Subassembly 4: The Right Elevator

by Frank Justice

Alignment Notes:

Items of particular interest in the right elevator assembly are: the Wd-405 control horn bend angle and bend line, the E-609 root rib flange bend line where it meets the E-602 spar, and the E-604 and E-405 tip rib flange bend angles and bend lines where they meet the spar. The height of the flanges on the long sides of the spar should be equal although they do not need to be exactly 5/8 inch. Taking care of these early reduces the twist in the spar in the final assembly, thus making it easier to line up the skin; it also insures that the two bearing rods are in alignment with each other thus making the elevator align properly with the horizontal stabilizer.

These preliminary operations are not all essential but if done will cause many hours to be saved later and also help to improve the appearance and aerodynamics of certain areas. It is easier to do these all at once rather than as the parts are called for in assembly. Since many of the elevator parts are the same for both sides, it is convenient to do these operations on parts for both at the same time.

Flute flanges to straighten. Bend all four flanges to be perpendicular to the web. Notch part of flange to clear flange on E-602 spar; hold it up to the spar to see how much to cut out. File down the flanges to an even height (approximately 5/8 inches). Verify that the flange on the trailing edge of the rib is perpendicular to the centerline of the rib; carefully rebend if necessary.

Flute flanges to straighten. Bend all flanges to be perpendicular to the web. No need to file flanges.

If bend line of flange that mates with spar is not perpendicular to the centerline of the rib, carefully modify the bend so that the flange is perpendicular. This is important in that it guarantees that the elevator will line up directly behind the horizontal stabilizer. Then bend ths flange down to an angle of approximately 68 degrees from the web. If the flanges on the long edge are not perpendicular to the web, bend them so they will be; then file them to be equal in height. Drill two #40 holes 1" apart in the flange for rivets that will later attach the rib to the spar.

If the bend line of the flange at the tip end is not perpendicular to the centerline of the spar, carefully modify the bend so the flange is perpendicular. This flange must also be perpendicular to the web of the spar. Insure that the long flanges are fairly even and of equal height. Radius the outside edge along both flanges slightly to keep stress from building up in the skin which starts its bend here for the leading edge.

Drill #30 holes as shown in drawing 5a. Do not drill the holes for the nutplates; drill a #30 hole at the center of the nutplate location; locate this hole as accurately as possible to the long-way centerline of the plates.

Verify that the bend angle is 68 degrees; if not, bend so that it is. Drill the 12 #30 holes as shown in drawing 5a except that the two holes next to the bend and the two holes in the center on the side with the tube should be placed 1/4 inch farther from the bend than shown in order to later clear the flange of the root rib and the trim tab rib (on the left elevator only). Do not drill the 1/4 inch hole in the horn. Locate the extended centerline of the tube on the control horn and mark. (Put a narrow straightedge inside the tube and align it with first one side and then the other; draw the tube centerline halfway between these two lines.)

None of the rivet hole locations in this assembly are critical. Clamp the two ribs together with the flanges carefully aligned. Drill all the joining rivet holes shown in drawing 4a except the ones for the counterweight baffles. Make the counterweight baffles for the tip ribs as shown in 4a, including the mounting holes. Clamp the baffles in position and drill their mounting holes into the rib assembly. Drill the two holes 7/32" for the counterweight hold-down bolts. Prime the surfaces of the ribs and the baffles where they mate and rivet this assembly together.

Hand-bend the counterweight skin so that it will conform to the tip rib assembly with only moderate hand pressure, then clamp it on with the edge of the skin aligned with the edge of the flange of the inside tip rib E-604. Drill #40 and countersink all the rivet holes that will not be later covered by the skin; see drawing 4a. There should be 28 holes. Remove counterweight skin from tip rib assembly.

