Ascend drills - how many is too many?
- Thread starter jayknight
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In talking with Karl Shreeves of PADI regarding an article I hoped to write (but abandoned) on ascent procedures for NDL dives, I learned that a 60 FPM ascent rate was the standard at the time the research for the PADI RDP was done, so that was what they aimed for. However, that research found no harm done with slower ascents. Apparently because the PADI research was done with real divers doing real dives, what they really did was ascend "no faster than 60 FPM."
If you think it through, that seems at least a little counterintuitive; in fact, I mistakenly believed about 15 years ago that it was a mistake to follow the RDP and ascend slower than the rate upon which those tables were based. I thought it would invalidate the data. A diligent search of very old threads will find me repeating that misinformation. I now know it is perfectly fine to use the RDP and ascend at 30 FPM, and that is probably a good idea.
The research I did for the abandoned article led me to believe that there is not much good information suggesting an optimal ascent rate, but 30 FPM seems like a pretty good guess.
I wanted to make this point separately. If you take the PADI RDP version of the OW course, you are taught "no faster than 60 FPM." If you take the computer version of the course, it says to ascend at the rate recommended for your computer. For just about any modern computer, that will be 30 FPM..
Is this a real thing that happens in 2022?
Bob DBF
Contributor
As was the research by the NEDU well prior to PADI.
For other readers: The US Navy's recommended ascent rate was originally not clearly defined, then 25'/min, then 60'/min in the 1950s until the 1990s, and is now 30'/min.
Talking to old-timers, 25'/minute worked more like: look at the second hand on your watch, ascent 25', stop until a minute is complete, and repeat. Surface supplied tenders (the guys that "tend" the diver's umbilical) would have a sense of the rate but it was closer to 30'/min or about 1' every two seconds.
Talking to old-timers, 25'/minute worked more like: look at the second hand on your watch, ascent 25', stop until a minute is complete, and repeat. Surface supplied tenders (the guys that "tend" the diver's umbilical) would have a sense of the rate but it was closer to 30'/min or about 1' every two seconds.
I find it MUCH easier because the small bubbles that are about the size of pensile eraser heads ascent at about 60FPM. Of course you watch the cloud of bubbles around you and switch to the smaller ones as they expand. I timed it many times on a calibrated downline and was always within a few seconds.
Bob DBF
Contributor
Back when it was the normal ascent rate, there was no safety stop, and in the case of a CESA one will not be doing a stop, so it's a moot point.
When I learned deco and needed to do stops, it was just a matter of slowing and stopping the ascent the same as at 30 fpm. The idea is to maintain neutral buoyancy during the ascent to prevent overshoot. It's a trick, and I learned it.
Hell yeah!
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