50cc AW Yak54 WINGS A ROCKIN!!

[nesikachad]

This has probably been beat to death, but I'm stuck.

The wings rock something fierce when doing elevators, harriers.

My lateral CG is spot on. I've checked it, other guys have checked it (all very good pilots)

My forward/aft CG is pretty close. I'm just a smidge nose heavy. Inverted flight requires just a wee tiny bit of down elevator to hold elevation. Flat spins are ever so slightly nose down.

I've tried mixing in spoilers and it kinda helps, but it's not the fix, seems more like a band aid. When attempting harriers down wind it seems to be better so long as I match air speed to what the wind is doing. This suggests to me that if the wings are fully stalled, then it improves. Am I on the right track with this?

My next idea is to get more weight in the tail, although I'm not real optimistic.

Ideas welcome!!

Chad

[Huckeneer]

give it a touch more power. The wing are trying to fly giving it a rocking motion. By giving it more power you are increasing the angle of attack an allowing the plane to be held up more by the prop.

[bodywerks]

Pretty much what he said.
Also, how much elevator throw do you have? You need 40, preferably 45+ on the elevators and they must both throw the same throughout the entire range of travel.
And yes, move your CG back if you want to 3D, at least to the very aft recommended CG or another 1/8" or so.
Flying a plane inverted doesn't do much for CG reference so don't base it on that - just fly it at different CG's and see what you like best for your type of flying.

Do another test - get your idle nice and low but still reliable. Take the plane a couple hundred feet up, point it down and after a hundred feet or so slam in full up elevator and just hold it. It should just parachute and basically stay there. If it snaps out or starts to rock the wings with no inputs from you then something is wrong...
Every plane has its sweet spot, what you may be fighting is the transitional phase of getting to that sweet spot. Like Huck said, you probably just need more AOA.

[nesikachad]

Thanks!

Parachutes used to result in a violent snap to the right. My elevator halves were not matched up properly at full throw. (now fixed)

I'll fiddle with CG and the idle

We'll see what happens this afternoon.

Thanks again.

C

[jamesrxx951]

when i purchased my yak i talked to mark dennis before i made the decision on the yak and he told me that the wings will rock some in higher alpha manuverse,compaired to the extra. but he said the yak flys straighter.

[exeter_acres]

what huckeneer said.....


increase your AOA

[Bill Clark]

I had the same problem with my Sukhoi. What is hppening is tip stall at high AOA. Remember in High alpha airspeed is still high over wing close to fues from prop wash but almost zero at tip and wing taper doesnt help either. I made some spill plates (aka side force generators) out of 3/32" clear polycarbonate (lexan) plastic I got from home depot and it made a huge difference and you cant see them in flight and barely when up close.and they come on and off easy. it is important to make sure the plate is slightly ahead of the LE or they will not be effective. The cool thing is it enhanced the KE performance to the point where it isnt much harder to fly a whole flight like that (exluding TO and landing). I can throw up pics if you want. They are on the plane in my avatar


dah, pics are in my album

[jamesrxx951]

some of the QQ planes had the same thing on the wing tips. i wonder if he put those on for the same issues?

[nesikachad]

Please do. I've tried about everything I can think of with little success. I have the CG back as far as I dare. and the only way it'll do anything without wing rock is if my AOA is ridiculously high, at this point though it's a real handful.

I know it's not me, my TOC 85 cc yak is rock solid no matter what I do to it.