deep stop facility on a mixed gas dive computer

[jeremy gainsford]

I am just starting out on mixed gas diving to allow accelerated deco and am gathering equipment etc for the course.

My faithful Suunto Vyper doesnt allow for any gas switching and I am interested in the Apeks Quantum which seems to tick all the boxes and is a good price. However I note it does not allow you to set deep stops like th Vyper Air and I just wondered how important this facilty is. Anyone got any comments and experience with this dive computer?

[Nigel Hewitt]

...However I note it does not allow you to set deep stops like th Vyper Air and I just wondered how important this facilty is. Anyone got any comments and experience with this dive computer?
If you want to do deep stops you just do deep stops.
Some compartments in the computers model might still be on-gassing and the time goes up a bit but that's to be expected.

I tend to do slow ascents rather than deep stops but you have to allow for it in your gas plan if you're on OC.

[DarrenA]

Vytec DS (air/Nitrox) and Helo2 (air/nitrox/trimix) both do deep stops.

[Richard Whitcombe]

If you're going into accelerate deco/mixed gas its unlikely you're going to be using a computer (or 2) anyway at least initially so its not really a problem.

Vyper air etc insert effectively modified pile stops (not part of deco obligation) but accelerated deco diving most of the training revolves around planning in advance. I wouldnt bother - just make sure you have a computer that does gauge mode...and a spare.

[Paul S]

My faithful Suunto Vyper doesnt allow for any gas switching and I am interested in the Apeks Quantum which seems to tick all the boxes and is a good price. However I note it does not allow you to set deep stops like th Vyper Air and I just wondered how important this facilty is. Anyone got any comments and experience with this dive computer?

I know nothing specifically about the quantum, but I went through a similar decision process this year. I ended up with a Uemis, but reasons more about the display, and that one was being sold cheap rather than anything else.

Deep stops, as Nigel says, do them if you want to. The computers just seem to say "Do one here, for this long, if you want". Completely optional. I'm a fan of them, but working out where to do them (using Pyle's method) if your computer doesn't do them isn't rocket science.


Halfway between your deepest depth and the first deco stop, stop for a bit.
Halfway between that and the first deco stop, stop for a bit.
Keep halving the distance, until you're within 10 meters of your first deco stop. At that point just do your normal deco.

For example: If I've done a 30 metre dive, and I've got a deco stop at 6m. Halfway between 30m and 6m is 18m, so I stop at 18m for a bit. Halfway between 18m and 6m is 12m, so I stop at 12m for a bit. 12m to 6m is less than 10m so I just do my normal deco from here.

It's worth reading Richard Pyle's article on Deep Stops (http://www.bishopmuseum.org/research/treks/palautz97/deepstops.html). I think it's a lovely story of one man thinking "This makes me feel better" and sharing his new found knowledge.

[garethwoodruff]

I ended up with a Suunto Hel02, more so because i was maybe doing a deep dive amongst a week of shallower stuff and trying to work that off software such as v-planner was causing me to have headaches.

Its easy to drive and I appear to be coming off dives feeling fine. Mind you thats only 50 to 60 meter stuff with about 40 or 50 mins of stops.

You would be better getting a D-timer to go with your vyper, you can run off something like v-planner or whatever your software of choice is and use them so that when you get a computer and you have a better idea of what its doing and understand the mechanics better. After a year of that then think about a computer.

I'm not sure i would use the BSAC ox-stop tables to run dives off, they are reasonably aggresive. If i did use them I would definately add an additional 5 or 10 minutes of stops at 6 meters as a little insurance.

Is it the BSAC ADP couse you are doing?

Cheers,

Gareth.

[Turtle Dude]

I am just starting out on mixed gas diving to allow accelerated deco and am gathering equipment etc for the course.

My faithful Suunto Vyper doesnt allow for any gas switching and I am interested in the Apeks Quantum which seems to tick all the boxes and is a good price. However I note it does not allow you to set deep stops like th Vyper Air and I just wondered how important this facilty is. Anyone got any comments and experience with this dive computer?
Have a read of Deco for Divers - which is very informative and easy(ish) to read.

I would also consider a full gas-switching tri-mix computer (to go with your Vyper in gauge mode) which uses a model that incorporates deep(er) stops.

[Nigel Hewitt]

I would also consider a full gas-switching tri-mix computer (to go with your Vyper in gauge mode) which uses a model that incorporates deep(er) stops.
I know it's my own view, and it's considered a bit off the wall by some, but I would suggest a simple computer that doesn't lay more than the gas model's requirements on you.

Once you are doing mixed gas diving it is time to take responsibility for your own plan. Computers and tables are just there to advise you. I like computers, which is why I take two, but they are set to zero conservatism and I add extra time as I see fit. I have yet to see any description of a conservatism system that can say "our X% of conservatism in Y% safer", all you are getting is some programmer's guess as to how far you should stay from the bent/not bent line the model draws. Your guess is as good as mine and although I've been reading this stuff for years all I can say is that I think deep stops or a slow ascent are good while shallow, at 6 meters, the predictions of most models seem to be good enough to be used pretty much as is.

As I said I dive two computers from different manufacturers and my first move at any stop is to see both of them cleared for me to ascend and then I start to wonder how much longer I'm going to stay. However, I confess, I'm on a rebreather so my gas plan is pretty much my scrubber duration and I'm quite willing to admit that on OC this might be more problematic to implement. My 'OMG' bailout tables that tell me what my bailout cans can get me out of are based on a 100/100 gradient factor model and how close I go to their 'maximum time at depth' is another number I decide live on the dive.

