![]() ![]() So I set the reference marker back four hours (to 8 o’clock), putting the local time on my virtual second time zone function to 4:11. Your watch can work for you so much more on vacation: like this Tutima M2 Pioneer (photo courtesy Sadry Ghacir)Įxample II: to dive in the Maldives for me means flying east (is least). The attentive reader may have already realized that in measuring decompression time the counterclockwise motion of the bezel is counterproductive: accidentally moving the bezel will lengthen the time, which might bring the diver to the surface too early. This scale is for timing decompression stops because most stops for the average sports diver are in the 15-minute range. Looking at the bezels of serious diving watches, we note they have minutes marked between 0-60 and 15. You’re in the shallows, your brain works again, and you count down five minutes. So when you reach three meters, you turn the bezel counterclockwise until the reference marker is at the minute hand and check for five minutes. And it is always a good idea to finish each dive with a safety stop of five minutes at three meters. The dive time from the bottom to the surface is already considered decompression time. One more aspect of using the watch as a no-decompression dive timer: the dive time starts at the surface but finishes in the depths when beginning the ascent. All calculations have been done and checked before the dive. This way, divers only have to keep the marker in mind and no confusing numbers. At which point, the diver must begin ascent. To set up the watch, experienced divers subtract 36 from 60, setting the minute hand to 24, which now counts down 36 dive minutes until it reaches the 60-minute mark. ![]() The no-decompression time is 36 minutes according to the 90s rule, which would call for a twin ten-liter tank of air. Now, let’s say the bottom of the wreck is at 27 meters. Experienced divers know that if something can happen, something will happen. They also calculate the necessary air supply and whether it will be enough for that dive, including a safety margin of one-third more. Setting dive bottom time using the bezel’s reference marker I’ll follow up on really deep diving with a mechanical watch in a future article. That’s 40 minutes of no-decompression time at 25 meters.Īt 30 meters it’s 30 minutes, at 40 meters 10, and unfortunately at 50 meters the formula no longer works, necessitating tables. Here is an example using a maximum depth of 25 meters: doubled makes 50, subtracted from 90 gives you 40. If you double the maximum depth and subtract the result from 90 you get your no-decompression time. But decompression tables were quickly developed to check no-decompression time – the time when a diver should resurface without having to make a decompression stop under water.Įxperienced divers (especially those who weren’t too excited about all these numbers) devised an easy rule to calculate decompression time in the head: the 90s rule. In the early 1950s there was no instrument available to calculate decompression times. The Blancpain Fifty Fathoms Bathyscaphe was launched in 2013.Setting dive time using the bezel’s reference markerīut how does the diver know when to end the dive? The more urban Fifty Fathoms Bathyscaphe takes the name and characteristics of a 1956 model, which referenced Auguste Piccard’s submersible vessel. A complementary range with both women’s and men’s styles was introduced in 2013. The first women’s styles were introduced to the collection in 2008, alongside a rare interpretation with flyback chronograph, complete calendar and moon phases, in 2010. It was followed, in 2011, by the X Fathoms which incorporated the world’s first high-performance mechanical depth gauge. Released in 2009, the 500 Fathoms with helium escape valve further increased water-resistance to 1,000 metres. All have a 45-mm case that is water-resistant to 300-metres – standard since 2003 – and crown guards. Blancpain updated the Fifty Fathoms collection in 2007 with three contemporary models: an automatic with date and five-day power reserve, a flyback chronograph that can be used underwater, and a flying tourbillon with an eight-day power reserve.
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