Underwater rambling Lot 2008

[terminalsump]

Some = enough, but not plenty. You always remember those moments

Prehap's should have turned on 1/4's rather than 1/3's

Tim

[cgrosart]

Or gone to the pub
x

[Duncan Price]

Perhap's should have turned on 1/4's rather than 1/3's

That is what is recommended for scootering - or even more conservative.

Or were you using the Jones's 1/3's rule: 1/3 in, 1/3 out and 1/3 for decompression?

[AMW]

The lines up to the Poumayssen are it seems always interesting , My self and Colin did the through trip a few years ago just as a tourist bimble

We had a couple of things going for us one was 20M+ vis the other was Al Wallace who with Sues help dived from the Poumayssen end to check the lines and place a light stick on the line below the rift up to show the route was Ok.

The dive through was Ok and rather than surface and have to carry the gear over land we scooter back to the Cabouy entrance. The vis was so good we could scooter flat out

Better luck with the lines and vis next time.

Andrew.

[NotDeadYet]

Carry over land??? I've driven down to Poumayssen in a transit van. The three point turn in the forest is interesting but it's a do-able drive. OK, it was a hired van, if it was mine I might be less keen

It was 20m+ last October. I was seriously pissed off, I'd dumped the scooter in the entrance because the vis was so bad but after about 200m it opened right up.

Looking upstream, there is a shelf in the top left of the passage which has (or at least had) a reasonably laid line through the final third. The main line is shite and there's not even the excuse of whoever laid it being narced out their tree. IIRC it joins on to the line which reaches the Poumayssen T.

Margins on a scooter are always hard to calculate. Losing a scooter isn't a major event, losing the ability to scooter is.

Cheers,

Stuart

[cgrosart]

We were both using 15s, which should be enough margin to do the through dive and back WITHOUT scooters. What that doesn't take into account is the deco, which as Stuart says, is very hard to work out.
We did NOT plan to do the through dive - rather get to the first line break (which we knew about as Clive and Rick had been in the Poumayssen earlier in the day and reported no downstream line could be seen) and patch it up as far as we could. If we found it, then great. If not, we would do what we could and turn back. This is what happened. We spent longer than planned fixing the lines at the far end, thus clocking up twice as much deco than we expected and had a mind-concentrating dive home in poor viz. We stayed together incase of a scooter breakdown. We had pushed the dive to thirds which did not leave us a comfortable margin for the surprise deco (that said, we did deco to the most conservative computer and could easily have surfaced according to my back up computer or Tim's Aladdin earlier and perfectly safely - but we had the gas to spare, so we stayed at 3m until all computers cleared). I came out with a total of 100 bar and Tim had about the same, maybe a little more.
It was the 'What if' factor which shook us. What if one of our cylinders went down ? We'd have had an interesting deco, but knew that we were ready to bail the other one out in order to complete deco.
I have never used 1/3 in, 1/3 out, 1/3 for deco as the extra third is for emergencies - not bloody deco !!! I normally carry or drop off a 7l stage for this. A line tangle, or a cylinder going down is why I keep a third back. The mistake we made was allowing the dive to go to thirds, thinking we would have less deco than we actually had. Bearing in mind the dive home was downstream and we had no line-patching to do, thus it was significantly quicker. We had discussed dropping a deco stage off the gantry at 3m and didn't do it - thinking that 15s would be adequate. This was a mistake. It becomes even harder to calculate when you consider that we dropped the scooters off at the 700m point (much earlier than expected) and swam from there due to having to patch up lines and swim due to poor viz.

[NotDeadYet]

Much as I hate to admit it, I like the DIR idea of using stages for scootering and keeping the twinset for emergency. My big worry on a scooter is being forced off it, bad vis for example. A failed scooter is a problem, fair enough, but not if you tow a scooter or can double up on someone else's. Scootering in but not being able to scooter out is a biggie though. No amount of spare scooters or being towed will help, it all comes down to how much wind you have.

For a bit of kit that can get you into serious trouble scooters seem to fail a bit too frequently for my liking. Even my previously uber-reliable Silent Sub flooded before I even reached the entrance of the Ressel in June. I've seen a group of three divers get in the water and come out with one working scooter. They just don't seem to be able to live up to the reliability required and I like having a lot more wind than I need when I'm using one. If I could get the lifespan of a rebreather with the simplicity of a twinset then it would be the perfect tool for scootering (I know someone is going to chime in with "RB80" ).

I don't use a computer, they only worry me

Cheers,

Stuart

[Clare]

Much as I hate to admit it, I like the DIR idea of using stages for scootering and keeping the twinset for emergency. My big worry on a scooter is being forced off it, bad vis for example. A failed scooter is a problem, fair enough, but not if you tow a scooter or can double up on someone else's. Scootering in but not being able to scooter out is a biggie though. No amount of spare scooters or being towed will help, it all comes down to how much wind you have.

Couldn't agree more. We talk about scooter failures and redundancy, but when the whole team has to come off the trigger on exit things can quickly get tight whatever the reserves. We scooter x times quicker than we swim, we come out in touch contact x times slower than we swim. Doesn;t take a maths genius to work out that whilst we can come up with strategies for dealing with this (using stages and bakgas in reserve is one) essentially the loss of the ability to scooter will blow holes in all but the most conservative gas plans.

(I know someone is going to chime in with "RB80" ).

To be honest, when I was back in Hole in the Wall and making such slow progress, it was the first and only time that trip I wished I had the damn thing with me.

[Duncan Price]

I came out with a total of 100 bar and Tim had about the same, maybe a little more.

Was that 50 bar in each tank then?

[cgrosart]

Just to clarify (cos it's not that clear) we did actually scooter all the way home in shite viz. But we were very, very careful. The only bit we swam was the final 300m at the Poumayssen end and back until we picked our scooters up again. Using a one-speed (bloody quick) zepp, I had no options to scooter slower according to conditions so I went home out in front and waited for Tim on the Silent Sub whenever I got to a belay at right angles to make sure he didn't overshoot it. We stuck together (within 20m of one another) incase either of us needed a tow. Luckily, both scooters performed properly. One scooter breaking down wouldn't have been the end of the world, one cylinder going down would have meant a bit of an uncomfortable deco - worst case scenario, one of us could have been sat in the tent on 02 afterwards, if we had had to cut deco short.
We had a good dive debrief afterwards and learnt a lot from it. I think the outcome was that we should not have pushed the envelope with the impending deco we had. It was also our second cave dive of the day and from a personal point of view (this does not necessarily reflect on Tim) I had taken on too much in one day and wasn't thinking as straight as I might have otherwise. I should have called the dive far sooner, but chose not to. That was my big mistake.