Building a Powered Kite

Who knew the Powered Kite could be so much fun?!?  After being cooped up indoors all winter, we relish the idea of a ridiculously simple plane that flies like the foam board is ecstatic to be turned loose in the sky, not doomed to a third-grader's social studies project.  My new-pilot friend, Patrick, who test flew it said it was easier than the FT Flyer.  Not too surprising since it's essentially a derivative of the gentle Nutball.  That it's like flying an optical illusion is just a bonus.  (See the original LET'S GO FLY A (POWERED) KITE article.  Link, below.)

The Powered Kite is a 3-channel plane designed for light wing loading, gentle handling, and high-alpha flight.  Even in mild winds, it can throw out a kickstand and park in the sky like a kite.  But it can also handle gusty winds.  Relax the stick forward, and it can also cavort in the sky like a homesick angel, doing graceful loops and flying inverted.

Here's how to make one.  Tiled plans and precision drawings are overkill.  Most of the dimensions aren't critical, and when they are, I've provided a template.

In general, the Powered Kite appreciates the axiom, "Measure it with a micrometer.  Mark it with chalk.  Cut it with an axe."

I assume you've built an FT Flyer, FT Nutball, or similar foam board plane, and so you have all the construction skills to build this kite.  When I built a second kite to test these instructions, it took me about 4 hours from clean sheet of foam board and box of parts to flight-worthy kite.  That doesn't include artwork.

YOU'LL NEED...

• one foam board sheet, 30 inches by 20 inches
• a yard stick
• a foot-long ruler (optional)
• pen and pencil
• red pen (optional)
• two Ping-Pong balls
• crepe paper streamer (Walmart sells rolls in the party section for 97 cents)
• and the usual supplies for building foam board planes (razor knife, packing tape, strapping tape, hot-glue gun, gift card, landing gear wire, Velcro(r) sticky back tape, Velcro strap (1 inch wide), push-rod wire, BBQ skewers, control horns, firewall, coffee stirrers, linkage stoppers, etc.).

The power system comes from Flite Test's Power Pack B for fixed-wing, small planes.
Motor:  Emax 2822, 1200 kv
Prop:  8 x 4.5
ESC:  BL-Heli 20 amp, with XT60 connector
Servos:  Emax 8.5 gram

LAYOUT AND CUT YOUR PARTS (about 1 hour)

Lay your foam board sheet "portrait" style in front of you.

Starting from the lower right-hand corner, measure 26 inches (660 mm) up the right-hand edge and make a mark.  From that same bottom corner, measure 26 inches (660 mm) to the left-hand edge and make a mark.  From those two marks, measure 14-1/2 inches (368 mm) to the top edge and make a mark.  Connect those dots.  That's the outline of your kite.  It should be about 33 inches (838 mm) long by 22 inches (559 mm) wide.

From the nose corner to the tail corner, draw a faint pencil line down the center of the kite.  That is your center line to align your power pod and vertical stabilizer.

Draw the nose flat where your firewall will be.  Your ruler will show the correct placement and orientation when it measures 2 inches (51 mm) between the drawn edges and the penciled center line is 1 inch (25 mm) from both sides.  Draw that nose flat line.  From there, measure 7 inches (178 mm) aft and mark your CG.

Now, measure the "scribe" lines that will define the polyhedral and elevator joints.

Polyhedral Scribe Lines

Measure along the leading edge from the nose point 6-1/2 inches (165 mm).  Make a mark on the left and right wing leading edges.  Those are points (A) on the drawing. 

From the tail point, measure forward along the trailing edges 11-7/8 inches (301 mm).  Mark that spot on the left and right wings.  Those are points (B).  Now draw a line (red, optionally) from (A) to (B) on the right wing, and again on the left wing.  You'll cut halfway through the foam board along those lines.

Elevator Scribe Line and Vertical Stabilizer Slot

From the tail point, measure 7-1/2 inches (190 mm) along the left and right edges of the kite.  Mark those points, then draw a line (red, optionally) between them.  That's the elevator hinge line.  You'll cut halfway through the board along that line.

Draw the slot for the vertical stabilizer straddling the penciled-in center line.  The slot is only as wide as your foam board is thick.

Vertical Stabilizer and Rudder

In the bottom left-hand corner of the foam board, measure and pencil in a rectangle 6 inches (152 mm) wide by 10 inches (254 mm) high. 

Halfway up the rectangle and using your (red, optionally) pen, draw a horizontal line bisecting the rectangle into two smaller rectangles 5 inches (127 mm) high.  That line defines the rudder hinge.

Draw the diagonal lines in pen, defining the leading edge of the vertical stabilizer and the trailing edge of the rudder.  Measure 1-1/2 inch (38 mm) up from the hinge and mark the trailing edge of the tail-dragger skeg.  Then, 2-1/2 inches (63 mm) up from there, mark the leading edge of the skeg.  Now, draw your skeg in pen.  I made my skeg 2 inches (51 mm) deep, but you can make it any size you like.

