Maximizing bottom time safely

[Bazzathemammoth]

I recently got a peregrine and I’ve been enjoying all the extra information that it’s showing me. I was thinking that I could use the info to maximise my ndl bottom time while managing risk. I’m eventually going to move to tech diving and have recently bought a Twinset and i have done some training on it.

So I’m thinking that I have two options to maximise my down time and manage risk.

Option one is to set conservatism to minimum (gf high 95), and then stay on my safety stop until surface gf is 75, or I decide to go up. I won’t know my tts with this option.

Option two is to set conservatism to max (35/75 I think), ensure that my surface gf doesn’t go above 95 and that my tts is within my available gas. This is technically a deco dive, but only because of conservatism settings.

Option one doesn’t violate any rules as the computer shows me as within ndl at all times, but option two gives me more information and I think could be a more reliable way to achieve my goal. Option two also gives me some practice in following a proper deco profile.

What are your thoughts?

Please note that this thread is a dogma free zone. I’m keen to hear opinions backed by logic or personal experience , but please refrain from saying I’m going to die because this isn’t what is being taught.

 

[100days-a-year]

1. You don't understand NDL
2. You don't understand GFz
3. I suggest reading up on both.
4. You wont die but there is no benefit either.

 

[Bazzathemammoth]

1. You don't understand NDL
2. You don't understand GFz
3. I suggest reading up on both.
4. You wont die but there is no benefit either.

Can you tell me what I’m missing, or point me to some reading that could explain it?

 

[tomfcrist]

I would suggest taking AN/DP at your earliest convenience. You will learn about NDL/GFs and get certified for deco dives….bottomtime becomes limited by gas, and willingness to do deco. Problem solved.

 

[Bazzathemammoth]

That’s the plan, but I’m time and money limited so it’s not going to be as soon as I would like. Damn kids need food and clothes and all that, and I have to work to pay for it all

 

[tomfcrist]

That’s the plan, but I’m time and money limited so it’s not going to be as soon as I would like. Damn kids need food and clothes and all that, and I have to work to pay for it all

They don’t like ramen?

 

[tursiops]

Your Peregrine also allows you to set any GFs you want; you are not restricted to max, medium, and low conservatism. In fact, those are terrible choices (GF-Lo is too small for most folks today) in many cases, especially if you go into deco (which you will if you are using GF-HI 75 and trying to get more bottom time. Play with your Plan mode, and see what your BT is -- within NDL -- for various GF-Hi choices. Your option 2 may produce a deco requirement....it is a real requirement tht you need to observe....to be consistent with how you have set the computer.
The biggest problem I see with both your strategies is that you do not know what your gas needs are. Sure, you have twins; people run out of gas with twins, too. You are not trained yet for deco, so pick a strategy that allows you to stay within NDL.
Using something like GF 80/95 will maximize your BT within NDL; spending as much time as you have gas for at your SS will minimize your risk.
Avoid your Option 2 until trained; it is playing with fire.
Get something like MultiDeco and see what you can achieve.

By the way, what is a dogma-free-thread? Good luck with that.

 

[Bazzathemammoth]

Thanks for that. If I allow 1 bar per min per ata then that’s as much gas as I could need for anything but full on hyperventilation. My working Rmv is 18l/m in cold water and 1 bar/ata is 24l/m with my 2x12l twinset.

 

[Endler's]

This is the most current Scubaboard link, to answer your question?:
Using GF99 and SurGF
It points you to this article by Andy Davis:
Shearwater Dive Computer Settings: Become A Power User!

 

[lowwall]

I recently got a peregrine and I’ve been enjoying all the extra information that it’s showing me. I was thinking that I could use the info to maximise my ndl bottom time while managing risk. I’m eventually going to move to tech diving and have recently bought a Twinset and i have done some training on it.

So I’m thinking that I have two options to maximise my down time and manage risk.

Option one is to set conservatism to minimum (gf high 95), and then stay on my safety stop until surface gf is 75, or I decide to go up. I won’t know my tts with this option.

Option two is to set conservatism to max (35/75 I think), ensure that my surface gf doesn’t go above 95 and that my tts is within my available gas. This is technically a deco dive, but only because of conservatism settings.

Option one doesn’t violate any rules as the computer shows me as within ndl at all times, but option two gives me more information and I think could be a more reliable way to achieve my goal. Option two also gives me some practice in following a proper deco profile.

Your options are completely different things.

Option 1 is acceptable given your current training level. Set the gradient factors to whatever you think is your appropriate risk level (or just accept the least conservative of the rec options), ride that NDL right to 1, ascend and extend your time shallow until you are happy with the SurfGF number and then very slowly surface. You obviously need to keep an eye on your remaining gas while all this is going on

OTOH, if I understand it correctly your Option 2 is not a good idea. Let's say you leave the bottom with your SurfGF reading of 95. What do you think is going to happen to it while you are waiting out the deep deco stops that a GF Lo of 35 is likely going to require?

The answer is that it's going to keep climbing. Likely to the point where you have turned your pretend deco dive into an actual deco dive. A deco dive that you are not trained for and probably without the gas reserves you would have on a planned deco dive.