Help, need knife edge knowledge!
 

Can anyone tell me why my otherwise terrific flying Dirty Birdy pulls to the canopy in knife edge flight? Corrects with elevator but would be perfect if it would maintain it's heading without the elevator deal. Thanks.

ddubya

Help, need knife edge knowledge!
 

Adjust both ailerons down one turn at time until fix

Re: Help, need knife edge knowledge!
 

Probably a tad too much positive wing incidence, which is not easy to change. Raising the ailerons as ocirema indicates will help but I find that changing the ailerons affects other maneuvers adversely. The only solution I've found that works well is using control mixing. A little down elev mixed with the rudder input cancels the adverse pitch without messing anything else up.

Hope this helps.

Help, need knife edge knowledge!
 

Thanks for your help guys. Let me ask you what you think about adding some down and side thrust . Would that improve the situation?

Help, need knife edge knowledge!
 

I would not change the engine thrust unless you see the pull to the canope during down line braking or up line maneuvers.

Help, need knife edge knowledge!
 

I have seen one flyer mix in spoilerons with rudder for knife edge, is this preferable to mixing elevator? Anyone have comments on which would be better?

I suspect it would be model dependent. The guy I saw doing this was flying a Kyosho CAP-232 40 size.

Help, need knife edge knowledge!
 

MalaysianFlyer,

you have me curious about the spoilerons on the CAP 232. I'm assuming ( perhaps wrongly) that the ailerons are located in the normal position on the wing and reflex upward. I'm not sure I understand how that would work. Have been intending to use spoilerons on a freeflight type plane....but would position the spoilerons along the CG about 1/3rd out on the wing. As for knife edge performance, I'm a little fuzzy on how coupling rudder and spoilerons would do the trick.

ddubya

Help, need knife edge knowledge!
 

Spoilerons is the ability to flex the ailerons up.

Help, need knife edge knowledge!
 

ddubya,

On his plane, it had a tendency to pull towards the belly, therfore by adding a little spoileron mix, it corrected the problem. IN your case you would have to mix flapperon in instead, since your pulling toward the canopy. But before you do so, just check out how your plane reacts to flaps being activated. If it tends to pitch the nose down with flaps, then it should help.

There may be a better solution out there, hopefully one of the RCU aerobatic gurus will pop in??? :)

Knife Edge
 

Check and see where the elevator is when the plane is trimmed for level flight. CG and incidence can cause you to put in elevator trim and when the weight is off the wings, this trim affects the knife edge pitch.

A nose heavy plane, for example, will usually carry a little nose up trim, causing the plane to tend to pitch toward the canopy in knife edge. A tail heavy plane would pitch toward the gear.

Wing and stab incidence is also a player as they can affect elevator trim. Changing the height of strip ailerons is an easy way to make a minor incidence change.

Help, need knife edge knowledge!
 

Thanks Ed,

Believe you may be on to the problem as I do balance my planes conservatively. That is, at the forward balance point then a bit more for good measure. It smooths thing out, but may be interfering with the knife edge, as you described. Believe the incidence to be right on.

ddubya