The relevance of depth

[JonG]

As I embark on my rebreather odyssey, inevitably hours of training and familiarisation await but how much relevance does depth play in this evolution.

When I was diving oc in the 90s we did a lot of what used to be euphemistically called extended range, but was really deep air, we would therefore spend winters at depth in quarries building up skills but also allegedly improving our ability to resist narcosis, or so we told ourselves.

With helium mixtures in ccr being largely influenced by density with attendant low end's is there a need to practice skills deep with the increase in risks associated or is it better to dial skills shallow and then progressively extend depth operationally?

[Paulo]

The deeper you are with CCR the more things take care of themselves so to speak as the PO2 in the DIL gets your PO2 up easier. At 6m on an air DIL, you need a LOT of o2 to get to 1.3 SP and it is hard work. At 20m it is easier. At 40m easier again.

I find really shallow dives such as an hour at 6m whilst using the unit manually a great way to fine tune skills as you have to over emphasise the concentration on ppo2 as any tiny changes are reflected quickly


20m is a good depth imho for practicing lots of other skills and 10m up is good for ascents.

There will be a lot to get used to and you will want to give up before you get the hang of it but stick with it

I await other views where I will be called a gobshite

[gobfish1]

gobshite

dont feeking bring me in to it

[Paulo]

dont feeking bring me in to it

Day release or did you get parole?

[notdeadyet]

I think train as you mean to dive. If nothing else, your brain knows you are at 6m.

You don't have to do daft depths but I think there is merit in doing at least depths with some commitment. If you need to bail at 6m then you have all the time in the world. You can damn near just stand up. A lot different at 30-40m. A lot easier to blow your buoyancy on the way up on a bailout from depth. If you don't like a shallow dive then there is nothing keeping you there but discipline, deeper then you are committed. Loads of reasons.

I kind of look at it like climbing. Sure you can practice everything a few feet off the ground but at some point you will be half way up a decent pitch, look down and suddenly it becomes real. That changes things dramatically. The big difference between 6m and 60m is psychological and there is no way to train your brain for that than to do it.

[jturner]

As I embark on my rebreather odyssey, inevitably hours of training and familiarisation await but how much relevance does depth play in this evolution.

When I was diving oc in the 90s we did a lot of what used to be euphemistically called extended range, but was really deep air, we would therefore spend winters at depth in quarries building up skills but also allegedly improving our ability to resist narcosis, or so we told ourselves.

With helium mixtures in ccr being largely influenced by density with attendant low end's is there a need to practice skills deep with the increase in risks associated or is it better to dial skills shallow and then progressively extend depth operationally?

For me, it depends on the skills. Doing flushes shallow means you can do more of them before you run out of diluent and can do O2 flushes too (which are very handy). As has already been pointed out, bailout from 6m is simple. Good for learning the basics but not the same as a bailout from 50m+ complete with gas switching. I'd suggest you nail the skills in the shallows until they're slick and efficient, then work deeper. A poor flush a 6m is annoying; at 30m, you'll empty your dil in no time.

Build it up slowly would be my advice. And don't assume good OC skills means you can fast-track CCR skills. As Pyle said back in the day "after my first 10 hours on a rebreather, I was a real expert. Another 40 hours of dive time later, I considered myself a novice. When I had completed about 100 hours of rebreather diving, I realised I was only just a beginner. Now that I have spent more than 200 hours diving with a closed circuit system, it is clear that I am still a rebreather weenie."

