roll on roll off

[ltb7733]

i went to beneath the sea in new jersey and had a blast. if you havent gone, try to make it at least once. anyway, i picked up a copy of IMMERSED, FALL 2003 and there was an article by jeffery bozanic on manifolds. I used to dive in new york in the early 90s with independent doubles. got strange looks from my fellow divers. like any other rig, it has its pros and cons. ( i didnt know it at the time, but i was practicing for side mount training by switching regs. some day i will get there) anyway, i was shocked to read that a whole artilcle was devoted to roll off problems. i thought that if you were having roll off problems i assumed:
1. you dont have your trim worked out

2. you are in a place too tight for a backmount rig and need to be in sidemount rig.

roll off problems tell me that the caves are getting damaged. Is this a real problem that we dont want to talk about, or its not really happening that often? then why a whole article on it? So i ask the cave divers whats the real story? thanks ltb7733

[curtschu]

Look at the IRAP and you tell me. There are a bunch in there about roll offs
Just about every cave has at least one spot that is "a little tight" This seems to be where roll offs occur. I don't think people are banging along the ceiling if so you’re right they got issues. This is why I think if someone came up with a positive but simply disengaged lock on the valve you might have a winner. There was a guy that posted about a design exercise he was conducting to address this among other valve related issues. He was thinking of a guard but I think that was the wrong course as he soon found out from the types pf replies he got. It also could be addressed with the position of the valve handles, how about pointing down at an angle say 30 deg. and forward at 5 deg the manifold would look kinda like a droopy dog’s ears this would change the angle that the handle hit and still allow easy access. Manufacturing might be the problem here.

Anyway that’s my two cents

[Sid]

Well I can't resist. Pretty much you can roll off the left post moving forward easily, especially if you got the soft rubber knobs, the right post will just get jammed on tighter if you hit moving forward. Not a problem if you can reach your valves, everytime you get near the ceiling or go through a restriction just check your valves and make sure they are open. If your hitting hard enough to bend stems (like a good wack when scootering) you need to develop better skills (don't know anyone who ever done this but...snicker). Also you can get really strange rolloffs rubbing alongside anchor lines in choppy water. Worst thing that happens is you suddenly got no gas, but it should be second nature which way to turn a valve back on if you practice and aren't too dislexic(sp?) BTW if you are moving at mach 2 or so exiting through the lips, etc at devils or someplace that low, might want to wait a couple of seconds before wedging you hand inbetween the valve and the ceiling and grinding off a finger, cave diver conservatism sort of.


Ahh that feels better. Sid

[Gary]

roll off problems tell me that the caves are getting damaged.

I would say that most roll offs are an indication that people are contacting the ceiling WAY too much and should be fixing something in what they are doing.

[jammer]

Well I have to say I was trained to check my air offten and everytime I check my air to check for roll off so it keeps you safe no problem it is now something I do without thinking twice about it. I know they make these neat little stainless knobs I have seen them on some rental tanks at the Dive Outpost.

[ARY]

Well I can't resist. Pretty much you can roll off the left post moving forward easily, especially if you got the soft rubber knobs, the right post will just get jammed on tighter if you hit moving forward. Not a problem if you can reach your valves, everytime you get near the ceiling or go through a restriction just check your valves and make sure they are open.

Agree. It is easy to detect roll off if you have inflator and SPG on left post: you suddenly loose air or find yourself face in clay which simply indicates recent roll-off (or true OOA ) Sidemounted tank also doesn't guarantee that you never shred stem. I had cylinder fallen into hole from my hands while i was pushing it through restriction, result-sliced knob (in opened position). Impact was very very little and apparently enough to cause a damage. After that i would rather hit ceiling with my head then touch it with valves.

[NitroxWarrior]

I've always been much more afraid of damaging the valve then having rolloff. I only use a guard because the thought of experiencing some sort of extreme loss of boyancy control(Such as drysuit over inflating) hit my valves on the ceiling and having a valve bust.

