Modern research/thoughts on Ascent Rates

[boriss]

Uhhhh yeah. Agreed. Just for fun, I've ran stupid dive profiles on subsurface. One was a deco dive (60 ft, 85 mins) using GFs of 75/95. Gave me a 43 minute stop at 10 feet- the only deco stop in the plan. If I set the last stop at 20 feet, it's an 80 minute stop. Neither sound appealing to me. Having the majority of your deco being at a much shallower depth just doesn't seem like a good idea.

I wasn't posting advice? all I said was for fun I ran GFs on subsurface to see what deco would come up.
ETA I didnt put nitrox in, it was just air

You actually do post opinions, in a Technical Diving forum (and very technical threads at that), which you aren't certified/qualified for yet and can be construed as advice by others, who don't know your qualifications.

Here's an example, where you say "Suunto is dumb," without understanding any of the theory, nor why the computer does what it does: Riding deco ceiling on ascent

In the post above you state "Having the majority of your deco being at a much shallower depth just doesn't seem like a good idea." That's reality, however: the majority of the deco is always at a shallower depth. The GF chosen is risky at best, it's a recipe to get bent!

Sorry if I'm sounding like a dick, but I take safety very seriously (thus this thread) and it's concerning that someone may read these opinions as advice. Instead, let's fix some of the above assumptions and break down that "stupid dive."

First, let's start by selecting a proper gas. 60ft = ~3ATA. 1.4 / 3 = 47%. A non-technical, but Nitrox certified, diver would be limited to <40% Nitrox and more likely EAN36, which is commonly banked.

Next, we need to calculate the Equivalent Air Depth (EAD) of EAN36.
EAD = 0.64 / 0.79 * (60 + 33)ft - 33ft = 42ft.

Now, here's a challenge for you: go look at your NDL dive tables and see if the above scenario (42ft @ 85 minutes) is a decompression dive.

Please continue to dive, read, learn, take more classes, etc. I'm sure given your passion you'll be up to speed in no time and I hope you join the rest of us on technical dives.

P.S. I recently went on an Advanced/Tech trip and one of the divers, needing a buddy was Advanced Open Water and Nitrox certified. He said a lot of things on the boat which were questionable, like not knowing which gas to use for a 140+ft dive (he had an AL80 of 24% and 31%). He didn't know he had to launch an SMB from under water (as to be seen by boats), and several other "warning signs." A lot of basics were just missing.

He wasn't buddied up with me, so I sort of ignored a lot of these things and was paying attention to my own gear, mental state, pre-dive checks and so on.

Our tech dive ended up being scrapped and we were instead put on an "advanced" dive to 110ft (Captain Dan Wreck). After an hour deco dive, I get back on board to find out this guy had an OOA emergency! At like 80ft!! Thankfully his buddy was a really advanced diver and she was able to get him on her octo and get him to the surface slowly and safely.

So my post isn't theoretical.... I see a lot of problems on an almost weekly basis and I don't want people to get hurt.

 

[kaylee_ann]

You actually do post opinions, in a Technical Diving forum (and very technical threads at that), which you aren't certified/qualified for yet and can be construed as advice by others, who don't know your qualifications.

Here's an example, where you say "Suunto is dumb," without understanding any of the theory, nor why the computer does what it does: Riding deco ceiling on ascent

In the post above you state "Having the majority of your deco being at a much shallower depth just doesn't seem like a good idea." That's reality, however: the majority of the deco is always at a shallower depth. The GF chosen is risky at best, it's a recipe to get bent!

Sorry if I'm sounding like a dick, but I take safety very seriously (thus this thread) and it's concerning that someone may read these opinions as advice. Instead, let's fix some of the above assumptions and break down that "stupid dive."

First, let's start by selecting a proper gas. 60ft = ~3ATA. 1.4 / 3 = 47%. A non-technical, but Nitrox certified, diver would be limited to <40% Nitrox and more likely EAN36, which is commonly banked.

Next, we need to calculate the Equivalent Air Depth (EAD) of EAN36.
EAD = 0.64 / 0.79 * (60 + 33)ft - 33ft = 42ft.

Now, here's a challenge for you: go look at your NDL dive tables and see if the above scenario (42ft @ 85 minutes) is a decompression dive.

Please continue to dive, read, learn, take more classes, etc. I'm sure given your passion you'll be up to speed in no time and I hope you join the rest of us on technical dives.

