Trying to understand my air consumption

[Raystafarian]

So this weekend I finally got to try out a BP/W configuration (rented) rather than jacket style BC (also all rented). To date, that would be dives #16 and #17 (hence basic discussion). The rig I got to try out had a wing for doubles, but I was only on a single, so I know the wing was a little too large.

I decided to go back through my dives (after open water cert) and try to figure out if what I was experiencing was my normal consumption or I was over-consuming, and if so, if it was due to the new rig or not.

All tanks were AL80

[TABLE="width: 427"]
[TR]
[TD]Date[/TD]
[TD]Max Depth (ft)[/TD]
[TD]Average Depth[/TD]
[TD]Time (min)[/TD]
[TD]Usage (PSI)[/TD]
[TD]Notes[/TD]
[TD="align: center"]Water[/TD]
[TD="align: center"]SAC (cf/min)[/TD]
[/TR]
[TR]
[TD="align: right"]Jul-14[/TD]
[TD="align: right"]25[/TD]
[TD="align: right"][/TD]
[TD="align: right"]86[/TD]
[TD="align: right"]1500[/TD]
[TD]Night, underweight[/TD]
[TD]Salt[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Jul-14[/TD]
[TD="align: right"]23[/TD]
[TD="align: right"][/TD]
[TD="align: right"]85[/TD]
[TD="align: right"]2300[/TD]
[TD][/TD]
[TD]Salt[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Jul-14[/TD]
[TD="align: right"]45[/TD]
[TD="align: right"][/TD]
[TD="align: right"]60[/TD]
[TD="align: right"]1500[/TD]
[TD]Shark Dive[/TD]
[TD]Salt[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Aug-14[/TD]
[TD="align: right"]35[/TD]
[TD="align: right"][/TD]
[TD="align: right"]75[/TD]
[TD="align: right"]2125[/TD]
[TD][/TD]
[TD]Fresh[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Aug-14[/TD]
[TD="align: right"]24[/TD]
[TD="align: right"][/TD]
[TD="align: right"]24[/TD]
[TD="align: right"]800[/TD]
[TD]Peak Perf[/TD]
[TD]Salt[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Aug-14[/TD]
[TD="align: right"]40[/TD]
[TD="align: right"][/TD]
[TD="align: right"]40[/TD]
[TD="align: right"]1700[/TD]
[TD]Peak Perf[/TD]
[TD]Salt[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Jan-15[/TD]
[TD="align: right"]31[/TD]
[TD="align: right"]17[/TD]
[TD="align: right"]19[/TD]
[TD="align: right"]800[/TD]
[TD]Cavern[/TD]
[TD]Fresh[/TD]
[TD].74[/TD]
[/TR]
[TR]
[TD="align: right"]Jan-15[/TD]
[TD="align: right"]48[/TD]
[TD="align: right"]26[/TD]
[TD="align: right"]19[/TD]
[TD="align: right"]1000[/TD]
[TD]Cavern[/TD]
[TD]Fresh[/TD]
[TD].79[/TD]
[/TR]
[TR]
[TD="align: right"]Jan-15[/TD]
[TD="align: right"]49[/TD]
[TD="align: right"]23[/TD]
[TD="align: right"]34[/TD]
[TD="align: right"]1800[/TD]
[TD]Cavern[/TD]
[TD]Fresh[/TD]
[TD].83[/TD]
[/TR]
[TR]
[TD="align: right"]Jun-15[/TD]
[TD="align: right"]24[/TD]
[TD="align: right"]17[/TD]
[TD="align: right"]60[/TD]
[TD="align: right"]1600[/TD]
[TD][/TD]
[TD]Fresh[/TD]
[TD].47[/TD]
[/TR]
[TR]
[TD="align: right"]Jul-15[/TD]
[TD="align: right"]30[/TD]
[TD="align: right"]25[/TD]
[TD="align: right"]30[/TD]
[TD="align: right"]1000[/TD]
[TD][/TD]
[TD]Salt[/TD]
[TD].51[/TD]
[/TR]
[TR]
[TD="align: right"]Jul-15[/TD]
[TD="align: right"]47[/TD]
[TD="align: right"]22[/TD]
[TD="align: right"]64[/TD]
[TD="align: right"]1800[/TD]
[TD]BPW[/TD]
[TD]Fresh[/TD]
[TD].45[/TD]
[/TR]
[TR]
[TD="align: right"]Jul-15[/TD]
[TD="align: right"]37[/TD]
[TD="align: right"]24[/TD]
[TD="align: right"]40[/TD]
[TD="align: right"]1500[/TD]
[TD]BPW[/TD]
[TD]Fresh[/TD]
[TD].58[/TD]
[/TR]
[/TABLE]

