Back in the Pool February 9, 2013
Posted by Chris Sullivan in Dive Log, Training.Tags: Dive Training, Diving, Enriched Air, Nitrox, SCUBA, Scuba Diving, Scuba Instructor, Scuba Training, Sport
add a comment
It’s been a while, maybe almost a year, since I did any pool training. I could have done some of the small things a bit better, but overall it went great and we were pleased. The students were all great and none had any undue anxiety.
Maybe there’s more instructing in the cards for me this year. For once I feel like doing it again. Or maybe it was just the energizing effect of the Nitrox I was breathing (although those effects are not proven, of course).
We had 10 students, two instructors, 3 divemasters, and 3 divemasters in training. Made it easy, even though the DMiTs were doing some of their own exercises.
Another Apeks Quantum Failure September 9, 2012
Posted by Chris Sullivan in Equipment.Tags: Adventure, Apeks, Apeks Quantum, Brockville, Dive Computer, Diving, Enriched Air, Nitrox, Outdoors, SCUBA, Scuba Diving, Scuba Equipment, Sport
2 comments
My replacement Apeks Quantum failed less than a year after I received it. It’s great that I get a new one but it costs about $60 in shipping and handling each time so it’s getting to be pretty irritating. This time, it decided to start eating batteries. I noticed at the beginning of summer it needed a new battery even though it was only about 6 months old. Then again on last weekend’s dive it was too weak to dive it. I happened to have a brand new replacement with me and used it on the next day’s dive on the Oconto, but on the surface interval it was obviously dying again so I didn’t use it on the Kinghorn later than day and took it to Divetech where they said it could be replaced for another $60.
I think when I get the replacement I’ll sell it to someone who doesn’t read this blog and maybe even spring for the new Shearwater Petrel. That would give me two functionally identical computers and I would no longer need to carry decompression tables.
Apparently the Quantum is made by Seiko, and is also rebranded under several other manufacturers’ names including Dive-Rite, although though don’t seem to carry it any more but have a 3-gas model that looks similar. The Tusa Hunter looks identical, but the Cressi Archimede II is a bit more stylish but recognizably the same design. Cressi always seems to be more stylish if you’re into that – I’m not – and their motto is “Scuba Diving in Style”.
I’ve reset more bent Quantums (or equivalents) than I can count, usually because the diver using it as a backup computer didn’t figure out how to switch to the deco gas. That happened to me once too. The trick is to hold the left button down for longer than you think is necessary. If you don’t hold it down long enough, it will switch back to your back gas.
The other Quantum trick is that after a reset it goes into metric. If you dive in Imperial units you need to go to the DIVE/GAGE screen and hold the left and right buttons down for 5 or more seconds.
Recreational Diving with a Shearwater Predator March 7, 2011
Posted by Chris Sullivan in Equipment, Technical Diving.Tags: Adventure, Apeks, Apeks Quantum, Cochran Computer, Cozumel, DCS, Decompression, Dive Computer, Diving, Enriched Air, Gradient Factors, Nitrox, Outdoors, Presbyopia, SCUBA, Scuba Diving, Scuba Equipment, Shearwater Predator, Shearwater Pursuit, Sport, Technical Diving, Trimix
add a comment
My second Apeks Quantum developed a problem last summer. The first one just died, but this one has developed the common problem (that my friends have seen) which is that the depth gauge becomes unreliable. Mine will suddenly jump to 10 feet shallower than I am, beeping mightily about the astronomical ascent rate. So while I’d normally take the Quantum on a trip where the water is warm and clear, with purely recreational dives, I elected to take my tech diving computer, a Shearwater Predator, instead.
The Predator is a great dive computer. Mine used to be a Shearwater Pursuit and was upgraded once the Predator was introduced. The main differences between the two are the OLED colour display (vs. LCD monochrome) and the Bluetooth communications to the (free!) logging program (vs. Infrared). Both features make a big difference to the operation of the computer, especially the nice bright OLED display on someone whose close-up vision isn’t quite as good as it used to be due to Presbyopia.
Predator’s have technical diving features like multiple mixed gases (5 gases for the open circuit version, 5 more for the close-circuit version), flexibility for decompression schedules, underwater gas switches and changes, etc. It lacks features that recreational computers have, especially the audible alerts and the safety stop counter. I don’t mind missing the audible alerts. I’m good at scanning my computer and other gear. Also, I like to guess what I’m going to see before I look at the computer and my air supply, so I develop a good mental picture of my situation.
I use the Predator with a conservative decompression algorithm (GF 30/85, which is actually the default). The Quantum, at least for the NDL calculation, is less conservative and my diving buddies figure it’s around GF 88/88). The tough guys at in the dive club who use Cochran Computers have them set to about 100/100, by the looks of it. The 30/85 setting means that it will go into mandatory deco stops sooner than most of its recreational counterparts. So unlike the rules that new divers are given, if you use a computer like this you either have to abide by a very short NDL or accept the deco stops.
