Ascent Rates (How to..?)

[261311]

One thing that I think seems to be glossed over is ascent rates, my RDP says 60 and that's what my PADI instructor reinforced but I've read people with ascent rates as low as 10fpm and my curiousity is how is that physically achievable? Even with the best buoyancy it would seem like if you performed any movement you would exceed that very quickly. Does one have to take frequent breaks from a very slow kick to achieve something this slow? How does that work?

Ideally I think achieving 30/40 is something that I'd like to adopt on my deeper and more time-sensitive dives but I'm wondering if there's any other way rather than trial and error staring at a dive computer. My instructor said the smallest bubbles from a diver exhaling move at around 60fpm, for example and not to exceed those.

 

[Doppler]

The generally accepted rate for sport dives (within the NDL) is about 9 metres per minute... for technical exposures, ascent rate is variable with 9 metres per minute around the maximum.

This is achieved by something called control. It may seem difficult but really is not... and it is possible to move through the water column slower than 3 metres per minute...

what part of Canada are you in?

 

[dbulmer]

To the OP,

A great answer above from Doppler above.

Someone like Steve will be able to control their ascent to 1m per minute.

The trick is fine tuning your buoyancy with your breathing (if on open circuit), having the right weighting and a lot of practice.

A tip for improving buoyancy is to move slowly and signalling to your buddy that you wish to stop. Notice if you rise or sink in the water - if you stay in the same position you are neutral and its neutral buoyancy combined with fine tuning your breathing that enables you to achieve slow ascent rate.

 

[Diver0001]

One thing that I think seems to be glossed over is ascent rates, my RDP says 60 and that's what my PADI instructor reinforced but I've read people with ascent rates as low as 10fpm and my curiousity is how is that physically achievable? Even with the best buoyancy it would seem like if you performed any movement you would exceed that very quickly. Does one have to take frequent breaks from a very slow kick to achieve something this slow? How does that work?

.

It works exactly how you think it does. you take breaks.

The question is how to do this on the fly.

I'll assume you work in metric because it's really easy. You can translate it to imperial if you must.

The basic ascent rate that everyone uses these days is 10m/min (or 9, but 10 is a nice round number).

So say you're at 40 metres and you need to ascend to your safety stop at 5 metres. How to precisely control your ascent rate? That's your question, right?

Well it's really simple. First, you look at your clock before you leave the bottom. Let's say it says 8 minutes. You then ascend to 30 metres using bubbles, computer input and (eventually) your experience to gauge your ascent speed.

When you get to 30 metres, you look at your clock. If it still says 8 then you WAIT at 30 metres until your clock flips to 9 minutes. You then continue to 20m and check again. At 20 metres you wait until the clock flips to 10, at 10 metres you wait until your clock flips to 11 and then you can ascend to your stop at 5 metres. You've just made a controlled ascent from 40 metres to 5 metres at very near (almost precisely) 10 metres per min.

So what do you do if you get from 40 metres to 30 and your clock already says 9 minutes? Just don't stop. keep going straight on to 20 metres and check there again.

And finally... what do you do if you start falling behind? Say you go from 40 to 30 metres and your clock says 10 minutes instead of the 9 you expected? In this case you (a) keep going on to 20 metres AND (b) add that extra minute to your bottom time.... especially if you're using tables. The point here is don't start rushing your ascent if you get a minute or 2 behind. Just keep going and add the extra time to your bottom time.

That last point is one of the reasons it's good to leave the bottom BEFORE you get right to the NDL so you have a bit of a buffer if you start falling behind on the ascent.

Does that give you a bit of a grip on it?

R..

 

[eponym]

One thing that I think seems to be glossed over is ascent rates, my RDP says 60 and that's what my PADI instructor reinforced but I've read people with ascent rates as low as 10fpm and my curiousity is how is that physically achievable? Even with the best buoyancy it would seem like if you performed any movement you would exceed that very quickly. Does one have to take frequent breaks from a very slow kick to achieve something this slow? How does that work?

If you're horizontal in the water (instead of vertical) it gets much easier. Get horizontal and get neutral. Then use one larger-than-normal inhale to move up a tad, then exhale and dump air (drysuit or bc) if necessary to re-adjust to neutral. Pause, breathe, repeat.

Horizontal trim allows the water to give you the maximum resistance to movement, so it dampens any buoyancy shifts. And you can fin slightly up or down if your buoyancy gets negative or positive, giving you time to add or dump gas.

I ask new dive students to walk a thirty-foot / nine-metre line in class and take one full minute to do so. They quickly get the idea of adding short pauses between steps. Same thing when diving.

Of course, you can (with practice) do a continuous thirty feet per minute ascent, but it takes some practice and some finesse. Don't watch your dive computer or depth gauge, instead watch an anchor line, the wall, the kelp "trees", or even the plankton floating in the water.

 

[ScubaInChicago]

We'll usually do a 30 sec travel/10' (ft) and stop for a predetermined amount of time to the next ten foot mark. You can deploy an SMB as a crutch or use an up line and focus on your breathing, ascent, and air spaces (drysuit, BC, RB counter lungs).

---------- Post added March 18th, 2013 at 06:59 PM ----------

It's a babystep towards tech diving, but your body will fell so much better when you get out....I use to feel like I needed a nap after diving when I did a foot a sec (it's crazy unless it's an emergency).

