Originally posted by Uncle Pug
Since you mention wetsuit.... the tank will probably be an AL
UP... why do you persist in this faulty logic?
In any wetsuit, the vast majority of divers will need weight in addition to a steel tank. Even with no wetsuit, I still need a weightbelt with a 12 litre steel tank.
** Suit compression is the only loss of boyancy that occurs during a dive - and is independant of tank type or number. **
Air consumed is the only increase in boyancy, - and is independant of tank type.
Using an Ali tank you will have to carry more weight due to the positive boyancy of the tank to be neutral at the surface post dive with an empty tank.
So - when diving steel, you carry enough weight to sink your exposure suit. When diving ali you carry enough weight to sink your exposure suit plus the positive boyancy of an empty ali.
Either way, if you are correctly weighted, the negative boyancy you have to swim up is equal to the compression of your exposure suit - Ali or Steel makes NO difference at all.
If you decide to ditch a weightbelt, you will be more positive with Ali than steel tanks - which I assume you agree is a bad thing as far as ascent rates are concerned.
Bottom line - as long as the total negative boyancy of all your tanks does not exceed the positive boyancy of your exposure suit at the surface, then the only boyancy decrease is due to suit compression. Therefore it is equally as easy to swim up a single ali 88 as it is to swim up doubled steels.
The only advantage of using Ali tanks is you get to try a polaris ascent if you ever lose your weight belt. Not sure why DIR considers this is a good thing, but each to their own
Oh - complete and abject apologies for the above rant if you were inferring that someone who can only afford a wetsuit would also only afford an Ali tank - they cost the same here, so I often forget that cost could be an issue.
BTW - I also think that Apeks are a good thing, I'm about buy my second TX100 so I only have one sort of reg when diving doubles. Also use a wrist mounted computer (although on my left wrist, as I tend to use a right side shoulder dump on ascent, and this way I can see my depth / time at the same time as I dump air, and have my right hand completely free.)
Mike