Feedback on recent two-tank and dive limits

[boulderjohn]

If a recreational diver is doing a "no decompression limit" (NDL) dive, he has the perception/expectation that at any time during the dive he is able to go straight to the surface (for whatever reason). On a NDL dive, his computer at the start of the ascent phase should not be telling him that he has to do multiple stops to the surface.

Are there any computers that do this? I am not aware of any. If you have to do decompression stops, you are on a decompression dive, not a NDL dive.

 

[Nick_Radov]

My position on computers using Bhulmann with GF (air, nitrox and oxygen capable) is as entry level technical diving computers. Yes, they can be used by recreational level divers, but with caution.

Your position is outdated. The majority of new recreational dive computers now support some Bühlmann algorithm (typically ZH-L16C or some variant) with gradient factors, and nitrox. For better or worse, this is what recreational divers are buying today.

 

[David Carron]

Your position is outdated. The majority of new recreational dive computers now support some Bühlmann algorithm (typically ZH-L16C or some variant) with gradient factors, and nitrox. For better or worse, this is what recreational divers are buying today.

That (as a rec diver) your computer is using gradient factors, or even ZHL16, internally shouldn't really be a concern. When (as a rec diver) you buy a computer you trust the manufacturer to have chosen a good algorithm and have provided a two or three "conservatism" settings according to their expertise in the matter.

I'm really convinced that allowing (rec) divers to freely configure their gradient factors according to what they may have read on internet is a potential problem.

 

[matt9122]

Agreed, there is no reason to be running GF as a recreational diver. Go with preset conservatism and take a nitrox course and keep it simple.

 

[Mobulai]

Unexpected multiple stops to the surface, which to the inexperienced basic scuba diver may be interpreted as mandatory is not appropriate and may cause anxiety which is not good.

IDK where you’re getting this, or what computer does that
I only know of PDIS on Scubapro computers which makes “suggested” stops tgat can be skipped, and has to be activated by the user — by default it’s off

(P# 28, 78)

https://scubapro.johnsonoutdoors.com/sites/default/files/2022-10/SP_G2_Manual_EN.pdf?srsltid=AfmBOooSPECvmVMuOHc4ccyacCSo2TWSM1f3HGpCJevuZzCYWFM4QfXX

If a similar feature is available on another computer, I’m fairly certain it would follow the same guard clauses

 

[Mobulai]

I'm really convinced that allowing (rec) divers to freely configure their gradient factors according to what they may have read on internet is a potential problem.

Isn’t that (tge worst case scenario) the same as allowing a user to set conservatism to 0 (min)?

I find that argument a bit condescending, kinda like saying “only race drivers are allowed to drive a stick transmission”

 

[David Carron]

Isn’t that (tge worst case scenario) the same as allowing a user to set conservatism to 0 (min)?

Yes. Where I (as a rec diver) have deliberately chosen my dive computer because I trust the manufacturer to have a reasonable definition of what "minimum conservatism" means.

I find that argument a bit condescending, kinda like saying “only race drivers are allowed to drive a stick transmission”

It's more like having a sign on the Scania showroom door saying 'you must have a CDL to drive any of these vehicles on the road' It's not all that hard and you probably could pick it up your own but you don't know what you don't know and odds are somebody's going to get hurt if you try.

 

[Belzelbub]

Agreed, there is no reason to be running GF as a recreational diver. Go with preset conservatism and take a nitrox course and keep it simple.

Why? If we are talking about computers running Buhlmann, which I believe we are (because I'm not aware of any other algorithms using GFs), then these sentences are incompatible with each other.

Perhaps you omitted the word custom from that first sentence. Computers running Buhlmann ZHL-16C may have preset conservatism levels, but they do those via GFs.

 

[Mobulai]

It's more like having a sign on the Scania showroom door saying 'you must have a CDL to drive any of these vehicles on the road' It's not all that hard and you probably could pick it up your own but you don't know what you don't know and odds are somebody's going to get hurt if you try.

I think the point of CDLs is not hurting others not yourself — and that metaphor would be analogue to “don’t go into deco without deco training”

What would reasonable min conservatism equate to in GFHi terms?

I think also sanity limits are set by manufacturers in the non modifiable a/b pressures (now we’re really drifting away from basic or technical scuba into deco theory)

 

[matt9122]

Why? If we are talking about computers running Buhlmann, which I believe we are (because I'm not aware of any other algorithms using GFs), then these sentences are incompatible with each other.

Perhaps you omitted the word custom from that first sentence. Computers running Buhlmann ZHL-16C may have preset conservatism levels, but they do those via GFs.

Correct, recreational divers should not be customizing their GF's.