Title
Page No.
|
| Chapter 1. Introduction |
| 1.1 What is it?
Underwater gliders have extended use in Search And Rescue diving tasks.
The concept consists of towing one or two divers from a rescue boat so
they can search a large area rapidly. The diver to control his depth and
fly over the seabed uses the glider.
The diver can control his depth by simply inclining the board upwards or downward; in other words, just by changing the angle of attack of the board. |
| 1.2 Problems
The current gliders are very difficult to control because the board
must be kept at a constant angle and at the same time must be firmly gripped
to withstand the drag force acting on the body of the diver. Small changes
to the angle of attack of the board lead to important changes of lift,
and therefore also of depth. In order to avoid these sudden changes the
board has to be very held firmly but since the functions of controlling
and holding the board rely on the hands of the diver, this results in a
very unstable, difficult and tiring system of control.
Another problem with the current gliders is that the searching speed must be kept quite low, typically less than 3 knots (Ref.2). The reason for this is again the difficulty of manoeuvring, because the hands must support all the drag force exerted by the body of the diver at the same time as controlling the angle of attack of the board. |
| 1.3 New design
The new design will solve the current control problems and also add
some more improvements to the device. The new underwater glider will take
the control functions away from the hands so that they can be concentrated
in supporting the drag force exerted by the diver, making it easier to
control. This will result in increased safety and will reduce the tiredness
in the divers, allowing longer immersion times to be achieved
|
| Chapter 2. Literature review |
| 2.1 Similar products
One of the previous steps in all kind of designs should be to research into existing similar devices to give the designer an idea of the potential competitors and their products. This shows the advantages and disadvantages of each similar product and helps the designer to see clearly what should not be done in the new design and what would be a good idea to incorporate on it. (Ref. 3). For the design of the underwater glider, similar devices were searched at:
Another source that was also researched was the existing patents. The existence of a patent does not necessarily mean tat the product is already in the market, but can similarly give the designer a view of the existing problems and applied solutions
on similar devices. (See appendix 3).
|
| 2.2 Hydrodynamic theory
The next step in the literature review was to obtain some information
about underwater and hydrodynamics theory. The dynamics of an underwater
vehicle are very similar to those of an aircraft. Both the water and the
air are fluids the only main difference being that the last one is compressible
whereas the first one is not. But the compressibility becomes relevant
only at velocities that are far away from our purposes and, therefore both
aircraft dynamics related information as well as that about hydrodynamics
was useful for the design. (Ref.4)
|
| 2.3 Regulations
Regulations about diving procedures and design and manufacturing were consulted before and also after every step of the design process. The object of this was to adjust the design to the existing standards in order to satisfy the requirements of safety, functionality and quality. The regulations about diving procedures were consulted at the manual
of the National Oceanic and Atmospheric Administration (NOAA), where all
the working dive procedures were listed and explained. (Ref. 2)
|
| 2.4 Manufacturers of components
An important question that must be clarified before the design starts
is if the design will fill an existing production plant or if the plant
and machinery involved are a constraint to the design. It would be no good
designing for one plant set-up to find a new one in existence by the time
the production phase arrives. (Ref. 3)
|
| Chapter 3. Specifications |
| 3.1 Introduction
An underwater glider makes it possible for divers to be towed from a
boat at the surface and vary their depth according to the contour of the
sea bottom. This allows them to make a close search of the area over which
the boat is travelling.
