your SAC is fine.
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SAC Rates
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SolarStorm
Contributor
I dont know if this is right, but I just went through my Oceanic Dive Log. I am 50 yrs old 5'10" 185 lbs. My SAC rate hovers around .47 - .5 and once when we were in heavy seas and current up to .65. My 18 yr old daughter never broke .5 after 32 dives. (I understand her, she is a national level athlete and trains 1 - 3 hrs daily) now this is based on tropical dives in the mayan rivera and Coz. and I am sure the cold water will increase this a bit. We have never been the first the in the group that needed to surface and typically surface with 1000 psi, my daughter with more. (I honestly dont think she breaths...)
Mike Boswell
Contributor
I'm a sipper, having developed some of my habits as a freediver. On warm tropical water scuba dives my Suunto Cobra tells me my SAC averages 0.32 (ranges from 0.28 to 0.36). In cold water it is usually in the 0.5 to 0.7 range depending on exertion.
A low SAC may be of little benefit, however. In our group dives in Roatan two weeks ago I invariably ended the dive with a half-full tank, which caused me more disappointment than pride.
When I download my dives from the Suunto it computes the average SAC and also plots a line graph over the course of the dive. You would think that line would be more or less horizontal and that it would be the same number regardless of depth, but it isn't. The rate is lowest at the deepest parts of the dive and increases when you get shallower. I imagine this is an artifact of more rapid changes in depth and the relatively slow 10 or 20 second sampling rate, but I really don't know.
A low SAC may be of little benefit, however. In our group dives in Roatan two weeks ago I invariably ended the dive with a half-full tank, which caused me more disappointment than pride.
When I download my dives from the Suunto it computes the average SAC and also plots a line graph over the course of the dive. You would think that line would be more or less horizontal and that it would be the same number regardless of depth, but it isn't. The rate is lowest at the deepest parts of the dive and increases when you get shallower. I imagine this is an artifact of more rapid changes in depth and the relatively slow 10 or 20 second sampling rate, but I really don't know.
I wouldn't be surprised, Mike, if you don't use your breath more for buoyancy control in the shallows, and get less efficient. I know I do.
i am also 5'10 and 200# and my sac is about .5-.6 in warm water.
I think a good Sac is one that has you not being the first one on the boat and not the last one on the boat. too low and you just waste air in your tank, too high and you cant hang till the end of the dive, about in the middle is the blessed path. or something like that. (Buddha reference
)
I think a good Sac is one that has you not being the first one on the boat and not the last one on the boat. too low and you just waste air in your tank, too high and you cant hang till the end of the dive, about in the middle is the blessed path. or something like that. (Buddha reference
)
Mike Boswell
Contributor
This is possible. I haven't done the mental math but I would guess that the volume of air used to produce a given buoyancy change would be proportional to depth. Anyway, you taught me long ago to use the wing - not my lungs - for that.
However, on most of the dives we would finish up in 20' under the boat, and my wife and I would just settle motionless near the sandy bottom and watch critters, feeling somewhat robbed, as the rest of the divers boarded the boat.
With the Suunto SAC graphs, on every dive the same thing happens, with the plotted Suunto SAC curve rising significantly as you ascend.
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Blackwood
Contributor
Thank you......
Well, that's really what matters. Trying to hit some number which may not even support your physiology is pointless.
In benign cold water deco conditions I'm often under 0.5. I know people who average 0.4. On the bottom I plan for 0.75. It's all really about knowing what you breathe, equipping for it, and then striving to improve relative to yourself, not relative to other people.
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You can expect to improve more ... how much more depends on how often you dive, what habits you develop, and how streamlined you become in the water.
I'm 5'9" and about 240 lbs ... and my consumption rate is, on average, about two-thirds of yours. But I dive often, go slow, and have my gear pretty well dialed in. In fact, I'd say I breathe about as hard underwater as I do relaxing on my sofa with a good book.
As I like to tell my students ... if an old fat guy can do it, you certainly can ...
... Bob (Grateful Diver)
Mike Boswell
Contributor
Note for Suunto Users: SAC calculations:
Found this discussion via google search:
Tim Digger21-10-2008, 08:29
...Two the SAC graph is I think wrong in that it seems to be depth related, in that at shallower depths I have a higher SAC, from a sensible average 13lpm at 20m to 25-30lpm at 5 m resting on a platform. No way correct.
Tim Digger27-10-2008, 13:26
Reply from Suunto confirming what I had already feared. The SAC calculation for the whole dive is based on start and finish tank pressures size of cylindand average depth of dive. The graph of SAC and tank pressure that can be produced by DM 2.6 is based on a tank pressure graph with only 2 data points, start and finish and is a straight line the variation in the SAC graph is produced only by the use of depth stored data and does NOT reflect real variations in SAC (Minute Volume M.V>). They did however admit that this may change on newer models of dive computer produced in the future. I think the deficit is in the log records of the Vytec as the tank pressure must enter the Vytecs caluclations to display remaining Air Time, it just does not record it where Dive Manager can get at it. Pity.
Found this discussion via google search:
Tim Digger21-10-2008, 08:29
...Two the SAC graph is I think wrong in that it seems to be depth related, in that at shallower depths I have a higher SAC, from a sensible average 13lpm at 20m to 25-30lpm at 5 m resting on a platform. No way correct.
Tim Digger27-10-2008, 13:26
Reply from Suunto confirming what I had already feared. The SAC calculation for the whole dive is based on start and finish tank pressures size of cylindand average depth of dive. The graph of SAC and tank pressure that can be produced by DM 2.6 is based on a tank pressure graph with only 2 data points, start and finish and is a straight line the variation in the SAC graph is produced only by the use of depth stored data and does NOT reflect real variations in SAC (Minute Volume M.V>). They did however admit that this may change on newer models of dive computer produced in the future. I think the deficit is in the log records of the Vytec as the tank pressure must enter the Vytecs caluclations to display remaining Air Time, it just does not record it where Dive Manager can get at it. Pity.
I've been diving in relativelly cold waters with wetsuit.
My average SAC rate is around 0,65
I've been always concerned for such a high figure, but now I read that it's normal.
I have no experience diving in warm waters, I mean caribean waters, where I should expect to have a smaller SAC rate.
My average SAC rate is around 0,65
I've been always concerned for such a high figure, but now I read that it's normal.
I have no experience diving in warm waters, I mean caribean waters, where I should expect to have a smaller SAC rate.
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