US divers using metric?

[JMBL]

However, unlike the french, all other populations will try to be understood by using a 2nd language. French wont even try even when theire not in france...

That's the trend for sure, but don't make a rule out of it. I speak English, German, dabble a bit in Spanish and Italian, then would you say I not French enough ? Besides I've got friends in the US and the UK who don't speak anything but Englsih, so it seems the fault exist somewhere else.

Anyway, there's no need to argue and I stop spoiling the thread.

 

[scagrotto]

just percentages is the best way to do it.

You must deal with an above average sampling of people. Or perhaps, despite being a US territory, most of the divers you encounter in Guam aren't American.

My experience is that a significant portion of people couldn't even tell you what 10% of 100 is. The mere existence of little plastic cards that show what a 15% tip is for any given amount is a serious indictment of typical math ability.

 

[Centrals]

Centrals, thats just cause 10 stones sound less, isnt it?

It is the UNIT rather than anything else.
10 stones or 140 lbs or 63.6 kg?

 

[DiverGuam]

My experience is that a significant portion of people couldn't even tell you what 10% of 100 is.

It's 110%, right? That's why we always say giving 110% right?

 

[PfcAJ]

Stick with the customary units for the location that you're diving in. When I travel abroad, I adjust to suit the locals. My Euro/Asia buddies do the same when they come here.

Eventually, you're going to need to communicate something underwater and have a "derp" moment when you botch the conversion in your head.

Set your stuff to feet, get used to PSI, and don't be "that guy".

 

[Kevrumbo]

Stick with the customary units for the location that you're diving in. When I travel abroad, I adjust to suit the locals. My Euro/Asia buddies do the same when they come here.

Eventually, you're going to need to communicate something underwater and have a "derp" moment when you botch the conversion in your head.

Set your stuff to feet, get used to PSI, and don't be "that guy".

*Ugh* --typical national-centric American attitude.

Here AJ, I'll buy ya one of these so ya won't have to be "that guy" wherever you go diving in the World. . .

SCUBAPRO - DUAL PRESSURE GAUGE

(I'll even take it out of the boot for ya! )

 

[PfcAJ]

I just said that I use metric when abroad...

If you really want to send me a trinket PM me. Unfortunately, I don't think I'll be able to send you a new personality.

 

[Kevrumbo]

I just said that I use metric when abroad...

If you really want to send me a trinket PM me. Unfortunately, I don't think I'll be able to send you a new personality.

If you were consistent (and smarter), you would utilize the world standard all the time --the best uses the best. . .

Unfortuantely, I can't give you a new & better brain as a trinket either. . .

---------- Post added July 1st, 2014 at 10:12 PM ----------

Gas Blending in Metric is a lot more intuitive as well. . .

Starting from an empty tank or set of tanks (5 .5L or AL40 deco cylinder; and 11L or AL80 twinset backgas Cylinders):

Nitrox 50 (add 37% O2):
For every 100 bar of Eanx50 deco mix, you need 37 bar of pure O2 and top off the remainder with [hyper-filtered clean] Air;

Nitrox 32 (add 14% O2):
For every 100 bar of Eanx32 mix, you need 14 bar of pure O2 and top off the remainder with Air;

20/20 Trimix (add 4% O2 & 20% Helium):
For every 100 bar of 20/20 Trimix, you need 4 bar of pure O2, 20 bar of He and top off remainder with Air;

25/25 Triox (add 12% O2 & 25% Helium):
For every 100 bar of 25/25 Triox, you need 12 bar of pure O2, 25 bar of He and top off remainder with Air;

30/30 Triox (add 19% O2 & 30% Helium):
For every 100 bar of 30/30 Triox, you need 19 bar of pure O2, 30 bar of He and top off remainder with Air;

21/35 Trimix (add 9% O2 & 35% Helium):
For every 100 bar of 21/35 Trimix, you need 9 bar of pure O2, 35 bar of He and top off remainder with Air;

18/45 Trimix (add 8% O2 & 45% Helium):
For every 100 bar of 18/45 Trimix, you need 8 bar of pure O2, 45 bar of He and top off remainder with Air;

15/55 Trimix (add 7% O2 & 55% Helium):
For every 100 bar of 15/55 Trimix, you need 7 bar of pure O2, 55 bar of He and top off remainder with Air;

12/60 Trimix (add 5% O2 & 60% Helium):
For every 100 bar of 12/60 Trimix, you need 5 bar of pure O2, 60 bar of He and top off remainder with Air;

10/70 Trimix (add 4.5% O2 & 70% Helium):
For every 100 bar of 10/70 Trimix, you need 4.5 bar of pure O2, 70 bar of He and top off remainder with Air.

Using a 11L (AL80) cylinder, or set of twin 11L doubles (double AL80's) for a total of 22L, a full tank or set of tanks is 200 bar:
-->Therefore, all you need is 2 times the amount in bar for O2 (& He for Trimix) from above recipes for a particular mixture.

