[robi]

I start thinking to this answering to ryuen in the post

https://www.watchuseek.com/showthread.php?p=775809#post775809

Basically there are three main design
- minute markers on the first 15 or 20 minute and 5 minute markers on the rest like my hami khaki navy gmt
- minute markers on all the bezel, but the first 15 minute marked differently like on omega or seiko pepsi
- uniform minute markers on all the bezel like the citizen diver's

Click on images to see a larger version



The best explanation I found is that the 15-20 minute sector is used to time the decompresion intervals, after the bezel is reset during ascending.

I'm not a diver...just a swimmer...

Please give your opinion, to find the best explanation.

:thanks

 

[Watch Watcher]

I must admit, I'd never given it any more thought than just presuming someone did it for aesthetic reasons, and everyone ended up following suit.:think:

Tom

 

[eptaz]

I think you got it with the first 15 minutes being for decompression. The rest, I imagine, is just based on style.

eric

 

[Bassoon]

The first 15 mins are set like that so you know how long to time the pizza.

 

[Caribbean Soul]

subkrawler posted what sounds like, to me, to be an historically reasonable answer, that does not require resetting the bezel for ascending.
https://www.watchuseek.com/showpost.php?p=779051&postcount=22

The 15 minute bezel was derived when Rolex did their testing it the 1950s and divers dove a flat profile based on the USN Dive Tables. Back then, when diving the tables, you planned a dive to a certain depth. If the dive was planned for 80ft then you had a bottom time of roughly 40 minutes. The diver, upon entering the water, would set the arrow on the bezel, 40 minutes ahead of the minute hand. Once the minute hand reached the arrow on the bezel(provided he had enough air) the diver would begin his ascent to the surface. The 15 minute scale helped with timing the ascent and timing whatever safety stop the diver deemed necessary.

Any variance of colors on the bezel, are mostly for aesthetics.

 

[J.Bond]

"The diver, upon entering the water, would set the arrow on the bezel, 40 minutes ahead of the minute hand."

I am a tad confused. Does that mean I would set the arrow to the minute hand or to the 20 minute mark?

~JB

 

[Watcheye]

I start thinking to this answering to ryuen in the post

https://www.watchuseek.com/showthread.php?p=775809#post775809

Basically there are three main design
- minute markers on the first 15 or 20 minute and 5 minute markers on the rest like my hami khaki navy gmt
- minute markers on all the bezel, but the first 15 minute marked differently like on omega or seiko pepsi
- uniform minute markers on all the bezel like the citizen diver's

The best explanation I found is that the 15-20 minute sector is used to time the decompresion intervals, after the bezel is reset during ascending.

I'm not a diver...just a swimmer...

Please give your opinion, to find the best explanation.

:thanks

It comes from the first Dive watches to use this type of Bezel in the 60s. Back then, the usual amount of air in the Dive Tanks was about 15 to 20 mins. The reason the Bezels only turn one way is that if you accidentally move the Bezel, it would show less time left in the Tanks,

No Decompression does not come into it, with regards to the Bezel. That has to do with depth, as to how far down you can go without having to Decompress.

Watcheye.

 

[Joe K.]

Could be...

I have only been diving since 1982, so I my perspective might be limited, but when you plan a dive based on the tables you know beforehand what your decompression stops will be an plan accordingly. The only way I have ever set my watch is to align the arrow on the bezel with the minute hand. That way the elapsed time into the dive is shown. Once I see that I have reached my bottom time I will start ascending and breaking at the decompression stops. The first 15 minutes never really come into play, so I am not sure what they are all about.

subkrawler posted what sounds like, to me, to be an historically reasonable answer, that does not require resetting the bezel for ascending.
https://www.watchuseek.com/showpost.php?p=779051&postcount=22

 

[GatorJ]

Could be...

I have only been diving since 1982, so I my perspective might be limited, but when you plan a dive based on the tables you know beforehand what your decompression stops will be an plan accordingly. The only way I have ever set my watch is to align the arrow on the bezel with the minute hand. That way the elapsed time into the dive is shown. Once I see that I have reached my bottom time I will start ascending and breaking at the decompression stops. The first 15 minutes never really come into play, so I am not sure what they are all about.

The 1 minute gradations would be used to time your decompression stops.

 

[Joe K.]

I guess that would be the case if you move the bezel to time the stops. As a safety precaution, I don't move the bezel until the end of the dive.

The 1 minute gradations would be used to time your decompression stops.

 

[eptaz]

Great info, fellas. I'm learnding!

eric

 

[no_self_control]

it seems to me that the breitling B-1 got this right. the numbering assends anti-clockwise. as such this can be used as a count down timer. most count up.