Exceeding NDL on an al80?

[krbailey]

Interesting question that I really could not definitively answer from recall so pulled up my dive log and looked at a recent Cozumel trip since it would be most representative of my typical al 80 dives.

First dive first day, Columbia Deep hit 3 minute before I ascended shallower to extend dive. Max depth 110. 32% gas

Next day first dive, Cathedral and hit 2 minutes before going up. 36% gas

Both cases I had to ascend secondary to NDL and not gas.

Caveat: I dive a very conservative algorithm and these were both deepish dives although my algorithm conservativism doesn’t really kick in until repetitive dives.

Edit: Bob brought up another factor, nitrox. Added to post.

Just for my own curiosity...

From what I can tell, the Cathedral dive is betweem 120-128fsw.

MOD for EAN 36 1.4po2 = 95fsw
1.6po2 = 114fsw

 

[uncfnp]

Just for my own curiosity...

From what I can tell, the Cathedral dive is betweem 120-128fsw.

MOD for EAN 36 1.4po2 = 95fsw
1.6po2 = 114fsw

The times that I have done Cathedral/Punta Sur (excluding Devil’s Throat) my dives have been between 92 to 107. The 107 dive I brieft hit ppo2 1.52.

I have done DT on 32%. Hit max depth of 134 with a ppo2 of 1.62 for about 30 seconds.

 

[krbailey]

The times that I have done Cathedral/Punta Sur (excluding Devil’s Throat) my dives have been between 92 to 107. The 107 dive I brieft hit ppo2 1.52.

I have done DT on 32%. Hit max depth of 134 with a ppo2 of 1.62 for about 30 seconds.

Thanks for clarifying! I've never done that dive. Thought it was much deeper.

 

[northernone]

Today beyond recreational depths by the time I breathed ~80 cf of gas I had already accrued 53 minutes of deco with GF 60/80. VBM-b +2 was asking for 41 minutes. SendS to well answer the question personally.

Cameron

 

[NAM001]

100 ft 20 min should be about a sac of ,8 2500/300 * 65 cuft / 20 about 3.2 cuft @ 4atm. some one correct me if needed.

 

[Jim Lapenta]

My normal working rate is .46 so I can get close to or exceed NDL's on a nice relaxing dive. Though I choose not to. In fact I don't even use al80's if possible unless it's two of them or they are being slung as stages. My normal single cylinder dives are done using LP95's with a bit of a bump on the fill. If it's a dive in excess of 100 ft I'm also slinging a 30 or 40.
My GF's rate before she stopped diving was a verified .26 so yeah, she could easily exceed the NDL's on an al80.

 

[stevensamler]

100 ft 20 min should be about a sac of ,8 2500/300 * 65 cuft / 20 about 3.2 cuft @ 4atm. some one correct me if needed.

You're oog at 100'.

 

[Jackie Treehorn]

My working rate in Cozumel on single tank dives is .40. On a trip two weeks ago running EAN30 there I hit my NDL on pretty much every morning dive. I just multilevel it up from there. Each subsequent dive (usually four a day) I would mostly bottom out at 10 ft less then the previous dive and stay if or when my NDL made me level it up.

After 60 minute dives (including the 5 minute Shearwater safety stop for over 100ft) I'd usually end up on the boat with just a touch over 500psi.

 

[HeliMech]

First dive on the double reef on Bonaire. Looked down and was within 6 minutes of NDL with a lot of gas. Did a slow small ascent and headed for the 1st reef. Another first dive at near 130' on Bonaire I got within 2 minutes of NDL and still had a lot of gas. So, at least for me it's something to watch.

Maybe I'm missing something but just take an AL80 to 130' and anyone can exceed NDL no problem. Just check your dive tables...

 

[Kharon]

Maybe I'm missing something but just take an AL80 to 130' and anyone can exceed NDL no problem. Just check your dive tables...

I think that's what I was saying. The OP question was "With your current SAC rate and staying within recreational depths can you have NDL become the limiting factor on your dive if you surface with 500psi in an al80 cylinder?" or didn't you read the OP?