Stage planning in caves

[rjack321]

Sheesh I thought my SAC at 0.48-0.5 was decent. :11:

I didn't actually calculate that SAC, those #s are just a guess based on my 500psi used to Danny's 200psi on dives we did in Nohoch. :d

Skip breathing is definately one cause of headaches. But that's topic for a different thread.

 

[SparticleBrane]

I think one of the things that keeps me from getting a lower SAC rate (besides being overweight and out of shape) is the fact that my breathing pattern keeps my buoyancy right on target.

 

[lamont]

I find that a SAC of below 0.40 on scooter dive makes my head get a little wiggy due to CO2 buildup... When I'm stressed it can go to about 0.80... I need to hit the pool more and do more laps...

 

[TSandM]

Our dives in the Devil's system, doing the pull and glide against the flow, my SAC rate was up to 1.0!

 

[amascuba]

Wearing doubles and sometimes a stage, in an environment that I'm familiar with, my SAC is typically between .5 - .6.. That's usually the case when I'm working OW classes (wearing doubles), and having to keep my awareness of where the OW students are.

In the Caribbean my SAC is typically around .3 - .4, depending on currents.

My SAC has been as low as .28 in a warm water, shallow spring that I have about 90 dives in.

I typically make my plan thinking that my SAC is going to be .6 for the dive and 1.0 for an emergency.

I agree with everybody else. This has been a great thread and I've enjoyed reading the different points of view.

 

[RTodd]

Too low of a SAC rate does cause a CO2 headache. Danny's sac isn't that low because I can beat him (barely) as long as I make him do all of the extraneous work, lines, marker, etc. I suppose it may get that low in just a set of doubles following students. Most of the time a really low sac rate, for an individual, causes CO2 headaches because of poor breathing. I get them on really easy dives because I don't focus enough on my breathing and the rate gets too low so I don't necessarily excahnge gas at the right time. I try to target around .4 which is partially achieved by breating a bit more on exit when things are going well in order to clear my system of any CO2 that may have started to build. But, indivdual SACs do vary and, while Danny is tiny, I am fairly small which helps to a small amount. More importantly, what I was alluding too above is that the ability to stay relaxed and keep breathing low, when juggling a stage drop, when something goes a little sideways, etc. is the key to the ability to make open circuit stages last. Not, some really low sac rate to start with. Of course, the two tend to go hand in hand.

 

[coldsmoke]

I get them on really easy dives because I don't focus enough on my breathing and the rate gets too low so I don't necessarily excahnge gas at the right time. I try to target around .4 which is partially achieved by breating a bit more on exit when things are going well in order to clear my system of any CO2 that may have started to build.

I think this might have been my problem. I don't skip breath (consciously anyway) but these times were in a very familiar area with pretty good conditions. I think I was just very (maybe too) relaxed. So to prevent it, I should just try to breath a little more - does this mean deeper or more rapidly or both? Thanks.

Since I got us off topic and I'd hate to be the one to kill the thread how about this. I am sure it's a pretty basic question and possibly bordering on dumb, but I'm very new to this stuff. Basically, what I have learned so far is that for easier dives you are still really using the rule of thirds for total gas including your stages. But there are better ways to utilize your stages to minimize problems or rather make dealing with problems that have occurred easier. When you are diving more complicated dives with scooters you move this to 1/6's. This is still for total gas supply with the same rules applied to stage usage. It seems logical that you would increase your gas conservatism because you travel farther on a scooter on a given gas supply than you would swimming. Based on the increased conservatism factor I am concluding that you travel a little more than twice as far on a given gas supply on a scooter than you would swimming. Basically, 1/6 in, scooter fails and buddy is OOG so you you have a little more than 2/6 for you and a little more than 2/6 for your buddy to exit. Is this correct reasoning? Also, it seems like you would get a better ratio of gas/distance scootering vs gas/distance swimming than 2+:1. Especially since you are now swimming, maybe towing a scooter, and in a more demanding situation thereby possibly increasing SAC.

Hunter

 

[RTodd]

An efficient diver on a scooter loaded down with extra scooters and stages, depending on flow, is moving at at least 200 fpm and using far less gas per minute than a diver that is swimming. I doubt many people are swimming 100 fpm and if they are they are using far more gas in that minute. So, while your basic understanding above is correct and 1/6 should allow a short body diving caver to get out swimming in a high flow cave in most situations, that doesn't work as the dive compexity increases and is why things like extra scooters start becoming a factor in the overall gas plan. Your basic understanding of how we use stages is correct.

 

[coldsmoke]

So do you always bring an extra scooter? If you don't then how do you plan for scooter failure?

 

[RTodd]

So do you always bring an extra scooter? If you don't then how do you plan for scooter failure?

Generally yes, but an easy dive with a short body has alternatives to a backup. Way beyond the scope here. First choice is a backup, second choice is buddy towing you. The nature of the dive dictates how viable being towed is. I.e. being towed out on a multi-stage dive that was properly planned means you experienced multiple scooter failures.