Dove this weekend back at Dive Haven quarry in White, Georgia. It was the monthly Dive and Dine with the other Lake Lanier Looney Birds. We had a fair turnout with 8 divers and one wife. Some folks did 3 dives, others did two. I got in a little late so missed the first dive and only did two.

I decided instead of carting the camera or playing with the dive scooters I wanted to concentrate on working with buoyancy control (hence the picture for this entry, my OxyCheg dive wing.)

What I found was that you need to make small adjustments when submerging. Using a vest or back inflate I would usually just let all the air out and then pop some in as I neared my target depth. With the doubles and BP/W arrangement this would usually result in overshooting the depth and playing yo-yo until I got in trim. I decided to just burp a little air out at a time until I submerged, then just a tad more until I sank. This resulted in a much finer control.

You see, with doubles you need to start out a bit ore negative than with singles. In Aluminum 80's the buoyancy swing from full (-4 pounds) to 500 PSI (+2 pounds) is in total about 6 pounds. Using a single tank you can compensate for this using just enough to compensate for the +2 pounds at 500 PSI and then adjusting your lung volume, this doesn't work with doubles. You need to be compensating for at least 4 pounds, and sometimes the entire 6 pound swing of the second bottle, which usually exceeds the capability of your lungs to compensate for. This use of doubles requires you to carry a bit more lead to start (generally speaking) and to be therefore a bit more negatively buoyant. This means you can't empty your wing of air or you will sink like a rock.

You also have to be more patient with buoyancy adjustments at depth, you have more mass than you may be used to (usually at least 50-70 pounds more than with a single tank) and therefore it will take a bit longer for changes in buoyancy to become apparent. This leads to over filling the wing (or dry suit) with air, then having to dump as you begin to ascend too fast.

So gentle does it when dealing with BP/W, dry suit and doubles.