Real time SAC? How? (Ridiculous SAC)

[GJC]

I mostly agree with you but the effect of being overweighted is that you’ll have more air in your BCD when neutral so you’ll swing more when you change depth. You don’t become negative because you are overweighted: you just put more air in your BCD so you’ll have to handle a bigger volume of gas.

Unless you are so overweighted that you cannot compensate with your BCD, but then I think you have bigger problems

That's why I qualified my statement saying "overweighted and compensating using your lungs." I agree with your description of the effect on adding air to your BCD.

 

[BlueTrin]

That's why I qualified my statement saying "overweighted and compensating using your lungs." I agree with your description of the effect on adding air to your BCD.

I misunderstood what you meant and agree with you

 

[estresao]

But which did you dive for the profile you have posted. Because the 2,900Lt displayed doesn’t relate to either option.

For this one I've used doubles. 2x12L starting at 200 bars and ending at 70 bars.In Subsurface is as following:

 

[estresao]

OP is your equipment the same ?

If you switched for example from wetsuit to drysuit, you’ll probably use more air ?

More importantly are you throwing a party and buying beers for your 100th dive ?

Well... the "big change was near 70 dives ago, along this time I've done dives with different configurations, but similar results. For example:

- Single mount and TDS dry suit.
- Single mount and Cressi 5mm wet suit
- Double mount and TDS dry suit
- Double mount and Black Pearl dry suit.

With all these most of the dives surpased 20 litres/minutes, sometmes reaching 40 litres/minute. I can remember dives were my budies dove with single mount of12L at 200 barand I weared doubles 12Lx2 @ 200, and at the end of the dive my bars weres rounghly the same than theirs, thus double the SAC.


For my 100 dives I have to thorw a big party.... caviar, chapangne, etc. You're invited.. LOL

 

[estresao]

I wouldn't put too much emphasis on SAC unless you have it in context. Keep in mind that the SAC survey here is almost certainly not representative of the typical diver. Previous surveys have found that most divers wear a backplate / wing (BPW) and half of all divers have completed divemaster (DM) training. Obviously, the typical Scubaboard poster is far more accomplished than the typical diver in the water. Personally, I am low-moderately aerobic conditioned, about 10cm shorter and 10kg heavier than you, and I use 16 L/min in warm, easy diving, and 20L in cold, more challenging diving. So take that for what it's worth.

Problem is when you travel to the Red Sea and you are the first to go in and the first to get off the water.... so frustrating. I mainly dive in South Spain, Mediterranean sea... the water get easily 26 celsius degrees (78,8F), so no cold water, usualy no currents, no waves....like a swiming pool. In winter it could be as cold as 14 celsious (57,2F), so not pretty cold even in winter.

 

[estresao]

14-15L would be a great SAC rate even for an experienced diver--that's basically .5cuft/per min. I would expect the average experienced normal sized male diver to have a SAC rate somewhere around 16-19L per min. That said, you should look at your SPG and gauge your air usage in 5 min intervals--see what tasks or aspects of the dive are increasing or decreasing your usage. Doubles, drysuit, they can all add to increased breathing rate. Another factor is that your GUE training has greatly increased your overall awareness. Before GUE, you would do a dive and you were mostly unaware of your buoyancy--go up a little bit, go down -- as long as you weren't crashing into anything you thought you were good and relaxed. Now that you have GUE training you see what real buoyancy is and you notice even a 1ft/.3 meter depth change. You can use a lot more air maintaining a correct depth - I know that my SAC rate during deco when I am hanging on a line or sitting on a ledge is .4-.5 cuft/min (12-14L), but if I deco in the open ocean off a line my sac rate will be .6 because I am breathing more to stay right at 20ft and swimming to stay near the anchor line.

