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Replace some of the nitrogen with helium. Do you have to have it spelled out totally for you? Go run the numbers. You might want to consider picking a high helium content. This is in reference to the multiple bottle example. Apparently you have forgotten or ignored that part of the thread.
When I say drag, I mean they tanks will be hanging down out of the slipstream. With less weight (i.e. replace some of the nitrogen with helium), they tanks will start out closer to neutral. This is in reference to stage bottles if you haven't quite picked up on that yet.
Also, you might note that volume is related to pressure. Now try applying that to what everyone knows is the density of water. Yes, that was in the PADI OW manual. Since I know the volume displaced and the density of the water, I can easily figure out the buoyant force. You might want to actually take a physics class since the dive industry has totally failed in teaching you this information.
You keep putting your foot in your mouth. You must be an instructor.
When I say drag, I mean they tanks will be hanging down out of the slipstream. With less weight (i.e. replace some of the nitrogen with helium), they tanks will start out closer to neutral. This is in reference to stage bottles if you haven't quite picked up on that yet.
Also, you might note that volume is related to pressure. Now try applying that to what everyone knows is the density of water. Yes, that was in the PADI OW manual. Since I know the volume displaced and the density of the water, I can easily figure out the buoyant force. You might want to actually take a physics class since the dive industry has totally failed in teaching you this information.
You keep putting your foot in your mouth. You must be an instructor.
msandler:sorry, guess I should explain that the example given by Dan is not tangible in actual diving. first a type helium mix would contain about 30% Helium (the weight difference in the stage would be negligible). His calculations are invalid for the variety of equipment being used (different tanks, different regs.), or even the equipment he is specifically referencing. You get the picture? Also, typically helium would be "back gas" Dan is only mentioning Al80's because that's what he got out of the DIR philosophy. He has missed the boat on the very sound principles of "DIR". For example, there are plenty of dives that call for other size tanks - deep deco dives where a travel gas is useful to minimize deco times - you would probably only need 20 - 30 cuft of a specific mix for a given portion of the dive, so why bring 80?
Your pal's lack of real diving experience with the systems, situations and mixtures he is referring to in his posts is blatantly obvious. I hope he doesn't misslead to many people.