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Air Pressure September 27, 2011

Posted by Chris Sullivan in Equipment, Technical Diving.
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Around this time of year I need to blow the water out of my underground sprinkler system so it doesn’t burst during the winter freeze-up. I used to use a company to do it, until figuring out that I could save the money by doing it myself, with a return on investment of 1 year. The process is pretty simple, hook up a regular air-tool compressor to the outside hose bib, shut off the inside tap (lest my toilets explode), crank up the pressure on the compressor to 120psi (safe on my system, your mileage may vary) and program the controller for 1 minute on, 9 minutes off, and cycle it twice.

After finishing on Sunday I disconnected the hose from the compressor without bleeding it off. The hose then whipped around my porch for the next couple of minutes, whacking my ankle (without injury) in the process. This is food for sober thought when thinking about the pressures used in your typical scuba shop, with AL80s at 3000 psi, and compressors that have a safety shut off at 5,000. If a 120 psi hose can whip around menacingly, you can imagine what would happen at 3-5,000 psi.

Most of us learn just how dangerous a scuba tank can be. A recently fatality in Florida is yet another example. Let’s be careful out there!

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A Little Drift on the Lillie Parsons September 25, 2011

Posted by Chris Sullivan in Dive Log, Shipwrecks, Technical Diving.
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Labour Day Monday, 2011 – last dive of the weekend. I’d used my doubles down to 1800 PSI on a training dive on the Daryaw, but I also wanted to go deep on the second dive of the day, so Larry and I made a dive plan which was to drop to the bottom of the St. Lawrence and scoot along until one of us got down to 1000 PSI, leaving us lots of gas to make a slow ascent. We were expecting little or no decompression obligation but I took a reasonably bottle of 47% Nitrox along with me anyway.

The dive started at the Lillie Parsons, at the upstream end of Sparrow Island (there are a lot of wrecks in the St. Lawrence near the upstream ends of islands – go figure). There were about 12 of us on the boat. Some wanted to do the traditional dive, which is to do a lap around the wreck (which is around 50′ deep) then drift at about 40′ or so to a chain that hangs from a cove on the shore. I found out on the previous Saturday that the maximum depth of the chain+rope was 66 feet. Others wanted to drop down to 80-100′ and drift along a bit further.

There are several ways to get to the wreck. The first I learned was to drift on the surface to island in the spot where the current splits around the island and therefore is fairly calm. You can look underwater and see which way the particulate matter is moving to know where that is. Then you have two choices. One is to swim upstream then turn right with the current and run right into the wreck, the other is to find the chain from shore that leads directly to it. The third way is to just jump of the boat (parked 100 yds or so upstream) and follow the contour down from the island to the correct depth.

We’d no real interest in seeing the wreck so we just headed down. We both saw the end of the mast, which sticks out into the current, briefly as we drifted by, but couldn’t see any other part of the wreck. We didn’t exactly rocket down, but didn’t waste any time either. Usually at that spot I avoid using my dive light and just let my eyes get used to the gloom. No dice this time. At 164′ maximum depth I couldn’t see a thing, and had to use my light to avoid running into outcroppings of rock against the wall while also keeping the wall in sight so as not to drift into the channel. I also wanted to stay a few feet off the bottom which I could also not see. Basically if I didn’t shine a light on it, I didn’t see it.

After a few minutes Larry signaled he was down to 1000 psi (he had double 85s and started at 1500) so we did a nice easy ascent while still drifting along. We got into a calm spot at around 20′, so we found a good foothold at 15′ and we did a safety stop for a few minutes (me on my deco mix) before surfacing. The computer had indicated a 10′ stop for me during the dive but it was clear by the time we got to safety stop depth.

When we surfaced we were on the downstream end of Stovin Island, about 100′ from 4 of our other divers, so we swam over to them so we could get picked up as a group. To the credit of the local operators, a competitor of the operation we were using called over from their boat and said they’d radioed our boat and suggested we move to the end of the island so they’d have an easier pickup. It’s great to see a community (Brockville, Ontario) that looks out for each others’ divers.

Diving the Rothesay September 3, 2011

Posted by Chris Sullivan in Dive Log, Shipwrecks.
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Today (in Canadian Eastern Time) I went for a little dive on a St. Lawrence wreck call the Rothesay, a 193′ wooden side wheeler. The wreck isn’t in great condition, being in fairly shallow water and having been used for demolition training by the military, but it still intact enough to recognise its shape and to see part of the paddle wheel.

We’re up in Brockville for our annual warm (for Canada) water wreck diving weekend, and arrived a bit early to do this easy shore dive. What I really like was its accessibility. There are parking spaces, a couple of spots for changing, a Johnny on the spot, and steps down the shore. The dive site has information describing the wreck, and the start and end points of the 100 metre swim are marked with buoys. An underwater line runs from the shore to both buoys, but most people surface swim to the first buoy then cruise underwater to the wreck. The dropoff is quite gradual so we were about 20m out before putting our fins on.

The maximum depth was 30′ and total dive time of 40 minutes including swimming back and forth. I came back with 1500 psi but we had a new diver with us who went through her air pretty quick so the timing was about right for her.

All in all I’d say is quite worthwhile for an easy dive close to highway 401. There’s lots to see on the wreck including some largish fish, passageways to swim through (overhead environment but not really wreck penetration), and some boilers and other equipment. No pictures unfortunately as I put my camera battery in backwards. I’d forgotten that was possible.