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Wot I lerned on my last dive trip

Discussion in 'General Scuba Diving' started by Wibble, Dec 31, 2017.

  1. Wibble

    Wibble Fish don't talk
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    The great thing about diving is learning something new, even if it is pretty obvious to some it's always new to someone else or useful as "revision" to others.

    Specifically, we learn a lot from mistakes or doing things outside of our comfort zone. Do share your stories...
     
  2. nickb

    nickb Active Member

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    Make sure you turn your gas on before entering the water if you wish to see your loved ones ever again, particularly if you're fool enough to dive with a semi-closed rebreather.

    This did NOT happen to me.
     
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  3. Wibble

    Wibble Fish don't talk
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    Don't use steel tins for stages...

    Bleeding obvious really, but was good to try it out. I thought that for a bottom stage (a stage cylinder which would be used for extending the bottom portion of a dive, you switch to back-gas when it's depleted) if an aluminium cylinder was used it would get extremely floaty and therefore tip upwards and be a complete embuggerance.

    It's possible to take a technique from the sidemounters and clip it on a forward belt D-ring, thus dragging it down.

    It's also possible to clip the stage under another (full) stage and keep it under control -- the right answer.

    But no, I thought I'd try a steel stage as this would be slightly heavy when empty, so not float upwards. The maffs means that it's circa neutral when empty - Subaqua.co.uk diving calculator
    So, on paper, seems like a reasonable idea.

    I've a couple of candidate bottom stages to play with, AKA sidemount cylinders. So, wearing my 'standard' twinset, I attached one of those steel cylinders along with two Aluminium 80 stages containing deco gasses -- two left, one right. Then jumped into Vobster with a couple of buddies.

    Feck moi.

    Aside from being grossly overweighted -- wing filled to bursting point and my suit pretty full too -- I managed to stop sinking. But that was only part of the problem; I had to almost go into a 'banana' shape to keep from turning sideways with the weight!

    Stuff that for a game of soldiers. After a minute of that 'trim hell' I decided to ditch the thing and pick it up later. So took it off and put it down whilst dumping a lot of gas from my wing to compensate.

    One of my buddies then decided he'd carry it. Bad move! Same problem, so he ditched it 30 seconds later, but on the APC / tank thing. NP, just mark it with an SMB. Wasn't my best launch of an SMB as the spool left my hand. Good design feature of the shiny Apeks spools is they do slowly descend, so I caught it on the way back down and clipped it to the stage.

    And we continued our bimble and picked up the stage at the end.

    Lessons well and truly learned. Firstly, steel cylinder/stages are great for Sidemount where there's two to balance each other, but are a complete CF when you use one. Secondly, what works in theory doesn't always work in practice! Thirdly, playing aroung / experimenting like this is exactly the point of the relative safety of the quarries.


    ...
    When I went to pay at the end of the day, the guy in the shop said that they'd seen the SMB on the surface and took the boat over to pull on the SMB to see if there was anyone attached and realised it was tied off. Didn't think of that; was just using the SMB for marking the stage to collect it later. Nice to know that they're looking out for us.
     
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  4. timmyg

    timmyg Super Moderator
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    How the purest has changed......

    I’ll admit, that’s something I don’t get, L&R. I went from LL RR to all left, and for 3 prefer all left, or 2 left & one behind & rotate as required.

    That said, SWMBO does 2:1 on the rare occasions she has 3 stages.

    But as with everything diving, each to their own.

    TG

    Sent from my iPhone using timmytalk
     
  5. Tel

    Tel Super Moderator
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    Would have thought the first thing to learn would be to do a standard buoyancy check in the confined area first :p
     
  6. Wibble

    Wibble Fish don't talk
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    Purist? Was something I meant to expand on...

    Using both sides is something which Mark P mentioned when doing the Normoxic Trimix course. It's also popular with (some) rebreather divers diving with two stages.

    Am very happy with two left but the first attempt at putting an ali 80 (third stage) on a leash was bloody awful as the thing dangles between one's legs and is sodding uncomfortable. As ever, it's always easiest to get someone to show you how it's done, but I don't know anyone who dives with a leash. So I've been messing around with putting a stage to the right to see what it's like.

    Being careful when clipping the stage on is important; don't want to trap the longhose. A donate is pretty straightforward; get the reg from the mouth into the donee, then release it from under the cannister which may mean reaching under the stage or even unclipping it. But everyone lives.

