Diver Propulsion Vehicle Level 1

Global
Underwater
Explorers
Diver Propulsion Vehicle Level 1
Ver 1.01
Global Underwater Explorers: Diver Propulsion Vehicle Level 1 by Dan MacKay
© 2011 Global Underwater Explorers
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Trademarks
GUE is a registered trademark of Global Underwater Explorers in the United States and other countries.
ISBN XXXXX
10 9 8 7 6 5 4 3 2 1
GUE DPV Diver Level 1
Contents
Contents3
Clutch. . . . . . . . . . . . . . . . . . . . . . . 18
The Gavin Scooter7
Tow-cord Attachment . . . . . . . . . . . . . . . . 18
Getting Started
Attachment Methods:. . . . . . . . . . . . . . . . 19
9
DPV Considerations. . . . . . . . . . . . . . . . . . . . 9
Barotraumas . . . . . . . . . . . . . . . . . . . . 10
Running Out of Gas. . . . . . . . . . . . . . . . . 10
Decompression. . . . . . . . . . . . . . . . . . . 10
Equipment Failure. . . . . . . . . . . . . . . . . . 10
Human Error . . . . . . . . . . . . . . . . . . . . 10
Environmental Issues . . . . . . . . . . . . . . . . 11
Skill . . . . . . . . . . . . . . . . . . . . . . . . 11
What have we discovered?. . . . . . . . . . . . . . 11
GUE DPV Programs. . . . . . . . . . . . . . . . . . . 11
Course Structure: DPV Level I Diver . . . . . . . . . . 12
Comprehensive diving theory that will encompass: . . .12
Training Limits . . . . . . . . . . . . . . . . . . . 12
Timetable . . . . . . . . . . . . . . . . . . . . . 12
Course Structure. . . . . . . . . . . . . . . . . . .12
Land Exercises. . . . . . . . . . . . . . . . . . . . 13
In-water Practice. . . . . . . . . . . . . . . . . . 13
Components, Balance, and Trim
17
General Composition of a DPV. . . . . . . . . . . . . . 19
Components . . . . . . . . . . . . . . . . . . . . 19
DPV Materials. . . . . . . . . . . . . . . . . . . . 19
Disassembly . . . . . . . . . . . . . . . . . . . . 20
Reassembly. . . . . . . . . . . . . . . . . . . . .21
Maintenance . . . . . . . . . . . . . . . . . . . . . . 21
Inside the Motor Compartment. . . . . . . . . . . . 21
Electronics . . . . . . . . . . . . . . . . . . . . . 22
Motor Connections - Internal . . . . . . . . . . . . . 22
O-rings—Motor Compartment . . . . . . . . . . . 22
O-rings—Main Body . . . . . . . . . . . . . . . . 23
Testing. . . . . . . . . . . . . . . . . . . . . . . . .23
Blades . . . . . . . . . . . . . . . . . . . . . . . 23
Clutches. . . . . . . . . . . . . . . . . . . . . . 23
The Motor . . . . . . . . . . . . . . . . . . . . . 24
Batteries. . . . . . . . . . . . . . . . . . . . . . . . 24
Choosing a Battery . . . . . . . . . . . . . . . . . 24
Battery Packs . . . . . . . . . . . . . . . . . . . . 25
Battery Charging/Operation . . . . . . . . . . . . . 25
Getting Familiar. . . . . . . . . . . . . . . . . . . . .17
Burn test batteries. . . . . . . . . . . . . . . . . . 25
Reliability . . . . . . . . . . . . . . . . . . . . . 17
Multi-meters. . . . . . . . . . . . . . . . . . . . 25
Parts. . . . . . . . . . . . . . . . . . . . . . . . 17
Burn Testing . . . . . . . . . . . . . . . . . . . . 25
Tow-behind and Ride-on Designs. . . . . . . . . . . 18
Battery Burn-testing Procedure. . . . . . . . . . . . 26
Variable Speed Adjustment. . . . . . . . . . . . . . 18
Battery Maintenance . . . . . . . . . . . . . . . . 26

3
Motor Rotary Seal. . . . . . . . . . . . . . . . . . 26
Streamlined Storage . . . . . . . . . . . . . . . . .38
Maintenance Schedules . . . . . . . . . . . . . . . . . 28
Dive Planning. . . . . . . . . . . . . . . . . . . . . . 39
Technical Protocol. . . . . . . . . . . . . . . . . . 28
Team Strategies. . . . . . . . . . . . . . . . . . . 39
Recreational Protocol . . . . . . . . . . . . . . . . 28
Dive Objectives . . . . . . . . . . . . . . . . . . . 39
Post-dive Normal Care. . . . . . . . . . . . . . . . 28
Procedures. . . . . . . . . . . . . . . . . . . . . 40
Long-term Extensive Care . . . . . . . . . . . . . . 29
Logistics . . . . . . . . . . . . . . . . . . . . . . 40
Storage and Transportation . . . . . . . . . . . . . . . 29
Dive Profile and Parameters . . . . . . . . . . . . . 40
General Considerations. . . . . . . . . . . . . . . . 29
Risks and Contingencies. . . . . . . . . . . . . . . 40
Balance and Trim. . . . . . . . . . . . . . . . . . . . 30
In-water and Surface Support . . . . . . . . . . . . 40
Proper Weighting and Ballast Control . . . . . . . . . 30
Nutritional Requirements . . . . . . . . . . . . . . 40
Trim Position. . . . . . . . . . . . . . . . . . . . 31
Dive Parameters . . . . . . . . . . . . . . . . . . . . 41
Planning and Gas Mangement 35
Awareness. . . . . . . . . . . . . . . . . . . . . . . 35
Gas Mix. . . . . . . . . . . . . . . . . . . . . . .41
Situational Awareness . . . . . . . . . . . . . . . . 35
DPV Considerations. . . . . . . . . . . . . . . . . 42
Environmental Awareness . . . . . . . . . . . . . . 36
Breathing Gas Requirements. . . . . . . . . . . . . . . 42
Depth. . . . . . . . . . . . . . . . . . . . . . . 36
Gas Consumption. . . . . . . . . . . . . . . . . . 42
Time. . . . . . . . . . . . . . . . . . . . . . . . 36
Minimum Gas. . . . . . . . . . . . . . . . . . . . 42
Gas Management. . . . . . . . . . . . . . . . . . 36
Establishing Minimum Gas. . . . . . . . . . . . . . 43
Decompression Management. . . . . . . . . . . . .36
Gas Management. . . . . . . . . . . . . . . . . . . . 44
Distance . . . . . . . . . . . . . . . . . . . . . . 36
All-Usable . . . . . . . . . . . . . . . . . . . . . 44
Navigation. . . . . . . . . . . . . . . . . . . . . 36
Half-Usable . . . . . . . . . . . . . . . . . . . . .45
Environment . . . . . . . . . . . . . . . . . . . . 37
DPV Specific Management. . . . . . . . . . . . . . . . 46
Entanglement. . . . . . . . . . . . . . . . . . . . 37
Power Management. . . . . . . . . . . . . . . . . 46
Equipment Awareness. . . . . . . . . . . . . . . . . . 37
Available Burn Time. . . . . . . . . . . . . . . . . 46
Team Resources. . . . . . . . . . . . . . . . . . . 37
Reserve Burn Time. . . . . . . . . . . . . . . . . . 46
Verification. . . . . . . . . . . . . . . . . . . . . 37
Distance . . . . . . . . . . . . . . . . . . . . . . 47
Malfunction . . . . . . . . . . . . . . . . . . . . 37
DPV Dive Planning Checklist . . . . . . . . . . . . . 48
Team Awareness. . . . . . . . . . . . . . . . . . . . 38
4
Exposure . . . . . . . . . . . . . . . . . . . . . . 41
Operation and Driving Techniques
55
Capacity. . . . . . . . . . . . . . . . . . . . . . 38
The Importance of Technique. . . . . . . . . . . . . . .55
Responsibility. . . . . . . . . . . . . . . . . . . . 38
DPV Positioning. . . . . . . . . . . . . . . . . . . . .55
Dive Plan. . . . . . . . . . . . . . . . . . . . . . 38
Operational position . . . . . . . . . . . . . . . . .56
Protocol . . . . . . . . . . . . . . . . . . . . . . 38
Temporary position . . . . . . . . . . . . . . . . . 57
Introduction Contents
Parked position. . . . . . . . . . . . . . . . . . . 57
Dealing With Emergencies. . . . . . . . . . . . . . 63
Team Positioning. . . . . . . . . . . . . . . . . . . . 58
Run-away DPV . . . . . . . . . . . . . . . . . . . 64
Line formation . . . . . . . . . . . . . . . . . . . 59
Broken Trigger . . . . . . . . . . . . . . . . . . . 64
Wing formation. . . . . . . . . . . . . . . . . . . 59
Damaged or broken DPV . . . . . . . . . . . . . . . 65
Tow formation . . . . . . . . . . . . . . . . . . . 60
Flooded DPV . . . . . . . . . . . . . . . . . . . . 65
Matching Speed . . . . . . . . . . . . . . . . . . . . 61
Gas Sharing. . . . . . . . . . . . . . . . . . . . .65
Communication. . . . . . . . . . . . . . . . . . . . .62
Limited Visibility . . . . . . . . . . . . . . . . . . 66
Light communication . . . . . . . . . . . . . . . . 62
Conclusion . . . . . . . . . . . . . . . . . . . . . . . 66
Communication protocol. . . . . . . . . . . . . . . 62
Emergency Procedures. . . . . . . . . . . . . . . . . .63

5
Preface
by George Irvine
The Gavin Scooter
An Historical Perspective
Diver Propulsion Vehicles (DPVs) were originally born from a perceived military need and eventually were offered to the public. Over time, these helpful devices found their way into cave diving. Various attempts at creating delivery vehicles for the military produced all sorts of mostly secret and largely bizarre vehicles. Some of
these vehicles were probably best suited for movies, while the truly useful vehicles are likely a well-kept secret.
Three of the most popular DPVs used in early cave diving were the Aquazepp and Farallon, which were ride-on
scooters, and the Tekna, which was a tow-behind. Ride-on scooters present issues with control in tight spaces, extra gas consumption due to the effort that was required to steer them, and having dive equipment getting
entangled in the prop. All early scooters had reliability issues. The Aquazepp and Farallon problems revolved
around inefficient motors, unreliable electronics, multiple voltages, and undependable battery pack connections.
Meanwhile the Tekna was difficult to disassemble precluding pre-dive evaluations; it was also prone to explosions, rated for shallow water diving, and had very limited battery capacity.
Initially wreck divers really did not care much for DPVs. If used at all, the distances were typically short enough
that the shortcomings of the scooters were not critical. Early cave divers using DPVs did not complain much
about the short burn times because long-distance explorations were not common at the time. Motivated divers
such as Sheck Exley merely dropped his DPV at its limit and swam the rest of his dive. Most US and Mexican
caves are relatively shallow, so the shallow rating on the early Tekna was fine for most people; this was the DPV
of choice for a budding cave diving community.
