Printing the Maripi

This RC Acro Airplane was my second printed RC airplane. The Maripi is also an RC airplane designed by Kraga. More information about my printers and software you will find in my other post on the Kraga Kodo. To experiment when further with the 3D printed airplanes, I choose to make the second plane in another material HIPS - High Impact Polystyrene. The combination of carbon struts, covering film, lightweight design, and the fuselage with carbon reinforcement has proven to be successful.  I choose the white and black Makerfill HIPS filament and Oracover Red Transparant Fluorescent film. High impact polystyrene (HIPS) is a material blend of polystyrene plastic and polybutadiene rubber. The mixture of these polymers results in a material that’s both tough and flexible. HIPS is very similar to ABS, but as the name implies, it’s capable of withstanding much higher impact forces. It’s easily painted, machinable, and works with a large number of adhesives. I designed some extra parts in FreeCAD 0.18  as battery support, a receiver-, and gyro support, wing base and wing ends. Some of my Printer settings are; minimum volume 200x200x180 mm, Extruder 0.4 mm, Layer Height 0.19 mm, Extruder Temp 245 ºC, Filament Speed max 40 mm/s, Bed 90 ºC, Cooling 0%.

Electronics for this Maripi

I used an Extron motor 2814/20 KV800 Outrunner with an Extron iQ-40 ESC, 4 Savox SH-0257 MG (Metal gear) servos, a Spektrum AR6610T 6 channel receiver,  and a Yuki Brainergy 3S 2800 mAh battery.

Modifications

MOD1: Modified the main wing connection with printed and glued HIPS base plate on the main wings and two super magnets and modified extra flexible safety connection.
MOD2: Modified tail section with extra HIPs elevator and rudder parts to close the surface ends
MOD3: Printed a semi-transparent cockpit in PET-G for the looks and to test this material.
MOD4: Added A3Pro Gyro from Hobbyeagle to improve stability and to test the auto hoover mode.

Summery

A successful maiden flight, but only with the help of the A3pro gyro's, because de Centre of Gravity was not forward enough. I had to add extra weight left and right of the motor and glued in with a hot glue gun. After more flights seem this plane performs well, but the HIPS material seems to crack easily when you hold the wing firm, probably because of the different material properties between HIPS and original by Kraga proposed PLA. Not done too much Acro till now. No crashes so, fortunately, I can not evaluate the HIPS resistance to impact forces.

Aircraft Characteristics after Configuration and Modification

Wing Span: 1.1 m
Length: 1.0  m
Flight Weight: 1.2 kg
Wing Aera: 20 dm2
Wing Loading: 60 gr/dm2
Wing Cube Loading: WCL 13.4
Power: 3S 2800 mAh
Motor:  Extron 2814/20 KV800 Outrunner
Propeller: APC 1x  11x5.5 2-blade
Stall Speed: 32 km/u
Sound Pressure: 50 dB(A)/7m

video

Photos