Micro Twin FPV [Competition Entrant]

My Scratchbuilding Contest Entrant

For a while I had been looking for a small, powerful RC plane that can fly a micro FPV system without prop obstruction. The "weird plane" scratchbuilding contest set up by Experimental Airlines gave me an excuse to build something along these lines. Running on two 300 class Blue Wonders, the "Red Leader," appropriately named after a Star Wars fighter, is an ideal aerobatic parkflier with FPV and small camera carrying capabilities. Personally, I enjoy this plane because when I have limited space to fly in, or I need to travel, it will nicely fit or fly in small spaces. If you're looking for a plane that fits these qualities, then I hope I've just made your day :). Think of this plane as a budget, slightly more experimental, easier to build FT Mini Guinea pig.

DISCLAIMER: This plane is not Mach 10 weird. Judge it as you wish, but my ulterior motive in building this was as a fun, small FPV platform. Also, I did not choose the acronym 'WTF' for the plane, that is just the name of the contest set up by Experimental Airlines (who is really cool and you should check out) Thanks!

To get a better idea of what you're looking at, here's the maiden and a short overview of the ARC WTF Plane/"Red Leader"

 My original idea for this plane was to have three motors, two on the wings, and one pushing behind the fuselage. Unfortunately, as I calculated, the power to weight ratio would be too small and the wiring would have been weird and all over the plance, so I used two motors instead. That is why the tail booms are in the "V" shape, to allocate space for an extra prop. This original design would have looked something similar to the Cessna Skymaster with motors on the wings.

If you want to build one of these, I would not suggest using the "V" tail shape unless you really want that look. A single, thicker boom would be a better choice for maximum durability, maybe out of a carbon fiber rod or folded fuselage.

One of the experimental features I'm testing is a small-chord, higher lift wing with added extensions, similar to the Flite test wing, but adding on to the simpler armin wing using hot glue and tape. Fortunately, this works out quite well, as the extensions add an extra 10 inces to the original 30 inch wing without adding the weight of an entire airfoil.

Here is a side view of the wing. I have three pieces of foamboard inserted instead of the usual two. The wing chord is small for this amount of airfoil curve, so when the throttle is increased, the plane doesn't speed up, it just adds more power and torque.

Here is an overhead shot. You can see the added extensions and the tape and glue used to keep them on.

I've cut into the airfoil to make the ailerons instead of adding extensions because I wanted to keep the current wing chord. This is not required, and I'm confident that the plane will fly the same with added aileron extensions instead.

The fuselage can also be separated from the wing for storage and better accessability. Here is a photo of the dissassembled plane:

I was also originally going to make the tail booms detachable, but I later decided against it, as they kept falling off. The tail booms also have 12 inch skewers glued on to the sides for maximum durability.

Electronics Setup:

I am running two 300 class 1900kv Blue Wonders for power on 12 amp ESCs. All servos are 5g ultra-micro, and everything is powered by an 1800 mah 3 cell battery. Because this is a twin motor set up, you're going to need an ESC power splitter and a Y-harness for the receiver adapter lead. You need to cut ONE of the red (middle) wires (or whichever wire powers the receiver) from ONE of the ESC's leads so that the reciever does not get overwhelmed from BEC power from both ESCs. Here is a picture of the setup:

Overhead of elevator:

As you may notice, there are is no rudder. The plane tracks well enough that it does not need one, and the split vertical stabilizer makes it hard to put a control surface there. Also, setting up differential thrust with the twin motors can substitute quite well for an actual moving rudder.

The motors are mounted on small plywood mounts backed by triangle pieces of foamboard cut at 90 degree angles, nothing too elaborate, and no extra plywood support is needed.

Here is a complete list of electronics with links to where I bought them:

2 x 1900kv Blue Wonders - http://www.headsuphobby.com/HURC-300-Blue-Wonder-1900kv-Brushless-Motor-B-702.htm

1 x 6030 3 bladed prop standard - http://www.headsuphobby.com/GWS-6030x3-Standard-Rotation-Propeller-ONE-BLACK-Prop-B-215.htm

1 x 6030 3 bladed prop reverse rotation - http://www.headsuphobby.com/GWS-6030Rx3-Reverse-Rotation-Propeller-ONE-BLACK-Prop-B-235.htm

2 x 12 amp ESCs - http://www.headsuphobby.com/Sky-Power-12A-ESC-with-Switchmode-BEC-E-159.htm

3 x 5g ultra-micro servos - http://www.headsuphobby.com/Towerpro-5g-SG50-Ultra-Micro-Servo-K-420.htm?categoryId=-1

2 x Servo Y-harness - http://www.headsuphobby.com/Servo-Y-Harness-6-lightweight-32-gauge-wire-C-448.htm?categoryId=-1

1 x 2 ESC to 1 Battery connector - http://www.headsuphobby.com/Parallel-T-Plug-Adapter-Two-Motor-Harness-A-235.htm

1 x 1800-2200 mah 3 cell battery of choice - http://www.headsuphobby.com/111v-1800mah-30C-DBY-Power-Lipo-Battery-with-T-Plug-A-215.htm

1 x Reciever of choice

If you want to build one and want to order the parts directly from the site, the ESCs have jst connectors while the splitter has T-plugs. Instead of soldering, I just bought 2 jst to T-plug extensions. - http://www.headsuphobby.com/JST-Male-to-T-Plug-Male-Adapter-C-705.htm?categoryId=-1

FPV

Here are some ways FPV gear and cameras can be mounted on the plane:

Ultra Micro Camera in fuselage

Larger, Mobius-type camera on top or in fuselage

200mw transmitter mounted on top of battery (with camera in front)

General Specs:

Wingspan: 40 in
Wing length: 6 in
Aileron length: 14 in
Aileron width: 1.5 in
Total length airplane: 23.5 in
Length fuselage: 12 in
Diameter fuselage: 2 in

In case I missed anything, here are all the videos I've put together featuring this plane, and if you have any questions about building the plane or its design, feel free to comment below.

More Specifications and Details:

Flight Tests:

Links:

Sub to my youtube channel: https://www.youtube.com/channel/UCot5Q3Aw3oIE7uqcVSLnyFA

My website: http://AileronRC.wordpress.com

Thanks!