As cave divers became familiar with DPVs, they naturally wished to take them deeper and farther. One prominent example is the needs of early explorers. Several early attempts involved simple modifications to the Tekna
scooter. GUE president Jarrod Jablonski worked with others interested in deep cave diving by placing support ribs
in the old Tekna scooter and removing the weak acrylic front lens; these changes allowed these DVPs to survive
repeated excursions beyond 300ft/90m. However, it was early cave diving pioneer Bill Gavin who would make
the most lasting impact on cave diving DPVs. The limitations of the Tekna were almost immediately obvious for
divers of the Woodville Karst Plain Project (WKPP) and Gavin would focus his engineering resources on a scalable solution. Bill’s efforts culminated in the development of what became known as the “Gavin” scooter. Given
the popularity of the Tekna motor, Gavin’s design used this drive system in a system that produced a deep-rated
DPV with the capacity to accept a range of battery configurations. I was diving with Bill Gavin at the time and
utilized Gavin’s design, expanded production for other team members and standardized certain dimensions and
layouts. These changes provided a DPV that allowed parts to be interchangeable among different units.
My early commitment to supporting DPV production helped revolutionize the team’s capacity and greatly expanded the reach of what would become one of the most productive groups of explorers in cave diving history.
The Gavin continues to be the tool of choice for serious explorers and is the benchmark to which all modern
DPVs are compared.
The DPV an Historical Perspective | 7
I n t r o d u cti o n
8
Introduction 
Getting Started
DPV Considerations
A Diver Propulsion Vehicle (DPV), more commonly referred to as a scooter, is
one of the few SCUBA purchases you will make that has such a high fun quotient. These truly amazing vehicles can provide less gas consumption and greater
maneuverability while expanding a diver’s reach as compared to swimming. These
amazing freedoms come with a price tag, however, and the price you pay is relates
to two primary factors:
D a n ge r
• The logistics of diving become more complex; and
•
The nature of DPV diving allows divers to very easily overextend their capacity.
Zone
The last factor can have the most
impact of all. An unskilled diver
can be a hazard at any depth.
Before addressing the preceding items, we should outline the scope and purpose of
this course. We will first look carefully at the inherent dangers of scuba diving in
general and then consider how this new piece of equipment affects these parameters. In general, we can state that all forms of diving carry risk; we are placing
ourselves in a medium where we cannot breathe without the use of life-support
equipment. A partial list of risk factors would include the following:
• Barotraumas
•
•
•
•
•
Out-of-gas emergencies
Decompression
Equipment failure
Human error
Environmental issues (e.g. current/cold, etc.)
While considering these risk factors, we will determine our relative exposure to
these risks. Since we previously agreed that diving, even in its simplest form, bears
some risk, we will attempt to determine what overriding elements control our
exposure to these risks. In their simplest form, three factors most notably impact
our exposure to risk. These are as follows:
• Depth
•
•
Time
Skill
DPV Considerations 9
So how do these factors control our exposure to risk? The first two, depth and time,
are relatively self-evident; the deeper we go and the longer we stay, the less time
we have to react to stressful situations. The last factor can have the most impact
of all. An unskilled diver can be a hazard at any depth.
Now that we have verbalized some of the risk factors and how they may be exacerbated by depth, time, and lack of skill, we can ask ourselves how the addition of
a DPV can influence these factors.
The most dangerous characteristic of a DPV is that it
acts like a magnifying glass:
If you are going to get into
trouble, a DPV will easily let
you get there quicker.
The most dangerous characteristic of a DPV is that it acts
like a magnifying glass across a range of diving variables
(speed, distance, maneuverability, gas extension) and as
a mask for the inherent limitations of DPV operation. If
you are going to get into trouble, a DPV will easily let
you get there quicker. For example, if we enumerate the
list of factors discussed previously we have the following.:
Barotraumas
A diver can incur a lung-expansion injury with a depth
change as little as three feet. With a DPV, a change in
depth can be made virtually instantaneously.
Running Out of Gas
Time flies when you are having fun and a DPV is a very captivating device; it forces you to focus attention on the act of driving. This narrowing of focus naturally
results in a diver who can be more easily inattentive to the external environment,
including effective management of gas supplies.
Decompression
Bottom times can be unexpectedly increased through DPV failures or poor time
management. Meanwhile, decompression ceilings can easily be broken by inattentive divers moving at a high rate of speed.
Equipment Failure
Given the potential distance from an entrance or diving boat, equipment failures
may take on greater significance. In addition, certain problems such as a runaway
DPV can be dangerous and/or difficult to resolve.
Human Error
A lack of awareness regarding the acceleration of risk factors associated with DPV
use can increase the likelihood of accidents.
10
Introduction Getting Started
Environmental Issues
A DPV acts to extend our natural capacity, allowing us to overcome limitations
such as distance, currents, and depth. These enhancements are positive until the
point of DPV failure; a failed DPV leaves divers to resolve the challenges of a
potentially dangerous environment
Skill
The last and certainly most important piece of the puzzle relates to individual capacity. The effective management of a DPV can require notable personal skill. This
is particularly important as a DPV can mask personal deficiencies. For example,
a diver with poor buoyancy control may use the DPV to overcome this weakness.
If you are a little heavy, pitch it up; a little light, pitch it down. Even very experienced divers can suffer from skill degradation when they use DPVs for extended
periods of time.
What have we discovered?
The preceding discussion serves to illuminate the risk/benefit nature of DPVs. On
the one hand, a DPV offers an exceptional array of benefits; on the other hand,
it provides just enough rope to hang to shoot ourselves in the foot. Therefore, in
keeping with the spirit of GUE training philosophy, we will start with the basics
and build an understanding of our abilities as well as the limitations of a DPV.
This is necessary in order to effectively manage the safe operation of your DPV.
This is ultimately the purpose of this course.
GUE DPV Programs
GUE has two DPV programs structured to encourage learning that is consonant
with the pilot’s skills and aspirations.
DPV Level I Diver – This course is designed for divers enjoying their initial
exposure to DPV diving. Minimum requirements are listed in detail in the GUE
Standards Manual Section 2.4.4; essentially these require passing a GUE Fundamentals course with 75 total dives and 50 beyond Fundamentals certification. This
program is an introduction to the DPV and is the focus of this manual.
DPV Level 2 Diver – This course is a hybrid course supporting divers in the tech
and/or cave environments. Tech divers learn advanced DPV handling and logistics as well as advanced gas management techniques. Following completion of the
Level 2 program, divers may pursue an additional module for diving in an overhead
environment. Minimum requirements are listed in detail in the GUE Standards
Manual Section 2.4.5. The OW (Tech) portion of this program is designed as a
three-day course; the overhead module requires an additional three days. Divers
taking the entire program with the cave environment can complete the training
entirely in a total of five days.
GUE DPV Programs 11
Course Structure: DPV Level I Diver
This course follows the typical GUE methodology, including the following:
• Technique and skill refinement; and
•
Team building and skill development
Comprehensive diving theory that will encompass:
•
•
•
Advanced contingency planning techniques;
Equipment handling procedures; and
Thorough academic and skill reviews.
This training is designed to gradually increase your level of comfort, competence,
and confidence by providing sufficient diving experience and a thorough knowledge base. To accomplish this goal, GUE employs a well-structured approach,
combining equipment familiarity, detailed education, and practical experience.
Training Limits
•
•
•
•
Diving within minimum decompression guidelines
Use of 32% nitrox with a PPO2 limit of 1.4 or less
Equivalent Narcotic Depth (END) of less than 30m/100ft
Maximum training depth of 18m/60ft
Timetable
A course timetable will be presented by your instructor during course commencement. The schedule represents a reasonable target regarding time and order of our
training activities. However, environmental conditions and regional considerations
frequently require adjustments. Be prepared to be FLEXIBLE!
Course Structure
The DPV Level 1 program is usually taught over a three-day period through a combination
of presentations, land exercises, and in-water sessions. The presentations are as follows:
Classroom Presentations
1. Module 1
•
•
•
GUE Overview
GUE Diver Training
Course Overview
2. Module 2
•
•
12
The Evolution of DPV Diving
DPV Breakdown
Introduction Getting Started
•
•
Maintenance
Testing
3. Module 3
•
•
•
Situational Awareness
Breathing Gas Requirements
DPV Planning
4. Module 4
•
•
Operation and Driving Techniques
Dealing with Emergencies
Land Exercises
Land exercises provide an opportunity for the diver to practice certain procedures
in a dry environment. This allows the diver and team additional time to practice
skills without the time pressure and communication challenges imposed by being
underwater. Land drill sessions are as follows:
• DPV Preparation
•
•
•
•
•
Team Formations
Communication
Problem Resolution
Contingency Planning
Line Management
In-water Practice
The last component of DPV training involves in-water practice. Your GUE instructor will balance these training components in accordance with the demands of the
environment and your particular requirements. However, you will likely notice a
bias towards in-water training. It is our sincere belief that you cannot learn how
to dive unless you are in the water and you should dress accordingly. Remember
our insistence that a DPV acts like a magnifying glass and consider the thermal
implications of diving in cold to moderate temperature conditions. Taking into
account the limited movement while riding a DPV and compounding this effect
with the cooling that results from moving through the water, you will find that
driving a DPV can be a very chilling experience.
GUE DPV Programs 13
The in-water sessions are as follows:
• Session 1: Set up and maneuvering techniques
•
•
•
•
Session 2: Out-of-gas (OOG) Scenarios
Session 3: Maneuvering techniques
Session 4: Skill Review
Session 5: Experience Dive (Optional; if time allows)
A detailed description of the in-water sessions is included as Appendix A.
With the housekeeping over and with no further ado, we will move on to the exciting stuff—playing with these wonderful toys. Get ready for some fun, be prepared
to get your hands dirty, and begin learning how to integrate the nuances of driving
a DPV into your normal diving repertoire.
14
Introduction Getting Started
Notes:
GUE DPV Programs 15
1
C hapte r
16
Chapter 1 Chapter 1
Components, Balance, and Trim
Getting Familiar
Before we delve into the intricacies of piloting a Diver Propulsion Vehicle (DPV), it
is important that we learn what goes into it, how to take it apart, and what type of
maintenance to do over what period of time. While these materials may reference a
particular brand, the general principles that we will be discussing are, for the most
part, applicable to all DPVs regardless of the specific type of vehicle. There is a collection of appendices included in electronic format with this manual that document
the maintenance and parts of as many types of DPVs as practical at the time of publication. Please refer to them to see if your DPV is included.
The first step in gaining familiarity with a DPV is tearing your very expensive machine
to pieces and putting it back together, hopefully in working and water-proof condition. The teaching pattern that is going to be employed in this manual is consistent
with typical GUE/DIR philosophy—that is we will start with the simple and move
to the more complex. Gaining an understanding of the construction and mechanics
of your DPV will enable you to spot and fix issues before they become an in-water
problem, which is definitely the attitude we wish to encourage while dealing with
these devices. The following outline provides an overview of the core issues useful in
evaluating a particular design.
Reliability
The DPV must be manufactured and maintained in a manner that will afford an
appropriate blend between performance and reliability. The benefits we gain from
DPV use, such as extended range and lower gas consumption, can expose us to
great danger in the event of a DPV failure. Proper planning, as you will learn in the
coming chapters, reduces the risk associated with a DPV failure and is particularly
important for inexperienced DPV users. We dive with the confidence that our DPV
will not fail, but plan that it will.
Parts
Nothing kills a DPV dive quicker than a failed propulsion vehicle. Of course, failures
that are discovered as part of a pre-dive test minimize risk and provide a chance to
reconfigure the dive plan. If a team employs a standard DPV, a common repair kit
can be used. In fact, a team of divers with the same DPV may even cannibalize a
spare DPV to get at least part of the team in the water. You do not what to be waiting for months to receive that left-hand thread widget to arrive from halfway around
the world. For some divers, that is the whole dive season.
