Ascent from Minimum Deco Dive

[Spectre]

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?

The point of rock bottom is to reserve enough gas to get you and your buddy up through the planned ascent. So whatever your planned ascent is should be the ascent used in calculating your rock bottom.

 

[MHK]

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?

I thought we were making real simple by saying:

"Start your deep stops 50' from max. depth and do 30 second stop, 30 second move until you hit 30'". I'm not sure how much simplier we can make it. Certainly as you progress the 80% of ATA rule is more realistic, but at the DIR-F level our goal is to introduce ascent rate strategies that more often then not are the first time students encounter any such dialogue. I can't tell you how many times I ask a student to compute how many ATA's at 100', and all I get is blank stares.

The big picture that is our goal to communicate to students at this level is to begin the process of changing the way they view ascent rates. We move them from the concepts of getting up quickly, ie; 60fpm to slowing down there ascent to 30fpm. We then walk them through why incorporating deep stops is a good idea, as opposed to what most have been taught which is that by slowing the ascent down you are not on-gasing, We then move them off of 3 minutes at 15' and into a 30',20',10' viewpoint. We discuss RGBM -v- Buhlman so I guess I'm confused what you'd like to see added. The teaching paradigm we use is very much a building block approach, and by building the blocks the way we do it seems to have been a productive approach.

The other thing to consider on your point respecting "GUE confusing the issue" is that our goal has always been multi-faceted, in that we like to address how the industry teaches it, how we teach it for purposes of comparing and contrasting, and then most importantly the WHY's behind it. I don't see offering a variety of ways to approach the issue as confusing it. I like to give students more credit then that, in that we're not trying to train robots, we're trying to train divers to think and show them that once you understand the mechanics behind the approach there may very well be more then one way to do it. Perhpas it's a little more then semantics, but I believe at the end of the day the picture we are trying to fill in is the shape of the curve, and the tools needed to be understood to create your own shape. I hope everyone recognizes that point.

Let me know if that clarifies the point.

Later

 

[Charlie99]

What hasn't been addressed is the relative merit of the different ascent profiles.

In the doppler study done by DAN (8 different ascent profiles from a 25m 25min dive followed by 25m 20 minute repetitive dive) the 10fpm linear ascent comes out as the worst possible ascent even though it is not the shortest total time to ascend, and at least one of the GUE recommended ascents is pretty much a stepwise approximation of that same linear ascent (after the initial 30fpm ascent to 80%ata).

The fixed stops on the www.dir-diver.com website better match my understanding of the proper shape of deco, they better match what you get out of various deco programs by cranking up the conservatism very high, and the better match the profiles with low bubbling on the DAN study.

To me they look like that is a much better way of "doing it right", even if others post that it isn't DIR.

 

[boomx5]

What hasn't been addressed is the relative merit of the different ascent profiles.

To me they look like that is a much better way of "doing it right", even if others post that it isn't DIR.

No one ever said they were not DIR. I still think you are missing what Mike was saying Charlie. Furthermore, I think trying to get the answers you seek off of the internet is a less than optimal way of satifying your curriosity...IMHO.

 

[Charlie99]

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

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

Independent of the creative math, in the recreational range of depth and times, the 50' off of max depth appears to be a better rule of thumb as the place to slow the ascent from 30fpm to 10fpm.

 

[Charlie99]

No one ever said they were not DIR.

I must have misinterpreted Soggy's statement "For the record, these tables are not DIR." on thescubastop.

His post in the Safety Stops thread "They are not considered the DIR approach to minimum deco, regardless of his affiliations, and that fact has been stated here by more than just me, I believe." can indeed be interpreted as merely meaning the overall table approach being not DIR.

The reason I started this thread was to determine whether his depiction of the GUE taught ideal ascent profile was accurate, or whether is was a case of an enthusiastic DIR-F graduate passing along mistaken info.

Comments as to the relative merits of the dir-diver approach (slow to 10fpm at 40', further slowdown shallow with 3 min stops at 20' and 10') vs the 10fpm all the way to the surface approach would be greatly appreciated.

 

[lamont]

it seems like a major problem with this discussion is that people are overly focusing on a given schedule and not the principles behind deco. people are taking the deco schedules way too literally...

 

[boomx5]

I must have misinterpreted Soggy's statement "For the record, these tables are not DIR." on thescubastop.

