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Tank Jockeys meeting April 17, 2009

Posted by Chris Sullivan in Equipment, Shipwrecks, Technical Diving, Training.
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On Tuesday, April 14th, the “Tank Jockeys” got together for the monthly meeting at Shoeless Joe’s in Newmarket. About 40 people showed up, which is well-attended for our club. Unfortunately we had to meet downstairs in the main part of the restaurant instead of the more private area upstairs, as a meeting for a hockey pool had beaten us to it.

There was lots of discussion about the upcoming trip to the USS Ex-Oriskany. It looks like most everyone is traveling in pairs, which makes sense as people are on different schedules and traveling by car means there won’t be much room after the equipment, including 4 tanks apiece, has been stuffed in. We’re all a little nervous about the potential of having to drain our tanks at customs, and will have VIP stickers and hoses to move gas from one tank to another on hand at the destination.

For the first time in a couple of years we had a featured speaker, Doug Arnberg, an SDI/TDI Instructor Trainer and Eastern Regional Manager. He’s also a professional photography and has been published many times in wreck diving magazine. He brought along a VRx for us to look at. Not surprisingly, playing with the unit confirmed to the people who were already convinced that it is a wonderful computer, and to me, who is not convinced, that it is not. Some of the more noticeable issues were:

  1. The regular graphics (not using the big graphics option) font size was tiny. I couldn’t use it without my glasses. This would be a problem when trying to set it up on the boat. I didn’t get a chance to try it with the big graphics, though.
  2. The user interface is completely non-intuitive. Each screen has a different method of operation, with various complex button pushes.
  3. To make the user interface even harder, there were significant delays in the reaction time of the unit. To make things worse, identical operations took different lengths of time. Sometimes I’d press a button and it would take 3 seconds to react while other times it would take around 20 seconds.

The decompression algorithm is a minor complaint. It is based on Buhlmann ZHL16C algorithm which I know and love, and includes Gradient Factors although the factors cannot be entered directly. That’s a definite drawback in my opinion, which is undoubtedly coloured by my overly analytical way of thinking. The VRx handles conservatism in a variety of ways, including pretending that more inert gas (in this case Nitrogen or Helium) is in the tank than is actually there, and using their new “VGM” algorithm which tailors the gradient factors to the dive profile. While this seems like and admirable idea, I’d like to have complete control of my decompression parameters even if it means sacrificing some flexibility.

Andrew checks out the VRx

Andrew checks out the VRx

Doug, who I assumed is somewhat biased as to the best of my knowledge he is somewhere in the supply chain for these units, did his best to point out the good features of the unit. One of the benefits he mentioned was that the decompression algorithm was validated through thousands of dives. I’ve read criticism of this because the dive information is proprietary and the symptom reporting is subjective. Personally, I would want to see external validation in the scientific community with published and preferably peer reviewed results before relying on a decompression algorithm. The only feature that really makes an impression on me is the unit’s compactness compared to the similarly priced Shearwater Pursuit.

His digital photography was quite amazing, with the first part of the slide show comprising of wrecks primarily from the St. Lawrence River. Some of the wreck near Picton Ontario looked especially good and the club informally resolved to plan a trip there. The most surprising thing is that the visibility in the photographs is so much greater than what I remember when diving the same wrecks.

Doug addresses the Tank Jockeys

Doug addresses the Tank Jockeys

Doug pointed out damage on one of the wrecks by the first team to dive on it (he was on the second), and the importance of not touching these wreck at all. They are part of the Great Lakes/St. Lawrence history.

Doug also spent time working with NOAA saturation diving on the Aquarius Project to test software changes on the Inspiration rebreather. He described living in the underwater habitat in gory detail, including the details of going to the bathroom. Suffice to say I wouldn’t want to eat the fish in that neighbourhood



1. Bubbling blood « Chronicle of an older diver - May 13, 2009

[…] water divers. Another is that it mentions Aquarius, an underwater habitat created by NOAA, where Doug Arnberg who came to one of our dive club meetings did some rebreather work. Lastly, it described taking a blood sample from an inhabitant of […]


2. SDI Comes to Town « Chronicle of an older diver - March 17, 2011

[…] then started the introduction to SDI/TDI. This started with the announcement that Doug Arnberg was no longer the Eastern Canada Regional Manager. No explanation was given. I imagine I’ll […]


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