[John L.]

Welcome back Sid! Good to see you posting again.
John

[Stu]

I reckon there's another way to avoid this - at least to a large extent.

Mount your tanks inverted. I discussed this during my full cave class and got told the dreaded words "Bad student! Entanglement risk!" but the more I think about it, the more sensible it seems. ("Bad qualified diver!")

AFAIC, you're more likely to run into line which is drifting above your head. You drift into this valves first, then you've got all those strangely shaped bits of metal and rubber to get entangled as opposed to the rounded ends of a couple of tanks. Same with a roll-off. You're more likely to figure out that you want to be a little bit further from the ceiling when the part of the tank nearest the ceiling impacts, and that's generally going to be the bit above your shoulders. With tanks mounted "the right way up", you're going to start to roll off on that impact. With tanks inverted, you hit a big, round piece of metal that gently smooths away the ceiling above rather than digging strangely shaped holes in it.

For those of us like me who have enough trouble scratching our heads never mind reaching valves, mounting tanks inverted also makes a huge amount of sense. Now the valves are almost level with my arse, and while I may have wiping problems (seriously - what idiot thought white underwear was a good idea? ) at least I can reach around there to scratch. This means I can reach all the valves easily, and if anything there does get entangled, I can reach it without having to undo my crotch strap and waistband (usual method of reaching my valves) and work it out in comfort.

Another point with this - the fact that you're mounting your tanks upside down generally means that you'll need some sort of guard rail to sit them on. This should also help avoid roll-offs ever occurring, and though ("Bad diver!") it may be an entanglement risk, I don't see it as any more of a problem than the valves themselves.

[Sid]

I reckon there's another way to avoid this - at least to a large extent.

Mount your tanks inverted. I discussed this during my full cave class and got told the dreaded words "Bad student! Entanglement risk!" but the more I think about it, the more sensible it seems. ("Bad qualified diver!")

AFAIC, you're more likely to run into line which is drifting above your head. You drift into this valves first, then you've got all those strangely shaped bits of metal and rubber to get entangled as opposed to the rounded ends of a couple of tanks. Same with a roll-off. You're more likely to figure out that you want to be a little bit further from the ceiling when the part of the tank nearest the ceiling impacts, and that's generally going to be the bit above your shoulders. With tanks mounted "the right way up", you're going to start to roll off on that impact. With tanks inverted, you hit a big, round piece of metal that gently smooths away the ceiling above rather than digging strangely shaped holes in it.

For those of us like me who have enough trouble scratching our heads never mind reaching valves, mounting tanks inverted also makes a huge amount of sense. Now the valves are almost level with my arse, and while I may have wiping problems (seriously - what idiot thought white underwear was a good idea? ) at least I can reach around there to scratch. This means I can reach all the valves easily, and if anything there does get entangled, I can reach it without having to undo my crotch strap and waistband (usual method of reaching my valves) and work it out in comfort.

Another point with this - the fact that you're mounting your tanks upside down generally means that you'll need some sort of guard rail to sit them on. This should also help avoid roll-offs ever occurring, and though ("Bad diver!") it may be an entanglement risk, I don't see it as any more of a problem than the valves themselves.

You got to be kidding, right? So now to avoid a problem that doesn't exist, you got your valves and 1st stages getting smashed everytime you hall yourself out of a cave, do the death march and hit the picnic table or tail gate of the truck. As for entanglement, your not supposed to swimming under lines getting your manifold wrapped up, and if it's really low and the lines are all stuck in the ceiling, well don't go there if you can't help but get tangled. Much simler and elegant to just learn how to turn valves on and off. BTW I like dark red silk underware for several reasons (1) it feels gooooood (2) when you run into Gary solo diving with his independent transverse mounted tanks and you do get startled the stains are easier to hide/spotclean (3) silk will wick the sweat accumulated from the deathmarch away from the sweetspots into the drysuit underware. Ok I'm going to work on my dorsel mount rig now. Sid