Appeared in DIVER June 2007

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John John Bantin has been a full-time professional diving writer and underwater photographer since 1990. He makes around 300 dives each year testing diving equipment.

BC CRESSI-SUB BACK JAC

NEVER SAY NEVER. Today I find myself doing things I said I would never do. Mr Cressi finds himself in the same boat. After years of declining to make a wing-style BC, this year Cressi brings us the Back Jac (Back Lift in the USA), a back-flotation jacket and part of the new Aero range.
Whats the advantage of a wing Some say it puts buoyancy where you need it, at your back when swimming horizontally. I ask where else it would be, in either a wing or a conventional BC The air used for buoyancy control will always move to the highest point and, if the wing is well-designed, this will surely be at your shoulders.
A wing cannot provide forward support low-down when fully inflated at the surface, as a waistcoat-style BC does. Rig your weights too far forward and you will be pushed forward.
What wings do give, however, is masses of buoyancy, important when diving with multiple steel tanks. They also provide an uncluttered frontal area, which you can clutter up with stuff of your choice, such as the clipped-on sling tanks of the technical diver.
Yet this hasnt stopped the onrush of wings for ordinary leisure diving. Divers enter
the water with a single tank and the equivalent of a small inflatable dinghy on their backs. No wonder they feel pushed forwards at the surface.
The better wings are designed to inflate outwards at the bottom, with little displacement near the shoulders and none above them. By arranging your weights well round to the back, you can float upright, especially with the aluminium cylinders favoured the world over for single-cylinder dives.
Mr Cressi is a keen diver, which is hard luck for his designers. They cant get away with anything that doesnt work. When they chose the shape for the buoyancy cell, they got it right.

Surface comfort
The Back Jac harness has shoulder-straps that seem to have been cut to suit a woman. Thats not a problem for me. I find that I can often use a womans BC as well as one intended for a man, and not because Ive grown man-boobs. Its simply that jackets like this leave the chest area uncluttered - one of the original advantages of a wing.
The cummerbund is less easily accessible for adjustment than that of some other BCs,
but it was elasticated enough that I didnt have to bother. Theres the usual waist strap and pinch-clip to take the strain, and four stainless-steel D-rings plus some plastic ones.
The BC comes with a single camband, but this can be threaded to suit either an aluminium or steel tank. Hooray! At the lower level, there are enough slots to be able to use it with twinning-bands and blocks for independent double tanks.

Buoyancy control
Cressi BCs tend to provide everything you need in a BC for leisure diving, yet dont take up too much room in the dive bag. The Back Jac is inevitably bulkier than many of its more conventional siblings, because the harness is separate from the buoyancy cell and the weight system takes up space. That said, it works well.
For pockets, you have to make do with two drop-down jobs zipped away along the lower edge of the front of the harness.
This is because this area is taken up with the integrated-weight system that now employs an almost standard pouch with rip-away buckle and toggle design. Its good for 4.5kg each side.
Two little 2kg trim-weight pockets that are sandwiched between the harness and the buoyancy cell augment these weight pouches.
The drop-down pockets were not easy to locate and deploy under water, but the whole effect was so sleek that there was little resistance to impede my horizontal swimming.

Control of ascent
For shedding air during a vertical ascent, the dump valves are at the highest point, right on top of each shoulder. You operate one by pulling on the corrugated hose, the other by pulling on a cord finished off with a heavy toggle located at the right-side shoulder-strap facing.
Theres a lower dump, too, but this doesnt work well for horizontal ascents because when doing one it faces downwards. It works for fast head-down descents, however.
I never had a moment of doubt when dumping air, often a problem with some wings, although
I had to rotate a little to use the shoulder dumps effectively, and preferred to use the bottom dump, tipping forward to do so.

Surface support
The wing is not part of the harness, so there is no torso squeeze. It is shaped so that it expands outwards at the bottom when fully inflated to give proper surface support low down, yet is kept tidy at other times by discreet elastic cords. It provides 20kg maximum buoyancy in size M.
At the surface, the plentiful buoyancy low down was very effective in lifting me high out of the water. At the same time, once the Back Jac was fully inflated I felt nothing pushing me forwards.
My long legs forming a deep keel may account for this. Shorter people could face a problem, as the integrated-weights system does not afford you the luxury of getting the ballast round to the back.
If using an aluminium tank, I suggest you fill the trim-weight pockets and perhaps thread a weight onto your camband before putting too much into the front. Using a steel tank, it was preferable to put a couple of extra kilos on a weightbelt at the front rather than in the trim-weight pockets at the back.

Ease of removal
The weight-pouches were a snug fit for four standard 2kg block weights that only just zipped up inside, but they snapped into place positively, and pulled out as satisfyingly when the time came to pass them up to the boat. Similarly, it was easy to unclip a shoulder and swing the rig off.

RELATED CRESSI-SUB BC: AERO PRO

IF YOU LIKE THE CRESSI BACK JAC
but dont want a wing-style back-flotation BC, consider the Aero Pro. It has the same features and a few differences, such as the zipped pockets.
Cluttered up with the integrated-weight system and hose clips terminating at the same point, I found them quite difficult to get at and pull open during a dive.
That said, they provided a welcome stowing place for a small lamp, current hook and neoprene lens cap. A longer strip of ribbon or bigger toggle on the zips would solve the problem. On either side there are flaps with eyes for fixing a small knife holster.
I would also be inclined to shorten the inordinately long cord fitted to both the upper right dump and lower right back dumps. At any angle other than upright, the cord allows the toggle end to get lost, particularly on fast head-down descents.
It was easy to dump air by tugging on the long corrugated hose, which I tucked away under the elasticated sternum strap.
The Aero Pro proved quick and easy to put on before a dive and slick to get out of back at the surface.
I especially liked the buoyancy cell. Nothing protruded above the shoulders, so I never had to wriggle to shed the last of the air, and adjustment straps allow you to tighten those parts that sit like epaulettes.
The BC provides 18kg of buoyancy (size M) when fully inflated.
The buoyancy cell wraps cocoon-like around the tank, providing perfect buoyancy and trim when swimming horizontally. It widens towards the bottom to provide masses of lift low down at the surface.
The cell is gusseted with an elastic adjustment strap to allow you to choose how much of this lifting air passes into the front of the BC, so you can trim it to suit your tank, whether steel or aluminium.
Using the Cressi Aero Pro proved all sweetness and light apart from those easily sorted niggles. It comes in five sizes, XS-XL, and costs £393.

Divernet
The
The main integrated-weight system
Aero
Aero Pro
Aero
Aero Pros gusseted buoyancy cell

SPECS
CRESSI BACK JAC
COST £348
STYLE Wing
DRY WEIGHT n/a
POCKETS 2 drop-down
INTEGRATED WEIGHTS yes
D-RINGS 4 stainless-steel
MAX LIFT IN SIZE M 20kg
SIZES XS to XL
CONTACT www.cressi-sub.net, 01484 711113
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