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January 2016    Download the Entire Issue (PDF) Available to the Public Vol. 42, No. 1   RSS Feed for Undercurrent Issues
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The Shortcomings of Winged BCs

do single-tank divers really need them?

from the January, 2016 issue of Undercurrent   Subscribe Now

One of our subscribers, J. Konstanza (Sacramento, CA), wrote to us, describing his problems with the Scubapro Knight Hawk, as well as his spouse's issues with the Scubapro Lady Hawk BCD -- common among BCDs that have a large buoyancy cell separate from the harness and independent from it. "Basically, I believe they have a flawed design that traps air on one side or the other of the BC. I have tried restringing the bladder ties, to no avail. I have tied them tighter and very loose, but it simply makes no difference. They trap air on one side, and we are diving lopsided. I am used to it now and routinely have to grab the lower left (while wearing the BC) and the lower vent on the right side, and squeeze. It was both dangerous and aggravating as a newbie diver, because if I could not vent the air from the BC, I would shoot up to the top. Now, it is just an aggravation. It also forces us to dive in a more heads-up position to try to keep the BC balanced. Thanks for addressing this matter, and I hope Scubapro will make some design changes."

The problem Konstanza describes is indeed real, and we speculate that he may have been sold an inappropriate product for the diving he does. So we asked John Bantin, our expert gear tester, for his take. Here's his reply:

A while back, wing-style BCs became popular with divers using multiple steel tanks because their large buoyancy cells provide plenty of support for all that weight at the surface, while offering an uncluttered chest area where multiple regulars otherwise hang ready for use. It wasn't long before equipment manufacturers realized there were many more people who weren't actually going to dive this way but to whom the configuration appealed. A plethora of wing-style BCs arrived in the marketplace intended for single-tank diving.

Alas, many "wannabe" technical divers demanded technical-style wings because 'they might want to dive double tanks one day.' These wing-style BCs come with larger buoyancy cells that may or may not be constricted by elastic strapping or cords, but whether they do or not, it can lead to some complications with single tanks.

A conventional vest-style BC has a buoyancy cell that wraps around the diver, so that any air that is introduced by the inflator will lodge at the highest point, which is usually behind the diver's head, at the shoulders. The corrugated hose or the dump valves are also located at that spot, so it is usually just a simple matter for the diver to release air during an ascent if he is looking where he is going. However, with winged BCs and bigger buoyancy cells, things may be different -- it might wrap around the tank instead.

The wing-style buoyancy cell does not follow the contours of the diver's torso, so the air might lodge someplace other than directly behind the diver's shoulders, unless the diver goes head-up. In worst-case scenarios, a cell without the elastic cord may wrap around a single tank, and air introduced at the left side by the inflator can remain at that side, causing the diver to feel lopsided, and making it difficult to jettison during an ascent if he stays in a horizontal position. On the other hand, when used with double tanks, it is not free to flap in this way.

In common with many other wing-style BCs, the Lady Hawk and Knight Hawk both have large buoyancy cells, and these are kept neat by some elastic cord. However, this can cause some crumpling of the material, and air can get caught in the loose folds, rather than progressing cleanly to the upper part - unless the diver makes a concerted effort to go upright in the water, maybe raising a left shoulder as he does so.

Some say these wing-style BCs with big buoyancy cells are unsuitable for use with a single tank, although it can be done. However, before you purchase one, you should ask yourself why you need it? Bigger is not always better. If you want a wing for use with a single tank, maybe you'd be better off with a smaller one, one fit for your purpose. A huge buoyancy-cell fully inflated behind your back at the surface does not necessarily add flotation when combined with only one tank, because much of it is above the surface at this time. For most, if not all, sport divers, a wing-style BC is not the answer to safe and comfortable diving.

wing-style BCs(In the photograph at left, John Bantin is using a typical large wing-style BC (without an elastic restricting cord) that has wrapped around the single tank and put the air within itself at a higher point than the dump valves or exit to the corrugated hose when the diver is horizontal.)

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