Flying Wing Testing - No Stabilizers and Expos

While adding the AMP to the Shrike, we wanted to understand Flying Wings a little better and explore expos.  We incrementally increased expose to 0%, 30%, and 60%, then flew the Raptor with the existing vertical stabilizer at 100%, 50%, and 0%. We were surprised to find that it flew just fine with 0% stabilizer! This test was in low wind, however, so it will be interesting to try it again in higher wind and to hear from others' experiences.

-Trent & Nick

Tx: Flyer9x with er9x firmware by ParkeFlyer
Battery: 20C 2.2Ah Sky
Servos: T-Pro 9G 
Motor: Optima 450 2220-1800KV
ESC: Exceed RC Proton 30A

Produced by Trent & Nick in Arkansas, USA
Main Camera: Panasonic HDC-TM900K
Video Editing: iMovie

Views: 1789

Comment by John Arne Birkeland on May 26, 2012 at 4:43am

I love you enthusiasm.

You wing has relatively small control surfaces, so expo is not really needed. On a 3D aerobatic airplane with HUGE control surfaces that can more close to 90 degrees each direction, you want expo to calm things down during normal flying.

Comment by Gary Mortimer on May 26, 2012 at 5:04am

+1 with John says. Don't add too much of anything in your radios it makes sorting out AP integration much harder.

Comment by Ryan Beall on May 26, 2012 at 12:30pm

One thing to think about with this kind of design is the aero going on around the tips.  Ideally you have a little twist in the wing to reduce the lift distribution at the tips to prevent tip stall.  Winglets in this case also will help "fence-in" the stall and make for a very docile "deep stall" characteristic.  That's really what you want to test in the no winglet configuration.  You can take flying wings well below stall and do sort of a "falling-leaf" landing which can be a pretty good replacement for an emergency parachute type landing.  The downside with no winglets is that you will probably affect your slow speed characteristics and have a pretty crazy tip stall tendency.  It's clearly not that noticeable on the raptor because the wing loading is pretty low.  With something that has a higher wing loading say the shrike, you might get yourself into unrecoverable spins even at higher altitude if you get the speed too slow.  Do some stall tests up high and see if it's worth it to you.  

Love the work guys!  Learning by doing is always the most rewarding. 

Comment by Gerard Toonstra on May 27, 2012 at 11:18am

These winglets force the tip vortex entirely to the outside, allowing the entire wing span to produce lift. This therefore increases your aspect ratio a bit and this lowers stall speed a bit. Doubt that this impact is noticeable on model aircraft though.

The characteristics of "dutch roll" are also changed and typically increases a bit (this is procession around a vector). Dutch roll is usually noticeable after changing course. It occurs because the winglets are attached at the end of the wing, creating a significant momentum of rotation around the midpoint of the aircraft. When the procession occurs, the projected surface area into the direction of movement continuously changes a bit and therefore the drag.


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