................................................................. 14.

Pressure .................................................................................... Error! Bookmark not defined.

Drag....................................................................................... 15Error! Bookmark not defined.

Design Specifications.................................................................................................................... 17.

Material Selection: ....................................................................... Error! Bookmark not defined.

Steel .............................................................................................. Error! Bookmark not defined.


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Aluminum...................................................................................... Error! Bookmark not defined.

GFRP.............................................................................................. Error! Bookmark not defined.

Hull Design .................................................................................... Error! Bookmark not defined.

Advantages of cylinderical Hull..................................................... Error! Bookmark not defined.

Disadvantages............................................................................... Error! Bookmark not defined.

Weighted and Rated Matrix............................................................. Error! Bookmark not defined.

Design requisites .............................................................................. Error! Bookmark not defined.

Hull Closing System.................................................................................................................... 28

Water Tight Propeller Shaft .......................................................... Error! Bookmark not defined.

Water Tight External Control .................................................................................................... 24.

Gaskets And Sealing Components ........................................................................................... 24.

Project Risk Statement................................................................... Error! Bookmark not defined.

Cost ................................................................................................... Error! Bookmark not defined.

Appendix - A (Bibliography)......................................................................................................... 25.

Appendix B (GANNT CHART) ......................................................... Error! Bookmark not defined.

Appendix C (SOR)........................................................................... Error! Bookmark not defined.


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List of figures:

Figure 1: Crane operated UWV-Courtesy: BLUE FINS ROBOTICS

Figure 2: first submerged vehicle-William Bourne inventions: Wikimedia commons

Figure 3: the Rotterdam boat-Courtesy: The Navy Times Book of Submarines

Figure 4: the PAPIN design 1-The Navy Times Book of Submarines

Figure 5: the PAPIN design 2-The Navy Times Book of Submarines

Figure 6 underwater chariot-Courtesy: military history journal

Figure 7: underwater scooter with seat-Courtesy: SEABOB underwater scooter

Figure 8: underwater scooter without seat-Courtesy: SEA DOO underwater scooter

Figure 9: cross sectional view of underwater scooter-SEABOB underwater scooter

Figure 10: underwater multipurpose car-Courtesy: Rinspeed concept car

Figure 11: 3-seater underwater plane-Courtesy: Necker Nymph

Figure 12: floating objects buoyancy-Courtesy: fluid mechanics book by Munson

Figure 12: Archimedes principle-Courtesy: hyper physics library

Figure 13: buoyancy explanation-Gsu.edu, Buoyancy, 2000

Figure 14: positive buoyancy-Gsu.edu, Buoyancy, 2000

Figure 15 cylindrical hull-Courtesy: SEABOB underwater scoter

Figure 16 3D CAD model (GRAB CAD)

List of tables:

Table no.1 Material feature requirements

Table no.2 weighted matrix

Table no.3 Rating matrix


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Abstract

The underwater exploration is always a fantasy for the world above the water line. For thousands of

years man has shown an inborn need to explore, conquer, and experience the unknown.

We have to design and fabricate an underwater scooter for multipurpose underwater operations by PAK

NAVY and for recreational purposes too. For this we have studied and referred to various books of

design and analysis of structure and material selection.

By the study of these books we learned about the material selection for fabrication and best possible

designing of body. Apart from these we also have learned the fluid behavior and differential analysis of

fluid flow.

Several meetings with CAPT. DR. NADEEM AHMED PN were done to learn about the factors that would

be considered in designing and fabrication of underwater scooter.

The underwater scooter is relatively a new concept in diving industry. The need of speed in diving has

always remained a problem for divers as diver has to carry breathing apparatus and equipment

underwater. This high load always reduces his speed and results in quick exertion and high consumption

of oxygen by diver.

Increase in underwater range is always a major issue for divers. Range is restricted by the amount of

breathing gas that can be carried, the rate at which that breathing gas is consumed under exertion. In

order to cater this problem we are committed to design a low cost underwater scooter that can be used

for certain depths. This will not only help in increasing the speed underwater but also the overall

efficiency in underwater operations.

1. Aim of project:The aim of this project is to design and fabricate an underwater scooter that can operate efficiently at

desired water depths and must be compatible and operational in high tide and current.

1.1 Cost reduction factor:According to our survey of local and international market, it is observed that prices of underwater

scooter are considerably high and are out of reach for a common person. That why our group team

decided to fabricate an underwater scooter that will be fully functional, highly maneuverable and of

reduced cost. This reduced cost factor is making this project different and first of its kind in PAKISTAN.


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The basic objectives for this project are as follows:

1.2 Problem statement:

The importance and requirement of oceanography has taken utmost importance in the field of marine

biology, chemistry, geology and engineering. The oceanographers compile and study this data to

investigate ecology of marine environment, chemical interaction of the ocean and marine physics.

