NACD Intro - 58cf Limit - Why?

[Dive-aholic]

Jago, I think you misunderstood. What Dive-aholic is saying is that the steel 72's at 2000 psi is 58 cu feet.

So, you don't go for a dive without a minimum of 2000 psi in your 72cf tank, and you are limited to use one third of that tank, or 660 psi, for the entrance, and the rest for the exit.

I think he meant to type, 2.9 x 20 = 58cf. Otherwise, it would have been .029 * 2000psi = 58cf.

Yes, I should have typed 20. I usually don't bother to use the actual tank factor of 2.9 but rather skip that step and just use .029 when doing my own calculations. However, students have an easier time dealing with bigger numbers so that's the way I teach it. My fingers just weren't listening this time.


And for everyone who is ragging on Jax about taking a class, did you not prepare for your own classes by reading the student manuals before the class? Oh wait, obviously not because you already knew everything there was to know about it and just took the class for the card.

 

[cavemn]

Doubles MAY be used at the discretion of the instructor.

If the instructor doesn't INSIST on doubles and a proper setup find a new one.

 

[Jax]

If the instructor doesn't INSIST on doubles and a proper setup find a new one.

Oh, I don't know about that. I think instructors should let students use the singles. The person may decide cave isn't for him or her. I wouldn't want to just jump into a cave class in a bunch of gear I haven't practiced in. I'd look like a bigger spaz then normal!

 

[Jax]

Hey, I found out tonight I don't need no stinking lessons!!!!

"He wasn't certified but he had taught himself to a high standard and knew exactly what he needed to do and did it safely".

I can teach myself to a high standard, too. Hold my beer and watch this!

 

[cavemn]

Oh, I don't know about that. I think instructors should let students use the singles. The person may decide cave isn't for him or her. I wouldn't want to just jump into a cave class in a bunch of gear I haven't practiced in. I'd look like a bigger spaz then normal!

My NACD and TDI cave certs required a minimum level of Tech certification first. My Tech instructor required doubles. German requires doubles and a Hogarthian setup for cave . The first day was gear configuration and Hogarthian method. He was prepared to work with newbies on their buoyancy and trim. You can read all about it in his book. I feel like I got more than my moneys worth of cave training.

Is there an agency that does not require doubles for tech before cave???

 

[Dive-aholic]

Jax is talking about intro cave not full cave. Historically, intro cave could NOT be taken in doubles.

 

[PfcAJ]

Historically, you needed a deep air cert before trimix, too. Its a good thing times are a changin'.

 

[cavemn]

Jax is talking about intro cave not full cave. Historically, intro cave could NOT be taken in doubles.

I guess NACD show doubles as optional for cavern and intro to cave. What agency did NOT allow doubles? Why would you not already have doubles equipment from Tech?

 

[ucfdiver]

I guess NACD show doubles as optional for cavern and intro to cave. What agency did NOT allow doubles? Why would you not already have doubles equipment from Tech?

The NACD used to have a 90 day waiver your instructor had to fill out to allow you to dive doubles at intro (it really only mattered at Ginnie). From what I understand, this basically stated that you were going to continue cave training soon, and were gaining doubles experience. The CDS offered a 1 year card that was intro with doubles specifically. From my understanding, the NACD training director was against allowing intro divers to use double tanks, for fear they would exceed their training limits. Because of this, nearly everyone opted to get the CDS (or other agency) card since most instructors are crossed over to teach multiple curriculum. Clearly this cost the agencies that didn't allow doubles lost revenue, and they adjusted, maybe not for that reason, but if I had to guess...

As for why the students don't already have doubles, you have to remember that you can take cavern almost right after OW. The NACD requires 15 dives for cavern, and 25 for Intro to cave, so basically you would qualify within a week long live aboard. Other agencies require intro to tech and 50-100 logged dives, but they lose students because it takes too long, and it's too expensive for them.

FWIW you don't need any deco training to take apprentice or full cave either according to standards, and it's basically impossible to do these dives without deco. Under such loose standards, some instructors cover basic deco, some require a deco class before apprentice, and others just let the student ride their computer, it really all depends.

 

[cavemn]

That's a shame some agencies are so lax. I'm going to jump of my soapbox now and just feel fortunate about the training I received.