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Wibble's CCR odyssey

Discussion in 'General Scuba Diving' started by Wibble, Jul 5, 2020.

  1. Wibble

    Wibble Fish don't talk
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    Thanks Dave. I know it's only one dive on the Kyarra, but it really was terrific.

    One of the first things I noticed with CCR is you can breathe as much as you like. With OC you're constantly aware that the bubbles going out will never come back, so you become unconsciously frugal with breathing. Oddly, whilst ferreting around in the wreck, I remembered that you can breathe without affecting your buoyancy and also reduce the amount of percolation (bits falling down from above) as bubbles stir things up. Such a bleeding obvious thing, but it was an unconscious "skill" developed over years of wreck diving using a twinset.

    I don't know if other common rebreathers encourage you to run the unit manually, but I was shown to run the Revo with a setpoint of 1.2 but run it manually at SP1.3. I like that as it means developing the understanding of fine trimming the oxygen or diluent injection as you work hard or change depth. The orifice (leaky valve constantly injecting a small amount of oxygen) helps in this respect. When stopping to gawk at some blenny/lobbie/whatever or keeping a decompression stop, it will mean the oxygen levels will remain pretty static. So treat a controller's oxygen injection as a tap on the shoulder that you've not kept your eye on the PPO2.

    Am sorting out my helium stash from my dealer. Think the two twinsets are about to be put to use as diluent and oxygen banks. Already reassessing how many tins I need. Currently I've 3x Ali 7s and 3x Ali80s. Need to do the maffs for bailout calculations as I progress deeper and work out what the best options are. Would guess that for above **60m you'd keep a strongish helium mix and periodically top off with air as it's slowly depleted with bailout testing and bag inflation, e.g. 20/50.

    Of course for regular diving I'll be cycling scrubbers way more than the sensors say. After all it's only 1.3kg for peace of mind! It is really good to know that the scrubber times are way longer under the sensors than the CE testing rules of thumb.

    **not yet, only thinking now about the future.
     
  2. Dave Whitlow

    Dave Whitlow Super Moderator
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    I gather revo isn't very flood tolerant as you have discovered. That said, flooding the unit is never a good pastime.

    As for other units, I can only speak for the Inspo. It takes effort to fully flood an Inspo and, by going vertical, you can protect the cells and solenoid from flooding, even with a fairly serious flood. I've three floods and bailed out from two of them. The third, and most serious, was getting close to bailout as the WoB was increasing. In this case I avoided bailout as ascent wasn't an option (overhead boat traffic) and I was keeping that to last resort. When we eventually surfaced the exhale (front-mounted) counter-lung was completely full and there was about 6 inches of water in the scrubber. We estimated a couple of litres of water came out. After discarding the lime soup and rinsing the scrubber the unit was prepped and ready for diving the next day.
     
  3. Dave Whitlow

    Dave Whitlow Super Moderator
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    I have 5 bailouts; AL40 32%, AL7 15/55, AL7 65%, AL80 15/55, and AL80 60% (I use an extra O2 3L bottle when using this). Dump the wasteful SMB and get crack bottle or CO2 (best get both).

    A twinset makes for a useful trimix bank (I now bank 15/55 as it's good for most stuff and an air/nitrox top can turn it into something else.

    For oxygen, I suggest you get shot of the twinset and use 2 x 12L for oxygen. It is easier to move around and you are only wanting to fill the low pressure cylinder.
     
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  4. barrygoss

    barrygoss Active Member

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    Yep. Dil is banked 12l twinset of 15/55, bailouts are Ali 80/Ali 40 and Ali 7
    Bailouts are filled with 15/55, 50% and 100%. I’ve got 4 Ali 80’s, 6 Ali 40’s and a Ali 7 of O2. So I have up to 100mins of deco gas.
    Dive planning is now how much deco do I want to do.

    Dives to 50m I’ll stick 5’s on the unit, take an Ali 40 of 50% and 100% and be sound. It’s got a bov plumbed in so the 5l of dil will get me from 50-20m

    Simple gases = simplifying the diving.

    B
     
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  5. Wibble

    Wibble Fish don't talk
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    That’s very useful.

    Obviously have a huge amount of practice and consolidation time ahead with a steady progression to the deeper end of the qualification. The most important thing about rebreather diving is to never forget that the box is after you and it’s happy to bide its time before it strikes! A bit of paranoia whilst diving is a good thing.

    It’s very interesting running various dive plans through MultiDeco to check the bailout requirements; it’s particularly enlightening when you're constrained to a single bailout gas!
     
  6. AndyW

    AndyW Member

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    For what it's worth, even though my MOD1 qualified me to 45m with a light mix, I found the single bailout restriction limiting. If you're wanting to bail onto the gas at any depth to 45m then you're looking at max 29% @ 1.6. You'll burn through that before doing any deco. In that regard it's more limiting than the equivalent OC qual.

    Didn't really find any 45m dives worth doing. As a newbie I was keen not to get into a habit of scrimping on bailout.

    As a result, I did 60 odd hours of stuff which was mostly 30m stuff. No regrets though and once through MOD2 you won't have these issues
     
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  7. Wibble

    Wibble Fish don't talk
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    Was really surprised how constraining a single bailout is for a 45m dive. Have dived an hour at 45m on OC several times which works even if one deco gas fails.

