Fitting Flap and Aileron to Wing page 1

August 8, 2010

Now it's time to fit the aileron and flap to the wing.  This part of the build process must be approached carefully and thoughtfully.  Proper alignment and positioning of the flaps and ailerons in the wing will not only affect the fit and finish of your airplane, but will also affect the flight characteristics. Take your time and get this part as perfect as possible.

Wife Michelle, came out to hang out with me, so I put her to work removing the paint from the insides of the hinges, so the bearings could be installed.  Here she is using the dremmel with a small drum sander to remove the paint and open the hole a bit to get the bearings in:

The holes need to be opened enough that the bearing will almost go in but not quite go in all the way.  Note the rubber mallet that Michelle used to tap them a bit.

Looking at the plans (drawing 13) you will see that these bearings should be a "press fit". This means they should be snug enough that you  cannot just press them in with your fingers, but will need to press them in with something like a hydraulic or arbor press. If you can simply slide them in with your fingers, they are too loose. 

A "press fit" will prevent the bearings from spinning or being loose in the hole. If you have a hydraulic press, that's fine, but since we are trying to build this airplane with minimal tools, we used a "redneck press" to install our bearings.  Here it is:

As you can see, this involves a couple of sockets and a "C" clamp and four or five hands to hold it all aligned while you tighten it. The one socket is not aligned properly. It slipped just as I took the picture.

You could also do this on a bench vise. One socket should be small enough that it will slide inside the aileron mount hole and the other one large enough that it won't slide inside. The hole is opened up enough that the bearing will not slide in with your fingers but will slide in part-way.  There should be some resistance. Once it's to that point, use a press or a set-up like we did in the photo above to "press" the bearing the rest of the way into the aileron or flap mount. Here is what it looks like pressing the bearing in using a bench vise:

Here is the bearing after being pressed into the mount. Note that it should be centered side-to-side in the mount:

We also temporarily installed the rod end bearings in the aileron drive push rod.

Next drill out the aileron and flap hinge mounts in the location shown on drawing 13. Clamp two of the hinges pieces together and match drill them. Start with a small drill bit and gradually open up the hole to 3/16":

One note of Caution: - When measuring for these holes, don't rely on just the radius from the curved/rounded edge of the hinge to the hole. The radius is given, but should not be the primary way to locate the hole.

Once you have the holes drilled out, temporarily install these hinge pieces to the aileron and flap mounts on the wing.

If you want to, you can drill out the pop rivets that hold the braces on the aileron/flap and then use some "C" clamps to clamp the aileron to the hinge pieces. Mark them for location so you can reinstall them correctly later.

I opted to use some large slide clamps with blocks of wood as spacers, to clamp the aileron to the wing hinge mounts.

Now try rotating the aileron up and down to check for clearance. When I mounted mine, I found that the sharp edge part of aileron nose skin actually comes into contact with the bottom wing skin and cannot rotate up, as you can see here:

I was able to trim the wing skin about 1/8" and still have good edge distance for the rivets, but still found that the aileron was almost touching the wing skin.

The final solution was to make some .125" thick aluminum spacers (3/4" outside diameter, with a 3/16" hole in the center) and place one of them between each hinge mount leg and the rear wing spar capstrip:

That spaced the aileron outward an additional 1/8", giving me enough clearance between the wing skin and aileron nose skin. You need a minimum of 1/8" clearance. (Note: on the newer wing kits from Avipro, this issue has been fixed and no spacers are needed)

There are two adjustments that can be made while installing the aileron hinge mounts to the aileron spar You can slide the aileron side-to-side and you can slide it up or down on the mounts. Start by clamping or bracing the aileron in the flight neutral position, with the trailing edge of the aileron aligned with the trailing edge of the tip rib. I simply clamped a paint stir stick to the tip rib and let the aileron rest on the stir stick:

The correct spacing between the aileron and the wing tip rib is approximately. 1/2":

Once you have the proper clearance between tip rib and aileron, you will need to adjust the aileron up or down to create a smooth blend with the wing. Again, make sure your aileron is braced up to be level with the tip rib and in the flight neutral position.

To adjust height, I used a 6' long metal ruler, laying it on the wing and allowing the end to hang over the aileron. Laying this ruler flat, it conforms to and matches the wing shape. Its easy to see if the aileron is too high or too low by looking at it's relationship to the metal ruler:

Check the aileron positioning at both ends to assure that you have a smooth flow from wing to aileron and that the aileron is a continuation of the wing shape.

Once you have the position correct on the bottom of the wing (remember, this wing is laying on the table, bottom side up), check it on the top side of the wing as well.  I used a shorter metal ruler for this:

Again - note how we have a smooth transition from wing to aileron.

Now stand back and look at the gap full length.  Make sure it is even and the aileron is not tilted one way or the other.  

Click here to go to Fitting the Flap and Aileron to Wing page 2