What kind of dives are you doing? Are they new dives in new places or dives you have done many times before. Sometimes there is additional stress on our breathing rate even though we don't actually "feel stressed at all". I know that a SAC rate is usually higher if you are leading a group of divers vs just following a long in a pack. I once took a class where my SAC rate was 25-40% higher than avg. I found it very strange. I didn't feel stressed, but first day after class I was doing the SAME exact type of dives I was doing in class and my SAC rate had returned to normal.

I don't use AI and I don't particularly trust computer SAC calculations. I always take notes of time, depth, starting and ending pressure and do the calculations myself so that I know I can trust the results.

I totally agree with you and maybe what I need it just have a little patience, practice and let the time do it's work. But I was thinking a "real time SAC tool" could help my in dincovering these moments in which I'm consuming more to be aware of them, take some actions and avois errors or evolve my technique in particular aspects.

Most of my last divings were at the same place, no more than 7 meters, practicing. In general I don't feel stressed, but have to say sometime I get frustrated when practicing and trying to get still in a spot.

 

[estresao]

The primary trigger for increased breathing is an increase in the CO2 your body is producing. If you are working harder to swim, are cold, or nervous, you are producing more CO2 and need to breath more. If you are relaxed, warm and not moving your muscles a lot, your SAC will drop.

Using your lungs to maintain your buoyancy can affect how well your lungs get rid of CO2. Taking slow deep breaths, fully inhaling and fully exhaling is the best way to get rid of CO2.

If you are overweighted and compensating for it using your lungs, you will not be exhaling as much as you should be (keeping a good amount of air in your lungs to maintain buoyancy) and not getting rid of CO2 efficiently. This causes you to breath faster to get rid of CO2 and your SAC goes up.

If you are underweighted and compensating for it using your lungs, you will not be inhaling as much as you should (keeping your lungs partially deflated). CO2 is not efficiently removed and you need to breath faster (but shallower) and your SAC goes up.

So your best bet to reduce SAC is to get your weight right for neutral buoyancy, relax, stay warm and don't work hard.

That could be related to what I deduced. I'm pretty sure I'm not overweighted, but as I've said, I trend to keep negative, I mean, empty too much my wing, which effects could be pretty much the same that being overweighted, and the end of the day I need overbreath to keep in a particular deep level.

 

[estresao]

@loosenit2

I do exactly that. I keep my tank pressure visible on the bottom row along with my real-time consumption rate. I am able to connect task load and actions with resulting air consumption and it is really interesting to see how it affects it, or it reminds me to slow down on my breathing given what I am trying to do or accomplish while keeping in mind the conditions. It is very insightful. I have everything going through MacDive and I pick tank size there. It is fun to see the data graphs on my air consumption rate steadily lower over the last few hundred dives. Using MacDive, I can also use keywords or tags and then use those to search and only show what it is in warm water vs cold, or for a certain country or region I was diving, etc, or conditions (by tagging it with "current" or "drift", etc. ).

I think it worth give a try to that.

 

[BlueTrin]

For my 100 dives I have to thorw a big party.... caviar, chapangne, etc. You're invited.. LOL

Lol ... I eat a lot !

I also use a lot of air, particularly in my drysuit.

However, I have noticed that if I try to get myself in the most relaxed state possible (imagine that you are trying to get in a vegetative state where you breathing becomes slower) and breathe in slowly for a few seconds then wait a few seconds, breathe out for a few seconds then my consumption drops.

The breaths are deep but not full lungs just similar to what you’d do when relaxed (imagine meditating rather than breathing hard) ... also you are not forcing yourself to hold your breath but more like trying to relax.

However this is not natural for me (at least not yet) and if I don’t focus on it, I revert to my heavy breathing.

 

[Edward3c]

For this one I've used doubles. 2x12L starting at 200 bars and ending at 70 bars.In Subsurface is as following:
View attachment 539343

130bar for 2x12s gives a gas used of 3,120Lt therefore 23.28Lt/min, not the 21.7Lt/min Subsurface displayed.

If you’re constantly changing your configuration you’re not giving yourself the chance of becoming familiar, and comfortable, with one setup.