In Pakistan navy the divers perform a variety of diving salvage operations and special diving duties,

execute search and rescue missions, support military and civilian law enforcement agencies, serve as thetechnical experts for diving evolutions for numerous military Special Operations units and carry out

routine ship maintenance, including restoration and repairs. For this we need equipment that can carry

diver to his mission area quickly and that result in low rate of consumption of oxygen by diver.

1.3 Scope:

The scope of this project is to provide Pakistan Navy the ability to transport diver and his equipment tothe mission area quickly and covertly. It will provide great support in search & rescue and lifesaving

operations.

Design Analysis Fabrication


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Introduction:

The underwater scooter, as an electromechanical vehicle that carries a diving person underwater and

have certain characteristics and features derived from precise design and construction so as to use all

means to avoid any type of injury to the user and damages to property.

An underwater scooter is provided with an electric motor driven by battery enclosed in the watertight

vessel used to drive the propeller, or a fan device that transmits power by converting the energy

produced by the fan's rotation into a reaction force, called thrust. (Courtesy: CONSTRUCTION STANDARDS FOR

UNDERWATER SCOOTERS by Marco Segatto Alessandro Fenu)

Literature review:

2. Historical Background:

Back in the 16th century people began to use diving bells supplied with air from the surface. This was

probably the first effective means of staying under water for any length of time. The bell was held

stationary, its bottom open to water and its top portion containing air compressed by the water

pressure. The diver standing upright would have his head in the air. He could stay until the air in the bell

was no longer breathable due to carbon dioxide build-up.

There have been many steps in the evolution of diving and many great inventions, but the major

breakthrough came in the guise of SCUBA (Self-Contained-Underwater-Breathing-Apparatus). Using fin

power the diver has freedom to move about and discover the underwater realms without interference

of surface supplied air. Open circuit SCUBA is the mode most common in recreational diving, expelling

the expired air into the water creating bubbles and avoiding carbon dioxide build-up.

Many transformations are done in underwater breathing apparatus but less attention paid towards

underwater speed increasing equipment. There are many companies manufacturing underwater

scooters right now. (2. Brief History of Diving, From Antiquity to the Present 1997)


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2.1 Crane operated underwater vehicle:

The history of underwater scooter is not very old as this advance

concept came from a small purpose-built boat engine, used by

divers to propel them under water. This is needed when divers

have to cover large distances under water. Prior to use, this

vehicle hangs from a crane at a port and has to be lowered to the

water. The crane is controlled by a computer.

2.2 Underwater vehicle history in military:

The first ever underwater vehicle was made and designed by WILLIAM BOURNE in 1580, an English

scientist who also described the concept of submerged vehicle.

Bourne first offered a lucid description of why a ship floats by displacing its weight of water. In other

words, decrease the volume to make the boat heavier than the weight of the water it displaces, and itwill sink. Make it lighter, by increasing the volume, and it will rise. (3. The inventions of submarines- submarine

history.)

Figure 1: Crane operated UWV

Courtesy: BLUE FINS ROBOTICS

Figure 2: first submerged vehicle

William Bourne inventions: Wikimedia

commons


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2.3 The Rotterdam Boat:

The 72-foot-long "Rotterdam Boat," designed by a Frenchman named DE SON in 1654 was probably the

first underwater vessel specifically built to attack an enemy (the English Navy). This almost a semi-

submerged ram was supposed to sneak up unobserved and punch a hole in an enemy ship. (3. The

inventions of submarines- submarine history.)

2.4 DENIS PAPIN boat:

DENIS PAPIN, a professor of mathematics built two underwater vehicles. He used an air pump to balance

internal pressure with external water pressure, thus controlling buoyancy through the in and out flow of

water into the hull.

PAPIN featured "certain holes" through which the operator might "touch enemy vessels and ruin them

in sundry ways."

Figure 3: the Rotterdam boat

Courtesy: The Navy Times Book of Submarines


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2.5 Underwater Chariots:

Chariots are a type of ride able submarine used as secret naval weapons in World War II. The basic

design is still in use today; they are a type of diver propulsion vehicle.

The name was commonly used to refer to the weapons that Italy, and later Britain, deployed in

the Mediterranean and used to attack ships in enemy harbors. A group of a dozen countries used

the human torpedo, from Italy and the United Kingdom to Argentina and Egypt, and there are some

museums and movies dedicated to this naval weapon. The human torpedo concept is used

recreationally for sport diving. (4. A HISTORY OF THE USE AND DEVELOPMENT OF MIDGET SUBMARINES AND'CHARIOTS')

Figure 4: the PAPIN design 1

The Navy Times Book of Submarines

Figure 5: PAPIN design 2

The Navy Times Book of Submarines

Figure 6 underwater chariot

Courtesy: military history journal


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3. Modern form of underwater vehicles:

The Underwater Scooter:

Underwater scooter is the modern form of underwater vehicles as it is highly beneficial for the divers for

search and rescue operations and recreation as well.

