|Jul 09, 2014, 11:03 PM|
United States, CA, Palo Alto
Joined Oct 2013
47" Swallow-tailed kite EP bird glider
Many people have asked me about the Swallowtail kite and plans, so here it is, plans and some info. This was the 3rd bird plane I built the first two were the 42" eagle based on jacoda88's plan http://www.rcgroups.com/forums/showthread.php?t=1035283. Great fliers.
After building those two, I got to thinking about other birds and came across Youtube videos of the Swallowtailed kite; what a graceful glide with the fancy tail. So I set out to design based this on same idea as the eagles with a simple boxed fuselage; my first wing was a cambered sheet of form but because of the leading edge curve, the part farthest forward had too much camber and the plane had way too much pitching moment and would nose down when it picked up speed. yikes! Lucky for me I came across the KFM threads which gave me the idea to try the KFM, which turned out pretty well; easy to conform to the curves and layers gives it the layered feather look on the top. the first KFM wing flew pretty but sadly I lost that bird a couple weeks later at a local park behind some buildings, trees, who knows: MIA; poof gone. The second version of the KFM wing I think works even better. This is the one shown in the plans has a shorter chord so gives it a sleeker look; also I simplified the curves on the KF layers.
I used the gray 3mm 30"x10" Depron from RCFoam, seemed to be the cheapest per area (yes, I'm cheap). I cut the main part of the wing and then added the tips out to 47"... I think the wing took just 2 sheets; don't quite remember for sure. Definitely can do with with under 3 sheets including the swallow tail fins. the 3 layers of the wing are glued together with Gorilla glue (can use either the original yellow or the fast drying white). Cut out the ailerons from the wing and bevel the leading edge of the ailerons underneath at 45 degrees, then Scotch tape top hinge join the ailerons back to the wing. Servo for aileron is a HXT900 9g servo. Control rods bend from just wires (no carbon as the distance from servo to horns is pretty short).
There's a 3mm carbon tube in the 2nd layer. Later, I added a 3mmx1mm carbon strip (HK) to the bottom to make it more rigid for high wind flying. The strip is gorilla glued into the bottom layer after digging a grove 3mm deep. Then tape over to smooth over.
Leading edge of wing is simply sand TLAR for a smooth curve to about 27-30mm back from leading edge. Bottom leading edge also rounded (I was thinking of an AG03-like profile with the KF when building this wing. But I'm now convinced that with these types of quick build foam wings, TLAR is all you really need, pretty forgiving and it'd be hard to that that level of precision anyway, for me). I also sanded down the trailing edges of top and middle KF layers to about 1mm to smooth out the steps (I think I might have destroyed much of the benefits of KF by doing this; oh well, it still has a pretty good lift and stability).
The body is built in the style of the jacoda88 eagle. hot glue the sides to the bottom, hot glue the back top to the sides. For the head section, I added some 3mm EPP to the inside to make it tougher for crashes. Fuse is build up from 2mm Depron; you can use 3mm also.
Next I laminated a couple layers of 3mm EPP and used that for the firewall. Motor is then mounted to the motor mount, motor mount screwed into basswood ply 3/16" and basswood hot glued to the EPP firewall. pretty simple. there is a slight down thrust and right to p-factor compensation. Hook up the motor to ESC. then hot glue the top front section on to the fuselage.
The elevator and rudder servos go inside at about 2/3 way from leading edge; hot glue on bottom and side to fuselage. Cut out small slit on each rear side panel to feed through the control rods. I use typical wire and carbon rods with wire shrink tubes; connected with modified z-bends. rear end of rods near the horns have V to adjust length, control horns make from gift card, hotel entry card, plastic.
Held on with a couple of bamboo skewers pierced through the fuselage at locations TLAR. reinforced with extra layer of Depron. hotglued in place. Then use a couple of rubber bands (bag of #64 from Walmart) criss-crossed over wing to hold in place.
I cambered the top of the top of the tail fin leading edges then hot glued together at 120 degrees; then hot glued to the back top panel. I later added a 1mm carbon rod to the bottom of the tail fins lengthwise to give it more stiffness; only marginally. My next one would be just simply tape top and bottom; I think that would be stiffer than that thin rod. I also used 2 carbon 1mm stays from the fins to the fuselage to keep the fins in good position with the fuselage and from ripping off the fuse in high winds and at fast speed.
I set the tail to v-tail in DX6i. right servo goes to elevator, left goes to rudder. need to reverse elevator to get the correct defection (servos are mounted upright).
In light winds I fly with a 300mah Turnigy NanoTech 2s to get more float. Motor strong enough to get up high quickly then glide/soar.... i get about 20mins of power up glide down several times. This bird thermals well, lots of fun. once in thermal it pick up speed, just add aileron and rudder trim and it'll fly itself up the thermal! I've flown an hour on 300mah once.
The rudder function is pretty weak, need to crank right left a bit to get it to yaw. But aileron and rudder cover for that weakness.
When the wind picks up, I put in a 460mah NanoTech 3s and get some fun fast flying. The extra weight steadies out the flight in the big winds.
It's pretty fun to do some acrobatics with it as well, can do inside/outside loops easily, rolls a bit slower, inverted flight easy. I like to summersults/.flips with it; fly straight up, cut off power and just before comes to a stop, add full up elevator and it'll just do a quick summersult flip..
Anyway,, I've lots of fun with it. I've had birds come after it, I've thermaled with the local turkey vultures, met many people thinking it was a bird.
Wanted to share the enjoyment. Good luck with your build. Best thing is the total cost is about $45 and a couple nights of build time.
motor: Turnigy 2211-2300KV
ESC: Turnigy Plush 10A
prop: GWS 7035
servo: HXT500 5g servo for elevator and rudder, HXT900 for ailerons
receiver: Lemon-rx featherlight DSM2
KFM section; 3mm Depron, 3 layers
carbon rod pushrods, wire connectors
control horns from plastic gift card
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