how fast to ascend...

[Charlie99]

Watching little bits of stuff in the water is good for realtime, instantaneous depth control over short periods of time (unless there is a upcurrent/downcurrent).

For large depth changes, such as for controlling the overall profile and timing of the ascent, I use my computer depth gauge and elapsed time. Upon starting the ascent, I pick out a couple of depth & times ---- for example, at what elapsed dive time I plan on surfacing, which time I plan on hitting 50', and what time I plan on going to 20'.

Typically I'm doing 3 or 4 stops on the way up, and these set my overall average ascent rate. Some DAN tests have shown that the overall average ascent rate over a period of a couple minutes is what counts rather than the instantaneous rate over a few seconds.

If you stay neutral all the way up, then you can easily control your ascent rate with your breathing pattern while watching the little bits of gunk in the water. Staying horizontal give more vertical drag and makes it easier. An occasional glance at the dive computer for depth and time tells you if you are on the desired overall large scale ascent profile.

Just hovering horizontally without moving while at a 15' safety stop is really good practice in buoyancy and ascent control. Once you can stay motionless at 15', you will find that it is easy to control your ascent with breathing.

Charlie Allen

 

[diebeste]

if there is a failure in both or even a failure in my primary air source, and switch to my redundant air source...

As I said above, the depth gauge is not dependant on your air, so even if your primary air source fails, the depth gauge portion of the SPG will still be working (if there is one, of course).

 

[jbd]

Watching little bits of stuff in the water is good for realtime, instantaneous depth control over short periods of time (unless there is a upcurrent/downcurrent).

For large depth changes, such as for controlling the overall profile and timing of the ascent, I use my computer depth gauge and elapsed time. Upon starting the ascent, I pick out a couple of depth & times ---- for example, at what elapsed dive time I plan on surfacing, which time I plan on hitting 50', and what time I plan on going to 20'.

Typically I'm doing 3 or 4 stops on the way up, and these set my overall average ascent rate. Some DAN tests have shown that the overall average ascent rate over a period of a couple minutes is what counts rather than the instantaneous rate over a few seconds.

If you stay neutral all the way up, then you can easily control your ascent rate with your breathing pattern while watching the little bits of gunk in the water. Staying horizontal give more vertical drag and makes it easier. An occasional glance at the dive computer for depth and time tells you if you are on the desired overall large scale ascent profile.

Just hovering horizontally without moving while at a 15' safety stop is really good practice in buoyancy and ascent control. Once you can stay motionless at 15', you will find that it is easy to control your ascent with breathing.

Charlie Allen

As always with Charlie99---very solid info/advice.

 

[LI Diver]

Typically I'm doing 3 or 4 stops on the way up, and these set my overall average ascent rate. Some DAN tests have shown that the overall average ascent rate over a period of a couple minutes is what counts rather than the instantaneous rate over a few seconds.



Charlie Allen

Does that mean that a few extra minutes spent at a stop would make up for some faux pas in a ascent?

 

[OE2X]

I guess if my depth gauge went TU then:

1. I would immediately let my buddy know.

2. I would ascend with three things in mind Visual - particulate matter, Ears and buddies gauge.

3. If you are doing a shore dive - it's easy to use the slope of the land to very slowly work your way up to surface.

4. Having your gauge fail is not necessarily a dive ender.

I have practiced airshares in blue water where as the donor and in charge of the acsent, my mask was taken off. Now the OOA victim is in charge of the ascent. We ascend at 30' per minute and hit and hold all of our stops. You have to rely on your buddy and his depth gauge/bottom timer.

 

[rawls]

is there a way to make a lot of small bubbles and keep them coming up in front of your mask so you can see them moving... my regulator deflect the air the left and right of me, so i'd be swimming in spirals...

Stunaep...I would think it would be a little difficult to make alot of small bubbles. It would mean you would have to focus alot on exhaling through your regulator. And I think you could get into trouble with that. When you are trying to control your breathing in that manner I feel it would put you at risk of holding your breath at some point. We are taught to breathe evenly and normally and that's what I would suggest. In addition to that I think kidspot mentioned a good step and you can also use a slow hand over hand method. You can use your bubbles as a benchmark and ascend hand over hand in a slow manner. But again, I wouldn't suggest you trying to blow small bubbles. It simply isn't necessary and it could cause trouble...

