No More Wobble.

16 hours.

Going to have to sum up last week as well.   Last weekend I did the fiberglass layups on the intersection fairings.   I hate those things.  As is typical with Van’s fiberglass, the fit is garbage.   Add my lack of skill to that, and the result is a set of ugly  fairings that just barely managed to get the job done.   I may wind up reworking the whole landing gear fairing mess, but for now, these will do.   I think if I actually make them smooth and trim off the excess, I’ll get a couple of knots out of them, but the process went like this:  Saturday – Fiddle with wet fiberglasss layups all day.   Sunday – trim the extra bits off, install some platenuts for mounting hardware, go flying.

That’s when I noticed the wing wobble.  running flat-out, with ground speed at around 190mph, trimmed up, the slightest bounce on the stick would cause a divergent oscillation..  This is without the autopilot, au naturel.   Bump the stick, the wiggle starts and just gets worse.    So I had to leave it for another week.

This week:

2 hours fiddling, almost 3 hours flying.  I can live with that.   First thing on the agenda was to double check the gear leg fairing alignment.   No issue there.   Next was clocking the governor back a couple of notches on the control shaft to get more RPM on my takeoff run.  It currently tops out at 2549, when it should be around 2600-2650.   One notch is too coarse of an adjustment; I wasn’t able to cycle the prop during runup, so I had to set it back to where it was.    With that fixed,  I went up just to confirm the oscillation, and sure enough, predictable and repeatable.   So I came back down and checked my rigging.  Turns out, one of the ailerons was off.   Not sure how that happened, but whatever it was, it wasn’t enough to cause a problem with the gear fairings and wheel pants off, at least not until the autopilot was engaged.   The AP couldn’t keep up with the oscillation either.    And, because I’d read about it, I checked the trailing edge of the ailerons.  The control surface is supposed to be absolutely flat from front to back, and then it wraps around where the trailing edge is bent.   This being a quickbuild kit, you’d think they’d be just fine.   Not so.  If the surfaces bulge outward at all, they can cause instability, so you do the heavy-wing treatment: Squeeze the trailing edges so the top and bottom are flat and not curved outward.   Even a little convex is OK.   But the idea is to go easy, not even enough to notice visually.

That was the magic bullet.    Hands-off, the stick stayed rock solid.   Repeating the bump test had the wings settle back to trimmed bank angle.   The autopilot was still a little twitchy though.   The fix for that was to move the AP control linkage to the innermost hole on the servo arm.  Less motion, more precise control increments in the stepper motor.   So that was awesome.   Being able to steer the plane with the heading bug is cool.

With everything trimmed up, balls to the wall, I managed to get 192mph ground speed in level flight.   The fuel burn was absolutely decadent, but it was pretty cool to go almost 200mph.   Oh, and the oil door stayed closed, which was nice.

So I did some more speed runs and spent some time getting familiar with the new handling.   A little different with gear fairings.   It doesn’t slow down as fast, for one thing.   I landed at SZP, went back to OXR, then spent some time in the pattern.   Landings are a little different as well.

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