|
| 3.2 General Factors
3.2.1 Size: It should be possible to fit the glider in the boot of an average car and it should also be easy to transport by hand by a single average adult person. A size of less than 1500mm. x 700mm. when folded (if necessary) would be acceptable. 3.2.2 Weight: Under the seawater it should be neutrally buoyant. A downward force of less than 6 kg would be acceptable. Out of the sea it should weight less than 120 Newton to allow its transport by hand. 3.2.3 Appearance: It must not obstruct the divers vision of the bottom. No sharp edges should be present, to avoid injuries in case of collision. 3.2.4 Materials: Materials must stand the action of water and salt under the water without loosing their properties. If a colour is applied it would be preferably a vivid colour in order to make its localisation easier under the water. The painting must not fade and has to be not toxic or harmful for the environment. 3.2.5 Ergonomics: As the diver is going to be in a face down horizontal position the glider must be possible to be controlled that way. The handles where the diver is going to be held from should have enough room to accommodate an average divers hand dressed in high thermal insulation gloves. The measures of the underwater glider will be adjusted to the regulations of the British Standards Institution for anthropometrics. 3.2.6 Life: It must support uses of 12 hours without stop and not get
damaged to make possible carrying out intensive searches. It is very difficult
to precise the actual life of the glider because it will be in function
of the use given by each particular user but it should be, at least, long
enough to make the acquisition of the glider cheaper than that one for
an
3.2.7 Maintenance: The glider should need to be rinsed with no more than water so it can be easily maintained. Its parts should be accessible with common tools to be replaced or adjusted in situ by the owner in case of breakdown. Spares should be made available by order, to make possible future replacements of damaged parts. 3.2.8 Cost: It must be cheaper than £600 for the final customer since there is some underwater scooters available from that price in the market. 3.2.9 Competition: The underwater glider is much more developed than the similar products found in the analysis and offers much more possibilities than them, therefore there is going to be no important competition. The only possible competitors would be the underwater scooters, but they can also be beaten if a low price is achieved for the final design. 3.2.10 Shipping: It should be possible to transport it in the boot of an average car, therefore it should be possible to dismount if necessary, therefore when folded or dismounted it should not be bigger than 1500mm. x 700mm. It will be shipped in a foam package to prevent it from damages when storing. 3.2.11 Quantity: As it is a completely new kind of product and the market does not seem to be extensive, a first limited edition of 100 units is suggested. |
| 3.3 Environment and Performance:
3.3.1 Temperature: It must stand temperatures from 0?C up to 40?C. It will be normally used between 0?C - 25?C. (Ref.2) 3.3.2 Pressure: Must support pressures from 1 atmosphere to that at 42-m depth (5 atm), since this is the maximum depth range a recreational diver is allowed to dive without decompression. It will be normally used at no more than 20-m depth (3 atm). (Ref.2) 3.3.3 Humidity: It must stand the underwater environment, therefore everything should be completely operational when submerged. 3.3.4 Vibration damping: The towline will damp all the oscillations caused by the boat. 3.3.5 Corrosion: It must resist water and salt action for periods of usage of at least 12 hours. It must also support dirty waters without getting damaged. 3.3.6 Speed: It must support speeds up to 3-5 knots (1.545-2.575 m/s), since this will be the normal towing speed range. 3.3.7 Power sources: No power sources will be incorporated. If a communication system is added then the power will be at the surface vessel. |
| 3.4 Connection to boat
3.4.1 The towline: Divers should always dive in pairs for safety reasons (Ref. 2), therefore it must be possible to tow two gliders simultaneously. The gliders must be of the same type and the tow must be carried out with two separated towlines. Practical tests suggest that towing from a single rope with two derivations would result in a destabilisation of the diver who is still being towed in case that his partner releases the glider. 3.4.1.1 The main towline: Two main towlines will be used (one for each glider) since it is proved to work better than a single one. Towlines will have a separation of at least 2m. Between them. (Ref. 1) 3.4.1.2 Derivations: The towline will divide in two parts in order to pull from two points at the glider. The line should pull from both towing points equally. This will give the glider much more stability. 3.4.1.3 Upward forces: The glider should easily counteract the upward drag force on the towline, but if necessary, a counteracting device can be added before the derivation of the towline. The counteracting device can consist on the addition of one of the following items: 3.4.1.4 Depressor: A depressor is a winged body used on water towing applications to produce a downward lift force to overcome the effect of the tow cable drag and thus achieve the required depth of operation of the vehicle without using a body of excessive weight. (Ref. 4) 3.4.2 Weight: Adding lead balls would counteract the upward drag force exerted by the towline. The spherical shape would make it more difficult for them to get hooked on rocks. (Ref. 2) 3.4.3 Detaching system: An emergency detaching system must be incorporated in case the glider gets hooked on the bottom. This will consist on the addition of a less resistance piece of line inserted between the towing line and its derivation, which will break in case of blockage. |
