Looking or tips on redistributing weight with a back-inflated BC.

My wife has a back-inflated BC with integrated weights, and she seems to have some difficulty assuming a vertical position underwater, which makes it harder for her to descend comfortably on a drift dive. We are wondering what is the best way to correct this. We have not seen anyone using ankle weights with a wetsuit, and it sounds like having such weights should make it somewhat harder for her to kick, and possibly cause her to get tired and use up her air much faster. We are considering trim weights, but from what I heard, those are typically used to address the opposite problem (or are they?). Oddly enough, she seems to have more control with one pound less weight, but that in turn makes it difficult for her to perform safety stop with an empty tank. A trim weight clipped at the very bottom of the tank, perhaps? It sounds like it could easily slip off. Perhaps lower back weights, or hip weights?

empty all the air in the BC, thus allowing her to descent as if she is not wearing one. Unless it is the negative buoyancy of the tank that is throwing her off balance, but that would be the case regardless of the type of BS she is wearing.

Try lowering the tank in the BC. That shifts some weight lower on your body. You can also connect two ankle weights around the bottom of the tank, using the tank boot to hold it in place (but that is no guarantee they will stay there).

Strange. My weighting is such that it promotes a static horizontal position. If I choose to, I can descend head-up/feet-down, head-down/feet-up, on my belly horizontally (prone), or on my back horizontally (supine). In order to descend in any particular position, it's all about creating balance with one's arms/legs/head.

Redistributing ballast, using ankle weights, or shifting the tank relative to the BCD may make it easier to attain a vertical position during the descent phase...but what about the rest of the dive? For the way I like to dive, that would be making too costly of a compromise -- I spend most of my dives hovering in a horizontal position.

Why exactly does your wife need to be in a vertical position in order to descend?
Novices are taught to descend vertically because they lack buoyancy control and can kick towards the surface to slow their descent if they are slow to equalize their ears. Perhaps a better approach is for her to work on her buoyancy control skills and try to descend horizontally. First pre-pressurize her ears at the surface with the Valsalva maneuver. Next, empty only enough air from her BCD at the surface so that she's neutrally buoyant...then exhale slowly and deeply. She should begin to descend slowly. Then, stop at a depth of 2-3 fsw by adding a small tap of the BCD power inflater and equalize her ears. Achieve neutral buoyancy. Then repeat the process with another stop 2-3 feet deeper. And so on.

My dive buddies and I all descend horizontally. We all dive drysuits, but we'd be descending in a similar fashion even if we wore wetsuits. It's easier to see what's below us if we're horizontal in the water. We can also adjust our position relative to each other easier during the descent. YMMV.

I'm a little confused about the problem, from reading the original post. She is having difficulty assuming a vertical position, but tends to be feet up? So it's a feet-down vertical position she can't assume? I don't use that position for anything but the first three feet of any descent, drift dive or not. By three feet underwater, I'm horizontal, so I can see both in front of me and what's below me.

If she is having problems with being feet-up when she tries to be horizontal, I agree that dropping the tank might help, as will putting her weights as low as possible.

If her BC has trim pockets near the shoulder blades like mine does, you can add or remove weights there as needed. If your wife's feet keep floating up, I'd say don't use the trim pockets and move the weights down. Maybe get a weight belt for just a couple pounds.

I agree with the others that she should not want to be vertical much anyway. Once she gets underwater, she should be getting vertical.

TSandM:

I'm a little confused about the problem, from reading the original post. She is having difficulty assuming a vertical position, but tends to be feet up? So it's a feet-down vertical position she can't assume? I don't use that position for anything but the first three feet of any descent, drift dive or not. By three feet underwater, I'm horizontal, so I can see both in front of me and what's below me.

If she is having problems with being feet-up when she tries to be horizontal, I agree that dropping the tank might help, as will putting her weights as low as possible.

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Good point. My assumption was that she had light feet, and could not get horizontal either, not just vertical.

Thank you all for your suggestions. Yes, the problem is that she has some difficulty equalizing especially at the beginning, and she cannot just dump the air, for then she would be descending too fast. Also, she feels that being horizontal somehow makes the process more difficult and less comfortable. In addition, her feet are light possibly in part due to the neoprene socks she is using, and sometimes she ends up with her feet pulling up. We will try to lower her weights a little, and work on her buoyancy during descent so she can remain horizontal more comfortably.

how about first doing a proper weight check. "cannot dump air" and "then sescending too fast" point to over weight. If she use weight integrated BC, most weight will be on her upper body, making her feet light.

So do a proper weight check, then you know how much weight she need. Then try to distrubute them so that she can be comfortable staying at any position. Like other said, majority of the time, the diver should be horizontal.

janosik:

Thank you all for your suggestions. Yes, the problem is that she has some difficulty equalizing especially at the beginning, and she cannot just dump the air, for then she would be descending too fast.

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This seems to be a more general buoyancy control issue. There is no reason why a descent should be fast in a horizontal position. If anything, being horizontal would increase water resistance creating a slower, more controlled descent.

A preference for vertical descents tends to indicate that the diver places a high reliance on using their fins to creat upwards thrust to compensate for an underlying buoyancy control issue. i.e. the diver is not achieving neutral buoyancy and using fins to counteract their negative buoyancy.

Address this issue by first ensuring that her weighting is appropriate. Over-weighting often causes this type of problem with descents.

Secondly, work to develop more precise buoyancy control, thus eliminating the necessity to rely on the fins to arrest/control the descent.

janosik:

Also, she feels that being horizontal somehow makes the process more difficult and less comfortable.

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As mentioned, being horizontal relies on effective buoyancy. Without that buoyancy control, the diver is likely to find themselves struggling to achieve a comfortable descent. It truth, a horizontal descent should be painless and stress-free.... nothing more than a gentle drift downwards, which can be arrested with breath control.

With regards to drift diving, being in a vertical postion will only maximize the impact of water movement on the diver. Unless the divers' intention is to move with the current at the fastest possible rate (divers' would rarely have that goal), then horizontal positioning is by far more preferable as a drift diving technique.

janosik:

In addition, her feet are light possibly in part due to the neoprene socks she is using, and sometimes she ends up with her feet pulling up. We will try to lower her weights a little, and work on her buoyancy during descent so she can remain horizontal more comfortably.

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In addition to what others have contributed, I would recommend that your wife also investigated the relative buoyancy of her fins. It seems likely that she might have very 'floaty' fins. There are several models of fins available on the market that provide substantial negative buoyancy... and these would effectively counteract the lift provided by her booties.

Body positioning makes a difference when attaining good horizontal trim. Extending the arms forwards in a relaxed pose can shift some gravity forwards. Likewise, holding the legs upwards (bent at the knee) will reduce the 'lever' effect of having postive buoyancy in the legs. In addition, a weak posture can make horizontal trim very unstable and difficult to maintain comfortably. Creating a small arch in the back, with the mid-torso forwards and the shoulders/knees raised will make the position much more efficient (a bit like a skydivers' pose). This can take some practice though.


Overall, I would suggest some consideration of potential underlying problems; especially weighting, buoyancy control and trim. Without these as a foundation, no amount of trim weighting and tank shifting is going to have definitively beneficial effect.