1/48 scale Type VIIC U-201 build

[Monahan Steam Models]

Well I managed to get project Flying Spaghetti Monster transferred over to the new forward water tight section. It’s in the initial assembly stage. Will need to break some of it down to add sealant to some components for final assembly and finish connecting wires to the 17 pin data bulkhead plug.



I am already enjoying the modular style of each compartment with more components being fixed into the hull not needing to be removed. The way the forward compartment end cap clicks into place with the forward alignment dowels in the hull is easy and everything feels rock solid.



View of the equipment installed on the upper shelf. Slightly different arrangement than the original design with the servos removed and the LPB now moved to the center. The eight color ribbon cable will be replaced and routed to the 17 pin data plug. So that will be a much cleaner look.



The underside of the lower shelf that holds the trim tank pumps is less busy than the original design since the power cable connection and harness has been removed.



Here’s a view of the forward end cap. The counter sunk wells around the brass nipples are for the flexible potting epoxy to fill.



Overall view of what the new forward dry compartment looks like currently.

Do those of you following this build enjoy these smaller more frequent progress updates or do you prefer less frequent but more major milestone updates?

Nick

[SubDude]

Smaller more frequent...really liking the updates.

[Bob Gato]

You tend to give us more information from smaller updates- Also easier to eat the elephant one bite at a time -BG

[rwtdiver]

Nick,

I have a question for you. Dose the Arkmodel Vll kit come with the prop shafts, and if so, what size they are? I know the 80 mm WTC that I have coming for my boat has a 4 mm dual shaft.

Thank you nick,

Rob
"Firemen can stand the heat"

[Monahan Steam Models]

Nick,

I have a question for you. Dose the Arkmodel Vll kit come with the prop shafts, and if so, what size they are? I know the 80 mm WTC that I have coming for my boat has a 4 mm dual shaft.

Thank you nick,

Rob
"Firemen can stand the heat"

Yes the Arkmodel type VII that I purchased from Bob did include the 4mm prop shafts. The stuffing boxes that come with the kit are nylon tube and are junk. I replaced them with stuffing boxes made from K&S .250” OD brass tube and oil embedded bronze bushings. The bushings had a 5/32” bore and a 7/32” OD. The bore of the bushings was opened up to 4mm with a high speed steel multi-flute ream.



Here are the bushings and the part number.

I keep the bushings in place in the tube with blue locktite applied to the OD of the bushing prior to inserting it into the brass tube. The bosses that are molded into the Arkmodel hull for the original nylon prop shaft tubes have an ID of 6mm or .236”. These were opened up a couple thousands at a time with a series of reams till I arrived at a ID of .250”. You could open the ID up more for a looser fit or to have some play to get the new stuffing boxes aligned with the outer supports and then glue them in place also.

Part of the reason I did it the way that I have is during this whole build, I have been measuring and documenting all the critical features of the hull in CAD trying not to disturb the alignment or placement of the original moldings. This allows me to know in a 3D environment where everything is in relation to other features. Comes in really handy when designing the all the new junk that I’ve been putting into the build. LOL! Anyways, hope this helps.

Nick

[rwtdiver]

Thank you, Nick,

It certainly does help! You sure do things the right way. I cannot believe what you are doing to your Vll, and the quality in the design and the manufacturing of the components. "Perfection in motion"

If I can just get all control surfaces to work properly, and have the boat operate and descend to periscope depth, then I have achieved my goal. I am going to follow the YouTube that Bob has out on how he weathered and applied the finished his Vll. This will be my first true submarine weathering process that I have done, so I will look forward to that as well.

Thank you again, Nick. I do appreciate your help, advice, and expertise.

Rob
"Firemen can stand the heat"

[Monahan Steam Models]

I feel like a dung beetle pushing an elephant turd up a hill with this build. The small things that make a difference I guess. Finally got the forward dive planes working again with the new servo in the wet design.



Kept the magnetic coupler design as it is still relevant for quickly removing the forward servo equipment mount as a unit without pulling the whole launch tube assembly out too.

Here is a short video of it working. https://youtu.be/TikVaWcqAxA

The servo is not waterproofed yet and I plan to upgrade the bow plane cross shaft to something similar to what I did for the aft planes but hey it’s progress so far.

At this point, all the control surfaces are functional and the props spin. The torpedo systems are functional and the new WTC is almost complete. The original design worked great so the new one should be also good. Still lots of little details to address before the cosmetic part of the build can start hence the uphill turd battle still. It’s getting there.

Nick

[RCSubGuy]

Nick,


Maybe I missed something in the thread, but what is the assembly that the servo is bolted to? Is that all for the sake of creating linear movement for the forward dive plane linkage shaft? My gut says no, and you likely explained it earlier, so sorry if I missed something.


Bob

[Monahan Steam Models]

Bob,

The mount assembly for the servo is somewhat of an artifact and a design compromise left over from the way that I had originally chose to locate the components in the hull using the first WTC. Post #188 goes into some explanation of what all it does.

In a short summary, it holds the servo and allows me to still use the original linear forward plane linkage I came up with last year. It also holds the adjustable pressure regulator for the torpedo solenoids. It will aid in keeping the forward data cable connection in place from being bumped around.

