Used airplane- Heavy Wing, suprising solution...

[fodrv7]

Originally Posted by coastalflyer

Best aerodynamic efficiency is achieved by banking into the p-factor slightly, and actually your butt will tell you that. If you listen to your butt that is. I like to listen to my butt.

I flew only one turbo prop. THE F27. My first twin. Bit of a leap from C150.
Anyway, engine out we flew with 5? bank in to the live engine. Now I know why.
As you say. Poaching wisdom.

Pete.

[kentb]

Originally Posted by GrayHawk

My thinking matches yours. I bought a flying RV-6A and have been working on the alignment. The plane had a large aluminum trim tab on the left side of the rudder, to give roughly straight flight at cruise. When I got to the empennage checks, it turned out the VS actually had RIGHT offset (the 6 was originally spec'd at 0 offset). After consulting with all the experts and everything else I could lay my hands on, I corrected the VS offset to approx. 1/4" LEFT and took the rudder trim tab off. Plane now flies straight at cruise and is 8 mph or so faster. In my case, RIGHT VS same as left rudder, which was then counteracted by left trim tab (right rudder). Moving the VS LEFT acted as adding RIGHT rudder & trim tab no longer needed. Clear as mud, right!

Rudder control feels much better too.

Did changing your VS to correct yaw have any effect on "wing heavyness"?

Kent

[GrayHawk]

Originally Posted by kentb

Did changing your VS to correct yaw have any effect on "wing heavyness"?

Kent

The correction to my VS was done because in my assessment, along with those of several A&P/builder/experts, the plane was not built correctly to begin with. I went past the Van's spec of zero offset for the 6, due to the fact a couple of 6 builder friends had built in left offset with good results on their planes, and Van's had changed the design on the 7 to have 1/4" left offset built in. The VS correction was more or less a gross correction to get out of the way before working on the finer details like "wing heaviness" or roll. Those checks and any fine tuning are next; however, the plane is flying so much better now, I'm not sure what else I would change (maybe fairing & pants alignments when I put the new ones on).

BTW: Along with the VS correction, a small correction to HS sweep was made at the same time. Prior to this I had straightened the trailing edge, left side VS, where it had seemingly been bent outwards to allow rudder clearance. These all had positive results.

Left to do: The right elevator trailing edge is approx. 1/2-3/4" higher than the left elevator trailing edge (elevator horn drilling). I haven't worked up to doing that yet. After this is done, then some more test flights to see what is left. If I did have significant "wing heaviness" that could not be explained; I'd check flaps, ailerons, alignments, hinges, and remove the permanent trim tab on the right aileron.

[jcmcdowell]

I would concur- the VS adjustment was a 'gross' tuning not meant to improve the Vans design, but to correct/overcome some issue with the original build. The results were so dramatic that is was like flying a completely different airplane.

[N375JS]

JC

I have a slow built 6 and in the manual it states that if I experienced a "heavy" wing the manual says for the 6, hopefully you can apply to the 7.

"The answer is to change the ailerons themselves by altering the shape of the trailing edge. this eliminates any fixed tab for the rudder, but requires a light touch. If flight tests reveal a rolling tendency, cover the trailing edge of the aileron on the "light" wing - the one coming up as the aileron rolls-- and use a hand seamer, or just fingers to squeeze the trailing edge along the length of the aileron very slightly. The results should be barely perceptible. Fly the airplane to gauge the results. Decreasing the trailing edge radius may also increase the stick forces in roll, which is another reason to proceed cautiously with this method."

You can also tap the trailing edge of the "heavy" wing as well.

Good Luck

John

[jcmcdowell]

I think this is only good for fine adjustments as well. 10lbs of pressure is like going to the gym on an 1hr flight. 2lbs of pressure is in the fine tuning range.

I adjusted the ailerons last night- test flight today to see what the results were. There was about 1/4" of right aileron (it was lower than the flap) to be adjusted UP. This makes sense- low right aileron causes left roll (i.e heavy left wing).

Getting better every flight.

[jcmcdowell]

Next- I have to jack the plane and level all axis to take some datum points. I believe the wheel pants need adjusting, can't really tell about the leg fairing yet. The wingtips both 'appear' to dip down below the ailerons at the tips.

The plane flew really light at the controls, the wing heaviness was not noticeable at climb, only at cruise above 150mph (ball centered). The plane is certainly much much more pleasant to fly than before the Vertical Stab adjustment.

I'm going to wait to make more adjustments until I fly off my insurance time. I don't want to tinker and take the plane out of service for weeks right now. I'd forget what little I know about landing a taildragger.

Tomorrow I go to Mike the mechanic at the field for help tuning the carb. I get a erratic rpm drop (50rpm) when the throttle is at less than full power (2100-2200 rpm) and the mixture is leaned out- checked the mags, not them. You can see the erratic drop on the tach. I'm also only getting about 2200 rpm max at takeoff. I would like to see 2300, but it may be the prop (not sure the angle).

Still getting over 1100fpm climb with 2 men and full fuel at 90kn (CHT's all under 400).

Fun Fun-

[fodrv7]

Originally Posted by jcmcdowell

Next- I have to jack the plane and level all axis to take some datum points. I believe the wheel pants need adjusting, can't really tell about the leg fairing yet. The wingtips both 'appear' to dip down below the ailerons at the tips.

-

Jim,
Glad you are making some progress.

I used a Laser Level to set up my Wheel spats, and fairings.
It took all the frustraion out of the job and proved to be very accurate.

There is a good description at http://www.vansairforce.com/communit...ht=laser+level

I had also been meaning to suggest that you use the same sort of Laser Level to check the straighness of your fuse, by sitting it high above the nose and projecting it down the fuse at the Vet Stab and checking its' alignment with the centre row of rivets on the top of the fuse.

Pete.

[jcmcdowell]

Thanks Pete- that's a good idea.

A friend has a digitial level and with a laser level- should make quick work.

The part I'm dreading is jacking and level the airplane. I work alone, so this requires some coordination.

Thanks

JC McDowell

[DaX]

Jerry, If you would like a hand, I'd be glad to come help, just call me when you're ready to do it.