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Max depth for CESA?

Discussion in 'Advanced Scuba Discussions' started by Bigeclipse, Aug 10, 2017.

  1. Dizzi Lizzi

    Dizzi Lizzi Manta Ray

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    :shocked: Personally, I would only want to practice it from shallow depths, say 30 feet like in training. With my working reg in hand. Hopefully muscle memory and the knowledge that it works and I've done it before (more than once) will help me if I am ever in a situation where I need to do this.

    edit: just saw mbd's post. yea, like he said
     
    mdb likes this.
  2. mdb

    mdb ScubaBoard Sponsor ScubaBoard Sponsor

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    Practicing from any depth, whatever you feel comfortable with, will, obviously, help if the skill is ever really needed.

    In my first couple of hundred dives I practiced free ascents at the end of every dive. Most often 40-60 FSW.

    When the time came to do it for real, it seemed a normal response.
     
  3. WantSomeScuba?

    WantSomeScuba? Dive Shop

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    No, I agree with you 100%. I was more suggesting to what degree should one practice this particular skill? Do you practice emergency ascents from 120 ft?
     
  4. mdb

    mdb ScubaBoard Sponsor ScubaBoard Sponsor

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    No, I have never practiced a free ascent deeper than 100 FSW.

    I routinely have practiced from 40-100 FSW, mostly in the 40-60 feet range.
     
  5. Akimbo

    Akimbo Lift to Freedom Volunteer Staff Member ScubaBoard Supporter

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    You might find this thread interesting: Max Depth for CESA


    To expand a little, Captain Bond made that buoyant ascent with Chief Cyril Tuckfield in 1959. I'm not sure how applicable it is for Scuba divers though. They were aboard the submarine USS Archerfish, pressurized the escape trunk to depth in under a minute, and on the surface 52 seconds later. A 60'/minute ascent would be over 5 minutes.

    Chief Tuckfield was running the diving locker at Submarine Development One in San Diego when I was there in the early 1970s. He not only worked with Captian Bond on that dive but also during Sealab 1-3. I lived on base so spent hours talking to him during my free time. The guy was a legend but was as modest as a new recruit. I practically had to drag sea stories out of him... I wish I took notes.

    I'm not sure if they still make submarine sailors do emergency buoyant ascents from 100' in a tower anymore or not. Maybe @Wookie knows? I think he was on the boats.


    I do on a regular basis:



    I'm sure it depends a lot on the individual and how much you train. Speaking for myself, it is a reflex, but this is what I remember from the first lecture in my Scuba class:

    Memorable for sure.
     
    Last edited: Aug 11, 2017
    Bierstadt, northernone and mdb like this.
  6. Dizzi Lizzi

    Dizzi Lizzi Manta Ray

    # of Dives: 50 - 99
    Location: California
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    What's the difference between free ascent and CESA?
     
  7. northernone

    northernone Great White Rest in Peace

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    In my understanding they are the same behaviour with different terminology. I hear them used interchangeably.

    Edit: Free ascent I hear from those with military backgrounds and a CESA is a recreational scuba term. Upon reflection I suspect there are differences as I've never been trained for a free ascent.
     
    Dizzi Lizzi likes this.
  8. dmaziuk

    dmaziuk Orca

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    And not only American ones. There are obvious problems with doing it underwater, though.
     
  9. pepperbelly

    pepperbelly Solo Diver

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    I was certified in the mid '70s as was diving with dad since about '68 or '69. We called it a free ascent then.
    CESA is more recent, like BCDs, octos, aluminum tanks, etc.
     
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  10. Akimbo

    Akimbo Lift to Freedom Volunteer Staff Member ScubaBoard Supporter

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    Free ascents are without a regulator in your mouth and sometimes with Scuba gear jettisoned. CESA (Controlled Emergency Swimming Ascent) keeps the regulator in your mouth to take advantage of any residual gas in your cylinders that becomes available as ambient pressure reduces. Submarine escape uses very buoyant ascents and often a breathing device, starting in the US with the Momsen Lung and later the Steinke Hood. There may be something newer now.

    I prefer doing free ascents because I feel that the regulator makes it less natural to keep my airway open. After a lot of practice I found that I can position my neck and jaw so that it is very hard to close my airway. One of the divers I worked with taught buoyant ascents at the Submarine Escape Tower in New London and helped me refine my technique. Rather than overtly blowing air out I barely exhale and purse my lips to keep the water out and make sure that there is almost no backpressure.

    Obviously, this can be fatal if you screw up so test carefully and progress slowly. However mastering it will increase your survivability no matter how much your gear fails. I didn’t need it since I had been doing them for about 9 years by then but he suggested sitting in a pool holding your breath and assume your "position"... looking up, jaw thrust forward, pursed lips. Air will escape when you find your sweet spot and gently pushing on your diaphragm will push air out faster.

    You can force air out faster than necessary, which isn’t a big problem in itself since the expanding air will catch up... except that you may naturally try to close your airway and embolise yourself. That is true on a free ascent or CESA.

    Start shallow and overtly exhale until you get the feel of it and SLOWLY learn to exhale less aggressively until keeping the airway open is natural and reflexive. Keep your regulator in hand in case you over-exhale and get uncomfortable. You will also learn the feel of moderate lung inflation and allowing gas to escape through your lips faster as you get shallower. It sounds a lot harder than it really is. I did one from 180' once because I was doing a lot of diving at that depth and wanted to make sure my ultimate back-up system worked.

    Edit: I forgot to mention an important factor:
    Remember that you won't pass out from low Oxygen because of the elevated ppO2... like 2x at 33', 3x at 66', etc. There is way more Oxygen in your body than you will need to reach sunshine even if you have only been on the bottom for a few minutes. You will also be expelling CO2 so can comfortably do a free ascent or CESA much longer than you can hold your breath at the same activity level.
     
    Last edited: Aug 12, 2017

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