With the help of underwater scooter you can ride amongst the spectacular underwater world or remain

stationary while you feed the fish. The search and rescue operations by navy can be easily carried out

with the help of underwater scooter. The best part about this underwater scooter is that it doesnt

require any specialized scuba training nor do you have to be a great swimmer to ride around on it.

When some newer concepts emerge in the underwater market and prices go down, everyone can own

an underwater bike.

The making of reduced cost and highly effective underwater scooter is our main aim of project.

Figure 7: underwater scooter with seat

Courtesy: SEABOB underwater scooter


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Figure 8: underwater scooter without seat

Courtesy: SEA DOO underwater scooter

Figure 9: cross sectional view of underwater scooter

SEABOB underwater scooter


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Future concept in underwater scooter:

4.1 The Underwater Car:

Thirty years after the James Bond thriller The Spy Who Loved Me hit the silver screen portraying a

brand new concept of a car that doubled as a submersible boat, Swiss company Rinspeed has come up

with the first real car that can actually fly under water called the sQuba.

Submersible and stable to a depth of 10 meters (33ft), the sports car is both a beauty above water and

below. Rinspeed replaced the engine of a sports car with 3 electric motors in the back of the vehicle1

to provide propulsion on land with powerful torque to drive the rear wheels and the other 2 driving the

screws for underwater motoring and designed a salt water-resistant interior. (5. Rinspeed sQuba, Rinspeed

Creative think tank for the automotive)

4.2 3-seater submersible fighter plane:

The 3-seater submersible built in the likeness of a fighter plane uses the same principles of flight

through air underwater. It has an open cockpit and passengers use scuba gear, stored in the craft which

can dive to depths of up to 130ft. Designed by Hawkes Ocean Technologies, the Necker Nymph is the

first underwater plane to ever be designed and an entirely new class of vehicle.(6. Aqua views underwater

plane)

Figure 10: underwater multipurpose car

Courtesy: Rinspeed concept car


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4.3 Underwater scooter in PAKISTAN:

Underwater diving is a neglected sport in Pakistan but its importance in PAKISTAN NAVY cannot be

denied as it is an essential practice for search and rescue as well as combat operations. There is no

industry setup in Pakistan for manufacturing of underwater scooter. Therefore an underwater scooter

remains an imported item for amateurs and professional divers.

Reference from text books:

Since, we are going to design an underwater scooter which will experience pressure loading due to

varying water depths. For this reason we must know about fluid flow and its behavior at certain depths.

Our underwater scooter will be propelled by the help of DC motor powered by a battery. For its efficient

working underwater control systems must be in grip.

Material selection is the most important aspect of designing the structure so we have strong approach

on material sciences for material selection. To act upon this job, the designer should have a firm grip on:

5.1 Fluid mechanics:

Fluid mechanics deals with the drag and fluid flow for certain structure and the forces experienced by

that structure under the influence of that fluid. A body immersed in a fluid experiences a verticalbuoyant force equal to the weight of the fluid it displaces. A floating body displaces its own weight in the

fluid in which it floats.

Floating bodies are a special case; only a portion of the body is submerged, with the remainder poking

up out of the free surface. This is illustrated in Figure where the shaded portion is the displaced volume.

Figure 11: 3-seater underwater plane

Courtesy: Necker Nymph


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Figure 12: floating objects buoyancy

Courtesy: fluid mechanics book by Munson

Occasionally, a body will have exactly the right weight and volume for its ratio to equal the specific

weight of the fluid. If so, the body will be neutrally buoyant and will remain at rest at any point where it

is immersed in the fluid. (Fluid mechanics 5th edition by Munson)

5.2 Material sciences:

Material selection is an important aspect in manufacturing the structure. Underwater vehicles have

been developed in many ocean exploration and rescue applications. In smaller scale of underwater

vehicles, critical components are not usually commercially available. The cost of non-standard parts is

relatively high in the development stage if special molding or precision machining is involved. Therefore

selection of material for fabrication is main feature of fabrication.

5.3 Control systems:

The underwater scooter is propelled by electric motor driven by DC battery. Therefore installation of

switches and power control, maneuvering, safety, power shut down and emergency cutoff will be

covered under the control systems subject.

The power is probably the most important design characteristic in underwater scooter since it

determines the range and accordingly the mission characteristics of the scooter. The typical sources of

power on the AUVs have been batteries. Batteries are by far the most commonly used power sources

for AUVs. The advantages include the simplicity of the resulting system and commercial availability.

Battery technology is also very mature because of its innumerable applications in automobiles, portable

electronics etc.