Example)
21/35 Trimix requires blending 9% Oxygen and and 35% Helium; Therefore a full 11L (Al80) cylinder(s) at 200 bar total pressure needs 18 bar of O2 (2 times 9 bar equals 18 bar), and 70 bar of Helium (2 times 35 bar equals 70 bar); and top off remainder to 200 bar with [hyper-filtered clean] Air.

Now how did we get the "cookbook recipes" for blending the particular mixtures above? And why for instance with Nitrox 50, can't we use 50 bar of Oxygen and 50 bar of Nitrogen for every 100 bar of Eanx50 to blend a seemingly real intuitive "half & half" mixture?

The answer is YES! You can blend 50 bar of O2 and 50 bar of N2 -->If you are mixing pure O2 AND PURE N2 TOGETHER!!!
But for practical means, why do you need pure N2 when you can just use Air with its natural constituent contribution of 21% Oxygen & 79% Nitrogen?

Using Air this time, let's blend 100 bar of deco mix Nitrox 50:
We know empirically that for every 100 bar of Eanx50, 50 bar must be O2 and 50 bar must be N2;
Quantitatively then, how much Air do we need to add in order to give us a N2 amount of 50 bar?

Algebraically and by Dalton's Law, you divide 50 bar N2 by 79% (the %age of Nitrogen in Air), and this yields approximately 63 bar of Air needed. And of this 63 bar of Air, 21% of it (the %age of Oxygen in Air) contributes to the amount needed for O2: approx 13 bar of Oxygen.

Therefore, instead of initially mixing in a full 50 bar of O2, and since we're using Air instead pure N2, you only need 50 bar minus the 13 bar Oxygen contribution from Air, which equals 37 bar. So hence the cookbook recipe of for every 100 bar of Nitrox 50, add 37 bar of pure O2, and fill the remainder with Air to 100 bar (100 bar total minus 37 bar of O2 equals 63 bar --the amount of Air needed for N2 which we calculated above).

Now to fill an empty 5.5L/bar deco tank (same as an AL40) with Nitrox 50, we need 200 bar of the above recipe (i.e. "For every 100 bar of Eanx50, add 37 bar of pure O2, and then fill the remainder with Air"). Therefore just multiply 37 bar by 2 which equals 74 bar of O2 needed, and then fill the remainder with Air to the total fill pressure of 200 bar.

Similarly, it all applies also to the Trimix recipes --the only difference is accounting for the exact percentage and amount in bar of the Helium constituent in the total mixture . . .
​

 

[84CJ7]

They would have to start teaching the classes here in metric if they wanted things to change.
The units of measurement are fairly well irrelevant. Someone has to teach us that 130 feet is the recreational depth limit just as much as they would if it were 40 meters. The numbers don't mean anything until we are taught where the limits are, like 35 bar in the tank means time to surface (with no overhead). Your pressure gauge could be just a colored bar graph and be just as effective (outside of tech calculations) since its consumption rate and percentage remaining and not pressure values that are relevant.
Trying to get people here to use metric would require almost retraining rather than just conversions because nobody is used to seeing the important numbers that stick in your head when they are in metric.
Gear wise its easier nowadays with computers, but I still would have a bit of a bother coming up with all metric gauges (I always use full analog backups) since they pretty much have to be special ordered new here which translates to stupidly expensive full retail.

Getting systems changed here is hard, it requires almost a full generation of people to have dual measurements to make the transition like speed limit signs in both kph and mph and gas pumps in liters. Most vehicles would require new gauge packs many of which don't exist in metric.
Tons to change and tons of people too stupid to learn. You want comedy you should have put up a lawn chair when roundabouts first started appearing out here in the rural country where its nothing but old farmers. They still can't grasp the concept of meshing together timing wise like gears rather than treating every entry point to the roundabout like it has a stop sign. We also get a number of close calls and accidents from people assuming a person will exit at a particular point and pulling out when the person is actually using the roundabout for a complete u-turn.

My answer to your buddy question would be that your gauges are yours and his gauges are his and you don't need to try and communicate numbers back and forth. I have never understood why people do that outside of carefully orchestrated tech dives where everyone should be using metric only anyways. Either its time for you to start back or even thumb the dive due to air remaining or it isn't, that's all I care about. I expect everyone to be competent enough to tell me based on their consumption and how long it took to get where we are what their needs are, if they can't figure it out without my involvement they shouldn't be diving.

 

[Storker]

[...]
Nitrox 32 (add 14% O2):
For every 100 bar of Eanx32 mix, you need 14 bar of pure O2 and top off the remainder with Air;
[...]

That's all fine and dandy, provided your gas behaves like an ideal gas. That's a reasonable assumption for tank pressures up to about 230 bar, but if you're filling a 300 bar tank, you'll have to factor in the compressibility of the gas. If if you don't, you'll end up with another mix than you planned for.