Ascent rate monitoring using air bubbles?

[G9]

I've been diving for 35 years. Only the last 5 with a computer. I am just a sport diver. I also was taught to ascend using the bubbles as reference. There was nothing else to use when I started as most of us dived for several years before we could afford dive watches (very expensive in the 70's).
Slower than the small bubbles always worked for me. We did not do safety deco stops at 3-6m. Only deco when required by the tables. I have never been (knowingly) bent, or had any other diving related health issues..

So, from a sample of 1, it is quite feasible to dive safely with limited equipment. You just have to be careful how you go about it.

 

[bkarate215]

How do you determine safety stop if rope has not been marked?

 

[peterthewolf]

Great topic! I was cert'd in 1974 when 60 ft/minute was acceptable ascent. Took a long break and got back in the water about 5 years ago with new equipment and the revised more conservative deco/ascent data.

Although I have a good computer with digital depth, I dislike it. I'm very comfortable in the water with a good felt sense of things, but I *never* gauge my ascent well with a digital depth gauge, finding that I consistently accelerate or decelerate too much by the time the next foot of depth reads digitally, so if I use the digital as reference, my ascent is retard city. Just never can seem to 'feel' it on digital. So I just keep an analog gauge on the inside of my wrist and use that, with side reference to the computer which I hold in the same hand.

I used to love using my smallest bubbles; it really put my mind in a wonderful place of blending with the sea, especially in low vis, and it did seem to match 60 ft/min back then. I mean really the smallest bubbles, like 1mm or less. They do expand as we go up, so it meant keeping on smallest bubbles as I went up but that was common sense.

I'm not an ice diver or that techy, just love to dive. Has anyone experimented to find out how actually fast (really) tiny bubbles ascend? Now you all have me very curious to find out. If bubbles that are smaller than a millimeter really do clock at about 60 ft/minute ascent rate, and we stay fixated on that size group from bottom to surface, it could mean a nice ride up if we come up at *half* their speed. That could induce a hell of a meditation, because it would then appear visually (perceptually) that by letting them "slip" up at double our own actual speed of ascent, we would have gauge backup but (have sensation) of going down on ascent...not up! I can similarly recall getting vertigo early in my history, 85 feet deep with 20 vis, and absolutely swearing that those bubbles going down at a 45 angle should be going to the surface. So I followed them against every instinct I had yelling at me, down until I broke surface. One of those memories you treasure. But this is a serious inquiry on my part. I LOVED following my bubbles up years ago, and doing the current way (gauge only) is not as rich an adventure as it used to be.

I won't be in the water for a month or two while clearing something up so while this topic is fresh I won't get to time bubbles right away. All the more I'd love to hear from some of you who might be willing to time your (tiny) bubbles on your ascents. How fast really do they go? Have fun and let me know!

 

[Paladin]

There seems to be something some of you have been missing: When using your bubbles as a guide for your ascent rate, you are ascending slower than your slowest bubbles. That means that all your bubbles are leaving you behind as you ascend. If you are worried about bubble size or shape, then you must be ascending at the same speed as your bubbles, which is too fast. With a proper ascent rate, all your bubbles are ascending faster than you and are, then, gone in an instant.

 

[moregooder]

I picked this up at the UEOD school in Indian Head MD in 1980. to control are assent without a light or in zero vizz most people can listen to the air expanding in there sinus exiting out there ears. all the guys in my class could do it, to me it sounds like rice crispys in milk. I still us it today even with my modern day computer. I ascend slow enough so I can barley hear the bubbles and the assent line on my computer registers little to nothing at all

 

[Subcooled]

How do you determine safety stop if rope has not been marked?

Looking at my depth gauge.
Works even in sub 1m visibility.

 

[Subcooled]

If the tender drops it, it comes undone from your harness or somehow breaks or is cut does it matter how fast you come up?

The line is fastened with an ice screw and also held by the tender. It is wrapped around my body in such a way that it is very difficult to become undone. I also keep it in my hand for signalling reasons. There are thus two fixation points in both ends.

The rope has 30m maximum length and if I loose it I ascent to the ceiling and wait. The safety diver will commence a circular search along the ice using a rope twice as long.

During the day visibility is usually very good, it can be twenty feet or even more, as ice keeps the murky surface waters away. This depends on the bottom though. The hole in the ice is also like a lamp in the ceiling. Pretty hard not to see it

If the dive is done later than 4 pm during the winter, it is usually a night dive. Lights are usually highly visible, even if the hole in the ice is not. If a safety diver jumps in, his dive light can be seen far a way, just like my light(s).

Those, that can afford it, use double tanks, although taking into account the limited penetration, loss of air is nothing more than a mental hazard. If you don't panic, you are fine. One really can't run out of air, even with 0 bar (you still get a few breaths after you notice the increasing breathing resistance). It takes max 2 minutes to ascend from the deepest possible depth. The limited rope length really removes many risks. But it does not stop one from ascending too fast. With a 300 ft reel the dives would become seriously dangerous. That's why only tech/cave divers use reels under the ice.

 

[dry heat diver]

Some points worth mentioning:

I got training from a qualified instructor on how to do the dives
I got both ice diving experience and night diving experience before combining those
I got a good and experienced surface support (but occasionally no dive buddy in water)
I do a thorough mental rehealsal, part of which this thread is
I am also fully aware of the possible risks, which include at least

- lonely ascent with a free flowing regulator: issues with lung pressure/teeth cooling/breathing out/visibility and the accompanied difficulty at controlling ascent rate (can't see the computer). I have done it once from 30 feet, and it's not really a joy, but with a calm mind and moderate depth, very doable. The risks are real, though. Obviously, an octo helps here, esp. with double tanks.

- emergency ascent without air if there is a catastrophic equipment failure (risk of shallow water blackout, for example). Dangerous. Yes, doubles is the solution.

- the risk of cutting and loosing the line (though it's not a reel). There are standard operating procedures for this event, but it may still be pretty fatal. This is why we mark the entry point and divers with lights. They are not visible from far away, though.

- entanglement of the rope and/or diver. There's a safety diver and a rope tender at the surface, but still...

- having the line pull the regulator while one is turning his head is a potential source of anxiety. It feels weird "Where's my line? What's pulling my reg? How do I free it?". The obvious thought "I'll take the regulator out of my mouth and look at it" is the wrong solution.

- if there are several divers under the ice at the same time, the risk of making a big knot of the safety lines.

- and of course the risk of sending a distress signal by mistake and beeing pulled out at too great a speed.

So... not quite an easy entry level dive.

Just out of curiousity, what is the difference between fatal and pretty fatal?

 

[Subcooled]

Just out of curiousity, what is the difference between fatal and pretty fatal?

Beauty?

 

[Subcooled]

The bubbles rule is actually quite useful. Two weeks ago I had a free flow at 100ft, and with all the hassle of managing my own little jacuzzi, sharing air with buddy (have you ever tried to swim while sharing air? I can say two fins are fine, four is a little bit much), communicating, making sure not to blind the buddy and so on... I had not much time to stare at any gauges.

Looking at the bubbles was reaffirming, and we managed to do a nice slow ascent with only one audible ascent rate alarm (+33ft/min).

There's a video on the event on Youtube. Plenty of bubbles and some particles.
link: YouTube - Ice dive, free flow, GoPro HD

The sound is a little bit distorted, didn't have time to fix it. The video camera is on a Goodman handle, that's why the image shakes a lot at times.

ps. Size of the hole in ice: maybe 60ft or 90ft in diameter. Almost an open water dive. Down line. Visibility 90ft+. Plan: descend following the line, then practice with reel at the bottom.