Thread: Discussion Skywalker 168cm FPV plane
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Old Nov 14, 2012, 08:42 PM
Mtrhd0024 is offline
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Skywalker banking issue...

Whats up guys!

I have a V5 Skywalker I built up slowly over the past year, taking my time to do it all right... I only say that to reinforce the fact that I've been patient with this thing, and didn't take any shortcuts with the build.

I have now made about 10 flights with this thing (no crashes so far, fingers crossed!) and it insists on wanting to bank to the left, to the point where i have to use full right aileron to get it to fly straight and level, and if I hold it full right for about 10 seconds, it will SLOWWWLYYYY start to bank to the right. Even with the trim set to full right aileron, it's only marginally better. It's so bad, that I finally caved, and added a bendable aluminum trim tab on the right wingtip to try and help drop it back down. I flew it with that for the first time today, and it kinda sorta helped.

I'm beginning to think this thing has roots in NASCAR or something; I pretty much only fly in wideee left hand circles around the field, because even flying straight is a challenge!!

What puzzles me is, there is nothing obviously wrong with the build that would cause it to do this. I've never had a plane bank so badly to one side that I couldn't trim it out, without something obviously wrong.

A few of the things I've checked so far:
a) All control surfaces are in a neutral position before takeoff. The rudder is centered, and ailerons are even with each wingtip.

b) The tail is not twisted. Sighting from the front or back of the airplane, the main wing, and the horizontal stab are parallel with each other.

c) Its not the thrust angle of the motor, or P factor, the plane still banks to the left in a power off glide. Makes approaches and landing interesting (not in a good way)

d) The main wing is balanced from side to side, within about 1cm from the very center.

e) The angle of incidence of each wing half is the same.

A few build details that might help:

Its a V5 Skywalker 168 with the single CF Spar, which I beefed up by machining down a dowel, and then sliding it inside the CF spar, and gorilla gluing in place. This was to prevent the possibility of the CF spar snapping, and the wings folding in the center. Sounds heavy I know, but the dowel actually weighed less than the CF spar after machining. The wingtips (past the main spar) are reinforced with CF ribbons, inserted into the wings edgewise, to prevent the wingtips from folding.

All control surfaces, including the flaps, were cut free from their respective wing, and reinstalled with Pinned hinges to reduce the stress on servo's. I tossed the standard skywalker "press in and glue" control horns in the trash, in favor of screw on Dubro control horns. Each control-surface push-rod was made from CF rod and nylon clevis ends.

The motor mount is custom made from 1/8" ply to accommodate the somewhat oversized (but common) NTM 35-36A 1400kv motor & 60amp plush ESC power combo. Prop is a nicely balanced 9x6 APC.

The wings are permanently joined at the center, and a single 6pin multiplex connector handles all 4 servos in the main wing. (2 aileron, 2 flap)

Payload consists of a dragonlink receiver and RVOSD5 & anti-vibration mount in the belly, a 3s 4,000 or 5,000mah lipo mounted in the nose, the Video TX and 1.3 cloverleaf antenna on the tail boom, and the video cam mounted on a pan and tilt on top of the fuselage, just in front of the wing. The dragonlink antenna is mounted vertically in the tail.

My only other observation is that I need to check my CG again, because I think its a bit tail heavy. It requires a bit of nose down trim to fly well, and I think either a GoPro, or another lipo up front would help that.

What gives!? I feel stupid even asking this, because it sounds like it would be something obvious, but I've been pretty thorough with this plane.

Since I don't get to fly often, I've been racking my head for the past 2 months (since I first flew it) trying to figure it out... I'm almost at the point of thinking its a manufacturers defect in my wings, (something about the wing geometry I can't easily see or measure) and I'm kinda tempted to order a 2nd set of wings from BEVRC, possibly the new 1900mm ones, to try them out.

Anyone else have this problem?

I can post pictures of everything later on tonight if that would help.
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Last edited by Mtrhd0024; Nov 14, 2012 at 08:48 PM.
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