how do you ascend SAFELY???

[mislav]

The Mac guys are the people with the really cool computers, who always complain that they can't find software.

Terry

Nautilus. And it's good.

The person who wrote GUE's decoplanner program was in my fundies class and he looked like a Mac guy. Might be worth writing him and asking about a Mac version if you're really interested.

Got a link for Nautilus, Perrone? I can't find it.

I doubt the Mac guy would write a program solely for me, but I'm positive I wouldn't be the only one buying it. Who knows, if it's no bother, you may well ask him a question.

 

[ianr33]

thank you guys for all the great replies. keep them coming
also can anyone point me towards a good decompressing program or something like that to plan dives?
sb is great
again thank you

If you have less than 25 dives,and are asking about ascent rates on recreational dives then you probably dont need to start worrying about deco software just yet.

 

[PerroneFord]

Got a link for Nautilus, Perrone? I can't find it.

Go here... click on software:

http://www.techdivinglimited.com/

 

[Dive 'N' Dolphin]

my question to the members of sb is what are your procedures for acending from a dive.

please include the following:
-how many feet per minute
-how long of a safety stop do you do if you do one
-at what dept do you do the stop
-do you do deep stops

im looking for replyes from everybody even deco divers
im just here to learn more and i really need to figure out what the safe acent rate is

also i think i recall somebody telling me how the rates should be 60 fpm until 30 feet then 30 feet per min
is that correct or am i getting the numbers mixed up?

i would like to thank anybody that contributes in advance

The deepest I have been is 100ft but what I do, for first 11 dives I use to struggle with not coming up to fast and at 20 being sucked up because to buoyant then when I went to Cozumel another dive taught me a trick the first time out and I use it every time now. Not really a trick but a different way to do it. When I decide that I am going up. I dump all of my air out of my BC then I slowly kick my way up. Just 1,2 kick 1,2 kick real slow and at 20 feet I do a 5 min safety stop. You can do 3 but I like to be on the safe side and do 5. Now at the safety stop if you are properly weighted you shouldn’t need to kick to just hold your spot in mid water with maybe a kick her and there to stay at 20 but the good thing is you don’t feel the pull that you are being sucked out. You are not kicking like crazy upside down to hold it. Then after 5 I slowly head back up. I have a Uwatec Smart Computer and it is great. It will beep if going to fast and I never have that problem. I just watch the computer on my way up make sure going slow and what depth I am at. Then at the last 10ft I let go of the computer put my hand up and slowly kick the rest of the way up. Once to the top I fill up the BC with air.

Stacy

 

[Charlie99]

Ratio deco, huh Charlie?

Nah. Just what I worked out long before I ever heard of ratio deco. It's like you said in your earlier post, the "slower as you get shallower" curve shows in the output of deco programs, including for "ndl" dives if one cranks up the conservatism to absurd levels in order to force the program to generate deco stops on what is normally considered a no-stop dive.

Another way to look at it, is that a 60 or 30fpm ascent with a single stop at 15' is a crude, one step approximation of the ideal curve.

A 30fpm ascent to xx% ata, and then 10fpm (or equal time stops every 10') to the surface from there, is also a crude, one step approximation of the ideal curve.

My system is a 3 step approximation of the ideal curve. For me, it's the right tradeoff between complexity of the profile, and efficiency of deco. Or to put it more crudely, if I'm going to waste my time hanging out for xx minutes, I might as well make it as short and as useful as possible (while not making tooooo complex).

--------------------

Edit: Thinking back to around '99 when I started that type of ascent, it was also a result of my extension to NDL diving the deep stops per the Richard Pyle method. He found that he felt a lot better on dives where he did a deep stop. His method was to stop halfway between the bottom, and any required deco stop. Then stop again halfway between that stop and the 1st required deco stop (provided it was more than 30 or 40 feet of difference). A string of constant length stops, but the depth of each half of the previous one is another way to generate the "slower as you get shallower" curve. I tried adapting that method to NDL diving it a few times (treating the 15' safety stop as a deco stop). It was awkward, though, and I came to the conclusion that the equivalent more or less constant increment of depth, but increasing time per stop was easier for me to track mentally -- particularly since my computer doesn't have a second timer.

