Why can't I dive twice on the same tank?

[BamaCaveDiver]

Who taught you this technique of sharing air without it being an emergency, or emergency practice?

Please, don't take any offense to this, but I think it may be time for some SCUBA classes. Your air management seems unrealistic and sharing your air for no reason sounds like not a good idea.

Good luck!

A lot of us do this all the time Ace, we call it drills. If you wait until a true emergency, then you will have to waste a bit of time to think prior to reacting; if you practice these skills on a regular basis, it becomes second nature (muscle memory and all that garbage.) Even when I am diving solo, I will breathe my backup from time to time just to ensure its functionality.

As for banging the NDL's with an AL 80, it can be done quite easily. This is especially true for more experienced divers (the more you dive the more relaxed you should become and thus the better your SAC rate.) Women are notorius for having extremely low SAC rates to begin with, but I have met my share of male divers who I swear had to have gill implants.

[acelockco]

Bamma,

He/she is not talking about doing a drill, or as I called it "emergency practice".

I also don't think the person asking this question would be of the level you are speaking about concerning NDL with an AL80. Of course it can be done, without too much difficulty, but what we are talking about is hitting your NDL TWO TIMES with 1000PSI to spare. I can't figure it out, even with unreasonablly low SAC rates.

[littleleemur]

No offence taken acelockco. But I can't help being "unrealistic" about my air management. My air consumption has been the same since Day 1. So I guess I should take more SCUBA classes since the main indicator of skillz improvement is air consumption and it's been unchanged. Therefore I've obviously not improved as a diver.

No one has taught me this specific style of sharing air. I have a lot of it, more than I could "realistically" use. So I really don't see any harm in sharing any of it, regardless of whether it's a drill or not.

My original question was regarding "why" I was advised not to use the same tank twice -- logic and a basic understanding of psi vs. tank capacity didn't make sense to what they were telling me.

As for hitting the NDL, I have done it every time since my first checkout dive & can't currently see a reason where I won't continue to do so. As for a penetration dive for the dive profile I had used as an example, I have hit my NDL twice on the same tank multiple times with approximately 900psi (+/- 100) when allowed to do so.

[BamaCaveDiver]

My original question was regarding "why" I was advised not to use the same tank twice -- logic and a basic understanding of psi vs. tank capacity didn't make sense to what they were telling me.

He who owns the boat gets to make the rules, and for most deck hands it is just easier to look at the pressure rather than attempt to convert that into cubic feet. It might help if you found some off time to walk the objecting party through the math and show them that it is the cuft that matters more than the psi, then again it might have the opposite effect. I just let the owners make their rules and if I can live with those rules I patronize their business and do the dives. If the rules seem to silly to deal with, I look elsewhere.

[littleleemur]

It might help if you found some off time to walk the objecting party through the math and show them that it is the cuft that matters more than the psi, then again it might have the opposite effect.

That's what my rant is about:
1) I have to pay for a full fill even if I don't use a full tank.
2) I would rather have 1 less tank to schlep.
3) I can do it safely
4) I understand the physics, even if some don't

If the rules seem to silly to deal with, I look elsewhere.

I have no problem dealing with that I believe in always respecting the DMIC & the Boat Captain regardless of your level of training/specialty .

Anyways, thanks all for listening to my rant.

[amtrosie]

Bamma,

He/she is not talking about doing a drill, or as I called it "emergency practice".


.

What is a drill? Nothing more than simulating a scenario in which a specific procedure is required to mitigate the situation. Hence... an "emergency practice." It is most certainly a good idea to practice as often as possible. Heck, I have dives that are nothing more than one drill after another. What ever each member of the team can come up with. These may not be the most enjoyable, but they certainly are beneficial to the entire team. We always seem to manage to gain some insight to the scenario practiced.