Missed deco stop on Perdix. Need help understanding dive log

[SaltyWombat]

My Perdix is in high conservatism mode, GF 35/75. I did not complete my deco stop at 10 feet. This was the first time I went past NDL.

Below is my my dive profile. I don't understand the deco and GF data.

1. Does the height of the red deco information correspond to the deco stop depth of 10 feet?
2. My ending GF was 77%. What exactly does this mean?
3. 10 foot deco stops are hard to hold in a drysuit. If I want a deeper stop, like 15-20 feet, should I switch the GF away from 35/75?
   
4. How close to being in trouble was I?

I felt completely fine after the dive. Gas was EAN 32.

 

[rsingler]

1. Yes. That was the depth and duration of your recommended deco stop. Stopping at 15 instead of 10 would have worked. It just would have taken a little longer to complete offgassing to a GF Hi of 75%. So the answer to question #3 is no. Don't change your GF's. Just stop where you want to stop if it gets rough, and wait until your computer clears deco.
2. If 100% is Buhlmann's max tolerable overpressure in your leading compartment, then you finished 77% of the way there. Diving to 100% is generally considered overly aggressive, so we add padding. 77% is perfectly adequate, according to many tech divers. Finishing at 77% vs 75% in your leading compartment is clinically insignificant, until the day it isn't. Me, I dive XX/70. Over the past 15 years, average GF Hi has been dropping a bit, if you survey a wide range of tech divers.
3. See #1 above
4. Not very. Many guys (not me) dive GF's more aggressive than yours.

But where I take issue is with your acceptance that GF 35/75 is max conservative. You are correct, that's what Shearwater calls it, but that's a legacy bias. If I go into more detail, I will open Pandora's box, and this thread will spin out of control.
Let's just say that the "conservative" argument lies not only with GF Hi, but also with GF Lo. A low GF Lo causes you to make your first stop deeper in the water (which didn't really occur with your dive of only one stop). For bigger dives where a low GF Lo is used, deeper first stops are argued about, because for some compartments, you will still be ONgassing while your leading compartment is offgassing.
There is scientific data that begins to suggest that the bad effects outweigh the supposed benefit of the deeper stop.
And that's as far as I'll venture here, because it doesn't apply to your dive.

My 2 cents? Set your GF to Custom, and use GF50/70. Then if you inadvertently go past your NDL, just follow your computer.
The length of your required deco stop suggests that this was not an inadvertent decompression dive. Doing that without specific training is not a great idea.

 

[Miyaru]

Those lines are just an indication of a decompression model. There is much more to decompression than just following computer instructions.

The setting on your computer is to surface with 75% of the Bühlman maximum super saturation. Or in other words, 25% safety margin. You surfaced with only 23% safety margin. The purpose of the stop is to give your body time to off gas before going into that safety margin.

Your 3rd question will be answered by me and others with: get training!
That goes for understanding decompression models (theory) and for holding a stop effortlessly at 3m/10ft in a drysuit.

How close were you to being in trouble?
On this dive: obviously not that much. But now that you got away with it, it might give you confidence that you can get away with it a 2nd time. Did you have enough gas to complete the suggested stop(s)? The profile doesn't show that.

You're pushing the limits while you are not 100% in control. The best solution is to work on being 100% in control.
Find an instructor who can teach you 100% control, and he will teach you the decompression model and how to determine your own personal Gradient Factor settings.
35/75 is not simply conservative.

 

[Raphus]

Nothing more to add.

Were you out of gas, or why didnt you do the deco stop?
And why didnt you do a safety stop?

A safety stop would probably lower your gf enough to clear your deco aswell.

On such a "deep" and long dive there should always be a good long safety stop, even when no deco.

 

[Searcaigh]

I will just emphasize the point get training (before you become a statistic).

 

[Capt Jim Wyatt]

I will just emphasize the point get training (before you become a statistic).

Yes, do get training.

 

[rhwestfall]

10 foot deco stops are hard to hold in a drysuit. If I want a deeper stop, like 15-20 feet, should I switch the GF away from 35/75?

You can set your last stop to 15' (or 20') but as said above, it will take longer to clear.

Repeating, you really need to gain some knowledge in DECO procedures..

You also need to be more attentive to dive time/depth in general. Why did you stay down (exceed NDL) so long?

 

[rhwestfall]

I guess I need to say a little more.....

Preparing for this dive, what was the plan? What was the planned depth and time? The computer has a planning mode, what did it provide you? You are not trained in DECO, so what caused a deviation to go into DECO this far? It seems you didn't do any of that, but just strapped on the magic gizmo, and didn't follow it either...

How often on the dive did you identify depth/time/NDL/air?

This is concerning.....

On top of advanced training for DECO procedures, I think you need to revisit basic dive planning...

 

[DiveTucson]

Here is a pretty simple article on gradient factors:

Gradient Factors - Dive Rite

That being said based on the questions you are asking I would strongly recommend getting the correct training before continuing to dive in this manner. There is a pretty small margin of error for mistakes and a lack of understanding in deco diving.

 

[Outbound]

I don't want to jump on your case, but why is a 10' stop difficult to hold in a drysuit? It shouldn't be. You should be able to remain neutrally buoyant at any point in the water column. Ninety percent of my diving is done in a drysuit, and I frequently stop in 3-4' of water with no problem just to check out the fresh water jellyfish or other things in the water.