TVBS Nano Drak VTOL conversion

There's now a Facebook group to discuss builds, successes and problems. Come join at https://www.facebook.com/groups/vtolhangout

Aug 6 2022 update:

• Updated the param file with my latest tune. Note you need to check that plane is level in quad mode by connecting to mission planner and checking. Adjust AHRS_TRIM_Z to get roll perfectly level
• added a h743 FC mount (remixed from here: https://www.thingiverse.com/thing:5022908) to keep the FC perfectly mounted in all axes.
• added a fin guard to go behind standard (non-boomer) fins to protect them during tail landings.
• added a 45 degree gps wedge to mount GPS at 45 degrees so it can get satellites in both horizontal and vertical modes. Works well with the side hatch covers I used found here: https://www.thingiverse.com/thing:3929719

In the spirit of continuing to try different things, I've modified the original Nano Drak VTOL nacelles to work as a TVBS, Thrust-Vectored Belly Sitter. The design has been proven to work and just needs more tuning to perfect the transitions. This is a more efficient VTOL platform since it only uses 2 motors. Its lighter but CG is a bit more tricky because there's no motor in the rear to offset the weight of the two forward motors. Battery probably needs to be placed at the rear of the battery bay.

There are 2 versions of the nacelles. One has a slot for a servo in the nacelle. That makes the build much easier as you don't have to cut in holes in the wings for the servos. But it also puts more weight forward of CG. Depending on how much weight you have in the nose of your nano drak, you may be able to get away with these nacelles. Alternatively, you can use the more compact nacelle design and put the servos in the wing. I mounted my servos in the wing as far back as possible as I have a heavy printed mount with DJI in the nose of my nano drak.

I also added a bumper for the boom tail if you choose to use a boomer which would help a bit with CG. Its important to protect the elevator in a tailsitter setup. This is just a quick design I did and haven't really tested. Printing it vertical with supports is probably best (as its laid out) to avoid having to pick out supports from the inside. You may have to slightly trim the elevator on the sides so it clears the bumper.

Included is the Ardupilot param file I used on the transition maiden.

Here's the hover maiden video: https://www.youtube.com/watch?v=d1PKQAvDJWE

Here's the first transition test: https://www.youtube.com/watch?v=BL99-sontV4

(still some problems here with the tune.. transition from forward flight to hover needs some more work). Actually this is probably Vortex Ring State, descending too fast under power. Lower pitch prop could help. Going to try 6x4 bi-blade rather than 5x4x3. Also best to descend using q-hover or q_loiter and set descent rate lower using Q_VELZ_MAX_DN to a speed that doesn’t cause issues during descent (I’m trying 100 cm/s but still finding the best setting). Too fast and all tailsitters have problems it seems.

The original VTOL build walkthrough video not including conversion to TVBS: https://youtu.be/8DG942hFIpE

And a basic Ardupilot setup video (no TVBS info here): https://youtu.be/4e3JP7eEZIU

Pease follow the Ardupilot docs here for the initial conversion to TVBS: https://ardupilot.org/plane/docs/guide-tailsitter.html

Also there's a tuning guide for tail-sitters here: https://ardupilot.org/plane/docs/tailsitter-tuning-guide.html?fbclid=IwAR1naw-sI2J3Xbo57-BIJy65Tul89Atc-INZ8SSWEIZe_M5N2aE-9-wmfeI

Credit for the original tilt-rotor design goes to Steve Carlson who designed a fantastic fully 3d-printed plane. Check it out here: https://hackaday.io/project/175286-minihawk-vtol

I printed using Pet-G for its strength. 20% infill (50% for the tail). The nacelles and tilt motor mounts are laid out on their sides. I've had good success printing them in that orientation with full supports. Requires some cleanup with needle nose pliers afterward but supports come out pretty well. Mirror for the other side.

Parts needed:

Nano Drak.. I tried without boom kit at first and it works but I think it works better with a boom kit for CG. I also went with the 40" wings cut down to 32" wings.

2 motors. I’m using iflight 2208-1800 motors https://www.amazon.com/gp/product/B07XYYRWGP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

with 5x4x3 props but apc 6x4 props might help with Vortex Ring State so trying that asap

and running 6s 2200 LIPO

4 in 1 ESC or individual ESCs : https://www.amazon.com/gp/product/B0946J3XZ6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Longer motor wire: https://www.amazon.com/dp/B01K4QVW1K?ref=ppx_pop_mob_ap_share

Mr30 connectors for the motor wires: https://www.amazon.com/dp/B07VMK96QH?ref=ppx_pop_mob_ap_share

Ardupilot compatible flight controller. I’m using a matek h743 wing v2

GPS with compass.. i'm using this one https://www.amazon.com/gp/product/B092RVFSN4/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

.047" smooth rod for hinge mechanism, (may have to drill out hole with 1/16” drill bit) and 2-56 rod for linkage to servos.. also will need clevis of your choice to connect to servo horn (I used a solder clevis)

e-z connector like https://www.dubro.com/collections/e-z-connectors/products/e-z-connector

to lock hinge rod in place (bend other side)

2-56 ball link https://www.dubro.com/collections/kwik-links-clevis/products/2-56-threaded-ball-link (will have to drill out hole with 5/64” drill bit)

servos for tilt mechanism..I am using Turnigy DMC809 which have tons of torque and smooth operation: https://hobbyking.com/en_us/dmc809-micro-digital-coreless-servo-25t-3-8kg.html. But if they are out of stock you can also find the pricier kpower brand which is the same servo on Amazon KPOWER 3kg/0.07s Coreless Titanium Gear Full Metal Case Slim Servo for RC Airplane Heli https://a.co/d/50YJh2K

Another good option: https://www.buddyrc.com/products/kst-ds215mg-digital-servo-6-0v-0-06s-3-10kg?variant=39868029042876

My nano drak nose and pan option: https://www.thingiverse.com/thing:5351076

Winglets: https://www.thingiverse.com/thing:3076740 scaled 130% long by 120% tall to fit 32” wing mod. For others wings would have to try different scaling factors.

Receiver and fpv system