Is 50 meters water resistance too risky?

Archer · Apr 30, 2021

C Concretepuppy
The crazy thing is that your arms don't move much at all while diving or snorkelling, they're best folded across your chest or down at your side, which i must admit makes the dynamic arm movement increasing water molecule much less of a possibility even if it's more through the user's performance than physics, the physics behind the theory holds water for me but certainly not in the time frame that the manufacturer states the seals or gaskets to be checked, would be interesting from a watch likers point of view to see the condition of the seals and pressure test results of two identical dive watches after a year of diving every day at the same depths, one in the Caribbean and one in Norway, a project

You state that you don't have the mathematical wherewithal to do the calculations, but then state that you believe the physics holds up?

What are you basing that one if it's not mathematical calculations?

hronists · Apr 30, 2021

C Concretepuppy
Yes it's small stuff, people need special equipment to see it, but luckily there's that youtube thing, they have videos that show you the small stuff and how it works without needing the equipment

Also there's a great word called "the", it's free to use and really useful

i studied physics and math in school and university. Granted it was quite a while ago but thanks to that I don’t need to look YouTube vids to visualise three water molecules swimming past seal.

oh and by the way English is my third language, so please excuse my mistakes.

Dan S · Apr 30, 2021

Archer
You state that you don't have the mathematical wherewithal to do the calculations, but then state that you believe the physics holds up?

What are you basing that one if it's not mathematical calculations?

I'm happy to show the calculations if anyone is interested. But the bottom line is that even very rapid motion wouldn't result in dynamic pressure that is equivalent to more than a few meters of additional hydrostatic pressure. For example, a velocity of 10 m/s corresponds to about 5m of depth.

SkunkPrince · Apr 30, 2021

I have a Seiko watch intended for Japanese market and the instruction manual for 30m water resistance says something to the effect of, don't put this watch under running water and it is barely splashproof.

One wonders....

jmnav · Apr 30, 2021

All I can tell you is this:
* "Water resistant", despite its related ISO (2810) doesn't insure standing named depth for long, so it's very much up to the brand's reputation how confident you should feel about it.
* Achieving water resistancy for all but most demanding water-related activities is quite easy with a proper design and quality assurance practices (with the exception of the thinniest most dressier watches)
* Current oils and gaskets can last for many years on proper shape.
* All in all the only watch that can be flooded, is the one that see water.

The wristwatch I wear the most (by a large margin) is a Speedmaster Mk40 I own since 2007 when it was bought new. Regarding this 30M rated watch...
* Omega publishes their water rates are "mean it".
* I wear it 24x7. That means I sleep with it, take shower with it, bath in the beach or the pool with it, etc.
* Its first revision was DEC/2020.
* Never flooded.

PS: in the meantime, I read the whole thread. I did quite long ago the calculations (over-envelope level, truth be told), and I'm on @Archer 's side. Even with good safe margins, about half an ATM is the largest difference that made sense.

Lurk41 · Apr 30, 2021

Archer
This is the "dynamic pressure" argument. It is brought up every time there is a discussion on water resistance. Many people just assume that moving your arms will be enough to make a significant difference to the pressure a watch experiences under water. I always challenge these people to do the math to prove their theory - I have yet to have someone take me up on that. Will you be the first?

Dan S
I'm happy to show the calculations if anyone is interested. But the bottom line is that even very rapid motion wouldn't result in dynamic pressure that is equivalent to more than a few meters of additional hydrostatic pressure. For example, a velocity of 10 m/s corresponds to about 5m of depth.

Not directly linked to watches but a couple of years I read a research article on that. They used CFD to calculate the pressure on the hand of professional swimmers. It was negligible for a watch, like 0.1bar more at peak level. (the study was larger than just pressure calculation, they were trying to find the optimal hand position)

So, unless someone thinks the case design could create some incredible pressure points... we should be safe by sticking to the rating. 1m is 1m

STANDY · Apr 30, 2021

C Concretepuppy
Yes, thanks again, that's a pretty definitive Omega depth chart right there, i haven't any watch instruction manuals from any manufacturers so can't make any claims about their caveats, it was a shoot from the hip assumption that i made based on corporate interests being a bit more important than the accurate marketing of products, i didn't mean to give the impression that the caveats (or lack of) listed the types of liquid their products can be immersed in with or without arm movement but i suppose that's all covered by using the word "water" in the same sentence as "rated" and "depth" so would by default rule out anything not watery, i imagined the instruction manuals to have a chapter (or at least a paragraph) of "Dos" and Don'ts",
among the Don'ts being things like leaving it on the dashboard of your car while streaking across the Sahara for a dare, as an obvious Don't, but less obvious would be perhaps Don't wear it in a sauna,
or maybe some manufacturers just don't have that chapter, their philosophy is to do what you want to the watch "and we'll repair and decide if the warranty has been voided before we invoice you"
The crazy thing is that your arms don't move much at all while diving or snorkelling, they're best folded across your chest or down at your side, which i must admit makes the dynamic arm movement increasing water molecule much less of a possibility even if it's more through the user's performance than physics, the physics behind the theory holds water for me but certainly not in the time frame that the manufacturer states the seals or gaskets to be checked, would be interesting from a watch likers point of view to see the condition of the seals and pressure test results of two identical dive watches after a year of diving every day at the same depths, one in the Caribbean and one in Norway, a project