Getting Familiar 17
Tow-behind and Ride-on Designs
The two primary DPV styles are the tow-behind and the ride-on. Tow-behind scooters
are usually clipped to a diver’s crotch strap; the diver rides behind and slightly above
the DPV. The tow-behind option provides a range of benefits including reduced inwater profile and better emergency towing options
to combat failed DPVs. Divers pilot ride-on scooters
while mounted on top of and forward of the motor
shroud. Ride-on designs are not suitable for GUE
training. (Fig 1.1)
Variable Speed Adjustment
Figure 1.2: Gavin pitch
adustment
Speed control is accomplished via a Figure 1.1: Farallon Mk 7-E
constant speed prop that allows pitch
control or by a potentiometer that controls the speed of a fixed set of
blades. An adjustable pitch design prop has a motor that turns at a constant rpm until you release the trigger or run out of power. You adjust
the speed by setting the pitch of the prop—the higher the pitch, the
faster the speed. One benefit of adjustable pitch motors relates to reduced
complexity; they have fewer electronic controls. One must weigh this
against greater difficulty in matching speed with other divers and the
arguably more advanced options available with electronic controls. For
example, speed can be set precisely with electronic controls. Should the
latter be used, one must consider options for using the scooter (or disengaging it during a runway) in the event of a flood.
Clutch
A DPV should have a clutch that is designed to “slip” when sufficient pressure is
applied to the blades. This prevents damage to the motor and diver in the event
something blocks the blades. The clutch will slip and allow the motor to spin while
the blades remain still. This is particularly critical in the case of a runaway DPV,
i.e., where conventional controls prevent the motor from stopping. A scooter with a
clutch can be stopped either by hand or by using something to stop the motor from
turning (the tow leash is one consideration). Another option allows the diver to disengage the power to the motor; this option will stop an uncontrolled scooter. This
latter control, if used, should be mechanical in nature as the failure might be related
to a flooded DPV and electronics may not be functional. Regardless of the method
for managing a runaway DPV, clutches remain useful in the prevention of motor
damage when foreign objects such as line or debris are introduced to the propellers.
Tow-cord Attachment
The typical “three o’clock and nine o’clock” attachment positions refer to a scooter at
rest. Under power engine torque encouraging the DPV to rotate counter-clockwise.
18
Chapter 1 Components, Balance, and Trim
Depending on the type of DPV, while immersed and not under power, the handle(s)
of your DPV should be either horizontal with the trigger handle on the right or in
the ‘up’ direction. This position is greatly affected by battery position balancing.
Attachment Methods:
•
•
•
Permanent—In this configuration the leash is adjusted for the pilot and then
the pivot point (bolt snap) is secured in such a manner as not to slip on the
leash.
Semi-permanent—In this case, the pivot point may
be retained but can be adjusted with a minimum of
effort. This allows a fixed position for the clip when
desired but provides the option to slide the clip and
adjust the position of the DPV relative to the diver.
Free Running—This configuration allows the bolt
to slide freely on the tow leash, reducing stability
but increasing ease of movement.
Note: You will have an opportunity to try all of these
configurations to decide which you prefer and the pros
and cons of each.
Figure 1.3: DPV tow cord attachment
Now that we have a sense of the key aspects of DPVs, let’s have a look at the general
composition of most DPVs.
General Composition of a DPV
Components
•
•
•
•
•
•
Nose Cone
Body Tube (Battery Compartment)
Tail Cone (Motor Compartment)
Shroud
Handles
Trigger Mechanism
Note: Some DPVs such as the Farallon and the X-Scooter have the nose cone and
body as a single unit. This feature eliminates one major O-ring.
DPV Materials
Typically the body, clutch, nose, and tail cone are constructed of a machined or
molded polymer such as HDPE. This reduces weight and simplifies construction.
Aluminum is also a favorable material given its low weight and high strength. It may
be used throughout a particular design or used for support within certain parts (such
General Composition of a DPV 19
as on legs that support the shroud). Motor compartments require a design that dissipates heat. This is usually accomplished with an aluminum part of the motor that
is in contact with the water. The motor compartment is typically separated from the
battery compartment to reduce the risk of damage should water enter the scooter.
Disassembly
Now we get to the hands-on fun—taking the unit apart! Let’s see what makes it tick.
When disassembling your DPV, always work in a clean area, if possible, and get into
the habit of laying the parts out from left to right. This makes reassembly a fairly
straight-forward process, particularly when the breakdown becomes more complex.
See the accompanying diagram. (Fig 1.4)
1. Stand the DPV on its tail.
2. Remove the nose cone and/or body. If your DPV has latches, be careful not to
damage the fixtures or the sealing surfaces.
3. Remove the battery pack.
4. Remove the motor compartment cover. Some designs have wires and electronics
attached to this lid, so be cautious with this step.
5. Carefully remove all static O-rings and set aside for inspection.
At this point you have disassembled the unit as far as necessary for routine maintenance, so for practice let’s put it back together.
Figure 1.4: Gavin-Component disassembly for inspection
20
Chapter 1 Components, Balance, and Trim
Reassembly
The process for reassembly is the reverse of disassembly:
1. Install and secure the motor compartment cover.
2. Vacuum test as required.
3. Inspect and/or replace the lower body O-ring.
4. Stack the battery pack on top of the motor housing, taking care not to damage
any wires or electronics.
5. Slide the body over the battery pack and motor compartment, taking care to en-
sure lower body O-ring seals properly.
6. Secure the body as required. If your DPV has latches, note that it is preferred to
latch opposing latches at the same time.
7.Replace/inspect the O-ring of the nose cone where appropriate.
8. Replace the lid where appropriate.
Maintenance
A DPV may be many things to different people but above all it is a mechanical device
that will eventually fail. It is not a question of “if ” but rather “when.” Those that
subscribe to Murphy’s Law acknowledge that it will fail at the absolutely worst possible time. DPVs may allow the world’s leading explorers to execute amazing feats of
exploration but it is an obsessive attention to detail and careful maintenance routines
that insulate them from risk. We attempt to reduce the likelihood of in-water DPV
failure through several levels of maintenance. These are as follows:
• Routine
•
•
•
Pre-dive
Post-dive
Long term care or storage
These routines will be detailed later in this chapter. For now, let us look at how to
inspect and maintain the various components of our DPV. Disassemble your unit as
previously outlined. Stop when you have all the components neatly strewn about. As
you are taking the unit apart, you should be inspecting all parts for unusual wear,
deformations of all sealing surfaces, cracks, tightness of components, etc.
Inside the Motor Compartment
Only sophisticated users should venture deep into this compartment. In general there
is little to check here. However, we do want to ensure there are no signs of wear and
Maintenance 21
no symptoms of water and/or humidity. Moisture, corrosion,
or signs of melting are all obvious signs of potential problems.
Electronics
The most noteworthy electronic component in a variable pitch
scooter such as the Gavin is the relay. As with all components,
relays do eventually fail; they can also become mechanically
damaged. Many apparent relay problems are motor problems
Figure 1.5: Motorcompartment
in disguise. Motor repairs should always be referred to the
manufacturer or to a registered agent. Be aware that you may
void the warranty by working on your own motor. The relay
should be secure to the board and the leads to the brush boards
should be soldered securely to the circuit board.
Figure 1.6: Relay and wiring
Scooters with electronic controls typically have a larger circuit board that controls speed and general operation. These
components should be free from obvious signs of corrosion,
as well. The compartment should be free from moisture without any signs of rust or contamination. Some DPV designs
provide mechanical override options. You should review the
operation of these devices and ensure they are functional and
appear to move freely.
Motor Connections - Internal
When checking connections under the motor cover, use care not to disturb any connections. For example, the motor compartment plugs on the Gavin are threaded; to
tighten them you must hold both sides of the fitting. Otherwise, the fitting will rotate
in the opposite direction. Make sure these fittings are tight so that no intermittent
behavior will be displayed by the DPV.
O-rings—Motor Compartment
Be sure to reference the manufacturer’s recommendation regarding O-ring size and
maintenance. Most dynamic O-rings require lubrication, though static O-rings such
as those used on a typical face seal do not. Do not use hydrocarbon sprays near or in
the motor compartment as the propellant may ignite when you start the motor. Make
sure your O-rings are “alive” and not “dead”—that is not flat or losing their resilience—or damaged so as to leak. Be sure the compartment lid is secured prior to use.
Some motor compartment designs allow for a negative pressure test (vacuum test)
that helps identify the potential for leaks (see Testing, this book). It may be easier to
remove this plug when closing the motor compartment as this reduces the build-up
of pressure. This plug is also a convenient way to verify that the DPV is free from
water. This prevents the user from removing the motor compartment with any regularity. To check the motor compartment for water contamination after diving, it is
best to just remove the testing port and check for water, instead of removing the lid.
22
Chapter 1 Components, Balance, and Trim
O-rings—Main Body
Two main sealing types are relevant in DPV designs; static and dynamic. A static or
compressed O-ring sits between the sealing surfaces. Any damage to the O-ring or
sealing surface is problematic. However, it is easy to inspect for cracks and/or flat
spots. While in use, these O-rings are highly compressed between the sealing surfaces of the DPV. These O-rings should never be lubricated as the lubricant attracts
sand and small particles of grit that will be ground into the O-ring material during
compression. The sealing surfaces of the DPV should be cleaned with a soft brush
and inspected for any grit or physical deformity prior to assembly.
A dynamic O-ring seal is captured and does require lubrication. The advantages to
this design are a reduction in pressure upon the O-ring and the elimination of DPV
buoyancy changes when the O-ring is compressed. However, one must be careful
not to allow dirt or debris to accumulate on the O-ring as this could allow water to
intrude. These O-rings should be maintained by keeping them clean and lubricated.
As with all O-rings, they should be changed if they show any signs of wear.
You should be aware that a recently charged scooter can release flammable gases (the
risk and the type of gas vary among batteries). Batteries that are charged outside the
scooter can off-gas easily, eliminating combustion problems. However, when charging within the DPV body, you should avoid sealing the body immediately. If you
are required to transport the unit shortly after charging, you may consider leaving
the lid O-ring off the nose. Be sure to replace this O-ring before placing the DPV
in the water.
Testing
Blades
One consideration in the use of variable pitch DPVs is that the blades will eventually wear out, reducing the speed of the vehicle. To test your blades, set the speed in
the middle range and check for sloppiness. There should be little or no movement in
the blade; they should not wiggle. If movement is noticeable, disassemble the upper
blade assembly (see Fig 1.11) and check the blade pin and head for wear. Replace
worn parts as required.
Fixed blade, variable-speed DPVs do not show the above-mentioned wear. Yet, these
blades should be checked for wear or signs of damage. Cracks or unusual movement
should be managed appropriately and replaced as required.
Clutches
The DPV clutch needs to slip easily. This is especially critical for scooters that do
not possess a way to disconnect power to the motor. Be warned that a clutch that
fails to engage may damage the relay. In order to test the clutch, hold the prop and
tap the trigger. It should slip instantly. Occasionally when the clutch has tripped, it
Testing 23
will ride on top of the clutch-plate and you will have to engage the trigger a couple
of times to get it to reseat.
The Motor
Some DPV models contain a port plug that may be used for vacuum or
pressure testing. To test the vacuum, remove the hose from the special
test plug and screw the plug into the port in the motor compartment. Reattach the hose and pump it down to negative 15 inches of vacuum and it
should hold indefinitely. If it does not hold, consider returning the unit to
your manufacturer. It is possible to use the same pump to pressurize the
compartment, using immersion or soapy water to locate the leak. Consider
the following potential leak locations.
