SonexBuilders.net

I am coming up on 16 hours of flight testing and am noticing that I have to hold just a little bit of left stick to keep the plane flying level. The left aileron is deflected about a 1/4" up and the right one a 1/4" down when flying level. I am going to first try flying without the wheelpants installed to make sure that is not the issue but if it isn't, where do I start it correcting the problem? It really is minor and takes almost an un-noticeable ammout of pressure but it is still something that I want to work on. Do I try adjusting the right aileron down or the left one up? What about the flaps? My right side flap is pretty close to the minimum number of threads at the bearing so I can't extend it lower. Would raising the left hand flap a turn or so help? Any other suggestions? Do they make a end rod bearing that is longer?

Keith
#554

Keith

Visit the Sonex site and look in the video area as Joe Norris gives a good description of situations like yours and how to correct.

Adjusting the ailerons down or up won't really do anything other than cause the stick to be off-center at neutral and increase or decrease the overall camber of the wing slightly. Whatever offset you think you are putting in just gets averaged out between the ailerons by the wind.

I'd probably try raising the left flap a little. If that's not enough, you might end up adding a small trim tab to the bottom-side of the left aileron.

Mine rolls the other direction so is mostly correct when I fly with a passenger, so I haven't fixed it yet.

Be careful about having one flap down farther than the other. You can get a lot of yaw with one down farther than the other. This can cause some discomfort during slow flight with flaps down.

I put a flap stop about 2/3 of the way down each flap. This is a three inch long 1/2 x 1/2 angle of .074 aluminum riveted to the trailing edge of the wing. The stops are set so each flap retracted is at the exact angle specified in the plans for the rigging. I had noticed my right wing flap was always coming up higher than the left when retracted. My Sonex now flies hands off.

The 1/2 in flat side pushes against the flap so it can not push up too tightly to the trailing edge. If anyone likes, I can post a picture. This is not my original idea but something I had seen some of the earlier Sonex builders do. Just make sure any stop you add has no ability to bind a control surface or weaken a structure.

You can also slightly adjust a heavy wing when installing your flap fairings on the side of the fuselage by being attentive to where the flaps need to be to correct a heavy wing.

I hope Sonex will consider adding the flap stops to the plans as these have worked wonders for me.

Jake

The problem on my plane seemed to get worse the faster it flew. I tried but had no luck adjusting the flap pushrod. Eventually fixed it by using a positive control stop.

There are many ways to do it, Here is what I did. A piece of 1/8" 6061 riveted to the rear spar with threaded holes to hold a block of phenolic. Its located it at the wing rib station closest to the flaps 1st rib. On the flap riveted another piece of 1/8" 6061. Used shims between the phenolic and the treaded base for adjustment to get the right position.

I had a heavy right wing. I ended up adding a trim tab under the right flap, near the outboard end. The first flight after installation it was still a tad right wing heavy, so I just bent the tab down a little more and it's been flying straight ahead ever since. My tab is about 6" long and is just ahead of the trailing edge, so you don't even see it unless you're looking for it.

I also had a slightly heavy right wing and fixed it with a flap stop. I think the problem is caused by torsional deflection in the flap drive tube. The left side only has a couple of inches to twist but the right side has the whole width of the fuselage, so deflects much more than the left with resultant loss of lift. The stops can be quite light. I have seen one that is just a bit of angle folded from 0.032" sheet. I made adjustable stops from 8 mm nylon screws that fit into machined nylon "top hats" riveted to the rear spar. The aircraft felt much more stable with the stops fitted.


Peter Anson
Sonex 894
190 hours

Peter,
You make an interesting point about the differences between the left and right flap. Anybody with center controls have a report? I have a ways to go before I fly mine. Just a couple small details left, like wings, engine, cockpit, panel, and canopy.

It's a pretty simple fix actually.
I mentioned this before on another forum about my fix. I used a piece of scrap .025 sheet and cut a blank about 3" x 2.5".
I bent the tab down its length to about a 15 degree angle at approximately 1".
The 1.5" base was used to lay two pieces of 3/4" Velcro base for install on my left aileron. The intent is to fly the left aileron up to counteract the right roll. I mounted this near a rib and approx. and inch forward of the trailing edge. As speeds change the effectiveness increases at speed and decreases in proportion. Slick! Call it backyard aeronautics if you will but, its simple and its effective.
For those concerned about flutter, I can tell you from first hand experience and careful testing its not an issue.
I spoke with the factory before doing this and checked the balance and it only required one washer forward on the balance weight to keep it well within the safe range.
Best part about this is its as permanent as you want it to be. Its removable and changeable without damage to the aileron or any other part of the airframe.
I have dive tested my Waiex to between 197-205 mph over a dozen times to confirm the stability of both the entire airframe and for signs of buildup to a flutter. Smooth and no signs of anything abnormal. This is both a blessing and a warning.
Keep an eye on the speed because in the case of the Waiex you can get to VNE really quick and easy and go right past it without much effort.
In summation, the tab under the aileron works extremely well with no permanent change to the basic airframe. It doesn't show when on the ground and hundreds of folks have crawled on(finger prints to prove it)and around my plane and only two guys ever asked me about the tab.
Sometimes simple really is better.

Larry, Waiex 121YX, Over 400 hrs in three years

I installed a simple bias spring system. The springs are attached to the aileron rods with a hose clamp. The other end goes via a small cable around a 12V motor with a winch/spool drum to the other spring. I control which spring is stretched with a high hat control on my stick. So a few clicks of the hat left or right, and the spool pulls the cable and spring on the heavy side. I installed a similar system for my elevator trim replacing the dial a trim. So when I need to trim out, its all on the hat. Using the springs, I can override the trim with a simple pull of the stick.

I have thought about making this a kit for other builders. Anyone interested? It would include the stick w/hat, motors, springs and relays.