Clare Gledhill (Online)

I posted this on YD in response to various comments about how any saw toothing at all was dangerous. It was suggested that other cave profiles would make interesting study so wonder if anyone has others that they can put up. I'll dig around and see what makes interesting viewing but I'm a very new cave diver so haven't much to share (50 odd dives on sixths doesn't give much in the way of variety ).




Cave profiles are interesting really - obviously you do what you can to create a better profile - in the example above pinning the line to the floor in the entrance would take you down to 19.5 metres both on the way in and on the way out so you avoid that if you can (here we managed to get a tie at 13 so reasonable but not that great due to the fact that we had to run on the right hand side of the cave).

Some caves lend themselves to nice deco profiles (I understand the Ressel in France does alhtough I haven't dived it) others are a p.i.t.a. There's nothing that special about this one - just thought you might be interested to see one if you haven't before - and it may help explain why average depth is slightly more important to a cave diver than a wreck diver

To explain the above a bit (and why there is a bookmark)

Cave 1 is limited to 6ths. The mainline in carwash is 140 metres from the entrance and it can take a reasonable amount of gas to get the line tied in (I've seen people hit gas limits at start of the mainline).

We agreed to a 30 bar penetration on dive 1 and, leaving the line in place, a return to nine meters in the cavern zone where we would recalculate gas for a second dive which would be 35 bar in from that point.

Not returning to open water to recalculate is, in this instance, simply avoiding yet another bounce on what is quite an unfriendly profile.

So looking at the profile you will see that the cavern floor is at 13 metres (around minute 4) the mainline is at 15.5 (around minute 9) Luke's Hope cenote is at 4 (minute 15) and the dive turns on minute 24 or so where we return to the 9 metre tie off in the cavern area. This takes us 12 or so minutes.

Dive 2 kicks off from minute 37 where I bookmark the time and depth.

We then return to the mainline (although not quite so deep as we are not handling the line) Luke's hope passes by again with it's rise to 4 metres then we drop down until the passage snakes up again on the way to Adrianna's Room which we reach by descending again to 11 meters (at minute 57). Gas limits were not reached on this dive as the passage became too narrow to continue so we had to return at that point - retrieving the line as we went.

One other interesting thing was that I was moaning about my poor gas consumption on this dive until someone pointed out that suit and wing inflation would also be a little heavier than normal

HTH - if you would like to post a profile just open your dive software programme, then press print screen on your keyboard (which copies it) and then paste into MS Paint. You can then cut out just the profile, save and upload to a photo hosting site such as photobox.com or tinypic.com which will give you a url to post here using the image button on the new post form. if there is a more straighforward way of doing it than this let me know

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BigJohn(Offline)

I always blame suit and wing inflation for poor air consumption. When we were in Mexico last month we were talking to a diver that was doing 4 hour dives at Dos Ojos, when they are returning they deco about 40 minutes from the cave opening due to you have to ascend to about 1 meter at this point. This dive isn't very deep. (we never got past 26 feet) but after a couple of hours you do collect some nitrogen. I don't have a bottom timer I can download so it,s interesting to see the dive like that.

rjack(Offline)

I was on a backup computer last week since my Aladin Tec gauge died. But I found it interesting that the Oceanic hockey puck (old Haldane algorithm) that I used (air only) was never bent.

My longest dive was Canyons then Madonna Passage in Temple of Doom. 400 psi in 400 out for Canyons, then about 300 in 300 out for Madonna. Total time was 1:35 something (maybe??). But no bendage on the air 'puter. We recalculated gas UW ~20-25ft and of course I was diving 32%.

Richard

Joe Hesketh(Offline)

There's only 120 metres of line on a Pathfinder reel...

Sorry, couldn't resist. On the sawtooth thing, we were taught to put in short stops (30s - 1min or so) at roughly 80%ATA and up. So in México on a typical 15m max dive, we'd end up pausing at each 9 and 6m rise (unless the slope was gradual, etc.) both on the way in and the way out.

Joe

Lou(Offline)

The comments on YD (at least from me) were that saw tooth profiles were regarded as provocative. The advice that Joe has given seems to suggest that whoever taught him accepts that as a possibility too. What is the general view on here then, are they or are they not?

If they aren't then why bother with holding a good stop - just bounce around between 3 and 9m, that should be about the same on average!

rjack(Offline)

Sure I'd agree that they are "provocative". But in my case (same area/general depths), the sawtooths in question are within allowable air limits (albit primitively derived). Cut off 20% EAD and the thought of adding stops on every intermediate ascent seems a bit paranoid to me.

Clare's ascents look pretty slow to me, in line with Joe's guidelines.

Bob Cooper(Offline)

Here is a typical profile from Trou Madame......

Joe Hesketh(Offline)

Clare’s ascents look fine - you have to remember that’s a 90 minute dive so the depth changes are going to look steeper on the timeline of that graph (edit: even more so with the one Bob's just put up)

The sawtooth thing is certainly recognised as an issue, and the mini-mid-dive-deco was taught to me by both Danny and Fred as a way of introducing conservatism into these profiles. We were quoted actual instances of DCS having occurred before on simple dives on common routes (indeed The Room of Reflections on the upstream line in Taj Mahal is, presumably not for nothing, nicknamed The DCS Dome).

In reality, a lot of the depth changes are gradual and hence any “deco” (if you want to call it that) is done on the fly, and it’s probably less “provocative” (whatever that means) than say multiple CBL’s, etc. There are a few places where the line goes up near vertical walls mid-dive, so we put in short pauses as mentioned above.

On a practical level for me, all the ups and downs are more of an issue for my ears. There’ve been a couple of times where on the way out I just haven’t been able to clear them properly. That’s a real bitch when you HAVE to go down to get out!

Joe

Lou(Offline)

Just clarifying that the "provocative" comment made on YD were not in realtion to the profile posted by Clare, but in esponse to some training exercises done. Clare then posted this profile as a link to that thread, so my comments were not directed at her.

rjack(Offline)

I've been through DCS dome recently. I can't remember the deep portions on either side very well - something around 35 ft (10m) with the top being 4 ft 1.2m. I found the slopes to be pretty gradual and take about a minute to ascend descend. 30ft/min (10m) or close to it.

Its not like your racing and do need pauses to relax your ears. On air I could see this being a bigger issue than on 32% - although MX blending seems kinda coarse I only got something in the 31.0-32.9% range once in 9 sets of doubles used.

Chris didn't talk about mid-dive profile change stops with us. But it would have been a good topic for lecture.