OK,
I'm a new diver but here's what I learned last week in G. Cayman (first "real" dives!) The North Wall by the way was intense! Hope this helps.......
I'm male weighing in @ 220 lbs. Some muscle, some flab
Cert. dives in cold freshwater quarry:
7 mil full wetsuit
7 mil hood
5 mil gloves
5 mil booties
Jet Fins (negative)
Rental Jacket style BC
28 lbs. on the belt, tried diving 24 lbs. but when down to 1000 psi I could not re-decend. Went back to 28#. The extra weight was needed for the hood, gloves, BC etc. Trim was horrible!
I decided to get the weight on my back and off the belt so I went out and got a FredT SS 9# backplate with his 2# STA's. There's 11# off the belt. I paired this up with an Oxycheq 45# wing (thank you SB!) and I'm sure I lost 2 or 3 lbs. "hidden" buoyancy going with the BP/W over the Jacket style. I did not get to dive this new rig yet in cold freshwater with same wetsuit etc. for direct comparison but will do so in the spring.
OK- Grand Cayman!
3 mil shortie (2# per mil so roughly 8# off the belt?)
Going fresh to salt (UP another 2#)
NO hood (some weight)
NO gloves (some weight)
NO jacket BC but 9# backplate, 2# STA's, Oxycheq 45# wing
Jet Fins
Rough calcs:
10% of 220# = 22#
- 11# rig = 11#
+ 2 Fw to Sw = 13#
- 2# hidden BC buoyancy = 11#
- 8# (7 mil to 3 mil = 4 mil x 2# = 8#
= 3# on the belt!
Almost forgot, diving Aluminum Tanks both instances. I'm guessing when I go back to my cold water config with a 10# P-Weight I'll be diving 5# on the belt. Or 15# with out the extra PWeight on the BP. Still, much better than 28#! So if I went with a steel tank I could actually dive this rig with NO weight and still be slightly heavy in seawater!
I wish I broke this out like this BEFORE I went to Cayman! I did some calcs using my freshwater 28# as a benchmark, wrong.....
I started out with 15# on the belt. WAY too much! To make a long story short my last 2 days I was diving 3# on the belt and using NO air in the wing, only lung volume! I attained neutral buoyancy throughout the dive! My hang was fine with 400-500 psi. When I was fine tuning I dropped my 6# belt at the line, did the dive with no weight and grabbed it on the way back up the line, a little light at 500 psi. (belt in my hand on the line so I was still diving no weight) Went back to 3#. Maybe a tweak of 1# in either direction but I'm there.
Thanks SB!