Vulcain Vintage Nautical Diver - Dive Table Explained.
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  1. #1
    Member vokotin's Avatar
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    Cool Vulcain Vintage Nautical Diver - Dive Table Explained.

    Weeks ago I had the pleasure to handle in metal, thanks to my Italian buddy Luigi a brother for me.. a beautiful vintage diver from the 70s.
    A purpose built instrument a tool watch belonging to a different era where real divers relied on nothing but a depth gauge and a mechanical dive watch to explore the bottom of the sea.

    “When first launched in 1961, the Vulcain Cricket Nautical was truly avant-garde in all respects. For the first time ever, a wristwatch was capable of descending to 300 meters and audibly warning its wearer that it was time to the surface, while precisely indicating the various decompression stops."

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    The compressed air a diver breathes contains the same amount of inert nitrogen as the air we breathe at the surface. But the deeper you dive and the longer you stay down, the more of this nitrogen is absorbed by the body. When a diver ascends, this nitrogen expands and, if all goes well, is harmlessly released through the bloodstream. But stay too deep for too long, or ascend too quickly, and the nitrogen can rupture tissue, damage blood vessels and nerves, and wreak havoc on the body.

    With no dive computers, at the time recreational divers were forced to abide the dive tables developed by the US Navy that dictate the decompression limit for each depth.
    As long as you don't exceed the deco limits time, you can safely resurface without getting the bends.

    Most often, divers exceed these no-decompression limits deliberately, in order to explore a deep wreck for example, so to safely surface from these dives, they must linger at set depths on the way up and “decompress.”
    Decompression diving uses its own set of tables which outline at what depths and for how long a diver must decompress on his way up. These tables would be cumbersome and inconvenient for a diver to carry while submerged, so Vulcain, with the help of Dr. Keller, put these tables on the dial of the Nautical Cricket.

    Without further ado, it's time to see how to read the dive table on the Vintage Nautical Cricket Diver from the 70s which I tried on my wrist, feeling so darn stupid by the way since I'm not a diver and I never bothered to learn something about dive tables till that day.

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    The first thing to keep in mind is, it's just an analog watch made to tell the time, so forget for a moment all those colored circles, forget those strange numbers printed on them, forget the alarm and the seconds hands.
    So what do we have here? hour and minute hands, minute markers and minutes scale printed inside the black circle of the inner rotating bezel.

    So far nothing difficult, heck, we learned how to read the right time when we were just puppies.

    Let's move forward to the white squares track now.

    We can see two columns of numbers printed in black, 40-135, 35-115, 30-100, 25-85.
    At the top of each column we can see also two letters, M\F printed in white.
    What do they stand for? M stands for meters, F stands for feet. Those columns of numbers represent the depth scale, so 40mt = 135ft - 35mt = 115ft and so on...

    Now, let's say we are planning a dive to enjoy the beautiful coral reef at 25mt depth = 85ft below the surface, with our Vulcain diver strapped over the wetsuit.
    All we need to know is how many minutes we can stay at that depth without the need to make a deco-stop.
    Just follow the 25/85 white squares curve track till the number 0.. the square is orange now, why?
    0 is our No-Decompression-Limit, so we can enjoy the dive at 85 ft depth without the need to make a deco stop for.... follow the minute markers scale now and see where the 0 square is located.. the NDL is 34minutes.

    But what does happen if we stay at that depth for 35 minutes, just a minute more?
    We are forced to round up our math since we can't ascend quickly and safely anymore due to the higher quantity of nitrogen accumulated in our body that would be lethal for us, so let's follow the curve again till the next orange square with the number 5.
    Number 5 is the time of minutes we need to stop usually at 15ft depth before resurface safely.
    Actually, what the table is telling us is this, 5min is the first deco stop necessary if your dive time is 40minutes at 85ft depth.
    But if we can stay down 50 minutes for example, according to the table our the decompression stop will increase to 20 minutes. (Number actually covered by the hour hand but it's there.)

    Alright, time for a quick recap.

    85ft depth = NDL 34minutes
    40 minutes at 85ft depth = 5min. stop at 15ft
    50 minutes at 85ft depth = 20min. stop at 15 ft


    Different depth zone, same logic and same way to read the table.


