PADI tech 50 no refill between dives

[sk001]

Hi. Just wanted to see what opinions people have. A friend is presently doing her tech 50 course. I asked her how it was going and she told me that she had just completed a short first dive to 50m with a total runtime of 26 minutes.

It seems a bit short so I asked her why and she said it was because they were on a boat with no capacity to refill so they needed to save enough backgas for their second dive which was planned to 40m.

I expressed some concern about this and she told me that they had worked out their minimum gas and so she was told it was okay.

I was wondering is this actually permissible or does she have a loose canon for an instructor

 

[Miyaru]

So that was just a touch-and-go dive. Two gas changes and virtually no stops.
Ask her what she learned on this dive....

 

[northernone]

I've done training where limited resources became a factor. If the infrastructure met the training requirements safely and in a way that added sufficient value to the student I am ok with it.

Personally I like much longer dives, and if someone cut me short due to not wanting to bring an extra set of doubles along I was willing to pay for, I'd feel unhappy. But the value for money dynamic is personal.

I have a pair of lp131s I cave fill... We can do a half dozen rec dives on a single fill. Gas planning and management is part of training. Real life. We don't always have full tanks or need them... And a full tank is arbitrary... Carrying a quantity of gas which is required for the dive plan is necessary.

Cheers,
Cameron

 

[tbone1004]

50m, 6ata, probably 3.6cfm consumption, 26min total run time was probably 15min bottom+descent time, so call it 60cf out of the backgas bottles, and 30cf of EAN50 ish.

Even with AL80 doubles/sidemount, that is about 1200psi consumed with 1800psi left. Depending on gas consumption, it is possible to do a second dive with that. 40m doesn't really change gas consumption much, but could probably do another 15min bottom time at 40m with no real issues assuming the EAN50 bottle was an al80

 

[kensuf]

I frequently do something similar on the deep dives in my normoxic trimix classes. The way we do it is to use a stage bottle of bottom mix on one of the dives, and back gas on the other. Swap out deco bottles between dives though.

 

[Alastor]

50m, 6ata, probably 3.6cfm consumption, 26min total run time was probably 15min bottom+descent time, so call it 60cf out of the backgas bottles, and 30cf of EAN50 ish.

Even with AL80 doubles/sidemount, that is about 1200psi consumed with 1800psi left. Depending on gas consumption, it is possible to do a second dive with that. 40m doesn't really change gas consumption much, but could probably do another 15min bottom time at 40m with no real issues assuming the EAN50 bottle was an al80

although your math is correct, do not forget they are attending a course so, on the second dive, they MUST have gas reserve, whatever method they use to be safe.
Rule of thirds, rock bottom or whatevere, I don't know if having "only" 1800 psi would allow that reserve.

 

[tbone1004]

although your math is correct, do not forget they are attending a course so, on the second dive, they MUST have gas reserve, whatever method they use to be safe.
Rule of thirds, rock bottom or whatevere, I don't know if having "only" 1800 psi would allow that reserve.

still possible to maintain the reserve when you are doing that, you wouldn't sacrifice anything on that reserve, just bottom time

 

[Alastor]

still possible to maintain the reserve when you are doing that, you wouldn't sacrifice anything on that reserve, just bottom time

Right, so probably another 16'-17' bottom time ... it is just a bit longer than touch and go, breathing air it makes sense.

 

[sea_ledford]

So that was just a touch-and-go dive. Two gas changes and virtually no stops.
Ask her what she learned on this dive....

That's a 26 minute dive, not a touch and go. On a first dive in a deco class I certainly don't put my divers in actual deco anyway. I want to see them hold simulated stops and deal with gear and emergencies. Most of the drills are on ascent anyway. No reason to mess around at max depth just to build up deco time for no reason other than to build up deco time. At least not on the first dive.

Now if all of the divers were like that, I might have some issues, but dealing with limited resources should be part of the course as well.

-Chris

 

[Freewillow]

Nonsense.

When doing my Divemaster in the US some 20 years ago. Dives were "split" in half with one tank in order to increase the number of dives on the logbook.

You only fool yourself with that kind of practice