Ascent rate monitoring using air bubbles?

[DevonDiver]

Look ma a tornado!!!

Seriously - with all your hypothetical problems (no buddy, no gauges, no line, no vis, whatever else you are throwing into the mix now...) who cares about ascent rate, just get back to the dang ice hole. Even 100fpm is better than dinking around much longer with all your broken gear and buddies.

Let's throw a Scorpion Fish sting into the pot also... after all, it's only hypothetical.

 

[giles45shop]

Wait, it's under the ice, so a rouge elephant seal would be a better choice

Seriously, as Rjack said, get the heck out. If you don't have enough experience to instictively "feel" how fast you are ascending without monitoring a computer (ear changes, time perception, counting in your head, etc.), you probably shouldn't be doing this dive. If your worried about two computers failing, just take a third one.

 

[dumpsterDiver]

I use very small bubbles frequently rather than stare at my computer. A 2 cm bubble (3/4") is very large. I look at tiny bubbles, the smallest bubbles that I can see. They are probably around 1 mm in diameter. They move slowly.

I take my hand, swish some bubbles down toward my waist, watch all the dime size bubbles float away and then locate the tiniest bubbles that are almost like a mist. These bubbles ascend slowly. I would guess maybe 20 feet per minute.

Often while solo diving, I follow the computer ascent rate up to around 50 feet for my deep stop, then I look around and often can see very tiny bubbles ascend around me. I hang out at 50 feet (my deep stop) for a couple of minutes and often the tiny bubbles are just catching up with me.

Also, if the water is crystal clear and there are zero particulate matter in the water (which I doubt) you should be able to shine the light up and judge the depth pretty well. When you get to 40 feet, stop for a minute, come up to what looks like 30 feet and hang for a little and then stop at 20 feet for a while.

If this stuff is not obvious, I would think that solo, deep diving under ice at night would present other more serious issues.

 

[Charlie99]

Also, if the water is crystal clear and there are zero particulate matter in the water (which I doubt)......

It's rare that the water is so crystal clean that there isn't something right in front of your face to use as a reference. Even relatively clear water will usually have tiny specks that you can see if you look just a foot or two in front of you.

Even when my computer is working normally, I heavily rely upon particulates for feedback on depth changes.

Use the particulates to set a very slow ascent rate, or a series of small moves upward with short stops. Your bubbles should be disappearing overhead, going up significantly faster than you.

It's not your instantaneous ascent rate that counts, but instead the ascent rate average over a few 10's of seconds. For decompression purposes, as series of 2' to 10' moves, and then a short stop will be the near equivalent of a continuous ascent.

 

[DevonDiver]

Wait, it's under the ice, so a rouge elephant seal would be a better choice

My point being, that it is no more ridiculous a scenario than a properly trained and equipped ice (overhead environment) diver finding themselves in a position where they have to resort to following bubbles in order to conduct a safe ascent.

i.e. It's a nonsense scenario.

 

[Subcooled]

If you stay negative, the line need not float up.

Hmm. I really need to try that. It's an interesting idea. A bit demanding perhaps... but I'll give it a try on my next dive. That, and observing the relative bubble speed will make the ascent a bit more interesting.

 

[Subcooled]

Comprehensive training then?

Commercial

It wasn't comprehensive. After the course I felt "ready" to do the dives. Now I have been learning a bit more from books and workshop proceedings etc. and the more I learn the more I have questions. I could ask questions about profiles (shallow part first to counteract deco problems related to vasoconstriction and extreme cold?) or about exercise after the dive (how much and what type, as keeping warm improves deco in extreme cold, but wrong type of workload may let bubbles into the arterial side and be very very bad). I am still doing the deepest part first profiles, but I feel I need to learn more. And it's interesting.

Nobody teached instrument-free diving either and although it should never happen, I'm sure I will one day make a dive where visual clues are helpful.

 

[Subcooled]

I would thank you all for your replies. I got a number of informative answers on the topic. With that information and more practice I hope to become a better diver. Having several ways to monitor my ascent rate will surely make me enjoy diving more. I never really fully trust computers. It's a black box giving some numbers that your life depens on. If they are wrong, you die, not the computer. It's scary, when people stop to question and just obey.

I also got some good safe diving advice, and I appreciate that people care

 

[daz88]

think you are worrying about things a little too much.

 

[String]

It's a black box giving some numbers that your life depens on. If they are wrong, you die, not the computer. It's scary, when people stop to question and just obey.

I also got some good safe diving advice, and I appreciate that people care

So a watch and an analogue depth gauge as a backup then. Or dive with 2 sets of gauges because if one goes you're aborting the dive and ascending on the backup. The chances of both failing at once are remote.

Its a general theme with diving, always have redundancy and once something breaks forcing you into using a backup you immediately abort.

It is a little scary how many people i see diving though who are unable to execute a safe ascent without a little graph on a computer to tell them. People with computers on the OW course or bought one straight after seem to completely lack the ability to get out safety without a rate gauge.