Ailerons and Flaps
by Frank Justice
Build both of the ailerons and both of the flaps at the same time
to save setup work; the instructions are written as if you are
doing one at a time to make things a little clearer. Both are
very easy to build as long as you do everything in the right sequence;
if not you will have a difficult time in some areas. Aileron Skeleton (Drawing #16)
- Determine the top and bottom side of the aileron spar (W-608)
and mark it for reference; the top side has the sharper bend.
Mark the spar as left or right, then mark the ends as inboard
and outboard. Drill the lightening holes if desired.
- Cut out the spar reinforcement plates and drill them #30 to the
spar for the three innermost rivets that connect only the plate
and spar. These are 1" apart and on a line 1/4" from the edge
of the plate.
- Straighten the flanges on the main and leading edge ribs; trim
the main rib long flanges to be straight and of equal width of
no more than 5/8". Round off the corners and bumps at the notches.
- Make a mousehole in the center of the inboard rib to give access
to the center bolt.
- Clamp the leading edge ribs in place on the spar. The flange edges
do not have to be aligned exactly with the skin edges; locate
them in just a little and avoid a difficult measurement or protruding
flanges. Drill the leading edge ribs to the spar and plates with
three #30 holes 1" apart. Drill the holes #30 for the counterweight
pipe in the tip ribs.
- Clamp the main ribs in place (flanges out, tooling holes closer
to bottom side, long flanges even with the end of the spar) and
drill #40 through the spar, plate, and rib for the two rivets
that will hold them together. These are centered on the spar and
rib flange, and 1 1/4" apart. Remove the rib and countersink these
holes on the reinforcing plate side. Put the main ribs back in
place and put rivets in the holes held with tape.
- On the aileron mounting brackets mark where the outside of the
lower skin will touch it; this is 13/16" from the bottom of the
bracket as calculated from the drawings. Drill the hole for the
aileron pushrod in the top end of the root end brackets. Do not
drill the hinge point holes at the bottom.
- Clamp the mounting brackets to the ends of the spar; the wider
bracket is on the inboard end. Insure that the wider bracket is
properly lined up with the web of the main rib so there will be
enough room for the bracket mounting bolts and nuts. Drill the
brackets to the spar and main ribs #40 to insure that they are
aligned, then enlarge to #12. Put short #10 screws and nuts in
these holes to secure the main ribs to the spar.
- Lay the skeleton upside down on a flat surface, tie or weight
down the main rib tips, and put the counterweight pipe in place.
Mark through the holes in the tip ribs onto the pipe. Remove the
pipe and drill it #30.
- Diassemble and debur.
Aileron Final Assembly
- Trim the skin as shown in the sketch in the construction manual;
the cutouts can be slightly narrower than what is shown.
- Mark the positions of the stiffeners and the spar on the inside
of the skins.
- Make the stiffeners (14 per aileron). The stiffeners for one aileron
will all look alike but the ones for the other aileron should
be mirror images of these to exactly match the plans; this is
not essential or observable in the finished product. Make a pattern
and mark the rivet holes on them. Tape the stiffeners to the skins
and drill them. Debur and dimple the skin and stiffeners.
- Prime the stiffeners, the inside of the skin, and the skeleton
parts. Rivet the stiffeners to the skins, bottom side first.
- Install the three rivets that hold the reinforcing plate to the
spar. Install the three rivets that hold the tip ribs to the spars;
verify that the tip ribs are perpendicular to the spar.
- With the spar assembly laying on a flat surface to avoid twist
rivet the counterweight pipe to the tip ribs with LP3-4 pop rivets.
- Complete the trailing edge bend so that the final radius of the
bend is between 3/32" and 1/8".
- Put the spar assembly in place in the skin and secure it with
clamps and tape; insure that the spar is held straight. Attach
the main ribs but not the hinge brackets to the spar temporarily
with #10 screws and ordinary nuts. Clamp everything together.
- Lay the assembly right-side up on a flat surface. Weight it down
to hold it flat. Drill the holes #41 that attach the skin to the
spar and the main ribs with 1 1/4" spacing.
