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The Avro Arrow Models October 28, 2009

Posted by Chris Sullivan in Diving Books and Films, Shipwrecks, Technical Diving.
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I just watched, not for the first time, a Sea Hunters episode from 2005 on a search for several models of the famous Canadian fighter aircraft, the Avro Arrow, in Lake Ontario. In this episode, the crew took their boat from Port Dover in Lake Erie to Point Petre in Prince Edward County in Lake Ontario, where during the mid-to late 50s Avro Aircraft Limited shot models of their aircraft into the lake at supersonic speeds, on the nose of a rocket.

They didn’t find it. They found an unidentified sailboat from the mid 19th century in great condition at a depth of 200′. They also found a rocket which  they believed to be a Canadair rocket booster used to test the Velvet Glove Missile, which was being designed as armament for the  Arrow. This booster was designed in part by Gerald Bull, a Canadian engineer who was assassinated (reputedly by the Mossad) while working on Project Babylon, a supergun for the Iraqi government.

The show then rambled on into a rather pointless expedition off the Virginia coast  where the visibility was so back they could only feel the object they were trying to investigate.

Despite the squirrely storyline, the Sea Hunters is my favourite underwater TV show. It’s short on the wonders of the ocean environment and long on hard core diving and exploration (not that I’m against the environment, sharks or pretty fish, it just gets repetitive after a while). In Lake Ontario they were diving surface supplied trimix with a hardhat and ship to diver voice communications, running sidescan sonar, and a ROV. What could be more fun than that?


A Sad State of Affairs October 25, 2009

Posted by Chris Sullivan in Technical Diving.
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Yesterday (October 24th, 2009) I attended the 30th annual meeting of  the  Great Lakes Chapter of the Undersea and  Hyperbaric Medical Society. For reasons I’ll explain at another time, this is probably the last meeting of the chapter, due to reorganization of the parent society.

There were many interesting talks, but one thing really stuck in my mind about the state of hyperbaric medicine in Canada – and that is that it isn’t taken seriously enough. Hyperbaric medicine is used in the treatment of several ailments, including

  1. Air  or gas embolism
  2. Carbon monoxide poisoining
  3. Clostridial  myositis and myonecrosis (gas gangrene)
  4. Crush injury, compartment syndome and other acute ischemia
  5. Decompression sickness
  6. Enhancement of healing in selected problem wounds
  7. Exceptional anemia
  8. Intracranial abscess
  9. Necrotizing soft tissue infections (like necrotizing fasciitis a.k.a. flesh-eating disease)
  10. Ostemyelitis
  11. Delayed radiation injury
  12. Grafts and skin flaps
  13. Thermal burns

One particular aspect of the above was in  the treatment of diabetic foot ulcers, which often would otherwise result in amputation. With the population (like me) aging, diabetes is becoming more common and the incidence of this problem will grow proportionately.

However, when we visited the Hyperbaric Facility at Toronto General Hospital and asked why it wasn’t in use at that time, the reply was that there was no funding to pay for technicians. Meanwhile it seems that private hyperbaric facilities are popping up all over the place for treatments that have no proven benefit, putting, as we heard, the situation as on where a clinic “can charge patients for hyperbaric oxygen therapy for conditions that is doesn’t work for, but cannot charge for condition for which it can”.

Per capita Canada has about 10% of the number of chambers as the US available for physician-prescribed HBOT. Part of this I’m sure is the stringent controls on private facilities  that  can avail themselves of  government funding,  and of public facilities  that can access private funds (i.e extra-billing  which was outlawed decades ago  by the government of Pierre Trudeau).  But it also seems there is a general ignorance and/or  scepticism with regard the to usefulness of HBOT, and the leaders of the  chapter are campaigning for greater awareness and education amongst the medical community.

Let’s hope they succeed. Access to recompression chambers for emergency use  is essential to divers, but actually provide greater benefits to the general public. That’s a double win.

Email Scam October 23, 2009

Posted by Chris Sullivan in Miscellany.
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A little off topic, but this one would be kind of fun, if only people would stop falling for these things. I’ve heard of this particular scam just recently. The premise is that someone you know has been mugged, arrested, sick, or whatever in some foreign country and now needs money. This one however is quite poorly executed.

