"I've never dived a double hose reg. Could you explain that one? Are you vertical in the water and want the reg lower than the mouthpiece? Diving horizontal gives you more position control (for movement in all directions). Of course that puts the mouthpiece below the reg but that's the way that animal works...they work better upside down? I'm also not much of a photographer but I can look any direction I want while wearing my valves where I can reach them."
I was not going to post in this thread anymore because it has become "strained" but I want to answer your question who ever it was who asked it--lol.
If you have an older Scuba Text from the 60s you will see that there are recommended tank positions. The reason that double hose divers wear their tanks "low" (normal) when compared to "tech" divers is for positioning of the main diaphram. The double hose regulator has the main sense diaphram in that large can that is attached to the tank valve. This differs from a single hose which has the main sense diaphram at the mouth piece. Wearing the tank such that the diaphram is kept closer to the center of the chest decreases the pressure difference between the diaphram and the center of the lungs. Since most divers, even swimming level/horozontal are actually swimming sliightly at an upward angle this also helps to lower the position of the diaphram relative to the center of the lungs. Properly positioning the regulator greatly reduces breathing effort. I can, if I were to ever need to, reach around with my hand, lift the tank, and reach the valve BUT I never have had to with a single tank OW dive. In most cases, asssuming some one is not grossly overweighted they should be able to maintain a position on the surface by swimming. I think I droppped a weight belt once when I was about 14 in the pre BC era, I got to far from the boat and the dive club dive master had moved the boat or something and I was getting awfully tired--lol.
Back to the double hose thing and position of the tank. I was always taught to wear the tank with the valve centered between the shoulder blades. I am sure, to some degree this training comes from earlier divers. I tend to be conservative and not jump on every new fad. A good Royal Aqua-Master double hose, properly tuned and set up can accomplish any dive a modern a single hose could and often perform better. Obviously for cave diving or serious wreck diving a long hose and doubles and DIR type configurations with isolated manifolds that can be manipulated during the dive are solid/smart thinking. The last tech type dive I did this season I was running dual single hoses on a single aluminum 80 in a DIRish configuration because my buddy was not familiar enough with a double hose so I did not want to cause him any concern or confusion. Low vizand cold water complicated the dive as well.
I touched on it but the thing about being horozontal in the water, that is the way we were taught before there were BCs. Like I mentioned, when horozontal a diver is actually going to be slightly head high and slightly feet low if well balanced. You may not think so but observe this on your own. Yeah, some people have legs or fins or other reasons their feet float up and you see them looking for ankle weights. The human body just seems to like keeping the head higher than the feet--lol--even if we are talking only a very few inches difference. Most double hose divers swim and rig for a horozontal position. Without a BC, using the body as an aquaplane helps to compensate for being slightly negative, forward speed will produce some slight lift. Yeah, yeah, that may not work so well in a heavy/more complex DIR outfit but it does when all you have is a tank and a regulator. Hope this explanation helps you understand why different tank positions are appropriate for different styles of diving.
Please everyone have a wonderful Thanksgiving, G'day.
N
Good ol Nemrod, always the gentleman
