Chapter 19

Chapter 19: WINGS & AILERON ATTACH

These are the wing jigs that are required to hold the wings in place as you bond them together, glass them and prepare them for controls. The process involves cutting plywood per plans and cutting out templates to form a shell for the foam wings to rest in. (NOTE: The garage floor was so CLEAN back then!)

Take a look at the wing jigs being supported by 1/4 inch 'sticks' of plywood. This is per the plans, and totally inadequate. I ended up using small blocks that I 5 min epoxy'd to the jigs and the floor. Now they are tight and straight.

Here is a picture of the wing attach points from the plans, and the templates drawn on the wing. Look carefully, at the bottom of the picture, you can see where I drew the template in the wrong spot initially. Mistakes, I find, are often made, but easy to catch, and easier to repair (so far, anyway)... Note also the cracked and broken pieces of foam. One of the beauties of composite construction is that these cracks and any other small pits and dents can be filled in, without detriment to the form of the structure.

Pictures of the spar cap on the shear web portion of the wing. As far as I know, the spar cap gives strength to the wing without too much rigidity. These layups were done in a temp range from 70 deg. to 100 deg. At 100 deg. the epoxy begins to cure immediately (and I begin to get delirious), so I had to work quickly. Next, the leading edge portion of the wing will be micro’d on top. I have placed the uni strips over the wing attach points in the right-hand pic. Note the crooked line on the bottom surface of the wing: I cut with a band saw because, in a complete rookie maneuver, I left an inner piece of foam INSIDE the wing after I bonded the wing pieces together. All efforts at removing the piece easily failed, so I sucked it up, cut through, and re-micro’d. My first experience with total frustration with this project.

29 September 2000 Update: I could have left the piece of foam inside the wing until I cut the ailerons, at which point it would have fallen out. The learning curve is quite steep sometimes.

Finally! The leading edge of the wing is micro’d to the rest of the wing. It’s always a cliffhanger when I bondo two large blocks of foam together. Its imperative to make sure the fit and positioning are correct. The bags hanging off the leading edge are full of sand; weights to keep the wing in place. In the right hand picture, the small stick attached to the outboard edge of the wing keeps the leading edge from sliding off the rest of the wing while it cures.

The wing is on the new jig table. I knew my old table wasnt going to be long enough. This table is simply 11 x 4 of 1/4” plywood on saw horses. The garage is getting CRAMPED.

Here I have layed up the 3” Uni tape on the lower wing spar cap. I did not peel ply the sides of the spar cap before bonding the leading edge of the wing to the trailing edge, so I did a LOT of sanding to correct my mistake. I needed to sand so that the tape is flush with the wing after cure. The top wing spar cap is virtually the same, with the exception that I weighted the tape down after the layup to make it flush with the wing.

The rudder conduit is installed. The conduit simply allows the rudder cable to run through the wing. I used a block of wood, with a hole cut through the center, and the dremel tool sanding bit sat in the hole of the block of wood, making it easy to slide along a line I traced in the wing. The block kept the conduit at a uniform depth. The conduit itself is nylaflow tubing. The conduit is covered with dry micro just before skinning, as seen here. It is the line running parallel to the leading edge, from the inboard to the outboard.

The wing has been skinned with UNI fiberglass. Two layers, top and bottom, with an additional layer on the top. I think it took me a good six hours total to do the work. Im not looking forward to doing it again for the left wing. The picture on the left shows three UNI layers of fiberglass layed-up over the inboard attach point. You can never have too much fiberglass holding the pieces that hold the wings together! The second picture shows the glassed wing root 'rib' of three layers of BID. The hole you see at the lower right of the leading edge is for wiring.

Unfortunately, this isnt a very good picture. What you see here is the inside of the inboard portion of the wing, glassed with three layers of BID.

The aileron is cut out. A scary proposition after building a wing. The aileron is a little bit longer and wider than what is called for in the plans. It's six inches longer, 1/2 inch wider on top, and 5/8 wider on the bottom. This mod was incorporated in the Berkut , for a more responsive roll rate.

OOPS! Well, making the ailerons wider was not a good idea. Since the ailerons are cut from the wing itself (and not made seperately), the 1/2 inch extension added to the aileron took 1/2 inch away from the wing where the hinges are to mount. To correct my mistake, I ended up cutting the 1/2 inch off the aileron, bonding it to the wing, and glassing it in place with three layers of BID. Upon later reflection, I could have left it the way it was, and cut further into the wing, but I think this will work.

Lesson learned: Stick with the plans, they make the airplane build and fly the way its supposed to.

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