But to change the dynamic pressure of water under water you need to move your arms about 1-2000 times faster that it is physically possible so the dynamic pressure argument is internet urban myth or what we divers call keyboard

Dan S · Apr 30, 2021

STANDY
But to change the dynamic pressure of water under water you need to move your arms about 1-2000 times faster that it is physically possible so the dynamic pressure argument is internet urban myth or what we divers call keyboard

Yes, if we're thinking about arm motion, then 2 m/s is probably a more realistic limit, which corresponds to a pressure head of about 0.2 meters. Above, I used 10 m/s as an upper limit thinking more about a jet of water hitting the watch, which could be a higher velocity than arm movement.

Concretepuppy · Apr 30, 2021

Archer
You state that you don't have the mathematical wherewithal to do the calculations, but then state that you believe the physics holds up?

What are you basing that one if it's not mathematical calculations?

Mathematical wherewithal, that's quite a blow i didn't realise i was that thick, is there anything less than a Jawa,
The physics holds up for me because i based it on principle not maths calculations, my thinking (which i know is now being called into question, but when i read it, it didn't seem like the science fiction it's being perceived as now) was that between the seal (or gasket whatever it's correct name is) and the watch casing, there is a gap, an incredibly small gap yes, so small that i daren't even suggest a unit of measurement before i get myself into uncharted territory again, but the seal and the case do not amalgamate into one form if we can agree on that, they remain separate, and even though the gap is so so small if you could shrink to the size of a quark and exist in that space it could possibly look like a chasm around you, and a water molecule would be bigger than the chasm but being flexible and pushed hard enough it could squeeze through eventually, maybe even easier with a seal that hasn't been replaced as it should and is deteriorating, so, the more force exerted on the water molecule(s) the more likely they are to get through, just a hypothesis because i can't prove it obviously, i wouldn't have a scooby where to begin, but the principle seems feasible, especially if the size of the molecule of water is usually constant, the gap between the seal and the case is constant, and the force exerted is the only thing that is variable, that force being pressure change due to depth and even though it seems negligible, arm movement, like a dripping tap eventually filling a bath effect, originally way back about 10 posts ago i think i was trying to say that a rating of 5atm although equivalent to the pressure at 50m under water, didn't necessarily mean it would be able to survive multiple 50m dives in open water, but it can survive sitting still at the bottom of a tank 50m deep, but if the majority of the folk in the thread are saying is that arm movement at 50m does not cause the water molecules to exert any more appreciable force on the seal/gasket, than arm movement on the surface and my wild imaginings about there being a gap between the watch case and seal are the ramblings of a thing-bloke, (can't think of an appropriate word, i'm sure a schizo pizza customer can) then shoot me down please and put a stop to this finally,
i'm only putting forward an idea based on something i read which doesn't seem too far fetched, not stating it as concrete fact, if i gave that impression before i'll take it back and eat it with one of your boldest sauces

Dan S · Apr 30, 2021

C Concretepuppy
Mathematical wherewithal, that's quite a blow i didn't realise i was that thick, is there anything less than a Jawa,
The physics holds up for me because i based it on principle not maths calculations, my thinking (which i know is now being called into question, but when i read it, it didn't seem like the science fiction it's being perceived as now) was that between the seal (or gasket whatever it's correct name is) and the watch casing, there is a gap, an incredibly small gap yes, so small that i daren't even suggest a unit of measurement before i get myself into uncharted territory again, but the seal and the case do not amalgamate into one form if we can agree on that, they remain separate, and even though the gap is so so small if you could shrink to the size of a quark and exist in that space it could possibly look like a chasm around you, and a water molecule would be bigger than the chasm but being flexible and pushed hard enough it could squeeze through eventually, maybe even easier with a seal that hasn't been replaced as it should and is deteriorating, so, the more force exerted on the water molecule(s) the more likely they are to get through, just a hypothesis because i can't prove it obviously, i wouldn't have a scooby where to begin, but the principle seems feasible, especially if the size of the molecule of water is usually constant, the gap between the seal and the case is constant, and the force exerted is the only thing that is variable, that force being pressure change due to depth and even though it seems negligible, arm movement, like a dripping tap eventually filling a bath effect, originally way back about 10 posts ago i think i was trying to say that a rating of 5atm although equivalent to the pressure at 50m under water, didn't necessarily mean it would be able to survive multiple 50m dives in open water, but it can survive sitting still at the bottom of a tank 50m deep, but if the majority of the folk in the thread are saying is that arm movement at 50m does not cause the water molecules to exert any more appreciable force on the seal/gasket, than arm movement on the surface and my wild imaginings about there being a gap between the watch case and seal are the ramblings of a thing-bloke, (can't think of an appropriate word, i'm sure a schizo pizza customer can) then shoot me down please and put a stop to this finally,
i'm only putting forward an idea based on something i read which doesn't seem too far fetched, not stating it as concrete fact, if i gave that impression before i'll take it back and eat it with one of your boldest sauces