•
Damage to polymers
•
•
Figure 1.7: Testing
the
clutch
•
Damage to the motor seal
Damage to O-rings
Damage to the motor compartment/cover
Batteries
Battery Types
• Lead-acid
•
•
NiMH
Lithium derivatives Li-Ion, Li-Po, etc.
Figure 1.8: Vacuum testing
Choosing a Battery
Battery technology is advancing at a remarkable pace making specific recommendations problematic. In general, lead-acid batteries remain reliable. They are not complicated and have a long track record. Regrettably they are also quite limited in their
capacity. By comparison, NiMH and Lithium offer progressing levels of sophistication with extreme energy density. These batteries require progressively more complex electronics to manage charging/discharging. The consequent benefit is improved
performance. Recent GUE DPV test models are one-third the size/weight and burn
roughly three times as long. This trend is likely to continue, requiring that you familiarize yourself with the most current options relevant to your needs. Internet discussion groups, your friendly neighborhood GUE instructor, and GUE’s Quest offer a
range of unique resources.
Pearl of Wisdom
A few common words of wisdom relate to an acceptance that batteries can be frustrating. They appear
to function well but sometimes fail prematurely for no apparent reason. They tend to tolerate heat
poorly so avoid keeping them in a hot car or storage area. Lastly, they do not mange deep discharges.
24
Chapter 1 Components, Balance, and Trim
Likewise, failure to charge batteries can damage cells. These problems are mitigated by the morecomplicated Lithium batteries mentioned above. These maintain a significant amount of protection
that prevents deep discharge and monitors the charging process, balancing cells as appropriate.
Battery Packs
The position and orientation of the battery pack greatly affects the way a DPV will
sit and ride in the water. The batteries need to be spaced properly with a way to adjust
their position (fore and aft), as well as their orientation (toward the top/bottom of the
DPV). Dedication to convenience varies with manufacturer but each unit is slightly
different. Be sure that the battery retainer does not impinge on any sealing surface.
Where a separate lid is used, be sure the lid is seated securely. One way to ensure
this is to remove the O-ring and verify the lid can seat properly.
Battery Charging/Operation
•
•
•
•
Use a charger suitable for your battery type.
A lead-acid charger will destroy NiMH batteries!
Check battery charge connectors.
Verify charge using a voltmeter.
Burn test batteries.
Use the charger recommended by your manufacturer. A variety of suitable options
exist for lead-acid batteries. Be sure you are using the proper voltage (usually 24 volt).
Verify battery charge with a multi-meter set to amps/dc; move the non-com plug to
the amp slot and then clip in between one side of the circuit (you will need to jumper
the other side) and turn on the charger. If it will not take current and the charger is
reading voltage, then it is charged. You can check the charger for volts first and then
the battery, then the amps, and then the resting voltage of the battery.
Multi-meters
Purchase and learn how to use a multi-meter. Not only is it a must-have tool for DPV
owners, it allows you to check your primary and backup lights before every dive as
well. The continuity function will tell you if your reed switch is working, the ohms
will tell you if your relay is welded, the amps will tell you if you motor is drawing
the right amount of current and hence has no problems, and the volts... you guessed
it, will tell you the resting voltage of your batteries, which you will know is what it
should be or not.
Burn Testing
Burn testers are commercially available however it is easy to build one yourself. What
you require to build one is:
• Resistors
Batteries 25
•
•
•
Power cable
Metal stand
Battery power connector
Battery Burn-testing Procedure
•
•
•
•
•
Fully charge battery and note the resting
voltage.
Verify charge using a voltmeter.
Connect the battery to the burn tester.
Note the time it takes for the battery voltage to
drop below 20 volts.
Label the battery with the verified burn time
and date of the test.
Figure 1.9: Burn Tester and automatic voltage
cut-off timer
Note: Never ever leave a discharging battery pack
unattended unless you have an automatic voltage cutoff unit (Fig 1.9). Deep discharge of your battery pack can severely reduce burn time.
Uncontrolled discharging can potentially lead to fires and explosions.
Battery Maintenance
•
•
•
Store dry at room temperature.
Occasionally trickle charge when stored long term
Avoid deep discharge.
Motor Rotary Seal
The first sign of a worn motor seal is the presence of water in the motor compartment;
a slight leak detected during a vacuum test is also a possible indicator. Replacing a
seal is best done by a trained technician who will do the following:
• Disassemble to the rear end. (Fig 1.10 and 1.11)
•
•
•
•
•
•
•
26
Remove the seal with channel locks.
Remove the inner donut with an O-ring pick. (* The snap ring is under the
inner donut.)
Check and be sure that the ring is in place.
Place the new donut into the hole without silicone or lubricant.
Spray the bell side of the seal with lubricant.
Put a drop of motor oil on the donut.
Slide the bell down, press the rubber ring down with a flat-head screwdriver.
Chapter 1 Components, Balance, and Trim
•
•
Add the spring, cap, and stainless snap ring.
Run the motor for a couple of minutes to break in the seal.
Note: You do not need to take the motor out of the DPV
to replace the seal.
Figure 1.10: Clutch assembly detail
Figure 1.11: Lower unit exploded view
Batteries 27
Maintenance Schedules
As discussed, we accept the inevitability of DPV failure but strive to reduce the frequency and consequences through several levels of maintenance.
Technical Protocol
If the DPV is to be used during an operation involving overhead environments or
similar scenarios, a more thorough test is mandatory. This test includes the following inspections.
• Battery burn test
•
•
•
•
•
•
•
Battery charge test
Motor compartment integrity test
Visual inspection of all O-rings
Visual inspection of all cables and connections
Clutch test
Relay and reed switch test
Trigger test
Recreational Protocol
If the DPV is to be used during a non-DPV dependant operation, a basic DPV functionality test is justified.
• Battery charge test
•
•
Visual inspection of all O-rings
Trigger test
Post-dive Normal Care
The DPV demands proper and regular maintenance. The following points of DPV
care are to be performed after every dive.
• Rinse in fresh water.
––
––
•
•
•
•
•
28
This removes sand and other particles.
This removes salt and prevents corrosion.
Run the engine while rinsing the propeller assembly.
Lubricate the shaft with WD40 (Hydrophobic).
Check for leaks.
Remove O-rings.
Clean.
Chapter 1 Components, Balance, and Trim
Long-term Extensive Care
On a regular basis, more extensive care may be considered to maintain DPV performance and reliability.
• Inspect and clean the clutch area.
•
•
•
•
•
•
•
Remove engine, blow carbon dust.
Check O-rings.
Check latches and screws.
Check reed switch/relay/electrical connections.
Vacuum test.
Burn test batteries.
Check motor compartment.
Figure 1.12: Proper DPV cradle
Storage and Transportation
The DPV should always be stored and transported in a secure manner (Fig 1.12) as
batteries can explode and cause fires. For storage and transport, a DPV should be
handled as follows.
• The battery pack should be disconnected.
•
•
•
•
The trigger should be pinned or deactivated.
The prop or speed control should be set to zero thrust.
Use a DPV tray/protection during transportation and storage.
Never leave a DPV in the sun for any extended periods.
General Considerations
The motor should never get hot. Heat indicates a waste of valuable battery power;
more importantly it is indicative of a developing problem. To reduce the risk of overheating and/or general damage consider the following:
• DO NOT spray any conductive lubricant into the motor.
•
•
•
•
DO dive a streamlined gear configuration and maintain proper body position
to keep from giving the DPV too much drag.
DO check the motor temperature from time to time when using the DPV by
touching the tail cone.
DO NOT deep discharge the DPV or otherwise abuse its integrity.
DO NOT handle batteries carelessly.
Storage and Transportation 29
Balance and Trim
Now that we have a reasonable overview of the disassembly/assembly and maintenance of a DPV, let’s discover how to establish a well-balanced DPV.
A properly balanced DPV is a true joy to ride while a badly balanced unit is one that
you will wish you never took in the water. Poorly balanced DPVs can be extremely
fatiguing as well as cause perceptual narrowing while increasing risk. Conversely, a
well-balanced unit requires minimal effort.
Proper Weighting and Ballast Control
A DPV is typically designed to be buoyant in the water prior to any adjustment.
In other words a DPV, with no extra weight and stock batteries, should float in the
water. This design consideration allows for a number of variables, including changes
in battery weight, salt vs. fresh water diving, and personal weighting preferences. If
your DPV is negative in a stock configuration, the only alternative is obtaining a
slightly longer body. In our case, let’s assume we have the appropriate situation and
your DPV is slightly buoyant.
The purpose of proper weighting is discovering exactly how much extra weight you
need to create a DPV that is neutral in the water. We are trying to discover the weighting for the vertical (up/down) component in the water column. The solution is rather
low tech but may require patience. The procedure is as described below.
Prior to attempting these adjustments make sure your trigger is pinned or scooter
deactivated.
• Obtain an assortment of small lead weights. Some manufacturers include these
as part of your DPV; alternatively, you can use fishing weights or other convenient lead pieces.
•
•
•
•
Slowly add weight until the DPV barely breaks the surface (Fig 1.13); adjustments from this point depend upon your weighting preference; i.e., slightly
buoyant, slightly negative, or perfectly neutral.
You can use bands around the DPV to hold the weight temporarily till the correct amount is found.
If your DPV is not horizontal, you may adjust the weight fore or aft until you
get the desired orientation.
It may be necessary or easier (depending upon the DPV) to adjust the battery’s position (fore or aft); large changes in horizontal trim will require this
adjustment.
This process can be accomplished fairly quickly and provides you with important
information. You know how much weight you need as well as how the weight needs
to be distributed in order to achieve appropriate trim.
30
Chapter 1 Components, Balance, and Trim
Figure 1.13: Position on the surface for a properly weighted and trim DPV
Trim Position
There is no perfect trim position—that is, one that will make all divers happy. Your instructor will discuss various positions though divers tend to prefer a scooter that is either perfectly horizontal or very
slightly “nose up.” Divers also tend to prefer their right handle (usually the trigger handle) between
twelve and three o’clock.
If weighting takes care of the vertical axis, then trim takes care of the horizontal. This refers to the
pitch angle the DPV would rest at when not under power. We have two primary means to trim our
DPVs. We have the amount of extra weight we determined in the previous set and the position of the
batteries. If the DPV is not in proper orientation, we must move the battery position forward or aft as
required. Nose down, move the batteries back. Nose light, move the batteries forward. This process
may take some effort so have patience and keep going until you get it right. (Fig 1.14)
In order to adjust the weighting, you may use the supplied ballast or locate appropriate weighting and
fix the weight to the unit. The weight may have a preferred location determined by the manufacturer
or you can adjust according to your preference. If necessary, you can use some of this weight to further
Balance and Trim 31
tweak the nose up or down orientation. DPVs with face seal O-rings, for example
the Gavin and Silent Submersion, will lose some buoyancy at depth. This is the
result of the compressed O-ring. In this case, it may be advisable to make the
DPV very slightly buoyant on the surface and then test it at depth. Typically you
will choose a very slightly negative DPV at depth. When you release the DPV, it
should very slowly sink beneath you until it reaches the end of the leash. It should
remain in a horizontal position.
Note: Changes in density between fresh and salt water require minor adjustments
of the DPV weighting. It is possible to add some additional weight to the nose,
but this will likely create a nose-down position in the water. You could adjust the
batteries aft to account for these changing conditions or add the weight near the
rear or middle of the DPV.
