Trim Fits! Steel120, I've done the buoyancy test.. What do the results mean?????

[ryantaylor0@yahoo.com]

i made a mistake when I started diving. I went out and bought a bunch of gear that I had no knoledge about, now I would like to make it work. So here's my setup and problem. Scubapro Knighthawk BC and Steel 120 tank. It dosent matter if I have no weight on at all, I still sink like a rock and constantly have to fight the tendency to be flipped onto my back. This is with no exposure suit, just shorts and a shirt. It gets even worse when I add a wetsuit because it's boyant and the tank is heavy so it tries even harder to put me in the ol' stranded turtle position. What's the cure? Folks that dive with steel 120s.... How do you do it? There is obviously a way to do this successfully, I just have no idea what it is. It also concerns me that with no weight and still being negative, there is no ditch your weight safety blanket... Thoughts? I know the right answer is probaly to trade for a al80 but I want to know if there is another option before I jump. Please help!!

 

[TSandM]

A lot depends on the brand of 120 that you have. PST 120s are only a pound or so negative when empty. Fabers are -7, and Heifers are an amazing -17. If you are diving Faber or Heiser tanks, and no exposure protection at all, you are VERY negative, even with the tank empty. This will result in a lot of air in your BC and a lot of instability, and since you will be carrying no other weight at all, all your tendency to sink is on your back, which means your technique has to be quite precise to prevent turtling.

Although wearing a wetsuit should improve the situation underwater, it won't help on descent, because the wetsuit is wrapped around your body, and therefore all its lift is along the long axis of your torso. The tank is still heading powerfully downward behind you.

This situation IS amenable to remedy, but only assuming you are either using the PST tanks with no exposure protection, or the PST or Faber tanks with a wetsuit. I don't think it would be easy at all to deal with the Heisers.

To fix the problem of falling on your back, you have to provide some kind of force that counters the desire of the tank to sink behind you. Bending your knees on descent will put your fins behind you, and they really resist descending. This will tend to rotate you into a horizontal position, and once you are there, all you have to be able to do to prevent rolling over is to learn to balance the tank above you.

 

[TotDoc]

As usual, my response is "Yeah, what TSandM said." ..sigh...one of these days I will get to beat you on one of these posts! one of these days!

But as someone who dives steel 120's, I can tell you that diving them without exposure protection gets interesting. Most steel tanks, especially in fresh water without exposure protection, will turn you into a real dirt dart. Keeping your knees bent and your fins out slightly and behind you (in the frog kick position) will help give you some lateral stability to prevent turtling, but it's really important not to do any sudden movements that will get those tanks trying to roll you. A lot of this will come with experience.

Your concern about no ditchable weight is reasonable...kind of. Keep in mind that if you are at the surface and can't establish positive buoyancy, you can always kick off the BC and let it sink. Better to buy new gear than to drown. At the surface is the only place that lack of ditchable weight should be of a concern, just so long as you are capable of swimming up your rig with no air in your BC. Worst case scenario is you have a wing failure at the start of your dive when you have all the weight from a full tank of gas on your back, so that is when you want to try this out - at the beginning of your dive. You really don't want to be ditching weight from depth, but you do want to make sure you can get BACK to the surface with whatever you bring down with you.

If you can't, you have a few options
1) wear exposure protection so that you have enough extra buoyancy to swim up your kit
2) bring redundant buoyancy like a lift bag or depth deployable safety sausage
or 3) replace the tank with something more manageable for you

All this stuff gets easier with practice, my friend - but if it so happens that you are diving an xs scuba (Worthington) x7 HP120 tank and you decide to go with option 3, I'd be happy to take it off your hands so I can make another double set!

Good luck!