    The biggest challenge is where to park the torch when doing a stage switch, particularly when switching from Lean-Left (e.g. 50%) to Rich-Right (e.g. 80%). I found that parking the torch on the left-hand D-ring was easiest as you go through the OxTox protocol for the RH stage.

    Anyway, it's fun to experiment and any new 'knowledge' or experience is good even if it's to realise that it's all wrong. And it's something to do in the winter season to relieve the boredom of a quarry.


    @Tel - how does one do a buoyancy check with three stages and a twinset? As all of them were full of O2+N2, so that's ~15kg of gas in those tins! Hmm. a 40lb wing is 18kg.
     
  7. Tel

    Tel Super Moderator
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    You said yourself that you were overweighted and the wing + drysuit struggled.
    I thought diving 101 was to make sure all was ok before jumping in, so oh dunno maybe the confined area would
    have allowed you to check whatever rig you've decided on this month could cope and your trim was at least passable.
     
  8. Wibble

    Wibble Fish don't talk
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    :)

    I went in in my "normal" rig with normal weighting with the exception of the steel stage which I knew would be 4kg more or thereabouts. Was somewhat surprised at what that means in terms of pumping gas into the wing and keeping a lateral trim. I didn't touch the bottom though, except for putting the steel stage down.

    Kind of was a weight / trim check really, just not in the confined bit. Definitely would be a bad idea to do that on the south end of the NDAC pontoon though!

    It does show (to me anyway) how hard it would be to do an accurate weight check in full technical kit with multiple cylinders, batteries, and preparing for long deco times in cold water, i.e. where you don't want suit squeeze at the 6m stop and *especally* where you're donating gas, etc.

    Actually I'll take that back; just jump in with empty cylinders and stages and keep a 6 metre stop.
     
  9. jb2cool

    jb2cool Moderator
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    I think a 40lb wing is good for 2 stages (Ali), more than that and you need a bigger wing. This is ‘common’ knowledge and is part of the standard rig.

    I didn’t realise how bad it would be though so glad you experienced it rather than me.
     
  10. Wibble

    Wibble Fish don't talk
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    If only I dived with people with "common" knowledge... :)

    Two ali80s on my 40lb Halcyon Evolve work fine. TBH three ali80s is OK too. Definitely not the steel though!

    What's the next 'standard' wing size up that's common on T2 dives?
     
  11. jb2cool

    jb2cool Moderator
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    60lb is the next boy up i think
     
  12. Wibble

    Wibble Fish don't talk
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    Changing too much in one go...

    Throwing down this ramble to get my thoughts together, maybe it'll help others...



    Had a horrible dive on the Alaunia. This is a large Cunard liner sunk by a German mine in 1917 south of Eastbourne laying at 45 degrees from 22 to 30 metres. Vis was pretty cack at ~2m with lots of sediment/gunge in the water, so not much flora and fauna to gawp at in the dark. Lots of twisted metal to keep an eye on, especially overhead. TBH this part of the dive was alright, fair to middling, but have had much better on that wreck.

    A lateish change meant that I donated my twinset to my buddy and dived on my sidemount kit for the first time in the sea and in open water. With all the sidemount fiddling I've been doing over the past few months I'd hoped I was ready.

    My plan was for about 60 mins on the bottom with some deco using 100% at 6 metres with my buddy using slightly different gasses, so a different ascent profile. Both of us are used to diving solo, so we were to dive together but with solo ascents to allow for one of us to bail out when we wanted and to avoid the different gasses constraining our ascents.

    I've found that with the full sidemount configuration with 2 x 12 litre steel tins, two umbilical batteries (one for the suit heater), plus a stage, I've been very overweighted. Sea diving requires, as a rule of thumb, an additional 2 kg over fresh-water diving. Last weekend, diving in the mine, I took off 1 kg but was using smaller 8.5 litre cylinders and one umbilical battery which was about the right weighting. For this dive, I made the decision that the steel 12s plus the additional battery would provide the additional 2kg for the sea water so didn't adjust the weighting.

    I also decided that I'd get the 100 metre Kent Tooling reel and AP crack-bottle SMB out for the first time -- many people saying it's the right tool for the job and, in theory, it should be a lot easier than using my normal Halcyon SMBs with spools which I fill from the drysuit inflation hose.