Once your DPV is properly weighted, the last issue you may have to deal with is
roll. This is rotation around the horizontal axis. If you have an older DPV, this
may be a bigger issue, as the battery packs themselves
were not balanced, making it very difficult to properly determine the battery center of gravity. In most
modern DPVs, this is not as much of an issue, as the
batteries are indexed to a particular location and/or
designed to be easily adjusted.
A properly balanced DPV should have the handles
resting at three o’clock and nine o’clock with the trigger on the right facing down. That means the DPV is
heaviest on bottom or at the six o’clock position (Fig.
1.13). When you hit the trigger and keep it activated,
the torque produced by the motor will cause the right
handle (trigger handle) to rotate counter-clockwise,
Figure 1.14: Loosen nuts and slide the btty pack to
establishing a trigger position between twelve and
adjust horizontal trim position
three o’clock, which is ideal. As your instructor works
with you to set up your DPV, this is the weighing,
trim, and balance you will try to achieve. You must strive to neutralize the vertical, horizontal, and roll tendencies of a DPV. When adjusted properly, DPVs are
an absolute joy to pilot. If any of these dimensions are out of kilter, they can range
from annoying to incapacitating.
Now that we have the boring side of working with a DPV out of the way, we invite
you to turn your attention to the upcoming chapter. Here you will finally get in
the water with your instructor and start to learn the fundamentals of driving a
DPV, such as situational awareness, DPV planning, and different DPV techniques.
We hope you agree that the combination of GUE’s step-by-step process and a
thoroughly experienced GUE instructor will provide you with the best learning
experience available.
32
Chapter 1 Components, Balance, and Trim
Notes:
Balance and Trim 33
2
C hapte r
34
Chapter 2 Chapter 2
Planning and Gas Mangement
Awareness
Having gained familiarity with your DPV and having had the
enjoyment of tearing it apart (and putting it all back together!),
it’s time to put it aside for a moment and consider the impact a
DPV has on diving and dive planning. It is important to understand how using additional, complex equipment will affect our
diving, and to think about the additional parameters that need
to be managed while conducting diving operations with a DPV.
Situational Awareness
From your prior GUE training, you should be familiar with the
concept of situational awareness. It involves being aware of what
is happening around you to understand how information, events,
and your own actions will impact your goals and objectives, both
now and in the future. When diving, situational awareness is
the umbrella term for constantly managing the environment,
the equipment, and the team.
Learning to divide your attention while simultaneously managing an array of sensory inputs is vital to successful diving operations. Divers must let their focus rotate between the environment, their equipment, and the team while always being alert
to any changes. Developing situational awareness allows one
to become more efficient, be safer, and have more fun diving.
Anytime additional equipment is added to a dive, or as the
complexity of a dive is increased, divers will be challenged to
maintain their current level of situational awareness. This is
particularly true when using a DPV, as you will no doubt find.
A DPV allows a diver to move quickly, approximately three times
as fast and, consequently, cover greater distances in relatively
short periods of time. This combination of increased speed and
travelling further in a reduced amount of time can allow simple
problems to quickly escalate into more serious situations. It is
important to recognize this and allow situational awareness and
experience with the DPV to develop over time.
Equipment
Environment
Team
Pearl of Wisdom
Good situational awareness prevents
small problems from escalating into
unmanageable situations. Divers
must strive to prioritize and manage
problems using correct procedures
and techniques.
Awareness 35
A review of many of the aspects of environmental, equipment, and team awareness
will help you understand how the DPV impacts situational awareness.
Environmental Awareness
Aquatic environments are very dynamic and can vary drastically from moment to
moment. The addition of the DPV makes them more so. Identifying and monitoring
environmental parameters that can increase risk due to change is critical in managing environmental awareness.
Depth
Knowing current, maximum, and average depths is important in conducting safe
dives. Naturally, this remains so while using a DPV; however, changes in depth can
now be larger and occur faster.
Time
Knowing how much of the planned bottom time has elapsed is the first step in managing time. Divers must also be aware of when it is time to call a dive based on other
factors such as available DPV burn-time and surface-support expectations of total
run time and estimated time/place of surfacing.
Gas Management
To maintain proper breathing-gas reserves, divers must both verify their gas supply
and check this against their depth and time to track gas consumption during the dive.
When first using a DPV, you may notice a slight increase in your SCR, but over time
this should improve and become lower than your swimming SCR.
Decompression Management
Decompression management is contingent upon a number of factors including bottom time, average depth, environment (e.g., ocean vs. cave), available gas supply, time
of day, team training, and experience.
Distance
Awareness of how far a team has travelled and the distance to a planned or alternative exit point is an important factor in properly managing available bottom time
and breathing gas. Using a DPV allows a dive team to travel significantly greater
distances, and dive planning must account for this and for the additional time to
return swimming and towing a failed DPV.
Navigation
Different environments demand different types of and proficiency with navigational
skill. Navigation is an essential skill for diver safety and all divers should be aware
of the direction in which they are travelling and their orientation from the entrance
36
Chapter 2 Planning and Gas Mangement
and exit points. It is also important to develop proficiency with specialized navigation skills, including compass and line navigation, and to integrate the use of a DPV.
Environment
Divers need to be aware of the information the underwater environment provides
about currents, temperature, visibility, surface conditions, and potential hazards
(lines, nets, debris, etc.). Divers need to remain aware of, and constantly interpret,
their environmental surroundings.
Entanglement
Even with a streamlined GUE equipment configuration, divers remain at risk for
getting entangled in fishing lines, anchor lines, lift bags, debris, etc.
Divers need to remain aware of such risks and protect themselves and their equipment from entanglement by choosing safe and clear routes and carefully checking
for entanglement hazards. Entanglement is particularly hazardous around the DPV
propeller and you will learn a process to effectively check them before pulling the
trigger and using the DPV.
Equipment Awareness
Equipment awareness aids problem resolution, encouraging safety and efficiency
during critical diving emergencies.
Team Resources
All equipment on a dive are team resources and divers must strive to remain aware of
both their personal and other team members’ equipment to ensure it is available if/
when needed. A DPV can be used to tow team members or additional/reserve DPVs.
Verification
Equipment should be systematically verified throughout a dive by monitoring operation, capacity, and reserves. This can be accomplished in various ways, including
gas-consumption tracking and tracking of DPV burn times.
Malfunction
Malfunction of equipment must be accurately and efficiently resolved with each
diver remaining aware of the team’s equipment capacity. Just like your other equipment, there are problems with a DPV that can be fixed underwater and others that
will necessitate calling the dive.
Equipment Awareness 37
Streamlined Storage
Proper storage of equipment improves streamlining and efficiency, reduces entanglement risks, and ensures equipment is not lost or inaccessible. Streamlining significantly increases efficiency when using a DPV.
Team Awareness
Team capacity is limited by experience and education as well as clarity in the assignment of responsibility.
Capacity
The success of any dive operation is dependent upon the divers’ capacities as individuals and as a team. By monitoring factors such as mindset, possible impairment
from narcosis, workload/effort, and ability during the dive, the team is better able to
facilitate proper decision-making.
Responsibility
Divers may have many responsibilities during a dive and divers should gauge each
others’ capacity and should support team members in the responsibilities that have
been assigned to them.
Dive Plan
The dive plan must be communicated to the entire dive team (divers, surface support,
boat captain/crew) and all must remain observant of how the dive is being executed
in comparison to the predetermined plan.
Protocol
Divers should stay alert to team members’ ability to follow proper procedure and protocols. Any deviating behavior might be a symptom of stress or discomfort.
• Communication
––
––
•
Awareness of team formation requires interpreting the environment and
making decisions on positioning the team whilst maintaining team integrity
and proximity.
Problem Resolution
––
38
The dive team must be aware of all communication (active, passive, written, touch) to ensure team integrity and be able to respond to individual and
team needs underwater.
Team Formation
––
•
Strong communication is an important component of efficient team diving.
Efficient and effective problem resolution requires early detection and the action of a well-focused, unified team. The ability to offer timely assistance and
Chapter 2 Planning and Gas Mangement
respond to a problem requires a high level of awareness. Divers must be alert
to additional problems that are likely to occur for a task-loaded diver and be
prepared to respond to them. Strong team awareness and effective problem
resolution may inhibit problems from escalating.
Dive Planning
Diving operations begin long before divers enter the water. Preparing and planning
for a dive is paramount to any successful diving operation. Appropriate dive plans
consider a multitude of complex variables toward producing a simple, efficient, and
safe dive operation.
Dive planning allows a dive team to establish necessary guidelines and address the
risk factors of a dive prior to the exposure. Dive planning identifies the parameters of
a dive (e.g., breathing-gas strategies, gas reserves, contingency planning) and confirms
that the dive can be safely conducted. A dive plan is therefore absolutely necessary
before venturing underwater.
Regardless of the environment or complexity of a dive, the fundamental rules for
planning remain the same:
1. Dives should be planned before entering the water and conducted according
to the plan.
2.
3.
4.
The dive plan must be communicated to all team members.
All divers must be capable of executing the dive plan.
The dive plan must be based on the capacity of the least-experienced diver.
Divers should be mindful that dynamic environments, challenging plans, and complex objectives confuse planning and increase risk. A proper dive plan should support the team objectives and insulate the divers from unnecessary risk. Dive planning
ensures the dive is safe, the objectives are achieved, and all divers enjoy themselves.
The dive planning process unites a dive team around the following fundamentals.
Team Strategies
A unified team philosophy is cornerstone in all GUE activities and the most successful, efficient, and safety-orientated approach to diving today. Team planning is
geared to the lowest level of diver experience/ability, taking into account environmental stability and complexity of the objectives.
Dive Objectives
Divers who have common goals are considerably more likely to enjoy a dive compared to less-unified groups. Divers should discuss and agree upon what they wish
to experience to maximize enjoyment for all team members.
Dive Planning 39
Procedures
All members of the dive team must be capable of safely executing the dive plan and
must have the training and experience to support other team members. Using the
GUE equipment configuration and common operating procedures allows the team
to operate efficiently and achieve the dive objectives.
Logistics
Dive logistics can often compromise pre-dive, post-dive, and dive tasks, making
logistics a high priority. Logistical planning may incorporate transportation, scheduling, gas fills, and dive-specific logistical requirements such as establishing DPV
burn times and ensuring batteries can be charged.
Dive Profile and Parameters
Determining the dive profile and associated parameters allows the team to identify
the controlling and/or limiting factors for a dive. This represents one of the most
critical components of any dive plan and defines the dive with respect to exposure
(depth and time), gas requirements, minimum gas, usable gas strategies, and decompression strategies. When using a DPV, divers will also need to calculate required
battery time for the dive profile and ensure the reserve and available DPV burn time
allow for a safe dive.
Risks and Contingencies
The dive team should identify and recognize the relevant risks of a given dive and
assess whether they are acceptable. Teams need to plan a strategy and evaluate their
capacity to manage the risks and prevent them from escalating into more serious events.
In-water and Surface Support
It is critical that support personnel are included in the dive planning process. The size
of a support team and their role may vary depending on the dive objectives; however,
they remain a fundamental safety measure for any dive.
Nutritional Requirements
It is important for divers to be well nourished and properly hydrated. Nutritional planning can be as simple as identifying the availability of food at a dive site and ensuring that appropriate (hot or cold) fluids and/or nourishment are brought to the dive.
