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Questions about Rigging

My RV-6 has an O-320 and a fixed pitch Sensenech cruise prop. I am breaking in a newly overhauled engine and therefore running it harder than I normally would. I have very few hours in this plane <20 and these hours represent all my experience in RVs.

Takeoffs require right ruder as normal.

At 5000 feet, straight and level and full throttle there is not enough left aileron trim to keep the plane from rolling right--slowly but still rolling. Also, I have to maintain some LEFT rudder pressure. More than just resting my foot on the left pedal.

At higher altitudes greater than 6500 feet and at full throttle there is enough left aileron trim to keep the plane level though I still need to rest my foot on the left rudder pedal to keep the ball centered.

In cruise descent, I need a lot of left rudder to maintain coordinated flight. Once in the pattern at pattern speeds < 120 MPH, I need right aileron trim The rudder is a non factor at that point because there is always some wind.

There is a "trim tab" glued to the tail on the left side with a slight leftward bend but as it is even with the trailing edge of the ruder I am unable to reduce the bend without squeezing the rudder and probably bending it more.

As you have accurately surmised I am not a builder and not very familiar with building aircraft. I have read about how to set up the ailerons but when I look at the trailing edge alignment of he ailerons to the wing tips and flaps, there is nothing very interesting to see. The ailerons don't line up with the the flaps and wing tips and when you align one side with the wingtip the other side is not aligned with the wing tip. I think all this means there is some amount of inaccuracy in the build--now 20 years old. Where should I start? I am not very concerned about losing a few knots of airspeed but would like to be able to fly hands off for a few seconds if that is possible. I also understand that at critically slow airspeeds some unexpected behavior could be encountered due to excessively poor rigging or wing assembly.

Lastly, while I am not flying IFR at this time, it is obvious that with the pane rigged the way it is now, pilot workload would be increased just to maintain straight and level. That's not a good thing.

Thanks in advance for your time and advice,
Hank
 
Hank,

In general, you want to pick a cruise setting and set the aircraft up for neutral trim at that cruise setting. Say 2400 rpm at 6500' or whatever cruise setting you expect to use on a frequent basis, with your load (fuel, people, and stuff) in a balanced state left to right.

At that setting (ideally), your airplane should fly hands off with the ailerons in neutral and the leading edge of the elevator counterbalances slightly above the horizontal stab tips.

Your airplane sounds like it may need a rudder trim adjustment and like it definitely needs an aileron trim adjustment. The rudder trim is straightforward, but on the ailerons, the issue could be something like the vertical mounting position of the aileron(s), the trailing edge radius on the aileron(s), or maybe you don't have enough throw or friction in the aileron trim system.

There are fairly easy and simple corrections for all of these things, and a search of this site using terms like "aileron trailing edge radius", "aileron trim", etc. would probably point you in the right direction. With the -6 and its builder fabricated aileron trailing edge bend, the trailing edge radius is a frequent source of roll trim issues.

That said, it might be good for you to find an experienced builder/flyer in the area to help you with the process. If you want to contact me, I'd be glad to help you sort through it, but there are plenty of other people in the area who could provide outstanding guidance.

I can be found at 770 722-4084 or by PM...
 
Thank you for the advice and your offer, Kyle. Are you hangered at KLZU?

Though I have owned the plane for six months, I have't flown for four and half as the engine was being overhauled. I've put three hours on the plane in the last week trying to fly off the first 10 hours according to the overhaul break-in document. In all honesty, I am just getting comfortable in the plane again. I will start taking notes while flying to build detailed descriptions of rigging issues.

If you are around and it's not inconvenient, I'd love for an RV guy to take a look.

Let me ask you this though. Is it normal for required right rudder pressure to change noticeably between cruise and descent in an RV-6?

Let me also clarify the handling. I am not saying it is difficult to hand fly the plane in VFR conditions and flying approaches is always done at slower speeds but the plane does require constant hands-on adjustments. It does have an autopilot that works great but I have been hand flying the plane to get a better feel for what the plane needs.

Thanks again,
Hank
 
I'm based at KVPC - Cartersville. If you know which hangars to peer inside, you can find very good RV guys at any of the <extended> Atlanta area airports.

As to rudder trim, yes, you will see a noticeable change in the rudder necessary to keep the ball centered as you change power/speed. I'd say you could move the ball one width transitioning between full power straight and level (or climbing) to a low power <relatively> high speed descent. So you set the trim to be neutral at cruise and plan on using your feet in other phases...
 
Trim

You need to squeeze the outboard right aileron trailing edge if you plane rolls to the left. Reverse if it rolls to right.
I would get some duck bill seamer tool from home depot or china mart and some paint sticks.
Tape the paint sticks to the inside of the duckbills to prevent marring of your paint. Gently squeeze the trailing edge so it takes the bulge out of the edge of the aileron. You don't need to do the whole aileron just about six inches.
Take a look at your trailing edge and if you can't get a straight edge to lay down on it all the way to the end and can see a definite bulge then this will cause wing heaviness and make the airplane roll.
If you fly solo a lot, trim the airplane for this configuration and live with the roll when flying with two people.
Make very slight corrections to your aileron trailing edge. Do a little then go fly and see if it's correct. If not keep squeezing the edge down the length of the aileron until you get it correct. If you go to far, you can always squeeze the other aileron to get it back to center. I would avoid using a hammer to peen the trailing edge back to a bulge. I've seen more dents then corrected ailerons.
You rudder trim tab can be bent a little more if needed. I used a wedge and taped it to the rudder until I got my ball centered, flying wings level of course. You can keep trimming down the wedge until you get it right. Then paint it and tape it down to the ruddger trailing edge with the UHMW tape from Vans. It's clear and the wedge blends in if it's painted. It looks better than a tab hanging of the back of the rudder trailing edge.
Avery tools sells these wedges.....
 
I have been on some relatively long, three to three and a half hours, cross country flights and have noticed a few things. The real issue is the rudder trim tab is too much. I actually have to hold some LEFT rudder at 11,000 feet and cruise ~2400 rpm and 170 MPH indicated. If I keep the ball perfectly centered the plane flies hands off within normal aileron trim limits. My left foot, however, is not happy.

I can't unbend the rudder trim tab without bending the trailing edge of the rudder but I can cut some of the length which is what I am going to try. I also bought one of those plastic wedges from Avery tools in case I need to remove the old trim tab altogether and start fresh.

It is taking longer to get really comfortable in the plane after several initial problems but I have put on 17 trouble-free hours in the past 8 weeks.

Thanks for the help and I'll update this thread with some results.

Thanks again,
Hank
 
Are the gear leg and wheel fairings installed? If so you might want to remove them and fly the airplane. If they are out of alignment, you'll fly sideways.

Dave
RV-6
 
Make sure you mark where the fairings line up on the gear legs before you pull them off. I know a builder who didn't and had to fly a couple of flights to figure out the best alignment again.


Dave
RV-6
 
I adjusted my rigging by slightly lowering the flap on my heavy wing and slightly raising the flap on the light wing. The builder of my plane did install a nylon wedge on the rudder as a trim tab. Now the plane flies hands off, feet on the floor, ball in the center in level cruise. Needs right rudder on takeoff and climbs... needs some left rudder on descents, which seems to be normal for RVs. Even though the flaps are no longer exactly equal, there is zero tendency to roll with flaps deployed at any amount.
 
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