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

[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.