Proper dive planning significantly influences the outcomes when dealing with problems on a dive and contributes greatly to team safety. Many of the contingencies that
are typically considered when planning a dive can become more significant when
integrating a DPV into the dive plan. Below is a list of examples; keep in mind that
this is not an all-inclusive list.
1. Loss of orientation/direction, silt-outs, and team separation
2.
40
Equipment failure (non-DPV)
Chapter 2 Planning and Gas Mangement
3.
4.
DPV malfunction or failure
Gas management issues, including hypoxia and hyperoxia
5. Hypothermia
6.
Physical injury or impairment
7. DCI
When planning a DPV dive, the planning process should include an assessment of
how the use of the DPV will influence the more common or standard risks of a dive
(team separation or hypothermia), as well as those that using a DPV will introduce
(DPV malfunction or failure). Risk assessment and contingency planning should
encourage management of such risks and associated problems.
Dive Parameters
One of the most important elements in building a proper dive plan is establishing
limitations for exposure, gas management, and—for DPV diving—power management. The dive team must recognize that, while there may be several factors that
determine the parameters of a dive, they must identify the controlling factors to
ensure none are unrealistic or beyond safe limitations.
Exposure
The dive exposure means planning the dive profile with respect to depth and time.
A dive profile may be planned on a maximum or average depth and establishing the
exposure parameters means determining how long the dive team will be exposed to
the maximum and/or average depth. A number of factors can control the exposure
including decompression limitations, breathing gas consumption and supply, training level and experience, and depth.
In determining the dive exposure and profile, divers should gather information about
the dive site—depth, site layout, and features. The dive team should then decide what
exposure parameters are desirable and establish a dive profile. Dives should always
be planned using the most conservative options.
Exposure Parameters:
1. Determine maximum and average depth.
2.
3.
Determine dive time.
Determine dive profile (time spent across various depths).
Gas Mix
Once the maximum and average depths for a dive have been determined, the appropriate gas mix to use can be determined from the list of GUE Standard Gas Mixes.
A mix should be chosen so that for the planned dive profile the maximum narcotic
Dive Parameters 41
depth of the gas and maximum PO2 will remain within GUE Standard limits of
END <100’ or 30m and PO2 < 1.2.
Gas Parameters:
1. Determine appropriate gas mix(es) for the dive.
2.
3.
Determine gas consumption.
Determine appropriate gas reserves including minimum gas.
DPV Considerations
As with all pieces of equipment we have to consider the characteristics of the DPVs
that will be used during the planned dive.
DPV Paramenters:
1. Determine DPV burn time.
2.
Determine DPV reserve.
Breathing Gas Requirements
Gas Consumption
Monitoring gas consumption and being aware of remaining gas supply is essential
in diving. Divers must be able to assess how much gas they will consume across the
planned dive profile, using their SCR as a tool to calculate the required gas supply
for a given dive profile.
SCR = Volume Consumed/Depth(ATAs)/Time(min.)
If you are not already monitoring your SCR, some standard gas consumption rates
that can be use for planning are:
• Decompression Consumption: 0.5cuft/min(15l/min).
•
•
Bottom Consumption: 0.75cuft/min(20l/min).
Consumption during Emergencies: 1.0cuft/min(30l/min).
Minimum Gas
Minimum gas is the absolute minimum gas reserve that safely allows two divers to
ascend, including safe ascent profile/decompression stops, from the maximum depth
while sharing gas.
Minimum Gas accounts for an emergency gas-sharing scenario and the ascent. Once
minimum gas is reached, the only option is to call the dive and ascend.
42
Chapter 2 Planning and Gas Mangement
Establishing Minimum Gas
To calculate minimum gas, there are a number of basic rules to follow; adjust for
conservatism if required.
1. Always add at least one minute to the total ascent time dedicated to resolve
simple problems at depth.
2.
3.
4.
The gas-consumption calculation for ascent is based on average depth between
the maximum depth and the surface.
Divers must plan for a proper ascent to first deep stop, using a proper ascent
rate of 30fsw/9msw per minute.
The first stop is at 65% ATA (~50% of the maximum depth).
5. Stops are conducted each 10fsw/3msw thereafter (lowering the ascent rate to
10fsw/3msw per minute).
6.
Calculations are based on two divers, sharing gas.
7. Use the SCR estimate for an emergency consumption.
8.
Minimum gas can NEVER be below 500psi/40BAR.
M i n i mum G a s E x a mple
Dive Paramenters(Metric):
SCR of 30L/min at a depth of 2ATAsave
Total time Requirement = 6min
0m/0ft
3m/10ft
1 Minute
6m/20ft
1 Minute
9m/30ft
1 Minute
Gas requirement:
2ATA x 1min x 30L/min= 60L/min.
6min x 2 divers = 12min required gas supply
12min x 60L/min = 720L of gas required
720L / 11L tank = 66Bar minimum gas
Dive Paramenters(Imperial):
SCR of 1.0cuft/min at a depth of 2ATAsave
Total time Requirement = 6min
12m/40ft
1 Minute
Gas requirement:
15m/50ft
18m/60ft
2ATA x 1min x 1.0cuft/min= 2.0cuft/min
6min x 2 divers = 12min required gas supply
12min x 2.0cuft/min = 24cuft of gas required
24uft/2.5(TF)x100 = 960psi minimum gas
2 Minute - Emergency
Figure 2.15: Metric and Imperial minimum gas examples
Breathing Gas Requirements 43
Minimum Gas calculations need to be flexible to account for variables such as dive
profile, individual and team capacity, and training, environment, and equipment—
DPVs!
Gas Management
Once minimum gas has been determined, the dive team is able to plan how the usable
gas will be managed. Usable gas is the total available gas supply, less minimum gas.
The usable gas management strategies for DPV 1 varies between two paradigms:
All-Usable
The all-gas-is-usable strategy is used when a return to a dive boat or a shore exit point
is not necessary and direct ascent is safe and practical.
E x a mple s All - U s a ble D i ve ( s ee F i gu r e 2 . 2 )
Metric:
• 11L tank @ 200Bar / Minimum Deco dive to 18m
•
•
•
Minimum Gas = 55Bar
Usable Gas = Starting Pressure – Minimum Gas
Usable Gas = 200 – 55 = 145Bar (Turn Pressure)
Imperial:
• 80cuft tank @ 3000psi / Minimum Deco dive to 60ft
•
•
•
Minimum Gas = 800psi
Usable Gas = Starting Pressure – Minimum Gas
Usable Gas = 3000psi – 800psi = 2200psi (Turn Pressure)
Figure 2.16: All available gas plan
44
Chapter 2 Planning and Gas Mangement
Half-Usable
The half-usable gas strategy is used for dives where return to entry point or boat is
desirable, yet not mandatory and direct ascent is safe and practical.
E x a mple s H a lf - U s a ble D i ve ( s ee F i gu r e 2 . 3 )
Metric:
• 11L tank @ 200Bar / Minimum deco dive to 18m
•
•
•
•
Minimum Gas = 55Bar
Usable Gas = (Starting Pressure – Minimum Gas) / 2
Usable Gas = 200 – 55 / 2 = 70Bar
Turn Pressure = 200Bar - 70Bar = 130Bar
Imperial:
• 80cuft tank @ 3000psi / Minimum Deco dive to 60ft
•
•
•
•
Minimum Gas = 800psi
Usable Gas = (Starting Pressure – Minimum Gas) / 2
Usable Gas = (3000psi – 800psi) / 2 = 1100psi
Turn Pressure = 3000psi - 1100psi = 1900psi
These rules should be familiar from previous GUE training and are not modified
when using a DPV. They are the foundation for calculating our gas plan. Once the
gas plan has be completer we can move on to the next step, which is integrating the
DPV into the dive plan.
For each of the gas rules above, we can
determine DPV dependency—can we
safely complete the dive with a complete
failure of a DPV? When making this
decision, two factors to consider are:
1. Whether it is safe and possible
to ascend at any time; and
2.
Must the dive team return to
the starting point?
Any dive where a direct ascent is safe
and possible allows the team to safely
surface with the failure of a DPV; the
all-usable and half-usable gas rules are
both examples of this and are not DPV Figure 2.17: Half available gas plan
dependent.
Gas Management 45
A third-usable dive does not allow a direct ascent and a return to the entry point is
required. In this case, the dive is dependent upon the DPV for a safe exit. Any dive
that is DPV dependent or requires a gas rule of thirds or less is beyond the scope of
the GUE DPV 1 course.
DPV Specific Management
Power Management
Managing the DPV power is as important as gas management when using a DPV
for diving. In order to safely use a DPV, there are three pieces of information that
need to be calculated.
1. Available Burn Time (BT)
2. Reserve Burn Time
3. Required Burn Time
Available Burn Time
As part of the pre-dive logistics for DPV diving, the battery pack for the DPV should
be checked, battery ratings verified, and the batteries burn tested following the procedure in Chapter 1. The result from the burn test provides the Available Burn Time
(BT); this is the maximum time the scooter can be used without damaging the batteries and is similar to the total gas supply available.
Reserve Burn Time
When planning a DPV dive, the amount of available burn time that can be used is
linked to the gas management rules. Even with an all-usable dive, some of the available burn time is reserved for the ascent. The rules for managing available burn time
are as follows.
Non-DPV-Dependent Dives
–– An all-usable dive can be planned with 80 percent of the available burn time
as usable, reserving 20 percent for the ascent.
––
A half-usable dive can be planned with 40 percent of the available burn time
as usable, with 40 percent retained for the return and 20 percent reserved for
the ascent.
DPV-Dependent Dives
–– A third-usable dive would use 30 percent of the available burn time, with the
remaining 70 percent reserved for the return and ascent. This still may not be
enough, and a DPV-dependent dive may require towing reserve DPVs.
46
Chapter 2 Planning and Gas Mangement
Distance
When making reserve-gas or burn-time calculations during the planning of a DPV
dive, the extended distance capability of a DPV must be considered. With a DPV,
divers have the capacity to travel up to 150ft/46m per minute, compared to approximately 50ft/15m for a swimming diver, which means that an efficient diver using a
DPV can go over three times faster than when simply swimming. This must be taken
into account by the dive plan.(See Figure 2.4)
Determining an estimate of the distance travelled using a DPV is more challenging
compared to a swimming estimate, with several factors affecting the efficiency of a
diver using a DPV.
• Environmental conditions
•
•
•
DPV riding technique
Streamlining
DPV speed setting
Speeds when towing a diver or another DPV will vary depending on diver skill and
the environment, but typically remain faster than swimming.
It is important to realize that whether travelling fast or slow, when piloting a DPV,
you will cover a larger distance with little effort, in much less time compared to swimming. Additionally, because you are no longer using as much effort, gas consumption
can be greatly reduced when using a DPV.
250m
820ft
30 Minutes
30 Minutes
500m
1640ft
750m
2460ft
30 Minutes
1000m
3280ft
1250m
4100ft
1500m
4921ft
Figure 2.18: Various distance/speed comparisons
DPV Specific Management 47
DPV failure will challenge usable gas strategies and potentially your gas reserve plan.
It is important to recognize this and include an estimate of the distance travelled
in your dive planning to ensure sufficient gas and burn time reserves are available.
When using a DPV, both gas turn times and burn turn times need to be managed.
The gas turn time is dependent on the minimum gas and the usable gas rule that is
being used for the dive. Gas turn times are affected by gas consumption and decompression.
The burn turn time is dependent on the power management rule used for the dive
and affected by environmental conditions, technique, speed, and streamlining.