| 3.5 Communications
3.5.1 Concept: Two-way communications with the boat could be incorporated. These would make possible to warn the crew of the ship when the divers have released the gliders so they can stop the towing. It would also help to co-ordinate the tasks of the boatmen and divers. 3.5.2 Switch and advising devices: A waterproof pushbutton switch should be installed to advise the crew of the towing boat when the diver is going to release the glider with signals agreed on and practised prior to diving. This switch would activate a buzzer or a light on board of the towing boat. 3.5.3 The wire: The signal must go up to the surface through a cable attached to the towline. This cable must be waterproof as well, and must have enough different wires inside to allow individual communications with all the divers to be made. Optic fibre could also be an alternative to the conventional cable. |
| 3.6 Instruments
3.6.1 Navigation: A compass and a depth meter will be installed on the
wing so the diver
3.6.2 Other: Another possible instruments included in the glider are
a thermometer and a
|
| 3.7 Recommendations for usage
The following procedures are recommended, according to the National Oceanic and Atmospheric Administration (NOAA). (Ref.2) 3.7.1 Jet dive: If possible, the boat should be equipped with jet dive propulsion system, which has no rudder or propeller. 3.7.2 Propeller cage: If the boat is equipped with a propeller, a propeller cage should be fabricated to protect the divers. 3.7.3 Signal devices: Divers being towed should carry signal devices (whistle, flare, etc.) especially in adverse weather conditions such as fog, in case they become separated from the boat and towline. 3.7.4 Surface float: Unless there is danger of entanglement, the divers should carry a surface float to assist the boat crew in tracking them. The float line also can be used for signalling the divers while they are on the bottom. 3.7.5 Boat equipment: The boat should be equipped with charts, radio, first aid kit and resuscitator, emergency air supply, and all the equipment required by the Coast Guard for safe boating operations. 3.7.6 Distress call: The boat operator should know the procedure for alerting the Coast Guard in case of an accident. 3.7.7 Dive planing: All personnel on board should be thoroughly briefed on the dive plan. |
| Chapter 4. Conceptual Design |
The current gliders are very difficult to control because the board
must be kept at a constant inclination in order to maintain the diving
level, as shown in Figure 2.
 The lift force on an airfoil is the sum of the lift force generated due to the angle of attack and that due to the camber. Lift = Lift Due to AOA + Lift Due to camber (1.1)
In the case of the existing gliders there is no camber so all the lift comes from the change in angle of attack. Depending on their shape, cambers can provide positive, negative or neutral lift, as shown in figure 3.  As the glider must provide positive and negative lift depending on the necessity of the moment it would be very useful to build it as an airfoil with variable camber in order to get the desired lift at each particular moment. The way of making this possible is to add a control surface. Control surfaces or ailerons are mobile parts installed in the rear portion of the wing. They move upwards or downwards at pilots will, as shown in figure 4. (Ref.6)  The best thing about them is that they can provide lift force opposite to that due to the angle of attack. This is especially useful for underwater gliders, since the main control problem was the difficulty on maintaining the desired angle of attack. The initial idea for improving the safety and manoeuvrability of the glider was to add an aileron. The control qualities of the glider would then be improved by changing the angle of the aileron upwards or downwards in addition to the inclination of the whole board. However during the design process it was noticed that a potential control
surface was being ignored: The fins.
 The lift produced in the fins will affect the pitching moment created
by the wing lift in the centre of gravity and this will lead to a change
in angle of attack, which will increase or decrease the lift on the wing.
The main wing will have a neutral camber, so it will provide positive or
negative lift depending on the manoeuvres of the diver.
The main frame will consist on three bars that would be welded together
and would support all the other elements, as the chassis does in cars.
|
| Chapter 5. Final design |
| The final step of the designing process required to concrete and design
in more detail each part and to research about which materials were the
most convenient for each element of the design. The final assembly can
be seen in the Appendix 5.
