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Old 10-18-22, 04:04 PM   #1
Gwenydd
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Default Gwen's Arkmodel 1/48 scale RC Type VIIC build log

This is the beginning of my thread for the build of my radio controlled Arkmodel 1/48 scale Type VIIC U-boat. I Purchased the kit for the sub on Amazon from Arkmodel (in China) for around $380. I had a Watertight Cylinder sub driver system custom built for me by Nautilus Drydocks (You know... "Bob Martin, the RC Sub Guy" on YouTube). The WTC system has a brushless drive motor with a gearbox to drive two counter-rotating propellers, servos for the forward and aft dive planes, rudder, and one extra output which I will probably use to open and close the bow cap doors for the torpedoes. I also have an automatic pitch control board which directly controls the aft dive planes automatically to keep the sub level at all times unless it receives an override from the transmitter to move the aft planes. And last but not least - I have a small emergency ballast blow tank that can be pressurized with canned airbrush propellant to do an emergency blow of the ballast tank in case I can't get the sub to re-surface. The entire WTC system with motor, servos, and other subsystems cost me around $1100 total. Not cheap but I prefer to spend a little more to make sure I don't lose my investment due to not being able to re-surface the boat.

The boat is 1.4 meters in overall length (55") so I can barely stretch my arms far enough to touch the bow and stern at the same time. This is going to be a lot of fun! Unlike most sub model kits this one was specifically designed for RC use. It has all the flood vents pre-cut through the outer hull, and proper mount points for the control surfaces to function.

I just received my kit and WTC packages a few days ago and have started working on the build. I'll get some photos shot and post another update later today.





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Old 10-18-22, 05:36 PM   #2
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Default Getting started on the build

The kit is made of some type of ABS plastic so it is not nearly as brittle as styrene. I think it will make for a very tough RC model.

I decided to start with the conning tower build. I have it mostly together now with the exception of filling a few small gaps and adding some details that were not included in the kit. You can see I already added the small (silver for now) hand railings at the front sides of the wintergarten. All the brass parts you see in the photos are photoetched brass parts which are included in the kit.







Here you can see a test fit build of the stern control surfaces and related support structures.



You can see that there is very little room in the stern for the rudder control horns. It takes some fiddling and reshaping of parts to get moving parts to not interfere with each other.



Here's a bit of a size reference photo with the hull on top of my Virtual Pinball cabinet and with my U-boat kaleun's hat.

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Old 10-20-22, 02:17 AM   #3
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Default WTC (Watertight Cylinder) 101

So, for anyone who isn't already familiar with this stuff, this is what the insides of most static diving RC submarines look like. Static, as opposed to Dynamic diving, means that the dive system is capable of allowing the submarine to dive without needing to move forward or backward and pushing itself down using the dive planes. Static systems dive by changing the overall buoyancy of the boat, so static diving systems tend to be more complex than dynamic systems.



This is the WTC or Watertight Cylinder containing all the electronics, batteries, radio gear, motors, servos, etc. to operate the sub. Mine is a 3" diameter tube with an 8" long ballast tank. If you do the math it works out to 56.55 cubic inches of volume or 2.039 pounds of water at 70 degrees. At least until I become proficient at operating the sub safely I will keep it set up to only flood to neutral buoyancy, which means I can operate pretty much normally using the dive planes (along with forward motion) to dive and surface before blowing the tanks. Later I may set it to allow for some negative buoyancy to allow quicker dives and diving in place... we'll see how it goes.

This is the forward section of the WTC which contains forward dive plane and torpedo door servos as well as the radio receiver, battery, a battery and radio signal monitor board, and wireless on/off switch for the sub that uses a key fob to activate.



This is the center section which is the ballast tank. The brass cylinder in the middle is a canister that can be filled with compressed airbrush propellant to emergency blow the tank. The tank vent is a small brass tube on top with a valve which is activated with a servo motor to allow air out of the tank and for the tank to flood. The large opening on the bottom of the tank allows water to enter as well as providing maintenance access. You can see the wiring for main power, servo motor, and engine controls running through an airtight tube that runs all the way through the ballast tank at the top. The airtight tube also allows the pressure inside the forward and aft WTC compartments to equalize.



And this is the aft section of the WTC containing the main drive motor and ESC, aft dive plane servo, rudder servo, two air pumps for blowing the ballast tank, and an electronic auto-leveling board connected to the aft dive planes.



I have already done a bit of setup on the WTC, mostly involving running wires and connecting servos and the subsystem control boards.

And last is a view of tha aft end of the WTC showing the control pushrods and gearbox to drive the twin propellers. The brass filler valve on the hose to the right allows me to fill the emergency ballast blow tank with airbrush propellant. The other two hoses are for the ballast air intake and pressurization testing.



I have been building various types of RC vehicles for many years and this one is the most complex system-wise I have done so far. There's a lot of stuff to set up, program, tweak, and maintain. Much more than an RC airplane or tank.

More to come on this subject as the work progresses...
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Old 10-20-22, 11:44 PM   #4
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I decided today I just wasn't comfortable with the fragility of the railings on the Arkmodel Type VIIC so I am replacing all the plastic railings with soldered brass ones. Also the wintergarten railing wasn't quite shaped right so...here's my start on the wintergarten upper rail replacement. I'm waiting for more brass rod to arrive in the mail before I proceed any further because I'm all out...



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Old 10-22-22, 09:09 AM   #5
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Oh boy, I have been waiting for this

The Arkmodel is designed fopr RC use, then? On the stern planes and rudders, the small screws are part of the kit out of the boy? What material are the threads the screws screw into? Are they metal or plastic? Or metal axle shafts?
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Old 10-22-22, 06:34 PM   #6
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Quote:
Originally Posted by Onkel Neal View Post
Oh boy, I have been waiting for this

The Arkmodel is designed fopr RC use, then? On the stern planes and rudders, the small screws are part of the kit out of the boy? What material are the threads the screws screw into? Are they metal or plastic? Or metal axle shafts?
Yes, it was specifically designed for RC use. Yes, those small screws on the control surfaces are included in the kit. They screw directly into the end of the control surfaces which are made of ABS plastic, so you have to be very careful when installing or removing them not to strip them out. I am probably going to make a set of metal threaded inserts (or maybe just use nuts) and drill out the holes larger and glue them in place so I have a more durable connection. The shafts for the control surfaces are all steel rods and the mount points on the hull have brass bushings for them to fit through, so they all turn pretty smoothly and without wobble.
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