Uses for a 6000m depth rated watch?

ZombieCake

ZombieCake

Well-known member
Omega have released a watch that's apparantly tested and rated for 6000m, or c. 20,000ft in freedom units.  I wonder if there's any real world use (except maybe in the extreme depths of Swildon's Sump 1), or is it just novelty marketing flannel?
Looking at the size and weight of the watch it'll probably drag you down to Davy Jones' locker if you go for a swim wearing it!
Anyway, it does look like some excellent engineering to be able to accomplish such a thing.
I think they also previously strapped a watch to the outside of a submarine and sent it down to the bottom of the Mariana Trench for something to do.

https://www.youtube.com/watch?v=btzwT-zKqFw
 
JoshW

JoshW

Well-known member
I always thought the pressure rating was for being static in water. So a watch moving about at -50m (for instance) is subject to higher pressures than a watch just say at the bottom of the ocean at -50m. Not sure how much extra pressure though, I doubt an extra 1700% (if my understanding above is even true)
 
Cantclimbtom

Cantclimbtom

Well-known member
The use for 6,000m is so the owner can incessantly boast about how "marvellous" the watch is because it can go to 6,000m
 
pwhole

pwhole

Well-known member
Maybe high enough to warrant a corpse-recovery with a submarine. That Omega make parts for?  :-\
 
C

Chocolate fireguard

Active member
JoshW said:
I always thought the pressure rating was for being static in water. So a watch moving about at -50m (for instance) is subject to higher pressures than a watch just say at the bottom of the ocean at -50m. Not sure how much extra pressure though, I doubt an extra 1700% (if my understanding above is even true)
Click to expand...
A rough estimate of the dynamic pressure on a blunt object moving through a fluid is: p = dv^2 where d is the fluid density and v is the speed.
It's one of those handy little expressions that gives an idea of what's going on, but you might want to use something a bit more sophisticated if  you were designing a submarine!
So for water (1000kg/m^3) and a speed of 1m/s this gives 1000N/m^3, or about 0.01 atmospheres.
This will go up to 1 atmosphere at 10m/s.

It also works for a moving fluid hitting a blunt object at right angles eg  in a strong wind.
 
F

Flotsam

Active member
It's obvious. As you sink trapped in a shipwreck at one of the ocean trenches, one can check the time.
 
M

MJenkinson

Member
During a drilling project offshore Japan, me and a mate strapped a 10 quid casio watch to the drilling template after we had flooded it with olive oil. It came back to surface from 3 days at 1000m in fully working condition. It's not 6000m, but it's deep enough and that cost about ?14 quid in total to make. ;)
 
JoshW

JoshW

Well-known member
Chocolate fireguard said:
JoshW said:
I always thought the pressure rating was for being static in water. So a watch moving about at -50m (for instance) is subject to higher pressures than a watch just say at the bottom of the ocean at -50m. Not sure how much extra pressure though, I doubt an extra 1700% (if my understanding above is even true)
Click to expand...
A rough estimate of the dynamic pressure on a blunt object moving through a fluid is: p = dv^2 where d is the fluid density and v is the speed.
It's one of those handy little expressions that gives an idea of what's going on, but you might want to use something a bit more sophisticated if  you were designing a submarine!
So for water (1000kg/m^3) and a speed of 1m/s this gives 1000N/m^3, or about 0.01 atmospheres.
This will go up to 1 atmosphere at 10m/s.

It also works for a moving fluid hitting a blunt object at right angles eg  in a strong wind.
Click to expand...

Oooh maths!

So if it?s proportional to the square of the speed, it?s not unreasonable to suggest that if you were somewhat shallow but moving quickly the pressure undergone by the watch could be quite high?
 
andrewmcleod

andrewmcleod

Well-known member
JoshW said:
Oooh maths!

So if it?s proportional to the square of the speed, it?s not unreasonable to suggest that if you were somewhat shallow but moving quickly the pressure undergone by the watch could be quite high?
Click to expand...

You'd still have to be moving pretty quickly... although it is a good demonstration of why it rapidly becomes very difficult to move quickly through a fluid with like water (and, at higher speeds, even air, although that is a much more compressible fluid so things get more complicated).

Fastest submarine ever was 51.6mph (about 23 m/s), so dynamic pressure of just over 5 atm (or the equivalent of being about 50m down).
Fastest torpedo, however, is going about 100m/s, so dynamic pressures is about 100 atm (or the equivalent of being about 1000 m deep). _However_ the only reason that torpedo can reach that speed is because it _isn't_ going through water - it is a supercavitating torpedo travelling in a gas bubble it generates.

Note that I am ignoring atmospheric pressure (deliberately) as it is the pressure difference between inside and outside a watch that matters (i.e. 1 atm more for every 10m roughly).
 
A

ALEXW

Member
Probably 40 years ago I was going through a scuba diving phase and bought a Seiko Tuna watch. It was rated to 1000m, I was reluctant to use it because it cost so much. It never went deeper than 60m. A few years back I had it serviced and a new battery it cost ?250.00. I sold it soon after.
 
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