Advantages to Imperial units

[RainPilot]

60 seconds to a minute and 60 minutes to an hour come from the shape of the earth. 360 degrees for the sun to "move" around the centre of the earth so 60 makes division easier.

Rule of thirds in metric, I just use a third of what the start pressure was in my tank. Either 200 or 230 bar. Am I doing it wrong?

 

[SecT]

Rule of thirds in metric, I just use a third of what the start pressure was in my tank. Either 200 or 230 bar. Am I doing it wrong?

No thats the way to do it.

Regarding AL80 is 3000 psi and in bar 200 with filled tank.

 

[billt4sf]

To answer the OPs question: there are none.

What was my question?

 

[AlexL]

10 hours to a day, 100 centihours to an hour.1000 millihours to an hour, It wouldn't be much different than the relationship between inches and centimeters.

using seconds as the basis of time seems more reasonable, makes it a whole lot easier to not re-tool all the software. dont even have to change time_t around or restart the epoch! 16 2/3 minutes per kilosecond, 3.6 kiloseconds per hour, 86.4 kiloseconds per day, 604.8 kiloseconds per week, 31.471 megaseconds per year.

then you get into international fixed calendar conversions, aka 13 month plan (2.149 megaseconds per month), which makes a lot of sense, but will never implemented.

 

[Centrals]

What was my question?

There was no answer for your question because you didn't ask one!!

However, I would not ascend from 30m with only 70bar left in a 11L tank. It is too fine a margin to play with. I would have ascent with 100 bar left. But that is me.

 

[dberry]

The title of the thread was so improbable that I mentally added a question mark.

 

[JohnnyC]

The worst are the savages that use both imperial and metric fasteners on a machined part. We're all civilized people capable of adaptation. Yet these a**holes just go and screw it up......savages I tell you....

 

[Kevrumbo]

I am from one of the three countries in the world that use Imperial units (feet, pounds, etc.) and I have found one advantage to this (apologies to Dr. Neil deGrasse Tyson).

My depth reminds me about how much air I should have to start my ascent, to wit:

When I have 1000 lbs, I start ascending if I am 100 ft deep,
When I have 800 lbs, I start ascending if I am 80 ft deep,
...etc... (I do not go deeper than 30m as a rule).

Now before you can say "depending on conditions", I totally agree this is assuming benign conditions below *and* above.

Now before you say "WHAT?!? Way too early!" -- I say: this is what works for me -- as a guideline, because I am a heavy breather.

Now before you say: "You gotta work on your air consumption, buddy", I say: Tell me something I *don't* know!

Now let the compliments, condolences, and criticisms roll in.

Have a happy.

- Bill

I think these below are the older Rock Bottom Rules-of-Thumb in US Imperial that you're trying to emulate:

Here are my "battlefield calculations" for reef divers:

1. Rock Bottom: 100psi per 10 fsw for LP104/LP95/HP120s/HP130, 100 psi per 10 fsw + 300 psi for Al80s/HP100s/LP72 -- 500 psi minimum for all calcuations.
2. 0.75 SAC: 300 psi per 10 mins per ATA for Al80/HP100/LP72, 200 psi per 10 mins per ATA for LP104/LP95/HP120s/HP130.

So, for a 30 min dive to 100 fsw on an HP130, I expect my SAC rate to be 800 psi / 10 mins (actually these days I expect my SAC rate to be 600 psi / 10 mins or better, but for planning purposes lets use 0.75 SAC) and I expect to have used 800 psi at 10 mins, 1600 psi at 20 mins and 2400 psi at 30 mins. 3500 - 2400 psi is 1100 psi which is above my rock bottom, so the gas plan is solid and I can dive and I know where I expect to be with gas at various checkpoints on the dive. Similarly, if I'm diving with a relatively newer diver as a buddy that I've never dove with before who is on an HP100 and we go to 100 fsw, I know that at 10 mins they could have burned through as much as 1200 psi, and could burn up to 2400 psi 20 mins in. I'll be planning on a max bottom time at 100 of 20 mins and I'll check 10 mins in to see how close they are to 2300 psi and if they're under that value I know that we need to leave sooner than that. Everything figured out with very simple math, on the surface, before the dive.

Again, also recommend using a dual unit SPG:
Extreme Exposure

 

[Hoag]

Or, just to throw a curveball into the mix ... I worked for over 30 years in Air Defence. Within the aviation world, we don't use a "pure" form of either the metric or the imperial system.

• Time was measured conventionally, but based on "Zulu" (Greenwich Mean Time or GMT)
• Distance was measured in Nautical Miles (nm) not in KM or Statute Miles, and was always expressed as a single number Twenty eight, not Two Eight)
  
• Speed was measured in either Knots (Kts) (1 Kt = 1 nm/hour) or in Mach which is a ratio and has NO units
• Altitude was measured in Feet if below 18,000 feet or in Flight Level (FL) if above 18,000 feet (1 FL + 100 feet so a typical commercial airliner cruising at 33,000 feet is cruising at FL330)
• Altitude is also expressed as Above ground level (AGL) or Above Sea Level (ASL) depending on the application.
• Direction was based on a standard 360 degrees, but was expressed as "Tracking" if describing the aircraft's path along the ground or as "Heading" if describing the direction that the nose of the aircraft was pointing. Direction was always expressed as three individual numbers. (If something was heading due west for example, it was heading Two seven Zero, not Two Hundred and Seventy.)
• Although the units were never mentioned, air pressure was in Inches of Mercury and was expressed as individual numbers usually prefaced by the word "Altimeter"

 

[StefinSB]

The title of the thread was so improbable that I mentally added a question mark.

Exactly.