Intro Cave - Singles or Doubles

[alemaozinho]

good point

 

[jfoutz]

I was reading my TDI student outline in preparation for class next week and learned that the limits on intro are for a turnaround when 1/3 has been used (assuming you and your buddy have the same tanks). It also indicates that you use a value of 1/6 if using doubles.

It would seem to make sense then that an Intro diver using doubles would benefit from 1) increased safety since the second bottle is entirly reserved for exit/emergencies and 2) getting practice with doubles on your back while still in the intro stage (doubles must affect boyancy/trim etc.) 3) Time spent on the exit and exploring the entrance area would be GREATLY increased as long as your buddy has a similar config.

Thoughts....comments????

There’s really no additional safety gained from doing Intro in doubles. Unless you have a heart attack, your instructor will bring you out of the cave alive. Period.

The only real advantage to using doubles for an Intro class IMO is that it gives you experience with them in a cave if you are going to move on to Apprentice in a short period of time. And I think that advantage comes only if you’re already very comfortable in doubles.

Intro class is no place to start diving with doubles. There are a large number of skills you need to acquire over a fairly short period of time. Some of the skills are big and easy to master if you put your mind to it. Others are far more subtle. Fine tuning buoyancy is very subtle. There are subtle aspects to running a reel properly. Line etiquette can be subtle. Learning those subtle skills takes time, practice, and patience.

As for the, “as many curves as I can get” argument, I understand the premise, but the logic doesn’t actually follow through. If you have a good instructor, you’ll have lots of curves thrown into the class. I think it’s best to concentrate on those curves – there’s a reason for them.

You can strap a pair of doubles on for the first time in Intro and probably finish as a competent cave diver. Some will come out better than competent – many of us won’t. But if all you want to be is competent, I’d like to discourage you from even thinking about becoming a cave diver. I don’t want to be a competent cave diver. I don’t want to dive with people who only want to be competent cave divers. I want to strive to be a proficient cave diver. Every time I finish a dive I look at it and ask myself what I could have done better. Then I ask my dive buddies what I could have done better. Then I work on those things. I do this, and I’m still not anywhere near proficient. But I think that this kind attitude is the kind needed by cave divers who actually are competent.

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.

If you’re taking your course in singles you’ll most likely be renting either AL 80s or Steel 95s. Either way, you’ll be using H valves with DIN connections. Your yoke tank is just not an option. Also, depending on where you train, you’ll need at least two and as many as four tanks as there often is not a filling station nearby (e.g. Manatee).

Also, depending on your certification agency, your 130 likely wouldn’t help you out anyways. At the Intro level, NSS limits you to 30 cu. feet of gas for penetration. I’m not sure on what the standard is for other agencies.

If you’re doing doubles, you’ll probably want something larger than twin 72s for an Intro class.

 

[Jason B]

At the Intro level, NSS limits you to 30 cu. feet of gas for penetration. I’m not sure on what the standard is for other agencies.

NACD limit is 1/3 of single or 1/6 of doubles start pressure.

Jason

 

[StSomewhere]

Intro class is no place to start diving with doubles.

That was my instructor's response almost word for word. He doesn't allow doubles for intro unless you can already show proficiency in them. Funny that you can't do the apprentice without doubles, apparently that's the gap you have to fill in your own training. Makes sense to me.

Also, depending on your certification agency, your 130 likely wouldn’t help you out anyways. At the Intro level, NSS limits you to 30 cu. feet of gas for penetration. I’m not sure on what the standard is for other agencies.

:06: My copy of the NSS-CDS 2000 standards and procedures for intro says 1/3 for singles and 1/6 for doubles.

If you’re doing doubles, you’ll probably want something larger than twin 72s for an Intro class.

Just curious, I have two E7-100s on the way with an eye toward doubling them up at some point. In your opinion would that be sufficient for intro?

 

[scubafool]

I am going to do my Intro class in doubles. I have a set of HP 100's. 1/6 of 200 cubic feet is 33 1/3 cubic feet. 1/3 of 100 cubic feet is 33 1/3 cubic feet. I get the same amount of penetration gas, but with the doubles I have 166 2/3 cubic feet to exit & deal with problems that might arise. With the single I have 66 2/3 cubic feet to exit & deal with problems. If & when I pass my Intro class, I will be a NEW, INEXPERIENCED cave diver, prone to making mistakes. It is precisely at this time that I NEED a larger reserve. Diving in doubles gives me that reserve.

I agree that you should be proficient in doubles before you take Intro in them. There is enough to learn in 3 days without trying to adjust to doubles added in. The first dive of my class, I will ask my instructor to make a call then & there as to whether or not my skill level in doubles is up to par. If it isn't, end of class, I'll see ya in a month or two.

 

[Mark Vlahos]

As for the, “as many curves as I can get” argument, I understand the premise, but the logic doesn’t actually follow through. If you have a good instructor, you’ll have lots of curves thrown into the class. I think it’s best to concentrate on those curves – there’s a reason for them.

Do you mean one fin, no light, no mask? Or perhaps no light, no mask, air share? Or no light, (and then the instructor moves you several feet while disorienting you) lost line drill? Oh, just wait, it's lots of fun!

But seriously, about the others and the double tank questions... I did the entire track from cavern thru full cave in doubles, but I had been in doubles before. If you can manage it I would encourage you to take the entire series of dives in doubles, but plan on a few extra dives just in the doubles to learn how they affect your bouyancy and trim. Practice hovering nice and flat while still shallow. It is not easy, I still had problems with it, the large air bubble in the wing really tests your patience.

You might want to think about a plastic, or aluminum backplate for use with doubles. You really will not need the extra weight of a steel plate, especially not in fresh water.

Mark Vlahos

 

[GDI]

Hey Mark do you mean things like entangled diver, with no mask while OOA, and no lights, where do you come up with this stuff?

 

[Mark Vlahos]

Hey Mark do you mean things like entangled diver, with no mask while OOA, and no lights, where do you come up with this stuff?

Hi Rick,

Frankly I was a little surprised that you didn't spring it all on me during the last dive. Then it would have been...

No light
No Mask
Lost line
No fin
Air share
entangled diver, but I think you tried that when my safety reel started running, but not on that dive,
deco obligation, again we did have this at the end of the dive.
You could have undone my primary wing inflator.
And mabey put a big rock on my back between the tanks!

Is there more, bring it on, I love a challenge!

But even with all of that I don't think I would have freaked out. I would have been stressed but still determined to get out safely.

But heck, learning to deal with the stacking on of problems is critical. If you can deal with multiple problems, then one problem at a time is almost easy.

Again Rick, a nice big public thank you for your patience and skill. I enjoyed my dives, and feel I am a better diver in general and will be a good safe cave diver, largely because of you.

Mark Vlahos

 

[Divesherpa]

That was my instructor's response almost word for word. He doesn't allow doubles for intro unless you can already show proficiency in them. Funny that you can't do the apprentice without doubles, apparently that's the gap you have to fill in your own training. Makes sense to me.

This, IMHO, is the problem with diving a single. So, you are supposed to teach yourself the use of doubles? Why not start out with doubles from the Get-Go? Singles (again, IMHO) do not belong out of daylight.

I am very much in agreement with GUE's stance on this issue. Also, dude with the 72's, 144 ft^3 is at an amazingly low pressure, you get a little more breathing medium in your bottles in cave country.