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Reasoning for Deco/Stage Bottles on Left

For the past few days, I’ve been creating the training materials for the new UTD Stage/Deco Bottle Mini.  One of the things I tried to accomplish is explaining the “why” and not just the “how”, so I thought I’d take some time to offer some insight into the “why” we wear our stages and deco bottles as we do….on the left.

Before getting into that, I’d like to stress that there are many different schools of thought on how the stages and deco bottles should be worn.  This is not an argument against other methods, but merely an explanation of UTD’s methodology.  One aspect of diving is personal choice, and my intent with this blog is merely to provide the diver with more information, so they can make a more informed choice, whatever method they choose.

It’s also important to remember that a primary aspect of the UTD mindset is consistency.  This includes consistency in equipment, training, protocols and team.  As mentioned above, the UTD equipment configuration places all stage and deco bottles on the left side of the diver.  I’ve listed the reasons why below:

1. Allows for clean longhose deployment – With the stage/deco bottle on the left side, there is no possibility of the bottle “trapping” the longhose, which is routed on the right side
2. Ease of scootering – the dpv (diver propulsion vehicle, or scooter) is typically operated with the right hand.  Having the right side clear of bottles allows for more freedom of movement of the right arm to control the dpv/scooter.
3. Clutter of the right chest D-ring – The right chest D-ring has many items clipped off to it.  It’s where the longhose is clipped off when not in use, a backup light, an extra double ender and the scooter when stowed
4. No right hip D-ring – In the UTD gear configuration, there is no right hip D-ring, as that is where the light canister is.  Consequently, there is no hip D-ring to clip a bottle to
5. Allows for one handed stage/deco valve management – With the bottles on the left, facing “up”, the handwheel is on the left, or “outside”, making it very easy to access with the left hand
6. Clean and consistent hose routing – All regulator hoses come from the left, behind the diver’s neck, and in to the mouth from the right
7. Clean donation of reg in diver’s mouth with right hand – Due to point #6, the regulator is always donated with the right hand, since the hose routing is always the same
8. Easy access to right (utility) pocket – This is a common misconception.  This isn’t about how quickly the diver can get to their pocket in an emergency.  The right pocket is the utility pocket.  In other words, the items in the right pocket may be used throughout the dive.  This means that these items may not only be taken out of the pocket, but also may be put back.  Ease of access to this pocket, since it will be used numerous times throughout the dive, is important.
9. Consistent gas switching and stowing procedures – With all bottles on the same side, the gas switch and stow procedures are always the same.
10. Consistent stage/deco bottle rigging – Since the bottles are always on the diver’s left, all bottles are rigged the same way.
11. Clean canister light cord routing – Since the canister light is on the right, and the bottles are worn left, there’s no issue of the light cord getting tangled or “trapped”
12. No risk of light switch getting bumped off – Like #11, since the canister is on the right and the bottles are on the left, there is no risk of a deco bottle hitting the light switch and accidentally turning off a functioning light
13. The scooter is stowed on the right side when not in use

Of course, some items listed above are more “critical” than others.  Should a bottle be rigged for the left side, then mistakenly be put on the right when gearing up, it would be an inconvenience when doing the gas switch, due to the hose being on the inside instead of the outside, but probably not a life threatening situation.  Whereas, inability to donate the longhose, or tangled hoses due to unclean routing can cause for a bad situation.  Since UTD is based on consistency, the above reasons are why we wear the bottles left.

This affects consistency in equipment, of course, protocols (gas switching, stowing, donation of the reg in the donor’s mouth with the right hand, etc), training (the diver is trained to always have the stages and/or deco bottles on left.  There is no “in this circumstance, the bottle goes on left, and in this circumstance, it goes on right…” or “Donate using left hand in this case and donating using right hand in this case…”) and team, since all members of the team carry their bottles the same way.

There are certainly other configurations, and every diver must choose which method best works for them.  This is simply the reasoning behind why the UTD equipment configuration has the stages on the left.