DPV Dive Planning Checklist
Putting all the planning tools together, the following checklist can be used when
planning DPV dives.
1. What is Minimum Gas?
2.
3.
4.
What should be the Usable Gas?
What is the Bottom Time estimate?
What should be Usable Power?
5. How far can you travel with Usable Burn Time?
6.
How far can you travel with Outbound Gas?
7. What is the limiting factor for this dive?
8.
What is Turn Pressure?
Using the checklist is a great way to ensure that the correct limiting parameters (gas,
distance, burn time, dive/deco time) have been identified. In Chapter 1 you learned
how to determine DPV burn time. Dive planning is complicated by the fact we have
to match gas usage with DPV power usage as well as maintaining adequate reserves
for both! Runing out of one or the other can have a dramatic impact on both yourself as well as the team.
As an aid to dive planning a DPV Planning Sheet is included in your course package. Once you have determined the basic parameters of your dive fill in the information in the appropriate places and follow through the process until the dive problem
has been solved.
D i ve P a r a mete r s
•
•
•
48
Diving 11L tank @ 200BAR (80ft3 @ 3000PSI)
BT 55 minutes
Minimum decompression dive to 18m (60ft)
Chapter 2 Planning and Gas Mangement
GUE DPV Dive Planning Sheet
1. Minimum gas required for the dive
Avg Depth in ATA
SCR
Time
x
6
30
x
2
# of Divers
2
x
=
Vol
Bar/PSI
720
65
2. Usable Gas
Gas rule (circle one)
SP - MG = UG
-
200
All Available
=
65
135
Useable Gas
135
(SP - MG) / 2 = UG
/2 =
-
Half Available
3. Bottom time estimate
/
1485
/
20
Bottom Time
Depth in ATA
SCR (20L or 0.75ft3/min)
UG in L/ft3
3
24
=
6. Distance traveled with Usable Gas
BT
Speed (50m or 150ft/min)
x
24
4. Usable Burn Time (UBT)
UG Distance
=
50
1200m
Burn test time
x
55
All Usable (80%)
.80 =
Useable Burn
Time
44
44
x .40 =
Half Usable (40%)
5. Distance traveled with Useable Burn Time
UBT
Speed (50m or 150ft/min)
UBT Distance
50
2200m
x
44
=
7. Limiting factor (select the least and check one)
or
Burn Time
Useable Gas
X
8. Turn Pressure
Gas rule
All Available
Starting Pressure
UG
-
135
200
Starting Pressure
Half Available
-
=
65
Turn Pressure
65 bar
Halves Pressure
=
Figure 2.19: DPV dive planning worksheet - Metric all available
DPV Specific Management 49
GUE DPV Dive Planning Sheet
1. Minimum gas required for the dive
Avg Depth in ATA
SCR
Time
x
6
1.0
x
2
# of Divers
2
x
=
Vol
Bar/PSI
24
960
2. Usable Gas
Gas rule (circle one)
SP - MG = UG
-
3000
All Available
=
1000
2000
Useable Gas
2000
(SP - MG) / 2 = UG
/2 =
-
Half Available
3. Bottom time estimate
/
50
/
0.75
Bottom Time
Depth in ATA
SCR (20L or 0.75ft3/min)
UG in L/ft3
3
22
=
6. Distance traveled with Usable Gas
BT
Speed (50m or 150ft/min)
x
22
4. Usable Burn Time (UBT)
UG Distance
=
150
3300ft
Burn test time
55
All Usable (80%)
Half Usable (40%)
x
.80 =
x
.40 =
Useable Burn
Time
44
44
5. Distance traveled with Useable Burn Time
UBT
Speed (50m or 150ft/min)
x
44
=
150
UBT Distance
6600ft
7. Limiting factor (select the least and check one)
Burn Time
or
Useable Gas
X
8. Turn Pressure
Gas rule
Starting Pressure
All Available
3000
-
Starting Pressure
Half Available
-
UG
2000
=
Chapter 2 Planning and Gas Mangement
Turn Pressure
1000 psi
Halves Pressure
=
Figure 2.20: DPV dive planning worksheet - Imperial all available
50
1000
GUE DPV Dive Planning Sheet
1. Minimum gas required for the dive
Avg Depth in ATA
SCR
Time
x
6
30
x
2
# of Divers
2
x
=
Vol
Bar/PSI
600
65
2. Usable Gas
Gas rule (circle one)
SP - MG = UG
=
-
All Available
Useable Gas
65 bar
(SP - MG) / 2 = UG
Half Available
-
200
/2 =
65
67.8
3. Bottom time estimate
/
715
/
20
Bottom Time
Depth in ATA
SCR (20L or 0.75ft3/min)
UG in L/ft3
3
12 min
=
6. Distance traveled with Usable Gas
BT
Speed (50m or 150ft/min)
x
12
4. Usable Burn Time (UBT)
UG Distance
=
50
600m
Burn test time
All Usable (80%)
55
Half Usable (40%)
x
.80 =
x
.40 =
Useable Burn
Time
22 min
22
5. Distance traveled with Useable Burn Time
UBT
Speed (50m or 150ft/min)
UBT Distance
50
1100m
x
22
=
7. Limiting factor (select the least and check one)
Burn Time
or
Useable Gas
X
8. Turn Pressure
Gas rule
Starting Pressure
=
-
All Available
Starting Pressure
Half Available
UG
200
-
Turn Pressure
135 bar
Halves Pressure
65
=
135
Figure 2.21: DPV dive planning worksheet - Mertic half available
DPV Specific Management 51
GUE DPV Dive Planning Sheet
1. Minimum gas required for the dive
Avg Depth in ATA
SCR
Time
x
6
1.0
x
2
# of Divers
2
x
=
Vol
Bar/PSI
24
960
2. Usable Gas
Gas rule (circle one)
SP - MG = UG
=
-
All Available
Useable Gas
1000 psi
(SP - MG) / 2 = UG
Half Available
-
3000
/2 =
1000
1000
3. Bottom time estimate
/
25
/
0.75
Bottom Time
Depth in ATA
SCR (20L or 0.75ft3/min)
UG in L/ft3
3
11 min
=
6. Distance traveled with Usable Gas
BT
Speed (50m or 150ft/min)
x
11
4. Usable Burn Time (UBT)
UG Distance
=
150
1650ft
Burn test time
All Usable (80%)
55
Half Usable (40%)
x
.80 =
x
.40 =
Useable Burn
Time
22 min
22
5. Distance traveled with Useable Burn Time
UBT
Speed (50m or 150ft/min)
UBT Distance
150
3300 ft
x
22
=
7. Limiting factor (select the least and check one)
Burn Time
or
Useable Gas
X
8. Turn Pressure
Gas rule
Starting Pressure
UG
=
-
All Available
Starting Pressure
Half Available
3000
-
2000 psi
Halves Pressure
1000
=
Figure 2.22: DPV dive planning worksheet - Imperial half available
52
Chapter 2 Planning and Gas Mangement
Turn Pressure
2000
The dive planning process for the DPV is an extension of the rules used for non-DPV dives. The strategies used to manage DPV burn time are an extension of those used for gas management and follow a
similar process with all-, half-, and thirds-usable burn rules.
Now with your understanding of the workings and maintenance of a DPV and the tools to start planning dives, it is time to turn to the next chapter and learn the various riding and emergency techniques
covered in the GUE DPV 1 course.
Notes:
DPV Specific Management 53
3
C hapte r
54
Chapter 3 Chapter 3
Operation and Driving Techniques
The Importance of Technique
Cultivating correct technique is not a simple issue when learning how to operate a
DPV. There are a number of variables involved in this process that are not immediately apparent. When you are swimming in the open water with you dive partner(s)
it is moderately easy to maintain situational awareness in reference to yourself, the
team and the environment. Time moves slowly. You have time to expand your awareness outwards. When DPVs are added to the equation, time compresses. The diver is
moving faster, has less time to make decisions, and more importantly the diver has
the tendency to focus inward. This concentration on operating the DPV can have a
very detrimental effect on team cohesion and situational awareness in general. As a
diver gains experience these effects are minimized.
Gaining the necessary experience is an important step. As this portion of the course
is a largely practical exercise, this chapter concentrates on detailing and illustrating
the proper techniques. Your instructor will work with you during the in-water sessions in order that you will know how to practice post-course to improve your techniques. For this introduction to the DPV, the following concepts will be used as the
building blocks to development:
1. DPV positioning
2.
3.
4.
Team positioning
Matching speed
Communication
5. Tow techniques
DPV Positioning
There are three primary positions in which you will place your DPV. These positions are optimized to take advantage of the task at hand. As with any piece of diving equipment DPV use requires careful though, more so in some cases as failure to
adequately control this device can cause you a lot of grief from inadvertent actuation.
This can cause:
• Silt outs in confined areas
•
DPV damage from entanglement with loose gear/lines
DPV Positioning 55
•
Run-a-ways
As a DPV diver your mantra should be always be in control. The three primary positions are:
• Operational position
•
•
Temporary position
Parked position
Operational position
This position is the normal driving position. There is no exactly perfect position for
all divers. It will take some time and effort to find the optimal trim for yourself. The
following general points will aid you in obtaining a good starting position:
• Keep the DPV approximately one arm length ahead (adjust leash length to accomplish the correct length)
•
•
•
You should stay horizontal—flat from chest to knees, feet up, fins horizontal
You must continually monitor buoyancy as is it very easy to use the DPV to
unwittingly compensate for changes in depth
The prop wash should pass just below your right shoulder/armpit
Figure 3.23: Proper trim and driving position
56
Chapter 3 Operation and Driving Techniques
Temporary position
This is the position that a diver uses any time that something must be done that
requires both hands and control of the DPV is still required. A good example of this
is if a diver has to communicate with his team mates via wet notes in a slight current.
Rather than simply drop the DPV below him, it is far more preferable to maintain
control. Ascents, conducting a gas-switch, or when operating in confined conditions
are good examples as well. To stow the DPV do the following:
• Leave the leash attached
•
•
•
•
Pin or lock the trigger (depends on your DPV trigger mechanism)
Set the propeller to zero pitch (if you have a variable pitch DPV)
Push the DPV back between the legs
Keep the DPV in place by applying pressure with your knees
Figure 3.24: DPV in the temporary stowed position
Parked position
The parked position is one that is used when the diver is either finished using it
either for the time being or completely. It is a stream-lined position that allows the
diver complete freedom of movement. When stowed properly the DPV sits nose first
directly behind divers tanks. This position is used for towing a broken DPV, during
DPV Positioning 57
gas-sharing or towing a reserve DPV. The following process should be followed to
stow the DPV:
• Lock or pin the trigger (depends on your DPV trigger mechanism)
•
•
•
•
•
Set the propeller to zero pitch (if you have a variable pitch DPV)
Unclip the DPV and stow the leash
Unclip the tow cord and clip it to the front crotch ‘D’ ring
Push the DPV back between your legs as depicted in Figure 3.3
Dead DPV, gas-sharing or reserve DPV
Figure 3.25: DPV in the parked position
Team Positioning
In order to facilitate team cohesion as well as communication, we must be able to
adapt our team formations to different environments and dynamic conditions. As
mentioned earlier in this chapter, one of the major benefits of using a DPV which is
additional speed can be a potential pitfall as well. The problem with additional speed
is that team separation is possible if the team is not vigilant. When swimming it is
much more difficult to lose your team. When moving along at a high rate of speed a
moment inattention in moderate or poor visibility can cause separation issues.