    100ft depth = NDL 19 minutes
    25 minutes at 100ft depth = 5min. stop at 15ft
    35 minutes at 100ft depth = 15min. stop at 15ft
    45 minutes at 100ft depth = 30min. stop at 15ft
    55 minutes at 100ft depth = 45min. stop at 15ft


    115ft depth = NDL 13 minutes
    20 minutes at 115ft depth = 5min. stop at 15ft
    30 minutes at 115ft depth = 25min stop at 15ft
    40 minutes at 115ft depth = 40 minutes stop at 15ft
    50 minutes at 115ft depth = 60 minutes stop at 15ft


    135ft depth = NDL 10 minutes
    10 minutes at 135ft depth = 10min. stop at 15ft
    25 minutes at 135ft depth = 30mins stop at 15ft
    35 minutes at 135ft depth = 45 min. stop at 15 ft
    45 minutes at 135 ft depth = 60min. stop at 15 feet
    55 minutes at 135ft depth = 80 min. stop at 15 feet


    Hope I made no mistakes , but that is all gentlemen, finally we have been able to understand and to read a very cool yet useful feature at the time.

    Sorry for the headache, and many thanks for looking!

  2. #2
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Hey Vokotin, you may be able to answer this question for me…I posted this over a month ago on the Panerai Forum but didn't really get a decent answer…thought you may have some insight…
    Use of the Radomir and the Luminor for timing missions.

    Does anyone know the specific technique/proceedure used by the Italian Navy combat swimmers when using the historic Panerai's for timing underwater operations? Modern diver watches have a bezel which allows divers to time bottom time, decompression time etc, but the historic Panerai's didn't/don't have the bezel.
    I suppose that when pilots of the X-Mas 'Pigs' were underwater it was at a depth that didn't require any decompression (10-15 feet) the breathing apparatus used were the re-breather type common in the 30's and 40's, so it seems that the watch could be used to time total mission time by zeroing the watch (setting to 12 o'clock) just before submerging to begin the mission.
    Factors like sunrise, time till warhead detonation etc would be known so the mission could be laid out by being at a particular target point in the mission at a designated hour, ingress, egress planting the warhead etc... the actual 'time' accouding to a 24 hour clock was not actually important.
    I'm sure there is an answer, I've just puzzled over it from time to time, and I would love to know the answer.

    longstride.

  3. #3
    Member vokotin's Avatar
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    The pig so nicknamed to its poor maneuverability was an assault vehicle launched form a submarine and piloted by two men.
    Those men wore closed circuit re-breathers filled with pure oxygen as opposed to compress air.
    Even though the Pig could reach 30 meters depth they usually didn't exceed 15 meters.
    The re-breather had two purpose, first to avoid creating air bubbles which could alert the presence of divers.
    Second, using closed circuit re-breathers the deco stop was unnecessary, regardless the depth reached.

    Actually, the frogmen were brave men, using such re-breathers filled with pure oxygen only, and no mixture, was a very hazardous and dangerous job.

    My guess is, they used the Radiomir just to keep track and to sync the time spent during the night operations.


    Quote Originally Posted by longstride View Post
    Hey Vokotin, you may be able to answer this question for me…I posted this over a month ago on the Panerai Forum but didn't really get a decent answer…thought you may have some insight…
    Use of the Radomir and the Luminor for timing missions.

    Does anyone know the specific technique/proceedure used by the Italian Navy combat swimmers when using the historic Panerai's for timing underwater operations? Modern diver watches have a bezel which allows divers to time bottom time, decompression time etc, but the historic Panerai's didn't/don't have the bezel.
    I suppose that when pilots of the X-Mas 'Pigs' were underwater it was at a depth that didn't require any decompression (10-15 feet) the breathing apparatus used were the re-breather type common in the 30's and 40's, so it seems that the watch could be used to time total mission time by zeroing the watch (setting to 12 o'clock) just before submerging to begin the mission.
    Factors like sunrise, time till warhead detonation etc would be known so the mission could be laid out by being at a particular target point in the mission at a designated hour, ingress, egress planting the warhead etc... the actual 'time' accouding to a 24 hour clock was not actually important.
    I'm sure there is an answer, I've just puzzled over it from time to time, and I would love to know the answer.

    longstride.

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  5. #4
    Member mellonb1's Avatar
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Love the looks of the Vulcain. Fun read and informative as I never completely understood the dial. Thanks for posting...
    vokotin likes this.

