AL80 to 132ft (caution-contains math)

[Melicertes]

So... your math is off, because your calculations are off, because everyone breathes the same... and every dive should be the same.. and every diver should be the same... etc... etc... etc... worthless waste of time...Welcome to planning your dives in South Florida, USA....

:11: Looking at your profile I'm now even more concerned than when I read your comments before - I really do hope you are not teaching your students that all divers are the same and that they all breathe the same and that everything should always be the same etc. etc. etc
Do you really believe that BS or are you trawling for attention? Besides, would you care in showing the OP where exactly you believe their math is "off"?

 

[Steve_Dives]

I wouldn't do a dive to 130 feet with a single AL80. I'd prefer larger tanks, and a pony/doubles to have a redundant system.

But the gas planning calculation is worth discussing. At a minimum it might prevent someone form just hopping in on a trust me dive.

I used 0.8 as an air consumption based on the OP. I added a 1 minute deep stop at half max depth. I ran 130 feet for max depth. Stressed diver air consumption rates (slightly over 1). A 3 minute stop at 20 feet. I wanted 500 psi remaining when at the surface in case there is a gauge error, to have air to inflate the BC, to have air to power an air horn, or if surface conditions make snorkeling difficult. And I assumed tank capacity was 76 cubic feet. Oh, and I assume it takes a minute to get stuff together at depth before beginning the ascent. I get a turn pressure of 2500 psi (rounding up to the nearest hundred psi). With a descent rate at 60 fpm, there's basically enough time drop to 130 and signal your buddy to begin the ascent...if they're looking right at you and aren't narced out of the gourd.

 

[fppf]

rather than trust post from people you don't know and could be full of BS, why don't you take a class that teaches proper dive plaining?

I have done 130 foot dives on an AL 80 using thirds.

 

[Nemrod]

After trying to read this thread my brain got tired.

All I know is that I can run Nitrox 28 etc and dive a full dive right to the edge of deco at 130 feet and return to my boat with 800 to 1,000 psi using an aluminum 80.

There are no resl limits on your descent rate, I plummet to the bottom to maximize my bottom time. I ascend at 60 FPM to 60 or even 30 feet before going to a slower 30 fpm rate.N

 

[AzAtty]

Courtesy of Lamont: a walk through of how to calculate your rock bottom and some potential numbers to use.

Rock Bottom and Gas Management for Recreational Divers

 

[Brewone0to]

Well guys,
I know your having a good time kicking "Cooltech" around on this one.
But, I gotta' tell you that he is not full of --it about that dive.
I know this because I was there that day, along with 30-40 other SB divers.
Do a search here, I think that day was a "Turkey Dive".
But we "Conch Divers" get together as a group of divers often so I could be wrong about which ScubaBoard Event it was.

VB=Venice Beach, Florida and unless your ready for a real long swim, you'll have problems finding anything much deeper that 22-24' there.
If you have problems with his statement of his gas usage, perhaps you should check with "NetDoc" about his gas consumption.
We do regular checks on Him just to see if he has gills.

As for the "cave fills", I've had my HP100's pumped up 20% many,many times.
This type of fill occurs so frequently in North-Central Florida that it has been given the codename "Cave Country Fill" or "Cave Fill",named for the many caves found here.
(Note*These fills are reserved for steel tanks only)

PS: My personal best depth/time on an Al80 was
42min with 142' max depth, 6-7min bottom time.
This was in an overhead cave environment,
But at least I wasn't solo diving on that dive.

OK I'm prepared now..............Let The Stonings Begin

 

[hudson]

why don't you take a class that teaches proper dive plaining?

Unfortunately, there aren't any classes that I'm aware of around here that does that, all the way to deco procedures.. and by then, it's a bit too late. Besides, there is nothing magical about rock bottom planning, you don't need a class for that.

As for all the myriad of things that can go wrong.. it's not difficult to mitigate those with a little common sense. Know your narc response. Don't do this in an unfamiliar area under unfavorable conditions. If you don't have redundant air, make sure your buddy is on the ball and close at hand. Stick to the plan. If all those conditions are met, I don't see a problem (other than a short bottom time)

Consider including a deep stop in your rock bottom.

 

[BHB ScubaTroll]

No harm in understanding what the computer is doing, though. Right?

No, there is no harm and it will probably help you understand more...

Apologies for your question getting the off-track hijack... I didn't expect some would attempt to discredit me because they didn't agree with my statement (Then, find a single post from the past... which is correct and accurate, in an attempt to do just that without knowing the dive site...) Then, others would take my responses to the person (I quoted in the response, and one answer that was sarcasm... ) and attempt to use them as some answer to your original post.

So, please accept an apology for myself (and others) not allowing your question to continue on track.

 

[AbyssalPlains]

Originally Posted by CoolTech
Venice Beach... Single HP 149. 4 1/2 hours. The only reason I surfaced... I got hungry. I still had 1,500 PSI left in the tank.

Yeah right.

 

[BHB ScubaTroll]

Well, I had to pick something. My descents are usually along a steep quarry wall. 60 just seemed like a reasonable number at the time.

Which explains why you are doing the flat table calculations... Using a computer for Multi-level diving (reef, wreck...) can maximize your time and NDLs (which I am sure you are aware). If you dive to 90' (sand), but average 55', a flat table calculation will severely limit your time at depth needlessly.

This is what I "meant" with my first response - Before your question was hijacked.