5.1 Main frame The main frame, or the chassis, is the structure that supports all the components of the underwater glider. It had to be a resistant structure since it would have to support the towing and drag forces, as well as those created when manoeuvring. In the other hand it had to be a light structure, since the final weight of the design was also an important factor. The chosen material was an aluminium alloy used commonly on shipbuilding. It combines a big strength with a low weight and also has excellent weldability and resistance after welding qualities. The structure will consist on three bars of square hollow section, two laterals and a central one that will be joined in a U shape. The joining will be possible thanks to a pair of prismatic pieces of the same metal used for the bars which will be located on the tips of the central bar and will get inserted into the lateral ones, after what it will be welded. At the ahead end of each lateral bar another prismatic piece will be inserted into the hollow of the bar and it will be also welded. This piece of aluminium alloy will have a thread machined in its centre at which the towing point will be attached. Another bar of the same characteristics will be welded on the top of
each lateral bar, this ones been longer since they will have the leg support
attached to their ends. The holes from which the additional components
will be attached to the main frame will have to be machined once the structure
is finished.
|
| 5.2 Hand supports
The hand supports will be fitted to the main frame at its front laterals
and its shape will be that one of a T laying on one side. It will be built
in aluminium alloy.
 |
| 5.3 Main wing
The main wing was required to be a relatively thin symmetrical hydrofoil
in order to provide positive or negative lift as required by the divers.
It had to be rigid and resist high bending forces at the same time combined
with a low weight, so it was decided to be built in a composite of carbon
fibre and epoxy that is widely used for aircraft components and some car
parts.
 |
| 5.4 Leg support
It will consist on a flat board that will be placed at the rear part
of the glider and will act as a support for the legs at the same time that
will help on the stability.
 |
| 5.5 Towing point |
 |
The towing points will be located at the root of the main
wings.
They will be built in stainless steel and will be capable to rotate over their center axis so the towing force can be applied from any frontal direction. It will be attached to the main frame by its axis, which will be a stainless steel threaded bolt. |
| 5.6 Fasteners
Only two different size of threaded bolts have been used in the design
to attach all the elements to the main frame.
The use of only two different sizes will make unnecessary for the user to carry a large set of tools in order to adjust or dismount the different parts of the glider. |
 |
| Chapter 6. Discussion |
| The design of the underwater glider implied learning the basic principles
of conceptual designing, which includes market assessing and finding of
needs, specification, product development and detail design.
The market assessment and the search for similar designs are the basic tasks to be performed in order to find out the problems and advantages of other products. It also makes clear if there is a need for a new design. The specification is the most important aspect to be considered. No design can take place until a firm specification has been agreed. But before this document can be written the problem and constraints to be satisfied by the design have to be recognised and defined. This aspect can be the most difficult one, because having a problem does not mean necessarily recognising it, neither to be able to define it. One of the most important tasks at the product development stage is to get information about theory, limitations, properties of materials and best material choices, regulations etc. The information at the designer disposal is often widely scattered, and it can only be obtained via long tedious searches. But if this search is not done, the danger exists that a key piece of information will be missed. Computer databases, microfilm collections and the Internet can be used to great effect in assisting the designer during this stage. Obviously, as well as accumulating information, designers must have to reflect upon it. The designer must use all his experience, knowledge, ingenuity and ability to compromise in the trade-off between different design parameters, e.g. weight versus reliability. The designer must then translate the pictures on his own mind into a
drawing which will convey his thoughts to others, and which will eventually
become a three-dimensional piece of equipment. Many decisions will depend
on scientific analysis, but many others will be non-scientific in nature
and will be determined by the non-verbal reasoning of the designer.