Most importantly it locks the forward end of the new WTC in place in the hull while also pulling that area of the hull halves back into the original shape and location with the use of dowel pins. (The horizontal waterline cut caused the saddle tank area to spread apart a small amount.)

Nick

[Monahan Steam Models]

Yesterday I started experimenting with making the servos waterproof. This was basically taking it the servo apart to rtv the different sections of the case together and make additional holes between sections of the case to allow mineral oil to fill the cavities and air to escape. Got the bulk of the air out but was still left with a couple tiny air bubbles trapped inside. The good news is the servo still works and hasn’t lost a drop of oil in the last 24 hours.

Today I am at it, trying again.



First I disassembled the servo and soaked everything in a jar of 99.9% isopropyl alcohol to remove oils and grease.



After the parts soaked I removed them and dried them off.



The motor’s case has holes in it, but they are blocked off by the plastic servo case.



To allow oil to flow in and air to flow out of the motor, I drilled small holes through the plastic servo casing.



Sealant is added to the edges of the servo housing sections using a syringe filled with black RTV gasket sealant.



Example of the sealant bead applied to the housing edge.



Next I drilled a 1/4” hole in the center of the servo case. This is for adding a thin rubber diaphragm that will act to equalize pressure internally with outside pressure .This feature is thanks to David M suggestion for it’s addition.



Here are the 3/8” diameter rubber diaphragm disks punch out from a party balloon.



A bead of RTV is used to glue the rubber “party” diaphragm to the case.



Here’s the servo reassembled waiting to be filled with mineral oil. I’m going to wait to do so until the RTV has had time to fully cure.

Nick

[Monahan Steam Models]

This morning I continued experimenting with the water proofing attempts with the SG90 style servos. Now that the RTV sealant used yesterday had overnight to cure, I could move on with the next steps.


The first step today was to replace the standard type connectors on the servo wires with 2mm bullet style types.



These were then sealed up with heat shrink tubing that has heat activated glue inside them. Water or oil will travel through the wires if measures are not taken to seal the ends. I’d rather solder the connections on now than try to do so when they might be filled with oil.



Once the wire connections were completed, the next step was to begin filling the servo with mineral oil with the lower hole that was drilled into the case while the opposite upper hole allows air to escape. The servo was filled as much as possible. Here I am using the blunt applicator needle to point out a small air pocket still trapped in the servo.



The servo was then placed submerged in a jar of mineral oil and placed inside the vacuum chamber. Here’s where things I think became interesting.



This photo was taken after about 5 minutes into initial drawing down the vacuum chamber. I thought this would be a few minute job in the chamber….

Here is a short YouTube video taken at the same time as this photo.

https://youtu.be/tGHYtYep1s0

28” of Mercury was reached immediately and held there during the degassing of the servo. Now here is the interesting part. The servo continued to release lots and lots of tiny to larger air bubbles for the next almost 45 minutes! I had to stop and reposition the servo a few times until the bubbles being pulled out of it became just about zero. Key word just about zero. The bubbles were micro at this point and very few.




After the visit to the vacuum chamber, the servo was removed from the jar of oil and kept in this position with the fill holes pointing up. I had left the o-ring and servo horn off of the splined during the degassing but quickly installed them after the servo was pulled from the oil and placed like this. Next I carefully took a a paper towel soaked with isopropyl alcohol and cleaned off just the area around the fill holes. It is also interesting that the equalizer diaphragm is still in a puckered position. I’m assuming it stretched this way and took a set like this.



Next I used some baking soda and CA glue to seal up the fill holes.




Once the CA cured the whole servo and wires where submerged in a jar of isopropyl alcohol and wiped off.



After all that, there are still two very small air bubbles trapped inside. It’s not the 100% fill that I was shooting for but it is darn close! Btw, the motor puked a ton of air bubbles during the vacuum session. That was one of the main areas of monitoring that was done during the entire process.

Okay one or two more interesting things witnessed today…

Although the equalizer diaphragm is puckered inwards, this is not a bad thing! The next step was to hook the servo up the servo tester to see if this thing still was alive. Yes it was! The travels where full in either direction but the response speed seems slightly slower to me.

After moving the servo back and forth many times with the tester, I noticed the servo heat up.



This is where the puckered diaphragm came in handy I think. As heat built up the expansion of the oil inside had somewhere to go besides being pushes out of the seals. This slight bulge in the diaphragm was only after few dozen full travels with the tester. The returned to its puckered state less than a minute after I stopped operating that servo.

Anyways, interesting stuff I think.

Nick

[He Who Shall Not Be Named]

Well done, sir!

David

[Monahan Steam Models]

Well done, sir!

David

Thank you sir! That diaphragm you suggested trying, came in handy for the heated oil expansion! Didn’t see that one coming but, duh!

[rwtdiver]

Nick,

I received my Arkmodel 1:48 scale Vll today. I have a question for you about the hull sections! Did you use the provided screws and the Plastruct Bondene solvent cement to glue the hull half sections, or just the solvent cement?



Rob
"Firemen can stand the heat"

[Bob Gato]

Great post! I love information like this- nice job..