RCU Forums - Flying wing

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Hey guys I just put together a flying wing. I have a couple question one is with my elevator is very sensitive and needs only about 1/2 " travel to work very well but I need more roll out of the plane. Should I move my cg forward a bit more? This plane is built for RC combat (not slope combat). It has a 64" span and 12.02 MAC. I have it balanced at 2.5".

Thanks:

Can you get more through on the airlerons?Or make them slightly larger towards wingtips?

For the theoretical location of the CG, consider also the taper and the sweep back of each half-wing.

Use the on-line calculator shown in the sticky post "Aerodynamic Resources and Online Tools".

If you're using center driven strip elevons you may well be running into the same problems as Iron Eagle did in this thread.

http://www.rcuniverse.com/forum/m_7305622/tm.htm

The same solution for his case would then apply to your situation.

From what I read there I should do one of two things either split the ailerons from the elevator and have a shorter elevator on the inboard or go with shorter elevons on the outboard portion of the wing. I'm not sure I like the idea of adding extra servos to run separate control surfaces but have the redundancy in the case of a midair might be the best.

There's no extra servos needed but you would have to cut into the wing to allow installing pushrods from a central aileron servo. The other servo would become the dedicated elevator servo. So still only two servos.

But yeah, the easy way on a wing which is already built is to put two smaller servos out in the wings in line with the separated outboard ailerons and one in the middel to run the separate elevators. If the elevators are split due to a sweep angle at the center line you can run with the existing two "elevon" horns and just make up a solidly joined Y shape pushrod to run the elevators.

The other alternative is to stick with elevons but move the two servos out onto the outer wing positions so that the servos have a straight line to the control horns on the new half size outboard elevons. So again only two servos are used but you relocate them from the centerline out to positions mid span on the wings. With the new 40'ish % span elevons the roll response will be very close to the same as before with the same deflection angle but the elevator response should be cut down a lot by the reduction in area.

Thanks I will give it a try my servos aren't centered on the wing so I can remove about 8 inches each side. I hope it helps some.

If that 8 inches is anywhere near about half the semi span it'll make a huge difference.

Would (running) a (Bellcrant to the serfo increase his (through)?

I allways 2 vertical fins with an elevator connecting them.It helps keep it straight when banking!

Quote:

ORIGINAL: Pathous

Hey guys I just put together a flying wing. I have a couple question one is with my elevator is very sensitive and needs only about 1/2 '' travel to work very well but I need more roll out of the plane. Should I move my cg forward a bit more? This plane is built for RC combat (not slope combat). It has a 64'' span and 12.02 MAC. I have it balanced at 2.5''.

Thanks:

Get some stick-on weights and adjust your CG until it flies the way you want...then glue in permanent weight and remove the stick-ons. It does sound like you have a CG that is a bit aft of where it should be.

Don

Actually if his balance is at 2.5 inches back from the leading edge at the MAC location and the MAC is 12 inches then he's running with a balance at 20.8% of the MAC. That should be pleanty forward enough for a delta wing.

High speed tends to make controls that would be normal for normal speeds become sensitive as well. That's why racing models tend to use very small surfaces and low amounts of travel.

I was able to test fly the changes made to the elevon and it worked well. The plane still a bit slow on the roll rate but the elevator control us much better. I decided to move the servos out a bit further and remove 12" from each side of the elevons.

Pathous, if you're in the ball park now you should be able to use the dual rate setting on the elevator to reduce the elevator portion of the mix while keeping the aileron amount the same or even make it more by using more throw. Then use the dual rate function to reduce the elevator until the roll and pitch are more harmonized.