Ok, I dive with double-12s and need 1 kg extra lead. I also dive with a single 15 litre and use 3 kg extra lead. My 12s with 125 bar of air weigh 33.3kg, so the tanks weight about 29.4kg. The 15 ltr weighs 21.3kg with 105bar so about 19.4kg empty.
So, the 15 litre is 4.4 kg negative, and the 12s are 5.4 kg negative (if we only consider displacement from air volume - is there a way to estimate displacement from the cylinder material and valves?)
In theory then if I got some 7s which were also about 5.4 kg heavier than their air displacement they would be about right. So, about 14 + 5.4 = 19.4 kg, and I would probably need a kilo of lead extra... or 20.5 kg would make them perfect. Though possibly too heavy if I went to a thinner undersuit in summer.
Does any of this make sense?
So, the 15 litre is 4.4 kg negative, and the 12s are 5.4 kg negative (if we only consider displacement from air volume - is there a way to estimate displacement from the cylinder material and valves?)
In theory then if I got some 7s which were also about 5.4 kg heavier than their air displacement they would be about right. So, about 14 + 5.4 = 19.4 kg, and I would probably need a kilo of lead extra... or 20.5 kg would make them perfect. Though possibly too heavy if I went to a thinner undersuit in summer.
Does any of this make sense?
