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Author Topic: Engel Type 212A Build Log  (Read 27121 times)

Jack D

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Re: Engel Type 212A Build Log
« Reply #75 on: April 20, 2016, 11:02:10 pm »

A relatively quick update.

I've installed the magnet switch in the stern and it works beautifully, it will allow me to test the seals in a clean environment and then turn the submarine off taking it to the pond, which limits the chances of dust getting in or something else which could cause the O ring to leak.
I've also tested the O ring again and the perpetual leaks were caused by using the wrong or too much lubricant. Perfectly dry the O ring works, but after being immersed and broken again, with water on the ring it will leak. I've found that E-45 hand cream actually helps it seal magnificently, although I have today ordered some silicone and sticky grease from Engel which are what they recommend using (alongside a much needed stand!).

The test tank trials did show some water getting in without any leaks apparent, but it could be the way I'm taking the sub apart after being in the water, it warrants further investigation. Hopefully the maiden voyage on the lake will be soon.
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thegrimreaper

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Re: Engel Type 212A Build Log
« Reply #76 on: April 21, 2016, 08:35:55 am »

I think I'd dispense with the pressure sensor.


Agree with Subculture neither my Lafayette , Typhoon or Nautilus have the pressure sensor connected.


regards Mark.
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Jack D

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Re: Engel Type 212A Build Log
« Reply #77 on: April 21, 2016, 11:47:15 pm »

At the moment I'll keep the pressure sensor in. When I've run the sub a fair number of times and I'm confident she won't start to flood unexpectedly I'll probably remove the sensor because tripping every few minutes will be a pain. For the time being though I like the added security it gives. I'm also wondering if there's some way to keep the depth sensor working while disabling internal sensors, although given it's in one unit I'll wager that it is unlikely.
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Jack D

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Re: Engel Type 212A Build Log
« Reply #78 on: April 27, 2016, 11:33:15 pm »

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.
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Subculture

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Re: Engel Type 212A Build Log
« Reply #79 on: April 27, 2016, 11:59:57 pm »

It isn't the tank at fault. Salt water is denser than fresh water, so the boat can be quite a bit more buoyant. You need to take a couple of ounces of lead along with you to counter that.

Jack D

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Re: Engel Type 212A Build Log
« Reply #80 on: April 28, 2016, 07:20:11 pm »

Haha, my late at night knackered wording didn't help there. I might try experimenting with some adjustable trim weights for fresh and salt water running, but honestly I don't expect to hold a signal much below periscope depth in Canoe Lake even with the antenna modifications and she will happily get to periscope depth as is so I'm tempted to leave it alone.

I'll have to see how the external antenna goes though- if it turns out I can get a signal to the bottom of the lake near the edge I'll certainly be re trimming for seawater. Just have to remember to take it out before I go somewhere like Chichester and end up donning my scuba gear to retrieve it :D
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Subculture

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Re: Engel Type 212A Build Log
« Reply #81 on: April 28, 2016, 09:28:32 pm »

Unless you can keep the aerial above water you can expect to lose the signal immediately when submerged in salt water. It's also very hard on exposed metal parts. I would seriously consider running a sacrificial anode if you run in salt water regularly.

Jack D

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Re: Engel Type 212A Build Log
« Reply #82 on: April 28, 2016, 09:35:00 pm »

The anode isn't a bad idea at all. I know Engel advertise their stuff as being almost totally corrosion resistant but I get the feeling that the prop at the very least will suffer badly and it doesn't hurt to be covered any way.
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derekwarner

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Re: Engel Type 212A Build Log
« Reply #83 on: April 28, 2016, 11:29:02 pm »

Jack.....back on 31 December 2014 we noted......

'O-ring's were designed to be a pressure energised seal element........they also necessarily rely on correctly dimensioned cavities, [compression] clearances & surface finishes to effect fluid tightness

One of the difficult things here is that both British & Australian Standards for o-ring cavities are based on a pressure application....[~~~200 Bar]...so are not necessarily suitable for static conditions of say 1 Bar or atmospheric conditions'


Now you believe the manufacturer is supplying an o-ring which is not the correct size....are you able to accurately measure the o-ring cavity dimension and nominate the corresponding bore dimension?..............we can look at these & back check nominate the best o-ring to suit the dimensions

Using a fluid based lubricant will assist in the guiding & hence compression of the o-ring during assembly, however too much lubricant should have little bearing in the water tight integrity of the joint......dry talcum powder can be used as an alternate

Mention was made of using an MVQ or silicone elastomer o-ring as being softer....according to universal Manufacturers Standards, MVQ elastomer is listed as 70 Shore hardness, along with NBR at 70 Shore........[although someone could substitute a common 90 Shore hardness NBR o-ring which are widely used because of the greater anti-extrusion properties]

The only downside with MVQ is that they are produced in far fewer size variants around that nominal size.....come back with the dimensions..................

Derek
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Derek Warner

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unbuiltnautilus

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Re: Engel Type 212A Build Log
« Reply #84 on: April 29, 2016, 09:51:33 am »

The replacement O-Ring was without a doubt very wrong in size, being more like 2mm cross section rather than the roughly 3mm cross section of the original. You could get your little finger under the O-Ring with the slack evident.
As far as the antenna is concerned, the plan is to use stainless braided cable used for fishing line, which has a plastic seal over it. This should prevent any earthing or corrosion issues. All that we will have to look at is the antenna connection point and the hook onto the back of the sail.
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