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Project Notes

#679 Yawatamaru / Un’yō Conversion

Using a Pepper’s Ghost effect in a box diorama to capture the Yawatamaru (八幡丸) conversion to Taiyō-class escort carrier Un’yō (雲鷹).


Here’s a quick demo..


And here’s a behind-the-scenes view of the box diorama in action:



Yawatamaru (八幡丸) is one of three Nitta Maru-class cargo liners built in Japan during the late 1930s to be transferred to the Imperial Japanese Navy (IJN) for conversion to escort carrier. The Yawatamaru was converted in 1942 to Taiyō-class escort carrier Un’yō (雲鷹, Cloud Hawk). This is described in The Imperial Japanese Navy in the Pacific War by Mark Stille.

When I discovered that Aoshima had 1:700 water line kits of both the Yawatamaru and Un’yō (both new tools from 1982), the lure was irresistible.

The interesting question was how to display the ships to best effect to describe the conversion. I wondered whether a box diorama with a Pepper’s ghost illusion would work.

Well, I finished making the kits back in 2021, crated the basic box diorama and electronics in 2022 but it then sat on the shelf waiting for me to come and tweak the effect. Which I finally did today (2023-01-02) - just before I need to go back to work;-)

The Yawatamaru

The Aoshima kit No. 045718 of the liner Yawatamaru (日本客船 八幡丸) is available in recent boxing but is a 1982 tool. It is however reasonably well detailed and goes together just fine.


Feature Gunze MrHobby Paint Used
Flat White: upper hull, superstructure H11 Vallejo 70.951 White
Flat Black: funnel, hull H12 Vallejo 70.950 Black
Tan: hatches H27 Vallejo 70.941 Burnt Umber
Wood Brown: deck, masts, spars H37 Vallejo 70.981 Orange Brown
Sail Color H85 Vallejo 70.951 White

Before I knew it I’d decided to do a pretty much full build before painting




Still got some tidying up to do - windows, weathering, rigging



The Aoshima kit No. 045220 of the escort carrier Un’yō (日本海軍 航空母艦 雲鷹 ) is available in recent boxing but is also a 1982 tool. Like the Yawatamaru it is reasonably well detailed and goes together just fine.


Feature Gunze MrHobby Paint Used
Flat White: boat covers H11 Vallejo 70.951 White
Flat Black: funnel; plane engines H12 Vallejo 70.950 Black
Cocoa Brown: lower hull H17 Vallejo 70.985 Hull Red
Wood Brown: boat decks H37 Vallejo 70.941 Burnt Umber
IJN Green: plane upper surfaces H59 Vallejo 70.897 Bronze Green
IJN Gray: plane lower surfaces H61 Vallejo 70.989 Sky Grey
IJN Gray: flight deck H61 Vallejo 70.990 Light Grey
Dark Gray: upper hull H83 Vallejo 70.992 Neutral Grey + 30% 70.994 Dark Grey

Starting the Un’yō..

build_02a build_02b build_02c

So.. the thing about building carriers!!


Pile-up on the flight deck


Finishing the Ship Construction

build_03a build_03b build_03c build_03d

Finished the main build of the Aoshima 1:700 kits (rigging and weathering to come).




finishing details for the Un’yō - a little rigging, rust effects and modulation



the Yawatamaru gets some rigging


Pepper’s Ghost Lighting Effects

The lighting effect is achieved with 4x 12V cool white LED strips, individually controlled by an ATtiny85 microprocessor

The Arduino sketch YawataMaruUnyo.ino is programmed to the ATTiny85 with fuses set for 8MHz internal clock. I used ArduinoISP to program the chip via an Arduino Uno.

LED strips are connected and used as follows:

Pin Name Arduino Port Pin Effect
LEFT_FOREGROUND_LED PB1 6 (Yawatamaru) PWM fades
LEFT_BACKGROUND_LED PB0 5 (Yawatamaru) PWM fades
RIGHT_FOREGROUND_LED PB3 2 (Un’yō) hard on
RIGHT_BACKGROUND_LED PB4 3 (Un’yō) lightning flashes

The circuit diagram is as follows. A 12V DC power supply drives the LEDs, with a buck converter module stepping the voltage down to 5V to power the ATtiny85.



The sketch was initially tested on a breadboard:

Breadboard Build

I transferred the design to a small piece of protoboard. Layout sketch:


Final Construction

Internal layout showing the one-way mirror on 45˚ angle in front of the Yawatamaru is a piece of acrylic with silver insulation window film applied to the rear.


The finished box


Power jack and switch on the rear..


Looking through the window when the Yawatamaru is illuminated:


Looking through the window when the Un’yō is illuminated:


Here’s a demo of the final effect:


And here’s a behind-the-scenes view of the box diorama in action:


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.