Ascent rate monitoring using air bubbles?

[captain]

To clarify the no faster than your smallest bubbles. No faster than the smallest bubbles from your "last" exhalation.

 

[bleeb]

To clarify the no faster than your smallest bubbles. No faster than the smallest bubbles from your "last" exhalation.

The original, common version of the saying "no faster than your smaller bubbles" seems open to misinterpretation, especially by new divers who may not have remembered, assimilated or even been taught enough background to realize they can't keep following the same bubble, or the one they're following is too big, without someone explicitly pointing it out.

I think captain's version "from your last exhalation" is better, but there's still a bit of wiggle room. The one I prefer is "no faster than a bubble no bigger than the head of a pin." That's <1-2 mm in diameter in any direction.

 

[flots am]

I think captain's version "from your last exhalation" is better, but there's still a bit of wiggle room. The one I prefer is "no faster than a bubble no bigger than the head of a pin." That's <1-2 mm in diameter in any direction.

While this might be useful when you can clearly see the surface and judge your distance, "going up" is not guaranteed. It would be very easy to "go slower than your bubbles" discover that you have gone nowhere or even descended.



flots

 

[Charlie99]

The original, common version of the saying "no faster than your smaller bubbles" seems open to misinterpretation, .....

It also dates from the days when 60fpm was the recommended ascent rate.

 

[scjoe]

I believe 60fpm is the rate the current PADI tables were constructed around.

 

[String]

..maximum rate.

 

[Charlie99]

..maximum rate.

60fpm was a maximum for the PADI tables, but at least some of the USN tables were calculated assuming that the ascent rate really and truly was 60fpm. That changed sometime in early/mid 1990's to 30fpm.

Here's some info on the muddled history of ascent rates for USN tables.
http://www.scubaboard.com/forums/4209673-post4.html

Originally slow ascents for hard hat divers being winched up on stages. Then scuba divers wanted 100fpm+ rates while hardhats wanted 25fpm. They compromised on 60fpm.

Then in mid 1990's the USN changed the recommended ascent rate to 30fpm.

The recreational agencies that adapted the USN tables generally chose 30fpm maximum as the recommended ascent rate.

Nobody (that I know of, except DCIEM) specifies what is an unacceptably slow rate, but that is an entirely different subject.

 

[bleeb]

The DCIEM table specifies 50 plus or minus 10 fpm.

 

[LeadTurn_SD]

To clarify the no faster than your smallest bubbles. No faster than the smallest bubbles from your "last" exhalation.

Yep.

If you have nothing else to use, this still works. Acending up a line is easiest (usually), followed by a computer with the ascent rate thingie, then a watch and depth guage will work fine..... but "bubbles" work in a pinch.

There are better methods, but if none of those are avaialable, at least with the "bubble method" you have some reference point for how fast you are ascending: If you are passing the smallest bubbles that you just exhaled, you are going too fast (maybe way too fast :shocked2: ).

Best wishes.

 

[Subcooled]

My computer has such a little graph. It's so small and difficult to see though, that I'm only counting seconds in my head and looking at the depth value. One decimal, 0.1 meters, per second.

My diving hobby comprises diving activity and academic matters, both of which are interesting.