Posted by Murddoc on March 19, 2001 at 20:36:38:
In Reply to: "Wet steel" a no-no.....why? posted by AADIVER on March 18, 2001 at 23:18:34:
I know that the steel tank remains negatively bouyant regardless of how little air it contains. While an aluminum tank will go from negative to positive bouyancy as air is consumed.
Because of this, I have heard that a BC failure will make it difficult or impossible to ascend with a steel tank but not be a problem with an aluminum tank.
I adjust my weight belt to provide the necessary negative bouyancy at the beginning of the dive. However, the steel tank is not negative enough for me to dive with no weight belt. As a result, I use a weight belt but it is not as heavy as when I use an aluminum tank. I am not as experienced as most of the DIR crowd. Am I doing something wrong?
My steel tank is a 95 cf while my aluminum tank is 80 cf. So at the end of the dive I loose 7.2 lbs with the 95 and 6 lbs with the 80. The bouyancy change is a result of the tank size not the material from which it was made. And the net bouyancy change is more positive with the steel 95 than the aluminum 80.
If the goal is to gain enough positive bouyancy to ascend without the aid of the BC, they should differentiate between size not the material of the tank used. Or recommend ditchable weights.