If you are interested in understanding this from the traditional macroscopic perspective, the Bernoulli equation would be a good starting point. Approaching it from the molecular/nanoscale perspective will just result in hand-waving (no pun intended), and is not going to be very helpful for a quantitative calculation.

RI Omega Fan · Apr 30, 2021

C Concretepuppy
Mathematical wherewithal, that's quite a blow i didn't realise i was that thick, is there anything less than a Jawa,
The physics holds up for me because i based it on principle not maths calculations, my thinking (which i know is now being called into question, but when i read it, it didn't seem like the science fiction it's being perceived as now) was that between the seal (or gasket whatever it's correct name is) and the watch casing, there is a gap, an incredibly small gap yes, so small that i daren't even suggest a unit of measurement before i get myself into uncharted territory again, but the seal and the case do not amalgamate into one form if we can agree on that, they remain separate, and even though the gap is so so small if you could shrink to the size of a quark and exist in that space it could possibly look like a chasm around you, and a water molecule would be bigger than the chasm but being flexible and pushed hard enough it could squeeze through eventually, maybe even easier with a seal that hasn't been replaced as it should and is deteriorating, so, the more force exerted on the water molecule(s) the more likely they are to get through, just a hypothesis because i can't prove it obviously, i wouldn't have a scooby where to begin, but the principle seems feasible, especially if the size of the molecule of water is usually constant, the gap between the seal and the case is constant, and the force exerted is the only thing that is variable, that force being pressure change due to depth and even though it seems negligible, arm movement, like a dripping tap eventually filling a bath effect, originally way back about 10 posts ago i think i was trying to say that a rating of 5atm although equivalent to the pressure at 50m under water, didn't necessarily mean it would be able to survive multiple 50m dives in open water, but it can survive sitting still at the bottom of a tank 50m deep, but if the majority of the folk in the thread are saying is that arm movement at 50m does not cause the water molecules to exert any more appreciable force on the seal/gasket, than arm movement on the surface and my wild imaginings about there being a gap between the watch case and seal are the ramblings of a thing-bloke, (can't think of an appropriate word, i'm sure a schizo pizza customer can) then shoot me down please and put a stop to this finally,
i'm only putting forward an idea based on something i read which doesn't seem too far fetched, not stating it as concrete fact, if i gave that impression before i'll take it back and eat it with one of your boldest sauces

That could be the longest sentence ever written.

Archer · Apr 30, 2021

C Concretepuppy
Mathematical wherewithal, that's quite a blow i didn't realise i was that thick, is there anything less than a Jawa,
The physics holds up for me because i based it on principle not maths calculations,

I didn’t mean for it to be “quite a blow” but I admit there appear to be some sort of linguistic differences that might be playing into this. You said you didn’t have the maths...I was simply saying the same thing, but references to “Jawa” that you keep making are somewhat puzzling, so sorry if I misunderstood you and you do actually have the ability to do these calculations.

And to be clear, calculations are what is required as I said in my longer reply.

Back in my first days on the job as a fresh new engineer, my first assignment was the design of a lifting device intended to dump a batch of product into a hopper. It was a 7 meter or so high steel structure dumping roughly 1000 kg containers of product. I dutifully made all the drawings, on an actual drafting board by hand, and submitted my design to the more senior engineers for checks. The device was powered by an electric chain hoist held by a pin and clevis arrangement at the very top of the device.

Of course I was not going to get my design approved to be built with principle, so I had to show my calculations to ensure that critical points in the structure, such as that clevis, wouldn’t fail. Gut feelings aren’t proof...and lack of proof is why this same thing keeps getting trotted out time and time again. You are not the first, and you surely won’t be the last to use this, but I’m still waiting for the calculations. If you do have the ability, and prove that moving your arms will cause some significant pressure spike, I’m sure the watch world will be interested in your findings.

Cheers, Al

Pazzo · Apr 30, 2021

Archer
.......

Back in my first days on the job as a fresh new engineer, my first assignment was the design of a lifting device intended to dump a batch of product into a hopper. It was a 7 meter or so high steel structure dumping roughly 1000 kg containers of product. I dutifully made all the drawings, ...

