Single bottle dives and choice of deco gas

[ucfdiver]

RD *sucks* for long shallow dives. The rules you've read simply require way too much deco. For long 100ft 32%/100% o2 dives I've found ratio deco runs a higher risk of making me look like a starving child in Africa than getting bent.

How long of run times are you talking? Less than 130, I would nearly always choose o2/backgas, unless rock bottom forces me to use 50%

 

[gsk3]

RD *sucks* for long shallow dives. The rules you've read simply require way too much deco. For long 100ft 32%/100% o2 dives I've found ratio deco runs a higher risk of making me look like a starving child in Africa than getting bent.

How long of run times are you talking? Less than 130, I would nearly always choose o2/backgas, unless rock bottom forces me to use 50%

T1 limits, so 30 mins deco.

 

[limeyx]

RD *sucks* for long shallow dives. QUOTE]

Definitely agree here. for long deco dives 80-110 or so feet, then a 1:1 time over is definitely overkill.

Just the same as I have seen even VPM+2 (In my opinion) underestimate deco for shorter deep dives (it seems to approach a cliff sometimes where it goes from quite far under to over with rather small changes in BT)

 

[gsk3]

Just the same as I have seen even VPM+2 (In my opinion) underestimate deco for shorter deep dives (it seems to approach a cliff sometimes where it goes from quite far under to over with rather small changes in BT)

Out of curiosity, how deep is deep and how short is short?

 

[PfcAJ]

Take a look at 80ft for 160-200mins (30/30, o2 deco) and compare buhlmann to vpm. Substantial differences between the two.

All these models break down and get nutty at some point.

 

[gsk3]

Take a look at 80ft for 160-200mins (30/30, o2 deco) and compare buhlmann to vpm. Substantial differences between the two.

All these models break down and get nutty at some point.

That's kind of funny. VPM says it's pushing the limits of T1. Buhlmann says it's pushing the limits of T2!

 

[limeyx]

Out of curiosity, how deep is deep and how short is short?

What we were asked to do in Cave2 was take VPM+2, and try to make a reasonable table given doublr AL80s + a stage (based on 1/3s gas planning) and for a variety of depths, plan based on our SAC rate how long of a dive we could do and how much deco.

I think our table was from 50-120 feet or so ?

What we noticed was that if we planned a dive to say even 100 feet, then added BT in lumps of 5 mins, both Buhlman and VPM+2 would kind of go in a patern of "virtually no deco, not much, not much, wow -- a lot of deco"

I dont have the exact profiles here, but it wasn't for anything insanely deep.

I would post some examples but unfortunately I only have VPM on my cell phone. We used a buddy's laptop for the experiment.

I think we came to the conclusion that as was pointed out, for relatively longer shallower, we (being inexperienced at those profiles) would over-deco but some of the numbers from VPM looked (to us) kind of scary

 

[diddydidit]

For the majority of the dives I do in that range, keeping in mind that in 5 degree water we are only doing bottom times of 30-45 mins, and diving on air, both 50 and 100 are going to be pretty close on the times, maybe around 5 mins or so either way. so for me it doesnt matter. Whatever gas I have more of at the time. Or what my dive buddy has