BP&W Foating Face Down on The Surface

[OE2X]

I have read with great interest about people saying that BP&W's will turtle you and only float you face down on the surface. I decided to do a very unscientific experiment to see if this was myth or fact.

Equipment:
PST E8 130 Tank w/ 1200 PSI EAN32
Wing - Oxycheq 45# Signature wing
BP - Koplin 10# with 6# STA
Terkel can light mounted on right waist belt
Halcyon Scout back up mounted on right shoulder strap
DUI CF 200 Drysuit
Weight Belt - 3# per side
Fins - SP jets w/spring straps

In the water (salt) I vented all the air out of my drysuit. I added just enough air in my BP&W to float my head out the water. I then went prone face up. If my arms were spread slightly and I finned a couple of times then I could achieve face up floating posture. With a puff or two of air in the BP&W I had my chest completely out of the water. Fins and feet now floated on the surface. No effort was involved to stay on the surface. I then inflated my BP&W all the way and found that I turned toward my right side at no more than a 45 degree angle. When I infated my drysuit all the way then I was able to roll onto my stomach - face down. This was achieved by dropping my arms to my sides.

Conclusion: I think that the only reason I could turn onto my right side was because of the slightly negative qualities of the can light and back up light on that side. While I don't notice any turtleing with this configuration while diving it still makes sense that this could be the cause. As to being face down - what caused that was an overinflated drysuit and BP&W. Here I was surprised by the results. I actually found that the nearly 18# of negative weight on my back served as a keel. For the most part it was a very stabilizing factor in keeping me face up on the surface.
While this was very unscientific and I only used one BP&W it mirrored what I saw happen to Uncle Pug with his Halcyon BP&W. Obviously more of this type of testing needs to be done before we BP&W owners say emphatically that you will float face up on the surface. The trend does appear to be in our favor though.

 

[jagfish]

Hey
Just did my first dive with my BP/W and I was at least initially pleasantly surprised at the surface. 6.5 mm wetsuit and AL80, SS BP and Heavy STA and 8 pounds in ACB pockets. No accessories. I was rock solid vertical at the surface, though I am not sure how much air I had in the Elcipse 40. Perhaps 50 to 75% full.

However, at the end of the dive, when the tank was near 500 psi, I had to have less air in the wing, or I was being pushed forward slightly. Once the tank neared empty, its boyancy began to exert an influence, opposite of the "keel effect" described in the above post.

JAG

 

[OE2X]

However, at the end of the dive, when the tank was near 500 psi, I had to have less air in the wing, or I was being pushed forward slightly. Once the tank neared empty, its boyancy began to exert an influence, opposite of the "keel effect" described in the above post.

JAG

Jag,
You brought up an interesting point about using the Al 80 that I hadn't thought about. They go what 4-6# positive when empty? This is a similar effect to inflating the drysuit. Since I dive only with steel tanks being pushed forward is not going to be the same as using AL tanks. Also when empty my steel 130 will be either 1 or 2 #'s negative thus giving me more keel like performance.

 

[jagfish]

Yup, the aluminum swing...
Wreaks havoc on my drysuit trim...

Regarding tanks...
For better or worse, you pretty much have to dive with what the dive sites have over here. Depending on the site, I dive with 10 L in AL or 10, 12 or 14 L in Steel. Makes it really tough to get a handle on weighting and trim considering the different exposure protectoin you might wear with those tanks seasonally...

JAG

 

[DA Aquamaster]

I have not found any difficulty consitently floating face up with a BP/Wing and a tank or pair of tanks that are no more than neutrally bouyant at the end of the dive. All it requires is some care to keep the weight as close to the backplate as possible. Weight belts are not very effective in this application and a well designed set of integrated weight pouches work better.