EDITORIAL, MAY 2010: ISN'T IT TIME?

By Alex Brylske
Photo by Joseph C. Dovala
(Readers, please comment at bottom of editorial)

Unless you were on some other planet recently, you no doubt heard about the recent event at Orlando’s SeaWorld in which a trainer was killed by an orca. Clearly, it was a tragic situation made worse in that it was apparently a very public spectacle. And unlike what was initially reported by authorities, the victim did not fall into the pool, but was grabbed and dragged into the water by the whale. Some were surprised that the animal wasn’t put down, as would have been the case with a dog; and many even expressed alarm when it was made public that this was the third fatality involving the whale, Tilikum. (Although, in fairness, it’s far from certain that he was the cause of one of those deaths.) Personally, I was heartened to learn that Tilikum wasn’t euthanized. It also made me question the purpose and true cost of turning marine mammals into circus performers.

NO DUMB QUESTIONS, MAY 2010: A PHYSICS PRIMER FOR SCUBA DIVERS

by Alex Brylske
Photo by Joseph C. Dovala
Readers please submit comments at the end of the article.

Q: Al Pinzon had a question about tank capacity. “My wife and I are recently certified Open Water divers. I use an 80 tank and my wife uses a 50. Our question is how do we know exactly how much air is left in our tanks at the conclusion of a dive? Even though each of our submersible pressure gauges (SPGs) may both read 500 psi, we know we don’t have the same amount of air. So how do we determine the amount of air left in the smaller tank so my wife doesn’t risk running out of air?”

A: There’s a very simple way to convert psi to cubic feet. Just take the capacity of the cylinder in question and divide it by its maximum working pressure. The product is, in essence, how many cubic feet of air is accounted for by each “psi.” Let’s take the standard 80-cubic- foot cylinder as an example. By dividing 80 (its maximum capacity) by 3,000 (its maximum-rated pressure) we get 0.0266. In other words, we can assume that each psi of pressure accounts for 0.0266 cubic feet of air. Thus, if the tank is filled to only 2,000 psi, rather than its maximum 80 cubic feet, it contains only 53.2 cubic feet (2,000 X 0.0266).
In the case of your wife’s 50-cubic-foot tank, the value is 0.0166 (or if she uses the more standard 63 cubic footer it’s 0.0210). Therefore, if you each end your dive with 500 psi remaining, you have 13.3 cubic feet of air left but your wife has only 8.3 cubic feet.

Of course, even though your wife would have less air remaining, it’s likely she also uses less air, which is why you can both plan to exit the water with 500 psi. So, with all things being equal, you’d both have about the same usable reserve in terms of time underwater at the same depth.

More questions after the break...

BUDDY LINES: LETTERS TO THE EDITOR, MAY 2010

Readers may add additional comments at the end of this article.

SOLO DIVING SHOULD BE EMBRACED

I am in total agreement with your editorial, “To Buddy or Not to Buddy,” Dive Training, March 2010, and would like to thank you for this long overdue discussion. I have been diving since 1968 and was an instructor in the earlier days of scuba diving. My interest in underwater photography and videography brought me to many international open waters. I appreciate the evolutionary technical, physiological and teaching improvements, however, I think this at times forced “buddy system” has reached an excessive level.

The increased focus on “self-reliance” would necessitate a better understanding of one’s own equipment and capabilities, and it would not degrade any safety procedures.

I am a divemaster and do understand the psychological intent of the buddy diving teachings, however, especially in underwater photography and videography, a buddy is not necessarily a positive part of the dive. Having been on many live-aboards, I appreciate (as some live-aboards now practice) my diving-solo-privacy. Though I generally travel with two longtime diving buddies, our actual diving is not keeping your buddy at arm’s length and/or annoying him/ her with the frequent “Are you OK?” hand signal.

The attitude in existence today forces one to pretend to agree to the “buddy system,” which oftentimes leads to the “once we are underwater I’ll do it my way” situation. The situation described in the article creates uncomfortable and resentful feelings and is not a positive experience. The “solo diver” should be accepted and accommodated, especially since everyone signs all legal responsibility “absolution” papers at any and all scuba diving activities, from “air fills,” to rental equipment, to boat dives.

Heinz W. Blaume
South Lake Tahoe, California