Flipper - Plank flying wing SAL

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 This is a Plank flying wing for SAL or bungee


The dimensions are 

Span = 875mm, Root cord = 260mm, Tip cord = 160mm, sweep = 60mm. 20mm constant cord full length elevons

The wing is hotwired out of EPP and then laminated with thin iron-on laminating film.

The airfoil is PW51 7% thick at the root and PW51 7.5% thick at the tip. It has a 1.5 degree washout and a 45mm dihedral at the tips.  It has one 2mmCF spar glued to the bottom positioned at 40% cord. There is also a spar on the top surface biased to the rear to avoid elevon reversal. Two 9g servos are positioned vertically into slots cut on the top of the wing. The position of the servos are driven by the thickness of the wing at that part and distance from CG. The full length elevon is a tapered 3mm balsa with fiberglass lamination. ....Note I had to increase the elevon cord at the tips by 12mmto improve the control response (after the first flight trials)

The fuselage is a 3mm CF rod glued onto the bottom of the wing in a slight groove, and extends in the front and rear. The vertical tail is coro, and one of the flute slides onto the CF rod. The front end of the fuse has scrap balsa pieces  glued onto the CF rod and the battery and Rx is taped on top. The front end has a plastic tube which slides over the battery and Rx  to make is more streamline. 

CG is at 60mm. The bungee hook is attached 1.5 inch ahead of the CG .

The 1s 350mah gets connected directly to the Rx via a jst connector. As there are two servos and the elevons are small this direct connection provides sufficient power to power it adequately...No need for a bec.

AUW : 200gm.. with a wing area of 18.354 dm sq, it has a wing loading of 3.59oz/sq ft or 11gms/dm sq and a WCL of 2.55

After the maiden flight which was SAL a few changes were made:- 

- the CG was moved to 60mm 

- the elevon tip cord was increased by 12mm and matched to 60% of the wing with a taper.

- the bungee hook was moved to 30mm ahead of the CG

These sorted out the initial configurations. It has a "launch" and a "normal" flight mode configured in the Tx. The "normal" mode has a slight up trip (the difference is 5). Bungee launch is done in the "launch" mode and at the apex it is transitioned to "normal" mode

It is a very rugged / tough aircraft, and flies beautifully. 

Here are some flights videos on a very windy day. During one of the launch I forgot to switch it back  from "normal" to "launch" mode and it looped .. SO NEED TO REMEMBER IT. Some ballast would help during windy days.

https://www.youtube.com/watch?v=gj3I0pr0IiE

https://www.youtube.com/watch?v=z6seo9Za28c


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