When choosing a buoyancy control device (BCD), one of the most important decisions to make is whether a back inflation or vest-style BCD will suit you better.
What is a Vest-Style BCD?
Vest-style BCDs are the more traditional of the two styles. The air cell (or the part of the BCD that inflates) wraps from the diver’s back around his sides and chest. An example is the Seascub Airone
What is a Back Inflation BCD?
A back inflation BCD features an air cell that inflates only along the back of the BCD. Usually, this air cell hangs behind the diver in the form of “wings.” An example of a back inflation BCD is the Scuba Pro Knighthawk.
How Do the Styles Compare?
• Floating on the surface
A vest-style BCD holds a diver in a vertical position when inflated on the surface, keeping his head well above the water. Back inflation styles tend to roll a diver face down on the surface, which can be frustrating for those accustomed to vest-style BCDs. This problem can be overcome by leaning back and floating on top of the BCD.
When fully inflated on the surface, vest-style BCDs can squeeze a diver’s chest and lungs in an uncomfortable way. In contrast, back inflation styles do not squeeze a diver’s torso, as they do not wrap around the diver’s chest. Many divers find back inflation BCDs more comfortable for this reason.
• Ease of Deflation
Vest-style BCDs are sometimes easier to deflate than back inflation models. The air cell in vest-style BCDs is held tightly against the diver by the BCD’s shoulder, chest, and waist straps. These straps squeeze against the air cell, and help to force air out when deflating.
Back inflation models may not deflate so easily. The air cell, or wing, hangs freely behind the diver, and no straps squeeze the wing to force air out when deflating. This means that air may take a longer time to exit a back inflation BCD, and increases the likelihood that air may become trapped in crevices or folds in the wings. Some equipment manufacturers wrap bungees or elastic bands around the air cells in back inflation BCDs, as in the Scuba Pro Knighthawk, which helps to squeeze the air out and somewhat eliminates the problem.
• Underwater Preformance
Many divers prefer back inflation BCDs because they naturally hold a diver in the ideal horizontal position. This reduces drag, which makes it easier for a diver to move through the water and may reduce air consumption rates.
In contrast, vest-style BCDs tend to force a diver into a slightly fins-down position, which is less efficient. Some BCD manufacturers attempt to fix this problem by placing weight pockets, called trim pockets, on the back shoulders or middle back of the BCD, as in the Scuba Pro Glide Pro. A diver distributes a small amount of weight into these pockets, which helps to correct the diver’s position by weighing his shoulders down.
As back inflation styles do not wrap around a diver’s torso, they allow a wider range of shoulder and arm motion underwater, which many divers find comfortable.
Some back inflation BCD models allow divers to detach the entire air cell from the BCD. This is an advantage, as a diver may want switch out the original air cell for one that provides more or less lift, depending upon the diver’s needs. For example, a diver might need less lift when diving with an aluminum 80 cu ft tank in salt water, and more lift when diving with a steel 130 cu ft tank in fresh water. Divers who dive in a wide variety of environments may find BCDs that allow them to switch out the air cell a huge advantage, as this eliminates the necessity of purchasing multiple BCDs.
Test-Dive Both BCD Styles Before Purchase
In this age of internet shopping, it is still a good idea to go to a retail store when purchasing a BCD. Divers should try on BCDs to ensure fit and comfort. Many dive retailers will allow divers to demo gear in a pool. Take advantage of this. Try out both vest-style and back inflation BCDs. Practice swimming, ascending, descending, and floating on the surface. Remember, most commercially available BCDs are high quality and work well, so pick a BCD style that is comfortable and intuitive for you.