Pocket Shorts, Drag, and Increased Air Consumption

I keep track of my air consumption (i.e., SAC) on every dive. (I’m funny that way.) Although my SAC on local dives in cold water (in a drysuit) continues to decline (albeit slowly at this point), on a warm water (wetsuit) dive trip this summer, I was surprised to see that my SAC had increased from previous warm water dives. And this higher SAC was in evidence on my subsequent warm water dive trip last week. Then in dawned on me that my higher SAC was on dives where I was wearing pocket shorts on top of my wetsuit. The difference in SAC is about 10% (0.50 vs. 0.55 [and the difference is statistically significant]). I realize, of course, that there are many factors that influence SAC, but I wondering if others have experienced this sort of difference with pocket shorts or with other gear changes that would seem to have only a minor effect on drag.

Just added a graph of SAC vs. Dive number. Dives with pocket shorts look more like drysuit dives than wetsuit dives.

Hmm . . . I can't say that I have, but I don't think I would notice a 10% change, because my SAC isn't that reproducible anyway. In theory, the pockets are in the slipstream of the shoulders if you are horizontal, so they shouldn't affect much.

TSandM:

In theory, the pockets are in the slipstream of the shoulders if you are horizontal, so they shouldn't affect much.

Click to expand...

I'm not horizontal, but close!

My dive trip SAC is remarkably constant with a reasonably tight standard deviation 0.33-8 +/- 0.01-4 cu ft/min. Though I have no experience with adding pocket shorts, I might be aware of a 10% increase if there were not other reasons to explain it like temperature, exertion, etc.