OK. I know that's not at system we teach. The ritual burning of the heretic may now commence. I'm quite used to it by now.

[DarrenA]

I know it's my own view, and it's considered a bit off the wall by some, but I would suggest a simple computer that doesn't lay more than the gas model's requirements on you.


Agree with this but that doesn't mean you shouldn't have one thats fancy anyway :)

Diving mixed gas/accelerated deco should be treated like your first Ocean Diver dives i.e. Plan the dive, dive the plan.

Your slate(s) should have the plan and a backup plan. Always.

Have computers to tell you dive time and depth or dive a depth gauge and watch, but don't plan to rely upon the computers for deco obligations on the fly.

We use the Suunto's because thats what we use (i know some people hate them). We use the Dive Planning software from Suunto so we can plan it and the slate nearly always matches the computer in reality. We dive two computers each.

We only ever dive the computer if we go over the slate (never done it, but the theory is there) or we cut the dive seriously short so no point in doing 80 minutes deco for a dive we didnt complete.

Using the same software as the computer you will dive makes sense to us too.

So in summary, every deco dive is a slate dive (pre-planned, agreed and calcuated on the surface). Computers are there as a backup to that slate.

All non-deco diving is done on the computer.

Imho, jumping in to do a deco dive and then relying on the computer to tell you what stops to do on the fly is crazy. What gas planning would you have?

[Woz]

I have a VR3 and a Quantum. On a mix dive, the VR3 puts in Pyle stops and the Quantum just ticks away merrily while you do them. When you get shallow, the Quantum is within a hair's breadth of the VR3 for the deco, even though there's no helium setting on the Quantum.

Nitrox diving there's no real difference between the 2.

What works quite well so you don't end up endlessly generating backup plans is doing a bunch of slates with the same runtime. For example, I mostly use mix in the 40-50m range so have pages in the wetnotes already marked up.

[PeteM]

I have a VR3 and a Quantum. On a mix dive, the VR3 puts in Pyle stops and the Quantum just ticks away merrily while you do them. When you get shallow, the Quantum is within a hair's breadth of the VR3 for the deco, even though there's no helium setting on the Quantum.

Nitrox diving there's no real difference between the 2.

What works quite well so you don't end up endlessly generating backup plans is doing a bunch of slates with the same runtime. For example, I mostly use mix in the 40-50m range so have pages in the wetnotes already marked up.

Pretty much what I do (with the exception of a Vytec DS instead of the Quantum), Vytec take a few minutes more to clear than the VR3 but by that time I don't care

[Kris2]

I am just starting out on mixed gas diving to allow accelerated deco and am gathering equipment etc for the course.

My faithful Suunto Vyper doesnt allow for any gas switching and I am interested in the Apeks Quantum which seems to tick all the boxes and is a good price. However I note it does not allow you to set deep stops like th Vyper Air and I just wondered how important this facilty is. Anyone got any comments and experience with this dive computer?

get the suunto Helo2, virtually the same to use as the vyper air except gives you 8 changes.gives .

[Dave Whitlow]

When I went did my ART course I went for a VR3 with my suunto as depth timer. Moving to normoxic I opted for a VR3 on each arm (still cheaper than a new Trimix computer) and gives adequate redundancy. I still used my Vyper to record the dive (and because I can the numbers better for simple stuff like depth).

With the VR3 you can use the Suunto Dive Planner (set to P-3) to plan the dive and do the gas calculations and play lost gas games. There will be a slight difference in depth of the deep stops but otherwise it works. Note that the VR3 will sulk if you don't do the deep stops whereas other computers just recalculate and might penalise you a bit.

Past tense now as I traded up one of the VR3 to a Vision :D

[jeremy gainsford]

Thanks guys - that is all really helpful stuff. (Its the first time I've used the Forum and I'm very impressed how quickly and helpfully everyone responded. i will definitely be posting again especially after I start the BSAC ADP course which is bound to raise further questions! jeremy

[Twinsetmad]

I'm really surprised nobody had mentioned the OSTC mk2...

http://www.deep-ideas.co.uk/OSTCII.html

This is a proper mix computer with proper deep stops and runs gradient factors. Its far more predictable than any of the Suunto's... Its the same price as a Helio2 and the screen and functionality can't compare. Ask Nigel, these are probably the best value for money computer available at the moment. :)

[Nigel Hewitt]

This is a proper mix computer with proper deep stops and runs gradient factors. Its far more predictable than any of the Suunto's... Its the same price as a Helio2 and the screen and functionality can't compare. Ask Nigel, these are probably the best value for money computer available at the moment. :)
Hey I can't talk about anything but the hardware because I bought it as a program-it-yourself box.
I had just had enough of other people's idea of what a user interface should be.:rolleyes:

Love that OLED display...

[Nick of Bristol]

I also use a quantum and have recently added a VR3.

I have been happy with the quantum as the display is easy to understand, and it was only £150 at the dive show.

It also has a lifetime gaurantte, but make sure you register it as they can go wrong.

The only irritation with technical diving to pre-determined run times is that the the run time was not displaced one you go into deco, and you have to press a button to see it – grrh !

That said, I would say that it is hard to beat a quantum for the money.

Happy shopping;)