Plank flying wing 60"

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A "plank" flying wing 



Details
1. Span 60"
2. Root Cord : 11.5", Tip Cord : 7.5"
3. Airfoil : PW 106
4. AUW : 605 g

It is a "plank" flying wing, with very moderate taper.
The wing is "hotwired" out of EPS a.k.a "thermocole". It has a 1.5 mm X 3.0 mm CF strips glued on the top and bottom surface of the wing to act as spar. The whole thing acts as a beam, and with the CF under tension becomes very stiff.. and is very light weight.

 In the past I used to cover the foam with paper. This time, it has been covered with monokote, ironed-on. With some testing, the suitable temp was found which stuck & shrunk the film without damaging the foam. The wing covered with monokote, came out very good. The elevon is a constant cord elevon @ 10 % of wing area

some pics

The hot wired cores


The reinforced roots with the joiner tubes. Had to use some polyurethane glue to harden the grooves, and fiber tape to reinforce the whole area


A picture of the tip showing the airfoil section . The trailing edge / ailerons  is a 1 inch triangular balsa section. And it is full length, approx 10% of the total wing area

The




First flight was good, the CG and thrust angle were proper. ....  A bit twitchy in pitch because of the shot moment arm, which was fixed by dialing in expo in the TX. 

Some mods after the 1st few flights


Added vortex generators to the outer part of the wing. And increased the tail area to enhance yaw stability. The vortex generators are made out of plastic card. 2.7 cm long and 1.5 cm high. 1 cm was above the surface of the wing and, 0.5 cm deep section pushed into the foam of the wing


A cardboard template was used to draw out the position of the vortex generators.  The vortex generators were aligned at 15 degrees from the perpendicular to the leading edge... i.e the airflow



The placement of the vortex generators was such that the training edge of the VGs were at 16% cord. A line was drawn on the wing and the and the template used to mark out the VGs. A sharp knife was used to make a thin groove according to the template. The VGs were then pushed in, upto the 0.5 cm mark






Tested it with the VGs..She does not stall!!!.. On cutting the throttle, letting her slow down, and pulling up , only thing which happens is the nose drops and gently.... even wing rocking is not perceptible..  no tip stalls ......Very happy with the vortex generators.
Now she has all the good characteristics.. a good glide ratio, no bad stall characteristics,  steady flyer.. looks like the VGs have bettered the already good glide ratio


here is a picture of the whole aircraft.... with the vortex generators... and extended tail




A flight video of the aircraft.. (in a confined flying field)
https://youtu.be/sGBpDkHChYk


Some pic courtesy our superb photographer Ranga. Below is my favorite picture, (courtesy Ranga the fantastic photographer of PC) , .. this is not photoshoped

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