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5.4 Engineering economics:

Engineering economics is the application of economic principles and calculations to engineering

projects. It is important to all fields of engineering because no matter how technically sound an

engineering project is; it will fail if it is not economically feasible. Engineering economic analysis is often

applied to various possible designs for an engineering project in order to choose the optimum design,

thereby taking into account both technical and economic feasibility.

When comparing costs among two or more possible alternatives, engineering economics may use either

present or future worth analysis or annual cost. Present or future worth analysis converts all the costs of

a project into equivalent present or future worth. The time period of analysis must be the same for all

options for this method to be valid.


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Principle of underwater scooter:

A propeller thruster is combined with control fins to propel and steer the vehicle. Maneuvering control

forces are generated by fluid flow over control surfaces, and the body is optimized for low drag during

forward motion.

6.1 Archimedes' principle:

Archimedes' principle is the law of buoyancy. It states that

"anybody partially or completely submerged in a fluid is buoyed

up by a force equal to the weight of the fluid displaced by the

body." The weight of an object acts downward, and the buoyant

force provided by the displaced fluid acts upward. If these two

forces are equal, the object floats. Density is defined as weight

per volume. If the density of an object exceeds the density of

water, the object will sink.

Archimedes' principle does not consider the surface tension

(capillarity) acting on the body,[3] but this additional force

modifies only the amount of fluid displaced, so the principle that

Buoyancy = weight of displaced fluid remains valid.

Buoyancy = weight of displaced fluid.

'Buoyancy force = weight of object in empty space weight of object immersed in fluid

Explanation:

If the body is less dense than the fluid, it will float or, in the case of a balloon, it will rise. If the body is

denser than the fluid, it will sink. Relative density also determines the proportion of a floating body that

will be submerged in a fluid. If the body is two thirds as dense as the fluid, then two thirds of its volume

will be submerged, displacing in the process a volume of fluid whose weight is equal to the entire weight

of the body. In the case of a submerged body, the apparent weight of the body is equal to its weight in

air less the weight of an equal volume of fluid. The fluid most often encountered in applications of

Archimedes' principle is water, and the specific gravity of a substance is a convenient measure of its

relative density compared to water. In calculating the buoyant force on a body, however, one must also

take into account the shape and position of the body. A steel rowboat placed on end into the water will

sink because the density of steel is much greater than that of water. However, in its normal, keel-down

position, the effective volume of the boat includes all the air inside it, so that its average density is then

less than that of water and as a result it will float. (http://www.britannica.com/EBchecked/topic/32827/Archimedes-

principle)

Figure 12: Archimedes principle

Courtesy: hyper physics library


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6.2 Positive Buoyancy:

Positive buoyancy occurs when the object is lighter than the

fluid it displaces. Thus, the buoyant force is greater than theobjects weight and a net upward force acts on the body.

6.3 Negative Buoyancy:

Negative buoyancy occurs when the object is heavier/denser than the liquid it displaces. Thus, the

weight of the object is greater than the buoyant force and a net downward force acts on the body.

(Gsu.edu, Buoyancy, 2000)

6.4 Neutral buoyancy concept:

Neutral buoyancy is a condition in which a

physical body's density is equal to the density of

the fluid in which it is immersed. This offsets the

force of gravity that would otherwise cause the

object to sink. An object that has neutral

buoyancy will neither sink nor rise.

Buoyancy is important in a surprising number of

fields. Designers and engineers must design boats,

ships and seaplanes in a way that ensures that

they remain afloat. In the case of submarines,

experts developed ways to make them sink and

bring them back to the surface. Many objects

were developed with buoyancy in mind, such as

life preservers and pontoons.

Figure 13: buoyancy explanation

Gsu.edu, Buoyancy, 2000

Figure 14: positive buoyancy

Gsu.edu, Buoyancy, 2000


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6.5 Stability:

In underwater scooter, rotational stability is the most important factor, since the pressure, buoyancy

and gravitational forces keep the underwater scooter vertically and horizontally stable. The design of

the scooter determines its rotational stability.

Rotational stability is defined as the measure of stability of a vehicle is conveyed by the assessment of

the moment required to change the pitch angle of the vehicle. It is characterized by the equation:

m =W (BG) sin

It is clear from the equation that a large distance between the center of gravity and center of buoyancy

provides more rotational stability. In general, the greater the distance between the COB and the COG,

the more stable the vehicle and the more likely it is to remain upright. However, the smaller the BG

distance, the less stable the vehicle but more maneuverable. (rov.org, design overview-ballast, buoyancy)

6.6 Pressure:

The pressure on an underwater vehicle is due to the weight of the water and due to the weight of the

atmosphere over the water surface. Pressure increases with depth according to the formula:

It is important to consider the pressure on the vehicle underwater, as the design and selection of

material will determine the pressure the vehicle can withstand. This will set a limit on the maximum

depth the vehicle can achieve

6.7 Drag:

Drag force on underwater scooter determines how fast the vehicle will be able to move or conversely,

what water currents will it be able to withstand. (Christ R.D., The ROV Manual, 2007)


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Design concepts

Material selection:Another choice that needs to be made in the design phase is the choice for the material of the hull. The

material should have a good resistance to corrosion, have a high strength to weight ratio and must be

affordable.

