| Imported post
300 bar is only usefull if you can guarantee you will get a decent fill, even then gas laws dictate the effective pressure is more like 260bar. I recently thought about twin 7's but a report in Diver indicated gas loss at 30l/sec if you lose a first stage to free flow. The amount of gas loss would need to be planned for in case of an emergency during ascent. When I calculated what I would need to start my ascent with in case of this gas loss I ended up with very little for the dive, especially if I could only get 220 bar fills in some remote location. It might be possible to run as independants and still use them though.
I'd echo what everyone else is saying 30mins at 30mtr from a 12l is good going, so dont worry about your gas consumption too much. Get a pony at the very least for both you and your buddy, if you lose your main tank at 30m its not going to be easy getting to the surface on your own if you cant get to your buddy quickly.
My SAC is STILL 25l/m (after almost 60 dives), it has stayed the same since I started diving and I agree it is a bit embarrasing to be first back on the boat, life sucks sometimes, so I normally try and get in last instead. This give me more time to kit up, I can help others (which they appreciate) and my buddy understands my gas consumption and if I'm back first I'll make the tea/coffee and help the other back in. Usually though if I'm last in I'm not first out.
Plus it gives me a reason to go back and dive the site again sometime - everyone's a winner.
Additionally it will keep you away from NDL by a margin and that can only be a GOOD thing in my view, in fact I've just done Nitrox to keep me even further away from any limits.
Enjoy.
HTH
Matt  |