Nitek 3 its expensive but GREAT!

[Lost Yooper]

Since we're going to talk about me, I guess I have to speak up. I'll play along on these threads as long as attacks are left out -- we'll see how that goes, but I have my doubts. It doesn't matter much as this thread is way off topic now. Maybe I wasn't real clear in describing how I (repeat, I -- as in me), come up with a deco plan. That happens a lot because of the difficulty of communicating exclusively in written form.

OK, Ralph, I don't tweak Haldane type models for my deco. I don't even use straight Haldane models anymore. I used to do this prior to using planners such as Z-Planner, GAP, and V-Planner. I use to do what a lot of people here do -- used a dive computer and added in deep stops on my own. I've done the Pyle type stops too. Now I use V-Planner, which is based on VPM (closely resembles RGBM). I do tweak my schedules to increase the safety and to allow a bit of fudge. I do this on my own which is based on the type of diving environment I'm in and my own experience (post-dive fatigue levels, etc.). I also incorporate the very slow ascent from 20' -- which just makes sense if you understand bubble mechanics a bit. I do this because my past readings and discussions have lead me to believe this is a good way to do it.

I have stated several times, that no one should blindly do anything I have stated without a thorough understanding of decompression procedures and physiology. I just state how I do things and how I view the subject. By all means (PLEASE) go out on your own (I'm talking to everyone here) and do your own research. Read all those links I posted. Get on Tech Diver and Quest and ask guys like Irvine and JJ what they think. I've been talking with these type of guys for years now, and I still have a lot to learn from them. Maybe you will come to a different conclusion than I have.

Maybe I'm totally wrong in my approach to developing a dive plan and executing it underwater. I don't know, I feel like a million bucks after a day of diving. Maybe there's a better way. Uncle Pug and I have been discussing deco privately for quite a while now, and he has a slightly different way he approaches it. I don't think his way is wrong, because I think we share the same basic principles (deep stops, slow ascents, etc.).

I'm really interested in having a decent discussion on this topic, but negative posts are not fun and really don't add anything to the discussion. If someone doesn't like something said, ask for clarification or simply say "I disagree and here's why ...". I don't know why these things turn into an insult fest.

Let's try again. I'll start a post in the Tech section regarding deco procedures, so we can let this one go (as it's way off topic now).

Mike

PS. I apologize for any remarks I made that were disingenuous to anyone here. Sometimes, I just have a bad day in life.

 

[Waterlover]

To try to put this to rest simply. Wrist mounted computers are haldane based programs with no allowance to make any adjustments for correct deep stops( the new sunto uses RGBM). Deep stops are very important for controlling bubble formation. Most computers actually allow some bubble formation and then treat it at the shallow stops. Decopplan Vplan and others allow the educated diver to calculate appropriate deep stops to prevent any bubbles from forming. I hope this simplification helps.
Ken

 

[rcohn]

From Lost Yooper:

Primary Deco Plan as put out by V-Planner:

30’ 5 mins.
20’ 13 mins. O2

Well there is the V-Planner Deco Plan. Where are the deep stops?

OK, I look at that plan and I say to myself, I don’t like that. I want to start deco deeper, so I throw in a 15sec stop at 80’, 70’, 60’, 50’, and 40’ (these are likely unnecessary, but I would do them anyway).

Why can't a computer user throw in 15 second stops from 80 to 40 feet if he/she feels they're needed? What is special about tables and a bottom timer? The computer would accurately track the nitrogen loading while these additional stops were being carried out.

From Waterlover:

Decopplan Vplan and others allow the educated diver to calculate appropriate deep stops to prevent any bubbles from forming.

Please explain how/where V-Planner is calculating the deep stops? I don't see them in the plan above.

Remember the discussion here isn't about what the ideal profile is, it's about why computers are wrong for Deco diving. If the program you use to cut tables doesn't plan the deep stops, changing their depth and duration for each profile, and instead you throw in a series based on a rough guess, this isn't a distinct advantage of tables over computers. Any diver can throw in an extra set of stops, any diver can ascend slowly to the surface.

The tables (at least the example above) aren't teaching you what the proper profile is, you're learning it elsewhere and adding it to the plan. Table divers aren't automtically edjucated and computer divers aren't automatically ignorant. As new ideas make their way into deco and non-deco diving everyone needs to study multiple sources to learn the best/safest techniques and apply their tools intelligently.

Ralph

 

[Lost Yooper]

Originally posted by rcohn
Well there is the V-Planner Deco Plan. Where are the deep stops?

For this particular plan, V-Planner doesn't think deep stops are required. As I said in my post, I would add the stops myself as a safety factor for me. I don't doubt the planner is right, but I would add the stops anyway to ensure a slow ascent and to help prevent bubble growth down deep.

