Reconsidering Deep Air?

[KenGordon]

I can't trust any diver who thinks they are immune to narcosis. Going on feelings is a fool's errand. You really can't tell how it affects you until it's too late. Hal Watt's book was entitled "Managing Narcosis" for a reason.

I've done some deep air dives in my time, but I don't think this old fat body is up to doing them anymore.

if mac64 will excuse me applying stereotypes...

Have you been to Ireland? The national sport is being narked. He will hopefully have allowed his baseline narkness to decline prior to the boat ride and then come back on the wreck.

 

[The Chairman]

if mac64 will excuse me applying stereotypes...

Have you been to Ireland? The national sport is being narked. He will hopefully have allowed his baseline narkness to decline prior to the boat ride and then come back on the wreck.

Don't quit your day job. Your humor isn't.

 

[Celt]

Personally I am a wuss and would be doing 30 or maybe 35 minutes for a 90 or 100 minute runtime. I am looking at a log of the Leonatus in 57m, that would have taken 4450l of backgas OC by my usual OC planning with 18/45.

The bloke giving me the blacked out mask treatment (not a wuss) was giving a talk recently about a 120m dive with something like 20 minutes bt and a 4 hour run time.

The limiting factor is bailout. By the book you have to assume 45l/minute for a CO2 hit. With an hour of deco to do that is really more that two ali80s. However if you have a 90 minute plan and are delayed 10 minutes on the bottom so you end up with a 120 or 130 minute dive you still have plenty of everything. Clearly a CO2 hit and bail out on such a delayed dive would be bad, but that is two major failures. Worst case might be a co2 inside some wreck and kicking it up so your exit is slow. Don’t do that

These sorts of dives are not terribly expensive on gas, a 3l of 15/50 or so is £10 or £15 of helium and you’d have plenty left for an afternoon bimble. With a twinset you’d be looking at £70 to £100 so much less likely to actually use it.

For me a CCR is a toy, but it does make these gas limited dives much more enjoyable. Checking your ppO2 is less stressful than thinking “bugger I am 10 bar lower than I ought to be, better turn sooner” etc.

When I first dived the Cunard liner SS Feltria 67m no one had dived it before. It was the most beautiful day and the conditions were perfect: I’d have given my eye teeth to stay another 10 minutes. I tied this copper fish kettle on the shot before leaving the bottom.

 

[Celt]

Sorry put photo up twice

 

[KenGordon]

View attachment 650169 View attachment 650169
When I first dived the Cunard liner SS Feltria 67m no one had dived it before. It was the most beautiful day and the conditions were perfect: I’d have given my eye teeth to stay another 10 minutes. I tied this copper fish kettle on the shot before leaving the bottom.

Ah yes, the old better than expected conditions problem.

 

[tursiops]

Sorry put photo up twice

That's what happens when you're narced.

 

[Celt]

if mac64 will excuse me applying stereotypes...

Have you been to Ireland? The national sport is being narked. He will hopefully have allowed his baseline narkness to decline prior to the boat ride and then come back on the wreck.

It’s actually hurling but it’s to bloody for the English so we have to beat them at rugby instead Ireland 32 England 16

 

[Celt]

That's what happens when you're narced.

There’s always someone in the sideline waiting for an opportunity for you to slip up.

 

[Wibble]

Doing my first 70+m / 220' dive on open circuit, I was astounded how quickly the back gas was consumed. With those deep dives on OC, it's all about being calm and conserving gas as your bottom time is determined primarily by your minimum pressure and secondarily by your deco plan. In a phrase; be frugal with gas.

With CCR you can pretty much huff and puff as much as you like without consequence - within reason. The planning is all about bailout and how much you overestimate for "Your CO2 Hit", the biggest fear of a CCR diver. The guidelines say you should calculate for a SAC of 45 litres/min (1.6 CF per min), which at depth means you consume absurd amounts of gas
Maffs: 80m/250' = 9 ATA = 45x9 = 405 l/min (1.6CF x 9 = 14.4 CF/min) in other words emptying an ali80 in 5.5 mins -- if you can get on it without drowning.

Hence you a) don't want a CO2 hit, b) need other peoples bailout gas, c) need other people to keep you alive.

 

[Kay Dee]

Hence you a) don't want a CO2 hit, b) need other peoples bailout gas, c) need other people to keep you alive.

Your right, you certainly don't want CO2 hit, but..............by the same token you (the collective you that is) shouln't need other peoples bailout gas or need other people to keep you alive (underwater). That's being reliant. And even if diving with a buddy you (again the collective you that is) want to be totally self reliant and / or simply accept the consequences if your not.

Might be nice to have someone else there when the s@#t hits the proverbial, but then again it might not. Whatever, you shouln't be dependent on them.