| I went from a single 15 (without pony) to twins of varying size. I checked the weight and buoyancy of all of them (without regs). Results for Faber single 15 vs. twin Faber 12's as below:
Twin 12's (with rubber boot) at 232 bar weighs 37.9 kg (6.6kg air), steel weight 31.3 kg.
Buoyancy full = -8.9, 40 bar -3.5, empty -2.3
15l single at 230 bar, full weight is 22.1kg (4.1kg of air), steel weight = 18.0kg.
Buoyancy full = -4.2, 40 bar -0.8, empty -0.1
Thus, the twin 12's were about 2kg less buoyant. Add another kilogram for the extra primary regulator and stuff and you have 3kg less weight to carry.
Weighting also depends on the difference between your harness/bcd (wing and plate?) using the single and what you are using now. E.g. a steel backplate has less buoyancy than an aluminium one.
Rule of thumb take 2kg off your belt for the twins. Add 2kg for salt water from fresh water. Do a test.
IMHO unless you can stay at 2m with 10 bar or less then the extra gas in the twins is just there for ballast and not available to breathe. Better too heavy than too light....
ATB
Ian  |