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Seeking input

Discussion in 'New to Scuba Diving' started by Simple simon, Jan 9, 2021.

  1. Simple simon

    Simple simon New Member

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    Hello

    I am a newcomer with roughly 40 dives under my belt. I dive mainly in the tropics south east Asia. And usually do 3-5 dives a day. I am a big person 6 feet 4 and 150kg.

    My problem is my gas consumption is outrageous and it’s severely limiting any dives over about 10m I can’t get near my NDL!

    I am working to shrink my size, and hoping this will cut my consumption rate. But exploring other options for equipment to extend my dive time.

    I am looking at moving to a twin set or side mount with 2 cylinders but have some questions and would appreciate thoughts from those with more experience.

    I generally do between 3-5 dives from a boat and I am concerned about after my first deep dive on a twin set can I then use a STA to dive a single without having to cart 2 wings around and completely rebuild my system? Basically do I need to change wing to a single wing if I use a single tank adapter for the dives after my first deep dive.

    Do I need to use 2 regulators on a twin set or is it ok to use a single regulator initially and forgo the redundancy?

    I like to get into the bottom and explore the reef would a side mount system been stable enough to do this?

    Welcome your thoughts feedback and and any advice.

    cheers

    SS
     
  2. Vanny

    Vanny Well-Known Member

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    Quick honest answer , loose weight, improve cardiovascular fitness and build experience, 40 dives isn’t enough. Increasing kit and complexity won’t reduce your breathing rate , which is what you need to do.
     
  3. splinter

    splinter Active Member

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    What size cylinder do you currently use? I'm guessing an Al80 in SE Asia? Quick and easy fix would be a bigger single like a 15l if that's the case.

    Any solution like moving to twins, ok it would give you more gas available, but increases complexity, the weight you're carrying and the number of things to go wrong and that's the last thing you need to improve your breathing rate.

    Improved fitness will help. Also do a proper weight check. Make sure your breathing properly too. Numerous articles on the web that cover this. Get your buoyancy and trim nailed, get streamlined, swim a little slower. It all gets better the more you dive.
     
  4. jb2cool

    jb2cool Moderator
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    When you say your SAC is high do you actually know what it is? At the shallower depths the NDL is usually much longer than your gas is expected to last and at the deeper depths the NDL will very possibly be shorter than what your gas will last.

    25l/m is a fairly typical SAC for a newish diver, with a bit of experience you can get this down to around 20l/m, this is sort of typical. With more experience and fitness you can get this lower still. I have quite widely varying SAC levels depending on what I'm doing, I've had SAC as low as 9l/m but also as high as 25.5l/m. You basically can't do much about this whilst on the dive, anything you try (like skip breathing) will probably bite you in the arse, all you can do is work on fitness and then on the dive of course monitor your gas but don't worry about cutting the dive short when it's time to go.

    Couch to 5k (jogging) can be a good way to work on fitness as can swimming and cycling.
     
  5. Wibble

    Wibble Fish don't talk
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    Gas consumption is sometimes tied to stress from being in the water.

    Wondering if it would be useful to do a breathing exercise out of the water to measure your 'surface' consumption, to get a baseline. Literally get a cylinder -- doesn't need to be full -- attach the regulators, stick a mask on your face (so you can't breathe through your nose) and sit *quietly* for, say, 10 minutes breathing. Make a note of the gas pressure before and after.

    Then compare this with a dive. Obviously going to 10 metres means you'd consume twice as much gas (add 1 bar/atm for every 10m/33ft, e.g. 20m/66ft = 3).

    Fitness helps, but being stressed really doesn't help.
     
  6. Wibble

    Wibble Fish don't talk
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    As the others said, a twinset will add complexity. All perfectly normal, but needs some training.

    Or does it? At least one person on here's used a twinset as a 24 litre single.
     
  7. Doomanic

    Doomanic Dinosaur Wrangler
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    Hello...

    That was me and it was totally worth it just for all the looks I got... :D

    As said above, lose weight, get fit, dive loads.
     
  8. Simple simon

    Simple simon New Member

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    Thanks for the replies all, very helpful.

    undoubtedly improving my cardiovascular system will help reduce my sac rate and I will continue to work on that and dropping my in body weight.

    in the water I don’t feel like I’m breathing heavily and to be honest barely move other than to flick my toes for propulsion which is sufficient most of the time. I have implemented a 4 second breathing cycle 4 seconds in hold for 2 and 4 seconds out whilst I’m diving and this has helped improve things but not really what I want to be thinking about when diving.

