Why isn't DIR universally metric?

[liuk3]

Not only DIR but whole US should move to metric system. Staying imperila is not logical. US is all about making life easier and simpler, and with the imperial system is exactly the other way around.

In the U.S., we're just strong enough divers to be able to task load the extra mental math required using the imperial system...

 

[Walter]

If I fill an 11 litre tank

The 11 liters is irrelevant. The tank is empty.

the obscure "rounding up" of working volumes

That has nothing to do with imperial vs metric, that's pure marketing.

 

[Red Sea Shadow]

The 11 liters is irrelevant. The tank is empty.

But it'll be filled! You just multiply the 11 liters by the filling pressure (normally 200 bar) to get the total volume, which is 2,200 liters in this case.

 

[Rhone Man]

I think that is the point. If you are trying to calculate your gas volume for a tank which is at anything other than its rated pressure, you calculate residual volume multiplied by pressure.

• The European start with residual volume, and multiple by pressure in bar.
• The Americans have to calculate my by multiplying working volume by the fraction (actual pressure in PSI / rated working pressure in PSI (including 10% overfill if appropriate)).

One is easy to do in your head. The other isn't.

I grew up using the US system, but even I'll admit the European method is much easier. It might be why BSAC teaches gas planning as part of basic certification, but PADI does not.

 

[Walter]

I doubt that's the reason.

 

[Peter Guy]

Re US/Imperial vs. Idiots/Metric -- There are times when everyone else really is just wrong!

 

[Red Sea Shadow]

I grew up using the US system, but even I'll admit the European method is much easier. It might be why BSAC teaches gas planning as part of basic certification, but PADI does not.

I agree the metric system is easier but I don't think it has anything to do with PADI not teaching gas planning as part of basic certification.

 

[rjack321]

I doubt that's the reason.

PADI doesn't want the liability of saying WHAT a safe pressure to leave the bottom is. They just know that 500psi on the surface is safe so they leave it up to the user to muddy their way to that point (or not).

BSAC has a completely different legal universe and don't seem so paranoid, except about long hoses

 

[mania]

I love you Mania, but that's an issue that should be decided by citizens of the US. When I travel, I encounter many things I would do differently, but I enjoy the differences of the different lands I visit. I don't tell the nice people I meet they should do things my way.

Walter - love you too

And of course it should be decided by Americans. But I do have the right to comment, don't I? Anyway at least I got used to miles and gallons. But calculating the turning point during all my cave dives was a nightmare for me

That's an illogical method. Regardless of what units are used to measure my gas, I need to know how much it holds full, not empty.

It's really easy. Simple calculations -as others already wrote. So let's say you have 80cf tank. This is 12 liters tank (precisely it's 11 point something liters, so we use 12 for easier calculations). You fill it with gas up to 200 bars (my doubles are in fact 300 bars, but this is another story. So you get 2400 liters of gas. Your air consumption is 10 liters/minut. Easy calculations - how long you can stay, how much gas you need and so on.

Let's say you use 15 liter tank (it's 95cf or 105 cf - I'm not sure right now). Again - you fill it up to 200 bars. So you have 3000 liters of gas to be used

But to be fair - in plumbing measures are in inches also in Europe. Not that I'm an expert in plumbing (not at all ) but I've heard it many times - inch or half inch pipe...

 

[elan]

The imperial calcs using tank factors are as easy. No one is using any weird calculations. I know my doubles factor is 6. so I get 1500 psi it's 90 cuf, 1300 psi it's 78cuf. left. Straight an easy.

I grew up on metric but I fail to see a disadvantage of imperial