Why can't a computer user throw in 15 second stops from 80 to 40 feet if he/she feels they're needed?

They could.

What is special about tables and a bottom timer? The computer would accurately track the nitrogen loading while these additional stops were being carried out.

This is the sticking point regarding computers using the Haldane based models. They may view deep stops as on gassing rather than off gassing. That type of algorthm wants to get you shallow quickly. On the other hand, the Vyper (which uses RGBM) does not penalize you for slow ascents and deep stops if you chose to throw them in yourself.

Remember the discussion here isn't about what the ideal profile is, it's about why computers are wrong for Deco diving. If the program you use to cut tables doesn't plan the deep stops, changing their depth and duration for each profile, and instead you throw in a series based on a rough guess, this isn't a distinct advantage of tables over computers. Any diver can throw in an extra set of stops, any diver can ascend slowly to the surface.

I think I see what happened here. This particular profile (which I really just picked out of thin air), V-Planner doesn't think deep stops are required. When you start getting into deeper trimix dives, V-Planner will throw in deep stops starting at about 80% of the profile (in ATA). I don't have to guess for those type of profiles, the VPM algorthm calculates all of that. For other dives, where it says deep stops aren't required, I do them anyway as a fudge factor (because I realize the potential for bubbles to form deeper).

Another nice feature of V-Planner is that I can tell it to stop at a gas change for minimum amount of time. I use this feature for my 70' stop for my deeper dives. When it calculates a profile, it tells me to stay 70' for 5mins, and then it re-adjusts the intermediate stops based on that. That's something a wrist computer can't do and is a feature I really like.

The tables (at least the example above) aren't teaching you what the proper profile is, you're learning it elsewhere and adding it to the plan.

Kinda. I think that the 100'/60min profile it spit out is probably fine. I would simply choose to add the short deep stops as a precaution. This is my own preference -- nothing more.

Table divers aren't automtically edjucated and computer divers aren't automatically ignorant. As new ideas make their way into deco and non-deco diving everyone needs to study multiple sources to learn the best/safest techniques and apply their tools intelligently.

I agree. I always quanitified my statements by saying many divers (not all) who use computers don't take the time to learn form those multiple sources. Many don't even know who or what the sources are. Some do know, but don't care to learn and rather put all of their trust into their expensive computer. This is what I, and I think others, are referring to.

Thanks Ralph.

Mike

 

[rcohn]

That makes more sense. When computers improve incorporating more advanced algorithms and the cost drops allowing redundancy I think the balance will shift in favor of computer use.

I want to correct one widely held misconception. The Suunto RGBM algorithm is only a partial implementation referred to as the SRGBM. It isn't a full bubble model but rather a Haldane computer with additional conservatism added based on computations from the full RGBM implementation. The computer runs a standard Suunto 9 compartment Haldane algorithm and reduces non stop limits or increase deco stops for a variety of factors. No deep stops, no reduction in deco stop times except as consistent with any predicted dissolved gas elimination that occurs during them which all computer do.,

From the Mosquito manual:

"It is a significant advance on the classical Haldane models, which do not predict free gas (microbubbles). It incorporates consistency with real physical laws for gas kinetics. The advantage of Suunto RGBM is additional safety through its ability to adapt to a wide variety of situations. Suunto RGBM address a number of diving circumstances outside the range of just dissolved gas models.

 Monitoring continuous multiday diving
 Computing closely spaced repetitive diving
 Reacting to a dive deeper than the previous dive
 Adapting for rapid ascents which produce high micro-bubble (silent-bubble) build-up.

SUUNTO RGBM ADAPTIVE DECOMPRESSION
The Suunto RGBM algorithm adapts its predictions of both the effects of micro-bubble build-up and adverse dive profiles in the current dive series. It will also change these calculations according to the personal adjustment you select.
The pattern and speed of decompressions at the surface is adjusted according to micro-bubble influence.

Also on repetitive dives adjustment may be applied to the maximum allowable nitrogen overpressure in each theoretical tissue group.

Depending on circumstances Suunto RGBM will adapt the decompression obligations by doing any or all of the following:

 Reducing no-decompression stop dive times
 Adding Mandatory Safety Stops
 Increasing decompression stop times
 Advising an extended surface interval (Diver Attention Symbol).

DIVER ATTENTION SYMBOL - ADVICE TO EXTEND SURFACE INTERVAL
Some patterns of diving cumulatively add a higher risk if DCI, e.g. dives with short surface intervals, repetitive dives deeper than earlier ones, multiple ascents, substantial multiday diving. When this is detected in addition to adapting the decompression algorithm Suunto RGBM will in some circumstances also advise with the Diver Attention Symbol (review chapter 3.2.3.2.) that the diver extend the surface interval."