Misconceptions of UTD Essentials & Intro to Tech

Between the misinformation we’ve seen and heard, and some of the questions we’ve been asked, I thought I’d provide some insight into the UTD Essentials, Intro to Tech, Rec 2 and the general UTD teaching philosophy overall.

While the “T” in UTD does stand for “Team”, it’s important to remember that we believe a diver must have solid foundational and personal skills before moving on to team skills.  In other words, if a student can’t perform a modified s-drill (personal skill) without losing their trim or buoyancy (foundational skills), how will they be able to perform a full s-drill with a teammate?   While the “team” aspect is a critical aspect to the UTD approach, that is just one block in the overall structure, and the top block is only as solid as the blocks below supporting it.

This is where some misinformation and inaccurate comparisons exist with the Essentials class.  Essentials is exactly as its name implies.  It teaches the essential skills of safe diving.  It is, by design, a personal skills class, not a team skills class.  We focus on the foundational skills of buoyancy, trim, kicks and balance.  We then move to the personal skills of the Basic 6 and smb deployment.  Team skills are introduced and performed, but again, the focus of this class is to develop the skills needed to become a safer diver and, in turn, a better teammate.

For the reasons stated above, Essentials is a very common entry point into the UTD curriculum.  While divers at any level, including instructors, photographers and experienced divers will benefit from the class, it’s designed to provide a diver who has taken their open water class from outside the UTD curriculum a means of learning the skills required for future UTD classes.

In other words, most open water students wanting to take Rec 2, which is the “equivalent” of Advanced and Nitrox combined, and also where team skills and light critical skills (failures) are introduced would very quickly be overwhelmed, simply because they haven’t built the foundation needed for that class.  They wouldn’t learn anything from the class because they’d be in over their head from the very beginning.

This isn’t to say that every diver wanting to enter the UTD Recreational curriculum must first take Essentials, as we do accept equivalents.  However, Essentials was designed to teach the foundational and personal skills, and introduce team skills, in a non-evaluation environment where the student can focus simply on learning, and not the pressure of passing or failing.

Additionally, there are also only 2 gear requirements for the Essentials class…a 7′ long hose and blade style, non-split fins.  It was important to us to make this class accessible to anyone wanting to take it, without a large investment in gear and equipment.

The UTD Intro to Tech class, while similar to the Essentials class in several ways, does differ in that it is an evaluation class. Intro to Tech is a more robust course, where the student is learning the skills needed to enter the UTD Technical Diving curriculum, in a non-critical skills (failure) environment.  To enter the Tech 1 class, where the student will be entering mandatory decompression obligations, the student must first meet the standards of the Intro to Tech class.  To that end, the Intro to Tech class is an evaluation class, but the student is still learning the required foundational, personal and team skills required to build that foundation needed for more advanced technical diving.

The Intro to Tech class is taken in double cylinders and a decompression bottle.  We feel that teaching the mechanics of gas switches, stowing and bottle passing in a non-critical skills environment allows the student to learn properly the first time and also allows them time to go practice their new skills before entering the Tech 1 curriculum, where failures are introduced.

Upon entering the Rec 2 (after Essentials) or Tech 1 (after Intro to Tech), the focus shifts to team, awareness, problem solving and thinking.  This is because they now have the foundation built, and they can refocus their new extra bandwidth towards those areas, as it is no longer needed for their own skills.

It should be noted that this method is not the only dive instruction philosophy.  It’s simply UTD’s training approach.

Hopefully this clears up some of the confusion.

Brian

Rock Bottom for Recreational Dives

Overview

Proper gas planning & management is critical to safe diving since humans cannot breathe underwater without life support equipment.

Unfortunately, many divers don’t understand what gas planning & management is, and simply use the standard “Back on the boat with 500psi” or the rule of “thirds”.  While those types of plans may work in certain circumstances, they can also be very dangerous, since, in the first example, the diver is planning his gas so he arrives at the surface with a set pressure in his tank.  He’s not planning his gas for what would be needed should an emergency occur underwater, which could be the difference between life and death.

It’s important to remember that an Out Of Gas (OOG) emergency is unacceptable.  Proper gas management and gear maintenance is all that is required to avoid this type of situation.  However, when planning our dive, we plan according to worst case scenarios.