By the way, for the first time ever, I replied to one of these (after stripping my contact details from my email signature). I said I’d be happy to help, and just send me details of the police report #, the hotel name, the airline and flight #, etc., and I would have a close friend in the RCMP help him out via the  local police department.

Of more  concern is how they got my friend’s email address, since the reply was requested through his legitimate address. I hope to find out soon. This comes less than 24 hours after another friend’s Facebook account was hacked… Let’s be careful out there in cyberspace!

This had to come in a hurry and it has left me in a devastating state.We are in some terrible situation and we really going to need your urgent help.Some days ago,unannounced,We came to visit a resort center in South Glamorgan UK,England…but we got mugged by some hoodlums and lost all our cash,credit cards,we are financially stranded right now and our return flight leaves in few hours time but we need some money to clear some bills,we didn’t bring our cellphone along since we did not get to roam them before coming over.So all we can do now is pay cash and get out of here quickly.we do not want to make a scene of this which is why we did not call my house,this is embarrassing enough.we was wondering if you could loan us some cash,will def refund it to you as soon as we arrive home just need to clear our Hotel bills and get the next plane home,As soon as we get home we will refund it immediately.Write me so we can let you know how to send it.

How to Reset an Apeks Quantum October 22, 2009

Posted by Chris Sullivan in Equipment.
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Somebody searched for this question and it’s an easy answer so here it is.

There’s a grey button on the back of the unit. Find something pointy but not sharp and use it to hold the button down for a second or two. There, you’ve done it.

But wait, you’ve just reset your computer. You will have to reset the time (press the mode button until you get to the TIME screen, and then use the left and right buttons to set the time – unless you’re over eighty you should be able to guess how to do this).

You will also have to set your computer to Imperial from Metric if that’s the way you dive. Use  the MODE button to go to the DIVE screen, and hold both the left and right buttons down for about 5 seconds to move from Metric to Imperial.

That’ll do it. You’ll have to reset your alarm preferences and enter your gas mixes as well if that’s what you need. You may also want to set it to fresh water from salt (also on the DIVE screen), and if you’re like me and using it with tables from DIVE to GAGE mode.  Logged dives will not be erased.

The Future of Diving October 21, 2009

Posted by Chris Sullivan in Technical Diving.
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I picked up this pointer on the Ontario Diving web site.  It’s  the proceedings of the Baromedical and Environmental Physiology Group of the Norwegian University of Science and Technology, 18–19 December 2008, in Trondheim, Norway and looks pretty interesting, although it’s still downloading as I write this. It  has an appendix the entire seminal document on  decompression sickness (“The Prevention of Compressed Air Illness”) by John Scott Haldane, which makes up about a third of its almost 300 pages.

I was pleased to read the  following sentence in one of the papers: “Nevertheless, there is no clear evidence, to date, that diving, in the absence of serious acute damage, leads to long-term neurological dysfunction.”  That’s good news, I think.

Blending Trimix October 19, 2009

Posted by Chris Sullivan in Technical Diving.
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As described in a prior post, I recently took the DSAT Gas Blender course which includes Trimix blending. No formulas were provided for trimix blending but you get a handy little program for calculating the blend for a partial pressure mix or a top-up for trimix, which is a whole lot simpler than doing it by hand. However, it’s not really difficult to calculate trimix blends using the method I came with during the class.

The most  difficult part of blending Nitrox is that the Oxygen in air comes premixed with 78% Nitrogen. If we were making Nitrox from pure Oxygen and pure Nitrogen anyone proficient in mental arithmetic could figure out the blends in his or her head. For instance, a 3000 PSI tank of EAN36 would need 1,080 (3,000 x .36) PSI of Oxygen and 1,920 PSI of Nitrogen, but as we generally top up with air, only 570 PSI of Oxygen is needed because the air already contains some.

