Practical Application of Ratio Deco

This is a great article giving an example of how ratio deco can be used on any dive. This was written by Brian Wiederspan. Many people either fear ratio deco or completely embrace it. The thing to remember is when using ratio deco and standard gases, the deco curve always looks the same. Therefore, it is much easier to determine “deco on the fly”. I hope you enjoy it.

Dive Safe,
Duane Johnson
Precision Diving

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

Here, I’d like to talk about the flexibility the 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 SS 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.

Best Practices in Scuba Diving

By Duane Johnson | Training

Ever hear the saying “There’s more than one way to skin a cat.”? Basically what it is saying is that there are multiple ways of doing the same thing. In scuba diving, there is a multitude of methods, procedures, etc for diving. But what is the best one? This article will look at a few areas of recreational scuba diving and describe what are the best practices for those areas and why.

Propulsion
Do you remember when you did your initial open water course? Did the course materials or instructor discuss propulsion techniques? Most likely not. Most open water courses do not teach propulsion techniques as they assume the students are swimmers. When swimming on the surface, most people use a kick called the flutter kick. Most open water classes will just have you flutter kick around the pool or open water as that is what you probably learned when you were a kid in swimming lessons.

The flutter kick is the most inefficient propulsion technique in scuba diving. The traditional flutter kick uses the largest muscles in the body, the thighs. When you exercise, your muscles metabolize oxygen and the by-product of this is carbon dioxide (CO2). CO2 is a killer in scuba diving. It is more narcotic than nitrogen and can lead to a diver blacking out. So when you are swimming with the flutter kick and working underwater, you are building up CO2 in your body. Secondly, the flutter kick directs water down. If you are diving in sensitive areas such as a reef or shipwreck, you run the risk of damaging that environment or silting it out. A silt out can also be a killer in scuba diving.

The best practice for propulsion techniques is the frog kick. The frog kick directs water straight back from the diver. It does not direct water downward, instead it directs water directly behind the diver. Thus significantly reducing the risk of damaging sensitive aquatic environments and silting out confined areas such as shipwrecks. The frog kick also does not use the thigh muscles as much as the flutter kick. By using more of the glutes, hamstrings, and a little thigh, we can reduce how much CO2 we are building up in our bodies.

Equipment
Currently, the trend in scuba equipment is that people use a jacket style buoyancy control device (BCD). These BCDs fit people like a vest. They have a variety of features. Many include weight integrated, built in tank bands, and pockets. They also use plastic buckles and velcro to secure around the diver’s body. One big problem with jacket style BCDs is that they are very bulky. The weight pouches on these types of BCDs are normally right around the “love handle” area of the body. This now moves the weight off our back and possible off our center of gravity.

The best practice for a BCD is the backplate system with a one piece, continuous harness. This configuration is very streamlined and not bulky. Backplates are made of either stainless steel (SS) or aluminum (AL). The SS backplate is 6 pounds negative, that means you can take six pounds off your weight belt. The AL backplate is 2 pounds negative. Many divers have found that carrying weights in pockets or on a weight belt is not comfortable. The backplate puts the weight on the divers back where it can be supported easier than hanging off the hips. The one piece continuous harness, not only is streamlined, but it also eliminates many failure points. By getting rid of plastic buckles and velcro, the one piece harness will be much secure. If a diver also out grows the harness or needs to replace it, the webbing only costs about $15 and can be purchased at any hobby store. Jacket style BCDs, when out grown, must be replaced and can be very expensive. The backplate system can also be paired up with a wide range of wings (i.e. the air cell or BCD). If a diver is going to move between a single tank rig and double tanks, the backplate doesn’t need to change. You just swap out the wing for which type of rig you want to dive.

There are many other best practices when it comes to equipment. To many to list out here. But you should get my point. We are looking for equipment that enhances our skills, not replacing them. Equipment should also restrict potential failure points, either real or perceived.

Trim
First, let’s look at trim. Trim is the position a diver is in. In order to move horizontally, with little resistance, through the water, we must present the smallest footprint as possible. Just like with cars being aerodynamic, we must be just as aerodynamic. The most ideal position is to be completely horizontal in the water. This gives us a small footprint and reduces drag as we move. Now, when we move up in the water column, you were probably shown to be in a vertical position, rotating around, looking up so you don’t run into the bottom of the boat. Well, remember when I mentioned that when we present a small footprint, we move very efficient through the water. When ascending, we want to ascend at a very slow pace. If we are streamlined going up, it just makes it easier to ascent faster than what we want. In order to ascend in a controlled manner, we must present as much drag as possible going up. This means we must remain in a horizontal position when ascending. This creates a large surface area to increase drag. Thus allowing us to control our ascent. The best practice for measuring trim, is that a diver should be no more than 30 degrees of horizontal. For technical divers, that measurement is 20 degrees or less.

Moving Forward
As you can see, I just touched on a couple areas where we can apply best practices. There are many other areas and I will write about those in future articles. So when you are taking your next class and are told/shown multiple ways of doing them, ask which one is the best and why.

If you found this article helpful, please leave a comment or submit a Digg for it. As always, I welcome your questions and comments.

