Was "Mike Nelson" right in advising never to ascend faster than your largest bubbles?

[Scubalot]

I recall an early Sea Hunt episode in which Mike Nelson advised never to ascend faster than your biggest air bubbles. If that's slower than 1 foot (30.48 cm) per second, then it could be useful when, e.g., a diver can see his bubbles but not (for whatever reason) his ascent gauge.

An internet search showed sophisticated research and formulas beyond my layman's graspbut the report at this link http://www.waset.org/journals/waset/v28/v28-48.pdf seems to suggest that even the fastest air bubbles in water reach a terminal velocity of 32.9 centimeters or nearly 13 inches per second, and that large bubbles travel slower.

Was Mike right? Can a diver's air bubbles indicate a safe ascent rate?

 

[mala]

20m a minute is pretty fast.


ok if you are deep but not to good near the surface.


mind you he did say slower than the bubbles.-just not how much slower.

 

[OldNSalty]

I actually recall getting that advice one time. If you are ascending faster then your air bubbles there is really a problem.

 

[GrumpyOldGuy]

I thought it was your smallest bubbles.

Anyway, back at that time 60FPM was the standard. Problem is people tend to bend the rules and then go even faster. So they slowed the rate to 30FPM (at least in the last 60 feet).

I would only use it as a contingency with a computer failure and then move a lot slower than your bubbles.

 

[EastEndDiver]

That was something we were taught 40 years ago.It was the smallest bubble.Things have changed !!!

 

[spectrum]

13" /sec X 60 = 780 "/minute
780/12= 65 feet / minute.

That's pretty much in line with the older 60' / minute max ascent rate and that called for the smallest bubble. I suppose there is the smallest bubble and then the smallest that you can watch so in the end it's a solid vintage reference technique. It's a rate that worked well for many years.

30' / minute along with safety stops expand the safety margin. 30/ minute also means many will hopefully at lease stay under 60!

Pete

 

[GROBIOG]

PADI is still 60/min. no?

 

[GrumpyOldGuy]

PADI is still 60/min. no?

60FPM for depths >60, 30FPM for depths < 60

 

[Hawkwood]

PADI is still 60/min. no?

Your question relates to PADI teaching, so the answer is, it depends. What are you using...table or computer? You are taught the maximum safe ascent rate when using the RDP (PADI) is 60 ft/minute. In the case of using a dive computer it is what your dive computer dictates.

 

[GROBIOG]

and does any agency teach to disregard the computer and follow their guidelines?