It’s probably no surprise that I usually do the latter. In the 18 dives I logged in Cozumel I didn’t go past 6 minutes total decompression obligation. Most of the time it was 2-3 minutes, sometimes nothing. It is my belief that a 3 minute 10′ deco stop with a conservative algorithm is more or less equivalent to a safety stop. If miss, the chances of DCS are greater but that’s also true if you miss the safety stop. So in effect, I’m just getting the additional discipline of a safety stop that my computer calls mandatory. Once I’m done the stop(s), I’ll stay a while longer to get some additional safety margin or surface – slowly of course.
Getting well into deco is an entirely different matter. 5 minutes is about all I’ll do with recreational equipment. If I have to escape to the surface I’m probably going to be OK, which is as much as you can say for missing the safety stop on a less conservative computer. Any further pushing of the limits means carrying additional redundancy to make sure that I have the means to complete the decompression under all foreseeable circumstances. That’s why we have technical diving training.
Disclaimer: This is what I do. You need to understand all the facts and risks to make your own decisions about what level of risk is acceptable to you. I certify that this level of risk is acceptable to me at the time of writing, and that’s all.
Cozumel 2011 Day 4 – Cantarell Reef March 2, 2011
Posted by Chris Sullivan in Dive Log.Tags: Adventure, Blue XT Sea, Cantarell Reef, Christi Courtney, Cozumel, Decompression, Diving, Drift Diving, Enriched Air, Lion Fish, Nitrox, Outdoors, Scorpion Fish, Scorpionfish, SCUBA, Scuba Diving, Sport
add a comment
Today were the last dives with Joe and Grunt, and I’d agreed to take a taxi ($16 for gringos) from the Occidental Grand Hotel to the Marina (La Caleta) so that we could dive the reefs north of San Miguel. The first of these was Cantarell Reef, which on my map is called “Eagle Ray Reef”. When I dove it two years ago there were tons of them, but you never know whether they’ll show up or not, and this time they didn’t.
Blue XT Sea’s owner, Christi Courtney, also showed up for the dive, as she’d known Joe and Grunt on-line for several years but never met them. So there were 6 of us the on the dive, including our guide Pedro, and we dropped down into the current, sometimes quite strong, sometimes almost non-existent. All of us from time to time grabbed a handy Sponge to keep the group together. Some divers view this practice dimly as it is interfering with the marine life, but until I find out differently I believe there is little or no damage done to a big Sponge if it is held gently. It might be worth looking inside the Sponge before grabbing it, though, as you never know what might be in there!
Lion Fish in Sponge
The picture above was actually from San Juan Reef about an hour later, but it fits better in the story here… At one point, one of the divers, Joe I think, was hanging on to a sponge and noticed that he was inches away from a Scorpion Fish. These remarkable creatures are so well camouflaged I bet many people wouldn’t notice it in this picture unless told it was there.
Scorpionfish at Cantarell
Again we saw Juvenile Spotted Drums but the pictures aren’t worth posting here. Once more the shutter lag on my camera made it difficult to frame them well.
I hit a max of 108’ on the dive and the majority of the dive was fairly deep, so after 36 minutes bottom time I had 6 minutes of deco at 10’ on my computer (the 20’ stop cleared well before I got there). No one else went into deco because they were all diving Nitrox – Jackie because she always did, while Joe and Grunt decided to because they were flying the next day.
Enriched Air Nitrox Formulas February 28, 2011
Posted by Chris Sullivan in Technical Diving, Training.Tags: Adventure, Diving, Enriched Air, Nitrox, Outdoors, SCUBA, Scuba Diving, Scuba Training, Sport, Training
add a comment
Formulas for Nitrox are used for several purposes:
- Calculating the Equivalent Air Depth (EAD) to allow the use of standard Air tables to calculated no decompression limits, repetitive groups, or decompression schedules.
- Calculating the best or optimum mix for a given depth
- Calculating the maximum or contingency depth for a given mix to minimize risk of CNS Oxygen Toxicity
- Calculating the oxygen exposure for managing Pulmonary Oxygen Toxicity
- There are also formulas for partial pressure filling of tanks, which determine how much Oxygen needs to be put in before topping up with air. A more difficult problem is how much Nitrox to drain from a tank before topping off with air in order to reduce the fraction of O2 in the mix.
In basic Nitrox training we’re given the formulas for 1-3, and a table to manage 4 in recreational diving situations. The PADI table uses the NOAA or “CNS” clock only, with no surface interval credit. Surface interval credit makes sense in technical diving when we’re managing pulmonary toxicity using the Repex method, but when using one table to manage both I’m not convinced that it would be wise to apply it.