 

[K Mejean]

In this regard I guess I am lucky. I have ears that tell me when I am moving too fast. If I don't go up and down at a very slow rate I have a hard time equalizing. I was really concerned about ascending too quickly in the beginning so I bought a computer but it didn't take long to figure out that the computer and my ears were saying the same thing.

 

[Charlie99]

Does that mean that a few extra minutes spent at a stop would make up for some faux pas in a ascent?

Dan Europe has some interesting articles on some tests they performed. One of several that address ascents is titled The Speed of Ascent Dilemma: "Instant Speed of Ascent" or "Time to Surface" - which one really matters?. From their testing, it appears that the instantaneous rate of ascent is not as important as the overall average ascent rate or total time to surface.

Another simplistic way to look at it is that offgassing and bubble formation takes place over a period of a few minutes. From a decompression viewpoint, a perfectly constant ascent at 10 feet per minute, isn't all that much different than an ascent where you pop up 10' at 60fpm (10 seconds) and then wait another 50 seconds before popping up another 10'. This is very true deeper than 40', but is less valid for a 20' to 10' or 10' to 0' move.

My interpretation is that what counts during the ascent is the depth as averaged over a few 10's of seconds.

That's what is behind my practice of moving up in a controlled fashion, but not worrying too much about the instantaneous rate of ascent. OTOH, I do pick out to time-depth waypoints that I pass through, such that my ascent has both the total-time-of-ascent I have chosen when starting up, and also has the "slower-as-you-get-shallower" overall profile that has been repeatedly shown to be the optimal type of ascent.

Charlie Allen

 

[rocketry]

I always try to limit my ascent to 30 feet per second. I always use the "floaty things" in the water to guage my rate, and, of course, my computer's ascent reading. I personally like to make myself negatively buoyant on my way up, by dumping some air out of my BC before I ascend. I eventually get myself into a rythm with my fin kicks so far as I hold a good rate. And, since the air in the BC is expanding, I am usually pretty neutral when I do my stop at 15' (with a few, minor buoyancy adjustments, of course!). After 15 feet, I take it as SLOW as possible. I'm not rushing to get anywhere! Why not make the last minute of my dive enjoyable!...and all the more safe? I'd like to be underwater as long as possible. Provided I have ample pressure in my tank, I'm not freezing my butt off, and the boat's not leaving me: its a slow and leisurely ride to the surface for me.

 

[boulderjohn]

Dan Europe has some interesting articles on some tests they performed. One of several that address ascents is titled The Speed of Ascent Dilemma: "Instant Speed of Ascent" or "Time to Surface" - which one really matters?. From their testing, it appears that the instantaneous rate of ascent is not as important as the overall average ascent rate or total time to surface.

Another simplistic way to look at it is that offgassing and bubble formation takes place over a period of a few minutes. From a decompression viewpoint, a perfectly constant ascent at 10 feet per minute, isn't all that much different than an ascent where you pop up 10' at 60fpm (10 seconds) and then wait another 50 seconds before popping up another 10'. This is very true deeper than 40', but is less valid for a 20' to 10' or 10' to 0' move.

My interpretation is that what counts during the ascent is the depth as averaged over a few 10's of seconds.

That's what is behind my practice of moving up in a controlled fashion, but not worrying too much about the instantaneous rate of ascent. OTOH, I do pick out to time-depth waypoints that I pass through, such that my ascent has both the total-time-of-ascent I have chosen when starting up, and also has the "slower-as-you-get-shallower" overall profile that has been repeatedly shown to be the optimal type of ascent.

Charlie Allen

Additionally, another Dan study showed that safety stops were indeed more important than the ascent rate. After testing several ascent rates, they found that the best choice was a 30 ft/min rate with both a deep stop and normal stop, but a 60 ft/min rate with the stops was superior to a 30 ft/min without the stops. (These were 5 minute stops.]

Both the 30 and 60 ft/min rates were superior to 10 ft/min.