Have ScubaBoard's SurfGF threads changed how you plan to dive?

[rsingler]

As y'all have demonstrated, the survey was definitely imperfect. Still, if we can get our members to give serious thought to the potential value of a markedly slowed final ascent, and the added value of extending the safety stop now that we have a parameter like SurfGF to look at, I think we will have done the diving community a service.

It's by slow evolutionary changes like this that we improve our sport, whether I'm right or not on this particular issue.

 

[100days-a-year]

Nope, but it is always interesting to see why other people do what they do. I would have to identify a problem with my ascent rate/SS before I went looking for a solution.

 

[Divectionist]

I've always done a really slow final ascent and if there's Nitrox I'll have it, no matter how shallow.

 

[markmud]

In the last two months we have had two threads with surveys exploring the relatively new metrics of GF99/GFNow, and SurfGF, which have together garnered more than 5,000 hits.
What's your SurfGF and how does it compare to your (Rec) GFHi?

Recreational Ascent Rate in the last 15 feet

We're wondering if all the discussion really might make a difference to your diving?

Hi rsingler,

I have performed slow ascents from SS since reading several books more than a decade ago. Scubaboard has confirmed my practice.

Why rush to end your dive? I enjoy the time at 10' as there are lots of things to look at from that depth. The 10 foot perspective is a different view. And, continued in-water decompression can't hurt.

Thanks for the thread.

markm

 

[Centrals]

I am sticking with my routine which has been trouble FREE, rec or decompressed dive, over last 23 yrs.
New trick to an old dog!!!!

Of course, love to know/learn/see other opinions.

 

[hedonist222]

how slow is slow ascents?

Shearwater (because I use one) defines an optimal ascent rate as 9 meters per minute

there have been Shearwater articles where they suggest sticking to 9 mpm as the algorithm of off-gassing is based on that ascent rate

 

[rsingler]

Now that I'm deco diving, my new standard ascent rates are:
30-60fpm from 200 to 60 ft to reduce ongassing
30fpm from 60 to 10 feet per my computer
10fpm max from 10 feet to the sfc. as my GF99 blooms.

When you watch the theoretical changes in your compartments on your Shearwater in those last 10 feet, especially if you've loaded your slower compartments by deco diving, it's hard to rationalize 30fpm. I'm willing to bet it doesn't hurt me, and maybe one day data will show that it helps. The cost? An extra 2 minutes in the surge near the surface if its a rough day. And if you're on 100%O2 at 20ft? Just do an extra couple of minutes there and ascend as slowly as conditions permit.

 

[hedonist222]

When you watch the theoretical changes in your compartments on your Shearwater in those last 10 feet, especially if you've loaded your slower compartments by deco diving, it's hard to rationalize 30fpm. I'm willing to bet it doesn't hurt me, and maybe one day data will show that it helps.

Are you referring to CNS% ?

If so, I checked mine from deepish dives (up to 90 feet).
I even checked dives two and three from the same day to 90 feet dives (with an hour of surface interval between)
The percentage change from bottom to starting to ascend was only an increase of 1% in the majority of dives I checked.

I'm not insinuating that you are wrong, maybe I'm checking the wrong statistics?

As an example: CNS% was 14% at the end of an NDL dive down to 28 meters for 38 minutes, then an ascent to 6 meters that took about 3 minutes, followed by a 3 minute safety stop.
CNS% increased to 15%.

My ascent rate from 27 meters to 6 meters was 9 meters per minute.

This was the case for a handful of deep dives that I skimmed through.

 

[rsingler]

No, not CNS, but SurGF GF99
Look at the red line in your dive log with "GF" checked. You'll see that the percentage oversaturation in your leading compartment, which is near zero for most of your recreational dive, becomes visible on ascent, and really blooms in the last ten feet.
I'll find a dive and post a pic.

 

[hedonist222]

No, not CNS, but SurGF.
Look at the red line in your dive log with "GF" checked. You'll see that the percentage oversaturation in your leading compartment, which is near zero for most of your recreational dive, becomes visible on ascent, and really blooms in the list ten feet.
I'll find a dive and post a pic.

The GF icon on the below?
Thats definitely not SurfGF. Thats GF99.

Because my SurfGF increases the longer and deeper I go.
I think you meant GF99.

Yes, its on-gassing but then exponentially rises as I ascent.
But isn't it supposed to?