Just seeking some insight into proper procedure, comments are appreciated. I'm well aware of the rule of 3rd's, I'm curious is how you would actually apply the rule of 6th's in an actual overhead environment, please explain...
Rule of 6th's ????
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ucfdiver
Contributor
It just means limit your penetration to 1/6 of available gas. It's an arbitrary training guideline placed on intro divers from the idea that it's 1/3 the volume of a single tank.
Rule of 6th's is usually used to limit the penetration of an intro diver. They either dive to 1/6 the gas supply of a set of doubles or 1/3 of a single cylinder w/dual outlet. The main purpose is to prevent them from getting too far in and find themselves beyond their training and to provide plenty of extra gas to extricate themselves in the event of a problem.
ianr33
Contributor
And it applies to double tanks, so the same volume of gas would be used as diving a single to 1/3rds.
Cave Diver beat me to it.
Cave Diver beat me to it.
You are all so fast.
To be safe at Cavern or Intro on a single tank, you dive thirds. Why anyone would go into an overhead with only a single tank is beyond me, but that is besides the point. A third in, a third out, a third belongs to your buddy.
If you dive doubles, you want to be as closely matched to the single tank divers in you group, so even though you essentially have one tank of gas you are allowed to breath, you have the added redundancy.
Beyond Intro, and in some cases Cavern, you do not have to worry about sixths.
To be safe at Cavern or Intro on a single tank, you dive thirds. Why anyone would go into an overhead with only a single tank is beyond me, but that is besides the point. A third in, a third out, a third belongs to your buddy.
If you dive doubles, you want to be as closely matched to the single tank divers in you group, so even though you essentially have one tank of gas you are allowed to breath, you have the added redundancy.
Beyond Intro, and in some cases Cavern, you do not have to worry about sixths.
rickm21
Registered
I was taught that it was 1/3's even in doubles. You still need 2/3's to exit with a buddy even in doubles.
If you were taught this at the basic/intro level, you were taught wrong. I'm familiar with the standards of 6 different agencies and they all state 1/6s.
I'm not sure where this concept that 1/6ths "only applies to intro divers". It applies anytime you might want more gas to exit (can be any amount >1/3rds not "just" 1/6ths). New caves, no flow, poor vis, siphons, etc.
In most overheards 1/3rds is suicidally aggressive unless you've got flow or extra buddies to help your exit.
In most overheards 1/3rds is suicidally aggressive unless you've got flow or extra buddies to help your exit.
rickm21
Registered
Basic Cave Diving by Sheck Exley... Ten Recommendations... Rule 2; "Always use the 1/3 rule in planning your air supply."
I agree fully with the understanding that this is the upper (maximum/suicidal) range, and Exley stipulates that additional air should be reserved for current, visibility, restrictions, and decompress time.
I am intro only so I'm not questioning the 1/6th rule. But I did want to provide the standard I was using... for the sake of discussion.
ianr33
Contributor
Doesn't NAUI Cave 1 allow 1/3rds of doubles?
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