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One of the first things I want to change is how to describe the important elements Fundies students have picked up….One of the WORST descriptive terms used is a “Balanced Rig”…It is fine when used in discussionswith other GUE divers that have experienced what this means—but for everyone else, it sounds like rhetoric, and falls far short of explaining the real issues.
1. Balanced Rig …I began class using a lp 120 and an 18 pound lift wing. Normally I use big monster freedive fins, swim easily at 2 mph or faster, and can stop and hover at what I had thought was no effort J I learned this was NOTa balanced rig….not because I could not swim up the tank from the bottom if the wing failed—in fact, very little gas was in the wing at the bottom on a dive. Balance was really about balance in this case. While it is cool that a bp/wing diver can switch from double tank set up to single tank, by just removing the doubles wing, and adding an STA and the singles wing..this removes a lot of side to side balance. First, the STA which attaches the tank to the backplate, adds vertical profile to how high the tank extends above your back. Think walking on stilts, versus walking on sneakers. Second, if the single tank is a really big single tank, like my lp 120, then the vertical rise—the weight quite far from your back, gets even higher, and ends up pulling you left or right with more leverage---the tank wants to roll to be at the lowest point in the center of gravity—the bottom. This tends to pull you to one side or the other. Now choice of wing can mitigate this quite a bit…..worst would be the 18 pound wing I liked, for it’s lack of drag in the water, great when trying to keep up with bottlenose dolphins. For stability when stopped ( when your body is not acting like an airplane wingfrom the swim speed) , it is terrible because it has no “pontoon effect”, and because it is a horseshoe design, so air can’t quickly run from one side to the other always. The 30 pound Halcyon wings on the other hand, DO have a “pontoon effect”…they spread out at the sides like pontoons, and the small amount of air you have in them at the bottom, makes the tank become a much lower center of gravity, and you feel left to right stable, as if aided by pontoons. If you were using doubles, the sta is absent, so the tanks are quite a bit closer to your back—really close, so center of gravity is very low for the tanks—very little pull possible to left or right---AND, the 40 or 50 pound lift wings run quite a bit further to each side of the diver, causing the pontoons to be almost twice as far apart---spectacular stability. So when you stop with doubles on , and want to hover motionless, and effortlessly….there is nothing to fight..unlike the setup I had been using. Maybe no big deal if you will only stop for 10 seconds….but imagine in a shipwreck or cave for 10 to 20 minutes, or on a spectacular coral reef, where your buddy was photographing a rare nudibranch,and there are NO handholds or places you dare touch---perfect trim and buoyancy, plus balanced rig as just explained, and you can hang 4 inches above the coral, not have to even move your feet, and stare effortlessly at the Nudibranch. Anyway, this is what I am taking away as the real meaning of balanced rig. It also means you need to be able to swim it up from the bottom with a total wing and suit failure, but this is more common sense…Some guy using massively heavy steel tanks and tank weights, to get neutral on the surface with a 7 mil wetsuit, who then dives to 150 feet, could easily weigh 35 pounds at depth ---if his wing fails, he can not swim this up. If some of his weight was on a weightbelt, he might ditch 15 pounds, but may still have so much negative weight left that he could still not effectively fight the weight to make it to shallow water and more wetsuit buoyancy. So this guy MAY have carried a redundant liftdevice like an SMB he could inflate at depth, but this is a hopelessly convoluted way to solve the problem, with it’s own potential to create major problems at the worst possible time. The double 80s are almost neutral, so at 150 feet, even if the big wing failed, the diver could swim them up.
The doubles diver desiring a “balanced rig” would not use a thick wet suit for a deep dive, knowing that it would cause a massive shift in buoyancy at depth—requiring the wings to hold a lot of gas. This is drysuit territory for balance. If a thick wetsuit HAD TO BE USED for the deep dive, then it would require ditchable weight, but once you were in shallow water, you would be too positive to hold your stop at even 30 feet. So now you would be looking at the redundant lift solution, which perhaps should get it’s own thread to point out all the dangers of using this approach.
