Cavern In Doubles?

[GDI]

Actually, I would personally consider a single 190 a safer rig than double 35s. So I guess it depends...

Actually the double 35's are two small as the minimum gas required is 72 cu ft sorry you miss out by two cu ft

 

[Daedalus]

Going further doesn't necessarily make it more dangerous - I believe in the rules of no jumps, tees, etc - but limiting gas is just an attempt to keep people from getting to jumps, tees, etc to keep those not trained from using them.

In short I believe the prudent rule should be Intro - stick to mainline. Full - navigate to level you feel comfortable.

1000 feet back and not responding properly to a problem is just as dead as 2000 feet back.

I disagree, distance is definitely a factor. Someone who has a problem 2000 feet back has a long swim out ahead of them. Every 100 feet is an opportunity to come upon something that delays you or causes new problems.

 

[Kendall Raine]

Any agencies allow cavern to be done in doubles? Thanks.

I assume your question is in context of a class. I did Intro through Full in doubles, including at Ginnie (CDS). That was in '96 so site rules may have changed. I can understand why a site would prohibit use of doubles if you only have an Intro cert, but I can't understand the logic applied to an Intro class where you're under the supervision of an instructor who, by necessity, is Full Cave at a minimum.

If an instructor or agency does not allow you to take an Intro class in doubles I'd find another instructor or agency.

 

[GDI]

I agree Deadalus. However I feel the extra redundancy should be a requirement even at the intro level. You can get a long way back in a system on 1/6 of doubles. Going further doesn't necessarily make it more dangerous - I believe in the rules of no jumps, tees, etc - but limiting gas is just an attempt to keep people from getting to jumps, tees, etc to keep those not trained from using them.

In short I believe the prudent rule should be Intro - stick to mainline. Full - navigate to level you feel comfortable.

1000 feet back and not responding properly to a problem is just as dead as 2000 feet back.

My wife and I did cavern/Intro in doubles.

Timle this is not pointed at you specifically please take no offence by it as I am just using your statement as the typical example of Intro Diver thinking.

Intro is not just about the amount of gas you have on your back. yes one can get a long way back on a 1/6 of doubles and 1/3 of larger singles. You also need to look at your DECO status. The FACT is that if you are pushing that way on a single you are most likely to do the same on doubles. Intro to Cave is also a time related dive in that deco is not permitted.

Example: A 100 ft dive permits 20 minutes of BT. You take 5 minutes to run your reel to the main line and tie off. you now have 15 minute remaining to be back at the reel and starting your ascent. That is 7.5 minutes of penetration in and 7.5 minutes out (assuming no current flow) If you are just looking at your gas supply as a limit to your dive then I would suggest that you rethink your intro level diving practices.

 

[timle]

No offense taken - its just an over generalization and an assumption that I don't factor NDLs into my dives. Which couldn't be further from the truth, but apparently help you make your point.

 

[WD8CDH]

Actually, I would personally consider a single 190 a safer rig than double 35s. So I guess it depends...

Hopefully, you mean with an H valve and two good, well maintained regulators, not with is single junk regulator.

Personally, I would consider two skinny 50s on a double outlet manifold as safe as a single 100 with an H valve.

I don't think the 190 is safe for any diving other than a stage bottle since it is about 50 pound negative.

It sounds like the agencies are trying to control the dives by gas capacity but they are trying to control gas capacity by the number of tanks rather than the tank volume.

 

[Mike Edmonston]

GDI hit the nail right on the head.

It's really about bottom time and NDL's. A new diver with doubles can find himself in real deco trouble if he's not careful. I believe the 1/6 rule is there to minimize this, not to shorten the length of penetration. (That really sounds dirty doesn't it... )

Cheers

 

[WD8CDH]

Actually the double 35's are two small as the minimum gas required is 72 cu ft sorry you miss out by two cu ft

Hi GDI,

Is that a nominal 72cu ft or an actual 72 cu ft?

Most 72's are less than 72 cuft and my 35's are really over 36 cuft each.


My "intro" cave dive was in 1973 so I haven't been doing any intro diving for a very long time.


I firmly believe safe diving requires not exceding the limits of either your training or your equipment but I see stating "no doubles" as a way of "looking" like safety is being addressed while not actually addressing safety.

I have almost always prefered skinny doubles over a normal single of the same capacity for just about all of my diving.

 

[DeepSeaExplorer]

Hopefully, you mean with an H valve and two good, well maintained regulators, not with is single junk regulator.

Personally, I would consider two skinny 50s on a double outlet manifold as safe as a single 100 with an H valve.

I don't think the 190 is safe for any diving other than a stage bottle since it is about 50 pound negative.

It sounds like the agencies are trying to control the dives by gas capacity but they are trying to control gas capacity by the number of tanks rather than the tank volume.

No, sorry I didn't... I don't think much of your double 35s scenario in the cave - sorry! I suspect that you wouldn't really choose to do that either.

I wouldn't choose either, but given the choice between the two options, I'll err on the side of volume...

You brought up buoyancy. Assuming were still talking about cave diving, on top of everything else, the 35s don't have sufficient weight to offset the exposure suit, resulting in creating trim problems as well. I certainly would not invest the time and effort trying to trim them out. On the other hand, it could be an awesome setup for a shallow reef dive.

I too have issues with the method used to attempt to limit penetration, but I also see a lot of divers trying to learn how to use doubles on the Internet. I personnally think that they should NOT be learning to use doubles and learning to cave dive at the same time. In fact, I would not allow Intro diver to use doubles in the cave, even during a class, unless they have prior training from another course in the use of doubles.

How's that for a radical opinion?

Because here's what happens...

- Diver takes cavern and maybe intro in a single tank
- Diver reads about diving doubles on Internet
- Diver finds "good deal" on a set of doubles, again on Internet
- Diver begins doing cave dives with doubles
- Diver begins exceeding training limits excessively
- Diver gets away with it for who knows how long...

 

[ianr33]

GDI hit the nail right on the head.

It's really about bottom time and NDL's. A new diver with doubles can find himself in real deco trouble if he's not careful. I believe the 1/6 rule is there to minimize this, not to shorten the length of penetration. (That really sounds dirty doesn't it... )

Cheers

In Florida maybe.

In Mexico with an average depth of maybe 20 feet deco would not seem to be much of a consideration.....................