Exceeding NDL on an al80?

[mi000ke]

I have a SAC rate of .4 cfm and now dive nitrox, having frequently bumped up against ndl - although with a computer it just means shallowing out, not necessarily ending a dive - until air gets low.

For example, my last deep wall dive was a max depth of 90' and and average depth of 58'. Using the Dive Planner app (PADI tables), based on my average depth, my ndl would have been 55 minutes on air. I got 62 minutes for the dive on EAN32 with ndl to spare, and was on board with 600 psi. With EAN32 my ndl would have been 80 minutes for this average depth according to the app.

 

[scubadada]

On a first, clean dive, at my average RMV, on air, I will be NDL limited at 60 feet and deeper. Using 32%, I will be NDL limited at 80 feet and deeper. Using 36%, I will just be NDL limited at 90 feet. I haven't dived air for quite a long time. I dive a computer running DSAT, reasonably liberal NDLs. I would be more limited if diving a more conservative deco algorithm.

....and then, of course, there are repetitive dives

 

[Coztick]

Very easy for me. On my last dive, the 1st of two was to a wreck which was 100 - 120+ft. I maxed at 107 and stayed 100ish. Eventually had to start adjusting my depth so as not to ride the limit too much. Dive time ended up being 32 mins. I started with 2900 psi and was in the boat with 1400 psi.

My Gekko behaves similarly on deeper profiles, forcing an accent. Not a big deal on a wall you can shallow up on but on deeper sites it leaves me hanging with much less to see.
Im thinking/ hoping my "new to me" Oceanic will allow me to enjoy more bottom time.

Cheers, Kevin

 

[Steve_C]

If the water is nice and I am basically slowly drifting around a wreck taking a few pictures there is very little physical exertion. Easy to do on air. With nitrox it gets a bit more challenging.

 

[tursiops]

For example, my last deep wall dive was a max depth of 90' and and average depth of 58'. Using the Dive Planner app (PADI tables), based on my average depth, my ndl would have been 55 minutes on air.

Are you serious? You used your average depth with the PADI tables?

 

[J-Vo]

I hit 2 minutes of deco diving Devil's Throat in Cozumel a few weeks ago. Used about 2k psi for a 39 minute dive. This was with my Shearwater @ 50/80 on air. I don't think anyone's sport PDC in the group went into deco, but they couldn't have been far off as I was under a ceiling for nearly 15 minutes of the dive. Could also be that no one else pays attention to their PDC.

 

[Compressor]

It all depends on one's SCR and depth. Sure its possible.
I've been on dives with novice divers (not being derogatory) who were told follow DM to depth near 100 only to get the dive aborted midway as diver were getting way low on air supply.

 

[Diver0001]

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? Not a repetitive dive.

I can normally, including plenty of profiles run on the U.S. Navy tables.

I've heard it at least a dozen times that with 68cf of gas, there's no need to monitor NDL for the average diver if there are doing only one dive on a weekend.

My RMV is about .4 and it's not very hard to get over the NDL's with an AL-80. That said, I don't like to be very far over the NDL's with gear that isn't redundant.

R..

 

[stevensamler]

It all depends on one's SCR and depth. Sure its possible.
I've been on dives with novice divers (not being derogatory) who were told follow DM to depth near 100 only to get the dive aborted midway as diver were getting way low on air supply.

I agree MGR for a 100' dive on an al80 with a TF of 2.5 is 41.50 ft/3 of gas which is 1660 psi rounded up = 1700 psi. 3000 fill pressure - MGR ( 1700 psi ) = 1300 psi UG for working portion of dive = 10 min bottom time. 1300 psi = 32.5 ft/3 at 3 ft/3 p/m consumption rate is a 10 min B/T.

 

[mi000ke]

Are you serious? You used your average depth with the PADI tables?

I used the dive planner app which is based on PADI tables to come to some estimation of ndl under air and nitrox for a deep dive with an actual average depth provided by my dive computer. How else would you recommend I make the comparison?