I am going to add several more descriptive term suggestions, where they will make much more sense than how presently used…..but this post is too long already… J
1. Balanced Rig …I began class using a lp 120 and an 18 pound lift wing. Normally I use big monster freedive fins, swim easily at 2 mph or faster, and can stop and hover at what I had thought was no effort J I learned this was NOTa balanced rig….not because I could not swim up the tank from the bottom if the wing failed—in fact, very little gas was in the wing at the bottom on a dive. Balance was really about balance in this case. While it is cool that a bp/wing diver can switch from double tank set up to single tank, by just removing the doubles wing, and adding an STA and the singles wing..this removes a lot of side to side balance. First, the STA which attaches the tank to the backplate, adds vertical profile to how high the tank extends above your back. Think walking on stilts, versus walking on sneakers. Second, if the single tank is a really big single tank, like my lp 120, then the vertical rise—the weight quite far from your back, gets even higher, and ends up pulling you left or right with more leverage---the tank wants to roll to be at the lowest point in the center of gravity—the bottom. This tends to pull you to one side or the other. Now choice of wing can mitigate this quite a bit…..worst would be the 18 pound wing I liked, for it’s lack of drag in the water, great when trying to keep up with bottlenose dolphins. For stability when stopped ( when your body is not acting like an airplane wingfrom the swim speed) , it is terrible because it has no “pontoon effect”, and because it is a horseshoe design, so air can’t quickly run from one side to the other always. The 30 pound Halcyon wings on the other hand, DO have a “pontoon effect”…they spread out at the sides like pontoons, and the small amount of air you have in them at the bottom, makes the tank become a much lower center of gravity, and you feel left to right stable, as if aided by pontoons. If you were using doubles, the sta is absent, so the tanks are quite a bit closer to your back—really close, so center of gravity is very low for the tanks—very little pull possible to left or right---AND, the 40 or 50 pound lift wings run quite a bit further to each side of the diver, causing the pontoons to be almost twice as far apart---spectacular stability. So when you stop with doubles on , and want to hover motionless, and effortlessly….there is nothing to fight..unlike the setup I had been using. Maybe no big deal if you will only stop for 10 seconds….but imagine in a shipwreck or cave for 10 to 20 minutes, or on a spectacular coral reef, where your buddy was photographing a rare nudibranch,and there are NO handholds or places you dare touch---perfect trim and buoyancy, plus balanced rig as just explained, and you can hang 4 inches above the coral, not have to even move your feet, and stare effortlessly at the Nudibranch. Anyway, this is what I am taking away as the real meaning of balanced rig. It also means you need to be able to swim it up from the bottom with a total wing and suit failure, but this is more common sense…Some guy using massively heavy steel tanks and tank weights, to get neutral on the surface with a 7 mil wetsuit, who then dives to 150 feet, could easily weigh 35 pounds at depth ---if his wing fails, he can not swim this up. If some of his weight was on a weightbelt, he might ditch 15 pounds, but may still have so much negative weight left that he could still not effectively fight the weight to make it to shallow water and more wetsuit buoyancy. So this guy MAY have carried a redundant liftdevice like an SMB he could inflate at depth, but this is a hopelessly convoluted way to solve the problem, with it’s own potential to create major problems at the worst possible time. The double 80s are almost neutral, so at 150 feet, even if the big wing failed, the diver could swim them up.
The doubles diver desiring a “balanced rig” would not use a thick wet suit for a deep dive, knowing that it would cause a massive shift in buoyancy at depth—requiring the wings to hold a lot of gas. This is drysuit territory for balance. If a thick wetsuit HAD TO BE USED for the deep dive, then it would require ditchable weight, but once you were in shallow water, you would be too positive to hold your stop at even 30 feet. So now you would be looking at the redundant lift solution, which perhaps should get it’s own thread to point out all the dangers of using this approach.
I am going to add several more descriptive term suggestions, where they will make much more sense than how presently used…..but this post is too long already… J
...The other thing about the trim, the flat body is like an airplane wing as you glide along, and the wing of your body like this, helps to HOLD YOU in the exact depth you want---helps to prevent you dropping or ascending without desiring this. A diver half way to vertical, has little water resistance to prevent them from being pulled up or down--no body wing( not referring to bc here, just the hydrodynamics of a horizontal body with water passing over it). 
