Modifying rule of thirds

[Line Squirrel]

Isn't the rule still 1/6s for cavern and intro.?

jj is probably talking single tank which would be 1/3

[jj1987]

Isn't the rule still 1/6s for cavern and intro.?

It varies from agency to agency from what I understand. According to the intro class this past weekend, we're allowed to dive single tank ONLY, with turn pressure being when you hit 2/3. It was repeated several times during lecture that we can not under any circumstances dive doubles. I'm not an instructor, and don't have access to the nacd workbook, so my information could be off here. I believe that TDI, NSS-CDS, GUE, and maybe others I'm unaware of have provisions for intro students (or equivalent) to dive doubles.

I have my own opinions about this, as I've spent several hours reading, discussing, and thinking about this exact topic, but since this is a public forum, and I don't have enough experience to make my opinion worth much anyways, I'm not going to go into it here. I know there's a thread on TDS about this, so no need to start another. For those of you who disagree, I'd encourage you to write an email in a professional manner to the people at the following link, rather than starting it on a message board that won't change anything.
http://www.safecavediving.com/training_committee.shtml

I would like to say that Ginnie springs is the only place I know of that enforces this. The thread on TDS was specifically attacking them. Please remember when going there that it's not their rule, so don't get mad at them when they enforce it, they do so much for the diving community, I'd hate to hear them taking crap for simply enforcing a rule that isn't theirs.

[inkdiver]

It varies from agency to agency from what I understand. According to the intro class this past weekend, we're allowed to dive single tank ONLY, with turn pressure being when you hit 2/3. It was repeated several times during lecture that we can not under any circumstances dive doubles. I'm not an instructor, and don't have access to the nacd workbook, so my information could be off here. I believe that TDI, NSS-CDS, GUE, and maybe others I'm unaware of have provisions for intro students (or equivalent) to dive doubles.

I have my own opinions about this, as I've spent several hours reading, discussing, and thinking about this exact topic, but since this is a public forum, and I don't have enough experience to make my opinion worth much anyways, I'm not going to go into it here. I know there's a thread on TDS about this, so no need to start another. For those of you who disagree, I'd encourage you to write an email in a professional manner to the people at the following link, rather than starting it on a message board that won't change anything.
http://www.safecavediving.com/training_committee.shtml

I would like to say that Ginnie springs is the only place I know of that enforces this. The thread on TDS was specifically attacking them. Please remember when going there that it's not their rule, so don't get mad at them when they enforce it, they do so much for the diving community, I'd hate to hear them taking crap for simply enforcing a rule that isn't theirs.

Not to hijack, but NACD does allow for doubles at the Intro level. The student has to take the class in doubles and show mastery of the required skills in doubles, and the instructor has to provide a "waiver" for lack of a better term, that is normally predicated on the fact that the student will continue with at least Apprentice level within a certain period of time. In your situation, you had an instructor who chose not to provide that option, but it doesn't mean that the NACD does not do so.

[jj1987]

Not to hijack, but NACD does allow for doubles at the Intro level. The student has to take the class in doubles and show mastery of the required skills in doubles, and the instructor has to provide a "waiver" for lack of a better term, that is normally predicated on the fact that the student will continue with at least Apprentice level within a certain period of time. In your situation, you had an instructor who chose not to provide that option, but it doesn't mean that the NACD does not do so.

Isn't this only good for 6 months, or am I off base here?

BTW- forgot to add, if my above post was off, anyone please feel free to chime in and correct me, that was my personal understanding, and like I said, I'm new to this stuff.

[cavediver256]

Isn't this only good for 6 months, or am I off base here?

BTW- forgot to add, if my above post was off, anyone please feel free to chime in and correct me, that was my personal understanding, and like I said, I'm new to this stuff.

Actually, at one time it was good for 1 year....like you, I may not be aware of any changes that may have been made since then. I guess I should be tarred and feathered for not keeping up.....

[RN]

Isn't this only good for 6 months, or am I off base here?

BTW- forgot to add, if my above post was off, anyone please feel free to chime in and correct me, that was my personal understanding, and like I said, I'm new to this stuff.

It's called a discretionary apprentice waiver and it's good for 90 days. Some instructors will reissue the waiver for another 90 days in some circumstances.

[rchrds]

Andrew, I had a huge message with examples and stuff all typed out, but I lost interest in making the point.

Anyway, thanks for the thread, as this will quite likely get people thinking a little more about how they calculate their gas consumption, and perhaps think a little more about what they are doing before they commit themselves to a large dive.

Let me narrow my whole previous paragraph down to this-

You are not letting Murphy have a large enough portion of your gas supply. You can (and should) calculate gas consumption for large dives, but always add a fat portion for stuff you will never see coming, and by all rights should not happen. I've had enough completely stupid stuff happen that almost killed me, that I never could have planned for, and a fair number of "completely astronomical odds" events.

Anyway, something to think about, it used to be, (and its been a few years since I've dove with any) that the WKPP dove 1/2+2 on their stages- leaving backgas untouched. Which at first, didn't make sense, until someone clued me in that they also had SAFETY bottles, in addition to, (and actually in replacement of, in the case of emergencies) their regular gas supplies. Then it clicked- they didn't calculate that gas, but if needed, it could replace or supplement a threatened gas supply (and add additional regulators and bottles) so, in fact, they dove with large safety margins.

Anyway, already too long. Lets have more arguments like this.

[rchrds]

It was suggested that the rule of thirds be modified when diving solo. I'd like to hear suggestions for modifying this rule.

Oops- I completely lost track of the original point of this whole argument.

Like Andrew, let me draw some fire.

First, I will no longer solo backmount. All other commments are based on this.

I do not modify the rule of thirds solely based on being solo. Being sidemount, you cannot completely lose your gas due to one tank failure, as you can backmount (again, has that ever actually happened?) and ALL OTHER THINGS ACCOUNTED FOR you should barely have enough gas to exit with the loss of one bottle.

Actually, the only thing I modify the rule of thirds for (never more than 1/3) are siphon systems. I will turn early based on the perceived flow. Every other contingency (scooter loss is most common) I will plan for a swimming exit at maximum penetration. If the dive is very long I will usually drop a safety bottle somewhere at the equivalent penetration of 1/2 to 2/3 of that bottle.

Please keep in mind I am talking exploration here. If I am at Ginnie (not in the last 8 years), It's usually 1/3s plus 100 for peace of mind, or about the same at Peacock. It doesnt hurt my feelings to exit with 2100 lbs.

Jason

[skip]

First let me say, that I will continue to solo backmount, unlike jason.

However, here's the rub. When diving backmount and solo, I dive only the stage or stages, saving all, yes all, backmount gas for emergencies. I dive 1/2 AL80, in and 1/2 out. if carrying two, then half of one, drop it, half of second, and then turn the dive. backmount is for emergencies only, and since I backmount 120's or 130's there's more than enough reserve gas.

I also carry a small hand mirror so I can do my own bubble checks.

-skip

[Sludge]

I dive only the stage or stages, saving all, yes all, backmount gas for emergencies.

That's what I do, whether solo or not.