Drager Dolphin Extreme – Semi Closed Rebreather in Thailand
Big Blue Tech have been rebuilding a Drager Dolphin Semi Closed Rebreather in an attempt to create a Semi Closed Rebreather that functions and resembles the Halcyon RB80
The Drager Dolphin SCR always had some draw back that kept it from being respected amongst the more adventurous divers:
1. The in water trim was terrible; The breathing bag or counter lung was located in the top of the unit and the steel cylinder slung in the bottom which made the diver very vertical, almost like a baloon with a weight tied on to the bottom. Additionally the bail out cylinder was mounted on the side making it unbalanced even if you did get vertical in the water.
2. The blue “Commando” bcd wasn’t black.
3. The white box that held the breathing bag wasn’t black
4. The small steel cylinder wasn’t big enough and a larger cylinder would only make the unit worse.
5. There was no way to mount deco or stage tanks.
6. The BCD was restrictive and could not be used with a backplate and harness.
Our initial purchase of a used unit in thailand gave us everything we would need including the oxygen sensor for our pp02 display. Out of the box, the unit was working perfectly with all the tests passed and no leaks.
Our first goal was to remove the old and restrictive built in bouyancy compensating jacket to allow the installation of a backplate and wing mounting system. This mounting system from V4Tec would allow all technical diving backplates and wings to be fitted in the same manner you fit diving gear to twin tanks.
The mounting system and side by side tank brakets arrived and fit perfectly. This alteration improved trim, bouyancy immediately. With the twin 6Lt (S40) cylinders mounted side by side it was difficult not to be balanced and horizontal.
The final and most dramatic improvement was the flexible manifold. Contacting our friends in Pattaya who own an engineer shop, we were able to source the high pressure hydraulic hose along with the fittings for our cylinders. This would give us redundancy and increased gas volume. We would still carry a bailout but that could be slung from the harness.
The testing later moved into shallow water trials where different divers of different skill levels went for a short dive to test the trim and overall experience. While this would be their first time in a rebreather they found it quite easy to reach neutral bouyancy and effective trim. The divers practiced bail out techniques and general rebreather loop use.
Open water ocean trials will be conducted in the near future to test exposure limits and functionality in saltwater.