Even in basic training, I usually like to point out why the formulas work, instead of using rote learning. I first starting doing this when I took the course myself in the Turks and Caicos in 2005, and found that the understand helps me both remember the formulas (which I’ve never been good at) and to catch errors in my calculations.
Except in case 5, all of the formulas relate to the pressure of Nitrogen or Oxygen in Absolute Atmospheres. Everything that in Imperial divides, multiplies, adds or subtracts 33 (or 34 in fresh water) is converting between gauge and absolute atmospheres, and the formulas themselves are much easier to remember in ATA than in ATG.
MOD Memory Aid September 17, 2010
Posted by Chris Sullivan in Technical Diving, Training.Tags: Adventure, Dive Training, Diving, Enriched Air, Nitrox, Outdoors, SCUBA, Scuba Diving, Scuba Instructor, Scuba Training, Technical Diving, Training
add a comment
Maximum Operating Depth and Contingency Operating Depths for Nitrox diving are defined (by most) as the depths you reach PP02 of 1.4 and 1.6 respectively, indicating the recommended safe limits for continuous Oxygen exposure during the working and deco portion of a dive.
When I was teaching a Tec 40 class we were discuss MODs and other depth and pressure related calculations and I was using the formulas to explain the principles behind the math, the instructor mentioned Daltons’ Diamond, which I had to confess not remembering. It looks like this:
/\ / \ /PPO2\ /______\ / | \ /Depth| FO2\ /______|_____\
It says that Depth*FO2=PP02, PPO2/Depth=Fo2, and PP02/FO2=Depth. The trick is that depth is in Absolute Atmospheres, so you need to divide FSW (feet of sea water) by 33, FFW (feet of fresh water) by 34, MFW (metres of fresh water) by 10, etc, then add 1. For instance, 50% mix at 33 feet is FO2=.5, Depth=2, so PP02=1 (and safe).
The memory aid is simple for people who used computers, and useless for those who do not. The triangle is made up of the first initials PDF (PPO2, Depth and FO2), which is the file format used by Adobe Acrobat. Once I noticed it I never forgot it, and neither do my computer-using students.
Tec 40, First impressions April 8, 2010
Posted by Chris Sullivan in Technical Diving, Training.Tags: Adventure, Decompression, Dive Training, Diving, DSAT, Enriched Air, Nitrox, Outdoors, PADI, SCUBA, Scuba Diving, Scuba Instructor, Sport, Technical Diving, Training
add a comment
The DSAT Tec Deep course I took a 3 years ago has been split into 3. The course is essentially the same when you put all 3 modules together, except that there are now incremental certifications on the way to the full 50 metre/165 foot, 100% O2, 2 deco bottle certification.
The 3 courses are Tec 40, Tec 45, and Tec 50, referring to the depth limits in metres for each level. My local dive shop just started a Tec 40 course, we me as the certified assistant. Each level consists of 1 confined water dive and 3 open water dives.
Tec 40 retains the 40 metre recreational limit, but allows up to 10 minutes of unaccelerated decompression, and enriched air mixes up to 50%.
Tec 45 goes a little deeper and permits a single deco gas up to 100%, while Tec 50 teaches two gas decompression (something I have found fairly useless in most (but definitely not all) air diving scenarios.
There are a few loose ends and contradictions. The knowledge reviews are in separate handouts which jump back and forth in the manual, which hasn’t changed from the original course. Worse, there are places where the standards contradict themselves. One that we’ve already run into in Tec 40 says in one place that deco gas carried by students can never exceed 1.4 PP02 at the deepest part of the dive, while another says that if students are carrying mixes that are beyond 1.4 PP02 for decompression to make sure to remind them of the hazard and proper procedures.
Given that the course is supposed to allow for up to 50% Oxygen to add conservatism to decompression (as we are not talking about accelerated decompression), restricting to 1.4 means the dive can’t exceed about 60′, which renders it useless for practical purposes.
Hopefully these issues will get sorted out with time, and the student materials will catch up with the curriculum. Whilst the Tec Deep had the advantage of a cost-effective way to go through what would be 3 courses with any of the other agencies, the new packaging seems popular with many of the students, some of whom find committing to the entire program to be a bit daunting.
Promotion December 22, 2009
Posted by Chris Sullivan in Training.Tags: Adventure, Dive Training, Diving, Dry Suit, DSAT, Enriched Air, Nitrox, Outdoors, PADI, SCUBA, Scuba Diving, Scuba Instructor, Scuba Training, Sport, Technical Diving, Training, Wreck Diving
add a comment
I certified 3 new divers on my recent trip to the Florida Keys. One was an advanced open water diver and two were in the deep specialty. This allowed me to upgrade my PADI status to Master Scuba Diver Trainer (MSDT), catching up with my fellow instructors.
