Roa II

Roa is an embodiment of my childhood dream. I always wanted to build huge, elegant, slow flying glider, to enjoy thermals in sunny afternoon. I also wanted to find out what are the current limits of 3D printing technology, and I definitely did that.

The size turned out to be huge challenge, and I spent many years working on this plane. The biggest problem was twisting of the wing, but thanks to one of you I managed to resolve that. Now it is finally ready to see nozzle of your 3D printers.

Although the wing has some flex, there is only a tiny bit of twist and Roa II can handle faster motor climbs with ease. On top of that it can definitely handle rough landings and even some crashes because the wing excellently absorbs impact energy.

When it comes to flying, its glide ratio is on another level compared to smaller gliders like Kodo II. Because of technical limitations, I was not able to make polyhedral wing to achieve super relaxing circling ability. But despite that, Roa II can catch and stay in thermals just fine.

Check out Roa II thread on RCGroups

  • wingspan: 340 cm
  • length: 135 cm
  • ready to fly weight: 1873 g
  • wing area: 0.68 m2
  • motor size: ⌀ up to 37 mm
  • required RC: 7 channel
  • printer build volume: 15 x 15 x 10 cm
  • printing material: irrelevant
  • weight of printed parts: 867 g
  • parts count: 139
  • printing time: 153 h
  • price: $42.90          Buy

What else do you need - your shopping list:

shopping list
part dimensions count
carbon tube ⌀ 2x1 mm   ↔ 1 m 10
carbon tube ⌀ 3x2 mm   ↔ 1 m 5
carbon tube ⌀ 4x3 mm   ↔ 1 m 4
carbon tube ⌀ 6x4 mm   ↔ 1 m 2
carbon tube ⌀ 8x6 mm   ↔ 1 m 3
carbon tube ⌀ 10x8 mm   ↔ 1 m 4
carbon tube ⌀ 14x12 mm   ↔ 800 mm 1
covering film ↔ 4 m 1
pinned hinge ↕ ↔ 16x28 mm or smaller 26
folding propeller ↔ 13x8 inch 1
spinner ⌀ 45 mm 1
screw M2 ↔ 8mm 22
other common accessories (clevises, servo extension cables, electronics ...)
To find out where to get carbon material check how to.


This is by no means the best way possible how to setup your plane.
This is just list of affordable parts that I believe could be good starting point for beginners.


Turnigy Aerodrive SK3 - 3536-1200kv Brushless Outrunner
I recommend to use motor weighting roughly 110 g, to have no problems setting the CG. You should be able to fit inside motors with diameter up to 37 mm.
Suitable propeller sizes: 13x8.


Turnigy Plush-32 60A (2~6S) Brushless Speed Controller
Or similar.


Turnigy nano-tech 1000mah 3S 25~50C Lipo Pack or Turnigy nano-tech 1600mah 3S 25~50C Lipo Pack
You can choose other battery but keep your size and weight similar to the examples above (up to 150 g). Using these, ESC and battery are installed as much as possible in the front of the fuselage next to each other (parallel config). For heavier batteries you need to put ESC into the front of the fuselage area and battery behind it closer to the servos (series config).


This depends on your transmitter. Only requirement is to have 7 channels.


Hitec HS 85-MG or similar.
More details about required servo dimensions can be found in build guide pdf.

KRAGA Roa II collage