    Finally, as this was a large, rusty, wreck and the last dive like this I ripped my dryglove and flooded my drysuit as I couldn't get the string out from under the cuff, so I decided to use the thick textured heavy-duty gloves.

    The bottom section of the dive was OK, usual great trim and low profile from the sidemount config. One thing that had made things very difficult was not being able to feel anything through the thick gloves. Was a nightmare doing simple things such as clipping off and unclipping boltsnaps as you can't feel a thing. That bloody tail dump on the sidemount harness' wing was even more difficult to locate.

    What I didn't realise the significance until later, was that I hadn't put any gas in the wing, only in the drysuit.


    We got to about 45 mins and my buddy signalled "up". I responded with "up" and off he went according to the plan. I had had enough of the dive by then, so decided to go up too. As I had the large reel and crack-bottle reel, I ascended to the top of the wreck and reached back for the reel and brought it round. Not being used to it, it was quite fiddly to get the bungees off the bag, then unwrap the velcro straps and work out just how to hold it to launch it. Faffed around with it for a while and cracked the bottle to fill it and closed it off before sending it on its way. I'm sure with some practice this would be OK.

    The fun began as I now realised that I was actually relying on the kilo or so of the reel and crack bottle to keep me down. Bugger. I'd got about 10 mins of deco racked up and the surface was not an option. So went completely vertical to squeeze every drop of gas out of my suit and wing.

    I've been in this position before when diving in Portland harbour where at the end of the second dive meant I was seriously underweighted for the ascent and basically ended up ascending whilst finning downwards. No deco obligation, but not nice.

    This wasn't pleasant at all with my ever-cautious 'captain' on my shoulder screaming you're going to get bent and go pop just like Arnie Schwartzinigger did in Total Recall (version 1). Calm down and get that bloody breathing and buoyancy under control said the other 'captain'. So I did, eventually. Hanging vertically with the reel above, I got things under control and took a couple of minutes to just calm down, with the other captain reminding me that it'll only get worse as the squeeze releases at 6 metres. That captain can be a right bastard.

    The ceiling was only 6 metres, so not that significant, but enough to need some deco. Both computers were happy enough and after another couple of minutes I slowly winched myself up to the gas switch at 6 metres. Again, hung around to make sure I was stable and then switched to the O2. All fine. Switched the Perdix over, so that was happy. Knew that the Suunto wouldn't switch until I'm above 6 metres, so went up for the Suunto to switch and dropped back to 6 metres for the 8 remaining minutes.

    Unusually, the Suunto had cleared much earlier than the Perdix. Once the Perdix cleared I gave it another minute or two as I knew the ascent from 6 to the surface would likely be faster than normal.

    Ascended, all was fine albeit a little faster than I'd have liked. Picked up by the boat, all was good, even some sunshine.

    So what's to learn for next time...
    • Weighting is incredibly important in an open water dive off a boat. Being underweighted really is about the worst thing when you've a deco obligation and the consequences of being underweighted are way, way, way more critical than being overweighted. Not talking grossly overweighted, just that extra 1 or 2 kilos makes a massive difference.
    • If you think you might be light, just add the damn weight and don't justify it.
    • Winter weighting is very different to summer weighting -- that Portland incident happened in winter.
    • From now on I'll add another kilo for all deco dives.
    • Those thick gloves are a bloody nightmare. You can't feel a thing through them and everything's harder as a consequence. Definitely back to the thinner gloves even though they cut easily.
    • Until I get that sidemount dump sorted, it's only for shallow caving with small tins where I can use my suit.
    • That hefty KT reel and crack bottle SMB need practice and are bloody heavy. They'll overweight you when attached to you for the bottom phase of the dive, but will possibly make you light in the ascent phase.
    • Calm down. It's vital to get those stress levels under control as stress breeds more stress and makes everything so much harder and prone to making mistakes.
    • Solo; I'm not sure this contributed much here. It could have meant two people getting into difficulties or just masked the 'learning points' which I won't repeat next time.
    • Sidemount off a boat: not sure. It's easier to carry single tins and lay them down than a twinset. But boats are pretty well set up for twinsets.

    I'm really looking forwards to a simple twinset deco dive. Oh the pleasure of knowing where everything is, knowing how much weight I need.
     
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  13. JohnL

    JohnL Well-Known Member

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    Hey Wibbs - you got back in the boat, unbent and learnt a lot - great dive.:) And gave the rest of us something to think about before we drop in with new kit and/or new conditions.
     
