Gearing Up for Teamwork
In this issue we outline Will’s next step and the teamwork needed for a dive to 220m supported by 8 JJCCR divers. The team will be descending down a sheer rock face following the decent line we successfully tied off to 180m last month. The support divers will stage the bailout gases for Will and various other team members along this line. At this stage we estimate the deepest support divers will wait at a depth of 180m. Leaving Will to descend alone to 220m for this dive and 300m for the record dive.
Over the past 2 months Will has been diving on his JJ CCR almost daily practicing equipment malfunction drills as well as trying out different configurations suggested by team members.
Will has been diving with his rebreather with no modifications to 180m and it works perfectly but to increase efficiency of the machine at depth and to simplify things if it were to malfunction at depth we have made some minor adjustments to the standardized set up. Dave Tipping our Aussie paramedic and mid depth support diver did some number crunching with weight to gas ratios and realized the need to reduce the weighting at depth. In order to do this Simon had AP diving in the UK specially machine inline valves with no burst disc to fit American aluminium cylinders. This means we can replace the Steel cylinders (that come as standard with a JJ) for aluminium cylinders. Unlike steel cylinders, aluminium cylinders are not negatively buoyant. This saves valuable gas at depth and reduces the total weight carried by Will.
The next adjustment made was suggested by Jeff Glenn, deep support diver and owner of Bans Technical Diving in Koh Tao. The JJ diluent and Oxygen pressure gauges are located to the rear of the diver by the hip. To look at them you need to pull them down and move your head to look down. This is fine with normal CCR dives but quite tricky carrying 4 s80 stages. They are now rerouted over the shoulder so they are in view constantly.
Simon dives with no gauges at all (a controversial equipment configuration) His argument being, they are a weak point on a CCR because if the hose blows you loose all you O2 or all your Diluent. This could be potentially fatal. An experienced CCR diver doing dives to this depth will know when either his o2 or diluent supply is exhausted even without pressure gauges. If you have exhausted your gas supply you will be in the same situation whether or not you had pressure gauges attached to the cylinders. So how can an experienced CCR diver know he has exhausted his gas and still be safe? Well, in terms of o2 you would know your were O2 was depleted as the P02 would not be maintained and you would see it dropping lower than the set point on the handset hand set or the HUD (heads up display). In this instance you would simply plug in the back up 02 supply to the breathing loop and manually maintain the po2. In terms of diluent the wing would not inflate and the ADV would not inject gas into the loop. Once again the diver could plug in his deep off board diluent supply. So Simon’s argument is having the high pressure hoses creates an unnecessary risk of loosing all you gas and if you did loose your gas the backup procedure is the same whether you had gauges or not. The reader should bear in mind this technique is not recommended for recreational CCR divers and only considered due to the magnitude of sub 150 meter dives. Will understands Simon’s reasoning but still prefers to conduct his training dives with gauges for his 02 and diluent supply to collect data for gas usage and to spot a low on gas situation before it occurs so that he has time to prepare his response. He considers the risk of a ruptured hose or a leaking pressure gauge very low but regularly practices broken hose drills. The important point in technical CCR diving is that the diver must carefully weigh up the benefits and hazards of different equipment configurations and make his own choice. Familiarity is always a big deciding factor.
This then highlights some further considerations. Firstly a dedicated wing inflation cylinder will be used with of course and extra lpi from the onboard diluent should that fail. A manual diluent addition button has been added so that any of Will’s deep bailout mixes can be plugged in should the onboard diluent fail. Another extremely important benefit of this is to reduce the inhale effort of pulling on the ADV at depth. Already past 150m it became “noticeable”. If this does become a problem a simple push of a button will eliminate that physical stressor.
The dive has the following parameters. Descent rate of 30m per min. ascent from 220-140 is 12m per min. 140m to surface is 9m per min. Gradient factors of 30/85. Diluent and setpoint changes are shown above in the graph and air breaks taken on 50% nitrox are inserted into the plan as CNS for the dive is 180%. The dive is an hour shorter and less CNS if deco is done on open circuit 80% from 9m and upwards. Twin s80’s with a full face mask to safeguard against oxygen toxicity convulsions will give the gas needed to do this with an elevated sac of 20l per minute which is double Will’s actual.
The bailout plan will include the following gasses which include a 50% reserve. Support divers will further back up this gas with the same mixes on the line giving further reserve.
3365 ltrs of Trimix 4/84 suitable equivalent narcotic depth of 30m to buffer the effects of hpns and also to match up the diluent so that in can be plugged in in the event of losing or exhaustion of the onboard gas supply.
2333 ltrs of Trimix 10/60 from 145m
1970 ltrs of Trimix 15/50 from 75m
1975 ltrs of Triox 30/35 from 39m
576 ltrs of Nitrox 50 is for air breaks.
1872 ltrs of Nitrox 50 is for deco from 21m to 9m.
2800 ltrs of Nitrox 80 has less CNS than using 100% and actually reduces deco time by putting in at 9m.
All gasses step up in o2 content whilst gradually coming off the helium. Particular care has been taken not to increase the amount of nitrogen by too much at any point to stop Isobaric Counter Diffusion and the risk of a vestibular bend.
Over the next 2 months Will, Simon and the Blue Marlin Tech Team will conduct several more configuration and teamwork training dives to a max depth of 240m before the record attempt dive.