I have just switched to a BPW after over 600 dives with a jacket and am trying to get some starting points by going to a pool and to work out weight distribution for trim. I have 3 wetsuit configurations (7mm full, 1.5mm full, and no neoprene, i.e. skin) and 2 tank types/capacities (AL80 and S100) I want to work out. Due to the steel backplate, only the 7mm cases needs additional lead so I plan to "overweight" by 2-4 lbs for trim weights (and keep some gas in my BCD). Extra lead (when needed) will be in a weight belt. (BTW, I am not concerned about not having any ditchable weight because I carry an SMB which can provide lift in the rare case of a total BCD failure.)
I have adjusted the harness as has been mentioned in this forum and plan to mount the AL80 as low as possible (upper cam band at the start of the tank curve) and the S100 about 4" higher when I am using it. I want to understand trim at 90 feet with a full tank and at 15' with 500psi remaining but, obviously, can't do 90 feet in the 15' deep pool. Therefore my thought is to establish a "midpoint trim" by using an AL80 which is 35% full (~1000psi) and an S100 at 50% full (~1800psi). My thinking is that if I get to horizontal trim under those conditions, the change across 15ft/500psi to 90ft/full range will be manageable by adjusting body position.
Since I will most likely be doing this in the pool alone (long story), my plan is to get slightly negative and motionless on the pool bottom then take a deep breath (or put air in the BCD), push off, and see which end rises. I will have some weights with me that I will pick up and position toward the end that rises so I know where to add the trim weight.
I would start with the 1.5mm wetsuit case and do the above experiment with both the AL80 and S100 and then repeat with the 7mm and no wetsuit cases.
I am very interested in what you people think about this plan.... so don't hold back.
