The Basics of the Rotating Divers’ Bezel

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The Basics of the Rotating Divers’ Bezel

Postby koimaster » July 9th 2018, 3:21pm

In this article in our series on the basics of divers’ watches, we take on what is probably the most distinctive element of a dive watch: the rotating bezel.

Its function is actually quite simple: before a diver’s descent, the 12 o’clock bezel marker is aligned with the minute hand, allowing the elapsed time, up to 60 minutes, to be read on the bezel (which is why quite a few dive watches come with a particularly prominent minute hand). A unidirectional, ratcheting construction ensures that – if the bezel is accidentally moved – the time already spent underwater would be indicated as longer than actually spent, providing the diver with a safety reserve for his now more imminent ascent. The bezel/minute hand combination does not, however, directly measure how much air remains in the air tank, as still can be read quite often in press releases.

A standard scuba dive (in which the diver is equipped with a standard air tank) usually lasts 30 to 50 minutes, mostly depending on the depth reached and the shape the diver is in (basically, how physically demanding the dive is). This explains why the first 15 to 20 minutes on the bezel inlay are often more highlighted – the end of this sector theoretically indicates the point of return (exception: “countdown” bezels that mark the time of ascent). In order to correctly time decompression stops at the end of a dive, central-minutes chronographs such as the Aquastar Benthos or even split-minute chronographs, such as the IWC Aquatimer Chronograph from 2004, offer an interesting complication (should the diver not use a computer). ... tch-bezel/


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Re: The Basics of the Rotating Divers’ Bezel

Postby conjurer » July 9th 2018, 4:03pm

Dang! So that's how it works!!
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Re: The Basics of the Rotating Divers’ Bezel

Postby 3Flushes » July 9th 2018, 4:47pm

conjurer wrote:Dang! So that's how it works!!

Good for timing the sprinkler or a steak, also, too. You can read a map with the lume pip if you charge it up with a flashlight. In case of a plane crash into a body of water, you can open the helium valve and breathe in the helium so your lungs will act as a flotation device and then you can use the bezel to count down how long you have left to live. If you crash on land, you will know what direction you were going when you collapsed and died trying to walk in the direction you were pretty sure civilization was in instead of waiting for rescuers to find you alive which you didn't do because you had a dive watch and read an article on-line about how to use it as a compass. A dive watch with a ceramic bezel can be worn on the fist and used as a self-defense device- especially on a bracelet- without concern over damaging the insert, even if you hit the son-of-a-bitch in the teeth with the tooth busting bezel while the broadly knurled edge rips a little lip on the way by.** Lastly, on nights you can't sleep you can put your head under the covers and shine a flashlight on your watch for ten whole minutes- timed with the bezel- turn the flash light off and fall asleep while you watch the lume go out like when you were a kid.***

**3flushes media suggests you only use dive watches made from 316L SS or better and inca-bloc or better shock protection.
***WARNING!: Using superluminovaed-or other souped up lumed- watches may actually make your insomnia worse.
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Re: The Basics of the Rotating Divers’ Bezel

Postby bedlam » July 9th 2018, 5:25pm

The articles' conceptualisation of watch use in diving is only relevant to recreational diving on a commercial charter boat. Charters normally limit dives to 50 mins for their own practical purposes. There is no actual limit other than how much air you are carrying and the time limits you need to stay within for no-decompression diving. None of that has anything to do with the bezel markings at all.

The markings on the first 15-20 min are a hang-over from a period when diving was done on tables. In recreational diving 5 minute graduations were used back then and the 15-20 minute indexing let you time your last (safety) stop (usually 3mins at 3m) prior to final ascent. The current standard requires the whole bezel be indexed with minutes as well as the bolded 5 minute indicators, which is far more useful as it lets you time deep and safety stops without moving the bezel and losing track of your overall dive time.

At under 10m you could be there all day if you had the air (at 10m I have an air consumption rate of .8bar per minute on a 12 liter tank that holds 232bar, giving me 3 hours of dive time in optimum conditions). The cold and getting bored would be the limiting factors in that scenario.
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