Tuesday, December 24, 2013

Superfly Tuning

Tram has some great advice on tuning a Superfly.  Since RCG posts tend to get buried and lost, I'm copying it here.

tl;dr:  1/8 inch up trim for level flight.

I would definitely go with a CG that suits you. Any time a kit has a recommended CG, that's all it is - a recommendation. Some folks will fly a little more nose heavy, some folks will fly a little tail heavy.

If the plane is laying flat on a table, and the elevons don't have a little up at neutral stick, it's not going to fly as it should, as the nose is being pushed over due to aerodynamic forces.

All flying wings need a little reflex. Essentially "up trim" at level flight. Superfly's need about 1/8th inch.

I'm no Bernoulli, but as a wing develops lift, it naturally wants to pitch forward. What most aircraft use to counteract this force is the tail. Flying wings are missing this. So, a little up elevon (reflex) at the rear of the plane helps to counteract the force and thus, push the nose back up to attain level flight. 

You said previously that your having to use half stick up to keep it level. Try adding some reflex and then adjust from there.. Lay the plane flat on the table and give it 1/8" to start. You may have to add more. Once this is accomplished, the aircraft can be subjected to the "dive test" to find true CG state and adjust accordingly.

Dive test:
From level flight at typical cruise trim, enter into ~30* dive.
Let the airspeed build a bit and let go of the sticks.

If the plane pulls up sharply you're nose heavy.
If the plane pulls up nice and slow, the CG is pretty much spot on.
If it stays where it was or increases the dive angle you're tail heavy.

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