Overshooting NDL and mandatory deco stops

[EFX]

You can't directly change the GF setting in a Perdix in rec mode anyway. They are preset and unchangeable, determined by the low, medium or high conservatism settings.

Starting with v65 of the software you can set the GF's in rec mode. The preset GF's for low, medium, and high conservatism are still there but a fourth option called custom lets you adjust the GF's. Sorry, if someone already replied to this. I haven't read through all the posts yet.

 

[uncfnp]

A valuable quote ... I guess your wife's not on SB. Don't worry, your SB friends know that what's written on SB stays on SB (or something like that ...) ... perhaps ...

But you missed the part where he said women were fatter.

 

[rsingler]

 

[Blackcrusader]

Well, that was interesting! I guess I'm a "normal responder", lol! That was NOT fun.
Can you stay calm enough to get yourself both out of difficulty and eliminate your hypercarbia? Do you have enough gas at depth to handle 4x your nominal requirement? That was interesting!

I'm going to Bali with a friend March April. A couple of the dive sites we do are fast drive dives at 5 knots or more. A lot of exertion involved to maintain depth and direction... We do some fast drift dives each year. Not for the feint hearted or those prone to panic. Panic mostly comes from anxiety and lack of experience of know how to handle conditions.

Mainly on deep dives ( lets say below 25m ) I do try to do dives with minimal current. The type of current that carries you along at such a gentle pace you can simply turn head into the current and not drift away. Thanks for your posts they are very interesting to me and others who are not medically trained. I'm 60 this year. Do I have enough air for emergencies... that's a yes enough for both myself and a dive buddy if required. There are times when I would use a larger tank just to have the extra air capacity, if the dive center offers them. A 120 cubic ft steel with 230 bar gives you a lot of air, but heavy tank and lots of drag.

 

[atdotde]

Also height, pants size, and gender.

Seriously, RMV at rest should be proportional to the metabolism that your body need to keep you alive and I would expect that to be proportional to your mass (maybe with some offset for brain etc). In a very limited survey of my diving friends I found that to be the case.

 

[Diving Dubai]

GAs consumption is a weird thing - past a certain point

My wife has a large lung volume (measured) has a sedentary lifestyle, by her own admission could lose a few lbs, but has a more than enviable gas consumption. Not once has a guide nor instructor male or female young or old, ever come up with more air. I sit around 11/m but can't hold a candle to her

The downside is that it's hard to get her to improve trim (she got lazy) because she can counter with the low gas consumption card

I'm convinced she does Zen out and her body slows down. I've watched her breath, its not shallow, but it is really really relaxed.

Also smokers bizarrely seem to have a lower consumption, and when they quite their consumption goes up. Lots of anecdotes from dive pro's who know there consumption very well, quit smoking and seen it rise. I'm sure there's a medical reason

 

[scubadada]

@Diving Dubai

Your RMV is relatively low, any idea what your wife's RMV is?

 

[Diving Dubai]

@Diving Dubai

Your RMV is relatively low, any idea what your wife's RMV is?

Take this with a pinch of salt, because I don't have her computer, but I'm calling 7.0 - 7.5l/m ish

How I got to that figure:

Start contents( in litre) of our (different sized) cylinders minus end contents to give litres consumed for each of us (and its a rough number but I know our rough difference in end pressure

some basic maths to give a percent difference

Apply that percentage diff to my SAC and you get hers. Roughly ish

EDIT

Another point. On the first dive of a day, whether repetitive dive or not, my consumption is "rubbish" approx 14l/m I put it down to my aversion to mornings. But I always need one dive.

EDIT 2 - these are normal dives, not working hard in current where SAC goes up (obv)

 

[dmaziuk]

Seriously, RMV at rest should be proportional to the metabolism that your body need to keep you alive and I would expect that to be proportional to your mass (maybe with some offset for brain etc). In a very limited survey of my diving friends I found that to be the case.

I would expect lung size to be the defining factor: you only metabolize a couple of % of the O2 in the air, the rest goes in and out of the lung. Height would be a proxy measure for lung size.

OTOH if you want to go with weight, you'd probably want to adjust for sex as males have more muscle that I think consumes more O2 than fat (excluding brain, of course). If true, you'd expect women to have lower SAC and they seem to. But that may be due to smaller size and therefore smaller lungs. Or both.

OTGH you gotta wonder if skinny people burn less O2 due to, I dunno, less water resistance, heart not working as hard to push the blood around, etc. (It does not look that way from what I've seen so far but my sample size is pretty limited too.)

 

[Blackcrusader]

Now that I see that my .3 cf/m equals 8.5 L/m and BlackCrusader's is 6.85 L/m, I can see why his causes some consternation. I don't think I've been diving with anyone who has a lower consumption than mine, and I'm a petite female. Though I have been diving with even some males who have about the same consumption.

A British chap I dive with a few times a year has the same air consumption as I do. He is about the same height but half my mass.
So I'm not the only one I know with good air consumption. I've met many Asian male pro dive masters who dive for a living that are also excellent on air. I've met another lass from Taiwan who is a nurse in an ICU unit about 155cm and light as a feather 45kg who is also like me excellent on air. Being a waif helps I think. Maybe there is no rhyme or reason why some experienced divers are better than others.