Dive Safe,
Duane Johnson
Precision Diving

NOTES FROM A RECREATIONAL DIVER – Workout Dives

By Jim Costopulos | Training

On the last day of a GUE Fundamentals course I completed several years ago, I caught up with one of the two instructors in the parking lot as we were packing up and asked him exactly how I could go about acquiring the skills I had seen him demonstrate in the water. Perfect horizontal trim, ascent control and precision finning, including backward and helicopter kicks. What would it take?

He and some friends, he said, after taking the course, decided to meet after work every Tuesday at the local quarry and practice these kicks and other skills until they had them mastered. They did this over a period of twelve weeks. These we call “Workout Dives”.

The fin kicks taught by GUE and by many other instructors who incorporate them into their teaching and diving – instructors like Duane Johnson, where I live here in the US Midwest – include the frog kick, modified frog kick, modified flutter, backward kick and helicopter kick. Each designed for specific situations and tasks, and to maximize efficient movement through the water with the least amount of drag.

The backward kick – designed to move you straight backward – the helicopter kick – designed to rotate about the horizontal plane without paddling with your hands; these are enormously useful moves, helpful when handling gear, cameras, an SMB, a lobster bag, and for simply maneuvering efficiently. (Read Duane’s article on the value of the backwards kick here). These kicks however require a damn bit of practice to become natural, but once learned these and other refined skills truly become “tools in a toolbox” – used interchangeably and on-the-fly as needed.

The very next week, a few of us who took Fundamentals began planning our “workout” dives, and we started right away – at the quarry or lake, every weekend. Through the Chicago winter we rented the high school deep diving pool ($15 for 3 hours) on Sunday nights and kept going.

And it became routine for us to focus a part of each regular dive on practicing one or more skills. Regular workout dives continued over the next four years, with participation growing to a network of divers with the same objectives, from divers working out the basics through technical- and cave-certified divers practicing with stage bottles, testing new equipment and keeping skills sharp.

The secret is that these dives are great fun; and invaluable for sharing information and tips, and learning from more advanced divers.

Here’s an example of an actual workout dive combining several target skills in sequence. A team is two or more divers.

Simple Workout Dive #1: A team leader and SMB diver is designated at the beginning of the dive. Team slowly descends in unison, facing each other, and keeping horizontal trim at all times during the dive.

Team stops from a direct descent one foot off the bottom, without touching or disturbing the sediment. Hold position off bottom for one minute. Team moves in direction indicated by leader for about 50 feet, maintaining one foot from bottom, using an appropriate kick style.

Reverse direction with helicopter kick, move another 50 feet, stop, and kick backward for about 25 feet – maintaining one foot distance off bottom. Bottom sediment must not be disturbed during the exercise.

Re-group 5’ off bottom; SMB diver deploys bag with team timing deployment to target time of 1 minute. Leader calls dive, initiates ascent, with 1 minute stops each at 40’, 30’, 20’ and 10’, with 30 second ascents between stops. Divers ascend together, maintain trim, face the team, and time their own stops. Final 10’ ascent must be slow to the surface. Each diver is critiqued by the team for improvements and advice.

This is a simple drill dive, but it reinforces basic planning, coordination, communication, control and situational awareness. It highlights individual and team skills that need to improve. As the team advances, greater complexity can be introduced, including multi-tasking and simulated emergencies – for example an out-of-air plus lost mask scenario.

A workout dive can be as simple as you and your buddy working on a single skill, like perfecting a backward kick, or as complex as a simulated technical dive with your full team. From simple to more complex, workout dives can progress through:

• Devoting the entire dive to practicing an individual skill (finning technique, SMB deployment, buoyancy control)
• Performing a structured sequence of skills (like the dive drill above)
• Introducing multi-tasking and simulated emergencies (combining all mastered basic skills with additional task loading)

Some of the basic drills on our list that we mix and match on our workout dives include:

1. Mask management (remove & replace, spare mask deployment, mask loss with buddy assist to surface, hand signals)
2. Finning technique (multiple kick styles)
3. Out-of-air drill with long hose/backup & buddy breathing
4. Coordinated descents & ascents (drysuit management, shallow stops, team formation)
5. Buoyancy control & trim management (fixed distance off bottom, travel in confined space, ascent stops)
6. SMB deployment (timed to one minute deployment)
7. Laying a line
8. Simulated low visibility (touch communication, team positioning)
9. Communication drills (hand signals, light signals, number drills)
10. Navigation & compass drills
11. Valve drills

The key is to include all these drills in rotation over many dives, focus on the areas you need to improve with individual practice, and most importantly to have fun doing it. Be sure to do all your workout dives in a calm, shallow water environment and take your time.

So I encourage you to grab several of your buddies, the ones who care, and practice the things you need to work on, starting with the basics. A structured, routine approach to mastering core skills will pay off with greater confidence and control in your diving.

In the end, you will become a better, safer diver and contribute more effectively to your team. Skills refinement will also lay a foundation for more advanced and technical training, if that is your goal.

Have fun and dive safe.

Jim Costopulos is a Chicago-area executive with an industrial products distribution company. He began diving as a teenager growing up in Southern California, with great shore diving and of course the Channel Islands. Currently diving in Lake Michigan, Lake Superior and local quarries – and back out to California whenever possible.