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Mike, It's SOP these days to dive the Halcyon with outboard twins. The cylinders are connected via an extended isolation manifold and function exactly like a set of DIR rigged OC doubles with the exception of two additional hoses. The first extra hose feeds the rebreather. The second goes to the OC second stage integrated into the mouthpiece. This answers your question about OC bailout - the twins serve both purposes. For ocean dives, twin 46's are a lot of gas. Especially if you _are_ carrying a deco stage. I'm still a novice Halcyon diver and very inefficient in my RB gas management but for the profile you note below, I never use more than 400psi and most of that is from practicing contingency procedures on OC. I'm positive RMC, Jess, George... would use a miniscule amount of gas, leaving plenty for bailout. Remember, according to DIR, ocean deco obligations are kept as short as possible. The philosophy behind the Halcyon is that it is a gas management tool that seeks to increase the efficiency of gas usage while remaining as close to OC simplicity and redundancy as possible. Why they don't carry a stage, beats me. It is incredibly simple to change gases under water on the Halcyon. I carry a small stage (Al30) of 50%. If/when I start doing bigger dives, I'll make the 50% an AL40 and add an AL30 of O2. Robert, Jess, jump in if I've left something out. Thomas >From: "Mike Langborg" <mslangborg@cl*.ne*> >Subject: Halcyon rebreather >Date: Thu, 27 May 1999 21:37:18 +0200 >On a resent diver trip down south (Waymouth) we met some DIR divers. = >Some dived the Halcyon Rebreather (open water). >It was rigged with two 7 litres (45 Cft.) on the sides of the unit. We = >asked if they did not use stages for DECO, and the answer was : NO >They dived to about 30 meter (100 ft) so I can se why they might opt to = >leave stages, but when we asked if they used stages on the deeper dives = >the answer was still : NO. >My question is therefor. Is this standard DIR(WKPP) procedures. If so = >why? Since this unit is NOT constant PPO2 you must have a longer = >hangtime compared to OC (and what about OC bailout?). >Secondly why are the bottom mix carried on the back (on the sides of the = >unit) when a single stage would do the same, and easily can be carried = >along the deco stages? >It doesn't make sense to me, so please enlighten me. >Mike -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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