I supposed the first skill a technical diver has to learn is how to dive in doubles. I get that opportunity this weekend. So, even though I had a brief taste of some technical dive training when we did the dry suit and deep diver specialties courses, this will be my first real technical dive training.
The dry suit class was basically just a recreational class except we were taught to use our suits tech style instead of rec style. That means we used both the dry suit and the BCD for buoyancy control instead of just the dry suit like you normally would in a pure recreational course. For the deep diver course, we practiced gas switching using a stage bottle hung at 20 feet (in standard recreational deep training the hanging bottle is just a bailout bottle in case you run out of air during your "safety stop"). We also did one dive using the tech diver rule of thirds to signal the end of our dive and then the final dive was done using run times and staged decompression stops (even though we were well within the no-deco limits). So these weren't really anything special: any recreational diver can do that.
This weekend, however, I'll be learning how to use a technical diving rig. This is a big departure from the standard recreational diving gear. In addition to having two tanks, the whole rig is different from the standard rec set up.
The first task is learning how to set up the gear, which we did this week. This started with connecting the two LP95 tanks together with an isolation manifold and tank bands. The tank bands are just metal bands that hold the tanks together and onto the rest of the rig. The tank valves and isolation manifold allow you to connect two regulators (one to each tank) and access the gas in both tanks from either regulator. Normally both regulators are drawing from both tanks. In the event of a regulator failure, you can turn off the valve to that regulator, but you are still getting air from both tanks using the remaining regulator. If, for some reason, you need to turn off the air from one of the tanks, you can close the isolation valve. Then each tank/regulator acts independently. I don't know know what situation that would be useful for, but I'm sure I'll learn that soon enough.
The next thing we did was set up the regulators. We used two Aeris AT400 Pro regs with DIN connections. The manifold is a Thermo 300 Bar DIN. You use DIN in tech diving because it's less likely to leak, especially if the connection gets knocked into something. Both regulators are high quality primary regulators. You don't use a standard octo in technical diving because the environment you are diving in requires that your backup be just as reliable as your primary. However, the second stage we designated as primary gets a seven foot hose instead of the standard hose. This regulator is connected to the right post and the hose routed down between you and your wing, then up across your chest and around your neck, left to right, and then into your mouth. The other regulator is mounted on the left post with the second stage hose going to the right and over your right shoulder. The second stage is attached to a regulator necklace. This holds your backup right below your chin, so in an out of gas emergency, you can hand off your long hose to your buddy and quickly pick up your backup. Both regulators get break-away clips. Basically this is just a gate clip attached to the hose using an o-ring and zip tie. If you have the regulator clipped off on a D-ring and you need it in an emergency, you can easily pull it off breaking the o-ring instead of fumbling with the clip.
Next we set up the harness on the backplate. The backplate is just a metal plate with holes and slots designed for routing nylon webbing to create the harness. We started with seven feet of two inch webbing which we routed through the various slots. In the process of doing this we added two D-rings to each shoulder strap and one to each waist strap. We added a metal belt buckle to connect the two waist straps and a plastic weight belt on the right side waist strap to hold the flashlight cannister (that I don't have yet). We finished it off by creating a crotch strap with a D-ring in the front and back, so you end up with four D-rings on your chest (two about shoulder level and two about three or four inches lower) and four on your waist (front, back, and each side).
Then we put it all together to see how it fit. Lay down the tanks with the tank band bolts pointing up. Put the wing on next with the bolts going through the appropriate grommets in the wing. Then put the backplate on the bolts and secure each bolt with a washer and wingnut. Next connect the regulators to the tank valves (long hose on right post and short hose on the left post). The LP hoses for the wing inflator and the dry suit inflator are connected to different regulators so you don't have all of your buoyancy on one regulator (redundancy). In our case, we are putting the wing inflator hose on the left post and the dry suit inflator hose on the right post. Additionally, the left post gets the SPG (with breakaway clip).
One other note. We removed all the hose boots. The reason for this is so we can see all the connections to look for cracks and leaks.
Comparing this set up to my recreational rig, it's simultaneously simpler and more complex. More complex because you have two tanks with an isolation manifold that you need to learn how to use. Simpler because there is not much to it. There is no integrated weight system, no fancy BCD inflation system, no adjustable tank strap that you have to set at the correct height every time you mount a tank. The tech rig is designed to be simple, redundant, and streamlined. Looking at a properly equipped technical diver, you will see that he's much more streamlined, in spite of the double tanks, larger wings, and other gear, than the average recreational diver. Recreational divers aren't general taught about streamlining, so they tend to jump in the water with all kinds of things hanging off off them. I know because I was one of them.
So the first think I learned from technical diving, streamlining my rig, will be an immediate benefit to my recreational diving.
This weekend we'll be headed for Gilboa Quarry for my first dive in doubles. This could be called my second dive weekend in the transition to tech course, since we started working on thinking like a tech diver during our dry suit and deep diver certification dives last month. In spite of the cold, it should be a good time.
