Ascent from Minimum Deco Dive

[Soggy]

This is the post I was referring to on the FifthDX yahoo group. It is interesting to note that it is not what was taught in any fundies class that I have attended, including the one he taught. So, I don't know what the 'real' answer is. I have email correspondence from another GUE instructor saying very explicitly stating that one is to start deep stops at 80% ATA and then proceed at 10fpm up from there.

Who knows. I guess I'll learn the real stuff in Tech 1, eh?

From Michael Kane:

Rather then introduce certain concepts at the Fundamental level, specifically 80% of ATA's, we recommend for an otherwise recreational profile, to start the deep stops at 50' from the max. depth. In other words, if you did a 120' dive, start the deep stops at 70'. Then do 30 second stops, with 30 second moves until you start your "safety" stops. In lieu of the industry standard of 3 minutes at 15', we recommend doing an additional minute at 30', then a minute at 20' and then a minute at 10'.

So to summarize, you do 30 FPM ascent rates, you start your deep stops at 50' off the max. depth, continue "deep stops" at 30 second stop- 30 second move intervals until you get to 30'. Then do 1 minute at 30', 1 minute at 20' and 1 minute at 10'.

Bear in mind, this ascent rate strategy applies to no mandatory
decompression diving within otherwise defined recreational limits. If you plan of progressing to deeper then "recreational" limits and/or doing mandatory decompression diving, this strategy is inapplicable.

 

[jonnythan]

The point I take home from the whole thing is that when you take GUE's deco procedures and extrapolate them to the low end of no required deco, you can go a lot of ways with it.. none of which are necessarily any better than the others. Don't fret over where you do your stops as long as you plan them and they make sense to you.

Worry about the numbers and real procedures when they teach them to you.

 

[Spectre]

I think the thing to realize here is the building in of a conservative approach. Sure, with an NDL dive you should be able to run 60fpm to the surface with no stopping. A 'safety stop' is just that... a method to add a little bit of security to be safer [hense the 'safety' part of it]. If you look at something like the PADI tables [from memory here], they have ranges within the NDL limit where your safety stop becomes a required safety stop, and then longer safety stops if you get too close to the limit.

It's not meant to be 'the way the big boys do it', it's just meant to add a little conservativeness to the ascent to increase your chances of getting out if you screw up.

Along the same lines, the linear approach that Soggy is being given isn't necessarily the way the 'big boys' do it, as will be learned in later classes I assume, but it's a more conservative approach to other methods.

Let's look at the profile in question. 1 minute from 100 to 70, then 1 minute every 10 feet from there on. That's 8 minutes. Sure, that extra minute from 70-60 might add a little on-gassing, but you still have 6 more minutes from there to the surface, rather than a traditional 1 or 2 minutes from 60 up.

Even going PADI style, 30 ft/min from 60 to the surface with a 3 minute safety stop.. that's 5 minutes. Soggy's doing 6. adding a minute at 70 isn't going to give you an extra minute obligation... so he still comes out ahead if he ongasses for that minute at 70. [even saying 1:40 or so for the time from 70 to you get past what V-planner says the offgassing point is isn't going to give you an extra minute of deco when you're sitting in an NDL scenario].

Another thing to remember is that there's no 'line' between ongassing and offgassing. It's different compartments that ongas and offgas at different speeds. Continued ongassing of slower compartments on deeper stops isn't going to be much of a deal when doing recreational dives unless your doing a liveaboard or something to that effect where the slow tissues never get a chance to offgas like they would in regular weekend divers.

I don't know for sure what MHK is truely saying for a profile in his response. 1 minute stops generally mean 30 second stop, 30 second moves. Since he references both, I can only assume he's saying 1 extra minute at 30, 20, and 10. So that'd be saying 1 minute to 70, another 4 minutes to 30, and then another 6 minutes to the surface.... which pads the safety even more. 8 minutes from 50 up is -more- than enough to cover that minute or two below v-planner's magic line.

Now... the only part I don't quite get is why some feel that 80% and 50% in ATA is too complicated for a Fundies student to grasp

 

[reubencahn]

This is not the ascent strategy taught in Recreational Triox--which deals only with recreational depths and no deco profiles.

 

[MHK]

I think that point that appears to be missing from this thread is one that we try as hard as we can during the DIR-F classes to bring home. Noting that scuba forums aren't necessarily the most productive method of communicating this type of information, I'll do my best to address the issue(s).

