Oops; swap them aound typo. Editing now...I don't consider myself a mathematical genius, but I am fairly certain your calculations are incorrect.
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Oops; swap them aound typo. Editing now...I don't consider myself a mathematical genius, but I am fairly certain your calculations are incorrect.
Need to convert to bar: 3000psi = 206bar, 2700psi = 186bar.
Obviously it depends upon circumstances, but in essence yes. It's probably more relevant for a cave penetration rather than a wreck penetration (wrecks aren't as long as caves!) where you've ended up using more than your third of gas and are now eating into your reserves.
For a wreck penetration, you'd have worked out your max TTS (time to surface) and your minimum gas. If your "disaster" (post leak) happens when you're in deep and you realise that you're now getting close to your TTS / min gas, getting out is definitely time critical. That 20bar / 300psi could make all the difference. If it really is a long or complex penetration, you can simply leave the line there and collect it another day; same with a cave for that matter -- much better to have a story on the boat / in the pub than to scare yourself witless with worry because you're now short of gas.
(The example numbers you used would have been better if they were lower, e.g. at the turn point, so call it 1700psi / 117bar and 2000psi / 137bar - here the loss of 300psi / 20 bar is more significant)
Edit: typo 2700 & 3000 swapped
I specifically said deco gas. Nobody is talking about using only a mini SPG on your back gas.
So, 2700 in your deco gas, but mini SPG says 3000. What would you do differently if your gauge actually said 2700?
When you are on deco and it gets hard to breathe, it is about time to come up, you don't need a fancy gauge to tell you that. LOL
Skip a stop completely? Or 'trim' the previous stops because you knew the gas remaining?
I've been diving for a long, long time, so perhaps I've lost touch with what people are doing these days, but the idea of using a small safety cylinder, what we called a bail-out bottle, for decompression fills me with horror. The gas needed for decompression should, I strongly believe, be factored into the dive plan from the primary cylinder(s). These little 15 or 20cf bottles are for emergencies, redundant sources of air. I've always thought that the rule of thirds was more than just a good idea: it was obligatory. Squeezing every minute possible from a dive by nearly depleting the main air source and relying on a small secondary source to complete any required decomp while doing ordinary sport diving is the hallmark of a fool.
Yeah I was wondering what he was on about too.Fortunately, I don’t think anybody in this thread has said anything like that...