Chapter 2. Section 3- Ailerons

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1 Chapter 2 Section 3- Ailerons Material: Hangar 9 servo arms x ¼ button head screws - 16 Dubro ¼ scale hinges - 2 pckgs The ailerons are built using 3/32 x 4 x48 balsa sheet. Cut the sheets to match the plans. Use the 9 degree template to get the proper wingtip angle (shown to the left of each plan). The inboard angle is determined by measurements. You will need 4 identical sheets for the top wing and 4 for the bottom. Page 1

2 Hold the cut sheets up to the wings to check for proper alignment and size. Trim the wing and/or sheets as necessary to fit each other at the inboard end. Page 2

3 Matching aileron sheeting to the wing. Secure 8 - Hangar 9 servo arms to their respective servo horns. Use 2, 4-40 x ¼ screws per arm. Add thin CA to permanently bond the arms to the horn. Page 3

4 Servo arm mounted to aileron horn - 8 required Select two lower wing sheets to become the bottom aileron skins. Position each of these up to the wing and mark the exact location of the center of the servo box horn cutouts. These marks will be the locations of the servo horns, and must be exact. Pin these two skins on wax paper on your table. Lay them as a left and right - mirror images to each other. Page 4

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6 The horn cutout is seen on the right side of this box. Mark the skin in the center of this cutout. Draw a straight line on the top of the skins, 3/8 from the trailing edge. This is shown as the dotted line on the plans. Shape the 5/8 x 5/8 x 48 aileron leading edge spars to match the aileron ribs. It requires you to shape three of the four sides slightly with a sanding block. Page 6

7 Glue the two ¼ thick aileron ribs even with the ends of the aileron skins. The trailing edge of the ribs should just touch the line you drew. The ribs align with the edge of the skin. Page 7

8 ¼ balsa end rib. Note the line 3/8 from the trailing edge. Pin the leading edge spar in place, but do not glue. Ensure the front of the spar is perfectly straight for the length of the aileron. Locate and glue the remaining aileron ribs in place. Glue them to the skin, but NOT to the spar. All balsa ribs must be perpendicular to the spar, not slanted like the end ribs were. Space the ribs as follows: 1. One rib goes along the outside of each of the two box reliefs - on the side opposite where the horns will go. 2. The remaining 5 ribs for each aileron are spaced evenly between the reliefs. Remember to account for the horn ribs when spacing. Page 8

9 Balsa rib installed opposite where the horn will be installed. Note the filler fashioned to go between the rib and horn. The horn will be placed to the right of the relief. Page 9

10 Remaining balsa ribs and leading edge spars installed. Trim the leading edge spar to match the ends of the sheeting. Mark the leading edge spar even with the side of the reliefs at the side that has the balsa ribs. Mark the spar again at the horn marks you made earlier on the skin, but 1/32 farther from the relief than the original mark. This will account for the thickness of the horn. Remove the leading edge spar and cut at the marks you just made. Glue the three spar pieces back in place on each skin. Position the servo horns on the skins, centered on the marks you previously made and flush against the leading edge spar. Be sure the servo arm splined side is towards the relief. You will have to cut a notch Page 10

11 in the spar to accept the servo arm. The horns must be perfectly vertical and perpendicular to the skins. Notch spar to accept the servo horn. Page 11

12 Horn installation - note filler block position Slide a.047 piano wire through the eyes of both servo arms. Move the horns until the wire is even with the front of the spar and is exactly parallel to it. This step is to ensure the servo arms are exactly on the hinge line and is critical. When satisfied the horns are perfect, lock them in place with thin CA. If desired to save weight, carve out the back side of the leading edge spar. Unpin the ailerons from the table. Move them so the trailing edge of the skins are on the very edge of the table. Bevel the trailing edge of the skin to match the angle of the ribs with a large sanding block. Take your time and work carefully to keep from damaging the ribs. The bevel will go as far as the line on the skin that you drew. Page 12

13 Bevel trailing edge to match the rib angles. Using slow CA, glue the top skins to the ailerons. Weight them evenly along the whole span while the glue sets. Page 13

14 Weighting top skin while glue cures Mark and install Dubro removable hinges. Page 14

15 Cutting hinge slots using a dremel with a cutoff disc Page 15

16 Repeat the assembly steps for the top aileron. Page 16