Finish drawing your vertical stabilizer in pen.  Erase the pencil lines to avoid confusion during foam-cutting time.

Power Pod

The Power Pod dimensions are kinda critical, so print and cut out the template, here.  Short Power Pod Template

Lay it on the sheet and trace around it. 

Cut out the parts.  Cut the nose point off at the firewall line.  Scribe half-thickness along the red lines.  Don't worry about cutting the slots in the wing for the power pod, yet.

BUILD THE POWER POD (about 1 hour)

Nothing fancy.  It's just shorter than normal.  Mount your motor, and locate the ESC and receiver as far forward as practical, leaving the aft half of the power pod vacant for the battery to snug up in there.

I poke holes through the corners of the power pod and fish out my antenna leads so they're in the clear and at about 90 degree angles to one another.

MEASURE AND CUT THE POWER POD HOLES (about 5 minutes)

Lay the power pod on top of the wing with the firewall snug against the nose flat.  Center it over the penciled center line.  Using the power pod tabs as a template, mark and cut the 1-inch (25 mm) slots to match.  A length of 1 inch (25 mm) wide Velcro strap (hooks on one side, loops on the other) holds the tabs in the slots nicely.  Also, cut about 1/4-inch (6 mm) square holes aligned to the landing gear skewers for rubber bands to pass through to the underside of the plane, holding the landing gear.

MAKE THE POLYHEDRAL (about 10 minutes)

I assume you know how to make a strong polyhedral joint from your experience with the FT Flyer or Nutball.  Do that, now.  The polyhedral angle need not be steep.  I use a 1-1/4 inch (32 mm) VCR tape box (remember those?) as my spacer.  Works fine.  The exact angle isn't critical. 

BEVEL THE ELEVATOR AND RUDDER (about 5 minutes)

Normal 45 degrees on the moveable member. 

ATTACH THE VERTICAL STABILIZER (about 5 minutes)

No new skill here. 

REINFORCE STRESS POINTS (half hour)

A little hot glue and a skewer on the tail-dragger skeg go a long way toward protecting the elevator and your artwork.

I glue a short skewer extending slightly above the vertical stabilizer to protect it when the plane is upside down on the bench.

If you like to reinforce the leading edge of your foam board wings with a glued skewer, this is the time to do it.

I mount a gift card where the landing gear wire meets the foam board.  Your call.

The wing is plenty strong enough for loops and to pull out of high-speed dives, mostly because it's essentially a lifting body; the plane's mass is distributed over the whole wing.  However, if you want to reinforce the polyhedral joints for hand-catch landings, a stripe of fiberglass strapping tape across the kite's ventral "chest" from wingtip to wingtip should go on now. 

MOUNT CONTROL HORNS, PUSHRODS, AND SERVOS (about 40 minutes)

Mount the control horns.  I followed the Flite Test convention of the rudder on the left (port) side and the elevator on the right (starbord).

I mount the servos as far forward as the control rods will reach.  This placement helps get the CG forward and therefore makes the battery placement more convenient.  It also keeps you from needing servo extension wires to reach the receiver.  Such long control rods need a little help staying rigid, so use a couple coffee stirrer straws and foam board trestles. 

TAPE HIGH-WEAR AREAS (about 5 minutes)

I put about a 4-inch (100 mm) piece of packing tape on the dorsal (top) side of the elevator.  Later on, that's where I tape down the tail streamer using painter's tape.  The packing tape provides a smooth surface and protects the paper underneath from wear from the painter's tape.

I also tape down the servo wires to the dorsal side.  Then I lay a stripe of Velcro(r) hook tape to hold down my battery and voltage alarm.

LANDING GEAR (half hour)

The plane is so light that you might not even bother with landing gear.  I built the standard wire gear but using Ping Pong balls for wheels.  Heat a landing gear wire.  Melt a hole through each Ping Pong ball, trying to get as close to center as possible.  A little wheel wobble won't make any difference. 

Frankly, one of the main benefits of the landing gear is to show me the kite's orientation when I'm flying it into the wind.  Often, the kite is side-edge-on to me, so telling when it's turning slightly out of the wind can be a challenge.  The Ping Pong ball alignment shows me.

ADD COOL KITE ART (all the time you want!)

The original Powered Kite had a lightning-bolt theme.  The one I built to test these instructions features a patriotic theme. Any cool artwork will do.  Let your freak flag fly!  (bad pun intended)  Just think:  What would you have bought as a 9 year-old kid looking at neat kites?

GO FLY A KITE!

Tape on a crepe paper tail -- 6 to 10 feet (2 to 3 m) -- to the dorsal side of the elevator.  Make it colorful!

Mount the battery to balance the plane on the CG points.

Hand launch works well.  I find that 60% dual rate and -80% exponential is plenty for relaxing flights.

Post pictures of your own kite!  Make Mary Poppins proud!  (Obligatory show tune reference, check!)

-- Mike