Warning deep "bounce" dives warning

[Tigerman]

...
Don't plan to go deeper than the number of cubic feet of gas on your back.
...

Now theres something I do on a regular basis (and safely so).
100 ft on an AL80 is no problem whatsoever, Ill run out of NDL before Im running low on gas at 100 ft with an AL80..

That being said, I KNOW what my gas consumption is, Im not just making a random guess that Ill be fine doing it!

 

[redacted]

Going down to 70-80 ft is not really all that different. Going down to 200... 300... 400+ feet is REALLY different.

I'm not a deep diver (130' max), so I'm not the most knowledgable on this, but it's pretty clear that: it's gonna take a while to get to the surface if something bad happens, air eventually becomes toxic, your tissues will load TONS of nitrogen, you'll be narced crazy, etc. And these are just some of the reasons keeping me above my limits until I have the necessary training and equipment to deal with those issues safely.

Sure there may be more considerations the deeper you go and I too have little interest below 130 ft. Unless you are just uninterested in even considering deeper dives and also just want to keep other from considering them also; then work out the parameters and determine the specifics as to why you don't want to do them (and why you feel others also should not).

In my case, I understand it is narcosis considerations that keep me from looking at depths greater than 150 ft. I can figure out how much gas I would want and any deco considerations and they are not my limiting parameters. But I also understand that if I ever put my sights on 200 ft, it is not something I need to mindlessly dismiss.

 

[TMHeimer]

Even if you leave out all the things that can go wrong, the bottom time at 200 feet would be miniscual (thus you "bounce", I guess). I always wondered what the attraction of doing this is--just to say you did it? As a shell collector it would obviously not benefit me at all.

 

[CuNanoTube]

My gas planning is done with a simple spreadsheet, assuming I know what the dives are in advance.
Here is the spreadsheet, uploaded to google docs. Link
I should mention this sheet is almost entirely in metric (except for a psi pressure readout as my pressure gauge is american).

 

[VooDooGasMan]

TM I would say the general answer is to see what it is like, therefore the gas supply was considered, yet the narcosis pulls you in from time and monitoring gauges. That results in speedy ascent and get bent, to slow reaction and gas runs out before you surface.

It is common thought of the new diver, beyond what they have learned in OW, so it is a self guided dive most of the time to new divers.

 

[eponym]

Now there's something I do on a regular basis (and safely so). 100 ft on an AL80 is no problem whatsoever, I'll run out of NDL before I'm running low on gas at 100 ft with an AL80. That being said, I KNOW what my gas consumption is, I'm not just making a random guess that I'll be fine doing it!

Well said. You and I know what our consumption rates are, and what extra safety measures to take. We can plan accordingly.

This is the "new divers" forum. In my experience, rules of thumb are useful for those just beginning, to avoid New-Diver Fatalities Such as This One in San Diego. Rules of thumb are appropriate and useful when one is just beginning to dive. As I said in my first post:

With increasing experience and knowledge one can begin to trade these rules for more detailed and more accurate plans.

 

[Tigerman]

I didnt really get what VGM was trying to say, but thats nothing new..

 

[CuNanoTube]

I didnt really get what VGM was trying to say, but thats nothing new..

I had no idea either, I just kind of ignore his posts as I get a headache trying to figure out what he is saying.

 

[scubadada]

Nice post, Blue.

Here is one gas planning rule of thumb I use in OWD courses:

Don't plan to go deeper than the number of cubic feet of gas on your back.​

And here is one gas management rule of thumb I use in OWD courses:

With a single AL80, it's time to ascend when your tank pressure (in PSI) is current depth times ten, plus 300.​

Both these rules of thumb take into account the need to preserve a portion of "your" backgas for a buddy who runs out. As with all rules of thumb, their derivations are not as important as the ease of remembering and implementing them. And with increasing experience and knowledge one can begin to trade these rules for more detailed and more accurate plans.

The 77 cu ft Al tank is the most common tank used worldwide at diving locations. These 2 rules of thumb are impractical and overly conservative, though "safe". I guess the out is actually using gas planning as appropriate.

Good diving, Craig

 

[ianr33]

The second rule could bring you to the surface with 300 psi which some might feel is a bit aggressive.

The 77 cu ft Al tank is the most common tank used worldwide at diving locations. These 2 rules of thumb are impractical and overly conservative,

So is 10 times depth + 300 aggressive or conservative?

Actually I think it's a mighty fine "rule" Nice way to do multi level dives. If you don't want to surface with 300 psi (understandable!) just do your final ascent from your safety stop with 500 or 600 psi remaining.