Deep Diving 108 feet w/ a single AL 80 (Air.) No redundancy.

[scubadada]

Since this thread has grown and been revived since my first post, I think it's important to reiterate that the Chester Poling wreck (which this discussion was initially about) is NOT a tropical dive. It's a cold low-vis north Atlantic wreck. Different risk profiles demand different dive profiles.

My second highest RMV ever was on the Chester Poling in Sept 2010. It was a relatively deep, cold (47 degrees) dive with some current. I was diving wet. My highest RMV was the second dive that day at Halfway Rock. I was still cold from the first dive and half the dive was into current. I did two more dives that day after lunch at Little and Dry Salvages, the water was much warmer, low 50s . If I frequently dived in such conditions, believe me, I would be in a drysuit

 

[Dody]

Sorry I missed the fact that it was in cold water. That changes everything. In tropical waters, I still believe it can be safe. I remember one dive when my RMV was probably around 30 l/ min because of a drink party a few hours before and less than 4 hours sleep. Before I got into water, I knew I was not good. When in the water, I immediately realized that I could not control my breathing as well as I did a few dives before. Had it been a deep dive, I would have called it but it was pretty much a leisure dive above 15 meters. I remember that I had 70 bars left from 200 when my wife had 120. I learnt an important lesson that day... and I am still learning.

 

[Dody]

Hi @Dody

You recently reported a significant decrease in your RMV from 20 to 11 L/min and you don't have many dives. It is most useful to have an average RMV representing the breadth of dives you do and the conditions you encounter. The variation around the average also helps in choosing what gas consumption to use in planning calculations. Examining your dives with the highest gas consumption helps identify the factors that are most important for you.

I have my RMV for nearly all of my last 1500+ dives and my RMV is 0.36 +/- 0.04 cu ft/min (mean +/- std dev). Sorry for the imperial units, it's what I use. So, 95% of my dives have an RMV between 0.28 and 0.44 cu ft/min. For me, I know that strenuous exertion and thermal stress, due to cold, are the most important determinants of my gas consumption. For routine gas planning, I use an RMV of 0.45-0.5 cu ft/min, the higher value if I expect exertion and/or cold. For emergency planning, I use twice my average RMV. For example I dive a 19 cu ft pony, and know that I would spend a minute at depth, make a normal ascent with a 3 min safety stop, from 130 ft.

Continuing to monitor your RMV will be helpful in your future diving.

Good point. Thanks. I will keep it in mind.

 

[scubadada]

@Dody, I agree, good planning is important. A single AL80 isn't good planning for sub 30m dives, particularly in colder, dark water.

Sorry, there is no good reason to not dive to recreational limits, 40 m, on an Al80, as long as you are aware of you NDL and gas limits and have the skills to do the dive. You adjust for cold, dark, poor vis, high current water.

 

[grantctobin]

Sorry, there is no good reason to not dive to recreational limits, 40 m, on an Al80, as long as you are aware of you NDL and gas limits and have the skills to do the dive. You adjust for cold, dark, poor vis, high current water.

Narcosis.

 

[scubadada]

Narcosis.

For you. And how does having more gas alleviate this?

 

[RyanT]

For you. And how does having more gas alleviate this?

Time to solve a problem when you are working slower.

Sorry, there is no good reason to not dive to recreational limits, 40 m, on an Al80, as long as you are aware of you NDL and gas limits and have the skills to do the dive.

Dive on!

 

[scubadada]

Time to solve a problem when you are working slower.

Oh, come now, you're kidding

 

[RyanT]

@scubadad, yep. I've been narced at 130' and gotten disoriented on a wreck. I'm glad I had extra gas to navigate back to the anchor line, when it took longer than expected.

 

[scubadada]

@scubadad, yep. I've been narced at 130' and gotten disoriented on a wreck. I'm glad I had extra gas to navigate back to the anchor line, when it took longer than expected.

And you realized this after the fact, attributed it to narcosis, and needed the extra gas? In general, if you have noted your anchor point, it is not difficult to return, I guess, unless you have narcosis. Sorry, though I'm skeptical, I can see how this might work.