As Helium is not a significant component of air, we can use this simple method to calculate the required partial pressure of Helium in any mix. So a 16/40 mix (40% Helium) has 40% x 3,000 or 1,200 PSI of Helium and 1,800 PSI of some combination of Oxygen and air. Similarly, a 4/80 mix has 2,400 PSI of Helium in a 3,000 PSI tank, with 600 PSI of Oxygen and Nitrogen.

So what about the rest? This is a little more complicated, but there’s a fairly easy shortcut. Let’s look at an 18/50 mix, since this is an easy example. This mix is 50% Helium, which would be 1,500 PSI in our AL80. The other 1,500 PSI is Nitrox, and our goal is to get a final blend of 18% Oxgyen. To do this, we need to top up the tank with 36% Nitrox. Why? Because ½ a tank of 36% Oxygen has the same O2 content as a whole tank of 18% Oxgyen. From there, it’s a simple matter of looking up what  pressures are needed to blend 36% Nitrox at 1,500 PSI. Nitrox blending tables should show this, and most people who have done Nitrox filling will  know that 36% into a 3,000 PSI requires 570 PSI of Oxygen, so a 1,500 PSI fill would need ½ that which is 285 PSI.

So our 18/50 mix will need 1,500 PSI of He, 285 PSI of O2, and be topped off to 3,000 with 1,115 PSI of air. I contrived this example so that the numbers would work out conveniently for me, especially with exactly ½ the tank containing Helium. What about other blends?

If we were looking for a 21/40 mix, clearly we’d need 1,200 PSI of Helium. The other 1,800 PSI would contain some Nitrox blend. To figure out the Oxygen percentage, we divide the desired percentage of 21% by one minus the Helium fraction, so in this case it’s (1-.4) or 60%. This turns out to be EAN35. So you can look up a 35% mix in a 1,800 PSI tank for the amount of Oxygen and air that needs to be added. You can also use the Nitrox blending formula of (W-.21)/.79 x PSI  (where W is the percentage of Oxygen wanted) to calculate it. This works out to 319 PSI of Oxgyen with the remaining 881 PSI topped off with air.

Note that there are some blends that can’t be made The 4/80 mix, for instance, can’t be made exactly. I chose this in my example because  it is the mix that was used by David Shaw when he died cave diving in South Africa at a depth of 270 metres. The reason it can’t be made exactly from Oxygen and air is the remaining 20% of the mix that isn’t Helium is only 20% Oxygen, and this Nitrox mix can’t be blended with a combination of Oxygen and air. I’m  sure though, that in this case his diluent was just air, and the mix was 4.2% Oxygen, rather than exactly 4%.

So what he was diving was actually “Heliair”, the simplest Trimix blend around, made from combining Helium and air with no added Oxgyen. The disadvantage of this mix is that at the optimum MOD of Oxygen, usually considered to be a partial pressure of 1.4 (although many rebreather divers use 1.3, and some open circuit divers use 1.5 or 1.6 under ideal diving conditions or in deco), has the same END (Equivalent Narcotic Depth) as air  at the same O2 partial pressure. This is true at any depth as the ratio of Nitrogen to Oxygen is the same as air for any mix of Heliair.

Deon’s END was 46 metres or about 152 feet, which is greater than many divers would care to venture, although less than many others including me have regularly dived, and his PPO2 1.12, which is well within acceptable boundaries. You can see from this though that he was getting quite exposed to narcosis while being well within the acceptable limits for Oxygen Exposure (at least from a CNS perspective, it was scheduled to be a long dive and Pulmonary exposure would undoubtedly be a concern). This points out the problem with Heliair – long before you’re at your CNS limits you will be well-narked. This extreme example has other considerations, so don’t take this as saying that for this dive his mix was incorrect or that narcosis contributed to his accident.

DSAT Gas Blender October 15, 2009

Posted by Chris Sullivan in Training.
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I just took this course. The manual was well laid out and the exam was reasonably difficult but not too tough ( got 98%, after changing one answer from right to wrong). In addition to the classroom  stuff we took apart some tanks, cleaned  and inspected  them, reassembled, and filled them with Nitrox. There was nothing too surprising  except on 2 of the tanks there were hydrocarbon deposits showing up under the UV light on the threads. Fortunately my tank was free of them.

