Once a technique used exclusively by technical divers, Side-Mount diving today is widely becoming an intriguing avenue of recreational divers. Being versatile and comfortable, the rig utilizes a specially designed wing and harness system designed by companies such as Hollis, Dive Rite and Halcyon and they are just about ready to dive straight out of the box.
The ideology behind Side-Mount diving is simple…and skeletally has less of an impact on the divers back. Rather than wearing a tank or double tanks on the back, the tanks are slung on the side of the body using metal D rings, tightly streamlined under the arm so that the valves rest just below and in front of the armpit.
Using Gas Management technical dive procedures, air and other mixed breathing gas supply is carefully managed by swapping back and forth from tank to tank every 500 psi. Over the years, several technical agencies have developed a gas management strategy called the ‘rule of thirds’, wherein a diver uses one-third of each tank for the inbound portion of a dive, and reserves the second third for the return to base. The final third of each tank is left in reserve for the unlikely event of an emergency. By balancing tanks in this manner, a gas supply emergency can be managed independently, without assistance from another diver. Recreational agencies are now following closely with similar “rules” of gas managing for the diver and his buddy.
Divers of any level should still rehearse gas-sharing drills, but by diving Side Mount, in most cases, self-rescue can be achieved by switching to the unaffected cylinder or regulator. In Side-Mount diving, the tank valves are effortless to reach, less likely to become damaged by impact and the air gauge is easy to monitor as it is directly in line of site.
The first noted attempt at Side-Mount diving was conceived by British cave diver Mike Boon in the 1960s. Having recently ditched his old double hose regulator, he decided to use an unconventional tactic to explore a small cave Yorkshire. Slinging a tank on his side he was able to squeeze through tiny spaces that were previously thought to be impassable. The British took notice and set out to perfect the system for a number of needed uses.
The introduction of the technique in the United States came about when in the late 70s, an untrained recreational diver fatally forced himself into an impossibly narrow crevice in North Florida. Two very experienced cave divers using back-mounted cylinders were unable to recover the body so they fabricated a single cylinder rig with an old hose clamp and a belt. Holding the cylinder at his side, the recovery diver slid into the crack beside the lifeless diver, breaking him loose from the cave’s grasp. Seeing this configuration in action, a similar setup for exploration of smaller cave passages quickly became the subject of possibilities and Side-Mount cave exploration began to expand through North America. In 1995, Dive Rite released their Trans Pac system and the commercial viability of this style of diving became evident.
Side-Mount diving offers a distinct advantage for traveling divers. Leading designs such as the Dive Rite Nomad, The Razor harness, or Hollis SMS50 are among the lightest diving systems available. They pack small and weigh very little. With today’s airline baggage restrictions, every ounce saved helps! With minor adjustments to Side-Mount system tank bands and hardware, the harness supports all common diving configurations using one or two tanks. Side-Mount rigs accommodate any size tank. For the Technical set, they offer the advantage of supporting multiple stage tanks when back-mounted doubles are difficult at best to obtain in many destinations around the world.
Although Side-Mount rigging can be self-configured, the units available for sale incorporate many hard to duplicate features that grew out of years of developmental testing. The specially shaped wing concentrates lift around the diver’s hips to compensate for the lower center of gravity of the tanks, different than that of back mounted systems. The bottom attachment point of the tank clips to the harness on a rail on the diver’s butt. This clip creates a pivot point or center of balance on the diver’s body. The pivot point can be moved up or down to change the diver’s trim in the water or to accommodate the tank losing ballast due to air consumption. Once the system is properly balanced tanks ride parallel to the diver’s body with the valve tucked under and slightly in front of the armpit.
Proper placement of cylinders is the most important aspect of the Side-Mount system. If cylinders are out of trim, the diver will be faced with poor buoyancy and inefficient movement through the water. Poor configuration can lead to entanglement hazards and additional workload for the diver.
The tank valve is held in place by a safety clip and a bungee. Each tank is independent with its own regulator and short-hose pressure gauge. The left side regulator is equipped with a short low- pressure inflator hose. Dry suit divers will place an inflator hose on the right regulator as well. The hoses are carefully sized to fit the diver and the hose port locations. There is no set formula for the perfect hose length since each diver’s body, first stage port configuration, and safety preferences present different challenges. Many divers equip their second stages with swivels that assist with hose routing and jaw comfort. Many Side-Mount divers prefer a 7’ long hose for air sharing, if the unlikely event were to occur.
Even though the majority of problems as a Side-Mount diver are self-managed, it is very likely that there will be mixed teams that include other diving configurations. It is important that a diver wishing to dive Side-Mount get the training to handle emergencies with traditional recreational back mounted systems. A Side-Mount diver may have to give up a bottle entirely to a diver in need. Balance, control, and trim become a necessary management if this were to occur.
With that said, with the availability of commercial rigs such as the Hollis SMS series and Dive Rite Nomad line, training agencies saw that Side-Mount classes could be offered to a wider audience, not just cave divers. Now, most agencies from PADI to IANTD, offer a wide variety of training opportunities. Recreational, technical, specialty and exploration side-mount classes are available at a growing number of facilities around the world. Although some divers choose to adopt the new configuration without assistance, it is highly recommended to get formal training from an experienced instructor. It takes a trained set of eyes to assess comfort, fit, and practicality for new Side-Mount diver. Harnesses are extremely versatile for many body types, but custom fit and properly configured regulators maximize streamlining while trimming the diver in the ideal horizontal plane.
Side-Mount diving has transformed the way many divers approach their craft and exploration. The Side-Mount technique is a safe and logical alternative to back mounted rigs, whether single or doubles. In addition, the technique is exceptionally useful in diving environments such as caverns, caves, and wrecks. The technique also offers those that thought they could never dive again due to back issues a chance to continue their passion. For those that still want to dive traditional back mounted rigs and the Self Reliant diver that ventures off on their own, or divers that just need more air, a diver configured with small, lightweight cylinders can add a measure of safety as a redundant air system.
Side-Mount diving is an easy option that offers flexibility and allows you to take your buoyancy and trim skills to the next level and for some to the world of technical diving.