[SoB]

All,

I'm looking to trade down from two steel 10ltrs and get some stage cylinders - with DIR Tech-1 in mind. The 10's are a hang-over from going twin when I wasn't comfortable with 2x12 and was looking at a possible 2x10 (which I never did in the end). They only ended up being used as pool cylinders.

So, questions I'm not certain about are Steel or Ali, 5 or 7 if steel or 80 if ali?

I've already had some good feedback that 7's or 80's are the way for Tech-1 but I'm still at a loss of the Steel/Ali question. First - I have no real preference.

I understand that Ali's are actually heavier out of the water than steel but that due to the lighter metal requiring thicker/bigger build the displacement means that they are naturally more bouyant in-water. However is this so good a benefit when trying to hold bouyancy at the end of a dive.

If an Ali7 is 8.5kgs and a Steel is 7.5kg's but in the water the Ali regains 1.5kg bouyancy then in effect the Ali is only 7kg so only 0.5 kgs lighter - they must both gain the same amount of bouyancy as the gas content is reduced therefore my initial feeling is that I would prefer steel.

However if the suggestion is to go for an Ali80 then as I already have steel 10's am I not just spending money on an Ali version of the thing I have?

All comments gratefully received.

Thank you,
Simon