Although many materials are being used to construct underwater scooter, choice was narrowed down

to five depending upon our requirements

Steel

Aluminum

Polyvinyl chloride

Polypropylene

Fiberglass

7.1 Steel:

High strength steel is a type of alloy steel that provides better mechanical properties or greater

resistance to corrosion than carbon steel. HS steels vary from other steels in that they are not made to

meet a specific chemical composition but rather to specific mechanical properties. They have carboncontent between 0.050.25% to retain formability and weld ability.

Advantages of steel:

The advantages of high strength steel are the price and the fact that it is commonly used, so

there is much knowledge of it.

It is resistant to corrosion and much stronger and tougher than ordinary carbon steel

It is ductile and highly formable and weld able.

Disadvantages:

The major disadvantage of steel is the low strength to weight. (Fundamentals of Materials Science 3rd

edition By E. J. Mittemeijer)


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7.2 Aluminum:

The flexibility of the metal allows for several designs that can complement the facade of the structure

they are installed around. By utilizing various combinations of its advantageous properties such as

strength, lightness, corrosion resistance, recyclability and formability, aluminum is being employed in an

ever-increasing number of applications. Aluminum has a better strength to weight ratio than steel and is

widely available.

Advantages of Aluminum:

The main advantage is that aluminum components do not rust as easily as iron.

It has better strength to weight ratio and has a smooth lustrous surface due to its molecular

structure.

It has both features that are looks and strength.

Disadvantages:

It is far more expensive that steel.

The drawback of aluminum is that it is anodic to most other structural alloys, making it

vulnerable to corrosion.

It is limited to certain geometric features using economical processes.

It is abrasive to tooling.

It is difficult to weld.

It is prone to severe spring back. (Fundamentals of Materials Science 3rd edition By E. J. Mittemeijer)

7.3 Glass-fiber reinforced plastic:

The most commonly used composite for marine vehicles is glass-fiber reinforced plastic (GFRP).

Fiber Reinforced Polymer (FRP) composites are used in a wide variety of applications. Their mechanical

properties provide unique benefits to the product they are molded into. FRP composite materials

possess superior mechanical properties including:

Impact resistance

Strength

Stiffness

Flexibility

Ability to carry loads


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Advantages of GFRP/CFRP:

GFRP is cheap with respect to other composites and has a very high strength to weight ratio. Carbon

fiber reinforce composites (CFRP) are about 3 times more expensive than GFRP, but have a much higher

tensile modulus than GFRP.

7.3.1 Mechanical strength:

Fiberglass is so strong and stiff for its weight, it can out-perform most other materials including steel,

aluminum and timber.

7.3.2 High impact strength:

In contrast to most metals, fiberglass does not change shape even when it is ruptured.

7.3.3 Resilience and Formability:

Fiberglass products have a hard finish and can be molded to almost any desired shape.

7.3.4 Chemical resistance and Corrosion resistance:

Fiberglass is minimally reactive, making it ideal as a protective covering for surfaces where chemical

spillages might occur and fiberglass does not rust away and it can be used to make long-lasting

structures.

7.3.5 Anti-magnetic, no sparks:

Making it super safe for the power industry, fiberglass has no magnetic field and resists electrical sparks.

7.3.6 Low maintenance:

Once installed, fiberglass products require minimal maintenance.

7.3.7 Long life:

Fiberglass products are built to last and have high resistance to fatigue. It has shown excellent durability.

Disadvantages:

Higher initial cost compared to a conventional concrete deck. The unit cost of FRP materials isoften more expensive than conventional materials.

Limited FRP experience within the construction industry. (Fundamentals of Materials Science3rd edition

By E. J. Mittemeijer)


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7.4 Hull design:

One of the most important aspects of an underwater scooter is the watertight hull. There are a number

of different ways in which hull design can be approached. These different design methods are typically

specific to the situation. The main hull must be able to meet a number of key challenges.

Aspects that must be considered during hull design include:

Pressure and depth required

Operating depth ranges

Structural integrity

Impact conditions

Water permeability

Visual appeal and aesthetics

Accessibility

Versatility Practicality

Size requirements

Corrosion and chemical resistance

Among these considerations, the hull of the underwater scooter must be able to withstand the

hydrostatic pressure at the target depth. Furthermore, it is desired that the hull is designed in such a

way that the drag is minimized. When the vehicle moves at a constant speed, the thrust force is equal to

the drag force. The less drag the scooter experiences, the less propulsive power is needed.