Yes, I have read what Soggy wrote. However, just because they did not teach it in a 2 1/2 day class doesn't mean it's not DIR. There are a number of ascent profiles that would make sence in the DIR scheme of things, however they may not be taught in a fundamentals class. I think the misinterpretation here is that GUE teaches one and only one ascent profile and that that way is the ONLY way to "Do It Right"; and to fixate on this without understanding the big picture is going to leave you wanting. I assure you it is very simple, but there is just to much to discuss on a message board...unfortunately.

 

[CRDiver]

I believe some of the confusion with different profiles is the result of people spending too much time focusing on how dogmatically GUE handles gear configuration, and expecting the same out of ascent/descent profiles. Some people (including many over-anxious newbies) are attracted to the DIR philosophy because it gives clear-cut and definitive answers to practical questions related to gear, emergency procedures, safety procedures, etc., with little room for dissent within the community. When it comes to questions of decompression and physiology, there really aren't definitive and clear-cut answers yet (as GUE readily admits), only various recommendations based on scientific measurements and observations which are subject to change, unlike which side to sling a deco bottle or wear a canister light.

 

[Spectre]

I thought we were making real simple by saying:

"Start your deep stops 50' from max. depth and do 30 second stop, 30 second move until you hit 30'". I'm not sure how much simplier we can make it.

Well first off the confusion is the lack of consistancy, with different instructors giving different statements. Yes, that is simple... sort of. I mean, even this itself is confusing. i.e. you talk of 30 second stops, 30 second moves, and then you talked about 1 minute stops at 30, 20 and 10.

Well, technically a stop is the time you arrive at the stop to the time you arrive at the next stop. So a '1 minute stop' vs. '30 second stop, 30 second move' really -is- the same thing, with two different terms being used.

So the confusion still gets propagated with some people interpreting that as 1 minute stops every 10 feet from 50 to the surface, while others may interpret that statement as 1 minute stops every 10 feet from 50 to 30, then 1:30 stops from 30 to the surface [1 minute stops, 30 second moves].

Now then it gets even -more- confusing when you compare that with the DIR-F lecture that discusses 1 minute from 100 to 70 with a pause at 70.

So as you see... there is different things being said, and while yes... they are all conservative enough to be perfectly fine; they definately confuse people as not every one with the same training is on the same page.

I can't tell you how many times I ask a student to compute how many ATA's at 100', and all I get is blank stares.

That is definately the most disturbing thing I've heard in quite a while. ATA to Depth and Depth to ATA is a skill that is taught in OW class. In a Fundamentals class, which is, as I understand it meant to teach students the fundamental skills that they -should- have learned in their OW and AOW programs, I can't believe that you can just brush off the anability to make such calculations; let alone -require- it to be done.

When is it that they are taught that skill? In tech 1? When they have quite a bit more task loading that they to focus on?

But ok... let me hypothetically assume that I accept that disability as acceptable. So how about tell them to pause at 75% of their depth, and start their stops at 50% of their depth, or 30 feet; whichever is deeper. That hits them pretty close in recreational depths, gets them familiar with making those calculations, and considering they damn well better be able to learn how to divide their tank pressure by 3, I don't think it's much to ask to expect them to be able to divide their depth by 4.

We move them from the concepts of getting up quickly, ie; 60fpm to slowing down there ascent to 30fpm.

I think if you look around, you will find that 30fpm ascents are what is being taught. There are some threads on other boards that asks specifically 'what ascent rate were you taught, and what methods were you taught to gauge that'. There were quite a few that were very surprised to learn that my OW book [(c) 1999] still stated 60fpm. I would be quite surprised if you found many DIR-F students that weren't already running 30fpm ascents, if not aware to some level of 'slower ascents' and 'deep stops'.

I like to give students more credit then that, in that we're not trying to train robots, we're trying to train divers to think

See... that's exactly the point I'm trying to make. You say you like to give students more credit, but in the same post you don't expect them to able to convert depth to ATA and knock off 20%, or even to be able to take 75% of their depth.

You speak of building blocks; but you don't seem to think that teaching them to be aware of the depths where later you will expect them to be able to not only calculate but calculate ascent profile changes at. Don't you think a better building block to learning to be aware of a curve shape is to start getting them used to the points on the curve, rather than giving them a linear ascent for 50 feet, and then another linear ascent for the rest?