It is clear from the manual that this computer adds several new conservative features to increase safety. However, I wonder how much safety is added, no indication of the magnitude of the increase is provided. Some restrictions may be excessive, for example, the recent conclusions of the Workshop on Reverse Diving Profiles was that reverse profiles (limited to a 40 ft difference) do not pose an additional risk to divers, so this restriction may be unduly conservative. More advanced versions of the RGBM (such as the Abyss implementation) include features such as deep stops for faster safer decompression. There is no indication that deep stops are included in the SRGBM version.

From Wienke:

"Generally, for short nonstop air diving, the RGBM reproduces the Spencer limits. For multidiving in spans shorter than 1-3 hrs, the RGBM reduces nonstop limits by 10% to 20% depending on surface interval, depth, altitude, and duration of present and previous dive, Multiday diving is impacted to lesser degree. Some comparisons appear in Table 8 for 3 days of repetitive air diving (120 f sw/10 min twice a day with 45 min surface interval). Computer choices are illustrative, not indictive.

Table 8. Nonstop Limits For VYPER/RGBM And Haldane Air Multidiving

Computer/Algorithm Dive 1 Dive 2 Dive 3 Dive 4 Dive 5 Dive 6
NDL (units) (min) (min) (min) (min) (min) (min)
VYPER/RGBM 10 6 9 5 9 5
SPYDER/Haldane 10 9 10 9 10 9
DATA PLUS/Haldane 12 6 12 6 12 6
DELPHI/Haldane 10 10 10 10 10 10
DC11/Haldane 6 6 6 6 6 6
DC12/Haldane 9 7 9 7 9 7
ALADIN/Haldane 8 8 8 8 8 8
ALADIN PRO/Haldane 10 7 10 7 10 7
SOURCE/Haldane 12 9 12 9 12 9

The VYPER/RGBM (first dive) nonstop limits (depth/time) are 150/6, 140/7, 130/9, 120/10, 110/13, 100/17, 90/22, 80/28, 70/36, 60/51, 50/69, and 40/120."

 

[pipedope]

In my own personal bias I prefer to have a chamber on site for all deco diving but each diver must choose and accept their own level of risk.
You can make a guess to how much deco diving I do. )

I must ask the question, "What treatment are the divers that are coming out of the water 'feeling crappy' seaking? The implication is that they are in type 1 DCS. Are any of these people going on O2 and heading to the nearest chamber?"

The thing I like about a computer is the running log of the dive profile. This can serve as a great cross check to the diver's memory of the dive profile. Blind reliance on any piece of equipment is a very bad thing and is likely to get anyone in trouble sooner or later.

Use your tools wisely.
Plan your dive and dive your plan.
Learn something new every day. I have been learning from this thread.

michael

 

[Lost Yooper]

Yeah, that exactly right about Suunto's algorthm, and is why I said I wouldn't use that computer for deco either. It's not a bad program for recreational divers, I think. I think it's a really good buy for divers, since it will do the nitrox functions for recreational diving, and it has the gauge mode if you get into the tech stuff. On top of that, the Vyper is only like $230-$250 which isn't killer bad either. I like it mainly for it's dive tracking and computer download ability.

Mike

As always, though, even recreational divers can benefit from taking the time to learn more than they were taught in their standard classes.

 

[Lost Yooper]

Originally posted by pipedope
I must ask the question, "What treatment are the divers that are coming out of the water 'feeling crappy' seaking? The implication is that they are in type 1 DCS. Are any of these people going on O2 and heading to the nearest chamber?"

michael

Hey Mike,

This is basically sub DCS (drowsy, sluggish, just kinda tired). It just means that you are bubbling pretty substantially, but not enough to warrant treatment. Some guys will go back into the water and do some more deco (but you'd best know what you're doing) if they feel bad, but most of the time it takes a while for the feeling to set in.

I've had this a lot when we were doing deep air diving. After a day of diving, you just feel like going to bed. It's not particulary good for you and not much fun. By avoiding deep air, using deep stops, using slow ascents, incorporating proper deco gasses, following a decent planner, being in decent physical fitness, staying hydrated, and avoiding post dive stress, you can virtually eliminate this sub DCS from ever occuring (at least that's been my experience).

Later.

Mike

 

[100days-a-year]

Ralph,nice chart....it doesn't really show any comparisons to anything other NDL and repetitive NDL tho.The dives being discussed are harder to quantify times for unless several divers share downloaded info.You're right in that unless real comparisons and info are being discussed,it's better to bite one's lip.......that works both ways tho....there is only the evidence of DAN's report available which suggests to me that a strict dependence on riding NDLs in modern computers is risky.....

 

[pipedope]

OK Lost Yooper, I will accept the judgment of the diver on the scene.
I say we each have the right to do what we want and we have the responsibility to know what we are doing.

Interesting stuff, now I have a couple more programs in my computer to use up my none existent spare time.
)

thanks

michael