- Pull the lower skin tight against the tip ribs and counterweight
pipe. Drill the skin #41 to the the tip ribs on the top side only.
- Drill the skin to counterweight rivet holes #30 just over 3 3/4"
apart. A Black? "Bulletnose" 1/8" drill bit works well for this
since it will drill without wandering; then enlarge the hole to
- Disassemble and debur. Dimple the spar, ribs, and skin; do not
do the ones where the rivets will go into the pipe since the curve
is too sharp; installation of the rivets later will cause the
skin to conform. Countersink the holes in the counterweight pipe.
- Remove one of the main ribs from the spar assembly and put it
back into the skin. Reattach the main rib to the spar.
- Turn the assembly upside down with the skin-to-spar clecos hanging
over the table edge and force it flat. Tape the bottoms skins
together so they are pulled tight against the spar assembly. Drill
the bottom side skin to main rib and skin to tip rib holes #41
and the skin to spar holes #30.
- Remove the spar assembly and debur and dimple all the skin, rib,
and spar holes.
- Put the spar assembly back into the skin and temporarily attach
the main ribs to the spar. Prop the bottom side skin up and rivet
the top side of the skin to the spar except at the ends where
the main rib will go.
- Place the leading edge part of the bottom skin on top of the trailing
edge part. Install the tip rib and counterweight rivets. Tap the
edges of the counterweight rivet heads with a small hammer to
make them conform to the skin curve.
- Remove the main rib on that end and bolt on the inboard mounting
bracket using the proper bolt, washer, and locknut only in the
- Put the main rib back in and rivet both to the spar and skin.
- With the assembly laying on a flat surface pop-rivet the bottom
skin edges to the spar.
- Attach the outboard hinge bracket and put in the other bolts for
the inboard hinge bracket.
Flaps are easier to build than the ailerons, but the construction
is somewhat different. Like the ailerons, alignment is maintained
and twist avoided by drilling and riveting with the assembly laying
on a flat surface. The information on rivet spacing on the plans
is a little deficient; some is hard to find and some will actually
not work. Bottom Skin/Rib/Spar Preparation
Control Arm Fabrication
- Lay one of the bottoms skins on a table with the flange away from
you just like it shows in SK-52. Mark this one "RIGHT", and mark
"ROOT" on the right end of it. Lay the other bottom skin on the
table behind it with the flange toward you (flanges together).
Mark this one "LEFT" and mark "ROOT" at the right end of it. The
two bottoms are mirror images of each other and you will be less
likely to get confused and wind up with two left flaps since you
will be making identical marks at the same ends.
- Mark the parts of the flanges to be cut off as shown in SK-52.
On one of the skins mark the positions of the rivet holes for
the spar. Mark the tip rib rivet holes but leave out the last
one toward the trailing edge (nearest the flange; see drawing
17 for spacing). Mark the root rib rivet holes, noting that the
spacing for the first five is 1" because the control arm is also
riveted there. Again, leave out the last one toward the trailing
edge. Mark the inner rib holes using the spacing on drawing 17
but modify as necessary to insure that they are far enough from
the ends of the rib flanges.
- Cut off the flanges as marked.
- Clamp the two bottom skins back to back and drill the marked holes
#41 through both. Separate the skins.
- Drill the short ribs FL-605 through the skins, making sure that
you have the right ribs in the right place; they are not symmetrical
as the tooling holes are closer to the bottom side. Mark the ribs
as to their position.
- Mark one of the spars "RIGHT" and the other "LEFT". Determine
which is the top and which is the bottom side (the sharper bend
is at the bottom) and mark accordingly. Trim off the small area
at the root end of each one as shown in drawing 17 (1/8" at top
down to nothing at bottom); hold them back to back with the tops
up and trim on the same end so you don't wind up with two left
- Clamp the spar in place (tip end even with tip edge of skin) and
drill it through the skin.
- Place the end ribs on the skin and drill them through the skin.
- Cut a piece of piano hinge 55 1/2" long and secure it to the spar.
Drill it through the skin and spar.
