Well, it's been a while since I last posted and a bit has been done in the meantime, although it still hasn't hit the water yet (I've been very busy with work). I also made an absolutely fatal error in the build which I will share here in case anyone else comes across the same situation.
Where I left off with the pictures was just after putting the pre sealed ballast in the hull. After this the stern section starts having its equipment fitted. It starts off with the bellows which will take the brass rods for the tail planes.
This was actually a remarkably fiddly job with a pair of long nosed pliers trying to get the bellows which are deeper attached. There's less room to work within that access hatch than you might think.
Now here are the pushrods and the main drive battery, which is two 6v batteries linked in series to make one 12v unit. It's done this way to save space in what is a relatively small hull. The instruction manual says that the threaded rod ends should either be soldered or superglued. Here you can see that they have been soldered, but later one linkage did break so I then superglued it and it seems to be a good bond now. These rods are then passed through the bellows to be linked to the X-rudder linkages, which have been pre assembled.
Here are the pushrods in their final positions. Note that the rod closest to the hatch is bent- this is to stop the pushrod from flexing when the rudder is moved, which puts pressure on the bellows and can cause the rod to seize in place. Judging the angle is difficult, especially since the bend must be done in situ, as it will be very difficult if not impossible to feed the rod in from the stern section (or was when I tried).
Here's the dry side of the aft bulkhead after installation of the servo pushrods. Note that the clips put on the threaded end caps are out of focus.
Now this next step is where things went badly wrong, installing the propshaft. I followed the instruction book to the letter as was recommended and so I missed a key step which came back to haunt me later. To prevent confusion, I'm going to put the next photos in the order in which you SHOULD install this thing, not how I DID the first time. The error I made was very simple and anyone with a little more experience probably wouldn't have made it, I'm pretty sure.
Here you have the propshaft assembled but everything isn't quite put together. The coupling is very simple, just a piece of brass machined through with four grubscrew slots. Given the tech rack and stern bulkhead's precise machining, there shouldn't be any mis alignment of the motor and propshaft. Note you have to put the motor mounting plate on before linking the motor to the shaft, because that mounting plate is also where the shaft leaves the watertight compartment and has a rubber seal- if you push the threaded end of the shaft through, you will destroy the rubber seal and your boat will leak, a lot. Luckily the shaft is long enough that this plate doesn't get in the way when you're joining the shaft to the motor.
NOTE: the prop and spinner are attached in this photo. In the instructions, the prop is attached after the shaft is installed and here it will need to be removed to fit into the submarine. However, I strongly recommend at this stage putting the prop on and giving the prop in one hand and the motor in another a firm tug. This ensures that your motor and propshaft linkage are on properly and the shaft won't come out if you go into reverse.
It is important to do this check at this stage, because the brass linkage will fit snugly into the mounting plate and will be totally inaccessible without completely taking the stern to pieces if you do have a problem. I can't stress enough how much of a total pain that is. In my case I followed the instructions and essentially completed the entire sub. Then I had leak issues, which made me take the submarine to the clubhouse, where it emerged that my leak problems were caused by having too much silicone grease on the O-ring and it managed to go into the water, dive and emerge just as it's supposed to. Then I put it into reverse and the propshaft came loose. After taking the entire thing apart and putting it back together, lo and behold it's leaking again, caused by something I did taking it apart. If I'd tested the prop linkage at that much earlier point this sub would most likely have been sailing happily for a while (or something else might have come up, who knows).
Here's the propshaft with the motor mounting plate on and greased. Note how the motor and propshaft linkage is now inaccessible. the green grease is also pretty cool- when it's no longer visible on inspection it is time to grease again.
Now the motor is mounted, plugging the largest hull in the stern watertight bulkhead. I HIGHLY recommend a nut driver for this step, if you don't have one it is impossible to do by hand due to the depth and restrictive size of the compartment. I first put these nuts on with pliers and it took over an hour. With a good driver, it takes five minutes.
The wet half of the propshaft. Note how most of the rotating part of the propshaft is entirely exposed to the water. It probably cuts down grief with keeping it greased but I can't help but wonder what the hydrodynamics are like inside that wet compartment when it's going.
Next is installing the servos into the tech rack. Due to limited room and the fact you use the third hole from the centre, the end of the servo arm has to be cut off. Since there are two, here is a picture between an original arm and one I prepared earlier
(tm). The servos then literally snap into place in the tech rack.
Here's the watertight stern bulkhead with everything bar the tech rack support bars attached. The large pipe takes water in for the ballast tank. I found handy advice to run it under hot water immediately before installation to soften the end of the pipe, which makes it easier to slot over the brass collar by orders of magnitude. Again, due to depth and narrowness of the compartment you need to use pliers to do this which isn't the easiest thing in the world. The smaller tube routs to the pressure switch, which will hopefully return the sub to the surface if the model goes below 3m of depth, which runs the risk of pressure and other, more sinister unknowns killing the model and making it irretrievable under its' own power. This smaller lead is easier to install, but with pliers you do have to be wary of ripping it if you aren't gentle.
At this point the tech rack is joined to the stern section. Here a lot of things need to be done simultaneously- the ESC must be linked to the motor (which given the positions of the two bits of kit and the length of cable provided means the pliers come out again and you have to be very careful. I also found that the bullet connectors didn't have quite enough rubber coat to completely cover the connection, leaving a small golden strip visible so I wrapped each connection with electrical tape to prevent any unlikely short circuits (as said earlier, you want to disassemble the stern as infrequently as possible so mitigating issues before they arise is essential). The piping is connected to the routing in the tech rack and then finally the pushrods are connected to the servos. This is done last because the reach of the arms only gets to the final position of the servos, so the tech rack has to be physically bolted on for it to work.
There wasn't a lot of point trying to take photos of these steps because they're all pretty straightforward, even for a build as simple as this and given their nature getting photos of this work would be tricky.
With everything installed, this is what the sub looks like from the outside. Which is to say, identical to when I started! Picking the model up however there is now a very healthy weight to it which is immediately apparent.
Then the prop and spinner are screwed on and the dive planes are fitted. Take note, when the instructions say use only the tiniest drop of superglue, they mean it. Luckily, for most of these planes, the fit is tight enough that they can really go on without any glue at all, but if you do need to glue them as they're resin superglue will bond them to anything and in lightning time (something I somehow forgot from my many years of sci-fi modelling with resin). As a result, one of the tail fins (the lower starboard one) is about a millimetre further from the hull than it should be because it got momentarily stuck pushing it on and the superglue went off before I could push it in further. Every attempt to remove the fin have ended in failure so far and since it is only minor I probably won't try much more to fix it (unless there's a chemical I could use which doesn't harm plastic and resin but attacks superglue, in which case I might), for fear of damaging the submarine.
At this point you are ready to test the submarine. This is where I discovered the leaks, found the solution to the leaks, lost the propshaft, took everything apart, fixed the shaft, leaked again, took everything apart again thinking one of the water lines had come off (they hadn't), still leaking etc etc etc.
When I build up the will to go leak hunting again it will be time for trimming and I'll take photos of the trim weights and the completed tech rack
et al. 
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Topic: Engel Type 212A Build Log (Read 37911 times)