Yaw, how do I get rid of it?

[Airacobra]

Lately I have been flying a Scimitar, the one recently published in Flying Models with a OS 40 FP with a Tornado 3 blade  10-4. I have been noticing that at the top of the maneuver on the downward leg I notice the planes nose pointing in a bit and the tail wagging. What types of things do you think I need to be doing.  I can give the engine some offset, change my tip weight and adjust my leadouts, but what do you think I need to do to get rid of this little annoyance?

[Crist Rigotti]

If it yaws in a little bit on hard inside corners then I'd:

1) reduce rudder offset
2) move the leadouts aft a bit.

[peabody]

Follow Crist's advice...it's sound....
Our aeroplanes are already flying at substantial yaw just by the fact that they are tethered....

[Bob Reeves]

My understanding is Rudder offset will make the airplane yaw out.. pretty obvious result of rudder and engine offset.

You then tend to end up with the leadouts too far forward to compensate for the rudder.. This is OK in level flight but as soon as you do anything the two start fighting each other and you end up with a wet noodle.

[Airacobra]

The rudder offset will not be possible as the Scimitar is twin tailed and no adjustment built in, but the leadouts will be adjusted back and I will let you all know possibly this evening if I can get some flights in tonight. Thanks for the suggestions.

[Steve Fitton]

Keith,

  Keep us posted on its progress.  I battled adverse yaw in my Avanti 50, nose out on insides and nose in on outsides.  Moving the leadouts forward from their original point (which was 1/8" behind CG) didn't really eliminate it, but seemed to reduce line whip, especially in the square 8.  It did some flakey stuff in the overheads, which led to some trouble.....

Steve

[Greg L Bahrman]

Typically on a 40 size ship, according to the line ll program, leadouts should be anywhere from 3/4 to 1 1/4 behind the CG. If you are farther forward as mentioned you will get unwanted yaw. Sure you can fly but eventually you will lose it. Ask me how I know!! If it was me I would start with the leadouts at 1 inch behind the CG. and work from there 1/8 in. at a time.

[Airacobra]

Tonight I only got one flight in, Ni-Starter took a dive on me. Prior to the flight, I moved my leadouts back, but it didn't really seem to help the issue any. Tension was more, but no noticeable difference in the yaw. At no time through the flights do I feel like I am going to lose it. the plane tends to recover from the yaw quickly, but I just don't like the look of it. I will keep working on it. I will check the leadout placement with the CG and report back later. Thanks guys, Keith

[Bill Little]

Lately I have been flying a Scimitar, the one recently published in Flying Models with a OS 40 FP with a Tornado 3 blade  10-4. I have been noticing that at the top of the maneuver on the downward leg I notice the planes nose pointing in a bit and the tail wagging. What types of things do you think I need to be doing.  I can give the engine some offset, change my tip weight and adjust my leadouts, but what do you think I need to do to get rid of this little annoyance?

Hi Keith,

Aaron chased a similar problem with his Geo Star.  After about a year, we never cold get rid of it.  Tried all the Expert advice and it was still there to some degree.  He built another plane and chalked it up to a misalignment/etc., somoewhere.  Only plane we have ever had that problem on that couldn't be fixed.  Sometimes................

Bill <><

[Airacobra]

Okay guys, latest update. I flew again yesterday and I watched very closely as I was flying through the pattern. That ground gets close quick!!!!! What I saw was the top of the airplane on those outside corners. The plane has a small bit of offset in the wings, so it looks like I need to add a tab for a bit more flap area and I will see if that will get the problem resolved. The yaw was induced by the outboard wing being up. Well, that's my theory at this point, I will make a small tab and give it a try.

[Bob Reeves]

Could be as simple as too much tip weight.

[Airacobra]

Okay guys, another update. Four flights today. I gave it more offset in the engine, more tipweight, added the tab to the tip of the flap to increase area and moved the leadouts back. Seems to be doing much better at this point. I made another tab for the tip a bit bigger but have not had the chance to fly it again. Oh yea, I didn't know if this would work or not, but I sealed the hinge line at the flap tip on the outboard wing as well. Seemed to work okay.