  6. #5
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Quote Originally Posted by vokotin View Post
    The pig so nicknamed to its poor maneuverability was an assault vehicle launched form a submarine and piloted by two men.
    Those men wore closed circuit re-breathers filled with pure oxygen as opposed to compress air.
    Even though the Pig could reach 30 meters depth they usually didn't exceed 15 meters.
    The re-breather had two purpose, first to avoid creating air bubbles which could alert the presence of divers.
    Second, using closed circuit re-breathers the deco stop was unnecessary, regardless the depth reached.

    Actually, the frogmen were brave men, using such re-breathers filled with pure oxygen only, and no mixture, was a very hazardous and dangerous job.

    My guess is, they used the Radiomir just to keep track and to sync the time spent during the night operations.
    If they were breathing 100% O2, even at depths of 15m, the partial pressures would have been dangerously high. Even using a ppO2 of 1.6, the current maximum operating depth (MOD) is 19ft**!

    **from memory.

  7. #6
    Member vokotin's Avatar
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Quote Originally Posted by Noodlefish View Post
    If they were breathing 100% O2, even at depths of 15m, the partial pressures would have been dangerously high. Even using a ppO2 of 1.6, the current maximum operating depth (MOD) is 19ft**!

    **from memory.
    You right, but there were no limits at the time and that is why I said, "brave men.." the chance using such re-breathers beyond 19ft depth to get an O2 intoxication, was very very high.

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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    think so,the chance using such re-breathers beyond 19ft depth to get an O2 intoxication, was very very high.thank you

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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Quote Originally Posted by vokotin View Post
    The pig so nicknamed to its poor maneuverability was an assault vehicle launched form a submarine and piloted by two men.
    Those men wore closed circuit re-breathers filled with pure oxygen as opposed to compress air.
    Even though the Pig could reach 30 meters depth they usually didn't exceed 15 meters.
    The re-breather had two purpose, first to avoid creating air bubbles which could alert the presence of divers.
    Second, using closed circuit re-breathers the deco stop was unnecessary, regardless the depth reached.

    Actually, the frogmen were brave men, using such re-breathers filled with pure oxygen only, and no mixture, was a very hazardous and dangerous job.

    My guess is, they used the Radiomir just to keep track and to sync the time spent during the night operations.
    The closed circuit system used by the Incursori, made by Pirelli could be used with pure oxygen or nitrox depending on the mission, the ARO had a twin gas tank assembly allowing the use of both breathing mediums in the same mission.

    The SLC (Maiale) carried its own compressed air supply for balance adjustment underwater and surfacing as needed. the SLC air supply was available to the Incursori as a back up.


    Paul Bert, a French physiologist, first described oxygen toxicity in 1878, the waterdepth limitation of pure oxygen breathing was well known in Italy in the late 1930s.


    Military divers using O² closed circuit systems usually stick to shallow depth, as close to the surface as the sea conditions allow, they can dive deeper than the safety depth of 7M for very short duration, but beside being dangerous, it's a tricky manoeuvre,they need to compensate the increase of pressure by adding oxygen into the rebreather, and when they return to their swimming depth they have to bleed off the excess oxygen pressure discreetly.

    Trainee military divers are screened for oxygen tolerance underwater by breathing pure oxygen in a decompression chamber at 18M.
    Last edited by kelt; November 15th, 2013 at 16:19.

  10. #9
    Member vokotin's Avatar
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Quote Originally Posted by kelt06 View Post
    Paul Bert, a French physiologist, first described oxygen toxicity in 1878, the waterdepth limitation of pure oxygen breathing was well known in Italy in the late 1930s.
    Of course, the toxicity of oxygen and waterdepth limitations were very well known in Italy.
    "No limits.." I meant they could exceed the 6 meter depth limit, but the Italian Frogmen were very well trained military divers.
    Regardless the depth, their knowledge and experience of use, the risk was very high, I read about several casualties occurred at the time.
    Last edited by vokotin; November 16th, 2013 at 15:11.

  11. #10
    Member vokotin's Avatar
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    Re: Vulcain Vintage Nautical Diver - Dive Table Explained.

    Another very important thing to mention that I forgot to say is, the ARO used by the Italian Frogmen at the time had very spartan made components like the counterlung and CO2 absorbent canister, and was less safe compared to a modern one, hence the higher risk added.

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