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  1. #1
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    Question about drysuits and air

    Hi, this is my first post and hoping someone can answer this as I don't get how it works


    When you put a blast of air into the you dry-suit to alleviate the "squeeze", how does that work exactly ? If air (while underwater) collects into a bubble and moves around, then how can it also spread out about the suit to help the squeeze ?

    Think of it like this; you put some air in the suit, it forms a bubble and gets trapped in the feet (or foot). In this case most of the air is in the feet, so you would suffer the squeeze everywhere else ?

  2. #2
    Established TDF Member witchieblackcat's Avatar
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    Quote Originally Posted by James 1976 View Post
    Hi, this is my first post and hoping someone can answer this as I don't get how it works


    When you put a blast of air into the you dry-suit to alleviate the "squeeze", how does that work exactly ? If air (while underwater) collects into a bubble and moves around, then how can it also spread out about the suit to help the squeeze ?

    Think of it like this; you put some air in the suit, it forms a bubble and gets trapped in the feet (or foot). In this case most of the air is in the feet, so you would suffer the squeeze everywhere else ?
    Air doesn't collect into a bubble and move into your feet.
    The air you add into the drysuit raises the pressure of the air already there hence alleviating squeeze.

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    TDF Member Titanic's Avatar
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    You'll find when adding air to a suit to alleviate squeeze or even if using the suit for buoyancy the air will find its way to where it needs to be, it just isn't a problem even in relatively tight dry suits.
    Air can and will move around a suit, I know people who go a bit head down at the start of a dive to move some air to their boots to add a bit of buoyancy in that area to counteract diving with heavy tech fins.

    You can have an issue whereby air migrates to the boots if you are in a head down position such that you end up with your feet floating above you, dry suit training covers how to deal with this. It's not a big deal.

    Air can get stuck such that when you are ascending it doesn't vent as required making you overly buoyant. This is often associated with thicker undersuits trapping air or even blocking the dump valve. For me this is something you get used to over time when you are diving your own dry suit, things can be tweaked if you have problems (e.g. putting tape over the undersuit by the valve to improve air flow), but it is down to personal experience. Different dry suits / different fits will have varying amounts of air spaces around your body. I dive an O-Three neoprene which I like partly because they are quite a close fit and right from the start I found the buoyancy nearer what I was used to in a wet suit, unlike my previous dry suit which seemed to have a lot of air kicking around in it despite being made to measure.
    You are entitled to your own opinion, you are not entitled to your own facts.

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    Quote Originally Posted by witchieblackcat View Post
    Air doesn't collect into a bubble and move into your feet.
    The air you add into the drysuit raises the pressure of the air already there hence alleviating squeeze.
    Great thanks for response, yep that makes a bit more sense now.

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    Great thanks for the response, that's good info.

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    Quote Originally Posted by Titanic View Post
    Air can and will move around a suit, I know people who go a bit head down at the start of a dive to move some air to their boots to add a bit of buoyancy in that area to counteract diving with heavy tech fins.
    There's a whole discussion in itself right there!!!

  7. #7
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    You’ll get used to the feeling and how to move it round to eliminate the squeeze where you need to. The air does move around a bit but it’s not like you have one big bubble.

  8. #8
    Old but keen Mark Chase's Avatar
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    Quote Originally Posted by James 1976 View Post
    Hi, this is my first post and hoping someone can answer this as I don't get how it works


    When you put a blast of air into the you dry-suit to alleviate the "squeeze", how does that work exactly ? If air (while underwater) collects into a bubble and moves around, then how can it also spread out about the suit to help the squeeze ?

    Think of it like this; you put some air in the suit, it forms a bubble and gets trapped in the feet (or foot). In this case most of the air is in the feet, so you would suffer the squeeze everywhere else ?
    Air pressure will need to be even throughout the suit so injecting air will spead it around no problem

    Be warned the more air you have in your suit the more "management" this air needs.


    In my early days of dry suit diving I used to use suit for buoyancy and with a single tank rig that's usualy fine (unless your massively overweighted) but on a twinset rig I found occasional issues with air trapped in boots which I was struggling to get into a position I could dump it from. So I tended to use the absolute minimum of air required to remove the squeeze an then use the much more controllable BCD/Wing to manage buoyancy.


    I also used gaiters on my lower legs when diving in shallow trim critical environments like caves to prevent air getting to my boots.


    Every one goes on about perfect trim and horizontal ascents but sorry screw all that, safety comes first.

    SO in early dry suit days Id go vertical straight legs on a pause on ascent and vent everything I could out of the suit. On say a 30m dive id do this on the bottom and probably at 21 and 15m Once comfortable on the 6m stop id add a bit to the suit for comfort whilst dumping from the wing.


    I don't know what the percentage spit on this point is but id say 50% ish suggest minimum air in the suit and I am firmly in that camp


    IMHO Reguardless if you change your mind later and go for suit for buoyancy, start off super cautious with minimum air and build up to it.

  9. #9
    Prior Member Tim Digger's Avatar
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    If you are vertical in the water then the suit is under different pressure from the water column, 2 metres =0.2 bar. Air is squeezed out of dependent parts of the suit by the slightly higher water pressure. When horizontal there is little difference in pressure on front or back of suit and SLIGHT excesses of air can be moved around the inside of the suit in the undergarments to alter the trim of the diver so no effort should be required to hold a horizontal position. The more air you have in the suit the more difficult does this balancing act become!
    Evolution is great at solving problems. It's the methods that concern me.
    Tim Digger

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    Quote Originally Posted by Titanic View Post
    Air can and will move around a suit, I know people who go a bit head down at the start of a dive to move some air to their boots to add a bit of buoyancy in that area to counteract diving with heavy tech fins.
    Maybe thats what I need to do, I have heavy fins and rock boots.


 
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