A sphere is probably the first shape that comes in to ones head; it is a good shape for withstanding

pressure, but not for stability. A circular cylindrical hull is a good shape to resist the pressure. Many of

the current scooters have a circular cylindrical hull including the most popular in military and scientific

use.

Weighted and Rating Matrix:

The weighting and rating matrices is an important tool in evaluating the different concepts and choosing

the best possible concept.

The first step was to select all the design features or factors that are to be included in the weighted

matrix according to the SOR.


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The next step in the weighted matrix was to compare the different factors with each other. Each row

was compared with each column and if a row factor was considered more important than a column

factor then a 1 was entered in a relative position in the matrix. If the row factor was considered less

important than the column factor, then 0 was entered instead.

Then weights were calculated and allocated to the different factors according to their importance.

The next step was to make the rating matrix. The different concepts were compared with each other

according to the design features selected in the weighting matrix.

Each concept was given a score between 0 and 2 depending upon how well it meets the requirement of

the design feature.

Finally the concept with the highest score is considered the best possible concept.

Table no.1 Material feature requirements

Table no.2 weighted matrix

Shape features

A EnduranceB Maneuverability

C Cost

D Effect on stability

E Reliability and maintenance

F Ease of manufacture

Design

featuresA B C D E F Total Weight

A 0 0 0 1 1 2 0.133

B 1 1 0 1 0 3 0.2

C 1 0 1 1 1 4 0.266

D 1 1 0 1 1 4 0.266

E 0 0 0 0 1 1 0.067

F 0 1 0 0 0 1 0.067

15 1.000


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Shape feature Weight

Mechanism Weighting and rating

Spherical

shape

Cylindrical

shape

Spherical

shape

Cylindrical

shape

Endurance 0.133 1 2 0.133 0.266

Manoeuvrability 0.2 1 2 0.2 0.4

Cost 0.226 2 1 0.266 0.532

Effect on stability 0.226 0 2 0.000 0.532

Reliability and

maintenance0.067 1 2 0.067 0.134

Ease of manufacture 0.067 1 2 0.067 0.134

0.733 1.998

Table no.3 Rating matrix

Thus, according to the result of the matrix, it is decided that the cylindrical shape scooter is a better

choice for the diving, manoeuvring and surfacing mechanism.

Advantages of cylindrical hull:

It is a good structure to resist the effects of

hydrostatic pressure.

Extra space inside the hull can be achieved bymaking the cylinder longer.

It is a better hydrodynamic form than a spherical

form of the same volume.

It can be easily docked.

Disadvantages:

The disadvantages of a cylindrical hull are the cavitation and the instability of the vehicle.

Cavitation is a phenomenon caused by the pressure distribution generated by the moving

vehicle.

Figure 15 cylindrical hull

Courtesy: SEABOB underwater scoter


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Design Requisites:

The final design concept selected for the project is

cylindrical shape vehicle, which will be a neutral

buoyant structure. It will be capable of operating at

variable depths.

The final design should meet the following essential

requisites: Construction materials must be resistant to corrosive water elements, especially those in salt

water. It must not be fragile and resist the normal collisions that may occur during transport and

use.

If must not be deformable so as not to compromise scooter conditions and its resistance to

compression due to external pressure.

It must not vary noticeably its volume and therefore its buoyancy when changing depth.

It must have good resistance to UV-rays since these are machines that are easily left exposed to

sun rays over long periods of time.

It must resist to a pressure at least 1.5 times that stated as maximum operating pressure,

in other words, the safety factor must be at least 50%.

All nuts and bolts must be made of stainless steel in order for the scooter to be dismantled even

if flooded and with internal parts corroded. Electrical wires must be highly flexible to prevent breaking due to the high number of

bends they may sustain.

Gaskets and any other seals must be those readily available on the market. If

O-rings are used; they must be compatible with any standard silicone grease.

External parts dedicated to hull closing that may get caught and consequently damage the

scooter and cause hazards for the user should be avoided.

It must have specific handles or grasping points on the body that permit secure holds for

transport.

A main battery (cut-off) switch must be included to physically cut off at least one wire from the

battery so as to cut off battery current to any service such as the electronic regulator or

electrical motor or other components at any time. Scooter speed must be adjustable by varying motor rpm (with set propeller step).

The propeller must have radial protection so that nothing can accidentally come into

contact with the rotating blades. (Underwater vehicles theories and application, New Zealand: university of

Canterbury, Netherlands)

Figure 16 3D CAD model

(GRAB CAD)


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8.1 Hull closing system:

The underwater scooter hull closing system will be designed with the following specifications in

mind:

The hull will be guaranteed fully gas- and watertight under all circumstances that normally apply fordiving.

It will be easy to use and not induce errors in scooter closing.

It must always keep sealing surfaces in contact with gaskets.