One of the initial goals of our introduction to ascent rate strategies in the DIR-F class is to begin to move the student off of the industry way of thinking. In other words, we believe every dive has an element of "decompression" associated with it, accordingly we try to move the student from a "No Decompression Limit" way of thinking towards a view that no such thing exists. Once the students accepts that premise, we can then move towards the notion of various ascent rate strategies. Those of you that are weighing in on what one instructor said versus another in different DIR-F classes, are largely missing the broader scope, which is to say that it isn't an exact science, and it's all about knowing how to shape the ascent rate curve. The difference between 80% of ATA's versus 50' of max. depth [ assuming a recreational profile] is a distinction without a difference and should be viewed from the prism of a different means to the same end, as opposed to a stark inconsistency.

Overall, the recomendation in the recreational setting [ Please do NOT confuse this approach with a dive that required accelerated decompression as the strategy will differ], but for the average Joe diver, doing a dive within otherwise defined "recreational" limits is as follows:

Use a 30fpm ascent rate;
Initiate deep stops at 50' of the max depth;
Continue deep stops using a 30 second stop- 30 second move approach at 10' incriments;
Commence your "safety stop(s)" at 30' for 1 minute, then 20' for 1 minute and lastly at 10' for 1 minute

There are various other ways to achieve the shape of the ascent curve that we like, but rather then parsing language, please appreciate that the end goal is to understand and implement an ascent rate that will maximize off-gasing and allow for bubble reduction in a complimentary fashion. Those that are worrying about whether instructor A said to start deep stops at 80% of ATA's and/or start the "safety stops" at 40' is missing the larger picture, and that larger picture is what is infinately more important then the minutae of what is being written so far in this thread.

I caution once again, as your diving habits progress, and you extend depth and/or extend acceptable bottom times and mandatory decompression obligations accumulate the above referenced ascent rate strategy will be inapplicable, and may very well lead to adverse consequences. For that reason you don't see many GUE instructors posting on scuba forums any additional "advanced" ascent rate strategies, since we don't believe it's effective or efficient to post an incomplete picture, which could be easily misunderstood and misapplied by someone who does not posses the requisite training or skill level.

For those that have taken my class, and something still isn't clear, please feel free to e-mail me and I'll try to clear up any confusion, but I'm reluctant to go any further on a scuba forum.

Hope that helps.

Michael H. Kane

 

[MHK]

So, I don't know what the 'real' answer is. I have email correspondence from another GUE instructor saying very explicitly stating that one is to start deep stops at 80% ATA and then proceed at 10fpm up from there.

Who knows. I guess I'll learn the real stuff in Tech 1, eh?

Soggy,

If you compare 80% of ATA's with 50' of max. depth I suspect you'll find that they tend to be a few feet apart ;-) It's just a different way of saying the same thing. Think of it if you lived 60 miles away from someone, and one day I said drive 60 mile per hour and the next day I said I'll see you in an hour..

Again, I go back to look at the bigger picture rather then focusing in on the differences amongst how different instructors explain the issue. At the end of the day, the results are the same. The 80% of ATA "rule" is more applicable in the "technical diving world", but applies equally as well in the recreational world and as I noted, I suspect you'll find that 80% of ATA and 50' of max. depth are pretty close in dives of 120' or shallower..

Regards

 

[Soggy]

So are you saying I should just continue doing what I'm doing and that I'm not too far off base?

If you compare 80% of ATA's with 50' of max. depth I suspect you'll find that they tend to be a few feet apart ;-)

 

[Spectre]

If you compare 80% of ATA's with 50' of max. depth I suspect you'll find that they tend to be a few feet apart ;-)

Somehow I think if anyone was 23 feet off on a stop, they'd fail your class.

I suspect you'll find that 80% of ATA and 50' of max. depth are pretty close in dives of 120' or shallower..

Doesn't seem to get close in my eyes until around 210'.

It's kind of funny. One of the senses I got from GUE was that they prepare you for the further steps. You might not know the full reasoning right off the bat; like why your compass is best on the left wrist instead of the right wrist; but it's there so when you get further along, you don't have to change anything; you just realize the reasoning behind each little thing.

So why is it on this issue, GUE feels the need to confuse the issue rather than doing something as simple as "Pause at 80% of the max ATA, and then begin 1 minute stops at 65%, or 40 feet, whichever is deeper"... which prepares them to start being aware of 80%, 65%, and the other percentages who's significance will become apparent as they get further down the road?

 

[lamont]

If you're doing rolling stops from 100' starting at 50 feet, that should add 2 mins to your ascent time compared to a simple 1@30/20/10 profile (i get 9 mins vs. 7 mins). Should this get added to rock bottom times as well?

 

[Soggy]

If you're doing rolling stops from 100' starting at 50 feet, that should add 2 mins to your ascent time compared to a simple 1@30/20/10 profile (i get 9 mins vs. 7 mins). Should this get added to rock bottom times as well?

Of course. If it takes longer to get up, it takes more gas to get up....x2