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  14. Dave Whitlow

    Dave Whitlow Well-Known Member

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    So many fails in one dive! You did well to avoid an early season chopper ride!
    Yep, that is never a good idea. You knew changing so much was a poor plan.

    I don't like diving to be exciting so I aim to only make one change before any dive. For me the only change yesterday (first CCR sea dive his year), after a weight check in Vobster a few weeks ago, was adding salt water and 3kg to compensate for the water density change. I like a simple life :)
    A few observations
    • Yes, correct weighting is very important and there is no substitute for doing a proper weight check and then diving the same equipment
    • Adding extra lead (the comfort kilo) just because you've not got a clue is a poor plan
    • For sea water (which is 2.7% more dense that fresh water) the proper calculation is not 'add 2kg for the sea' it is add an additional 2.7% of the total weight of you and your equipment (more likely to be 3kg or 4kg). If in doubt get fully kitted up and get on the scales!
    • Not sure why you have having an issue with the thick gloves. However, if they don't work for you then lose them and have cold hands.
    • Suunto for deco diving? You know that is wrong!
    • Diving with faulty kit (dump valve) is a recipe for problems. You already knew that was an issue!
    • The extra weight of the crack bottle isn't much. I dive CCR, which is much more sensitive to excess weight, and I find it works fine
    • Heavy steel reels have no place in diving as they add excessive weight you don't need. A neutral, or light plastic, reel is better
    • Sidemount on boats is just wrong. What works in the caves should stay in the caves
    Perhaps, for sensible diving (i.e. not in caves), you need to work out a single set of kit and do a weight check and then get on the scales. After that change nothing (apart from adding the correct extra lead)!
     
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  15. Wibble

    Wibble Fish don't talk
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    Great points, especially the weighting.

    That needs to be the diving mantra. I certainly want it as my diving mantra.

    (The Suunto's just a backup. One day I'll blag another Perdix or OSTC. In the meantime the Suunto's my challenge to not bend it)
     
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  16. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    Well, I enjoyed the dive. The vis was better than expected and I got to use my trilobite in anger for the first time.

    Even enjoyed my deco as I spent a bit of time looking up at the surface as the sun had come out - normally it’s a case of managing my position in relation to my buddy and trying to fight the cramp.
     
  17. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    & thanks for letting me use your twins. Made the dive far better than with the air in mine.
     
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  18. Wibble

    Wibble Fish don't talk
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    TBH I think it all turned out for the best in the end. For me it was proof that I've a way to go with the sidemount and that the dump is critical. I think this has lanced the thought that sidemount could be the way to go for deeper dives; not until I've sorted it out it isn't.

    I'll borrow your classic wing to see if that cures the dump problem. Hopefully it will. If not then I've a hack option (basically install a remote dump), or need to look at using a different wing+harness.

    Now I've the two 8.5 litre cylinders for sidemount, maybe I'll reassemble the SM twin 12s into a second twinset so I can have some backup helium fills.

    BTW I've just heard from Sylvia (off the boat) and she said that yesterday's 50m dive on the Noordster was superb; clear, light, and loads of fish. So the vis is better further out and deeper.
     
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  19. Vanny

    Vanny Active Member

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    I'm not a massive fan of solo diving , I've done it and no doubt will do it again but I'd rather take a buddy.

    All the issues you encountered should've been resolved before stepping off the boat. I.e sorted over winter. You choose to separate at the most task loaded section of the dive , smb & ascent/deco. The reel can be secured to the wreck, handled by buddy etc reducing task loading. Your buddy might've been able to help hold your stop (I know you did anyway) , they could've helped with an alternative deco gas you could breath deeper. Your ascent profiles for a 30 Mtr dive can't have been that different. 100% deco gas is effective for off gassing but not very flexible , you've got to be shallow and it'll hammer your cns if you do too much. Even 80% would allow you to hang at 10mtrs which in the circumstances would've been easier.

    I'd advocate getting a set up which you can be completely familiar with and keep it that way. Your constantly changing things , trying alternative set ups. If you'd missed 10 minutes of deco on 100% , that deco obligation would roughly double for 32% and be about 5 times more on 21%. Up a creak without a paddle springs to mind.

    Proper planning , preparation and execution will keep you safe , solo or any other ticket should extol that.

    Glad you both got back ok.
     

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