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MiniHawk VTOL

A fully 3D-Printable VTOL aircraft, designed as a hybrid fixed-wing plank + tricopter planform. For FPV and UAV experimentation.

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The MiniHawk is a 3D-Printed VTOL aircraft. It was designed with printability in mind, and is intended to provide the community with a common and accessible VTOL testbed for experimentation and tinkering.

The vehicle uses three (3) brushless DC motors for propulsion, with the forward pair tilting for forward flight and yaw control, and the rear motor fixed for hover only. Four (4) servos are used to tilt the forward motors and to control the elevon control surfaces of the wing. The airframe is a "plank"-style wing with a center body containing avionics and battery, and internal conduits routing to the nacelles and servos. Twin vertical stabilizer fins provide mild directional stability.

GitHub Project Link:
https://github.com/StephenCarlson/MiniHawk-VTOL

The main documentation for the project is contained in the README Markdown file at the GitHub repo, here is a direct link: GitHub README.md .

A version of the README is mirrored in the project files on this project page, direct link: Local Copy

Sections of the README are repeated below otherwise.


Remarks

  • As this is a totally 3D-printed airframe, the fully-finished vehicle is moderately heavy, which is a handicap, especially in the hovering mode of flight. As such, be gentle and cautious in adding any additional weight. For the recommended print settings with a 0.4mm nozzle, the airframe alone weights a bit over 300g, and the all-up-weight of the finished vehicle is between 700g and 800g.
  • The parts used in this project are commonly available in the drone racing and R/C plane market(s). The only known limiting component is the DYS BE1806 motor, which is an older (~2015 era) motor with a diameter of 23mm and around 80W power. A standard 22xx- or 23xx-sized motor can be used on the tail, but the nacelle design was modeled specifically for the DYS BE1806-2300KV. A future revision may increase the nacelle size to be able to mount 22xx-sized motors. Another potentially limiting component is the GreatPlanes GPMQ3843 Threaded Ball-Link set.
  • The aerodynamics and stability of the vehicle are still under analysis and subject to revision. The CFD poses/cases used for aerodynamics analysis are included for independent study.
  • Most project files are prefixed with "MH5", as this is the 5th internal revision of the design of the MiniHawk VTOL. The "MH#" prefix is incidental and not to be confused with the MH airfoil series, of which the MH45 is used for this vehicle. Generally, "MiniHawk VTOL" is the correct name for this design and any revisions to be released. 
  • This vehicle was designed in Autodesk Inventor Professional 2019. While compiled STLs are provided, the Solid Model and Assembly files for this vehicle are withheld at the time of this writing; contact me for inquires on obtaining a copy or further development. 
  • The Rear Strakes are recent additions to the design to compensate for poor directional stability. The aircraft does not weathervane into the relative wind well without them, and may yet require even larger vertical stabilization surfaces, not unlike the early days of the F-117 stealth aircraft. Another late addition to the design is the Lid FPV Variant, which supports the Foxeer -Nano camera formfactor (15mm width) and has a 30.5mm grid for a video transmitter, such as the AKK Infinite DVR.

Metrics

Description Value
Wing Span 800mm
Wing Area 15.6dm^2
Aspect Ratio 4.1
Airfoil (Root and Tip) MH45
Length 396mm
Rotor Spacing 315mm Circle
Lipoly Battery 3s to 4s, 1300mAh
Motors (front) DYS BE1806 2300kV or eqv.
Motor (rear) 22xx or 23xx ~2000kV
Servos HS-65HB/MG or eqv.
Flight Controller (size) 30.50mm to 16.0mm Grid
Propellers (front) 5050 to ~5249
Propeller (rear) 6030 to ~5249

Flight Testing

The vehicle is designed to hover with a nose-high attitude (positive Angle-of-Attack). The reason for this is so that as the nose is dropped to level, the thrust vector brings the vehicle to an initial forward drift. Having established a forward trajectory, the motors are tilted to the 50/50 intermediate point and the vehicle is allowed to accelerate. The motors are then dropped to full forward-flight position.

MiniHawk-VTOL-1.0.0.zip

Copy of the v1.0.0 release, minus the CFD Analysis set to save space.

x-zip-compressed - 21.62 MB - 10/16/2020 at 19:33

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Portable Network Graphics (PNG) - 362.99 kB - 10/08/2020 at 21:46

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README.md

8 October version, hash: 4f8bb3d583c8381204c57d6dcc3cf7a78883c4c1

markdown - 45.14 kB - 10/08/2020 at 21:46

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View all 26 components

View all 2 project logs

  • 1
    Airframe - Step 1

    Clean all 3D-Printed parts, remove all brim/support material. For each wing, carefully carve away any stringing or over-extrusion in the hinge reinforcement wells such that the hinge pin will fit.

    Figure 1
    Hinge Pin Clearance

    Carefully cut the elevons free if needed (WARNING! Only cut slots on either end to allow for surface deflection, DO NOT cut the entire elevon out), and gently exercise each surface up and down until the living hinge is established.

    Figure 2
    Elevon Movement Cuts

    Bond the Canopy/Hatch-Lid pieces together using Thin/Medium Cyanoacrylate or Epoxy, and set aside to cure.

    Figure 3
    Hatch/Lid Bonding
  • 2
    Airframe - Step 2

    Bond the Empennage Halves together. Thin or Medium Cyanoacrylate, or Epoxy, are acceptable. Set aside to cure.

    Figure 4
    Empennage Halves Bonding
  • 3
    Airframe - Step 3

    Bond the Control Horn pieces (2) into each Elevon (Left Wing and Right Wing). Thin or Medium Cyanoacrylate, or Epoxy, are acceptable. The Control Horn should be fairly flush on the Elevon Top Surface, approximately 0.5mm extending above the surface. Fit should be tight; carefully carve away any burrs or over-extrusion from the slot in the elevon if needed.

    Figure 5
    Elevon Control Horn Install

View all 33 instructions

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Discussions

dekutree64 wrote 11/05/2020 at 05:11 point

Looks great, very simple and clean design. The front motor arms look pretty delicate though, especially without prop savers on the motors. Do they break off every time you crash?

  Are you sure? yes | no

Steve Carlson wrote 11/05/2020 at 06:06 point

For the accumulated set of crashes that have, all together, broken most parts of the airframe, the motor-tilt servo arms (and servo gears) have been perfectly fine. I've stripped an elevon servo (non-metal gears), but metal gears and nylon arms on the motor-tilt have been either lucky or robust. I'd be happy to find a servo-saver that is sized to this scale, if you have any recommendations.

  Are you sure? yes | no

dekutree64 wrote 11/05/2020 at 13:38 point

Hmm, maybe wrong terminology. By arms, I was referring to the orange 3D printed parts that are glued to the wings and reach forward to hold the tilting motor mounts. Looks like they'd snap off at the glue joint. Enlarging the glue area might sacrifice some airflow efficiency, but I think it would be worth it. The rear propeller sticking up probably limits forward speed quite a bit anyway.

As for servos, I think it would be best to simply use metal gears on the elevons as well. Although I am surprised you managed to break one in the first place. Seems like the wingtips would take all the beating and protect them.

  Are you sure? yes | no

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