Advice needed for Suunto Vyper: switching from gauge to air modus impossible?

[vicky]

or just rumors? Where have you heard aobut it?
Anyway, O2 half time is considered to be 90 minutes, so if you don't do more than one deco dive per day, or wait about 7-8 hours between two deco dives, there shouldn't be a cns tox problem, isn' t it?
I usually do deco dives planned with V-planner, and Vyper comes along and I must confess that many times Vyper clears me up before the original V-planner stops. Perhaps it is because of the slight differences between plan and actual dive? Although I try to stick to original plan and runtime, I usually start ascending 1-2 minutes ahead of schedule and Vyper clears me up sooner...

 

[MechDiver]

vicky once bubbled...

I usually do deco dives planned with V-planner, and Vyper comes along and I must confess that many times Vyper clears me up before the original V-planner stops. Perhaps it is because of the slight differences between plan and actual dive? Although I try to stick to original plan and runtime, I usually start ascending 1-2 minutes ahead of schedule and Vyper clears me up sooner...

Might I inquire what type of profiles you are diving for your deco dives? I can't imagine a Suunto not getting bent, let alone letting you out of the water before a properly setup V-Planner profile.
Just curious.

MD

 

[vicky]

A 50m dive for 12 minutes. V-planner set on +2 conservatism and planned on air:

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Altitude = 0m
Conservatism = + 2

Dec to 50m (2) on Air, 18m/min descent.
Level 50m 9:13 (12) on Air, 1.25 ppO2, 50m EAD
Asc to 18m (15) on Air, -10m/min ascent.
Stop at 18m 0:48 (16) on Air, 0.59 ppO2, 18m EAD
Stop at 15m 2:00 (18) on Air, 0.52 ppO2, 15m EAD
Stop at 12m 2:00 (20) on Air, 0.46 ppO2, 12m EAD
Stop at 9m 4:00 (24) on Air, 0.40 ppO2, 9m EAD
Stop at 6m 4:00 (28) on Air, 0.34 ppO2, 6m EAD
Stop at 3m 9:00 (37) on Air, 0.27 ppO2, 3m EAD
Asc to sfc. (37) on Air, -10m/min ascent.

Off gassing starts at 29.4 m


I hit bottom after 3.5 minutes,started ascent after 12 minutes (from dive beginning). The Vyper cleared me up at about 9meters after 23 minutes from dive start.
BTW, my Vyper asked for a ceiling of 4.2meter, which pretty fast went up to 3meters and 2.4meters, while original V-planner plan asked for deco stops from 15meters (I use a 1minute 18m stop to switch to deco gas).

 

[Genesis]

This last Saturday I did the dive that I posted on the other Vytec thread.

15 minutes bottom time, 140 (137' actual), 28% Nitrox.

The Vytec had a 10' ceiling - it never moved it down from there.

VPlanner (VPM-B; the current version) calls for 1 minute @ 30', 3 minutes @ 20', and 7 minutes @ 15' (I set the "last stop" to 15' since that keeps me out of the surge zone, and I dive it with conservatism set to +2.)

My total deco obligation on the Vytec was listed as 8 minutes at "maximum exposure", and 3 of that is their "safety stop", so the total deco obligation I incurred was for 5 minutes (according to the Vytec.) By the time I reached 35' on the actual ascent I was "clean" according to the Vytec (I made a deep stop at 1/2 depth for 1 minute.)

People SAY the Suuntos are "famously conservative", but as with most of the BS that flies around that simply isn't all that true when you start comparing against planned-dive tables cut on "deco planning" software.

The Suunto definitely gets you out of the water first compared to something like V-Planner.

 

[Scuba_Vixen]

Just when you find a quirk that makes them mega conservative under a given situation, then you find them to be almost scarey liberal in another, (I think i'd opt for the false indication of being toxed more than for really being bent) That kind of overall inconsistancy would make it useless by my reasoning. Sheesh, ...

Karl, can you make it tox you out AND bend you all in one dive?

I'm beginning to be a Puggett, they really may rot your brain.

Darlene

 

[Genesis]

But I've taken to running profiles on VPlanner before doing any deep dives (anything over 100-110') or anything where I INTEND to go into Deco on the Suunto, and filing away what VPlanner tells me in my brain.

I do that for two reasons - the computer may fail during the dive (that would stink if I had a deco obligation at the time!) and as I "slide" more towards technical-style diving, I'm very interested in the actual safety factors involved in doing it both ways (computer .vs. table.)

The computer's apparently liberal approach isn't, by the way, nearly as bad as it looks, since there really is no such thing as a "square profile", and small differences in depth make a big difference. For instance, the actual maximum depth on that dive was 137'. You'd plan it was 140, but the fact is 137 was max depth reached, and the actual "bottom average" was right around 130ish.

Also, VPM-B doesn't call for deep stops. But I do 'em and believe in 'em, and that extra minute above the offgassing ceiling does help your overall deco profile.

When you recompute for the ACTUAL average bottom depth and time, you get pretty close results between VPM-B and the Suunto. VPM-B now demands a first stop @ 30', and that's for less than a minute. The 20' stop is 1 minute, and the 15' stop is now 6 minutes.

