Wing Rock, Tip Stall

[eblenkle]

Hi All

I have an older 47 inch Yak 54 that I have been trying to tune up because it just would not behave. Wing rock in a harrier and tip stall if you got near the stall point.

A flying buddy asked if I had measured the wing, he said if the tip is not the right proportion to the root that it will wing rock and tip stall.

I went home and measured the wing. This is what I found:

Wing Root Depth = 1.4375 In.
Wing Tip Depth = .75 In.
Wing Root Chord = 11.9375 In.
Wing Tip Chord = 6.25 In

Divide the WRD by WTD = 1.91667
Divide the WRC by WTC = 1.91

.3% difference. When the wing stalled, the whole wing stalled! Apparently the idea is to stall the root of the wing without stalling the tip, so you remain in control even though you are now hanging on the prop and not really using the wing for lift.

I taped some 5 In. strips of spruce on the thickest part of the wing starting at the root and extending straight toward the tip. Because this is a symmetrical wing I did the top and bottom of the wing.

Harriers are not rock solid, but now the plane can slow and bring the nose up without getting squirrely on me.

Note: You may notice I have not mentioned any manufacturer, that does not matter! I am posting this in case someone else needs to tune up their plane.

I am much happier with this plane now! Only took two months to figure out what was wrong and how to fix it.

Best Regards
Ernie

[RTK]

Can you post a picture?

[eblenkle]

	Quote: Originally Posted by RTK
	Can you post a picture?

Yeah, not much to show. Just laid spruce strips and taped them down.

Ernie

[eblenkle]

Pics of the 1/4 balsa stock added in to help stabilize the wing rock

[RTK]

Thanks, I will give that a try, I have one that really rocks and not in the good way.