You'll know you got it down when you add some major task loading while keeping you ascent rate constant.

 

[g1138]

Well skilled divers don't have to kick on ascent. Rather they use a bit of air expansion to ascend them, either by swimming up or inhaling a bit deeper. As they ascend too quick, (well before 20ft/min) they deflate their BC a little to control the ascent rate. This allows for a very slow controllable ascent.
And for what it's worth, PADI and all other agencies now recommend an ascent rate not exceeding 30ft/min. 60ft/min is an older hold over from most agencies.

Additionally ascending horizontally allows less of a bouyancy swing between your lungs and upper body being 3 ft above your lower body. In a thick wetsuit, with your BC riding up on you, this creates a big swing in bouyancy, especially if you tilt up from horizontal to vertical; in fact by doing that, you're already starting in an uncontrolled ascent, especially at shallow depths.

Horizontal ascents are much trickier, because you have to time your breathing rate. And additionally you can't see what's above you, so you have to roll over to check or rely on your buddy to spot you, while you do the same in return. This means both you and your buddy have to maintain a constant static team position, which for new divers can be challenging.

[video=youtube;OXwQTU1z1t0]http://www.youtube.com/watch?v=OXwQTU1z1t0[/video]

 

[Kevrumbo]

One thing that I think seems to be glossed over is ascent rates, my RDP says 60 and that's what my PADI instructor reinforced but I've read people with ascent rates as low as 10fpm and my curiousity is how is that physically achievable? Even with the best buoyancy it would seem like if you performed any movement you would exceed that very quickly. Does one have to take frequent breaks from a very slow kick to achieve something this slow? How does that work?

Ideally I think achieving 30/40 is something that I'd like to adopt on my deeper and more time-sensitive dives but I'm wondering if there's any other way rather than trial and error staring at a dive computer. My instructor said the smallest bubbles from a diver exhaling move at around 60fpm, for example and not to exceed those.

30 fpm ascent rate translates to one foot every two seconds. From your working NDL depth, ascend up to your safety stop either in 10' increments & pause at each for 20 seconds; or to be more conservative --every 5' do a pause for 10 seconds.

Ultimately when you get good at a continuous ascent rate with firm buoyancy control, while glancing your Bottom Timer or Computer, you try to do two easy rhythmic frog kicks in two seconds to move upward in approximately one foot increments --all the way to your deco or safety stop. . . (in rough or current heavy conditions at depth, just revert back to pausing 20 seconds at every 10' interval).

 

[dumpsterDiver]

One thing that I think seems to be glossed over is ascent rates, my RDP says 60 and that's what my PADI instructor reinforced but I've read people with ascent rates as low as 10fpm and my curiousity is how is that physically achievable? Even with the best buoyancy it would seem like if you performed any movement you would exceed that very quickly. Does one have to take frequent breaks from a very slow kick to achieve something this slow? How does that work?

Ideally I think achieving 30/40 is something that I'd like to adopt on my deeper and more time-sensitive dives but I'm wondering if there's any other way rather than trial and error staring at a dive computer. My instructor said the smallest bubbles from a diver exhaling move at around 60fpm, for example and not to exceed those.

As a new diver, it will be somewhat challenging. I think the best way is to go with someone who has it down perfectly. Just follow them up, stay with them and watch and mimic them as best you can.

i think all computers now have ascent rate information. Use the computer and check it very often until you learn by observation what a slow, controled ascent feels like.

You may be surprised that it is much easier when coming from the deep, because the air expansion in BC (and wetsuit expansion) occurs much slower at depth. It only really gets tricky above 30 feet or so and once you reach 10 feet, you will have to really pay attention.

I used to teach my students to GENTLY kick up. watch the particles in the water for clues as to your speed and if you are going up or down or stopped. Even in clear water there are particles out in front of you a few feet that give good clues. If you kick your way up, then when you begin to feel like you are going too fast, then you stop kicking.. if the particles tell you that you are moving up, then dump a little air and then check the particles in the water. If they show that you are stopped or sinking a tiny bit, begin gently kicking up.

Eventually you will learn to kick very little and once you got it down, you won't have to kick at all. Just breath control.

 

[DevonDiver]

Controlled/precision ascent is a buoyancy skill dictated ability. Practice makes perfect - most novice divers would struggle to believe what level of control is achievable if you put your mind, determination and patience towards refining and developing that ability.

The best way to develop excellent buoyancy is through long-term mentoring. Find a diver/s of excellent ability to dive with, refine your skills with them as role-models and able to provide you with critical feedback and tips.

Shorter/finite-duration buoyancy focused courses are also a good idea, but can only help you refine based on your current/immediate level. The best courses provide you with a 'road map' for future improvement. Of all the agencies, GUE probably has the highest focus on developing superior foundational skills. Researching media and materials relating to GUE courses, in particular the Fundamentals (or "Fundies") can be quite enlightening.

Other agencies, like PADI also provide buoyancy specific training; such as the Peak Performance Buoyancy (PPB) course. On paper, this course should be good, but sadly the dramatic variance in instructor quality means it is no sure bet for achieving profound results. With the big agencies, the necessity to research and confirm specific instructor ability is critical.