- Position the ribs perpendicular to the skin (except the root rib
follows the cut end of the spar). Drill the holes #30 for the
rivets that will attach the ribs to the spar and the flange of
the bottom skin. The spacing between the two holes for the spar-to-short
ribs will have to be approximately 1 7/8" rather than 2 1/4" so
they will not be too close to the end of the rib flanges. The
holes at the root rib must be 3/8" from the spar end so the control
arm assembly can be properly attached later.
- Remove the clecos holding the hinge to the skin and spar; reattach
the hinge oriented the same way except on the outside. Countersink
the holes in the hinge.
Top Skin Preparation
- Cut out the parts of the control arm assembly (FL-606A, B, and
C) per the drawing. Bend the FL-606B plate as shown. Dimensions
are not critical.
- Drill the FL-606B plate per the drawing #30.
- Clamp the FL-606A (large) angle to the spar with the corner of
the angle even with the trimmed end of the spar. Drill its mounting
holes #30 approximately as shown in the drawing except for the
ones where the root rib-to-spar holes already exist. Remove the
root rib from the assembly and drill the angle through these holes
in the spar.
- Reinstall the root rib, but use tape to hold it to the spar and
the bottom skin in the area where the contol arm assembly will
- Clamp the FL-606C (small) angle to the plate with its bottom edge
aligned with the bottom edge of the plate. Drill the angle through
- Clamp the plate/angle assembly (FL-606B and C) to the angle FL-606A
so that the lower surface of the small angle sits on the inside
surface of the bottom side flange of the root rib. If the tapered
edge of the small angle does not align with the web of the root
rib, take the assembly apart and rebend the FL-606B plate as necessary.
Drill the angle FL-606A through the plate.
- Drill #30 through the holes in the bottom skin into the small
- Remove the control arm assembly and debur its parts. Countersink
the holes in the surface of the small angle that sit against the
root rib flange.
Final Flap Assembly
- Draw a line 5/16" from the forward edge of the lower side of the
top skin for the line of rivets that will tie the top and bottom
- Lay the top skin bottom up on the table and place the bottom skin
in it. Position them so that the distance from the forward edge
of the bottom skin to the outside of the trailing edge of the
top skin is 11 1/4". Clamp together. (This dimension is not on
the drawing. It was obtained by placing the skins such that 10
1/2" is the distance from the trailing edge of the top skin to
the spar, measured along a line through the tooling holes at the
tip end. This done, the above distance was measured and found
to be as given. The skin edge to trailing edge distance is easier
- Mark the top to bottom skin attach rivet holes along the line
approximately 1 1/4" apart. Since it will be easier to buck these
rivets if they are not close to the ribs, begin by placing a mark
on either side of each inner rib. Then place the marks in between.
Drill these #41.
- Mark and drill #41 the remainder of the skin-to-end-rib holes
toward the trailing edge.
- Turn the assembly over and mark the top skin-to-spar holes. Weight
down the skin and drill them #41.
- Using the hole locations on the bottom side as a guide mark the
skin-to-rib holes. Drill these holes #41.
- Check that the flange of the spar conforms to the top skin contour.
If not, modify the flange bend.
- Disassemble everything, debur, and dimple all the #41 holes. Dimple
the #30 holes where the bottom skin and root rib attach to the
control arm small angle.
- Prime all the parts.
ailflaps.doc 9/23/94 Frank Justice
- Rivet the FL-605 inner ribs to the bottom skin.
- Put the top skin on and rivet the skins together.
- Rivet the top skin to the FL-605 inner ribs.
- Rivet the FL606A angle to the spar using only the five rivets
away from the spar end, then rivet on the root rib in the remaining
- Rivet the tip rib to the spar.
- Rivet the FL-606B plate to the FL-406C angle.
- Put the spar assembly into the skin assembly; rivet the spar to
the inner ribs.
- Rivet the top skin to the spar.
- With the assembly laying on a flat surface rivet the hinge and
bottom skin to the spar.
- Verify that the hinge pin will go in easily from the root end
of the flap. Trim the corner of the plate and angle if necessary.
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