Yeah, I can kinda see your first point, so I added in my signature (afterward) that none of what I say should be taken as advice.
I actually read about gradient factors and deco theory all the time lol. Not that I’m an expert or know it all by any means, just that I know some stuff (not that I’m necessarily right, here). With the suunto post, I guess I didn’t actually explain the reasoning behind thinking that. Kind of inferred it with my guess of why the deco is different, but wasn’t clear.
As for shallow deco, I meant if there’s going to be around 40 minutes of deco, it seemed weird to me for it to be all at 10 feet. Seemed weird=my opinion, never said it was definitely wrong. Afterwards though, realized it was because I had more dives before it on subsurface as another poster mentioned.
eta- yeah I think 85 minutes for 42 feet would be a decompression stop dive. but if I look at the SDI tables, it doesn't seem to be. but I think I suck at reading tables.

 

[grantctobin]

Yeah, I can kinda see your first point, so I added in my signature (afterward) that none of what I say should be taken as advice.
I actually read about gradient factors and deco theory all the time lol. Not that I’m an expert or know it all by any means, just that I know some stuff (not that I’m necessarily right, here). With the suunto post, I guess I didn’t actually explain the reasoning behind thinking that. Kind of inferred it with my guess of why the deco is different, but wasn’t clear.
As for shallow deco, I meant if there’s going to be around 40 minutes of deco, it seemed weird to me for it to be all at 10 feet. Seemed weird=my opinion, never said it was definitely wrong. Afterwards though, realized it was because I had more dives before it on subsurface as another poster mentioned.
eta- yeah I think 85 minutes for 42 feet would be a decompression stop dive. but if I look at the SDI tables, it doesn't seem to be. but I think I suck at reading tables.

I think you need to take a step back and get some formal instruction. The difficulty on the Internet is that everyone is just a name and someone could interpret your “non-advise” written nincompoopery as fact and be led the wrong way.

 

[lowviz]

The difficulty on the Internet is that everyone is just a name and someone could interpret your “non-advise” written nincompoopery as fact and be led the wrong way.

BTW, she spelled advice correctly. I realize that this is the technical forum and gloves are off here, but nincompoopery is a tad severe IMHO.

 

[kaylee_ann]

I think you need to take a step back and get some formal instruction. The difficulty on the Internet is that everyone is just a name and someone could interpret your “non-advise” written nincompoopery as fact and be led the wrong way.

Well, I would like to do that, except I’m not able to dive at the moment due to medical reasons. So looks like my stupid research and nincompoopery will have to do for the near future.
By the way, I’m allowed to comment wherever I want unless the moderators tell me otherwise.
I literally addressed your whole point in the post you quoted. You’re just being redundant now.

 

[TrimixToo]

For lots of deep-ish (around 200') dives, I've motored up to 150' quickly, then slowed to somewhere between 30 and 60 FPM to the first stop, then slowed to 30 FPM or less between stops. From the last stop (20' in salt, 10' in still fresh) I waft upwards slowly, taking my time, probably 5 FPM or less, still breathing O2. At the surface I stay on O2 until I need to get out of the water. This is, of course, anecdotal evidence and it's possible that I'm more cautious than need be after reaching the first stop and less cautious than I should be before I get there. I have nothing like the experience of some here but so far, so good.

This is NOT a recommendation, nor what the agencies or software I use recommends.

I'd love to know what Simon Mitchell might recommend here.

 

[Akimbo]

I think you need to take a step back and get some formal instruction. The difficulty on the Internet is that everyone is just a name and someone could interpret your “non-advise” written nincompoopery as fact and be led the wrong way.

Seriously? When was the last time dangerous nincompoopery went unchallenged on the Internet, let alone ScubaBoard? The diving world won't implode from a few imprecise posts.

We were all newbies trying to learn at one point.

 

[Nick_Radov]

As a practical matter for ocean technical diving, ascent rate coming off the bottom and moving up to your first deco stop is likely to be limited by how fast you can wind up the SMB spool. With thick gloves and cold hands, you don't want to risk fumbling it by trying to go too fast.

 

[Wibble]

As a practical matter for ocean technical diving, ascent rate coming off the bottom and moving up to your first deco stop is likely to be limited by how fast you can wind up the large SMB spool reel. With thick gloves and cold hands, you don't want to risk fumbling it by trying to go too fast.

FIFY

Large reels wind up much faster than itty bitty spools or reels

 

[Nick_Radov]

FIFY

Large reels wind up much faster than itty bitty spools or reels

Sure but then you have to carry the large reel through the entire dive, so it's usually not worth the hassle. Plus when you deploy the SMB, large reels can occasionally bind up due to sand or something getting between the moving parts. So it can work but usually it's better to only use a reel if you're towing a surface float through the entire dive and use a simple spool for launching an SMB from depth.