Thoughts on post roll-offs and first stage hose routing

[Tortuga68]

I guess that (push method) would work well so long as you weren't going into the flow

I'd be hesitant to use this method. Individual divers verifying the line for themselves reduces the chance of mistakes. There may be an instance where a tie off goes in more than one direction. i.e. two passages intersect. If the first diver makes a navigational error, the second diver is essentially on a "trust me" dive if they allow their hand to be placed on the forward section.

I understand your point - although in the course there was only ever one line, which we had layed - but if there's a branch then there should be arrows? If you were following permanant line and/or line layed by another team maybe not

To clarify, the following diver was only guided to the immediate other side of the wrap/tie-off. The necessity for this could partially be avoided by correct ties (so that the line was continuous without going around/behind the wrap point) but there could still be a line trap. The idea was to avoid a delay for the second diver that the first diver had already overcome

 

[Cave Diver]

I guess that (push method) would work well so long as you weren't going into the flow

Inside a wreck there usually isn't a problem with flow. Inside of a cave, if you're in a position where you're doing a blind line following exit, the flow will normally be pushing you. There are some exceptions, such as a low flow cave, or if you're diving in a syphon but typically you're going to plan a bit more conservatively in those instances.

I understand your point - although in the course there was only ever one line, which we had layed - but if there's a branch then there should be arrows?

The difference between theory and practice...

If you were following permanant line and/or line layed by another team maybe not

To clarify, the following diver was only guided to the immediate other side of the wrap/tie-off. The necessity for this could partially be avoided by correct ties (so that the line was continuous without going around/behind the wrap point) but there could still be a line trap. The idea was to avoid a delay for the second diver that the first diver had already overcome

That's part of the planning process in having adequate reserves. The one minute delay for both divers to follow a continuous line around a wrap or tie off point is much less an inconvenience than the potential several minutes lost by making an incorrect navigational decision. If you're comfortable allowing your buddy to make that decision, great. But should you ever find yourself diving with me under those conditions, know that I will verify your decision if you're in the lead and i will wait for you to verify mine if I'm leading.

If you know for a fact that this is the only line in the environment you're diving it's not that big a deal. In many of the ones I dive, there are potential for multiple lines and there are no guarantees someone hasn't come behind us and used poor technique and crossed our line, or used the same tie off point.

It really all comes down to what level of risk you're willing to assume. I prefer to minimize it wherever possible.

 

[Tortuga68]

Individual divers verifying the line for themselves reduces the chance of mistakes. There may be an instance where a tie off goes in more than one direction. i.e. two passages intersect. If the first diver makes a navigational error, the second diver is essentially on a "trust me" dive if they allow their hand to be placed on the forward section.

If there are no arrows, how do you know the first diver made an error?

 

[Cave Diver]

If there are no arrows, how do you know the first diver made an error?

Because if you physically follow the line around the tie off point with your hands you can tell if its continuous or not. If you find that another line is tied into it, or that intersects it in some way, but doesn't connect to it then you know that is not the line you've been following.

 

[Tortuga68]

I'll take your word for it - I'm not sure I could find a knot in a line in zero viz and determine which of the two offshoots of the line was the branch and which was the continuous line. I'd be hoping for a couple of arrows

If it was two lines crossed, sure, and not passing the following diver over the junction makes sense in that case - let them check and judge it themselves, both for their own satisfaction and to confirm your decision

 

[Ste Wart]

Most cave divers I know usually do a check anytime they contact the ceiling as soon as they're past the restriction.

But allow me to run a scenario by you. You're exiting a tight restriction with an OOG diver (upstream cow comes to mind). Your long hose is on your left post and the passage is tight enough to restrict your movements. You contact the ceiling and the post rolls off, maybe not completely, but enough to cause breathing resistance. Now the diver ahead of you is blocking your progress because they're excited due to difficulty breathing. You can't push past them, and if you pull back, you're gonna yank the reg out of their mouth. You don't know *why* they're excited, because you can breathe just fine. And the restriction is tight enough that you can't easily reach your valves to check.

What do you do?

Good one.

And a point a that is hard to argue. However equally, who says that the OOG was behind you when he signalled? Maybe he was the team leader and is now sharing air behind you and can signal if the air is cut off. There are many 'what ifs'

 

[Cave Diver]

Good one.

And a point a that is hard to argue. However equally, who says that the OOG was behind you when he signalled? Maybe he was the team leader and is now sharing air behind you and can signal if the air is cut off. There are many 'what ifs'

By putting the OOG diver ahead of you, you allow them to set the pace and reduce the chance the reg gets pulled out of their mouth. By using a right post long hose you put the diver who has the gas as the one in charge of the valve. If they have a roll off, they are the one with immediate control to fix the problem.

If the previously OOG diver who is now on your long hose has a second OOG experience because the post rolled off, they are more limited in how they can deal with it, and potentially more apt to panic finding themselves in two back to back OOG scenarios.

Forcing the diver on the long hose to have to signal out of air, then the other diver react figure out how to react to it prolongs the response time.

 

[Ste Wart]

By putting the OOG diver ahead of you, you allow them to set the pace and reduce the chance the reg gets pulled out of their mouth. By using a right post long hose you put the diver who has the gas as the one in charge of the valve. If they have a roll off, they are the one with immediate control to fix the problem.

If the previously OOG diver who is now on your long hose has a second OOG experience because the post rolled off, they are more limited in how they can deal with it, and potentially more apt to panic finding themselves in two back to back OOG scenarios.

Forcing the diver on the long hose to have to signal out of air, then the other diver react figure out how to react to it prolongs the response time.

I'm throwing in scenarios.

If a cave was so retrictive (sp?) and the leader was the OOG then surely it would be impossible for him to take the lead. Therefore would there not be a need to have a signal for either: a: hey, you just pulled the reg from my mouth or b: No gas from your donation?

 

[Tortuga68]

who says that the OOG was behind you when he signalled? Maybe he was the team leader and is now sharing air behind you and can signal if the air is cut off

I think the point is that you would re-order the team to put the OOG diver in front (of the donor) when that happened

 

[Cave Diver]

I'll take your word for it - I'm not sure I could find a knot in a line in zero viz and determine which of the two offshoots of the line was the branch and which was the continuous line. I'd be hoping for a couple of arrows

Even if you can't determine which branch to take, you would know that you just made a navigational decision. Mark the line that you're currently on (cookie) before proceeding in one of the two(+) alternate directions. If you fail to find a navigational marker in a reasonable amount of time, return to your cookie and try the other line.

The main takeaway from this scenario is that both divers are aware that a navigational decision was made. If the lead diver places the hand of the last diver on the "new" line, then the second diver may be unaware that such a decision was made. If the lead diver later loses confidence in his decision and attempts to turn around, the second diver will be more likely to be confused to the reasoning.

Further, since turning around will reverse the team order, when the second diver (now leading) comes back to that decision, if they find the alternate line, they may think they have come to a different point since they weren't aware of it from the beginning.

As I said before, this is not a common scenario, but I've seen several tie off points where it could become an issue. I'd prefer to err on the side of caution by having each team member verify the line than save a couple of seconds by making the decision for them.