denniscloutier
Contributor
Maybe I misunderstood you and I did chop this quote up to make my point but are you saying you went to 140' on an AL 80.
If so I would not be giving that advice to anyone.
If you or your buddy was to have a failure you were both in major trouble to say the least. Single tank diving to non-recreational depths with no deco training is asking for an accident.
I for one will not dive an AL 80 past 80 feet, my rule of thumb is to not pass the cubic feet value in feet of sea water. But that's me.
Just to be clear, I didn't recommend that anyone exceed the rec diving limit of 130'. That was a mistake on our part.
However, I don't understand the 80' limit. I'm not an expert, but my understanding is that the main principle behind gas planning was that you start your ascent with enough air for both divers to make a safe ascent on the least full tank. I have also heard a rule of thirds suggested whereby you turn around with 1/3 of your air gone and are out of the water with 1/3 still left in your tank. We did extra safety stops, and doubled the length of our 15' safety stop as suggested by the guides, and we were typically still in the boat with about 1000 psi left in our tanks on the deep dives. So, where is the problem?