One benefit of MSDT are that you can apply directly to PADI for specialty instructor ratings, which I did immediately for everything for which I qualified. I’ve heard of instructors doing this without the necessary 20 dives “in the specialty” but I’ve been honest. The biggest temptation was night diving, of which I’ve done a limited amount but have more experience in equivalently dark surrounding during daylight hours. Some of the ratings seem more in the “card collector” category but others will be useful as long I can find students. I’m looking forward to teaching underwater navigation for instance, as this is one of the key diving skills.
MSDT is also a prerequisite for some other things, most notably technical diving instruction. I’ve a long way to go in this, having to act as an assistant to another instructor, getting a few more Nitrox/Deep certifications, and some more deep staged decompression dives in but it will all come together in a year or two I think.
So at any rate I’ve now earned 14 specialty instructor ratings, which are:
- Deep Diver
- Digital U/W Photographer
- Drift Diver
- Dry Suit Diver
- Enriched Air
- Emergency Oxygen Provider
- Wreck Diver
- AWARE Fish ID
- Boat Diver
- Multilevel Diver
- U/W Naturalist
- U/W Navigator
- Search & Recovery Diver
- U/W Photographer
Some of the dives I used to qualify for Navigation and Search & Recovery Diver were looking for things I’d lost on the bottom of the Lake.
Diving the Spiegel Grove December 7, 2009
Posted by Chris Sullivan in Dive Log, Shipwrecks, Technical Diving.Tags: Adventure, Decompression, Dive Computer, Diving, Enriched Air, Nitrox, SCUBA, Scuba Diving, Shipwreck, Spiegel Grove, Sport, Technical Diving, Wreck Diving
add a comment
The first dive near Key Largo on our club trip was the Spiegel Grove. This was the first and only dive I did on double tanks, which meant we had a good long dive and I felt more comfortable on the long swim throughs. Here’s a video of the most interesting one, according to our charter operator, Conch Republic. This video covers most of the swim through, although it took the first 20 feet or so to get the camera sorted out for video.
A minor source of embarrassment was forgetting to set my computer to Nitrox until 16 minutes into the dive as you can see in the log. This caused it to calculate longer decompression than was required but I didn’t mind hanging out on the line. Rich wondered what the hell I was doing as he had little or no obligation whatsoever. It was definitely less of an issue than diving a Nitrox profile on air.
New Shearwater Desktop Software November 13, 2009
Posted by Chris Sullivan in Equipment, Technical Diving.Tags: Adventure, Brockville, Decompression, Dive Computer, Diving, Enriched Air, Nitrox, Outdoors, SCUBA, Scuba Diving, Scuba Equipment, Scuba Instructor, Shearwater Desktop, Shearwater Predator, Shearwater Pursuit, Shearwater Research, Shipwreck, Sport, St. Lawrence River, Technical Diving
add a comment
I just downloaded and installed Version 0.9.9 . I was wondering why it wasn’t released as Version 1, but found out the next day that Version 1 had been released. The first snag I ran into was trying to move the dives from my beta version 0.9.3 to the current version didn’t work.
Reloading worked fine, although dives 1 and 2 are lost as I’d exceeded the maximum of 32. New features appear to be dive export and print. I was disappointed that a double-click on the list of dives doesn’t bring up the details like it did in the beta version. Not sure why that was taken out. You have to go to the menu bar and select “dive graph” to see it.
The Print function is a definite improvement over doing screen grabs like I’ve used in the past for this blog. It puts the graph at the top of the page and the details at the bottom, which I think is a nice layout. I printed one of my dives to PDF for your amusement. One minor nuisance is that you have to save you details before they’ll show up in the print function.
As for the export function I have no real use for it, but it will spit all the data from the log in either csv or xml formats, just in case there’s some useful analysis to perform on it. Here’s a piece of the xml detail.
You can see that I’m in mandatory deco (NoDeco=0) and that I’m breathing EAN71 and the water temperature is 71 degrees Fahrenheit. I’m currently on the 20′ stop at an actual depth of 26′. Some of the information here, like the mix, is recorded in the details but not accessible through the program’s user interface. I would have liked the breathing gases to be recorded. The details allow you to enter the breathing gas (presumably the back gas) manually. The software however is quite useful and is also a free download, so I’m willing to wait for all my favourite features.
There’s also a header record that shows about 25 parameters like the start time, start and end battery voltage, and other things.
An odd thing about the dive list is that when I did my download, dives 34 and 35 were at the top of the list, which 3-33 followed them in numerical order. I’m not sure why, but I wonder whether it’s a reflection of how the dives are stored in the computer. However, clicking once on the dive # column header set them up in their proper order, while clicking again puts them in reverse order.
Chronicle of an older diver 