A question about Ascent rate

[boulderjohn]

What ascent rate do the experts use from bottom to 21m/70ft stop ?

Who are the experts? I would guess that a lot of people who consider themselves to be experts do different things.

I don't think anyone considers me to be any kind of an expert on this, so I guess my response doesn't matter, but I aim for 30 FPM from bottom to top. I do that because I have not encountered any convincing evidence to do otherwise. I am aware of the belief that it is advisable to use faster speeds deep and slower speeds shallow, but I have not seen anything that convinces me that there is enough benefit to it to make a change.

I do believe that ascending slower than planned--often much slower--in the deepest portion of the dive is one of the most common mistakes in tech diving.

 

[Remy B.]

My goal is eventually 75m max, but I will realistically not do any of those deep dives in the next 3 years.

I need to work first on my ascent rates and other technics and have them nailed right before attempting do go beyond 55m

Everything beyond 75m on OC doesn't make much sense to me.

 

[ajduplessis]

Ascent rates, at least for me is based on the pressure differentials during parts of my profile. Let me try to explain this a bit better with some examples in open water situations.

Ascending from a deep dive (300ft) my initial rate leaving the bottom could be as high as 20-30 meters per minute (before reaching 1st stop) as the pressure difference during this part is low. Ascending further to 2 ATA my rate would decrease to around 10 meters per minute following any mandatory stops along the way. The pressure differential during the last ATA is the highest and therefore my ascent rate here is the slowest and would likely be around 3-5 meter per minutes even on recreational dives.

 

[Doppler]

What ascent rate do the experts use from bottom to 21m/70ft stop ?

Not sure there are any experts... some of us have done a few trimix dives if that counts.

ANYHOW

Depends entirely on the target/maximum/average depth... but in a word, variable.

Important to understand that:
1) ascent rate is part of the decompression algorithm and as such, being ad lib with it can have consequences
2) moving rapidly below the off-gassing ceiling is probably a good thing
3) in all cases, listen to what your body is telling you
4)take notes

 

[jstrang]

The general principle that i have followed is to move rapidly up from the descent to the 1/2 point. ie on a 400' dive i ascend rapidly to 200', on a 200' dive i ascend rapidly to 100'.

For dives no deeper than recreational limits 100-130' I dont believe it really matters unless you are using tables. Your deco profile will be pretty close.

For the deeper than 200' or 60m dives it starts to become more significant. I know for me coming up from 300' or deeper is a bit of work - carrying deco/bail out, my rig, a camera i'm huffing along for the 2-3 minutes to get up to the 1/2 way mark.

 

[Remy B.]

Not sure there are any experts... some of us have done a few trimix dives if that counts.

ANYHOW

Depends entirely on the target/maximum/average depth... but in a word, variable.

Important to understand that:
1) ascent rate is part of the decompression algorithm and as such, being ad lib with it can have consequences
2) moving rapidly below the off-gassing ceiling is probably a good thing
3) in all cases, listen to what your body is telling you
4)take notes

I have been feeling good after the few Deco dives that I have done, even that my ascent rate had been slower than 10m/min, now that I have the Tec dive computer that I have, I need to practice too keep it at 6-7m/min which is the max readtout and see how my body feels.

My firsts Deco dives I done were on VPM and I did feel good after those dives, then I changed to GF 45/75 and I have been feeling good as well, but the instructor told me that because I was too slow on my ascents it was more like a 20/70 what I was doing, so I need to work on it in order to continue the trimix pad.

 

[Parklander]

Another reason I love the Shearwater Terik. It displays ascent in actual numeric detail. It has improved my ascents.

Disclaimer: I have not received money or products from Shearwater in exchange for promotion but I won’t turn down the offer.

 

[Michael Guerrero]

I'm no expert, but I shoot for 1atm/min and probably go slower than that every time. That said, I'm usually within a couple minutes of my tables. We do need to keep in mind that we're diving within an envelope of safety, the boundaries to which are very fuzzy to us or our computers.

I would never hesitate to stick with my tables if I'm a little behind in my schedule due to a slower ascent. I'd just try and adjust and maybe stick to my shallowest stops a bit longer for some extra washout, knowing that I had on-gassed more than the table was expecting.

I would expect to dive a ZH-L16C 100/100 GF profile and walk out of the water just fine the vast majority of the time (statistically speaking).