It should not have any parts considerably protruding from the scooter shape that could, in some way,

create hazardous situations for the diver or his/her environment during dives.

Inspections must be possible and it must be removable. (Courtesy: CONSTRUCTION STANDARDS FOR UNDERWATERSCOOTERS by Marco Segatto Alessandro Fenu)

8.2 Watertight propeller shaft:

The propeller shaft, because the electrical motor is in a watertight container and the propeller is

situated on the exterior emerged in water, will be perfectly watertight.

A system that provides the highest guarantees against water infiltration in the scooter will be

designed and, therefore, a double seal is highly recommended.

Seals must be readily available on the market and not custom made.

It must be very easy to dismantle the shaft water seal group for routine maintenance.

Seals will be protected as much as possible from any insertion of hooks or

other objects that could wind around the shaft, consequently damaging the seal and

flooding the scooter.

8.3 Watertight external controls:

External controls on the scooter, such as the main switch, speed regulator and other controls will be

watertight and sealed with multiple gaskets, suitably lubricated.

Gasket seals must be those readily available on the market.

8.4 Gaskets and other sealing components:

Gaskets and any other sealing components is to be of standard types readily available on the

market (dimensions, materials).

Especially O-Rings must be of a material that can be lubricated with any standard silicon grease on the

market. (Courtesy: CONSTRUCTION STANDARDS FOR UNDERWATER SCOOTERS by Marco Segatto Alessandro Fenu)


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Project Risk Statement:

The project risk assessment helps us to identify the various risks that could be encountered while doing

the project. These risks might result in delays or termination of the project.

According to the project risk assessment, the safety and performance of the underwater scooter has the

highest risk rating. The purchase and cost also have a high risk rating while quality have the least risk

rating. By taking the appropriate measures, these risks can be tackled effectively.

Quality risk pertaining to seepage of water inside the body of underwater scooter has the highest risk.

This means the proper waxing and sealing process must be ensured, and the vehicle must be tested for

leakage before installation of components.

Both, the cost and quality risk regarding defective manufacturing have high rating. They must be next on

our priority list while managing the risks.

Cost:

The estimated project and component costs are as follows:

Items Cost (PKR)

Mould cost 30,000

Fibre glass hull 20,000

DC motors 20,000

Batteries 15,000

Shafts 5000

Construction of water tight structure with

gaskets

10,000

Fabrication cost 10,000

Miscellaneous (transport etc.) 10,000

Total 120,000


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Appendix: A

Bibliography Designing Future Underwater Vehicles: Principles and Mechanisms of the Weakly Electric Fish

Malcolm A. MacIver, Abraham Fontaine, and Joel W. Burdick

EEE JOURNAL OF OCEANIC ENGINEERING, VOL. 29, NO. 3, JULY 2004 (last visited 5 April 2013)

CONSTRUCTION STANDARDS FOR UNDERWATER SCOOTERS by Marco Segatto & Alessandro

Fenu (Research paper)

A HISTORY OF THE USE AND DEVELOPMENT OF MIDGET SUBMARINES AND 'CHARIOTS' by J H A

Speir-Military History Journal Vol 8 No 2 - December 1989

Underwater vehicles theories and application, New Zealand: university of Canterbury,

Netherlands.

Archimedes principle- available from:

http://www.britannica.com/EBchecked/topic/32827/Archimedes-principle(last visited 10 April

2013)

Department of Materials Science & Engineering. Available from:

www.materials.cmu.edu/(last visited 10 April 2013)

SEADOO scooters parts. Available from:

http://www.seascooterexpress.com/store/seascooter_parts.html(last visited 12 April 2013)

Research Papers Faculty of Materials Science and Technology. Available from:

www.mendeley.com/disciplines/materials-science(last visited 15 April 2013)

How They Work - Archimedes' Principle - Blow the Ballast. Available from:

www.onr.navy.milfocusblowballastsubwor2.htm (last visited: 10 April 2013)

RINSPEED CARS.

http://www.rinspeed.eu/concept-galery.php?cid=6last visited 04 may 2013)
http://www.britannica.com/EBchecked/topic/32827/Archimedes-principlehttp://www.britannica.com/EBchecked/topic/32827/Archimedes-principlehttp://www.materials.cmu.edu/http://www.materials.cmu.edu/http://www.seascooterexpress.com/store/seascooter_parts.htmlhttp://www.seascooterexpress.com/store/seascooter_parts.htmlhttp://www.mendeley.com/disciplines/materials-sciencehttp://www.mendeley.com/disciplines/materials-sciencehttp://www.rinspeed.eu/concept-galery.php?cid=6http://www.rinspeed.eu/concept-galery.php?cid=6http://www.rinspeed.eu/concept-galery.php?cid=6http://www.mendeley.com/disciplines/materials-sciencehttp://www.seascooterexpress.com/store/seascooter_parts.htmlhttp://www.materials.cmu.edu/http://www.britannica.com/EBchecked/topic/32827/Archimedes-principle


