Question When do we speak of technical diving ?

[rx7diver]

I never considered the aspect that you guys were staying within the NDLs. ...

My post is suggesting that if you exceed NDL on either of the dives, you need to be sure to include (backgas) gas consumed during decompression when you compare expected air consumption.

rx7diver

 

[L13]

Careful: Navy tables give the NDL of a 100 fsw dive is 25 min (rather than 30 min), followed by a direct ascent to the surface using a 60 fpm ascent rate. And the NDL of a 70 fsw dive is 50 min.

Okay. These are the two dives you might compare with respect to expected air consumption.

ETA: I just read the posts that follow @Capt Jim Wyatt's. So, suppose, instead, the dives to 100 fsw and 70 fsw will be done using EAN32 (rather than air). It's straightforward to compute the two END's here, and then compute and compare the associated expected air consumptions of the two NDL EAN32 dives.

rx7diver

Physics says that with a constant RMV and any EAN, a deeper NDL dive will use less than a shallower NDL dive.

Given Min Gas, or going into Deco, all of that changes(I haven't thought through exactly how, but pretty sure total with Min Gas is higher for deeper).

EDIT:
typo, less above as typed more

 

[rx7diver]

Physics says that with a constant RMV and any EAN, a deeper NDL dive will use more than a shallower NDL dive.

Given Min Gas, or going into Deco, all of that changes(I haven't thought through exactly how, but pretty sure total with Min Gas is higher for deeper).

@L13,

I am not sure I am understanding your post. The two dives on air have NDL's of 25 min and 50 min, respectively.

And the two dives on EAN32 have NDL's of 30 min and 60 min (again using Navy tables, and trusting my very quick hand calculations).

Does this help?

rx7diver

 

[scubadada]

Careful: Navy tables give the NDL of a 100 fsw dive is 25 min (rather than 30 min), followed by a direct ascent to the surface using a 60 fpm ascent rate. And the NDL of a 70 fsw dive is 50 min.

Hi @rx7diver

Nobody uses Navy tables, I learned them in 1970 and quit using them when the PADI RDP came out in 1988. I dived the DSAT computer deco algorithm starting in 2002 and added Buhlmann ZH-L16C with GF in 2015

 

[L13]

@L13,

I am not sure I am understanding your post. The two dives on air have NDL's of 25 min and 50 min, respectively.

And the two dives on EAN32 have NDL's of 30 min and 60 min (again using Navy tables, and trusting my very quick hand calculations).

Does this help?

rx7diver

In both the air and EAN32 cases, more gas will be comsumed on a shallow NDL dive that a deep NDL dive.

This applies from EAN16 (minimum viable on the surface) to EAN45(hard to get an NDL at MOD depths beyond this). The numbers will be different, but the shallower NDL dive in a deep/shallow pair with the same EANXX will always be the one consuming more gas.

(excluding min gas requirements, and obviously not deco)

EDIT
@rx7diver, there was a typo in the original version of the post you quoted. Does that clear up your misunderstanding?

 

[johndiver999]

Physics says that with a constant RMV and any EAN, a deeper NDL dive will use more than a shallower NDL dive.

Given Min Gas, or going into Deco, all of that changes(I haven't thought through exactly how, but pretty sure total with Min Gas is higher for deeper).

Is that a typo?

 

[L13]

Is that a typo?

Yes, deeper is less gas. For all NDL dives.

 

[rx7diver]

Hi @rx7diver

Nobody uses Navy tables, I learned them in 1970 and quit using them when the PADI RDP came out in 1988. I dived the DSAT computer deco algorithm starting in 2002 and added Buhlmann ZH-L16C with GF in 2015

Navy tables are very convenient (for me) for doing some quick recreational dive planning--especially since I committed the "magic numbers"--you know, 60 for 60, 70 for 50, 80 for 40, etc.--to memory in the 1980's when I did my open water training.

ETA: In addition, the submersible tables that accompany me on my dives are Navy Tables-based. Great for surface interval, repetitive dive computations.

rx7diver

 

[Blackcrusader]

Maybe you should take a look at one then, maybe you wouldn't be telling people that decompression diving is recreational diving because it really isn't when you look at the added risks that come with it.

And also, nice humble brag I guess?
Not sure what anything after your first sentence had to do with this topic at all.

Maybe that's why it was called sports diving? Deco dives fall within recreational diving you just need some extra training for it. In my opinion.

 

[Angelo Farina]

I have a question about technical diving.
When do you start talking about technical diving?
I come to the question because I am currently making the SSI Deco Diver. After completion, you are allowed to do dives with up to 15 minutes deco stops. Is this already technical diving?

Does anyone know about the course, if so, what do you think of it?

Here in EU that is NOT technical diving. My fully recreational Cmas *** certification allows me to dive to a max depth of 50m in air, with deco on air.
Training was done using twin tanks and two fully independent regs on two separate valves.
Here the boundary of "tech" begins below 50m (albeit in France they have "advanced recreational" in deep air down to 60m).
Tech starts when you use different gas mixes at different depths (for example air below 36 meters and Nitrox above and for deco), requiring the usage of a Tech diving computer which allows for gas switches.
Deco stops per se is not tech. It becomes tech when done using a special hyper-oxygenated "deco mix", which again requires special tables or a "tech" computer.
However also here there are different boundaries in different countries.
In my opinion the best progression between rec and tech is from BSAC (UK) agency.