What is Rock Bottom

Rock Bottom is, quite simply, planning for the worst case scenario…the instance where a diver in a 2 person buddy team experiences a catastrophic and complete loss of gas at the deepest part of the dive.  It’s the minimum amount of gas needed for 2 divers to ascend, completing all required stops, sharing air on a single cylinder.

Review

In your open water class you learned about Boyles Law.  Simply put, Boyle’s Law states that at a given temperature as pressure increases, volume decreases. 

In salt water, every 33’ is an atmosphere.  At the surface, we are under 1 ata (atmosphere absolute) of pressure.  Therefore, at 33’, we’re under 2 ata’s of pressure (the single atmosphere at the surface, and the 33’ of water above us).  At 66’, we’re under 3 ata’s of pressure.  99’ is 4 ata’s, and so on.

Since every 33’ of saltwater is an atmosphere, to determine the pressure, in ata’s, of any given depth, we simply divide the depth by 33, and add 1 (for the pressure at the surface).  In other words;

Ata = Depth / 33 + 1

Likewise, to determine the depth of any given pressure, we simply subtract 1 (for the pressure at the surface) from the pressure, then multiply by 33.  Also shown as;

Depth = ata – 1 x 33

Consumption

It’s important that every diver know his/her own consumption rate.  If you don’t know your consumption rate, and would like to learn more, please Contact Us to schedule a FREE Gas Planning & Management Workshop.

At the recreational level, we typically plan for a stressed diver to breathe approximately 1cuft per minute (Respiratory Minute Volume, or RMV), at the surface.  Applying Boyle’s Law, from above, if a diver breathes approximately 1cuft per minute at the surface, stressed or working, he’ll breathe 3 cuft per minute at 66’, due to the fact that your 2nd stage regulator must deliver air to you at slightly above the ambient pressure;

1 (RMV) x 3 (ata of 66’) = 3

At 99’ the diver will breathe 4 cuft of gas, when stressed or working;

1 (RMV) x 4 (ata of 99’) = 4

You can certainly increase your planned stressed RMV upwards, for conservatism, if desired or if you know your working RMV to be higher than 1.

Calculating Recreational Rock Bottom

When calculating Rock Bottom, there are certain rules and assumptions that we must apply and consider;

 

• Use working RMV (1.0 each if not known, as previously stated)
• :01 to donate the regulator, assess the situation and initiate the ascent
• Ascend at 30fpm to first stop (50%)
• Ascend at 10fpm from 50% to surface

One final rule; never use a Rock Bottom of below 500psi.  If your calculated Rock Bottom is below 500psi, use 500psi.  This is due to the inaccuracy of the spg when reading pressures below 500psi.

When applying the rules and assumptions above, its easiest to visualize the situation in 2 segments; the bottom segment (donation, assessment and initiation of ascent) and the ascent.

Additionally, there are only 3 pieces of information needed to calculate Rock Bottom;

• How deep (depth)
• How long (time)
• Breathing rate (combined RMV for TWO divers, since they will be breathing off a single tank)

Depth and time are both variable.  The deeper the dive, the more that is needed/used in the bottom segment, due to the increased depth.  Likewise, the deeper the dive, the longer the ascent time.

Here’s an example;

 

So, in the example above, a buddy team experiencing an OOG emergency at 100’ will need 40cuft of gas to ascend safely, completing all stops.

However, since we work with pressure, and not volume, while underwater, we must convert the volume (40cuft) to pressure, or psi.

To do that, we’ll simply run a quick calculation using tank factors

Tank Factors

Tank factors are simply the amount of cubic feet per 100 psi, for a given tank.  Using tank factors is a very easy way of converting between volume (cuft) and pressure (psi).

To calculate a tank’s tank factor, you simply divide the tank’s rated pressure by the tank’s rated volume, then multiply by 100;

Tank Factor = rated volume / rated pressure x 100

For an al80 (al80’s actually contain 77cuft, not 80), the tank factor would be:

77 / 3000 x 100 = 2.66

This means on an al80, there are 2.66 cuft per 100psi.