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Bulletin of Material Science. Available from:

www.sciencedaily.com/articles/matter_energy/materials_science/.ias.ac.in/matersci/-(last

visited 20 April 2013)

global research report materials science and technology JUNE 2011, Jonathan Adams --David

Pendlebury

Materials Research Society: Advancing Materials. Available from:

www.mrs.org/m(last visited 15 April 2013)

Modern Control Engineering 4th edition by Katsuhiko Ogata

Fluid Mechanics 5th Edition by Munson

Engineering Economy 10th edition by E. Paul de Garmo
http://www.sciencedaily.com/articles/matter_energy/materials_science/.ias.ac.in/matersci/-http://www.sciencedaily.com/articles/matter_energy/materials_science/.ias.ac.in/matersci/-http://www.mrs.org/mhttp://www.mrs.org/mhttp://www.mrs.org/mhttp://www.sciencedaily.com/articles/matter_energy/materials_science/.ias.ac.in/matersci/-


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Appendix: B

Gantt chart:


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Appendix: C

SOR

Title Design, analysis and fabrication

of underwater scooter for multi-

purpose underwater operations by

SSG(N) and PAK MARINES.

CHANGES D/W REF REQUIREMENTS

1 Introduction

1.1 Preamble

Most underwater search and recovery is done by

professional divers as part of commercial marine

salvage operations, military operations, emergency

services, or law enforcement activities.

Diving equipment refers to equipment and gear

designed to make scuba diving efficient, safe and

more convenient. Underwater scooters are used in

deep sea diving applications.

Underwater scooters contain an electric motor

used to drive the propeller, or a fan device that

transmits power by converting the energy

produced by the fan's rotation into a reaction

force, called thrust.

1.2 Scope

1.2.1 The scope of this project is to provide Pakistan

Navy the ability to transport diver and his

equipment to the mission area quickly andcovertly. It will provide great support in search &

rescue and lifesaving operations.

It has commercial applications also and can be

used for recreational purpose as well.


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1.3 Related Documents

1.3.1 Books

Fluid Mechanics 5th Edition by Munson

Introduction to fluid mechanics 6th

edition by Fox

McDonald

Mechanical vibrations by Singiresu S. Rao

Modern Control Engineering 4th edition by

Katsuhiko Ogata

Engineering Economy 10th

edition by E. Paul de

Garmo

Visual C# 2010, 4th

edition by Paul Deitel, Harvey

Deitel

Fundamentals of Materials Science By E. J.

Mittemeijer

1.3.2 Software

Solid Works and related CAD softwares for

designing the structure

1.4 Symbols

From the D/W column of this table

D Demand A mandatory requirement

W(H) Wish high A highly desirable attribute

W(L) Wish low A low desirable attribute

1.5 Deliverables

W(L) Structure analysis

W(H) Electrical power production

W(H) The underwater scooter should be able to operate


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efficiently at desired water depths

W(H) Drawings and 3D modelling of the system

W(L) Installation of search light for assistance in search

operations

W(H) Installation of steering system for effective

manoeuvrability

D Waterproof construction for preventing accidental

flooding

D Neutral buoyancy for working at different depths

D Manufacturing of casing using suitable material

D Installation of rechargeable DC batteries for

smooth power supply

D Final project report

2 Technical Requirements

CNC Machines

Knowledge and expertise of given softwares

Undergraduate knowledge of fluid mechanics and

electrical power generation

Oceanographic study for its optimal utilization in

Pakistan Navy

Lab space for material testing and swimming poolfor underwater scooter trails

Knowledge about control systems

Gaskets and Sealing components


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Insulation materials and water proof kits for

electrical components

2.2 Design Considerations

Reduction of weight

Neutral buoyancy

Placement of motor and propeller underneath to

maximise water flow, thrust and manoeuvrability

Material selection for outer casing

Cost consideration

Efficiency consideration in high current and tide

Maximum operating Water depth

Operating time

3 Miscellaneous

Most of the equipment will be bought from local

market

Project will be monitored continuously by project

supervisor and advisors

Any addition or change in current proposal will be

notified and added in agreement

Complete fabrication is subject to availability of

funding for the project

4 Hazards/Safety

Safety fuse installation for emergency stop

Safety factor in terms of maximum operating depth

Protective casing for propellers to prevent

accidental contact with the diver

General risks during underwater diving


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The underwater scooter shall be safe to operate

and would not put in risk any human life.

5 Costs

The estimated cost of the Project is Rs. 100,000.

The above mentioned cost is subjected to material

cost, assembly requirements, and testing.

Source of above funding and budged allocation

(optional)

Project Advisor's

Signature

CD&RB Report Ammended

Documents

Transcript of CD&RB Report Ammended