An inherent problem for rebreather divers has always been the difficulty in achieving proper trim in the water. As experienced divers will tell you, proper trim is more than just your ability to orient yourself horizontally - it's the ability to stay there, perfectly balanced, while not finning or moving. Having to constantly fin to maintain proper trim is subliminally task loading. When faced with deploying a reel, or managing an emergency, the task suddenly becomes that much more complex when you find yourself needing to fin for proper trim.
Many rebreather have this trim issue because of the 'inverted tanks,' inherent in the design. Most, if not all rebreathers have their O2 and diluent bottles mounted where the valve is on the bottom, moving more weight to the bottom of the diver, and affecting their center of balance. It is also affected by the counterlungs themselves. For proper hydrostatic loading and low work of breathing, the gas in the counterungs is ideally located at the same level in the water column as the lungs. Fo rate horizontal diver, this is generally above the shudders, adding to the imbalance of the diver.
What's the solution? This problem can be somewhat mitigated by the use of a drysuit. Adding gas to the legs helps keep the diver nice and level. But what about when wetsuit diving? Enter the Halcyon CCR 35 wing. Designed by expedition diver Mike Barnette, the CCR 35 wing was engineered to put the lift where the rebreather diver needed it - down low. The earliest versions of the CCR-35 were designed for the Megalodon and the KISS rebreathers; however, subsequent field use has demonstrated this wing is ideal for most closed-circuit rebreathers utilizing inverted cylinders.
Designer Mike Barnette writes:
There are numerous wings on the market that work fine for open circuit technical divers ì doubles are pretty much doubles. In contrast, most rebreathers are much shorter packages, and weight distribution is much different. We tweaked our configuration as much as possible, trying to get perfect trim like we were used to on open circuit. However, because of the shortness of the rebreather, the OTS counter-lungs, and the fact the valves are positioned on the bottom (i.e., bottom heavy), we still had some niggling issues with trim and attitude. To help with our trim, we could have reversed the bottles and put the valves at the top, but we felt there were some drawbacks to this approach. Conventional wings simply trapped the small amount of compensating gas needed when diving the rebreather in the wrong area of the wing. Other wings were too long for the unit, and in our eyes some doughnut-style wings presented a failure potential due to repetitive stress (pinching) on the lower portion of the wing when sitting down on boat benches, etc. I personally felt a wing with a more appropriate design would be the solution to our dilemma. And, for us, it ultimately has. To their credit, Halcyon helped fabricate a better wing for our rebreathers.
A range of carefully engineered design features is sure to impress even hard-core CCR divers:
- 35 pounds (16 kg) of carefully tailored buoyancy provide the right amount of lift in exactly the right places.
- Standard 11-inch, on-center grommet holes provide easy attachment to most CCRs.
- Limits lift behind diver_s head; lift near inverted valves supports horizontal trim and diver_s balance.
- Offset inflator elbow supports easy access to the rebreather while keeping the inflator clear of the breathing loop.
- Slotted wing allows supply hoses to route through the wing, keeping hoses streamlined and close to the body.
- OPV is positioned to limit interference with open-circuit bailout bottles and to support easy venting.