|
|
|
Tasks |
|
|
Project proposal. |
|
|
Write proposal. |
|
|
Specifications / Planing / Standards / Look for similar products |
|
|
Research into hydrodynamics / Learn about underwater wings / Look for similar products |
|
|
First design and sketches / research into Hydrodynamics and underwater wings |
|
|
2nd design and sketches ? Apply hydrodynamics / Look for control systems in similar products. |
|
|
Design the control system / sketch control system |
|
|
Look for materials |
|
|
3rd design and sketches / start writing interim report |
|
|
Finish interim report ? Submit on December the 3rd. |
|
|
Prepare interim interview. |
|
|
Prepare interim interview. |
|
|
Draw sketches of the conceptual design / Design tow-line (including deflector or weights) |
|
|
Finish tow-line design / Find materials for tow line / Design control system (including handles) |
|
|
Finish control system / Find materials for control system / Find materials for communication switch / integrate on handles |
|
|
Design communication system / find materials / find materials for glider |
|
|
Attach communication system to towline and glider / Integrate instruments to glider / Finish glider design |
|
|
Final drawings / write draft of the report |
|
|
Write final report / prepare interview |
Table 1. Task program for the whole year.
| The table was not strictly followed because adding new tasks was made necessary during the process and some others required less time that the one supposed at first. But not following the timetable does not mean that is unnecessary; programming the process provides the designer with a future useful reference about the importance and hierarchy of each particular task. |
| Chapter 7. Conclusions |
| As said before, the whole project of designing the underwater glider
has not just consisted on drawing a new device. It has also been a great
contribution of knowledge and practice about information hunt, definition
of constraints for s design, listing and determining the specifications,
learning and getting acquainted with the Engineering Drawing Practice BS308
and the Computer Aided Designing programs and procedures, searching for
manufacturers of components and adapting the design to the availability
of those components
etc.
The design process of the underwater glider had more from a researching project than simply drawing some sketches. As a result, a completely new kind of underwater glider has been designed. The use of a concise designing method, in order to avoid the weakness and to take advantage from the good qualities of some other devices designed with the same purposes has resulted in a new successful product. This new device covers all the mayor weaknesses of the old ones and offers a series of advantages that will probably open it to a market with no competitors. |
| Chapter 8. Further Work |
| Only a small part of the design process was covered during this final
year project, and stages like detail design and design for production were
not included at all. The conceptual design can anyway be improved with
some features that, despite the fact that they were kept in mind, there
have been no time to develop.
The first suggestion is to continue with the design of a communication way between the diver and the crew on the surface. This would allow the divers to warn the people on the towing-boat when they are going to detach themselves from the gliders to investigate a particular area. Also, it would be very helpful to agree a towing speed reasonable for both the divers and the towing-boat. This idea started to get developed but, because of the lack of time, it had to be finally discarded by the moment. Also, as suggested from the National Oceanic and Atmospheric Administration, a brush handle type seat could be placed between the legs of the diver, so one hand could be released without loosing control of the glider. Finally, the observations made at the diving tests showed that there is a serious problem if the inexpert towed diver tries to glide in a face-forward position. The problem is that the regulators, which supplies the required quantities of air to the diver in order to breathe, are not designed for the speed reached when being towed. The regulator consists on a rubber valve, which opens the duct of the air when the vacuum produced by the breathing action of the diver acts on it. The design of the regulators does not take in account the towing and the rubber valve bends under the pressure of the water. When the valve bends the water gets mixed with the air and the diver can breath both elements at the same time, so some ability is required from him to separate the liquid from the air and breath only the last one. As the design of the regulators is not expected to change, the best way to avoid this problem would be to add a small canopy to the design of the underwater glider. This canopy would need to cover the divers face from the pressure of the drag force of water. The material must be transparent to allow a forward vision and also a scanning of the seabed. Also, the canopy should be designed with no sharp edges on it, to avoid injuries in case of accident. |
| Appendix I. References |
| 1. HER MAJESTYS STATIONARY OFFICE. Police Diving Manual. Her
Majestys
Stationery Office, 1st ed. 1975. Part 3. 2. NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION. Section 8: Working
Dive Procedures. Part 10: Diving from an anchored platform. In: National
Oceanic and Atmospheric Administration. NOAA Manual. Diving for Science
and Technology. <http://www.uwsports.com/reference_library/noaa/section_08/subsection_10.htm>
3. FEILDEN, G.B.R. A guide to design for production. 1st ed. The Institution of Production Engineers, 1984. 4. SOCIETY FOR UNDERWATER TECHNOLOGY. Advances in underwater technology, ocean science and offshore engineering. Volume 15. Technology Common to Aero and Marine Engineering. 1st ed. Graham & Trotman, 1988. Part 1. 5. MUCCI, Peter. Handbook for engineering design. 4th ed. BSI Standards, 1994. 6. DEPARTMENT OF AERONAUTICAL, MECHANICAL, AND MANUFACTURING ENGINEERING. Second Year notes in Flight Dynamics. The University of Salford, 1998. 7. DISCOUNT DIVERS SUPPLY. Underwater Exploration. Underwater
tow sled.
