Buoyancy Tips...

[Divin'Papaw]

The drysuit can be used as a redundant, but should not be used as a primary buoyancy compensator. Add or remove gas to the drysuit to prevent squeeze and to retain loft in your underwear; use the BC for buoyancy compensation. In other words, drysuit inflation is a comfort issue, and the BC is used to compensate for buoyancy changes due to suit compression and/or drysuit inflation. If you'll think of their relationship that way, life will be easier.
Buy a steel tank and jettison some of that weight
Rick

But in my PADI course we were taught ......

I found out pretty quickly how hard it is to adequately control buoyancy with just the drysuit like PADI and others (see The Zen of Diving Drysuits in Issue 13 (Oct '06) of X-Ray mag) teach. Once I started using just enough air to counteract suit squeeze and then the BC for buoyancy, I found it much easier to control my buoyancy in a drysuit. Others prefer the suit only option, but it just didn't work very well for me.

 

[Rick Murchison]

But in my PADI course we were taught ......

I found out pretty quickly how hard it is to adequately control buoyancy with just the drysuit like PADI and others (see The Zen of Diving Drysuits in Issue 13 (Oct '06) of X-Ray mag) teach. Once I started using just enough air to counteract suit squeeze and then the BC for buoyancy, I found it much easier to control my buoyancy in a drysuit. Others prefer the suit only option, but it just didn't work very well for me.

I don't wear a drysuit because I'm unhappy with my BC... I wear one to stay warm
Rick

 

[littlewaywelt]

You don't want to be head down, but you don't want to be feet down, for sure. The major reasons lie in the physics of the kick. If your feet are pointing down, then, when you kick, two things happen: You're propelled upwards, and the water from your fins goes DOWNWARDS into the silt, creating a dust cloud behind you.

Kicking yourself upwards with every fin stroke makes you have to dive negative, so you won't constantly head shallower. Thus, any time you are not kicking, you are sinking, which makes it impossible to hover to look at any thing.

Being horizontal means you can dive neutral, hover when you want to, and keep your fin "exhaust" out of the bottom.

If your head is banging into your first stage, you may have your tank up a little too high.

thanks for the tips.

So if I wasn't finning to maintain my depth (up or down), then I was neutrally bouyant?
When descending from the boat, and not using an anchor line what's the common or desired orientation? Still level? I found I was sinking in a knees down orientation.

 

[thomjinx]

One key element about being overweighted is that you must use more air in your BC. The more air in your BC, the greater the changes in your bouyancy as you ascend and descend. So when you are overweighted, your bouyancy control is much more 'twitchy' and difficult to control.

 

[TSandM]

When descending from the boat, and not using an anchor line what's the common or desired orientation? Still level? I found I was sinking in a knees down orientation.

People descend in different orientations. I prefer descending in a horizontal position, because it allows me to look below me but also makes it easy to keep track of my teammates, and if I need to look up, it requires only a small change in posture to do it.

If you are descending in a knees-down position, there are several possible reasons. A big one is that you are carrying significant weight and have it all too low on your body. People who dive with twenty or more pounds in integrated weight pouches at the waist are just about condemned to a knees-down position in the water.

Another possibility is that you are breaking at the hips -- In other words, your hip joints are flexed and your knees are below the rest of your body. That one's easy to fix.

A third one is that you are simply putting yourself in that position, as you begin your descend feet down, and not correcting it.

If you want to descend in a horizontal position (and as I said, not everybody does, although I think there are significant advantages to doing so) then you need your weights properly distributed and to get your body into a pretty horizontal position. For me, it feels as though I slide downward and backwards, and my fins catch the water and tilt me into the horizontal position. It did take a while to learn to do this, though!

 

[Rick Murchison]

When descending from the boat, and not using an anchor line what's the common or desired orientation? Still level? I found I was sinking in a knees down orientation.

Descents depend on what you're doing...
Spearfishing? Generally a headlong dash for the bottom (or planned depth) to get the first shot.
Recreating in clear water? Usually as TS&M describes, but sometimes I just sorta flop into the water and take whatever position happens and try not to fall asleep on the way down.
Vis less than 6 feet? Feet first! I dang sure don't want to find anything with my face!
Rick

 

[3-Ring Octopus]

On drysuits and bouyancy: You shouldn't need to add much more air to become neutral than you do to relieve squeeze if you're properly weighted. The two exceptions are: 1) you're overweighted significantly to provide extra warmth in VERY cold water 2) you're deep. (100'+, IME) Otherwise, my suit IS my BC..and controlling bouyancy is more precise in my experience, because I can "feel" the entire bubble. YMMV.

On descent: I like to descend horizontally, like TSandM said. However, vis hasnt ever really made any difference in my descent style. I'm not usually dropping like a rock anyway...so I've always got time to throw an arm out if I see something in low vis. (Or even better...I drop an arm below me if the vis is THAT bad and can "feel" my way around..) Again..YMMV.

Cheers,
Austin

 

[Divin'Papaw]

On drysuits and bouyancy: You shouldn't need to add much more air to become neutral than you do to relieve squeeze if you're properly weighted. The two exceptions are: 1) you're overweighted significantly to provide extra warmth in VERY cold water 2) you're deep. (100'+, IME) Otherwise, my suit IS my BC..and controlling bouyancy is more precise in my experience, because I can "feel" the entire bubble. YMMV.

On descent: I like to descend horizontally, like TSandM said. However, vis hasnt ever really made any difference in my descent style. I'm not usually dropping like a rock anyway...so I've always got time to throw an arm out if I see something in low vis. (Or even better...I drop an arm below me if the vis is THAT bad and can "feel" my way around..) Again..YMMV.

Cheers,
Austin

What size tank? I dive an HP100, which isn't huge but is different enough from an AL80 to cause me issues if all I used was the drysuit at the beginning of the dive. It requires just too much air in the suit. Also, the suit doesn't vent quickly enough nor is the location of the bubble as controllable as with my BP/W. I use the suit to offset suit squeeze, in essence keeping it close to neutral. I use my wing to offset the weight of the rig. Having the air bubble that is floating the rig right on my back surrounding the tank provides a significant amount of control. I found that using the suit to do it all significantly reduced my ability to fine tune buoyancy.

 

[Rick Murchison]

On drysuits and bouyancy: You shouldn't need to add much more air to become neutral than you do to relieve squeeze if you're properly weighted.

... my 7 mil drysuit ...

Want to revisit that one?
Rick

 

[littlewaywelt]

One key element about being overweighted is that you must use more air in your BC. The more air in your BC, the greater the changes in your bouyancy as you ascend and descend. So when you are overweighted, your bouyancy control is much more 'twitchy' and difficult to control.

This has been my weighting thus far.
8lbs in the pool classes
10 lbs in the ocean no wet suit
12 lbs with a shorty in the ocean
I'm about 165lbs with low bodyfat.
In the ocean I had almost no air in my bc or so I thought. I dumped it all going down and then just 2 shots of less than 1 sec/shot seemed to keep me in a close to hover situation.

The dive boat ppl told me that it's common for schools to overweight their students. Does it sound like I'm overweighting? I didn't seem to have much trouble maintaining depth location and my cpu log seemed to bear that out, although since it only samples every 30 seconds I suppose I might be missing something.

With regard to lung volume changing buoyancy. Occassionally, if I saw myself getting too close to the coral, I'd take a breath and hold it for a second or two (not longer than that) until I rose a little and then breathe normally. Is that considered "holding one's breath" as a no-no? ...was generally around 70-50ft when I'd do that. Would I have been better off using the bc? I was def nervous about adding too much air to the thing and shooting up.


Sorry for the rambling q's.