Inverted Twins - Cave Agencies

[MarkP]

Originally Posted by neilh

Sorted in what way? If they have that mentality would they "sort" themselves on a single? Is that an issue.

It's as Jason said - you can't easily get yourself into THAT much trouble quite so easily on a single. You might well have the correct mentality to progress safely, but there are divers who don't.

Example - doing the Elk as a second dive, I was expecting to spend quite a lot of time there - loads of 'branchs on the stern. I'd done a quick, for me, circuit and was surprised to see one of the divers from the boat by the line, agreeing with his buddy to set off to do another circuit. We'd been down for about 15-18minutes, so I asked to see their gauges. Diver "a" had a computer showing 1 minute NDL and diver "b" was showing a stop. I sent them up. In the pub we chatted about it: "And you had just a minute of no decompression time." "Oh, is that wat that means?"

Now if he'd has a twinset he'd have argued the toss about being sent up - he thought I'd sent him on his way because he only had 90 bar left.

[neilh]

Originally Posted by Steve S

Wouldn't that be sub-optimal?

Clearly - but if you're too inflexible or tight to mount them the right way up...
(For those that miss the smiley this is a bit of ironic jest!)

Originally Posted by MarkP

Now if he'd has a twinset he'd have argued the toss about being sent up - he thought I'd sent him on his way because he only had 90 bar left.

I'm not sure how the ability to shutdown or not would affect this individual though - they had no idea they were about to get into a deco situation on a single so it sounds like they need quite a bit of supervision just being underwater. You could argue that had they been on a twinset and had done another circuit then at least they could have had enough gas for a controlled ascent with appropriate stops?

[tom]

Originally Posted by neilh

appropriate stops?

<fx: hollow laughter>

If they can't work out what their computer is telling them, are they likely to be doing appropriate stops? or just their usual 3@5 or whatever?

[MarkP]

Originally Posted by tom

<fx: hollow laughter>

If they can't work out what their computer is telling them, are they likely to be doing appropriate stops? or just their usual 3@5 or whatever?

Exactly.

[neilh]

Originally Posted by tom

<fx: hollow laughter>

If they can't work out what their computer is telling them, are they likely to be doing appropriate stops? or just their usual 3@5 or whatever?

They'll be doing more than they would with an empty single

[iainmsmith]

Originally Posted by nigelH

I'm not so sure about two and a bit meter ones if we're talking entanglement unfriendly environments. How long a hose do you need so that the donor's ears aren't in the cusp of a frog kick?

In my (very limited) cave experience, when we were going through a restriction while air sharing and blind in one of the cenotes (I'm pretty sure we ended up going through something narrow that wasn't a restriction when one could see, but seemed very much smaller and nastier when it was all black!), when donating, you're in touch contact with the diver in front. This can be hand-to-arm if there is space, or hand-to-lower leg (just below the knee) in the above situation. In that sort of cave, a diver is using much smaller kicks anyway in order to avoid kicking the cave and bringing more stuff down, not to mention avoiding kicking his buddy in the head.

There are definitely times that one lets go of the diver in front (for example, to negotiate a station). You find them on the line up ahead of you again. However, the idea of being the recipient in an OOA situation while "riding your bull bars" makes me really uncomfortable. If we need to be in that configuration because it's that tight and I lose that reg, you may not have room to turn round to help. You can't get to me. If I'm behind, I'm much more likely to be able to get my hand up to your mouth with a reg in it.

A 3m (or whatever) hose might work on inverts to allow that donation (but see my previous post about the complete PITA that it would be to try to sort out a complex failure). The only way I can see of stowing it would be laid against the tank under bungee. Seeing Jingle failing to deploy such an arrangement while attempting to demonstrate its "superiority" at LIDS one year was enough for me not to want to "stuff". Maybe running the long hose up between the cylinders, then bringing it out past the right shoulder and wrapping it might work.

Then again, if one dives with normally arranged tanks, 7s, 12s, 15s, 18s, or whatever work the same way. Inverted 18s would be amusing to see...
So I would suggest that inverts limits diving in a way that uprights don't.

Iain
(who is very aware of the risk of coming across as "I've just done Cave 1 therefore know all about cave diving"...because I'm even more aware that I don't. Then again, I'm also aware that I've got two perfectly functional shoulders, so perhaps have less of a motivation to find an effective way of using inverts.)

[Guy Wallis]

I spoke to Mark P at the dive show in London and he mentioned this. I realise that I am coming in to this a bit late but I teach TDI cavern to full cave and don't see a problem with inverted cylinders. I'd certainly be happy to run a cavern course and see how it works out? If you are interested e-mail me. Details on deeptech.co.uk web site.

[Guy Wallis]

Just finished teaching a diver with inverted cylinders. He had them inverted due to a shoulder injury. Here are some pros and cons. He could reach the valves easily and although he had to have a pillar valve gaurd (potential line trap) he could reach back and clear it if need be. On the down side; the 2m long hose was not long enough for an air share with the out of air diver in front of the doner. There were problems restowing the long hose after an S drill (as about a foot of hose had to be stowed under bungies on the cylinder). One of the direct feeds had to be tailor made. After he completed Cavern I had no problems taking him on Intro Cave. I took a few photos of his kit set up. If anyone is interested contact me via the deeptech.co.uk web site.

[Steve S]

Originally Posted by Guy Wallis

Just finished teaching a diver with inverted cylinders. He had them inverted due to a shoulder injury. Here are some pros and cons. He could reach the valves easily and although he had to have a pillar valve gaurd (potential line trap) he could reach back and clear it if need be. On the down side; the 2m long hose was not long enough for an air share with the out of air diver in front of the doner. There were problems restowing the long hose after an S drill (as about a foot of hose had to be stowed under bungies on the cylinder). One of the direct feeds had to be tailor made. After he completed Cavern I had no problems taking him on Intro Cave. I took a few photos of his kit set up. If anyone is interested contact me via the deeptech.co.uk web site.

Thanks for that mate, it's good that there is some accurate information being posted so people can make a choice.

Safe diving,
Steve

[big_si]

Originally Posted by Guy Wallis

Just finished teaching a diver with inverted cylinders. He had them inverted due to a shoulder injury. Here are some pros and cons. He could reach the valves easily and although he had to have a pillar valve gaurd (potential line trap) he could reach back and clear it if need be. On the down side; the 2m long hose was not long enough for an air share with the out of air diver in front of the doner. There were problems restowing the long hose after an S drill (as about a foot of hose had to be stowed under bungies on the cylinder). One of the direct feeds had to be tailor made. After he completed Cavern I had no problems taking him on Intro Cave. I took a few photos of his kit set up. If anyone is interested contact me via the deeptech.co.uk web site.

Originally Posted by Steve S

Thanks for that mate, it's good that there is some accurate information being posted so people can make a choice.

Safe diving,
Steve

That's good. Steve, have you had the same issues that Guy's student had (long hose not long enough for donation in that team config / stowage of long hose)?

If not, how have you configured your kit to avoid it? Or if you do have the same issues have you any ideas on how people could configure their kit to avoid it?

Si