Aluminum 80s versus larger steel tanks

[cvchief]

Whatever.

When you compile all dives for every dive operation in Cozumel and post the results let me know, until then I'm happy for your dive times.

Ah, no. I showed evidence. I whipped mine out and it is that long, but I think LOTS of people have them that long. At least the people I dive with seem to have long ones too.

Er, length of dive, you know.

Given that, it is on you now to show evidence that that average is 'well under 60 minutes.' Until then..... BS.....



---------- Post added May 10th, 2014 at 01:49 AM ----------

And honestly, you ask why would you not want more air, but then you seem intent on exaggerating the difference. Are you saying the more air isn't enough more air, so it need to be inflated?

 

[Skittl1321]

Skittl..in time I would put bets that you will see your bottom time exceed your 51 min average. Once you conquer your "Freak out" , get more experience with buoyancy, and become more comfortable with the general routine you could very well see those 70 min. dives. Most importantly, Do Not take to heart what others are doing. Take your time, relax your breathing and get your weights right. Overall, experience is the best way to improve your bottom time.

Oh, I was very happy with my times, except when I missed the loggerhead, there wasn't really a day I wished I had been down a lot longer. I was just posting them to point out that I don't think "well under 60" is accurate for an AL80, when I was getting very nearly 60 and with personal conditions that increased my SAC. Perhaps many dives are "well under 60" since some ops apparently impose 45 minute time limits; but that is a function of the op- not the tank size.

---------- Post added May 10th, 2014 at 08:35 AM ----------

Whatever.

When you compile all dives for every dive operation in Cozumel and post the results let me know, until then I'm happy for your dive times.

But you were the first one to come up with a time for AL80s. Did YOU compile dive times for every dive op?
People who dive 80s are telling you that you aren't accurate to say you get "well under 60 minutes" with them.

 

[pjhansman]

What a bizarre, yet typical ScubaBoard thread.....might as well join in the fun...

Let's face it, we pretty much all dive the same reefs in Coz, and we probably dive them with much the same profiles....yes?

So from my logs, my average depth on the last 30 Coz dives is 44.5 feet. My average SAC/RMV (please let's not argue about the terms) is 0.41 cubic ft/min for the same dives.

So by my reckoning, assuming 65 usable cubic feet in an AL80, I theoretically max out at 67 minutes. Sound about right?

And while a SAC/RMV of 0.41 isn't awesome, I find myself in the last group going up pretty much every dive.....from which I conclude that I am at least average. So for me, if things go reasonably well I can get 60 minutes (but not 70) on an AL80 on a typical Cozumel dive.

My actual average dive times (with different dive ops and over the same period) when using AL80's was 57 minutes, and 80 minutes using Steel 120's.

Personally, I wear a 5mil fullsuit in Coz so I don't get cold, I don't struggle with the extra tank size, and I really enjoy the extra dive time that a 120 provides. I'm there to be under water.

Just my humble opinion of course.

Edit: I love Coz diving and would dive with AL40's if that was all that was available....although at that point I would consider doubles.

 

[jd950]

I have reviewed my logs and completed some complex calculations...

My average depth on Cozumel dives is:

about where I want it to be, give or take a few feet;

My typical dive time is:

less than I want it to be (like all dives), but enough to make me smile and feel good;

My average air consumption rate is:

whatever it happens to be at the time.

Based upon the above, and using some very high level math, I calculate my ideal tank size to be:

whatever is available between about 80 and 120 cubic ft.


No offense to anyone who is really into the whole dive time/SAC/tank size issue. If it feels good to get all technical on these things then go for it.

This whole thread got me wondering though. Has anyone calculated the ideal, post-dive, afternoon nap time length? I am wondering if it should be derived from a ratio of dive time to boat time or would be better calculated using ambient air temperature and direction of the ocean breeze???

 

[Mike]

ODid YOU compile dive times for every dive op?

Of course I did, check your email the spread sheet is waiting.

People who dive 80s are telling you that you aren't accurate to say you get "well under 60 minutes" with them.

So what? If 1000 people tell me they dive to 120 minutes on 80s, that still leaves the 10,000 others who haven't chimed in about diving under 60 minutes.

Oh, wait, it's actuaally 9999, because YOU chimed in and said you dive under 60 minutes. Dang it, which is it then? There can't be some people diving more and you diving less, are you lying, are you really diving 100 minutes but didn't want anybody to know?

Oh boy, scubaboard, what a hoot. Almost up to 100 posts arguing that more air is bad, so silly, like I said you all might want to ask for AL 40s on your dives if more air than an AL 80 is bad, then less air most be even betterer!. Pretty soon you'll all be diving just using a Spare Air

 

[drbill]

There isn't anybody in Cozumel routinely doing 90 minute dives with AL 80's on a typical Cozumel dive site & profile, period. Nada. The average dive in Cozumel is well under 60 minutes.

I can't speak for Cozumel as I've never been there but when I was in Anilao (PI) a year ago the average dive was over 90 minutes and many were over two hours, and these were all with 80 cu ft tanks. Of course maximum depths rarely exceeded 70-80 ft.

 

[Mike]

Awesome. I did a 3 hour dive on an under filled AL 80 in the Sahara in 1963, it was in a 2 ft deep kiddie pool. That proves that 90 minute dives are the average in Cozumel.

 

[KenGordon]

I can't speak for Cozumel as I've never been there but when I was in Anilao (PI) a year ago the average dive was over 90 minutes and many were over two hours, and these were all with 80 cu ft tanks. Of course maximum depths rarely exceeded 70-80 ft.

I couldn't do that sitting on my sofa.

There I use 9l/min. So for a 10m average that is 18l/min add 50% for rule of thirds gives 27l/min or about 1cuft/minute, so a al80 would be good for 80 minutes.

Hmmm. How deep are those dives?


Sent from my iPhone using Tapatalk

---------- Post added May 10th, 2014 at 03:54 PM ----------

I can't speak for Cozumel as I've never been there but when I was in Anilao (PI) a year ago the average dive was over 90 minutes and many were over two hours, and these were all with 80 cu ft tanks. Of course maximum depths rarely exceeded 70-80 ft.

I couldn't do that sitting on my sofa.

There I use 9l/min. So for a 10m average that is 18l/min add 50% for rule of thirds gives 27l/min or about 1cuft/minute, so a al80 would be good for 80 minutes.

Hmmm. How deep are those dives?


Sent from my iPhone using Tapatalk

 

[cvchief]

So what? If 1000 people tell me they dive to 120 minutes on 80s, that still leaves the 10,000 others who haven't chimed in about diving under 60 minutes.

Ah, the Nixon "great silent majority" argument! Always a classic.

You seem rattled. You basically called everyone rubes for diving 80s and then are shocked people pushed back.

 

[old gaffer]

I have not really paid that much attention to how long my bottom times have been. I know that at the start of my dive trips I am usually among the first few to have to surface and as the week goes on I am usually among the last to surface. So out of curiosity I checked my log book for my last coz trip and was surprised to find that all my dives were under 60 minutes except Columbia Shallows which was 78 minutes.

I saw one dive to 75 feet that was for only 44 minutes and checked my notes and that was a dive where I had 1500 left and another diver grabbed my fin and signaled he was out of air so I shared air with him until the dive master noticed us and came over and took over air sharing.in the brief amount of time maybe 2 minutes. My tank dropped to 650 with this guy breathing off it. Of course we all ascended to the safety stop. The dive master sharing air and also had this guys wife sticking together as a tight group. Seeing as he was kind of busy I deployed my SMB. So I guess that proved to me I didn't carry it around for nothing!

Gaffer ( Air Hogitus Maximus)