Posted by Robin on November 01, 2001 at 09:44:39:
In Reply to: backplates shift center of gravity NOT reduce weighting posted by Karl S. on October 31, 2001 at 14:41:08:
soo many things to say, where can we start? Ok as to AL tanks
If you have to have a steel tank to keep weighted properly then there is another course that you should take that your current instructors seem to have overlooked "buoyancy control" HOWEVER, I am sure this is not the case Karl and I know that no matter what type of tank, you have the ability to weight and balance yourself properly so you can hold a 15ft safety with ease.
A diver should be able to adjust their buoyancy correctly no matter which type of tank they end up diving. Clearly steel is some peoples preference and so be it (although AL is by far the most used scuba tank!) but to say that steel is "safer" is a misstatement of fact.They are perhaps AS safe but..
Yes steel tanks do stay neutral or negative... so? The AIR contained within gains the same buoyancy as pressure drops regardless of container materials. The problem that some folks(those who have trouble with shoelaces too) have is the WHOLE tanks buoyancy is not the problem but rather that the bottom end of the tank becomes more buoyant than the top thereby upsetting the balance and causing incorrect and awkward swimming angles. (regulator and valve keep the top negative) This is so easy to deal with, just add one camstrap with a 4lb weight near the bottom of the tank and put the cam buckle to the side and weight between you and the tank. Comfy, "transparent", dithchable, transferable (to rental or other tanks) and cheap! (this is just one way to adjust the buoyancy and balance of a diver, there are more!).
We are still buying three AL tanks to ONE heavy steel which does not have the ability to become negative (and leaving out advantages of corrosion over rust).
Is it safer (barring all other factors) to have some major prob occurr and be found an hour or so later on the bottom or a minute or two later on the surface? I can gain the positive bouyancy edge in an emergency without going "overboard" and dumping too much by merely dropping or handing off the tank weight and ascending controlled.
Keep in mind this is not the only way to dive, merely another way and nobody has a corner on the ONLY way. my two bits.
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