8. DISCOUNT DIVERS SUPPLY. Underwater Exploration. Sea Scanner.
9. SEATRONICS. Sidescan Sonar Systems. Seatronics,
Inc. 1st ed. 28 Feb. 1997
7. ABKOWITZ, Martin A. Stability and motion control of ocean vehicles. 1st ed. Massachusetts Institute of Technology, 1969. |
| Appendix II. Bibliography |
| a. General bibliography
SOCIETY FOR UNDERWATER TECHNOLOGY. Advances in underwater technology, ocean science and offshore engineering. Volume 5. Submersible Technology. 1st ed. Graham & Trotman, 1986. SOCIETY FOR UNDERWATER TECHNOLOGY. Advances in underwater technology, ocean science and offshore engineering. Volume 9. Stationing and Stability of Semi-Submersibles.1st ed. Graham & Trotman, 1986. UPSON, R. H. and KLIKOFF, W.A. Application of practical hydrodynamics of airship design. NACA Report No 405, 1931. SOCIETY FOR UNDERWATER TECHNOLOGY. Advances in underwater technology, ocean science and offshore engineering. Volume 15. Technology Common to Aero and Marine Engineering. 1st ed. Graham & Trotman, 1988. WHICKER, L. F. and FEHLNER, L.F. Free stream characteristics of a family of low aspect ratio all moveable control surfaces for application to ship design. DTMB Report 933, 1958. ABKOWITZ, Martin A. Stability and motion control of ocean vehicles. 1st ed. Massachusetts Institute of Technology, 1969. BISHOP, R.E.D. and PRICE, W.G. The dynamics of marine vehicles and
structures in waves. 1st ed.
FAY, James A. Introduction to Fluid Mechanics. 1st ed. Massachusetts Institute of Technology, 1994. THE UNIVERSITY OF SALFORD. DEPARTMENT OF AERONAUTICAL, MECHANICAL, AND MANUFACTURING ENGINEERING. Second Year notes in Flight Dynamics. The University of Salford, 1998. KINSKY, Roger. Applied Fluid Mechanics. 6th ed. McGraw-Hill Book Company, 1982 CASINI, Giuseppe.Calcolo e disegno meccanico per disegnatori operai
e tracciatori. 9th ed.
MUCCI, Peter. Handbook for engineering design using standard materials
and components. 4th ed.
THE INSTITUTION OF PRODUCTION ENGINEERS. A guide to design for production.
1st ed.
GRIFFITHS, A. Fasteners handbook. 1st ed. Morgan-Grampian Books Ltd. 1969. KERMODE, A. C. Mechanics of flight. 10th ed. Longman Group Limited, 1996. EPPLER, Richard. Airfoil design and data.1st ed. Springer-Verlag,
1990.
b. Regulations and Procedures: NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION.
BRITISH STANDARDS INSTITUTE. British Standards Service.
HER MAJESTYS STATIONARY OFFICE. Police Diving Manual. Her Majestys Stationery Office, 1st ed. 1975. (Last access: 17 May 2000) ER-ONLINE. Reference & Standard Organizations.
IBM. Intelectual Property Network
IBM. Gallery of obscure patents.
c. Online Sources: MARINET. 1999 Ocean Technology Workshop <http://www.motn.org/workshop99/default.html> MariNet: Marine Technology Online. Last updated: 29 Apr. 1999 (Last access: 17 May 2000) ANDREW KING. Patent information. <http://unicorn.sanger.ac.uk/patent.htm>
The Welcome Trust Genome Campus home pages, 15 July 1999. (Last access:
17 May 2000)
DISCOUNT DIVERS SUPPLY. Underwater Exploration. Sea Scanner.
