• Dive One. Joint Hole, UK.

    For the first time in several weeks i got the rebreather underwater without any flooding. It worked OK except that the cycle inner tubes were not completely prevented from kinking by the washing machine waste pipe inside them, so the loop became difficult to breathe - I could feel one of the inner tubes reluctantly straightening out each time i exhaled - but i had to exhale rather hard!! Nonetheless nothing flooded - especially the electronics -, which is a GREAT improvement. My scrubber is now exhausted from various previous experiments. I will change the sodalime and maybe experiment with a radial rather than an axial scrubber.

    i exited after a few minutes of experimenting in the "cavern zone", and went and had a chicken dinner at the nearby Station Inn, which will know me better than any pub in Leeds before long.

  • Dive Two. Wastwater, UK.

    I spent a happy half hour here finding out that it wasn't just a freak last time, the electronics really doesn't leak anymore. And the new radial scrubber works. Of course I want several further test dives before I consider the last 2 sentences really proved.. Meanwhile the most important remaining fault is my own: I haven't fixed the hoses, which have become able to get kinked, restricting the airflow and annoyingly increasing the work of breathing. I say "have become able" because it happened when I was putting extra epoxy into the system to make it more leakproof; which was successful except I used too much epoxy, I didn't leave enough epoxy-free space inside two of my 32mm plastic pipes for the (slightly narrower) hoses to fit in and mate nicely with them. Result: every now and then a hose slips out of its pipe and gets kinked. I shall fix this before I hit the water again.

  • Dive Three. Joint Hole, UK.

    Spent 17 minutes at a max depth of 22 feet or so, daring for the first time to take a rebreather past the light zone. The cave is looking pretty, we haven't had much rain and the water is unusually clear (for England! Florida divers need not feel envious..) Pretty much working OK, another dive like this and I shall consider putting on an extra bailout tank and doing a real cavedive. I am working out what I consider safe as i go along; I reckon 2x12 litre tanks is the minimum amount of bailout gas for a cavedive. In Florida I would probably go for more, i.e. 2x steel 95 tanks, and then I would consider the rig OK for a dive that would normally require a couple of stage bottles. It is a good deal lighter than 2 stage bottles. Nonetheless it's a far cry from just using a single 1.5 litre (tiny!) diluent cylinder, a practise which I consider highly dangerous even without an overhead environment. One hose still slightly kinking - To Be Fixed (Again). Electronics performed well.

  • Dive Four. Wastwater, UK.

    30 minutes, max 53 feet. Main problem remaining was that without my primary light I'm slightly too buoyant (the light's battery canister is a pound or two negative). Next couple of dives will be cavedives; after that I need to use a little extra weight in fresh, open water. Otherwise the rebreather loop can't be given the right mount of air and I go short of a deep breath.

  • Dive 5. Joint Hole, UK. circa 20 minutes, max depth circa 35 feet. The plan for this dive was that I would do the little passageway that is the first sump in the system, then return and pick up a second 12 litre diluent tank and experiment with 2 dil tanks instead of one - I think that 2x12l dil plus 1x 6l O2 tanks is about right for doing a reasonably serious cavedive with the rebreather, giving adequate open circuit bailout from all but the longest (or deepest) sumps.

    However this grand scheme was interrupted by another odd problem: I got half way along the sump when to my surprise I got just a taste - just a couple of droplets - of caustic cocktail with one of my breaths. I grabbed the open circuit dil reg anticipating the inevitable flood of caustic cocktail to follow but it never came. Instead I turned the dive still breathing the rebreather and returned to the entrance shaft. As I went under the lip of rock that sort of guards the entrance shaft - nothing like a real restriction, just a slight narrowing of a tall passageway - suddenly I felt something bumping on the roof, and a few seconds later I understood what had happened. My scrubber canister had come loose from its rather crude mounting and, being lighter than water by some margin, was floating up towards the ceiling in an upside down position. In the process of breaking loose into that unusual configuration, a few drops of liquid were no doubt dislodged from the scrubber, and they made their way into the inhale side of the loop - with the canister inverted the inhale side outlet would be "down at the bottom" as well as "along the line of the air flow". That was the cause of the problem, which must now be fixed by improving on the "rather crude mounting". Then we'll repeat the dive plan and hopefully get onto experimenting with that extra dil tank.

  • Dive 6 Joint Hole UK. Inspection of the scrubber revealed about half a cup of accumulated water in the bottom of it so it got cleaned out and I decided to make a better water trap out of the downstream counterlung. Up until now we had (after maybe 100 minutes diving) a total of about 2 cups water removed from the downstream counterlung, half a cup from the scrubber; ergo, about a quarter of water leaking past the mouthpiece was making it into the scrubber. Went back to Joint hole and had a nice little dive, circa 27 minutes max 30 feet.

  • Dive 7 Hurtle Pot UK. 30 minutes max 57 feet. Went upstream to the Eastwall outlet junction. Scrubber doing better now properly secured.

  • Dive 8 Wastwater UK. 45 minutes max 71 feet. The new water trap is an improvement; after this dive and dive 9 I could only find a few drops of water in the bottom of the scrubber compartment, and the chemical itself felt dry to the touch. Also, I discovered why so much water was leaking through the mouthpiece; simply, the rubber mouthpiece has developed a hole in an unauthorised place. So we'll deal with that before next time too and then we should be reasonably leakproof (NB no water has ever ben found in the upstream counterlung during these 9 dives, some evidence that "most" of the rig is reasonably waterproof). Diving a little deeper with the rebreather I stopped around 70 feet because it was getting cold (below about 80 feet Wastwater is circa 4 degrees C or 39F year round), and because of a previous dive when I wore an inadequate wetsuit here to 150 feet and found myself hyperventilating uncontrollably for a few seconds on ascent back to 100 feet - on open circuit!!!. Blooming freezing down there. I guess CO2 got released from my cold tissues in just enough excess to cause the hyperventilation. Having this dive an alternative reason to hyperventilate in my rebreather with its fairly primitive scrubber, I decided to postpone the adventure of going deeper in the cold water, even though I now have a warm, non-leaky drysuit.

  • Dive 9. Joint Hole. This dive was a bit of an anticlimax because recent rain has reduced the visibility to "up to 2 feet". So, I stayed just long enough to check that I and my rebreather seemed fully functional. Circa 20 minutes down to circa 20 feet.

  • Dive 10 of 9!! I then went back to Wastwater and gently increased the max depth the rebreather has handled, going to 84 feet for 45 minutes. Once I get into serious deco depths it will be time to arrange direct calibration at the surface with O2 pressures above 1 bar.

    The dive itself was an illustration of thermoclines: this was the afternoon of close to a record hot day for the UK, so the water at the surface was tepid bath temperature. But it cooled as you went down, till below about 80 feet it was 4C as usual. (Water achieves its lowest density at 4C/39F so a deep lake like Wastwater is always 4C below a certain depth. Above, it's generally warmer but might occasionally be frozen. But below 80 feet or so, it's 4C the year round). Rebreather did well.