Trip Report Egypt - BD (almost E) - Emperor Elite

[Parlem]

Regarding tank sizes in the Red Sea, my best guess based on personal experience would be that what they call "12L" are, in fact, AL80. This is actually just under 12L.
And their "15L" are AL100.
The latter is notorious for the buoyancy changes as your dive progresses.

 

[bvbellomo]

Part of the problem is neither the metric nor Imperial units really describe the tank. We call the same tank an Aluminum 80 or 12 liters. But 80 cubic feet is 2265.35 liters and the actual tank volume is closer to 11 liters - so neither number tells us much.

This is important to me, as my next trip will give me a variety of choices, and I'd like to know what to expect. Although in practice, I probably will have the option of an Aluminum 80 or only 1 other choice that is larger.

 

[JustSurfaceInterval]

And to add to this mess, your pressure gauge is in PSI, mine in Bar....
I learned a 12 L tank with 200 bar = 2400 L at 1 bar. Therefore i prefer taking a 12 L rather an AL 80.

 

[bvbellomo]

And to add to this mess, your pressure gauge is in PSI, mine in Bar....
I learned a 12 L tank with 200 bar = 2400 L at 1 bar. Therefore i prefer taking a 12 L rather an AL 80.

If you tell me your pressure in Bar, I can calculate your pressure in PSI (and vice versa). But if tell me you have a 12 liter tank, and I can't calculate anything - the only thing that "12" refers to is what people call that tank.

 

[Dan]

That’s the British revenge after losing the war in 1776.

Sorry to hear about your camera problem.

Too bad you missed seeing the Oceanic Whitetip (Carcharhinus Longimanus). That’s was the main reason I wanted to dive in BDE. Hopefully you’ll get a chance to see and capture it with your camera next time. At least you have something to look forward to in your next trip to Red Sea.

 

[JustSurfaceInterval]

If you tell me your pressure in Bar, I can calculate your pressure in PSI (and vice versa). But if tell me you have a 12 liter tank, and I can't calculate anything - the only thing that "12" refers to is what people call that tank.

Not quite: the 12 refers to the inner volume of that tank, as well as the 15 does in a 15 L tank.
And i accept that you are good in maths, even under water to take my bar and multiply by 14.5 to get your PSI.

 

[bvbellomo]

From the spec sheets I can find, the Aluminum 80 has an interior volume of 11.1 liters and the 100 is 13.2 liters. So this probably was rounded up for marketing reasons.

You can calculate the metric for these 2 tanks by multiplying by 0.15,
e.g. 80 cubic feet * 0.15 liters/cubic foot = 12 liters
e.g. 100 cubic feet * 0.15 liters/cubic foot = 15 liters

But I don't know if this is an actual, logical reason for this conversion or if it just happens to work with these 2 tank sizes.

 

[lowwall]

Until you are truly happy that you squared away with your gear and trim, you might want to compromise on the camera.

I bring a cheap gopro clone. It's normally clipped off to a d-ring. If there is something truly spectacular or if nothing else is going on, I'll unclip it and get some shots or a short video. Of course the quality is not great, but it's good enough to show the highlights to friends and family and jog your memory of the dive.

 

[Dan]

From the spec sheets I can find, the Aluminum 80 has an interior volume of 11.1 liters and the 100 is 13.2 liters. So this probably was rounded up for marketing reasons.

You can calculate the metric for these 2 tanks by multiplying by 0.15,
e.g. 80 cubic feet * 0.15 liters/cubic foot = 12 liters
e.g. 100 cubic feet * 0.15 liters/cubic foot = 15 liters

But I don't know if this is an actual, logical reason for this conversion or if it just happens to work with these 2 tank sizes.

Like I said we got screwed by the British. They came to America, introduced this weird imperial units of foot, pound, etc., went home and used metric. So we are stuck with it.

The 12L is based on the physical volume of the tank when we fill it up with water (incompressible fluid), which makes sense to me. Our weird system uses the volume of the gas in the tank at 1 atm pressure X the tank atm pressure, which doesn’t make sense as the tank pressure will vary.

So a 12L tank at 3000 psi (204 atm) =
12L/atm x 1cft/28.317L x 204 atm = 86 cft

A 11.1L tank at 3000 psi =
11.1L x 1cft/28.317L x 204 atm = 80 cft.

A 11.1L tank at 3500 psi (238 atm) =
11.1L x 1cft/28.317L x 238 atm = 93 cft.
Therefore we’ll have a “bigger” tank by compressing the heck out of that “AL80”

 

[Dan]

I think they gave you a S100 cylinder (13 liter aluminum). They must be the most horrible cylinders to dive with i.m.o., extremely heavy to start with and become incredibly buoyant when empty, they have the worst swing in characteristics I have ever experienced in a dive cylinder. My experience with these are you weight to be neutral at the end of the dive and manage being overweight at the start.
Pity about your camera, some shots of the hammers would have been great, at least nothing can take your memories and it sound like you had a fun trip.

I’ll use Steel 100 or Steel 15L instead, not the Aluminum one for better buoyancy control at different tank pressures.