This is why computers are useful, despite the Pugnatious derision that many serve up. Using tables - now matter how you cut them (e.g. pre-printed ones or ones you cut on a computer at the time) is an inherently conservative act, as few dives have anything approaching a true square profile.

The one complaint I have with Suunto in this regard is that their "ascent time" includes the "safety stop", which is cool, but once you clear mandatory deco they still claim the "safety stop" is advisory. THAT is a problem from where I sit, and accounts for most of the difference in terms of the computer being more liberal.

In fact, omitting the "safety stop" that the Vytec wanted me to do on that dive would have left me "off the charts" on VPM-B even with the conservatism set to ZERO!

So for those who dive a Vytec (and probably the Vyper or Cobra, as their deco computations appear to be nearly if not absolutely identical, assuming no gas switches) if you consider the "safety stop" on any deco dive to be MANDATORY and not advisory you end up with a profile that looks pretty much like VPM-B. If you also incorporate a deep stop with VPM-B, though, you have a problem as VPM-B has no provision for it (at least, none that I can find in the config or help files!)

 

[MechDiver]

Scuba_Vixen once bubbled...
Just when you find a quirk that makes them mega conservative under a given situation, then you find them to be almost scarey liberal in another

I'm beginning to be a Puggett, they really may rot your brain.

Darlene

I think the profiles here are borderline to the Suunto's capability. At least what little I have played with them. I was looking very strongly at the Vytec for good recreational/light deco computer to replace my old air units. Using their dive planning software for dives to 130 ft for 30 to 40 minutes showed the computer was not capabile of doing those dives. It would not allow you to do either deep stops or controlled ascents without apparently going beserk. Again, this is with the simulation software and not the unit itself.
Most of my dives now are on mix, so the Vytec is irrelevant, even if it does have gauge mode.

Vicky, thanks for posting that profile.

MD

 

[Genesis]

deep stops and controlled ascents.

I have actual "light deco" dives on it in which it behaves quite rationally under such circumstances. Provided you are above the offgassing floor, a deep stop doesn't hurt your overall deco profile on the Vytec (you should be - otherwise its not really a deep deco stop!)

 

[MechDiver]

Genesis once bubbled...
deep stops and controlled ascents.

I have actual "light deco" dives on it in which it behaves quite rationally under such circumstances. Provided you are above the offgassing floor, a deep stop doesn't hurt your overall deco profile on the Vytec (you should be - otherwise its not really a deep deco stop!)

How do you define "light deco"? The dive I remember planning was to 130', 30%, for 30 or 40 minutes. This should involve a stop at 100', and every 10' after that if I remember correctly (don't have V-P with me), with gas change at 70' using 50% for deco. The simulation software wanted me at 70' immediately after leaving the bottom, and would not accept any stops below that. Again, maybe the actual computer would do this differently.
I didn't care enough at that point to pursue the issue any further.

 

[vicky]

MechDiver once bubbled...

Using their dive planning software for dives to 130 ft for 30 to 40 minutes showed the computer was not capabile of doing those dives. It would not allow you to do either deep stops or controlled ascents without apparently going beserk. Again, this is with the simulation software and not the unit itself.
MD

Can you explain better why the computer goes "beserk" or does not allow you to do these dives?
Although Suunto's computers do not have any integrated "deep stops" feature, they keep monitoring throughout the dive the nitrogen uptake. This includes everything that you do in your profile. If you stop at 20meters for two minutes, the computer will take that into account, most probably clearing a bit of your fast tissues N2 loading. If you stay longer, you'll may load your medium tissues and thus get no benefit from the stop- delaying the ascent too much is not a good thing. Simulation (and computer itself) cannot forbid you a stop at 100' or force you to ascend to 70'. You can do that in your dive, the CEIL will get updated according to your actual diving profile. What's wrong with that?
Most planning softwares will tell you at which depth you start offgassing, in Suunto's SDM you can follow the tissue graph and see its behaviour. You can play and modify the profiles to see how it behaves and I think one can learn to know better his computer's behaviour like this.

Anyway, I don't see and don't recall any problem with Suunto's computers on 40meter profiles to 30-40 minutes. Your main concern will be to have adequate gas supply for such a dive. The only situation I can foresee that Vyper will get beserk and do not allow you to make a 18-20m deep stop is IF you make a too long bottom time that the CEIL (first deco stop) will be BELOW 20meters (70'). In this case you'll be probably in deep **** anyway regardless of what computer you're wearing on your wrist... If you understand what I mean...

I don't see any case where the CEIL in Suunto's computer will overrule those prepared by V-planner. From my experience V-planner stops start deeper than those of the Vyper. That is- of course- if you dive your plan. If you have both softwares (SDM Vplanner) you are invited to compare them with square profiles as much as you like- you'll discover that Vyper is more liberal and less conservative than what you previously thought. That's why I like Vplanner- conservatism!
IMHO computers that are more liberal than a Vyper should be considered potentially dangerous and not used for other purposes than rec diving. I'd stay with them at least 3-4 minutes AWAY from NDL time, and by all means avoid using them for deco dives! In multidive scenarios such as a Safari I'll take more precautions from a liberal computer. That is, if you want to get home safely...