Computerless Multi-Level dives

[Charlie99]

newdiverAZ once bubbled...
Does anyone now what the tissue haltimes are corresponding to the compartment #'s. {GAP}

Look at the Understanding M-values article on the gap website. GAP 1.2 uses those compartment numbers/halftimes/M0 values, except that what is labeled #1 onscreen is the 5 minute HT compartment 1b. Another possible point of confusion is that, when you start a new profile, the compartments all show 0% on the screen. Do a 0' 0 minute dive, and you will have a bunch of numbers. These are the initial loadings for saturation at your selected altitude (normally sea level). Using 2' for inspired air H20 pressure, and 79% inert gas, the starting compartment loadings are about 24.5fsw.

It may be that you were expected the compartments to move from zero up to equilibrium at the new dive depth. In reality, they are moving from those numbers you see after a 0' 0 minute dive.

Hope that helps,

Charlie

 

[cornfed]

Diver0001 once bubbled...

I follow what you're saying but I think we disagree about how much control you have. I just don't think you can plan for everthing. I mean, Berman screwed it up....Exley screwed it up....I can just about guarantee that they were both better divers than you or me and they both ran out of air and now they're dead. Procedure fault? Judgement fault? Planning mistake? Equipment problem? Doesn't matter much.

If you run out of air and drown then you don't have to worry about getting bent.

I realize I'm jumping in late but you seem rather beligerent, Diver0001. We're not talking about dropping down to almost 900ft using a mix with an END of almost 275ft. We're not talking about solo diving in heavily restricted virgin cave. We're talking about your standard weekend dive. We're talking about looking a some fish, maybe a rusty old boat.

If something happens while you're under water and you run out of gas it doesn't matter if you're using a computer or trying to shape your profile you still can't breath water.

Cornfed

 

[Knavey]

Freeman once bubbled...
I made a post earlier in this thread with an example multi level dive and asked if it was possible along with the explanation as to how to figure out using just a PADI RDP table. So far no responses Anyone up for exaplantion on this one? I have already ordered a dive computer but still want to be able to calculate multi-level dives on my own ( plan your dive-dive your plan).

Example dive: 90ft/15min, 60ft/15min, 40 ft/15min, remaining time at 15 ft?

Thanks to those who respond to this

Broght the wheel to work tonight just to try this example!

90ft/15 mins = Press Group I, H definately only touches on my wheel

No surf int, 60ft/15 mins, Press Group Q, P only touches

No surf int, 40ft/15 mins, Press Group T

NDL at 15 feet (35 foot ring on wheel) 93 minutes. Interesting that there is a difference in a couple of the people who calculated this.

I did "check the calibration" of my wheel before hand with the dots.

 

[Uncle Pug]

Freeman once bubbled...
Example dive: 90ft/15min, 60ft/15min, 40 ft/15min, remaining time at 15 ft?

....how much gas do you have left?

 

[newdiverAZ]

assuming an rmv of .65 on an Al 80 you would run out of air on this profile 41 mins into the dive, after 11 mins @ 40'.

 

[newdiverAZ]

To do the complete profile ie. 90' for 15, 60' for 15, 40' for 15, then the 93 min ndl they are speaking of would take 170 cu. ft of gas. assuming an rmv of .65. Not saying that I would do this profile but how would you figure the extra gas needed for bailout and your buddy. My guess would be you need an additional 20 cu. ft of gas for this.

 

[Uncle Pug]

newdiverAZ once bubbled...
assuming an rmv of .65 on an Al 80 you would run out of air on this profile 41 mins into the dive, after 11 mins @ 40'.

It doesn't matter what your tables, computers or wheels say... if you don't have the gas you are breathin' water.

 

[diverbrian]

Sounds like the reason that I use my dual 100's and 40 cu. foot deco bottle on so many deep dives (Even when deco is not required, I will use it at safety stops.). Running out of gas underwater makes breathing a little rough.

Even in recreational gear, my primary tank size is a 120 and I have a little less than a .6 cu. ft/min RMV with that. I have this thing about living and when I am diving 90-130 ft. wrecks, I will take all of the gas that I can get. If I don't need it, my buddy may need it.

This allows my computers to keep me underwater as long as they want (ie. be conservative) without risk to myself. Also, the only way that I have found to plan multi-level dives is to use planning software that I have on my laptop and desktop to plan the dives and then follow that profile. That seems to be effective.

 

[Charlie99]

newdiverAZ once bubbled...
assuming an rmv of .65 on an Al 80 you would run out of air on this profile 41 mins into the dive, after 11 mins @ 40'.

15@90', 15@60', 15@40' is a very reasonable dive with 0.5cfm. With typical drift dive SAC below 0.4, this is a common sort of dive for me. Just watch your air and go shallow earlier if running low.

 

[Uncle Pug]

Charlie99 once bubbled...
15@90', 15@60', 15@40' is a very reasonable dive with 0.5cfm. With typical drift dive SAC below 0.4, this is a common sort of dive for me. Just watch your air and go shallow earlier if running low.

But that's OK... new diver got it. Gas management comes first.

New diver you were wise to make the plan with the SAC you did.

When we plan our dives I figure my gas consumption at .66 for the working portion and .5 for the resting portion. However most of the time my actual SAC is somewhere around .44~.46 for the working portion.

Last Friday chasing crabs it was .58

If you plan for your best SAC and run into a problem you have no margin.