There is no absolutely right position to be in as team formation is largely dependent
on the environment. Specifically in the open water position is largely dependant on
58
Chapter 3 Operation and Driving Techniques
visibility. Although there are many variations of positions that are possible, the following three are the primary ones:
• Line formation
•
•
Wing formation
Tow formation
Line formation
The line formation is not frequently employed during open water operations due to the
potential of straining the ease of communication. However in situations such as navigating a wall, travelling along side a wreck, or during conditions of reduced visibility
it will prove useful. The following should be noted when employing this formation:
• The team leader should be the lead diver
•
•
•
As communication crucial the diver number two has to be especially vigilant
to keep the team together
Depending on visibility proximity is crucial as it is very easy to encounter conditions in which the last diver may not be able to see the lead diver
Divers should be slightly off-set either horizontally or vertically to keep their
DPV out of the prop was of the DPV in front of them
Figure 3.26: Three man team in line position
Wing formation
The wing position is the most commonly used formation when travelling with a
DPV in open water with either two or three man team. In a two man team the divers should be just side by side with the leader on either side they feel comfortable
with. Which ever side the leader chooses this should remain consistent throughout
the dive in order that each diver knows which direction that help would be available should it become necessary to need it. The following points should be adhered
to when travelling in a wing formation:
• The team leader takes the center position in a three man team
•
•
It is the responsibility for the two wing men maintain the same depth as the
leader and stay forward enough laterally to stay in the leader’s vision
Diver proximity can vary according to the environmental conditions
Team Positioning 59
Figure 3.27: Three man team in wing formation
Tow formation
The last formation is the most difficult one to execute. In an open water environment rarely should the team be in a position where it is absolutely necessary to have
to employ this formation for an extended period of time, as a direct ascent should be
a viable option. This should be practiced however as it always preferable to return or
get to your point of exit whenever possible.
What makes this formation difficult is that the lead (towing) diver has to be aware
that he is in fact responsible for the diver being towed. He has to makes occasional
stops for buoyancy checks as well as allowing the for the towed diver to adjust his
or her position if required. Follow these steps to position and tow a diver that has a
non-serviceable DPV:
• The diver with the broken DPV signals the team and stows the DPV in the
parked position as outlined previously
•
•
•
60
The diver to be towed then maneuvers between the legs of the lead diver; with
his right hand grasp the crotch strap; and with the left arm grasps the left leg
Both divers do a buoyancy check and adjust if necessary
The lead diver signals the third team member (if there is one) and they move
off
Chapter 3 Operation and Driving Techniques
Figure 3.28: Diver with a broken DPV being towed
If this is a three person team the diver not involved in the tow has considerable leeway
as to where to position them self in an open water as the environment will usually
allow for flexibility. Allowing for good visibility the attending diver should allows
attempt to select a position that allows them to observe and provide aid as required.
The optimum position is usually slightly behind the lead diver and to the right of
the diver being towed.
Matching Speed
Establishing a comfortable and consistent speed among the team is important as it
is necessary for good team cohesion and communication. This process takes a few
minutes at the beginning of the dive and is never exactly the same for every dive.
Factors that affect matching speeds are:
• DPV types
•
•
•
•
Battery charge
Trim
Drag caused by extra equipment(or the lack thereof)
Environmental factors such as current/visibility
The process for matching speeds is as follows:
• The team forms up facing each other and prepares their DPVs for use
•
•
•
•
All members set the propeller(variable pitch units) or the speed controller(fixed
pitch units) for mid-range operation
The team leader signals and leads off in the chosen formation
All other team members set their speed according to the leader.
The team lead does not vary speed unless environmental conditions dictate
such as an increase in current
Matching Speed 61
•
•
The team leader monitors the team to ensure that a speed has been chosen that
all members can match
Once all team members have matched speed and are comfortable normal dive
protocols and communications procedures take over
Communication
It has been discussed earlier in this study guide the difficulty of communication while
using a DPV. The primary issue is the reduction of external awareness as divers are
in general more focussed on where they are going. This tendency to focus inward
occasionally makes it difficult to gain a divers attention. Depending on the formation this may or may not be an issue but be aware that it can be problematic. For
example a wing formation is less of a problem than divers travelling in line. Passive
light communication in particular, is vital to avoid team separation
Light communication
•
•
•
Point over the divers left shoulder and attempt to illuminate an area in front or
of below and in front of the diver to let them know passively that you are still
in position
Rapid light movement in this divers field of vision will alert them to any
problems
In wing formation direct the light at the DPV tube
Communication protocol
•
•
•
62
Everyone is responsible for maintaining communication
Diver two in a three man team is responsible for distributing signals (keeping
the team intact)
As soon as a communication breakdown occurs the team must stop and immediately engage in what ever protocol is necessary to re-establish contact with
the team
Chapter 3 Operation and Driving Techniques
Emergency Procedures
The following emergency will be discussed and practiced during your DPV level 1
course:
• Run-away DPV
•
•
•
•
•
Broken Trigger
Damaged or broken DPV
Flooded DPV
Gas sharing
Limited visibility
It has to be stressed that it is not nearly enough to be exposed
to these procedures while on course. The list of emergencies
above are not theoretical or ‘might occur’ emergencies. If you
pilot a DPV long enough it is not a question of ‘if ’ they will
occur as eventually all of these will occur. Divers must ensure
that they practice the solutions to these problems—the greatest
danger is this area is one of complacency. As with any other
facet of GUE training, a comprehensive DPV practice regimen is strongly encouraged.
A T o ugh Q ue s t i o n
At the end of the day you have to remember
that a DPV, while a nice toy, is just a piece of
equipment. These devices represent a major
monetary investment and when faced with
an emergency situation they have a tendency
to focus on this and are understandably
reluctant to face the possibility that it may
be necessary to discard the DPV in order to
extricate themselves from potentially life
threatening situation. You may be in the
unenviable position to have to ask yourself
the question how much is you life worth and
be prepared to discard your DPV before you
enter the water.
Dealing With Emergencies
The best way to deal with emergencies is to reduce the possibility of encountering
a problem in the first place. The best defence against this likelihood is to have solid
dive plan that considers a multitude of complex variables such as:
• Discuss team strategies and procedures
•
•
•
•
•
Set reasonable dive goals and objectives
Plan logistics and responsibilities
Set the dive parameters
Set the dive profiles
Discuss the risks and contingencies
The primary method of avoiding problems is to ensure that the skill and experience
of the divers match each other and the environment. Teams frequently run into problems when they exposure themselves to dive profiles or environments that are much
more challenging than their general level of skill would allow. For example a dive in
which the team may be challenged yet capable of doing while swimming, may be a
dangerous proposition with the exposure that a DPV will bring to the dive. Be cautious as you and your team expand your experience base with DPVs.
Emergency Procedures 63
Run-away DPV
A run-away DPV can potentially create less desirable situations that range from siltouts, team separations, loss of buoyancy, and personal injury. The greatest danger
that occurs with a run-away is that it is usually completely unexpected. The diver is
cruising along and expects to stop when he removes his finger from the trigger and
does not. This requires immediate action on the part of the diver as if it is not handled
correctly and quickly it can rapidly spiral dangerously out of control.
The likely causes of a run-away DPV are:
• A jammed trigger
•
•
A damaged relay
A damaged speed controller
Problem resolution:
1. Signal the team
2.
3.
4.
Toggle(or twist depending on the DPV type) the trigger several times
Manually move the magnet from the reed switch(for a Gavin or Gavin type
DPV) or engage the battery cut off switch if the model is so equipped.
Stop the propeller with your hand, reset to zero(if the DPV has a variable
pitch propeller)
5. If possible take the lead and run the DPV back to the exit point
6.
If it is not possible to make it to the exit, then ascend, shoot the DPV up to
the surface, or leave the DPV
NOTE: A run away DPV should never be towed!
Broken Trigger
Most times a broken trigger does not render the DPV unusable as most designs allow
for problem resolution when face with this problem.
The likely causes of a broken trigger are:
• The trigger wheel has become misaligned
•
The trigger wire has broken
Problem resolution:
1. Signal team
2.
64
Manually move the magnet to engage the reed switch(for a Gavin or Gavin
type DPV) or engage the battery cut off switch if the model is so equipped.
Chapter 3 Operation and Driving Techniques
Damaged or broken DPV
A non-operational DPV leaves the team with several options depending on the situation.
Likely causes:
• Loss of power, the battery is dead
•
Reed switch, connector failure, or speed controller failure
Problem resolution
1. Signal the team
2.
3.
Park the DPV between the legs
Ascend, tow, shoot up, or leave the DPV
Flooded DPV
Most DPV flooding happens close to or at the surface. As pressure(depth) increases
the body O-rings are compressed hence sealing the body. At depth the most likely
problem would be a shaft seal. If you have a DPV with a sealed motor compartment
this can reduce the potential damage.
The likely causes for a flooded DPV are:
• Latches coming undone
•
O-ring failure
Problem resolution:
1. Signal the team
2.
3.
Abort dive if possible as the DPV will become extremely negative
L i ft D ev i ce s
When using a DPV divers should ensure that
they carry a lift device that has the capacity
to lift a flooded DPV. A flooded DPV will
weigh approximately the same as it does on
shore. Weigh your DPV to ensure that your lift
device is capable of lifting your DPV. Some
units can weigh in excess of 100lbs/45kg!
Ascend, tow, shoot up or leave the DPV
Gas Sharing
Gas sharing while using DPV has the same basics as any out of gas situation(OOG).
The key as usual is stay calm and remove the DPV(s) from the equation as quickly as
possible and then proceed as if it is a normal OOG scenario.
Problem resolution:
1. Signal the team
2.
3.
4.
Approach the donor
Execute the gas sharing drill
Pause to make sure everyone is OK
Emergency Procedures 65
5. As soon as practical decide exit strategy. In the open water the response should
be park the DPVs and ascend immediately!
Limited Visibility
Weak DPV skills will most likely reduce visibility quickly if diving in an sensitive
environment. Even if the skills are good limited silt-outs are possible.
The likely causes for reduced visibility are:
• Weak DPV skills
•
•
•
Thrust directed downwards
Environmental changes
Other divers with poor personal skills
Problem resolution:
1. Signal the team and slow down
2.
3.
4.
Convoy – DPV on fins creating ”a single unit”. Last man drives the ”unit”
forward
If line following, hold line with left hand and the DPV to the right, bump
and go
In the open water it is occasionally possible to rise above areas of localized
reduced visibility. Communication is paramount in order that no team members are left behind.
5. If there is current or water flow of any sort it may be desirable to wait it out if
time allows. It should be obvious if using this strategy ‘going with the flow’
will keep the team enclosed in silt or debris.
Conclusion
During this course you have gained a basic knowlege of the operational and maintence of a DPV. While there are differences in the mechnical aspects of rh DPVs
that are produces from various manufactures, the operating principles are basically
the same. Use this knowlege as the basis to go forward and gain the one thing that
there is not nearly enough time during the DPV Level 1 course to provide, that is
experience. Be cautious in your explorations and reguard a DPV for what it is—a very
enjoyable tool that can cause you no end of grief it you do not treat it with respect!
We trust that you will enjoy this course and look forward to have the opportunity to
return for move advanced training on your DPV Level 2 course. Have fun!
66
Chapter 3 Operation and Driving Techniques
Notes:
Conclusion 67
GUE Diver Propulsion vehicle level 1
Global Underwater Explorers, 15 South Main Street, High Springs, FL 32643, USA, (386) 454-0820, [email protected]