Needed for Cavern??

[PfcAJ]

I never dive solo, and sharing gas on exit isn't something I want to do (unless I have to...beats drownin!).

You aren't from Central Florida! Get outta here!

 

[ianr33]

I never dive solo, and sharing gas on exit isn't something I want to do (unless I have to...beats drownin!).

You aren't from Central Florida! Get outta here!

My my !

 

[ucfdiver]

Aren't you a cave diver?
If you lose the right tank, breathe off the left regulator. If you lose the left tank, breathe off the right regulator. You're not going to donate anything. You had the failure.

If you dive 1/3 of your air in, and at your max penetration you lose half of your remaining air, how much air do you have left?

1/3 of your air used, leaves 2/3's exit gas. Then tank loses a burst disk (about the quickest loss of gas I know of) and you lose one tank. If you are diving independant doubles how much gas do you have left? 1/3. Which if flow is at your back, should get you out.

Now, you are excited, a little freaked, and a burst disk has really screwed up vis. Is 1/3 enough air to get you back out? That's why alot of people dive 1/3 +

If you are diving isolator manifold, how fast can you shut a manifold?

FWIW I recently was diving SM in a river cave in cave country and had a low pressure hose fitting fail on me (where it connects to the reg) while I was on the line in a siltout. I think it got tangled on a rock I was beside, but I couldn't see anything so I really don't know. It startled me, and while shutting the valve down, I pulled a bit on the line which snapped. So I got to sit there, waiting for the silt to clear so I could stand a chance of finding the line, knowing that I only had enough gas to swim out at the same rate that I swam in at. Had this dive been done in isolated BM doubles I would have had 2x the gas needed because the shutdown would have saved the gas. This theory that SM is safer from a gas management point of view is entirely false, every failure I've ever heard about FIRST HAND is solved with more gas left over in BM than SM.

BTW, Had I dove to 1/3rds I would be dead.

 

[The Chairman]

So far, I haven't had that severe of a dangly or broken a line! But I do get your point. The most common failure we encounter are with regs. BTW, if you had to use that air, I bet you would have found a way.

 

[ucfdiver]

So far, I haven't had that severe of a dangly or broken a line! But I do get your point. The most common failure we encounter are with regs. BTW, if you had to use that air, I bet you would have found a way.

Grab a canoe and go dive each spring you see along the river, it'll change your view on cave diving...has mine at least.

 

[halocline]

I'm convinced that completely independant doubles are probably the best way to go. It negates the use of at least 4 orings necessary by installing an isolator. I gotta switch to sidemount.

Well, the problem with this idea is that the o-rings you're referring to are in series, not parallel configuration. That means that ALL of the o-rings on one side of the isolator must fail, not any of them, for that tank's gas to be lost. IOW, more o-rings in this case means less chance of failure, not more.

 

[Superlyte27]

FWIW I recently was diving SM in a river cave in cave country and had a low pressure hose fitting fail on me (where it connects to the reg) while I was on the line in a siltout. I think it got tangled on a rock I was beside, but I couldn't see anything so I really don't know. It startled me, and while shutting the valve down, I pulled a bit on the line which snapped. So I got to sit there, waiting for the silt to clear so I could stand a chance of finding the line, knowing that I only had enough gas to swim out at the same rate that I swam in at. Had this dive been done in isolated BM doubles I would have had 2x the gas needed because the shutdown would have saved the gas. This theory that SM is safer from a gas management point of view is entirely false, every failure I've ever heard about FIRST HAND is solved with more gas left over in BM than SM.

BTW, Had I dove to 1/3rds I would be dead.

I believe that is true with all failures except a burst disk failure. Burst Disk failures scare me.

 

[Superlyte27]

Well, the problem with this idea is that the o-rings you're referring to are in series, not parallel configuration. That means that ALL of the o-rings on one side of the isolator must fail, not any of them, for that tank's gas to be lost. IOW, more o-rings in this case means less chance of failure, not more.

It's still a failure point. If there were 0 orings to fail, there is no point of possible failure. An oring that doesn't exist cannot fail. Did I say that enough to get the point across? A single valve only has two failure points. At the neck, at the reg.

A manifold can fail at the neck, at the reg, at the left side of the isolator, at the right side of the isolator.

 

[PfcAJ]

Don't forget the bonnet o-ring. I've had one go on my backgas before (on the surface) following a rebuild.

 

[FritzCat66]

Another diver here who got Cavern certified (SSI, but using the NACD manuals), but has no interest in cave or deco or doubles. There are lots of great caverns in Florida, and having that cert opens a lot of them up to a diver where plain OW or AOW would keep them inaccessible. The training is actually very worthwhile, too - especially all the line handling.

Regarding the OP's query about gear for cavern: For both my cavern training and subsequent cavern dives, I basically just use my open water setup, although I switch the mount on my DiveRite LED700 from normal flashlight mode to Goodman. Also, I just borrow a primary reel from one of my techie buddies. However, my OW rig is already pretty "tucked-in" and has a long-ish 5' underarm hose and spring straps. No need for the polespear or safety sausage either. Decked out in tropical gear will definitely make you more "colorful" compared to all the black Borgified techie divers typically lurking around the caverns, but as always it's fun to meet and talk with them anyway.

One big difference for me is that normally I'll dive solo or with a "same ocean" buddy, but cavern for me is strictly buddy diving. I still carry my bailout pony, but when caverning keep to the rule of thirds.

Also, while I take my camera with me all the time to the reefs, I don't bother with it in the caverns because 1) it's just something else to get tangled in line, and 2) there's not much to my eye worth photographing in caverns anyway.

I'm still basically a reef guy, but the caverns are sometimes a cheaper dive option and better than not diving at all. They're kind of interesting, too, especially the ones with fossils, but still don't even begin to hold a candle to the reef. The freshwater makes for a good gear rinse dive, tho (except some of them will fill you with sand).

Nice thing about Central Florida is you can easily do either a cavern or a reef - or both - on any given weekend. Just having the option makes the Cavern cert worthwhile if you're in this area.