Version 2.0 - Hotfix and 2.1 Preview

This is long overdue: The last remnants of the old nacelle and motor tilt mount design must be swept away! It was buggy and is going to cause people issues when they try building the old October 2021 design release. Previous to this, I've been advocating for people to pull from the GitHub folders, but that was irresponsible, as the only proper action is to release a Hotfix. Being a bit of a perfectionist, I had been putting that off. Anyhow, at this snapshot of the master branch, I'm still in the middle of preparing the Version 2.1. release, so this tag/release is going to contain major spoilers!

Again, please use this release, or download files from the GitHub folders, don't use anything from last year!

Version 2 - Minor Fixes

This is a snapshot of some minor fixes, mainly to documentation. The NACA-Vented Hatch/Lid is present, and the tail has a -Full variant for those wanting to print it as a single piece. Slight change in the accompanying file names. Last time, the reduced zip archive was named MH7_EssentialFiles.zip, but I think going forward, it will just be named MiniHawk-VTOL-2.x.x.zip as that matches what I'll be published on the Hackaday.io Project Page. So, the tar.gz and .zip generated by GitHub will represent the entire file set, much of which is not interesting to the main builder; the zip archive I'm manually adding is the one you will want to download if you just want the essentials.

Version 2

Release Description

This is the "Version 2" design of the MiniHawk-VTOL, prefixed as "MH7_" in the file collection.

• The Wing design is the same as v1.0.0, that is, no changes to airfoil selections or geometry.
• Provisions for a spar (carbon fiber or equivalent) are made, for up to 640mm length. From Issue #1
• Servo wire routing is now on the bottom surface of the wing, per Issue #3 .
• The nose has been extended, and the battery and flight controller have swapped places. Per Issue #8 .
• The new nose also enjoys a larger hatch/lid definition. All mounting stanchion fastener positions are accessible. Issue #15 .
• NACA cooling ducts are available for the nose, Issue #27 .
• The Vertical Stabilizers are redesigned and have enough volume for proper directional stability, per Issue #5 .
• Motors of up to 29mm bell diameter are supported for the forward nacelles, from Issue #2 .
• The tail motor support has LED pockets (Issue #4), and allows up to a 6-inch prop (Issue #14 ).
• The winglet can support a GPS and other devices. Issues #6 , #21 .
• Typical pitot-tubes can be mounted in the wing leading-edge, Issue #20 .
• Center-of-Mass bumps are not yet added to the wing, but a digital-tabletop-scale balancing method is available per Issue #12 .

Known Issues

1. Per Issue #26, the tilt servos need at least 2.0 kg*cm of torque, but even then, transitioning to forward-flight is temperamental. The Nacelles need to be redesigned with a balanced tilt method, and until then, be gentle with forward-flight transitions by reducing the total thrust produced during the action.
2. The Hinge pins on the nacelles can "creep" out of the shaft due to vibration, and thus these should be glued or otherwise knurled to provide retention.
3. Tilt servo endpoints that allow the prop disc to get too close to the top of the nacelle arm will result in the prop grazing/brushing the top of the nacelle arm during dynamic and high-gee maneuvering. Set the tilt servo endpoints generously far to prevent the prop disc from doing this.
4. Symmetrically, tilt servo endpoints should be very carefully tuned so that the servo is not stressed when the motors are pulled to the forward-flight position.
5. A 6-inch prop mounted to the rear motor can potentially contact the vertical stabilizers, especially during dynamic movement or hard landings. When installing the vertical stabilizers, provide a few extra millimeters outboard to prevent prop-strike, or trim the 6-inch prop slightly.
6. There have been some requests for an FPV lid design that can accommodate larger cameras. A STEP model is provided of the vanilla Lid/Hatch for members of the community to develop this, but otherwise this will be addressed in future releases.
7. Servos are currently mounted using double-sided tape and/or Hot-melt adhesive. Servicing servo arms is difficult at the moment, requiring the respective servo to be removed to access the arm screw fastener for arm replacement. From Issue #13 .
8. The Flight Controller mounting tray has two variants, a typical "plate", and a compliant-mechanism-inspired version. Please be aware of how vibrations are conducted to the flight controller and add your own vibration-dampening solution as required. The compliant-mechanism-inspired version will behave as an undampened harmonic oscillator, and will manifest harmonic resonance, without viscoelastic material injected between the folds of the supports.

Supplemental

Much has happened in the past year since the initial release. In October and November of 2020, the MiniHawk-VTOL had barely flown in forward-flight a handful of times, and issues with pitch and directional stability were still unsolved. Through the course of early 2021, the design was iterated, polished, flight tested, crashed many times, and finally converged at a usable form in April, and was immediately used to prove its viability as a reconfigurable swarm platform. Alas, the secret is finally out; my occasional edits to the Hackaday project page got noticed by the writing staff, and the project has gone public, if not viral. Responding to this newfound popularity, I accelerated the release of Version 2.

Building this aircraft should be possible for any individual who is proficient in constructing typical R/C aircraft or multicopters. The build instructions are in need of some updating at the time of this writing, but are close enough. Supplemental to the instructions included in this repo are the timelapse videos in this list.

Flying this aircraft requires the Center-of-Mass to be located between 26mm and 30mm from the wing leading edge. The balancing procedure is detailed in Issue #12 . In forward-flight, without any stabilization active, the roll rate can be in excess of 540 degrees-per-second. Hard pitch-up maneuvers result in a sharp stall with some potential for tip-stall, but under moderate wing-loading, the aircraft behaves well. As a tricopter, the vehicle has good maneuverability, especially in yaw, but having a quartering or pure tailwind will yield strained behavior by the control system, so weathervaning is appropriate and necessary.

Initial Release

The project is feature-complete, and while some polishing tasks remain, the time has come for release. Version rules going forward as follows:

• This is Aircraft Version 1 (despite internal/private version=5 as hinted in Readme); Version 2 will occur should any substantial change be made to the planform/Outer-Mold-Line or build method. For example, making a larger version using EPP injection molding, etc.
• Revision 0. The Outer-Mold-Line and dimensions should be mildly consistent for all revisions of a version, but internal structuring and some external surfaces may change. Next release will be Revision 1, which will likely feature a carbon fiber spar, changes to wire routing, larger motors, larger vertical fins, and other wish-list items I've accrued.
• Patch 0. Any important changes to build instructions or supplemental artwork will increment this number. Geometry changes should not increment this field.