Dive Planning Excersize: Check My Work?

[Otter]

Ok you're scaring me. I don't have my OW yet. Is this what I'm supposed to expect when "planning" a dive?

I don't mean to be sarcastic but whenever I hear or read about dive plan what comes to mind is...I plan to dive on Saturday at bla bla bla with bla bla bla.

Wow. Diving sure is heavy if its really like this. Do I have to be the one to make a this kind of dive plan or a DM does one for me?

Thanks in advance for the answers.

Uh oh, me suspects this is going to generate a few replies....(troll?)

 

[H2Andy]

i saw it too... and Deep_6 is a very care-free poster. i would take him at face value.

Deep_6, they are talking about highly specialized diving, beyond the recreational diving most of us do.

you don't have to do it, of course, but if you did, you would want to make sure you
did the figures yourself and not depend on someone else doing them for you.

 

[MikeFerrara]

But since we're talking about mix, doesn't 21/35 give you really short NDLs in the 120 to 150 ft range? Does that effectively limit the utility of rec triox to just the 30/30 mix to 120 ft?

I think...some one correct me if I'm wrong...that GUE teaches rec triox to 120. To get deeper with them I think you need to move on to Tech 1 training.

But...no gas gives much no-stop time at 130 so...
the idea is to avoid the narcosis and save the heavy O2 exposure for decompression.

If you look at the gasses that they use (other than 30/30)
EAN32, 21/35, 18/45, 15/55 and 10/70 you'll see that they can all be made by mixing helium with EAN32. So...as long as you bank 32% this greatly simplifies gas mixing and analyzing.

As far as the deco schedule goes, I don't know what GUE teaches in DIRF about this. My 1 min@60, 2@20, 2@10 schedule was a guess based on what I'd pieced together from what I've learned. I'd appreciate knowing what the rules are for DIR schedules.

Again any one feel free to correct me if I'm wrong but what I've seen taught in a DIRF was 1 minute stops at 30, 20 and 10. Beyond no-stop limits there's a lot more to talk about.

 

[MikeFerrara]

i saw it too... and Deep_6 is a very care-free poster. i would take him at face value.

Deep_6, they are talking about highly specialized diving, beyond the recreational diving most of us do.

you don't have to do it, of course, but if you did, you would want to make sure you
did the figures yourself and not depend on someone else doing them for you.

Every diver, recreational or otherwise, should be able to manage gas in a way that reserves enough gas for both divers to get to the surface.

Whether or not GUE standard gasses must be used would be debated by some, of course but you still need something to breath on the way up if one of you suffers a total gas loss.

 

[H2Andy]

with OW diving, it's usually as simple as calling the dive when one member of the team hits 1000 to 750 psi.

nothing more complicated than that is needed.

with currents, other considerations come into play,
but nothing in the nature of the dive profile that was
presented here and which Deep_6 was looking at.

 

[lamont]

This is why you shouldn't try to learn decompression theory from the internet.

If you have taken a course and are trying to discuss what you have learned in person...then by all means, let's talk. If you are trying to piece together information from all over to come-up with what it means...then you end-up with your examples posted above.

Seriously, this is best learned one on one with an instructor or with someone who is extremely well versed in the calculations who can help you through it step by step.

Well, I'm not trying to learn decompression theory. I'm trying to learn safer dive planning within the NDL limits. I've already been taught one way of how to do that which is "don't exceed 30 fpm and do a mandatory 3 min stop at 15 ft".

I could have reformulated the example that I worked in terms of a 60 or 100 fsw dive which are dives that I'm doing right now anyway. I thought that the 130 fsw dive would shake out more questions though...

 

[cnidae]

I did an exercise to plan a non-penetration wreck dive sitting in 130 fsw of water. I'd appreciate any critiques of this plan that you can give.....

I'm a little confused by you posting this here. Everything you've done in your calculations is wrong if going by GUE's rock bottom.
1. You used a calculator
2. Your using the wrong gas
3. Your stops are wrong
4. Your sacs are wrong
5. Etc......

Not trying to bash you but it would be in your best interest to take a fundamentals class to clear up your misunderstandings on the way GUE does rock bottom.

 

[bwerb]

with OW diving, it's usually as simple as calling the dive when one member of the team hits 1000 to 750 psi.

nothing more complicated than that is needed.

The RB calculations are the math behind where the "surface with 500 psi" or "turn at 1000" comes from.

The problem comes not when people don't understand the math, but instead when people take the turn at 750 to be an absolute. RB for an AL80 at 100 feet is about 700...hmm...perhaps there is more too this then they told me in OW...

This discussion is lighthearted and fun, it is a bit of a look into the greater "why's" of diving.

I totally agree Andy that it isn't complicated at all. If you take a bit of time to understand the theory then you can quickly discover a number of "rules of thumb" which are basic ways of rounding the results of the calculations off to make a determination that "we'll turn at 1000 psi" works.

The problem comes when you start looking at the edges of the envelope. A diver doing the "turn at 750" thing on a 130 foot dive is going to find themselves in an interesting situation on the way up.

My appreciation of the DIR methodology is not that there is anything mysterious or unique in what is being said, it is that the teaching method is great for giving you the why's...which lead you to the rules of thumb instead of the other way around. It allows you to take ANY dive and then understand how to apply it to your dive at hand.


And Lamont...sorry if my post came-off harsh...it wasn't intended to. The problem is that by using an example at the extreme ends of "recreational" diving...other factors come into play which lead the discussion into other areas (gas selection, deco, gas planning, etc.)

 

[H2Andy]

actually... i just realized i am deficient in yet another way:

i have to figure out minimum gas for two people (in cubic feet) for 140 (just in case), 130, and 120, since i've never been that deep, and all my deep dives i do on thirds anyway,
so never get to that situation.

 

[lamont]

I'm a little confused by you posting this here. Everything you've done in your calculations is wrong if going by GUE's rock bottom.
1. You used a calculator
2. Your using the wrong gas
3. Your stops are wrong
4. Your sacs are wrong
5. Etc......

Not trying to bash you but it would be in your best interest to take a fundamentals class to clear up your misunderstandings on the way GUE does rock bottom.

Well,

1. yes, "learn the shape of the curve" -- but you've got to start somewhere in pushing the numbers through.

2. yup, understood -- i even made a note of that before anyone pointed it out to me -- but the mathematical techniques used are the same as would be used in dive on EAN to 80 fsw. seems i made a poor choice in picking this as an example because everyone has gotten distracted by the EAN vs. trimix debate.

3. i'd love to be more enlightened about what stops to pick. I did 2@10 and 2@20 because that's how the DIR guys I've dived with did stops from shallower depths -- I then tacked on a 1 min @ 1/2 max for a 'deep stop' (remember we're NDL here, so this is just added conservatism).

4. i don't think my SACs are wrong, I think I just wasn't clear in how I was doing the math -- I figured for 0.6 SAC and then multiplied by 2.0/0.6 -- you get the same answer.

and yup, me and a DIRF class needs to happen, but I've got these questions today...