[PSUBS-MAILIST] my toes are wet at last

["Alec Smyth" <Alec.Smyth@compuware.com>]

Today, courtesy of Mark Ragan, I finally went from theory to practice in Snoopy, the K250 that I purchased from Dale Heinzig some months ago. Mark has a K250 as well, and lives only 40 minutes from my home on a quiet inlet of the Chesapeake. The inlet is ideal for testing subs, and since Mark has taught sub school there for some 20 years, his neighbors treat submarines like mine would treat lawn mowers -- there were absolutely no gawking onlookers to make one nervous. 

We launched from the trailer without a problem. I'd modified the trailer so a telescoping tongue gives me about 25 feet between car and sub. This was just enough to float off as the water began lapping at the tires. Nonetheless Mark was such a gentleman he insisted on wading into the icy water with the trailer so it would not fall off the ramp or otherwise get stuck "on his watch".

The first thing I did upon climbing in was a quick leak check, then motored around on the surface a bit. As reported by others, the speed is comparable to that of a kayak or canoe. The maneuverability is excellent, as you can use one or the other thruster, in forward or reverse, and in high or low speed. Snoopy is hard-wired with half-speed and full-speed, but frankly there's very little difference between the settings. 

I made a couple of attempts to submerge, adding more lead weights each time. Something is unfair about this... the skinnier the pilot, the more lead weights he has to carry around! Anyway, once the weight was right I did a couple of stationary, tethered dives right next to the dock, to which I was attached by a line so Mark could haul me up in case of trouble. We used Motorola walkie talkies for comms, and they worked until the dome was a foot or so under water. 

I was surprised how gradually the K250 submerges. Dale had mounted an air-bubble "clinometer" longitudinally inside the sail. This turned out to be an excellent idea for keeping the sub on an even keel as you submerge. When you open both ballast vent valves, the water pushes out the air and you slowly settle. With an eye on the clinometer, you momentarily shut one or the other vent valve to keep on an even keel. It takes about a minute for the ballast tanks to fill, and you can tell right away when they are full because the bubbles cease. But it's absolutely not the sudden transition one might expect from watching movies of military subs. One lesson I learned was to CLOSE the vent valves once the tanks are flooded. Although closing them at that time does nothing, it prevents me from forgetting to do so later on when I want to blow the tanks. 

It's quite interesting the first time the water level comes over your window on a submarine. At age 40, there aren't too many really basic "firsts" left to experience, like the first time you rode a bicycle, flew in a plane, or used scuba gear. But the moment your acrylic dome goes under is one of those experiences. As an engineer I tend to trust in machines, and as a diver I tend to be comfortable underwater. But if I was neither of those things, I could see myself becoming quite anxious!

Getting under required flooding both ballast and variable tanks. One good pointer Mark provided was to stop venting the variable the second the apex of the dome goes under. My first tendency was to keep venting a little too long, and I ended up a few pounds heavy. In that condition I would settle on the bottom. I could lift off and motor around by angling the thrusters downwards slightly. Applying Mark's rule, however, I found myself hovering just a couple of inches off the bottom and motoring with the thrusters level. This wasted less energy and didn't silt up the bottom as much.

While diving struck me as a gradual process, surfacing is all the opposite. Once you blow ballast, you are basically sitting in a cork. The boat rises and falls far above and below the normal waterline in a series of oscillations.  Looking at it on video afterwards, its almost comical. And that was from a depth of only a few feet. If you surface on VBT only, of course it is less dramatic. But still, the VBT gets the entire dome above water. If you were just surfacing to get your bearings, there's be no point wasting air on the ballast tanks.

I had only two very minor technical issues; a slow drip from a Swagelok fitting that evidently needs another quarter turn or so, and a very slow free flow from my emergency regulator. The latter was not audible, but the barometer picked it up and I noticed a hiss when opening the hatch. If left to build up this is a dangerous condition, and I've installed a dump valve for cabin over-pressure, but since I was down only a few minutes at a time the pressure didn't build up enough for me to have to use the valve. I'll just have to adjust that second stage to stop the bleed.

I am tremendously indebted to Dale, to Mark, and to the many other folks on here who have helped me out over the years. Thanks guys, really.


Alec









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