The course covers air station system design for oxygen rich environments, O2 cleaning, gas mixing, trimix, and various other components and represents a combination of several courses from other agencies (most separate trimix blending from nitrox) so is a good value. To become an instructor for this course after taking it, one either needs to take a special  instructor course, or do 50 mixes to +/- 1% and apply after a 6 month waiting period, in addition to being an open water instructor, of course.

My tank valve was a different design to the others.  Larger, more parts, metric sizes, and so on.  It’s a DIN valve vs. the usual yoke valves that on the store’s rental tanks.

The course also covers blending trimix, and comes with the DSAT gas mixing calculator, which makes the determination of how much of each gas to blend trivial. It doesn’t adjust for molecular size and intermolecular forces by using Van Der Waals equations or other esoteric methods so at higher pressures it would be  a little bit off for Trimix.

I think, though, that in practice it’s difficult for any low volume operation to follow all the  recommended practices 100%. With an O2 clean VIP running around $30 retail, it  would really be difficult to go through the  full procedure  economically. That’s where the experience of having practical methods to maintain a safe system really count.

When I get my card I’ll update  my bio on this blog.

Boat Divers October 14, 2009

Posted by Chris Sullivan in Dive Log.
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On Sunday (October 11th, 2009) 4 of us went out to dive some lesser known sites in Lake Simcoe. This is the first time, at least to my recollection, where I’ve been out diving on a private boat rather than one belonging to a charter operator.

Our problems started at the boat ramp, situated on the North shore of Kempenfelt Bay. The water level of the lake seemed lower than that for which the ramp was designed, so the back wheels of the van were in the water before the boat would float. The small dock near the ramp wasn’t out far enough into the water to be a suitable platform for embarkation, so the owner, Ken, moved it to a nearby public dock that was much more suitable and we met him there, unloading the gear down the hill.

While maneuvering near the dock, Ken decided to back up quickly. The inboard-outboard engine is quite powerful, and I had to throw the line I was holding in my hand back on to the boat. Unfortunately it slipped off, and fouled the prop, so Ken spent the next 45 minutes or so anchored 100′ away, finally donning his wet suit to dive down and free it.

The three passengers by that time were all dressed in dry suits and began loading equipment on board. As we were loading my doubles, we had them perched on the starboard  gunwhale while I tried to step into the boat. The constriction of the dry suit cramped my movement at exactly the wrong moment and I fell unceremoniously onto the floor of the boat without injury. Ken fortunately was able to keep the doubles steady long enough for me to scramble to my feet and help him with the heavy unit.

Michael loaded his next, and wearing the same type of dry suit as mine, did exactly the same thing, and was also unhurt. Rich, now wiser from the experience of his shipmates, was much more careful in the way he stepped down onto the boat.

The first site we wanted to visit was a long way off, and Ken didn’t inspire confidence by continually voicing his doubts about the amount of fuel he was carrying. His fuel gauge wasn’t all that reliable, it seems. We were also experiencing high winds, waves and cold temperatures to make the journey more interesting. When we were within 2 miles of the site, according the several GPS units we had with us, we found the waves were too much and with uncertain fuel and queasy stomachs we all heartily agreed with our captain that we should turn around.

The second site was in calmer water, being closer to the shore and somewhat sheltered from the wind, and by 3pm (almost 6 hours into the adventure) we managed to get wet, although we found nothing interesting on the bottom. It was desolate even by Lake Simcoe standards.

Once we made it back to the ramp, we unloaded on the large dock and spent about 1/2 an hour getting the boat onto the trailer. But as the wheels were off the concrete pad and onto the bottom the van couldn’t pull the trailer. Finally, pouring on the acceleration we managed to disable the trailer when it hit the ledge on the end of the pad (which we then measured as 5-6″ high).

This put us in another conundrum as to what to do, as the light was beginning to fade. We slid the boat off the trailer and into the water to moor it on the large dock, and then pulled the trailer up the hill, despite the fact the rear wheels on the left were now touching each other. We determined that the front axle had slipped backwards on the left hand side about 8-10″, so we loosened the u-bolt holding it in position and started whacking it with a 2×4 block of wood.