DISCOUNT DIVERS SUPPLY. Underwater Exploration. Underwater tow sled.
DCF INNOVATIVE DESIGN. ROV Net. <http://www.rov.net>
DCF Innovative Design, 31 Oct. 1999
OCEANEERING INTERNATIONAL, INC. Oceaneering <http://www.oii-adtech.com> Oceaneering International, Inc. 1999. (Last access: 17 May 2000) BENTHOS Inc. Benthos, Underwater Technology. <http://www.benthos.com/benthos.htm>
ISR ORGANIZATION. International Submarine Races. <http://www.isrsubrace.org> ISR Organisation, Foundation for Underwater Research and Education, 8 Oct. 1999 (Last access: 17 May 2000) SEATRONICS. Sidescan Sonar Systems. <http://www.seatronics.co.uk/Side.htm>
Seatronics, Inc.
NETWORK WORK PLACE DESIGN. Waal Catalogue of products. <http://www.worcester-aluminium.com/product.htm>
1st ed. Worcester Aluminium Alloys, 1999.
JERGENS INC. Catalogue of products.<http://www.jergensinc.com/>
1st ed. Jergens Inc. 2000.
NET RESOURCES INTERNATIONAL. Offshore Technology. <http://www.offshore-technology.com/index.html> 1st ed. Net Resources International, 2000. (Last access: 17 May 2000) UNIVERSITY OF WASINGTON, SCHOOL OF OCCEANOGRAPHY. The virtual mooring
glider. An autonomous underwater glider. <http://www.ocean.washington.edu/research/glider/project.html>
1st ed.
DAVENPORT, Ryan. Davenport skeleton sleds <http://members.home.net/sleds>
Davenport skeleton sleds,
Harding, Jeff. Scientific diving and boating safety program. <http://www2.ucsc.edu/sci-diving> Institute of Marine Sciences of the University of California, Dec. 1999. (Last access: 17 May 2000) MANCHESTER COMPUTING. Consortium of Academic Libraries in Manchester
TI web. <http://tiweb.li.umist.ac.uk/tisearch.htm>
Umist Library, Jan. 2000 (Last access: 17 May 2000)
d. Magazines and Catalogs: CHAPLIN, TIM. Umbilicals. Underwater Contractor Magazine. Issue 8, Jan/Feb 1997 MARINE SONIC TECHNOLOGY LTD. Sea Scan? PC Side Scan Sonar.Oceanscan, for Marine Sonic Technology Limited (MSTL). 21 Oct 1999 |
| Appendix 3. Comparison of existing gliders
a. Tow sub |
 |
The Tow sub is a patented project that can not be found in the market
yet.
It incorporates a canopy to protect the diver from the drag force generated when towing which increases the comfort and could extend the diving tie of the diver since it reduces their tiredness. Even thought, the main problem of this design is that the vehicle is too big for the purposes we are looking at. This would not only imply the problem of storing and transporting it but also that the drag forces that must be counteracted would be extremely high, which means that a very powerful tow-ship would be needed |
| b. Sea scanner
The sea scanner is a small and light device, which means that can be
easily transported and stored.
The main problem is that it becomes unstable and difficult to control since divers have to stand the drag forces at the same time that must maintain the hands in a very firm position to maintain a constant lift.
|
Figure 14. Sea scanner |
| c. Underwater Tow Sled
The Underwater Tow sled is also very easy to store and transport and again, does not offer a big resistance against the towing force so it can be towed by any kind of boat. |
| A good feature of this design is that a third handle has been incorporated
so divers can held it with one or two hands indifferently.
The basic problems of this product are the same shown in the Sea Scanner: a bad control system that derives in diver tiredness and reduction of speed and increase of time of search. |
Figure 15. Tow sled. |
| d. Home Built Devices
|
Because of the existing lack of European manufacturers and the simplicity
of the existing products most users tend to build their own devices.
