The Cave Diving Website

Buoyancy Control

It is difficult to imagine two more dissimilar pieces of equipment than the typical recreational diver’s front-adjustable BC and the cave diver’s back plate, harness and wings. Nevertheless, more features from the cave diver’s harness have migrated to recreational BC design over the past ten years than from any other source.

Buoyancy Control

The typical recreational BC provides limited lift and a less-than-snug fit. This by itself makes it an unsuitable platform for supporting the weight of heavy double cylinders. There are other aspects of recreational BC design, however, that can cause potential trouble for cave divers. Among them:

Recreational BC
  • While recreational BCs typically have a number of D-rings to which divers can clip accessory equipment items, these tend to be located at the very front of the BC. Clipped here, items such as back-up lights and guideline reels would dangle several inches below the diver, where they could easily come in contact with the bottom, or become entangled in guidelines.
  • Many recreational divers clip items such as instrument consoles and alternate-air-source second stages to the D-rings located at the ends of their shoulder-length adjustment straps. Given the distance from the BC to the end of such straps, this creates an even more hazardous “dangly” situation than clipping items to D-rings mounted directly on the BC itself.
  • Recreational BCs tend to have very long large-diameter inflation hoses and little means of securing them. This creates yet another substantial entanglement hazard.
  • Recreational BCs also tend to lack critical mounting points for items such as canister lights and stage bottles — further rendering them unsuitable for cave diving.

The most common BC/harness configuration for cave diving consists of:

  • A stainless or aluminum back plate.
  • A single piece of continuous two-inch webbing.
  • D-rings at the shoulder and waist.
  • A two-inch crotch strap, with D-rings in the front (for attaching to Diver Propulsion Vehicles or “DPVs") and back (for reel storage).
  • An un-bungeed, wing-style air cell rated at 50 to 60 pounds of lift (less in Mexico, where divers use lightweight double aluminum 80s). The air cell’s inflation hose will be much shorter than those found on recreational BCs and be secured with a small piece of bungee cord to keep it from dangling or getting lost. There will be no “quick dump” valve at the shoulder, as these are both unnecessary and a potential source of failure.

In the past ten years, a number of cave diving harness features have migrated to recreational diving BCs. This has been both good and bad.

  • Most recreational BCs now come with true shoulder strap D-rings. These provide a better place for clipping off items such as consoles and alternate-air-source second stages, and result in much less in the way of “danglies” than clipping these items to the D-rings found at the end of the shoulder-length adjustment straps.
  • A number of BC manufacturers now offer “Tech” style single-tank BCs with wing-style air cells. Bear in mind that the reason wing-style air cells works so well for cave and technical divers is that their double cylinders hold the wings flat, making it easy to vent air. When used with single tanks, wing-style air cells tend to wrap up around the sides of the tanks, making it difficult to quicly vent air from the BC. Traditional recreational-style BCs do much better in this regard.

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