Deep Stops - Suunto Cobra

[beachnik]

Several Suunto models have a feature that provide prompts for deep stops. I've got the Cobra and it's not one of those models.

I've only read briefly about the feature on the Suunto site. And read briefly that those computers use 'the new Deep Stop RGBM'. I presume that's a modification of the old RGBM algorithm.

I've read enough elsewhere to start thinking that deep stops might be a good idea.

So, let's assume I start doing deep stops while diving with my Cobra - does the Cobra calculate any benefit from it? I would think not.

 

[bleeb]

From what I've read, there may be an indirect benefit.

It seems it's not so much a modification of their algorithm as an addition. The basic on-gassing/off-gassing and bubble modeling is supposedly unchanged, but an extra timer is thrown on the display when you ascend to where it thinks a deep stop is appropriate. (The computer model may still be accumulating nitrogen during this time, at least for some compartments.) Where the indirect benefit may come in is the fact that RGBM is a bubble model, and bubble models are sensitive to ascent rates, and possibly the amount of time spent at intermediate depths to allow the number and size of microbubbles to shrink.

This is also a basic premise of the benefits of deep stops in recreational NDL diving in general, regardless of whether you're using a computer which explicitly shows it or not.

 

[DA Aquamaster]

Way back when the Wisdom was young, I did deepstops with it and noted that a mild deco obligation would often clear during the deep stop or shortly after, so it is at least not penalizing you for taking a deep stop. I'd argue that is more important than giving you credit for the deep stop - you are after all doing a deep stop in recreational diving to get more safety and conservatism.

My understanding is that the Wisdom and Cobra are the same computers, just with minor differences in the displays and buttons.

 

[beachnik]

Thanks guys.

I've been reading the pro and con articles about deep stops for some time. Thought I'd give it a try. Yes, I have seen the article in Alert Diver which refers to the Navy's 2008 presentation at UHMS - interesting.

Anyway, more to the point, I was hoping for an added bonus. I like diving in such a manner that my computer is not scolding me. No matter how hard I try, it's nearly impossible for me to stop my SUUNTO from giving me an interval 'warning' at the end of the first dive on the second day of a multi dive trip. It's not just me, this is a common problem that you can see reported here on the board - SUUNTO users that is.

I know the various things that cause SUUNTO to decide that I've pushed the microbubble envelope too far. Not pushing the envelop is really hard. I kinda like the SUUNTO, so I'm not ready to ditch it.

The SUUNTO recommendation is to extend your surface interval - easier said then done when you've just come up from Columbia Deep, you've motored 20 minutes over to Columbia Shallow and all the Oceanic computer users are geared up and giving you that look 'What, you want to extend the surface interval, what the ____(?) - see ya later, we're going in'. Even an hour interval is frequently not enough to satisfy SUUNTO.

It's a little tough to eliminate some amount of 'saw toothing' from a reef tour. And it's damn difficult to not violate the speed barrier - 30 feet / min - at least once. So, I'm hoping I can do something proactively to reverse SUUNTO's anxiety.

I'll just give it a try.

 

[Jorgy]

There was thread on this before......tried to find it but was not successful.....

The Suunto triangle warning is due to residual nitrogen which as you point out is very hard to avoid as you progress with multiple dives......

You can start a dive with the triangle just know that it will impact your bottom time.....

How is your air consumption? As long as you clear the deco obligation prior to surfacing then your computer will be OK........

In the grand scheme, my sense is that a looonnggg safety stop after multiple dives is not a bad thing........

M

 

[beachnik]

There was thread on this before......tried to find it but was not successful.....

The Suunto triangle warning is due to residual nitrogen which as you point out is very hard to avoid as you progress with multiple dives......

You can start a dive with the triangle just know that it will impact your bottom time.....

How is your air consumption? As long as you clear the deco obligation prior to surfacing then your computer will be OK........

In the grand scheme, my sense is that a looonnggg safety stop after multiple dives is not a bad thing........

M

Thanks Jorgy.

I'm pretty sure I've found all the posts on this. And, I've thoroughly read the topic in the SUUNTO manuals. I've found quite a bit on the subject and feel I know it well enough.

Naturally, SUUNTO is not going to say - 'aw, just blow it off' : ). But that is what I and many other users have been doing.

My air consumption is very good. I'm a non-drinking, super-hydrating diet and fitness fanatic. If anyone is going to get bent, it'll be the other guy first. In fact, I've had one instance where my dive buddy dove the exact profile that I dove - 4 dives on our group's first day in Honduras. Both our computers said we were OK. My buddy ended up in the chamber every day for the next 4 days. I continued diving.

I also check downloaded logs for tissue loading - at the beginning of a dive, in the middle, at the end, and any subtle nuance that might give me a edge. That's looking in a rear view mirror, but it keeps me informed as to my general behavior.

In the end I think you're right. Maybe take a day off in the middle of a multi dive trip.

 

[bleeb]

Like you, I disliked that little warning triangle, and have kept an eye out for information over the years. Although you said you did a pretty thorough search, I'll risk repeating what you've may already found, and mention a few things to keep in mind.

One issue to avoid is raising the computer too fast to look at it, especially when shallow, or even reaching for your inflator a bit fast, if wearing the computer on your wrist. The thing is sensitive enough to misinterpret this as a fast ascent, which as noted, bubble models don't like.

Another thing is to take the last 5' of the ascent really slowly, even (or maybe especially) after the computer has switched to SI mode at 4'. I also wonder whether I once might have made it slightly unhappy with a long surface swim/drift, and the computer didn't like the apparent sawtooth with my arm bobbing above and below the 4' mark.

But the SI length is probably the most interesting one theoretically. Someone once posted on here that Doppler studies found a peak in detectable bubbles somewhere around 50 minutes after surfacing, and that most bubble models incorporated this by being sensitive to overall nitrogen loading and being prone to raise the warning flag until 60-70 minutes into the SI.

 

[beachnik]

As noted above, my interest in adding some conservatism to my dives was partially inspired by the 'ascent rate' alarms that SUUNTO was giving me.

I review all my downloaded dive logs, if SUUNTO tells me that tissue saturation is such-and-such, I accept it; if SUUNTO says my ascent rate is such-and-such, I accept it; if SUUNTO says my depth is such-and-such, I accept it.

For several years I've read the cautions about not moving your SUUNTO around too quickly. I was sure I wasn't doing that!

When 'bleeb' made the suggestion, I thought - OK, I'm going back into my logs with a calculator in hand and take another look.

Maybe I've been to naive. Anyway, assuming I've done the calculations correctly, here's what I discovered.

 

[sucnip]

One thing I dislike about the deep stops mode on my D9 is that when DS is switched on the 3 minute safety stop timer is deactivated. I think Suunto may intend for the Deep Stops to replace the 3 minute safety stop at 5 meters. I'd do both - and for this reason I keep DS switched off.

dp

 

[ickybingh]

Deep Stops aren't really about nitrogen loading/unloading. Think of them as Bubble Control Stops. Hmmm. That sounds good...Bubble Control Stops (TM). You heard it here first.

Anyway, if your Deep Stop is below the deco floor (meaning you're adding to your deco obligation), you will add to your total deco time; this is why you have the option of setting the Deep Stop time to 1 min or 2 mins. If you're doing deep deco diving, set the deep stop to 1 minute so you're not adding to your total deco. If you're doing deep recreational diving (non-deco), set it to 2 mins.