......

For some reason, Leonardo da Vinci came to mind. ... 😀

STANDY · Apr 30, 2021

@Concretepuppy

Myth vs Reality

https://www.watchuseek.com/threads/the-water-resistance-myth-vs-the-reality.159142/#post-1086618

Concretepuppy · May 1, 2021

Thanks for the watchuseek link, i haven't read it all yet (still recovering from the devastating news of having no wherewithal) but will do and it looks like an interesting read, from a watch liking person's perspective, especially the paragraph headed "So what do all of this means?" The author lists depth ratings next to their suitable activity, ie, a 30m or 50m rating is not suitable for swimming or diving, which is the point i thought i was making, even if offered up as a sloppy ill-explained mess in a one sentence ramble, that a watch's depth rating doesn't mean it can be taken to that depth but it can withstand the equivalent atm pressure, and i fell into the moving arm trap, just thirteen short years after the author did

It was just an idea i was backing, i couldn't and still can't offer any proof or calculations, just the principle, out of date and wrong as it may be i'd prefer to have it set on fire and danced on, then consider it as having been something i've learnt, than to stick to it rigidly as if it's my only life raft, thanks all for your patience and time to respond, i'm sure Benoulli was a great guy but i'm not going to be using his equation so i'll take your word for it, and that does make more sense than what i'd been saying, increase in water pressure is inversely proportional to it's flow speed, the molecules being more tightly packed together and less room to move
Still though, those water molecules are pretty small, you have to admit

How about that Speedmaster in the vacuum of space then...

STANDY · May 1, 2021

So a flashlight I have has a rating of 60m and a watch has a rating of 50m but I only dive 40m
I’m good to go with both. It’s that easy.

But marketing says you have to buy a 300m watch to dive 40m in.

Think about why those charts are set out like they are 😗 Basically the same reason they put the “Do not eat” on the silica gel in a packet of food....
(So dumbarses don’t dive with a dress watch but your dress watch is rated so if you fall in a pool like a dumbarse your OK)

Concretepuppy · May 1, 2021

STANDY
So a flashlight I have has a rating of 60m and a watch has a rating of 50m but I only dive 40m
I’m good to go with both. It’s that easy.

But marketing says you have to buy a 300m watch to dive 40m in.

Think about why those charts are set out like they are 😗 Basically the same reason they put the “Do not eat” on the silica gel in a packet of food....
(So dumbarses don’t dive with a dress watch but your dress watch is rated so if you fall in a pool like a dumbarse your OK)

But but but but sir that means the link you posted for me to read contradicts what you just said, now i don't know what to think again, can you not add the flashlight rating to the watch rating and dive to 110m safely then? i thought that was how it worked, then if you put on another watch also rated to 50m you can dive to 160m

If only it was that easy, then we wouldn't have gigabytes of posts and threads, and, posts linking to threads with links to posts of other forums and paragraphs of online stuff to wade through and absorb or weigh up and dismiss,
but the amount of discussion it's generated would indicate the opposite, not simple or easy and very much open to discussion with a difference of opinion, probably like you said because of marketing muddying the waters, i'm not experienced enough at watchy stuff or physics at molecular level to state anything as a fact, but i do ask questions or hypothesise ideas i've heard that make (or made) sense to me, and quite happy to dismiss those hypotheses if someone more qualified or experienced than me shows me the correct version of the facts,
online forums always follow a similar pattern, members with a high volume of posts are considered as being infallible and beyond question if they say something, anyone of lower standing questioning them is usually shot down and ridiculed by several of the highly revered member's disciples who dream of having such status one day,
thank goodness this isn't one of those forums and a lowly Jawa of a member like me can question a Jedi member or even Yoda himself and come away having learnt something after a swapping of different opinions or facts or even things we've heard and read, without being berated for asking, or even offering up out of date ideas like i've been doing, one of the best ways to learn is to question and ask why or how, then be put right, which i've always done, it's just a pity i haven't retained everything i've learnt after asking

STANDY · May 1, 2021

So if a speed sign says 60 it means 60.
If a bridge height sign is 4.2m its pretty sure it’s 4.2m underneath.
So if a watch says 50m 😉

Pvt-Public · May 1, 2021

Sounds like there are plenty of people out there really just don’t under stand the “maths”, the physics, or even the reality of the situation, and actually need the “don’t eat the silica packs” and other warnings.

Lurk41 · May 1, 2021

STANDY
So if a watch says 50m

And that is how people are getting confused...

😁

Is 50 meters water resistance too risky?

Archer

hronists

Dan S

SkunkPrince

jmnav

Lurk41

STANDY

Dan S

Concretepuppy

Dan S

RI Omega Fan

Archer

Pazzo

STANDY

Concretepuppy

STANDY

Concretepuppy

STANDY

Pvt-Public

Lurk41

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