[gobfish1]

when you have sorted noddy 1



id say dont use air as a dill ,

bail outs id run a few from 50m should be simple if your used to deco cans and deep air ,
30m / 40m feek me you home on a pony , and you have two on ye unit , play with them
and a 7l till your sorted , (at a depth your happy with )

once happy id do a few 80m 40m bailouts , and have a play a scr

get the feel of how much o2 you use as you swim around / sat on a rock, under stand how ambient pressure works For and against you on your dives.

all ways dive unit as o2 breather in 6m or less.
never use internet set points , get some feeking o2 in your unit.
if your used to deep air best up your sac a few points for bail out to h/mix deco cans as Helium go,s down real nice not like sucking air / treacle toffee at 70m lol,

ps
dill/o2 flushes i was board with that on day 3 of noddy 1 but hay if you want to play then
have at it ,
tip
o2 flush at 6m or dill flush at depth empty the lungs first ,

edit
im on a ybod , not sure its so simple on a kiss


the only thing i found frustrating was going from peter pan to dumbo,

[cathal]

Not sure where you are located but if you can get a location that has 30-40M depth available all year around you'll be sorted for skills and drills that will cover you up to 70M. If its a freshwater location i.e. quarry or lake I find using the exact same configuration that I plan on diving with during the season on every single training dive pays of dividends when the season starts and even throughout the season. When your on a boat for the first dive, I find the motor skills just kick in and that helps relax me on the boat getting kitted up. And then if you do a shallow dive on the unit and you just need a 7 litre for bailout then this configuration will then feel very comfortable.
Regarding practicing at depth I don't launch my red SMB much during the season as I usually come up a shotline. So I have started launching the SMB in the quarry from 35M on each dive - as there's not much work involved coming up from 10M-15M. I was very rusty at the start coming up on the reel but after a couple of dives I found doing this exercise at depth made a big difference to my skills and my confidence.

[colinicky]

The only real difference to skills at 6metres is that as Paulo said you need lots of gas for flushs BUT it also means you get to practice buoyancy changes a hell of a lot more ! TBH I am the worlds worst, if a dive is less than 10 metres I don't bother doing it as my buoyancy is crap as I never practice enough

[LukeTheDiver]

I’m hoping to go to CC next year. Trimix on OC hurting the bank!

[Mark Chase]

As I embark on my rebreather odyssey, inevitably hours of training and familiarisation await but how much relevance does depth play in this evolution.

When I was diving oc in the 90s we did a lot of what used to be euphemistically called extended range, but was really deep air, we would therefore spend winters at depth in quarries building up skills but also allegedly improving our ability to resist narcosis, or so we told ourselves.

With helium mixtures in ccr being largely influenced by density with attendant low end's is there a need to practice skills deep with the increase in risks associated or is it better to dial skills shallow and then progressively extend depth operationally?

Ironicly with a CCR even at relatively shallow depths you need to carry two cylinders.

With OC I was regularly diveing 40m ENDs to keep HE cost down. On CCR I limit myself to 20m END and am often diveing less, I'd happly dive 18/45 on a 30m wreck

Depth on CCR means increased risk of C02 narcosis being debilitating

Depth on CCR means more proficiency with bailout management

Now IMHO if you have deep multi cylinder experience on OC that goes a long way to providing the multi tank skills you will need but in the end managing an ascent on a flooded CCR will be a different exercise to managing an ascent on a normal trimix OC dive

SO seeing as hardly any one properly practices failed CCR ascents? Is this realy a consideration in the real world?



On the + side the gas time pressure at depth on OC is just no longer an issue. I litraly laughed underwater the first time this benefit became important on a broken guide line dive, low viz, 80m dive, MUST return to shot. The panic of finding my guide line broken was quickly replaced with a laugh that all it would mean is a bit more deco. Being relaxed made re-finding the line much easier

The other thing people forget is theres 300+% redundancy in a properly set up CCR rig where as theres pretty crap redundancy in a OC rig

By 300% I meen

Option1 Bailout to OC and ascend

Option 2: Use SCR and Pure 02 CCR to ascend

Option 3: Buddy


OC: Buddy? that's it, and good luck with that.



On a final note don't underestimate how badly a CCR will screrw up your narcosis tolerance.

After years on OC diving regularly to 50-60m on air and with dives down to 70+, I was as capabul of deeling with narcosis as its possible to be

Then after a few years diving ENDs of less than 20 on CCR I discover I am now narked off my tits on 30m red sea single tank dives


ATB