1/48 scale Type VIIC U-201 build

[Monahan Steam Models]

Yes there have been a lot of rebranding of these servos with subtle differences. One big difference is where the wires exit the case. Some exit the side and some exit the bottom. I have examples of both of these.

[neitosub]

Cool stuff! From what I remember the servo horn screw hole is a blind hole, but this might vary depending on the version of the servo, I’ve seen so many rebrandings of these blue micro servos ;)

[Monahan Steam Models]

Thanks Nate,

It took a bit of head scratching before I came up with what you see. The terminals are marked positive, negative and signal but the squiggly line for signal didn’t turn out so good. Looks almost like the negative symbol LOL.

The servos in the photos are stock and are not water proofed yet. Just haven’t gotten around to that yet. Will probably water proof all the servos and a few extra replacements at the same time. I plan to fill them with either mineral oil or CorrosionX. Then I’ll dip them a few times in Flex seal up to the bottoms of the mounting tabs. I may or may not use a O-ring underneath the servo horn and some silicon sealant for the servo horn screw if it is not a blind hole.

Nick

[neitosub]

That’s a really sleek connector Nick, love the fact that you even printed in the positive and negative terminal markings! How did you waterproof the rear control surface servos? From what I see they look like the standard “Tower Pro 9G” servos. Is the servo compartment filled with silicone with an O-ring seal below the servo horn?

Nate

[Monahan Steam Models]

With the new sectional version of the WTC no longer having the wire pass through conduits in the central ballast tank between dry compartments, I needed to shift focus to designing a new “in the wet” wiring harness that would be water tight. I don’t like exposing conductors to chances of corrosion. What I am going for with the new wiring harness is a design that stays in place in the hull the majority of the time. As the build progresses this will hopefully make more sense with the way this boat is being built.

The original WTC had two conduits that passed through the ballast tank. One for the eight data or signal wires and the other for the 12v, 5v and ground power cables.

The toughest or tightest area to try to pass all these connections through is the aft end cap area. There is not a lot of room available between the aft WTC end cap and the motor/servo module that is mounted in the hull.



This is the area I’m referring to.



A better view with aft end cap removed.



With the original WTC design, I had already worked out the water proof twin pair of 3 conductor brushless motor bulkhead connections. To get power and signal to the rudder and stern plane servos I worked out using this water proof 4 pin connector in the center. Pins were for positive, negative and a pin each for the signals.



A view of the backside of the original WTC aft end cap. Life was all figured out at this point… Time to mess all that up!



Now that I needed more than just the four original pins to pass through the aft end cap, I swapped the connector out for this 17 pin version. This will handle the four original pins needed for the rudder and stern plane servos as well as the eight data signals needed for the forward compartment and five additional pins of which four will be used for communication with the Arduino unit while the WTC is sealed up. (Didn’t have that before. Will come in handy later)



View of the new 17 pin connector from the other side of the end cap.




I needed to come up with a compact water proof harness connection to fit into the tight space that was available in the aft area for all these new wires and still have easy connections for the aft servos. This is what I designed. It looks like the Munsters drag car coffin. The six 2mm bullet connections are for the two aft servos. Silicon tube will be slid over them to seal out the water.



I built a strain relief into the new connector housing for the main data cable.




Once I solder the connections for the six gold bullet pins this void area will be filled with potting resin to seal the harness and housing from water.



Here’s how it click connects onto the bulkhead connection.



Fits down in there pretty good.



With the brushless motor connections made up.



Top view down through the aft piston trim tank.

This was the worst of the figuring out that needed to be done for the harness design and packaging for the new WTC version and so far so good. The design allows the aft section of the WTC to slide back a quarter of an inch from the ballast and forward sections, disengaging it to be removed and the connections to be quickly unplugged without removing everything else.

Nick

[MFR1964]

Nick,

The Type XXIII has a kind of insert at the radial split, no pins needed, there is only one way to connect, shearforces are limited because of the insert, i use 8 magnets to keep things together, need about 8 kg of pulling straight to make it seperate.
Opening up happens to break it's back ( shearforce) then you can pull things apart, a pretty easy job, SD is retrieved without using tools, it was all designed no tools needed.
The Ko-Hyoteki was a difffent story, made the model myself, so had to figure out the pins and magnets, same force needed to open things up, yet again no tools needed, the SD is removed with some more effort due to the design, all connections on both are either magnets or lipseals.

Manfred.

[Monahan Steam Models]

Love the innovation Nick! Top notch stuff.

Thanks Bud!

I’d say the biggest win so far with the new design was having another crack at correcting the main ballast tank volume and CG placement along with the improved ballast venting and internal stay design on each section. There are other significant wins but those are the ones that make a big difference out of the gate.

Nick

[SubDude]

Love the innovation Nick! Top notch stuff.

[Monahan Steam Models]

Great looking setup.

Thanks Casey!

We’ll soon see if the effort to split up the WTC sections makes much of a difference in the ease of servicing the boat or not. LOL

Nick

[Das Boot]

Great looking setup.

[Monahan Steam Models]

Here is the new sectional version of the WTC. All the major components are now made and dry assembled.



The empty WTC with equipment shelves waiting for components.


The sections separated.



Side by side overall comparison of the original one piece tube WTC next to the new 3 section version.



Overhead view of the forward compartment. Slightly different layout of the components that will populate the upper shelf since the two servos have been removed.



Overhead comparison of the ballast tank sections.



Finally the overhead comparison of the aft sections. The aft equipment shelves are identical between the two designs. No changes we made. Just the rear end cap received some minor design changes and added the forward end cap.

The next step will be to transfer all the equipment from the original WTC into the the forward and aft sections of the newer version.

Nick

[Monahan Steam Models]

Manfred,

Yes the pin and magnet connections work great for the reasons you point out. I believe your Type XXIII also uses this system for the vertical split?

Yes just the aft electronic unit will need to be removed regularly to access the batteries so they can be removed for charging. The aft WTC unit and the forward WTC unit each have a port on them for pressure testing for leaks prior to running and for ventilation during storage.

When I did the redesign of the WTC, I shortened the aft end of main ballast tank by almost 32mm. This brings the CG of the ballast tank to be almost exactly centered under the tower. Capacity changed from 631ml to 500ml.

Nick

[MFR1964]

Nick.

Smart thinking, connecting those WTC elements with pin and magnets, pins will counteract the shear forces and the magnets keep them on their place, pretty much the same as i did with the hull of the Ko-Hyoteki.
So, only the electronic unit is the one you want to remove on a regular base?

Manfred.

[trout]

I Love it!

[Monahan Steam Models]

Here’s the finished dry mocked up main central ballast tank for the U-201 project. This is the first of three new modules that will make up the WTC.



At either end of the ballast tank are 4 stainless steel alignment dowels and four magnets situated in both bulkheads. The bulkhead for the mating WTC module has four dowel pin sockets and four magnets.



The working guts of the ballast tank are mounted in the Aft bulkhead.



One of the mating bulkheads clicked into place on the aft ballast tank bulkhead. Very solid and secure connection.



Another view of the same. Need to remake the silicon vent valve piece. Although it seals and works well, it looks like crap because I cut it to size in a hurry and did a sloppy job but hey it works great still.

Staring work on the forward and aft WTC modules next. Then hopefully back to the main boat build.

Nick