CCR cave diver training Part II – Trim and Propulsion are key and the essentials

Deep sinkhole photo shoot preparation Part II – Once we had done the modifications to the AP Diving Evolution Rebreather it was time to get the unit including diver into the water to see how the trim actually was with the unit. The major goal of most modifications was to get the diver horizontal in the water. By horizontal in the water I mean horizontal without a fight or struggle against or with the Rebreather.

Rebreathers have a tendency to go vertical with the diver as we have a lot of positive buoyancy around the chest, shoulder and head area with the counterlungs and loop. A lot of negative buoyancy tends to be in the butt area with the inverted tank valves and first stages, which are made out of very heavy and dense materials.

While moving the unit up on the body and move the wing down on the unit a lot is done for better trim. Add a stainless steel back plate and a light weight on top of the tanks if needed and here we go. Every pound counts from light fins to a dry suit where you have a bit of air on your legs. The diver is comfortably horizontal in the water without struggle. Now we can focus on the essentials for cave diver training. Trim – done. Propulsion – working on it. Rebreather emergency drills such as the H’s (hypercapnia, hyperoxia and hypoxia) – we will see … don’t forget the boom scenario.

As we have the horizontal trim with our legs up position we can focus on propulsion. The frog kick I would think is the most important of all kicks followed by the reverse frog kick in order to back up. The helicopter turn is important to, so is the modified flutter kick. The shuffle kick is hardly used, even less the modified dolphin kick. The pull and glide is used mostly in restrictions.

As we have now good trim and propulsion we need to focus on the Rebreather related emergency drills before we can even think of going into the overhead environment. If we can’t do them in the openwater we can’t move into the cave.

The most life threatening emergencies are all related to toxic breathing gas such as to much co2 – hypercapnia, to much o2 – hyperoxia and not enough of o2 – hypoxia or as well called the three H’s. Another big one is the boom scenario with internal or external booms or uncontrolled release or loss of gases. There are many ways to deal with that but I found that the simplest and easiest is the most effective in terms as one response deals with almost all emergencies.

To get off the loop is paramount to check your brain and navigation. You need to check your brain to see if you potentially made a navigational mistake. Once off the loop and on bailout check with your team mates if they are still there and they know you have an issue. Call the dive and move out of the cave.

If you desire to work on your Rebreather and get it back going cause it is a small problem such as bumped close o2 valve or stuck open solenoid you may do so on the way out. But you don’t have to. That is why we carry pre-calculated amounts of optimized bailout gas with us. We are … aren’t we … or are you not ?.

As time goes by and the training goes on the student, in this case Paul Nicklen is getting proficient in his trim thanx to the unit modification, proficient on the propulsion but still struggling a bit on the backward kick and proficient on the bailout scenarios thanx to the simplicity of the bailout response … that is get off the loop, change your handset computer from cc to oc and move out of the cave.

The important part is to have enough time to develop trim, propulsion and Rebreather emergency drills in the open water before moving into the cave where we need to repeat them. If the student can not do them in the openwater no need to go into the cave and see how much fun that might be.

For Rebreather divers who might a bit rusty the Essential prep training program is a valuable tool in order to be ready when the cave diver training program starts. Another important part of the Essential Diver prep program is to heighten student awareness in regards to unit preparation before putting the unit on our back. We need to put a life support system on our back – not a tomb stone. The unit must be functional before being put on. Period. If not it can be forgotten in a rush and we would end up belly up because we forgot to turn on valves or electronics.

Stay tuned for Part III – The CCR Cave Diver training program & Part IV The CCR Normoxic Trimix training program.


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