Quote:
| Originally Posted by Clare Gledhill We do 30 minutes on the bottom (plus a descent time which you would include on your calcs as a 35 minute dive) so only 5 to 10 minutes less than you on twin 12s and bottom stage. One twin set lasts two days but we kill a bottom stage on each dive. Gets us round the fill problems too. |
But do you not breathe some of the twinset on the way back up? Doesn't this (admittedly only slightly, assuming you don't breathe much of it) compromise your second dive?
One of the big reasons I went CCR became clear after my suspected bend last year. I could have been diving Nitrox, but didn't because of the logistical hassle, and so dived air.
Now you could argue that I could have sat out some of the dives, waiting for my twinset to fill but that wasn't an option. Generally if I go away for a weekend diving in the UK, the first fill is Nitrox, because I get that from the local shop. Fills throughout the weekend tend to be progressively weaker air tops, just because the dive shop closes.
The breather has obviously solved this, but it comes into it's own when you start talking mix. Often it's cheaper for me to top up my dil bottle with 18/52 then it is to air top it (as I'll have to drain it again before the next mix dive). So I now dive 18/52 for everything. Even if it's a 30m dive.
Gas costs and logistics are now no longer an issue for me. That's been a change in attitude on my part. Now you could argue that a breather isn't necessary to make that change in attitude. There are other ways. But a breather makes it sooo much easier.
Thing is, with OC everything is planned to the knife edge. "Rock bottom" and "Minimum gas" and even END. If you stay too long then you are significantly cutting into your into your reserves. CCR gives you time. Trapped in the wreck? Spend two hours cutting yourself free? On CCR you can make it (although don't expect any biscuits left when you surface).
Janos
PS - Mark - I'm afraid I must disagree re the 50m thing - for me the OC / CC switching point is between 30m and 40m (I'm not sure quite where). But definitely if you are diving regularly below 40m then I think CCR is significantly safer. Above 30m it's OC. The main reason being the time that CC gives you.