    I might pick up a pony bottle as a cheap temporary solution for my deep dive, until I have more dives under my belt.

    My SAC rate is around the 20 mark but my wife and daughter who are my normal buddies are at about 12 which is my problem as I’m blowing through gas much quicker than them.

    thanks all for the thoughts and sometimes the solution is as you say just hard work.

    cheers

    ss
     
  9. jb2cool

    jb2cool Moderator
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    You’re not blowing through gas, they are particularly light users so they are sipping at their gas.
     
  10. splinter

    splinter Active Member

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    That^ You're actually pretty good on gas. Took me a lot longer than 40 dives to get my SAC down to 20lpm and still have dives where its above that.

    You're wife and kids SAC is remarkable, but that's the unfairness of biology for you. Console yourself with the fact you're less likely to find a jar you cant get the lid off

    Sent from my SM-G950F using Tapatalk
     
    JohnL likes this.
  11. Iain Denham

    Iain Denham Active Member

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    Don't compare your self to the ladies, ladies don't breath underwater #Fact

    Also 40 dives is quite a small number you will need to double it before good comfort levels are felt under water which will help SAC.

    Fitness is good not just for diving but for general life as well so should always be improved anyway but if you are unfit and by the time you are kited up and in the water you may be puffing a bit, so a good idea is to get in the water first so you can have a float and a rest whilst waiting for buddies/team etc. gives you a chance to relax before starting the dive which will help breathing rate.
     
  12. Wibble

    Wibble Fish don't talk
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    A 20 SAC is not as bad as some, but as you've found it is quite constraining especially with ali80s that are relatively low pressure.

    Now for the semi-serious but very expensive answer... A rebreather. This will effectively get rid of your SAC problems, but comes at the cost of lots of training, practice and expense. Probably difficult in Open Circuit focussed places.
     
  13. Dave Whitlow

    Dave Whitlow Super Moderator
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    No. Definitely NOT the answer!!

    Weight loss and fitness will make a difference to the amount of gas but correct weighting and being relaxed make a bigger difference.

    First, try reducing the amount of lead carried. Do you have much air in your BC during the dive? Have you done a proper weight check with an almost empty cylinder, whilst making sure your BC is empty and you breathe out as you try to submerge?

    Pausing every so often to confirm neutral buoyancy will make a difference.
     
    Wibble likes this.
  14. Simple simon

    Simple simon New Member

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    Many thanks all for the replies and consideration.

    to answer some of the questions, I am very relaxed when diving, I used to dive many years ago and am very comfortable in the water. I dived as a kid and am just coming back to the sport now.

    I know I am carrying a lot of lead, but have done a buoyancy check on an empty cylinder at the end of the dive and was about right with my mask being just above the surface, I have tried a dive dropping 10% of my weight but it was bloody hard work. I do have some air in my bcd to get to neutral but not very much it depends on depth usually a couple of touches on the inflator will suffice if I am in 10m.

    on the subject of a rebreather I did have a look at this, but 2 things out me off. A). I don’t want to spend that much cash and B). The statistics around accidents are way higher on rebreathers compared with an traditional open circuit set up. As such I am not comfortable with that option.

    for now it seems that based on the advice I’m getting I need to drop some timber and keep diving. In the interim I may take a pony bottle for my deep dive (<30m to give me a bit more bottom time. Has anyone tried this approach? I am a little concerned it may want to tip me on my side.... I was thinking I could use a trip pouch and move some of my lead to offset this.

    Thanks again for th3 help and sharing of your wisdom.


    Cheers

    ss
     
  15. Wibble

    Wibble Fish don't talk
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    To clarify the rebreather comment: it was semi serious in respect that it, within reason, takes away some of the gas consumption issues. However, this is just masking underlying issues -- not to mention it's a massive step up in terms of skills, is very expensive, can be dangerous, etc.

    ----

    Normally a "pony" bottle is an emergency secondary gas source; typically a 3 litre cylinder strapped to the side of a larger 12 or 15 litre cylinder. This has a separate regulator and is used only for emergency situations where you're out of gas due to some catastrophic failure where it will get you to the surface without relying on others. A pony bottle's not really for your requirements.


    I think you're referring to a "stage cylinder" which is clipped to you on one side (on a chest D-ring and a waist belt D-ring) and is used for either extending bottom time, or if filled with oxygen rich gas (nitrox) can be used as a decompression cylinder for accelerated decompression.