To make life simple, we’ll just call it a tank factor of 2.5.

It’s important to remember that you must use the rated pressure and volume.

Now that we know the tank factor of an aluminum 80, we can convert the volume (40cuft) to psi in the above example, using a simple formula.  The diagram below is actually a formula in itself.  If you want to know the volume, you’d simply multiply pressure by the tank factor.  If you want to know the pressure (psi), you’d simply divide the volume by the tank factor.

So, using the formula above, to determine how many psi 40cuft of gas in an al80 is, we simply divide the volume (40) by the tank factor (2.5);

40 / 2.5 = 16 or 1600

Applying this to the above example of a Rock Bottom Ascent, we’d get this:

 

1600psi is needed for the 2 divers to ascend from 100’, sharing air on a single al80, completing all required stops.  Since this is based on assumptions, if you’d like to add a buffer of 200 or 300psi, making the Rock Bottom 1800 or 1900, that is perfectly acceptable.  However, you should never lower the Rock Bottom number.

There are other gas plans as well, as Rock Bottom doesn’t work in every scenario (overheads, such as caves or wrecks, where additional gas is needed to get to the ascent point).  But for most everyday recreational dives, Rock Bottom gives you the knowledge that you need to safely execute a dive.

It’s important to understand that Rock Bottom is for a specific depth, and not a specific dive.  In other words, 100’ has a different Rock Bottom than 90’.  For instance, if you hit your Rock Bottom at 100’, and ascend up to 80’, you must ensure that you don’t exceed your Rock Bottom for 80’.

It’s a good idea to make note of your Rock Bottom in 10’ increments, from 60’ to the maximum depth you dive to.  An easy way of doing this is to keep them in your wetnotes.  If you know the volume, you need only use the tank factor to adjust it for the tank you are using.

If you’re interested in learning more about Gas Planning & Management, please Contact Us to schedule a free Gas Planning & Management Workshop.

UTD Standard Mixes

To keep our dives consistent, flexible and as simple as possible, we use standardized mixes.  Each mix allows us a range of depths to explore and provides a similar decompression.  This eliminates the need to remember a bunch of numbers and the use of decompression tables, since the ascent profiles are consistent within the mixes.  In other words, a dive to 150′ using 21/35 will have a similar ascent profile as a dive to 200′ on 18/45.  The primary difference is we’d simply add a 2nd decompression gas (O2) on the 200′ dive.

Parameters

• Bottom mixes have an MOD PPO2 of 1.4 ata
• Bottom mixes have an average PPO2 of 1.2 ata for our working depth
• Bottom mixes have a buffer from our working depth and the MOD of 1.4
• Bottom mixes are created by adding HE, then topping with 32% (easy for banking 32% and doing trimix fills) or by quick formulas for “air tops”
• Deco mixes have an MOD PPO2 of 1.6 ata
• Deco mixes have an average PPO2 of 1.2 ata (averaged over the range the deco mixed is used), except for O2 at 20′
• Deco mixes are used over an average of 5 10′ stops, except for when using O2 for decompression
• The higher the HE content, the better, however the HE content must always be enough to provide an END of 100′ or less, based on the conservative formula; END = (1 – HE)*ATA’s.  This formula assumes O2 to be narcotic

 

 

Bottom Mix	Depth Range	MOD	END at Max Depth	EAD	”Air Top” Mixing
EAN32	0 – 100′	111′	-	20% credit	14% O2
25/25	100′ – 130′	151′	88′	10% credit	12% O2 – 25% HE
21/35	130′ – 160′	190′	98′	0%	9% O2 – 35% HE
18/45	170′ – 200′	220′	94′	0%	8% O2 – 45% HE
15/55	210′ – 240′	275′	90′	0%	7% O2 – 55% HE
12/60	250′ – 300′	352′	100′	0%	5% O2 – 60% HE
10/70	310′ – 360′	429′	88′	0%	4% O2 – 70% HE
Deco Mix	Depth Range	MOD	END at Max Depth	EAD	“Air Top” Mixing
O2	20′	20′	-	-	O2
EAN50	70′ – 30′	70′	-	-	36% O2
35/25	120′ – 80′	120′	-	-	25% O2 – 25% HE
21/35	190′ – 130′	190′	-	-	9% O2 – 35% HE

Practical Application of Ratio Deco

I’d like to take a few moments to illustrate how standard gases and ratio deco have effected my diving recently.

