Tale of 2 computers on 2 dives

[Bubbletrubble]

Deepstop set to OFF

OK. So you turned off the "Deepstop" setting on your Vyper Air...even though you planned to do a profile that contained a deep stop. Why?
I don't think I understand the point of your experiment. What was the objective?

Ascend at 33f/min or faster. There is a lot of space between 33 and 60

Based on your comments, I think that Suunto must have implemented a slightly different prescribed ascent rate in its "newer" computers, like the Vyper Air.
My old Mosquito will register an ascent rate violation if the ascent rate ever exceeds 39 ft/min instantaneously or exceeds 33 ft/min "continuously" (regardless of whether you are in deco mode or not).
I realize that other manufacturers have implemented a "tiered" prescribed ascent rate schedule. For example, from a depth of 100 ft. to 60 ft., the maximum ascent rate allowed might be 66 ft/min, whereas from a depth of 60 ft. and shallower, the maximum ascent rate might be 33 ft/min.

 

[jar546]

From the manual:

WARNING YOUR ACTUAL ASCENT TIME MAY BE LONGER THAN DISPLAYED BY THE INSTRUMENT!
The ascent time will increase if you:

*remain at depth
*ascend slower than 10 m/33 ft per minute
*make your decompression stop deeper than at the ceiling

These factors will also increase the amount of air required to reach the surface.

 

[Bubbletrubble]

From the manual:

WARNING YOUR ACTUAL ASCENT TIME MAY BE LONGER THAN DISPLAYED BY THE INSTRUMENT!
The ascent time will increase if you:
*remain at depth
*ascend slower than 10 m/33 ft per minute
*make your decompression stop deeper than at the ceiling
These factors will also increase the amount of air required to reach the surface.

My Suunto manual says the same thing.
Under the section regarding ascent rate...
It states that an ascent rate violation will occur if the ascent rate exceeds 39 ft/min instantaneously or 33 ft/min continuously.

That's why I really didn't understand your comment in Post #10 of this thread:

Ascend at 33f/min or faster. There is a lot of space between 33 and 60

You seem to be implying that, once deco mode is entered, your Suunto computer is instructing you to ascend at a rate of 33 ft/min - 60 ft/min. My Suunto doesn't do that.

 

[jar546]

I don't think it is instructing you to ascend at 33-60 but if you don't it adds deco time.

 

[Bubbletrubble]

I don't think it is instructing you to ascend at 33-60 but if you don't it adds deco time.

Sorry if I'm sounding a little dense here...
Where are you getting the 33-60 range?

 

[jar546]

It says if you ascend slower than 33 you will get added deco time.

60 is the max safe ascent rate for diving in general.

 

[Hatul]

@jar546: Perhaps that was a typo. I see nothing in my Suunto manual which instructs a diver to ever ascend faster than 33 ft/min. That would result in an ascent rate violation on my Mosquito.
I would think that one should ascend to just below the ceiling at a rate very close to 33 ft/min in order for the minimum ascent time not to increase.

As you know, the Suunto will react differently if you initiate ascent before crossing over into deco mode. It will increase NDLs as you ascend regardless of rate, just as the Luna did on Dive #2.

The Luna supports Profile Dependent Intermediate Stops (a.k.a. "level stops" that allow on-the-fly cascading to lower levels of microbubble protection).
The latest iteration of the Suunto Vyper Air supports a Deep Stops option. Did you have this option turned "ON" on your computer?
Or perhaps you have an older Vyper Air which lacks the Deep Stops option?
Just curious.

Hi Bubble, I just want to correct what you wrote. The Profile Dependent Intermediate Stop, PDIS, is Uwatec's version of an improved deep stop. It's just above the depth at which you just start to offgas the leading compartment.

The Level Stop is different. It's an optional stop which is only set if you set the MB level above 0. The level stops tend to be shallow like deco stops and PDIS are deeper. You can control each of these separately and you're not penalized for missing either. If you miss a Level Stop your MB level gets decreased.

Adam

 

[Bubbletrubble]

60 is the max safe ascent rate for diving in general.

@jar546: So, just to clarify, you are citing the 60 ft/min max ascent rate as a "generally agreed upon diving principle" (which is debatable BTW if it is meant to apply to all depths) and not something that was stated explicitly in the Suunto manual.

I don't think I agree with your interpretation of the Suunto manual. I could be wrong about this, but I think that, with respect to deco mode, the minimum ascent time displayed by Suunto computer assumes an ascent rate of exactly 33 ft/min. If the ascent rate is slower than that, the minimum ascent time would increase. If the ascent rate is faster than that (let's say 60 ft/min), the minimum ascent time might increase even more, depending on how fast the diver ascends. Based on my understanding of how my Suunto works, the 60 ft/min ascent would trigger an ascent rate violation which, in turn, activates a Mandatory Safety Stop (MSS) to account for behavior that increases DCI risk. As you know, the MSS is incorporated into minimum ascent time, so as the MSS increases in duration, so does the minimum ascent time.

@Hatul: Thanks for the correction on the Uwatec stuff. I've never used a Galileo computer that had those features. It seems like every manufacturer likes to tweak the deco algorithm, market it as a brand new innovative "safety" feature and, of course, attach a catchy proprietary label to it. And, frankly, based on the scientific research on human subjects published in peer-reviewed journals, I don't think the safety measures employed by the Uwatec's PDIS or MB have any proven usefulness. I suspect Uwatec paid a handful of divers to go diving in a fairly uncontrolled environment and then did some less than rigorous Doppler bubble detection. The results of any of this research is not reviewable outside the company at all. The rest of it is pure marketing. That being said, I do hope I'm wrong about this.

 

[Hatul]

I have the Vyper, which is much older than Vyper Air, and the Sol. I spent several days doing two dives per day using both computers. What I found was that on the first dive of the day the Vyper was more liberal, but on the second dive they flipped, the Suunto being much more conservative in their NDL times than the Sol. It's very likely that on the second dive the Suunto would give me a short deco at 10 ft ceiling while the Sol would just give me an optional Level Stop at 10 ft with the MB level set to L2. (L0 eliminates level stops and L5 is the most conservative).

Another point: Suunto recommends the 10 ft ceiling be done at 15 ft to make the stop easier and avoid ceiling violation, even though it's a little longer when done deeper.

Adam

 

[DiveNav]

jar546,
thank you for providing the logs of your dives in question.

The first thing we noticed is that your dives #129 and #130 are actually part of a series of 6 dives started the day before as the nitrogen loading at the beginning of dive #129 is not 0.
So, the first question I have is: did you use the Sol also the day before when you did the 4 dives #125 --> #128?

We used divePAL to analyze your dives and, as per image below, according to our middle of the road algorithm, while your dive in question (#130) was a bit aggressive, you did not get into deco (again - according to our algorithm); the highest N2 load you reached during the dive was 87% - lead by compartment #6 - and you surfaced with a nitrogen load of 78%.

I plan to repeat the analysis as soon as my engineers give me a version of divePAL that allows to change the conservativism of the algorithm (either more conservative - Suunto like, or more liberal - Oceanic/DSAT like)

​

Alberto (aka eDiver)