I have not taken the DIR-F class yet, but hope to do so in Jan. or Feb.
It is my understanding that (according to DIR methodology) when diving wet you always dive an aluminum tank and that to dive with a steel tank you must dive dry for the redundant buoyancy in case of wing failure.
I know I'm missing something when I think this thing through, but here is what I keep tripping over.
Let me use the example of diving wet.
I'm assuming that ditching weight is an undesireable thing to do and that it should be avoided. With that in mind, if I am weighted to be neutral at 10 ft with 500 psi the weight of the gas is my only difference from full to empty. This should hold true with an AL 80 or a steel 80. Given equal sized tanks, the difference in buoyancy at depth will simply be due to the compression of my wetsuit.
I understand that with an aluminum tank I put more weight on my weight belt and that with a steel tank I take some weight off of my belt. The buoyancy swing on an AL 80 goes approximately from - 3.5 to + 2.5 and a steel 80 goes from - 8.5 to - 2.5. So the difference on your weight belt is simply 5 pounds.
I also understand that this difference increases with a larger steel tank. For instance, if one opts for an E-8 130 the swing goes from - 1 to - 10.5. That's a difference on your weight belt of 7 pounds when full and 3.5 pounds when empty compared to an AL 80.
If properly weighted, the difference seems minimal even when taking the full 7 pound difference between an AL 80 and steel 130.
Where is it that I am not thinking this through properly? I'm not looking to argue the point. I'm willing to accept that this is true, but I just want to understand why. Hypothetical examples may be helpful.
Thanks.
Christian
It is my understanding that (according to DIR methodology) when diving wet you always dive an aluminum tank and that to dive with a steel tank you must dive dry for the redundant buoyancy in case of wing failure.
I know I'm missing something when I think this thing through, but here is what I keep tripping over.
Let me use the example of diving wet.
I'm assuming that ditching weight is an undesireable thing to do and that it should be avoided. With that in mind, if I am weighted to be neutral at 10 ft with 500 psi the weight of the gas is my only difference from full to empty. This should hold true with an AL 80 or a steel 80. Given equal sized tanks, the difference in buoyancy at depth will simply be due to the compression of my wetsuit.
I understand that with an aluminum tank I put more weight on my weight belt and that with a steel tank I take some weight off of my belt. The buoyancy swing on an AL 80 goes approximately from - 3.5 to + 2.5 and a steel 80 goes from - 8.5 to - 2.5. So the difference on your weight belt is simply 5 pounds.
I also understand that this difference increases with a larger steel tank. For instance, if one opts for an E-8 130 the swing goes from - 1 to - 10.5. That's a difference on your weight belt of 7 pounds when full and 3.5 pounds when empty compared to an AL 80.
If properly weighted, the difference seems minimal even when taking the full 7 pound difference between an AL 80 and steel 130.
Where is it that I am not thinking this through properly? I'm not looking to argue the point. I'm willing to accept that this is true, but I just want to understand why. Hypothetical examples may be helpful.
Thanks.
Christian