Well, a bit of an update. I and Unbuiltnautilus took a really good look at this tub over the course of a couple of weekends and found some interesting stuff. The leak in the O ring always comes from the same place, but if you fit the lock in any position other than the one it's supposed to (so the ends are out of line with each other) the seal doesn't leak at all. While rotating the tech rack to find the wrong position to lock in the O ring, the forward ballast feed got snagged on something and was tugged loose, resulting in a somewhat rapid stern first sinking in the test tank shortly after. Luckily being fresh water a very fast retrieval and thorough drying out ensured no damage.
Also, the O rings listed as direct replacements from Engel are too big- the outer diameter is probably the same, but the thickness of the ring is much less so it doesn't sit in the allotted groove on the locking ring. Perhaps since the transition from the kit to the pre assembled hull version the locking ring has changed slightly?
On the fore half of the locking ring, we found a groove next to one of the projecting guiding sections. You can see it as a slightly whiter line (trying to photo white on shiny white is HARD) in the middle of the photo here. This position roughly corresponds to where the trouble has always been and due to it's position in front of the guiding point and its' depth is unlikely to be damage from sliding the tech rack in and out and is likely a minor machining defect, which is a pain in the proverbial.
Still, after something like four hours of trial and error, thorough cleaning of the entire assembly
and sacrifices to the dark gods of chaos the O ring finally sealed and wasn't blowing bubbles in the test tank. So, I turned the sub off using the magnets and we rushed to the lake as soon as possible, hoping that whatever was holding the seal true wouldn't slip in the meantime.
With the sun slowly setting on a freezing day in late April, the 212 went into some proper water for the first time.
She ran fairly well, but on the surface your speed is heavily restricted because above a relatively low RPM the prop starts frothing up the water and blowing bubbles which doesn't help at all. The boat also suffered from some pretty severe glitching issues not far from shore- likely because the aerial is situated inside the pressure hull (which is almost entirely submerged) fairly low down. My local lake is salt water, which is notoriously bad for radio signals.
This was expected, I was gauging how well the default antenna will do- I will be extending it out at the stern so it hooks to the back of the sail in a relatively realistic manner. Hopefully this will give excellent surface performance at least while looking good. The odd time where I managed to just about submerge, through dynamic diving in reverse of all things, this submarine goes FAST and will actually start to plane under the right circumstances. These only managed to last a handful of seconds due to signal loss and the fact that a planing X rudder is useless for steering!
The piston tank doesn't work very well in salt water and needs to partially dynamically dive, which isn't at all surprising. Unfortunately after dynamic diving signal loss was almost instant so she slowly rose to the surface before automatically blowing the tanks.
Unbuiltnautilus was running his (much nicer looking) type 7 and we got a nice comparison of scale and look of the models in the water together. It's also an amusing look at how diesel electric submarines in the German navy progressed over seventy odd years.
Finally a shot by the edge of the lake after a fairly successful maiden voyage. To my continuing surprise, the O ring held out throughout the run (at least an hour) and there was no water inside the sub whatsoever.