 

[Thalassamania]

First of all, there's no such thing as a "safe" ascent. Safe means without risk and all ascents have some element of risk to them. With that in mind:

Ascent rate is part and parcel of your decompression model. The old U.S. Navy tables, that were designed solely for hard hat dives who stood on a platform or stage (thus: Stage Decompression). The stage was winched up and down in the water column at 25 F/M. When new tables were first developed after the advent of SCUBA the combat swimmers (UDT in those days, EOD or SEAL today) wanted 100 to 120 F/M, but the MK-5 divers said that they could not crank the stage up that fast. A test was run at the EDU dock in Washington D.C. and the fasted that the stage could be cranked was 60 F/M thus the compromise resulted in the number used for the next generation of the U.S. Navy Standard Air Tables. Confused? I was at first. Here's the bottom line: the faster the ascent rate, the more limited the exposure has to be to have a "no-bends" ascent.

Many of us dove those tables and used that ascent rate for many years without any bends. But recreational divers were notorious for coming up much faster. There were studies that indicated 180 F/M in many cases. The training agencies cut back on the ascent rate with the real intent, at the time, of slowing folks down to no more than 60 F/M. The “safety stop” was introduced for much the same reason, a lot of discussion was had with the conclusion that a diver (who did not have a stage decompression obligation) could, with minimal risk come from depth to twenty or so feet about as fast as they wanted and then could go on to the surface as long as their “average” ascent rate was in the neighborhood of 60 F/M and their actual ascent rate from 20 feet to the surface was actually 60 F/M or less. So by stopping at 20 the dive would let the average decay to 60 F/M. Well … if the diver was as deep as they would ever go (read that as 130 feet) you could guarantee an average ascent rate under 60 F/M if they stopped for 2 mins.

People being what they are, and given the assumption that more is always better (and lawyers too boot), ascent rates were cut to 30 F/M (and in some cases 20 F/M) and tables were hacked back one step, all without any data or experimentation or modeling, just on the concept of, “it seems like a good idea,” The exceptions to the by-guess-and-by-golly, more is better, school of decompression theory were some of the computer manufacturers and the development of the PADI RDP (which, I feel has other “assumption” problems), all of which build ascent rates slower than 60 F/M into their model calculations.

Later studies bore out the not-quite-accidental reasonableness of some of these approaches. Of special note is the finding that bubble formation could be controlled if, in essence, the amount of dissolved nitrogen could be cut back by 20% from what the U.S. Navy table had permitted. Keep in mind that in the early days, without computers, we were calculating “square dives” that rarely produced 100% of the modeled nitrogen uptake.

Doppler work bore this out and the deep stop was introduced as a practical way to cut back the controlling tissue nitrogen level. This has resulted in the RGBM (reduced gradient bubble model) and the VPM (variable permeability model).

The bottom line for recreational divers is that it is reasonable to use a 60 F/M ascent to a deep stop for one to two minute stop at half your maximum depth (unless your computer complains) followed by a 30 F/M ascent to a “safety stop” of two minutes between 20 and 15 feet, followed by a 30 F/M or slower ascent to the surface. Maintaining maximum permissible outgassing pressure, as discussed by previous posters, is another benefit of a 60 F/M ascent to your deep stop.

This just significantly lowers your risk, it does not eliminate it, and in an emergency, keep in mind that many of us made no-decompression dives that were 5 to 10 minutes longer than what is permitted today and made direct 60 F/M ascents to the surface with no ill effects.

 

[Carribeandiver]

I find that if you ascend feet first, then you can go as fast as you like because all the nitrogen then settles in your feet. Studies have proven that feet expel nitrogen quickest which translates to shorter surface intervals as well as rocket fast ascents.
Feet First ::::: the trend of the future. This is an unproven strategy of course, if anyone tries it, please send a detailed report -- if you survive, that is.

 

[Charlie99]

I find that if you ascend feet first, then you can go as fast as you like because all the nitrogen then settles in your feet. Studies have proven that feet expel nitrogen quickest which translates to shorter surface intervals as well as rocket fast ascents.
Feet First ::::: the trend of the future. This is an unproven strategy of course, if anyone tries it, please send a detailed report -- if you survive, that is.

The rapid, feet first ascent method has had widespread, extensive, empirical study. The test participants are also known as "new drysuit divers".

The physiological results have been mixed, but psychological effects often include intense embarassment.

 

[The Kraken]

Slowly, with your buddy, and on a line if at all possible.

the K

 

[mislav]

Go here... click on software:

http://www.techdivinglimited.com/

I've downloaded it and tried the free version for now. I haven't figured it all out yet, but I do see that it's a good planner. I like it and I'll buy it eventually. Thanks!

Btw, if anyone's interested - there are Windows versions of it as well.