Question Advanced Specialties Discussion

[Blackcrusader]

It is not a specialty in most agencies, but I'd like light back gas deco. 10 minutes of back gas deco adds 50 to 100+% ish more time past NDL in the 80' to 130' range.

hmmm single AL 80 lets plan a 15 minute dive at 40m need 10 mins deco time for a total dive time of 25 minutes. Only need 1055 liters at SAC of 12l/min GF 45/95. Or 40m for 20 minutes need 17 mins of deco time for total dive time of 37 minutes using 1480 liters. All on air. You might get more time past NDL but you end up with shorter dive times doing a square profile whereas a dive to 40m staying within NDL limits and doing a multilevel dive has no set time limit. Of course 12l/mon sac rate is being very generous to most vacation divers. Others on SB have good low gas consumption.

Of course better if you have a 100 or 120 size tank perhaps although I have seen divers struggle with the larger tanks. To add light back gas deco you will want divers to be able to know about their RMV and have two tanks yes?

A 25m dive on 21% for 40 minutes then 17 mins deco time at 12l/min 57 minute dive time 1900 liters of gas.
A 25m dive on 32% for 45 minutes then 6 mins of deco 1920 liters of gas at 12l/min very tight on a single AL 80 need a pony
A 25m dive on 32% for 50 minutes then 9 mins of deco 2200 liters of gas at 12l/min near empty tank lol Need an AL100 plus pony

For me on an AL80 I can do the 25m depth 50 minute dive pls 9 mins deco. At that point I need to ascend to do my deco obligation I would still be at half tank on an AL80. Plenty of gas left to complete deco obligation. Total gas I would need would be around 1500 liters.
Others not sure about them lol.

 

[Edward3c]

you dive a rebreather? If so, let's go look for wrecks an old sponge diver told me about.

No, although I’ve done the intro, rebreathers are not for me. My normal rig is 300bar/12Lt with a 3Lt pony. I know too many who own one, but now dive OC as it’s more convenient.

If they had been around 40+ years ago I might have been a convert.

 

[MichaelMc]

NDL matters more deeper and the back gas deco certs limit required stops to 10 min. We can stay at 30 to 40' all day with the right gas and thermal protection, so shallower profiles are not the issue.

I do have a low RMV range, .4 cuft 11l/m at the higher end, so:

GF 50/70, .4 cuft /min, and EAX32 gives:
100' 14 min NDL uses 25 cuft. + reserve = 38 cuft
100' 28 min BT needs 10 min stop at 20' uses 54 cuft + reserve = 77 cuft
Meaning an AL80 is fine on just gas volume. (For me.)

75' 28 min NDL uses 39 cuft + reserve = 59 cuft
75' 49 min BT needs 10 min at 20' uses 72 cuft + reserve = 108 cuft

But yes, back gas deco classes teach having redundancy and that 50% reserve, so two tanks should be used. AL80 + 40 will do nicely. (With a low RMV)

Or my sidemount 2x LP50s would almost fit the bill nicely as well.

It gives you more time on the wreck or pinnacle, without the bulk of accelerated deco.

For an *advanced* specialty class, I think it would be a good pick, given good skills work prior on buoyancy, propulsion and trim.

 

[Gandalf-the-Diver]

It may come to no surprise that my favorite con ed course was GUE fundies.

 

[Nosmosis]

There is no PADI specialty called Psychological Diver. What are you talking about?

There is a PADI Psychological Diver - it is essentially a Human Factors course.

 

[tursiops]

There is a PADI Psychological Diver - it is essentially a Human Factors course.

It is a "distinctive" specialty, usually taught only by the person who wrote it. It is not generally available like the real specialties.
I wrote a distinctive speciality called Coral ID, but you can't take it except from me.

 

[Nosmosis]

It is a "distinctive" specialty, usually taught only by the person who wrote it. It is not generally available like the real specialties.
I wrote a distinctive speciality called Coral ID, but you can't take it except from me.

got yah

 

[Ulfhedinn]

There is a PADI Psychological Diver - it is essentially a Human Factors course.

Its a great class.

 

[Oldbear]

My favorite specialty course is actually two courses I teach together…DPV & Wreck. On the last dive which is a DPV dive I take the student on a tour covering 7 WWII wrecks….Japanese and American.

The wrecks include

1 Japanese Patrol Boat
1 Japanese Freighter
1 Japanese Subchaser
1 Japanese Harbor Boat
3 American LCM-3s (Higgins Boats)

 

[ScubaBadger32]

My favorite specialty course is actually two courses I teach together…DPV & Wreck. On the last dive which is a DPV dive I take the student on a tour covering 7 WWII wrecks….Japanese and American.

The wrecks include

1 Japanese Patrol Boat
1 Japanese Freighter
1 Japanese Subchaser
1 Japanese Harbor Boat
3 American LCM-3s (Higgins Boats)

Dang! Where do you operate out of/where are these dive sites?