    Checking again, it seems that it’s possible to run a bailout for 1h at 45m as long as there’s no helium in the bailout. Would be a long 90mins deco relying on a single ali80 of 25%

    Must get these early days dives out of the way. Have booked up several 30ish metre dives for now.
     
  8. Vanny

    Vanny Well-Known Member

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    I find the the 40/45 metre stuff tricky on one bailout as the BO gas isn’t optimal, feels bit of a no mans land
     
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  9. Dave Whitlow

    Dave Whitlow Super Moderator
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    35m with a single bailout (32%) is okay but beyond that I agonise over the suitability of the gas in the bailout and much narcosis I want when I bail out.
    Beyond 40m is always two bailouts; trimix and deco gas.
    The choice for 35m-40m stuff depends on the size of the wreck and how much TTS I plan to rack up.
     
  10. barrygoss

    barrygoss Active Member

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    That's where the BOV pays dividends, you bail to the bov accessing your dil and can carry an ali 80 of 50% which will see you good from 20m

    TBH I did Mod1 on mix as I'd been diving the unit for 5 years (self taught) because I couldn't see the reason to use air on a RB. I only have three gasses in the garage 15/55, 50% and 100%, air is for suit bottles and that gets nicked from the free swimming bailout, on the boat.

    B
     
  11. Vanny

    Vanny Well-Known Member

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    I agree , I have access to dil if I need it. 35 + is helium for me and as Dave says my TTS plan will dictate how many BO cylinders I take. But at Wibbles position now the 40/45 mtr stuff can feel restrictive.

    build the hours and experience and move on I guess.
     
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  12. nickb

    nickb Well-Known Member

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    Late to this party, as usual, but that 'report' reads like a very naive person trying to justify a purchase. The scrubber design of the rEvo is the single thing that makes it any good at all in my opinion. However, to call it 'frugal' on lime shows a total lack of understanding of the chemistry behind CO2 metabolism.

    Richard Pyle once said something like "After 10 hours on a rebreather, I thought I knew everything about them. After 100 hours, I realised I knew next to nothing".

    Whilst I'm paraphrasing, Lloyd Bentsen would have said "Wibble, you're no Richard Pyle".
     
  13. Wibble

    Wibble Fish don't talk
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    I know Nick. Over the past 5 years I've done a lot of OC and am very comfortable with it. The more I learn the more I know how little I know. Kind of the standard measure of experience.

    Deeper (60m) mix dives are fine but excruciatingly expensive and somewhat depth sensitive. I guess we all justify why our chosen unit is the best as the entry cost is quite high, particularly for the first one. Despite the Revo being a 'different' unit from most other common rebreathers, I've yet to find a Revo diver who hates or dislikes it. Anyway, I've made my bed, now need to float in it.

    I've spent the afternoon booking a load of dives in the 30m range. Really resisting the deeper ones until I have at least some independent hours on the unit. The other temptation I must resist is strapping on two bailouts; I think I'll be struggling with that as even adding an ali40 of oxygen would give more scope for bailing out.

    Anyway, It's not helped by the bastard weather: tomorrow's dive on the Alunia has just been cancelled. So it's fecking Wrayspuddle on Sunday. Oh the joy :vomit:
     
  14. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    Interesting thread. I know he has a bit of a gob on him and is partial to spouting bollocks now and again, but I’m always surprised at the cheap shots young Wibble has to take at times. It’s a shame as they’re often surrounded by really decent info. Just IMO obviously....
     
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  15. jps

    jps Active Member
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    WhatsApp Image 2020-07-27 at 11.22.18.jpeg

    Oh look here he is.......
     
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  16. Wibble

    Wibble Fish don't talk
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    Spent about 40 mins hovering next to a platform yesterday. Bloody hard in a CCR as you have to be finely tuned with the slightest of changes; with OC it's just control it with your breath. I'm sure that lots of time spent at deco will come in useful for this practice; must keep the bag laying flat on the surface :muted:
     
  17. barrygoss

    barrygoss Active Member

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    Wrong forum for that troll, he’s not a member ;)

    Never had a problem on the switch to CCR. You have an adjustment in lung volume. Bang min lung and be v slightly neg, add to lung so a deep breath just bottoms and it’ll be sound.
    Also don’t worry about hours, I’ve always said it should be not 40 hours, it should be 40+ ascents. You didn’t learn much in 40 mins sat next to a platform.

    B
     
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  18. Dave Whitlow

    Dave Whitlow Super Moderator
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    Yep, buoyancy control on CCR is a learning experience. Let go of the reel and use it as a point of reference and avoid the temptation to use it as a crutch. As Barry says, it's the ascents that count.
     
  19. Doomanic

    Doomanic Dinosaur Wrangler
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    I found it was best to have as many ascents as descents.
     
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  20. Wibble

    Wibble Fish don't talk
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    Been pleased with progress thus far, but so so much to practice and learn. Want to get as much time in the water as possible with plenty more descents and ascents on the way (was amazed how 'busy' these are compared to OC). Continuing to drive the unit manually with the controller backing up to know what’s going on with the PPO2.

    Booked a good dozen trips over the next couple of months, hopefully not too many will be bolxed by weather or kit failures.
     

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