Intro Cave - Singles or Doubles

[mavjax]

I want those training dives to have many curves as possible. There was a marked increase in my stability on my final dives for intro. Sometimes you just have to use the gear in the environment you are gonna dive with it in.

That's basically what I decided as well. I figured if I'm going to dive dry with doubles and eventually progress through deco and full cave, that I might as well invest in the gear now and use it, and be comfortable enough with it to complete intro before going any further.

 

[floydp75098]

Me personally I spent a year using doubles and a dry suit in open water prior to taking my Cavern course then completed all using doubles

 

[Jason B]

Well, since the thread has been resurrected already... I completed my cavern class in Feb. using singles. Big old cave bug bit me in the process, so obviously, Intro is in my future (already scheduled). My instructor recommended that I go ahead and practice diving doubles and running reels over the next few months until my Intro class dates. So I'm hoping to be comfy in them by then. So far, so good.

Jason

 

[Evans]

Apropos of this thread, I've been planning (forever) to put together a set of twin 72s for deeper rec diving here on Puget Sound. And if I make it out (as planned) to North Florida late this year I thought, why not take a Cavern/Intro course while I'm there and just use the doubles which I will by then be used to? But now reading this thread I see that the penetration limit for Intro is 1/3 of a single or 1/6 of doubles. This means if I take my yoke single with 130 cf of gas I can use 43 ft3 to penetrate. But with 144 ft3 in my manifolded DIN doubles I can only use 24 ft3 for penetration. Having not taken the course I am really not trying to make a point or anything, but on the face of it it does seem a little odd. I'd like to know the rationale behind this if anyone would explain.

 

[GDI]

Apropos of this thread, I've been planning (forever) to put together a set of twin 72s for deeper rec diving here on Puget Sound. And if I make it out (as planned) to North Florida late this year I thought, why not take a Cavern/Intro course while I'm there and just use the doubles which I will by then be used to? But now reading this thread I see that the penetration limit for Intro is 1/3 of a single or 1/6 of doubles. This means if I take my yoke single with 130 cf of gas I can use 43 ft3 to penetrate. But with 144 ft3 in my manifolded DIN doubles I can only use 24 ft3 for penetration. Having not taken the course I am really not trying to make a point or anything, but on the face of it it does seem a little odd. I'd like to know the rationale behind this if anyone would explain.

Ok Evans First of all you are not going to be allowed to use a YOKE in Intro so you will need to change the valve. One of the reasons of going to 1/6 on doubles is to equate the diver against someone who may be in a single for gas usage. The other is to limit penetration so as to reduce the chance of going into deco all while building up the divers skill and awareness levels

 

[StSomewhere]

OK, I've signed up for a cavern class and got some stringent feedback from the instructor and its a little different than what I'm reading here (from other instructors) so maybe you guys can set me straight.

Intro limits you to 1/3 of a single and by definition to 1/6 of doubles, this has everything to do with penetration limits being the same regardless of singles or doubles (GDI covered this). The doubles should not allow you to penetrate deeper than a single, but its OK to learn on doubles, correct? Also, singles for intro require an H-valve and two DIN first stages, correct? The regs are apparently the issue, since singles with H-valves are supposed to be easily rented in cave country.

Now for the main question. I was told that regardless of whether you trained for Intro on doubles, you are still 100% restricted as an intro diver to diving only singles. Only with a special exemption card are you allowed to dive doubles in a cave as an intro diver without an instructor, and this exemption is totally at the descretion of your instructor to determine if you are (1) safe with doubles and (2) if he believes you'll abide by the 1/6 rule. Did I misunderstand something? How common is this exemption?

FWIW, I was told to learn cavern (and later intro) with singles and when it comes time to doubles to learn that separately in open water before trying to apply that to cave diving, besides I'd have to get to apprentice (?) before I could actually dive caves with doubles anyway so there is no reason not to take my time. Then again, I'm obviously clear back at the "walking before running" stage.

 

[simbrooks]

Sounds about right, all the points made by your instructor are the same as other cave diving instructors seem to make. Some are more apt to give out the doubles exemption if they know you are ok in them than others.

The only reason you dive either in singles with H or doubles is for reg redundancy, not just cos there are plenty to rent - however in cave country there is a demand for them, so they are supplied/rentable - lets not put the cart in front of the horse here

 

[StSomewhere]

The only reason you dive either in singles with H or doubles is for reg redundancy

That's what I was trying to say. Before I get to intro I'll have to have two DIN regulators, but the H-valve tanks (and maybe doubles?) are widely available for rental so they aren't so critical to own at the cavern/intro level. OTOH, I'm completely new to this so feel free to correct me at any and every turn.

 

[akioMtFuji]

I recognize that 1/6 is only a TDI Intro diver.
Other Agency are A miniature double tank.
Is it correct with this standard?

 

[simbrooks]

Before I get to intro I'll have to have two DIN regulators, but the H-valve tanks (and maybe doubles?) are widely available for rental so they aren't so critical to own at the cavern/intro level. OTOH, I'm completely new to this so feel free to correct me at any and every turn.

They are available for a price. I went ahead and got some in the end thinking i would get plenty of use out of them and they were going cheap!! If you havent tried them before, rent a few different sizes, 85, 95, 104, 108, 120, 130 etc and see what seems to fit you - others might have suggestions on sizing for your bodyframe, the length of time you might need them etc. I found HP-120's fit me fairly well, but i am taller than most. Get someone out there with you who can give you pointers and see your form in the water with the tanks before you do the cavern/cave in doubles. Singles is no big issue, just get the larger ones, usually 95's or 104's for rent from what i have seen (never rented any of those).