Rigging help

[gbright]

Had the KitFox 7 a week now and been de-bugging. Cleaned up bunch of stuff like wrong safety wiring, loose connectors, did new CG with EAA scales (it is right in the middle of the CG envelope), etc., etc.

Have flown it 5 times. Seems more sensitive to pitch than my older KF 5 Vixen.

Here's the problem: it wants to turn left. So we lowered the left flapperon and raised the right a few threads at a time and tried it out. The flapperons appear to be straight on both sides now, but I do NOT have the "level the flapperon tool."

Not a lot of help. On last flight, I noticed the ball is out half-a-ball to the right. So I "stepped on the ball," and that helped the left turning alot.

Then back in the hangar, having a pizza, noticed the left wing is higher than the right by one inch. Checked hangar floor, and bottom of the fuselage level points. All level, so left wing is definitely one inch higher.

Will re-rig the rudder in the am, but just wondering about that higher left wing?

All help appreciated, Grant

[t j]

The flaperons will level themselves in flight hands off. If they are not rigged even with stick centered the plane should fly level but the stick will be off center toward the one rigged lower.

The rudder should center its self in flight too. If its out of rig the pedals will not be even when rudder is centered.

One wing an inch higher (more dihedral) than the other should not be noticeable in flight. The fuselage just hangs under the wings slightly off level which may cause the slight off center ball. With the plane sitting on that flat floor level the wings by letting a little air out of the high side tire. Then check to see if the ball is centered.

Slight left turn could be caused by spiraling slip stream hitting the left side of the vertical fin or the left wing has a little more twist (washout) than the right wing.

[jiott]

If you build everything straight, and rig the wings as instructed, I almost guarantee you will have a left turning tendency in flight. This is due to all the left turning effects that are always present: torque effect, P-factor, spiraling slipstream, etc. Most of us have had to tweak the wing rigging to add more washout to the left wing and/or less washout to the right wing. I also had to add a small rudder trim tab to fly hands-off ball centered. None of these things can or should be done by adjusting the control actuation mechanism (assuming they were installed properly to begin with).

[gbright]

Jim and Tom

I should have been more clear about three things:

1) The ball is out to the right in level flight. If I step on the ball (right rudder), there left turning signficiantly decreases.

2) The flappersons WERE misadjusted, right one was up, left one was down. Now both are level with the stick in a a neutral position.

3) If I hands off the stick, she starts a 15+ degree bank left.

I'll have to study about adding wash out.

Thanks, Grant

[jrevens]

If you build everything straight, and rig the wings as instructed, I almost guarantee you will have a left turning tendency in flight. This is due to all the left turning effects that are always present: torque effect, P-factor, spiraling slipstream, etc. Most of us have had to tweak the wing rigging to add more washout to the left wing and/or less washout to the right wing. I also had to add a small rudder trim tab to fly hands-off ball centered. None of these things can or should be done by adjusting the control actuation mechanism (assuming they were installed properly to begin with).

Our small airplanes are pretty sensitive in many ways. Everything being built straight and rigged correctly, as Jim said, is what we aim for, but another factor comes into play when you're flying solo... your weight in the pilot's seat is almost guaranteed to give you a little left wing heaviness. Seems like many, if not most also require a little rudder trim.

[jiott]

I would suggest you first add the rudder trim tab so she flies ball centered hands & feet off and wings level (hold right stick if you need to for wings level). Then if there is still the tendency to turn left bank, you must adjust the wing twist (washout) to correct it. This is done by adjusting the rod ends on the outer ends of the lift struts.

In my SS7 I notice some, but very little left turn tendency when flying solo. I would suggest you tweak the washout to fly straight and level hands & feet off in the loading configuration (solo or w/passenger) you most often fly. I set mine up for solo flight, but with a passenger the difference is almost negligible. Remember, to lift the heavy wing, you want to add less washout (more angle of attack) to the left wing and/or more washout (less AOA) to the right wing. I think I said it backwards on my earlier post.

Tweaking the washout will change the stall characteristics to some degree. If you have to rotate the strut rod ends more than about 1 turn on all four of them, it may be a good idea to go up and do some stalls to make sure you have not introduced a situation where one wing stalls ahead of the other and drops down significantly. You want a fairly nice even wings level nose drop in the stall. Normally, if the plane was built straight, it shouldn't take too much rod end adjustment to correct the left turning and the effect on stall will be negligible.

[Monocock]

Completely agree with jiott.

I've just done the same with a Kitfox that drops a wing when hands off. It sorted it perfectly. Don't start messing with the flapperons.

Here's what I did (last week).

Aircraft wanted to roll/turn right (it's a Mk3 with 582). I looked at the rod end adjuster and worked out that that the wing that was dropping (RHS) needed more AoA. Luckily it was the one with the rod end on the rear strut, so I shortened it by four threads to increase the AoA of that wing. I flew it straight away and it was absolutely perfect.

If your wing drop isn't on the side of your adjustable rod end, just decrease the AoA on the other one by lengthening the rear strut rod end (keeping plenty of thread safety) to balance it up.

[gbright]

Used digital meter level with degree readout to make sure both flapperons were at the same level angle.

The we turned one thread out on the left wing (increase AOA), and we decreased one half turn on the right wing (decreased AOA).

She is just almost perfect. I am going to put full fuel and check again. After 5pm today, there was no wind, and soooo smoth. What fun to fly and not burn 14 gallons an hour!!

Thanks to all for the helpful clues...turns out the wash out was the answer!

Take care, Grant

[rosslr]

I am revisiting this thread as, after 170 hrs, I can consistently notice a slight tendency to roll to the left. I have done the rudder trim adjustments as Jim suggested. Now, while I understand the principle of increasing/decreasing the wing twist by adjusting the the strut rod ends, I have a question. As the jury struts were attached after the initial rigging and fit neatly between the struts and wings, does adjusting the twist by turning out/in the rod ends place extra stress on the jury strut attach points? Is this amount of stress an issue?

cheers

r

[Dave S]

Ross,

I don't believe there is much to worry about.

To be real empirical about it - and I am not sure anyone wants to suffer that much - measure all the distances between the attach points (wing, jury strut, fuselage). Then determine the change in length due to a turn ot two of the rod end (pitch of the screw) Then bone up on your trigonometry and do the math (maybe a bit painful) I think you will find that a person would not be able to even measure changes which would result in any change in stress of the jury strut, nor any bending of the lift strut or spar tube from absolutely straight


FWIW - on our early S7 - I found a slight left (heavy wing) was corrected with no more than one turn on any one rod end.