These are normally very similar to those existing in the market and, therefore have the same problems.This one shown in Figure 16 belongs to a sea rescue society and is used for underwater rescue tasks. The main problem is the control again. As the previously seen designs, the control functions relay on the hands of the diver, which should be exclusively concentrated on supporting the drag force. |
| e. Common problems.
In addition to the problem of the apparent non-existence of European
manufacturers and taking the first example, the Tow Sub, apart all the
analyzed designs had the same control problem. All of them employed the
hands to exert control over the glider. At the same time the hands had
to support the strong drag forces created against the water.
|
| Appendix IV. Interviews to the professionals and diving tests |
| a. Interviews
Apart from the observations done over the existing models of underwater gliders there was another source of information that would confirm the problems and advantages deduced so far: The users of these apparatus. The interview was carried out in a sea rescue station of the Red Cross, and the interviewed were active crewmembers and divers of from this station. |
| The interviews did in fact confirm the disadvantages observed on the
current designs and also gave some suggestions about procedures of towing
and gliding.
The main problem was confirmed to be the one concerning the control, as observed before. Also, the impossibility of the divers to read their consoles and get all the information about depth, bearing and time was stated. Integrating a second group of instruments in the glider itself could easily solve this, but apparently there is not any design that includes it. A suggestion made by the interviewed professionals was to arrange the handles of the new design in a vertical position, since this would made the manoeuvring more conformable than if the handles had to be hold horizontally. |
Figure 17. Interviewing users. |
| b. Diving Tests
The possibility of a diving test with the gliders fabricated by the crewmembers of the sea rescue station was a very interesting suggestion from the designing point of view. Testing the apparatus is the best way to find their good and bad characteristics so, after checking the availability of the people and the equipment, a date was fixed for the tests.
The test was carried with two gliders towed by an outboard rescue ship
with two 20m long towlines. The procedure requires the divers to stay floating
in the water with the glider firmly hold in their hands as the boat starts
to tow.
Maneuvering the glider at that stage was an easy task; inclining the
board at a negative angle of attack resulted in a smooth descent, whereas
introducing a positive angle to the board had the opposite results.
This difficulty was rapidly solved when the boat started to accelerate to the normal searching speed of 3 knots. The glider could now descent without any difficulty, but because of the high forces that the water was exerting on the divers at that speed the glider became very unstable. The difficulty to maintain the wrists in a firm position was causing a vibration on the hands that made the angle of attack to acquire a small but continue change of inclination. This made the divers apply continuous control forces over the board with the consequent tiredness.
Later on the ship accelerated to 3.5 knots, which was said to be the maximum towing speed employed by this particular rescue team. The drag force that pushes against the diver had dramatically increased in that moment and the difficulties of control became then much more evident. A big force was needed to apply in order to keep holding the glider, and the necessity of separating the function of control from the hands became evident then. The test ended after some turning trials, which proofed that the lateral
control of the glider is a relatively easy task.
|
| Appendix V. Drawings |
| Appendix VI. Calculation of weight |
| Once the final drawings were produced the weight calculation for the
glider was done to assure that the design would satisfy the specification.
To calculate the weight the mass of each component have to be known, and the best way to get it is to work it out from the following relationship: m = ? / V Once the mass is known the weight is calculated from: W= m * g As a rough value was just needed only the weight of the biggest and
heaviest components was calculated, as shown below.
But as there are two main wings, The hand supports are built in the mentioned aluminium alloy ant have
therefore a density of 2660 kg/m3. The area for the hand supports was calculated
to be 0.000368602 m3 and, therefore, it has a weight of 9.805N.
The leg support is built in carbon fibre + epoxy, with a density of 1550 kg/m3, and has a volume of 0.00146 m3. Then, applying the formulae, the weight is calculated to be: The total weights of these parts, which are the more relevant, sums a total of: This weight is well down below the specified maximum of 120 Newton, so the specification is satisfied at this area. |
| Appendix VII. Wing data charts.
Hydrofoil co-ordinates |
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| Hydrofoil co-ordinates |
| Iñaki Rodriguez Rebolledo |  |
Curriculum Vitae, 2004 |
