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Gearmiester answers your questions about BCD FEATURES...

Features! Get your features!
For the past two months, we explored the evolution of the Buoyancy Compensation Device, BCD, and how it functions. This month, let's take a look at some extra features that you may find on BCDs.

It’s all about style
There are three main styles of BCDs for recreational diving - jacket, back-inflation, and hybrid. These terms refer to where the main portion of buoyancy is located in the BCD when it's inflated.

Back inflation style. All of the buoyancy is carried behind the diver around the cylinder. This helps to provide a very stable and horizontal position underwater with less drag than a jacket style. On the surface, even with a fully inflated BCD, there is no feeling of squeeze. However, there is a tendency for the BCD to roll the diver forward. After a few minutes of practice, most divers can find the new balance point and it’s not much of a problem. 


Jacket style. The air bladder not only goes around the cylinder in back, but also around the sides of the BCD. This provides a very stable and upright position on the surface, but can tend to roll the diver around under water, especially if over-weighted. Also, when fully inflated on the surface, it can give the diver a feeling of being squeezed.

Hybrid styles combine the best features of both jacket and back inflation styles and try to provide horizontal stability under water as well as upright stability on the surface.

There's also “travel” BCD’s - stripped down versions of the other styles that are designed to save weight and space while traveling. While they do a good job of that, it comes at the cost of other features. So, as with all dive gear, make sure it fits your needs before buying.

A weighty subject
We remember from our basic scuba class that proper weighting is important to safe and fun diving. But there are really two parts to proper weighting – the amount of weight, and the location of that weight, known as trim.

The proper amount of weight depends on the diver's body size, composition, and mass, equipment used, thermal protection worn, and whether diving in fresh or salt water. Once you have the proper amount of weight, you need a way to carry it in the water. Most of us learned scuba using a weight belt and weight belts are still used in most scuba training.

More and more BCD’s offer an "integrated weight system". Instead of a belt, the weight is carried in two pockets, usually located toward the front and bottom of the BCD. The weight is divided between these two pockets which close with buckles, snaps, Velcro, or rip cords. Integrated weight pockets are designed to hold the weight securely yet still allow for quick release to dump weights in an emergency. Simply pull the handle and the weight pocket falls clear.

Why would a diver prefer a weight integrated BCD rather than a weight belt? Safety, comfort and trim. Many divers find it easier to dump weight from a weight integrated BCD. Rather than search for the buckle on the weight belt, simply pull one or both handles - conveniently located on your hip where it is difficult for gear to get in the way- and you can dump all or some of the weight. Dumping only one pocket gets rid of half the weight. This can help create positive buoyancy without as much risk of an uncontrolled ascent.
Many divers find weight integrated BCD's more comfortable since the weights are in the BCD and away from direct contact with your body, unlike a weight belt which rests directly on the hips. Also, in a weight integrated BCD, there's less back strain. That's because the  pull of the weight is distributed all along the BCD rather than concentrated in one area like a weight belt. This is especially true when using a lot of weight. Now, what about "trim??

Assume the position

"Trim" refers to distributing the proper amount of dive weight along your body. This adjusts your body position in the water - in most cases, that means horizontal and face down. A properly trimmed diver swims with less effort and finds it easier to avoid stirring up the bottom (or kicking fragile coral!) There are several ways to adjust your trim.

In a weight integrated BCD, the weights are low and forward on the BCD which helps to roll the diver towards a horizontal face-down position. Another way to adjust your trim is to put some of your weight in "trim pockets". The addition of trim pockets is a feature of most high end BCD’s. By locating the pockets fairly high up on the BCD, a larger moment arm is created. This allows a smaller amount of weight to have a larger effect. Typically, moving one-quarter to one-third of your total weight from the main pockets to the trim pockets will be more than enough to move a feet-heavy diver to a more horizontal position. The higher up towards the shoulders the trim pockets are, the less weight will be needed to get a desired effect. Just remember that trim pockets are usually "non-dumpable" - you can't quickly release this weight in an emergency. So be sure that you can be positively buoyant with the trim pocket weight still in the BCD.

Location, Location, Location


Ok, it's not real estate but the location of your BCD is important for diver comfort. An average starting point for how high to mount the BCD on the cylinder is this: put the top of the hard pack level with the top of the tank bell. You can adjust it up or down to effect your trim and to avoid bonking your head on the regulator first stage when attempting to look up. To help you get the right position, many BCD’s have an adjustment strap/carrying handle. Drop this strap over the cylinder valve as you put your BCD on the cylinder, and adjust it so that your BCD hangs in just the right place for you while you fasten the tank strap without having to simultaneously hold the BCD in place. This is especially nice with weight integrated BCD’s which can be heavy when the weights are still in the pockets.

Ring it up
What do you want to do with your diving? Does the BCD you're considering have all the features you need to support your diving goals? Since diving is an equipment intensive sport, you'll need places to put gear. Check the pockets. Are there enough of them, are they big enough (with the BCD inflated), and can you reach them in the water? Some BCDs even have grommets built in for attaching a dive knife. Check out the D-rings. Some BCD’s have only one while others have five or six or more. Typically, you’ll find D rings located on the shoulders and the bottom edge of the BCD. Rings can be plastic, carbon, and stainless - make sure they’ll last and hold your gear securely. A nice touch on some of the stainless D-rings is a "pre-bent" position - the bottom half sticks out from the BCD a little bit, allowing for one-handed hook ups. And more is not always better since trying to use them all at the same time just creates a spider web of overlapping gear and lanyards.

Coming Up Next Month
Taking care of your investment or... "How to to clean and lovingly care for your BCD."