I posted a trip report of our attempt to dive the SS Governor here.

Here, I’d like to talk about the flexibility the UTD standard gases and decompression strategies. Keep in mind that ratio deco isn’t a decompression theory, it’s simply a strategy using existing models and research to help shape an ascent profile.

On our attempt on the Governor, we used 15/55 for backgas and EAN50 and O2 for deco. This allowed us a range of depths, generally in the 200’ to 240’ range. That afforded quite a bit of flexibility to explore the wreck, which was especially useful in this case as the wreck is sitting upright where the mudline is at 240’ and the deck is at ~ 200’…quite a variance in depths.

Our plan, however, was to try to keep max depth at 230’, and spend most of our time on the deck at 200’ to keep our average depth at 220’ or shallower, to keep our deco time manageable.

Unfortunately, due to vessel traffic delaying our splash time, we weren’t able to do the Governor. We instead decided to do the Al-Ind-Esk-A-Sea, another large wreck that sank in 1982 after a fire broke out and numerous explosions occurred. Dan Warter has a great article on the Al on his website, DCS Films.

Though the profile of the “Al” is similar to the profile of the Governor, it really made me think about what would happen if we were to do another wreck with a completely different profile. In other words, what if we planned to do a wreck that was 240’, but due to conditions, we were forced to do a dive in 200’?

Well, for starters, we’d have to make sure our backgas was compatible with the profile of that dive. We had 15/55 in our tanks, which would allow us to go as deep as 240’, and would certainly work for 200’. Now that we know our backgas is ok, we need to figure out our decompression. There’s quite a difference in the deco obligation/profile for a 240’ dive and a 200’ dive. If we simply used the same profile for the 200’ dive as we do for the 240’ dive, our first stop will be much deeper than necessary and our deco time will be much longer than necessary. We could bring out the laptop if we brought it and cut new tables, but we’d also have to print them and laminate them. We could just run our computers as well, which is fine, but if everyone has different computers running different algorithms, that can create some confusion as well.

This is what I like about Ratio Deco…”deco on the fly”, or “tailgate deco” as I sometimes call it, allows me to calculate an entirely new deco schedule in 2 minutes time on scratch paper. Instead of hurrying to pump out a new set of tables, or doing much more deco than necessary because I don’t have any other tables than the ones I made for the original profile, I just grab a pen, a napkin, scroll out my new schedule as a general plan, then relax and prepare mentally for the dive.

How can I do this? Standard gases all have the same deco shape. Sure, we may add extra deco gases, but the shape is the same. No new numbers to remember, no tables to cut every dive. The shape is always the same whether its an mdl dive, Tech 1 dive, Tech 2 dive or a Trimix dive. This makes it very easy to remember and calculate.

How about the reverse? Had we a chosen a mix specific to the depth we planned to go to (or “best mix”), rather than a range and ended up going to a wreck deeper than the one we had originally planned, we wouldn’t be diving at all that day. All that time and effort preparing, the cost of the charter and the gas, and we can’t even dive!

While there’s more benefits to standard gases and ratio deco, these are 2 that I really appreciate and have really positively effected my diving. They allow me to actually explore. We can do our dive, with plenty of flexibility to adjust our profile as needed, then, when our dive is over, we can figure out our deco.

On our dive on the Al-Ind-Esk-A-Sea, we had no tables or deco schedules…nothing written on a wrist slate or in our wetnotes. We did our dive…then, when our dive was done and we were ready to ascend, we figured out our deco. One quick signal of “average depth, 210’” and we both knew what the rest of our profile would look like.

The next 65 minutes we spent decompressing, both of us knowing what the rest of the ascent would look like.