It made some encouraging movement, and by jacking up the back of the trailer and using the boat winch for additional persuasion, we finally moved it back into position. Not wanting to use the ramp again, Ken decided he would drive the boat into Barrie and use the public ramp there, which was much more friendly. I had to drive his van there, and the final insult (at least for me) that night was it took 10 minutes to get his boat key off his key ring. I was showing my impatience as it was now almost 7pm and I figured my wife would be on the phone to the lawyer to file the divorce papers by this time, but we made it the rest of the way without a problem and Mike volunteered to wait for Ken to arrive in the boat. I managed to get home by 8:30 with take-out food in hand and opened a bottle of wine to ease the pain of my long absence.

Rich and I were long gone by the time he made it in. He had indeed run out of gas on the way, and made the final leg using the small outboard motor, which also ran out of gas just as he was arriving. But the boat was loaded and that was that.

We all agreed that we’d learned a lot that day and are looking forward to trying again when the weather warms up next spring.

Equivalent Narcotic Depth October 13, 2009

Posted by Chris Sullivan in Technical Diving.
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I’m glad to see that the Wikipedia definition of Equivalent Narcotic Depth uses (1-FHe) instead of FN2 as the basis of the calculation. The difference between these two is that the older way of using the partial pressure of Nitrogen leaves out the current theory that Oxygen is more narcotic than Nitrogen, and the current practice of assuming that their narcotic potential is equivalent, as it is believed that in practice Oxygen is less narcotic than the theory would suggest due to partial metabolism by the body.

So how does this change the END? So let’s use 20/40 trimix like the Wikipedia example. With this mix, 60 metres should feel like 32 metres. Using the old formula, where Oxygen is treated as equivalent to Helium rather than Nitrogen, the END would be .40/.79*70-10, or just over 25 metres. That’s quite a difference.

I also found a web site that took into account the theoretical narcotic properties of Helium in one method of calculation, which is considerably less than Nitrogen. I’m not convinced that is valid as at some of the depths people are diving at now (over 200 metres), the Narcosis would be intolerable.

For instance, in the Deon Dreyer accident at Bushman’s Hole, he was diving at 270 metres with 4/80 trimix. If Helium was counted at 23% of the Narcotic effect of Nitrogen, his END would have been 97.5 metres! That’s almost double the value if Helium isn’t counted.

Solo Diver October 10, 2009

Posted by Chris Sullivan in Training.
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Scuba Diving International, commonly known as SDI, is the only agency that I know of that has a solo diver certification. SDI also has a well-known technical diving sister company called TDI, and the two agencies share a web site.

I’ve signed up for this course, after receiving an offer I couldn’t refuse from Brad at my local dive shop, and have reviewed the entire book, the “SDI Solo Diving Manual”. It is full of sensible advice, and sits about 1/3 of the way between normal recreational diving practices and the technical diving techniques I learned in the IANTD Advanced Nitrox Course and the DSAT Tec Deep Course. The bottom line is a higher level of dive planning – including gas planning, emphasis on self-control as a prerequisite to self-reliance, and redundant equipment including a secondary air source, reel and SMB, and a spare mask. I carry a reel, SMB and spare mask on almost all dives, solo or otherwise.

While I feel the content of the course was pretty good,  I was surprised by the number of errors in the book, ranging from poor use of commas (placing a comma between the subject and the verb, for instance) to mathematical errors (Conversion of metres to atmospheres by adding 1 to the depth and dividing by 10). At one point it casually introduces the concept of deep stops by recommending them to be added to the US Navy tables (good idea) without mentioning that the stop should be added to bottom time, as the Navy tables require a 30 foot/min ascent rate. Not that I would ever use the Navy tables unless I was in a real hurry to get out of the water for safety reasons. I’m not a super fit somewhat expendable 25 year-old with a recompression chamber available at all times.

Nevertheless, I’m looking forward to the course, and will write to SDI with my list of errata so they can hopefully do a better job with the next edition. One thing I like is that I have all the equipment I need already.