Fliegenmong

Hi All

I have a vexing question about aerodynamics, it should be noted that I have been involved in aero modelling for many a year and my Father before me AND his father, I have also held private pilots licence, and yet I cannot figure out this problem

My Son flies an ELECTRAFUN, simple pod and boom type a/c three channels elev. Rudder and on or off motor. He / we have flown it many many many times, and after so much wear and tear it was time to purchase a new wing, and new tail feathers, (Vertical & Horizontal stab).

Out to the flying field for test flight – sharp dive to the left. Bend some right trim into the vert stab, still a sharp dive to the left but controllable with full right rudder after even more trim was bent in – however as soon as the motor is cut the application of full right rudder still produces a diving left hand turn!!!

Now this should not happen naturally, Radio has been range checked no glitches or anything of the sort.
To date I have moved the wing toward the (left) down going wing. No result, I have jacked up the leading edge of the down going wing with balsa shims, no result. As a last resort I made a helluva big ‘Barn Door” fixed aileron (down) on the wing that drops (left), and STILL it keeps diving into a left hand spiral, even though now there is slight tendancy to roll right under power as the aileron is so big. Full trim is to the right , maximum right deflection, left is more really just centre – still spiral dive left. CG is within range, nothing has changed except the aircraft – as mentioned – now has a brand new wing, brand new vert & horizontal stab, everything is needless to say all square tail to main plane angles of incidence are correct or at leaqst unchanged and I can still not figure out why this airplane still dives to the left!!

We are of a collective 65 odd years of experience and I cannot figure this out! Please what am I missing!?!?!?!

BMatthews

I'll bet the wing is warped or there's something seriously wrong with the airfoil shaping on the new wing or the wing and tail are not in proper alignment. Check the wing to ensure that it's square across the fuselage and not skewed. Also check that both panels are of equal span. And finally check that the airfoil is the same from one side to the other. Pay particular attention to the leading edge.

Use a measuring tape and a center line reference and check the diagonal measurements to the wingtips. It need to be right to less than 1/16 inch. Also check that the span is equal on both sides first.

This is far more about some building inaccuracy or alignment issue than it is about aerodynamics.

john_s3

My Feedback: (1)

Could The Wing Or Tail Be Flexing In Flght????I Would Try Another Set Of Wings Or Renforce The One You Have.Just A Wild Guess.