Practicing deco stops w/o going into deco

[SpeedyJ]

Yes but you've still exiting with the controlling compartment at the same GF. Not talking about pushing so deep into "deco" that you're adding a lot of additional dive time.

Sure, but the controlling compartment could be different, and the total nitrogen loading is different. Ascent rates matter.

I might be being pedantic, and perhaps you're right that it does not matter for the purposes of practicing deco, however saying they are equal just because you surface with the controlling compartment is at 50% of the M-value is just not correct. For someone just starting their tech journey I'd argue it is important for them to understand the implications of gradient factor choice and ascent rate has across tissue compartments.

 

[L13]

Sure, but the controlling compartment could be different, and the total nitrogen loading is different. Ascent rates matter.

I might be being pedantic, and perhaps you're right that it does not matter for the purposes of practicing deco, however saying they are equal just because you surface with the controlling compartment is at 50% of the M-value is just not correct. For someone just starting their tech journey I'd argue it is important for them to understand the implications of gradient factor choice and ascent rate has across tissue compartments.

In the exact scenario he specified, everything would be identical physically, because the dive profile would be identical if you applies all the qualifiers he specified.

If you just generically applied the idea you would be right.

Specifically noticed that he said "doing a "safety" stop and exiting with a GF of 50." A dive that had you surfacing with exactly 50% after a standard safety stop would have exactly the same profile as a dive on 30/50 that called out exactly a standard safety stop for deco.

You would be correct for any dive on 30/50 that called out any amount of deco other than a standard safety stop. In that case, the surfacing GF would be the same, but the individual tissue saturations would be different, and if it deviated enough, the controlling tissue would be different.

 

[grantmac]

I do NDL diving using 70/85 but plan to leave the water with a GF of <75 unless there is an emergency. I always run in OC Tech mode while monitoring SurfGF and GF99.

If I wanted to practice deco stops using my computer I'd just run lower GF.

Really you control what you want the computer to tell you and what work you want it to do. Especially when you have access to information like SurfGF and GF99.

 

[NitrogenSweater]

I do this very frequently. On any dive deeper than 50ft or so. Call me crazy...

I set my dive computer to the gas I am using, and set it quite conservatively, but not enough to trigger deco stops. This is my backup if there is an emergency.

Then, I bring a slate with a dive plan copied from a dive planning software like Vplanner. I set gradient factors very conservatively, between 20/20 and 40/40. I follow the stops that this plan generates.

If there is ever a concern, I can simply use the conservative settings on my computer, which will track a safety stop, but will NOT trigger deco (unless I plan for it to)

 

[stuartv]

I would like to practice deco stops without actually going into deco. I have thought of ways to do this, and the thinking is to set my main dive computer to very conservative settings (and thus trigger deco stops), whilst keeping my backup computer at normal settings. I would keep an eye on my backup computer to avoid going into real deco.

I have considered 2 options for a 30m dive on Nitrox 32

1) Settings my Perdix to very conservative gradient factors

2) Set my Perdix to air

Any considerations, inputs or better altenatives?

For context, I have CMAS*, AOW, RD certificates and amongst others Nitrox, Deep, Drysuit, Self reliant specialities. I have logged 190 dives, mostly in cold water. For normal dives, a use a BP/W setup with twinset. For solo dives and deeper/longer dives I also carry a 40cu stage bottle. Eventually, I could see myself moving into technical diving, But for now, I just want to be prepared for a situation where I get (unplanned) into a few minutes of deco.In particular, I want to familiarise myself with my dive computer in “deco mode”. Better to practice and not need it, than not to practice and need it.

Yours is a solid plan. Do both. GF 30/70 would be good. Or even 30/50. And set it to Air.

Also, shoot a bag at the start of your ascent, but don't hang on it. Reel it up as you ascend, but lock it off at each stop and hover next to it. Okay the line*, if you need to in order to prevent getting separated from it.

I don't know why everyone else posting here feels a need to make it so complicated or tell you to do something different that does not satisfy the goals you specifically stated.

*Okay the line == make an OK sign with your thumb and forefinger around the line, so you're not holding onto it, but it can't get away from you.

 

[tursiops]

Yours is a solid plan. Do both. GF 30/70 would be good. Or even 30/50. And set it to Air.

Set your backup computer to 95/95 nitrox, and your dive computer to air, even 30/30. Accumulate lots of "deco" according to the air computer, but stay NDL on your nitrox backup computer. Have fun.

 

[lermontov]

im not sure what it is you want to practice ? is it hitting your deco stops ? or switching your gas ? or are you prepping to do your Deco procedures course soon ?

you can write up on a slate and jump in and follow that without breaking any rules eg drop down to 30m -shoot a bag at 25m ascend to 21m for 2 min- 15m/ 2min 12m /2min 9m/ 2 min 6m /4 min

then do it again and add in a gas swap at 21 m and 6m ( use air )
then add in hose clean ups
then add in hand signals

that just a rough idea you can vary it a bit but once youve done your first run and can see your still inside your NDL then you can relax and keep practicing -get comfortable with each stage before adding new stuff


personally I wouldn't fiddle with any GF settings just use the computer to monitor time and depth and use the slate to pretend you have deco - that way your computer will give you an accurate reading on your NDL status

 

[SlugLife]

but the original poster also wanted to observe how his computer operates while in deco

If OP is feeling ambitious, he could always tie it to the end of a line and drop it down to 150ft, pull it back up, and go through the motions. Just make sure to do it very securely, and nowhere it might get entangled, or you might be without a computer.

 

[lermontov]

If OP is feeling ambitious, he could always tie it to the end of a line and drop it down to 150ft, pull it back up, and go through the motions. Just make sure to do it very securely, and nowhere it might get entangled, or you might be without a computer.

as long as he has another computer to measure real time -if he screws up and wants to surface he never sure where he's at deco wise (if any)

 

[rjack321]

The hard part about practicing stops like the OP is asking about is: 1) staying still when you need to and 2) MOVING when you need to. Beginning deco divers either bust their ceiling the second something goes wrong or they linger so long diddling with a problem or task that if you actually needed to do those X minutes of deco you'll run OOA.

All this watching your computer talk isnt really where the rubber meets the road in the real world