Male 155 lbs.
So, ignoring the first line as an anomaly because I honestly I was underweight and could barely descend. I didn't start to control my breathing for changing depth until the Peak Performance classes. It really felt like I was burning through air this weekend. But taking into account depth and the increased usage of air (compression) - was it all that different? I know, you can't tell me what I should or should not be using, but I'm just trying to get a handle on this. Any insight? Thanks!

 

[Diver0001]

In order to help you we need average depth, not maximum depth and we will need to know how big the tank(s) were.

R..

 

[tbone1004]

what he said. Max depth doesn't mean anything for air consumption calculations. If you're computer doesn't have avg. depth, then ask your buddy if he has it. Can't do anything with max depth

 

[jstrang]

If you know your average depth, calculate your RMV or some call SAC - here is one link - DiveNerd - SAC Rate / RMV Calculator, Imperial Units
plug in the data and let post your RMV/SAC for each dive.

 

[parzdiver]

As others have said, our average depth is needed to get an approximation of your SAC rate.

With just the information provided and assuming your consumption was high, the equipment change is a prime suspect. First is the change in gear itself. With new gear, you will probably not have your weighting perfect and that leads to greater consumption. Secondly, using a doubles wing with a single tank will have an affect. Because the wing is so over sized, and I assume not bungeed, it will flap around, causing higher resistance in the water, causing you to put more effort into moving. Also, the larger, floppy wing will take more effort to get the air to the correct place to be released.

While it is admirable that you are already looking at things like your consumption, you are a very new diver. Your breathing will probably vary with changes in equipment and environment. Start getting your gear the way you want it, focus on enjoying dives. Over time, as you become more relaxed, your breathing rate will improve and should stabilize.

 

[Mikeguyver]

Like others have said, air consumption is influenced many different actions. You need to get a "normal" set-up established and enjoy the dive. You will get into a normal routine of checking air and as you get more dives in, get a feel for how much you use. If you have access to a pool, that helps with getting a new set-up dialed in and getting your weight right. Keep diving! Mike

 

[Bob DBF]

It is your normal consumption now. The reason to know consumption rates are to plan dives, and that should be based around your worse rate then you can adjust at the end of the dive if you have "extra" air. I wouldn't worry so much about air consumption at 17 dives, I'd work on techniques and experience, monitor the consumption as an aside rather than a goal, it will sort itself out. With time and experience your consumption will stabilize and you will learn what activities will increase it.

The diving I enjoy gives me a larger consumption rate. If I hang with a photographer I can cut it by almost a third, or doing some amateur salvage work it may go up by a third. Should I base my diving on my consumption rate or just bring enough gas? It's all about your goals, not your limitations.



Bob
---------------------------
All my life I've wanted an excuse to wear a knife, and here I have found a sport where it is actually encouraged~ Dave Barry

 

[Dnaber]

From looking at your numbers and taking into account the number of dives you have I'd say you are doing well.

 

[ZzzKing]

Also, if you are wondering why it didn't magically drop because you were using a plate and wing, keep in mind that it's not like adding a performance chip in your car where you are suddenly getting 25 more horsepower and improving gas mileage by 3 mpg. You have to get used to the new stuff. As stated above, a doubles wing used with a single tank will probably adversely impact your SAC. There may be other factors as well such as trim that are making you work harder than you would if you were all dialed in.

 

[Raystafarian]

Thanks, All.

I've only had my computer since January, so I added in my average depth for the dives that I have it for - just for completeness. I'll look into calculating SAC. The wing was apparently 55lb, but it was bungied and I felt my trim was better than the dive the weekend before.

I'm sure we covered SAC in open water, but I just forgot about it.

Edit - posted my calculations above, seems I'm kind of all over the place, but gradually getting lower rates. Thanks again!