    If using a stage cylinder as a "bottom stage", this can indeed extend your bottom time and could well be a way of staying down longer with your buddies. Stages are typically aluminium and are pretty neutral in the water, but some cylinders, such as an ali80, will get quite bottom-light and float upwards when empty. You can counteract this by moving the lower clip forwards on your belt (i.e. using two D-rings, one on the side, one on the front).

    You'd typically jump in breathing from your "back gas", then switch to the bottom stage regulator, clipping off the back gas regulator, then breathe the bottom stage down to leave some gas in it (a minimum to ascend to the surface in case the back gas has failed -- this will vary according to the size of the stage), then switch from the bottom stage to the back gas for the rest of the dive and your ascent.

    Skills for using a bottom stage are around switching regulators; stowing (clipping off) the unused regulator; tidying the bottom stage regulator up once stowed away; constantly checking and knowing what gas you have now in *two* sources; learning how to calculate your "minimum gas" to ascend to the surface; and the discipline of ensuring that you switch in plenty of time for the depth you're at.


    The mild challenge with a bottom stage is you're still masking the real issue of a high SAC. But it would at least let you enjoy a dive:)


    Another semi-serious suggestion: sidemounting your cylinders. Thus you could take two ali80s and breathe from both. Needs two sets of regs and a different sidemount BCD. You should get training for this though. Benefits: double the gas; redundancy; superb balance and trim underwater. I love sidemount when I need to dive on open circuit, but hate sidemount when using stage cylinders.
     
    #15 Wibble, Jan 11, 2021
    Last edited: Jan 11, 2021
  16. Simple simon

    Simple simon New Member

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    This is really helpful many thanks, I will try and sort out a way to try this in the pool at the weekend!! As it could be a good solution till I can shift some weight and get my SAC down.

    cheers

    SS
     
  17. Simple simon

    Simple simon New Member

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    Just a thought I can see a side mount makes it easier to change cyl. Between dives and gives more flexibility compared with a twin set. I can vary my number of tanks according to my dive profile.

    but given I like digging around reefs looking in holes and exploring the critters would this be less stable in the water than a twin set? Or is it possible to get the 2 cylinders fairly tight so they don’t move in the water? Or am I over thinking this!

    cheers

    SS
     
  18. Wibble

    Wibble Fish don't talk
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    Sidemount is exceptionally stable, way more so than when you've that great weight on your back of a single or twinset. With sidemount you can turn sideways and stay in that position; stable face down, up, sideways, even on your back!

    Sidemount's an enormous faff to sort out though. You can learn by yourself, or from some of those excellent Steve Martin videos (www.sidemounting.com), but it's far far easier to get a *competent* instructor to give you a day or two of the basics; will save a load of time in the long run.

    The kit requirements aren't that much. Two regs (2x first stage - generally the swivelling "turret" ones such as the Mk25 or DST, plus two first stages). The sidemount BCD is the more expensive part -- the X-Deep Stealth Tec is generally highly regarded but in common with all sidemount harnesses needs tweaking "just so". Once tweaked, the kit is really easy to just slap on and go.

    As you're in a Ali80 location, you'd just rent two tins. You would need to work out the bungeeing for "standard" cylinder valves -- this can be done with a "choker" arrangement and use cam-bands for the cylinders (if you own the tins, you'd permanently mount your clips, etc. As you'll rent them, you'll need to have easily removed straps, choker, etc. Nothing too onerous).


    I like sidemount for simple diving. I've not used a single tank in years. On the rare occasion I do a sea dive, or have to use open circuit for solo diving, I'll always choose sidemount. Not least because you've got full redundancy, everything's completely under control. It literally is the nicest diving you can do with open circuit.

    Even my rebreather rig looks a lot like sidemount as I bungee the bailout cylinders back so they're under control and aren't a snag/entanglement risk when in a wreck.



    Dreaming of going diving again... Poxy lockdown.
     
  19. Chimpus

    Chimpus Member

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    Hi Simon,

    Without seeing you its difficult to know, but is your body bulk predominantly muscle or fat? Looking at it from the height & weight figures you give and from a purely physical viewpoint, it would appear that you are obese, bordering on very obese. At 150kg/~24 stone, if it's mostly fat you are carrying, I would urge you to concentrate on losing some weight and boosting your physical fitness before you go looking at any equipment changes. Follow some proper guidance for weight loss eg. https://www.nhs.uk/live-well/healthy-weight/start-the-nhs-weight-loss-plan/ and work on a graduated, planned exercise programme. Both will help.
     
  20. jb2cool

    jb2cool Moderator
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    That does sound a bit harsh but I think it’s an honest question. Height and weight on its own doesn’t really give you too much of an idea or somebody’s build/fitness.
     

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