1. (objective paragraph as in construction manual)
2. Lay out the position of the elevator skeleton and the stiffeners on both inside faces of the skin. Use sketch SK6-2. Also note the 1/8" overlap and alternation of flange position between sides for the stiffener placement shown on drawing 4a. Do not trim skin yet.
3. Fabricate the stiffeners from the 5/8"x5/8"x.025" angle provided. See dwg 4a to determine shape and distance from ends to spar and trailing edge.
4. Lay out the centerlines and rivet positions on the stiffeners. Position them on the skin; holding them down with duct tape is adequate. Drill them #40 to the E-401 skin as you did the rudder. Debur and dimple.

(read objective paragraph in construction manual)

1. Clamp the E-609 root rib, Wd-405 control horn, and tip rib assembly to the ends of the E-602 spar. Insure that the centerline of the control horn tube coincides with the centerline of the spar. Lay this assembly on one side of the skin against the marks for the spar and the longer tip rib; verify that the root rib winds up approximately in its proper place. (SK6-2 shows the root end of the spar going all the way to the end of the skin but it should actually be shown as ending even with the web on the root rib. At the tip end the rib shown is actually the back half only of the longer tip rib E-603; the inside short rib E-604 is not shown.) Then, hold this assembly up to the right side of the horizontal stabilizer (HS). Clamp the control horn to the center bearing of the HS with one AN960-416 washer in between. On the tip end there should be a space 1/8" to 1/4" between the elevator tip rib and the HS tip rib. If not, reposition the control horn on the spar (and trim that end of the spar if necessary).
2. Verify that the control horn tube still coincides with the centerline of the spar, and match drill the six control horn holes to the spar. Insure that the root rib is still in proper position against the spar and the control horn and mark through the two rib flange holes onto the spar. Remove the control horn and drill #40 holes at the marks on the spar. Countersink these holes on the side away from the rib. Put rivets into these holes held on with thin tape to keep the rib and spar aligned. Reassemble the control horn and root rib to the spar and match drill the six control horn holes into the rib.
3. Drill two #30 holes through the spar and the E-604 tip rib flange, then drill two #30 holes through the E-603 into the flange of the spar.
4. Position this assembly against the horizontal stabilizer as before and verify the 1/8" to 1/4" space between the tip rib and the HS tip rib. If not quite correct, another washer or two may be added or the elevator tip rib flanges may be shaved as applicable. Mark the position of each pair of HS hinge brackets accurately onto the elevator spar. Drill #30 holes on the centerline of the spar halfway between each pair of marks for the hinge brackets. Position the E-410 and E-411 on the spar with a cleco through the center hole and clamp firmly. Match drill the reinforcing plate holes into the spar. Enlarge the center hole to 3/8". Put a nutplate in place over the hole and secure it by inserting a rod end bearing with a nut on it from the other side. Drill the two nutplate mounting holes.
5. Disassemble everything, debur, and prime.

1. Rivet the reinforcing plates and nutplates to the spar.
2. Rivet the root rib to the spar.
3. Rivet the control horn to the spar and the root rib.
4. Rivet the tip rib assembly to the spar.

1. Backrivet the skin stiffeners to the skin.
2. Complete the trailing edge bend.
3. Recheck the skeleton rib positions against the skin markings; align the tip rib flange edge with the its mark 1/2" from the trim line for the edge of the skin. Verify that the inside edge of the tip rib is perpendicular to the spar and remark the tip trim line if necessary. Remark the trim line at the root end if necessary to keep it even with the edge of the flange. The old spar position markings on both the left and right sides of the skin should line up with the spar at the same time. If not it is because the trailing edge bend finish operation tended to favor one side. In this case remark the lines on the skin.
4. Mark the approximate position of the centers of the rod end bearings onto the outside of the skin. Using this as a reference point, mark the 2" bearing access cutouts centered on a point 1/4" toward the root from the rod-end bearing centers on the outside of the skin so the opening can be made after the leading edge is formed; cutting them out here makes it more difficult to form the leading edge bend and does not save any work. Mark the position of the inside edge of the short tip rib on the skin; mark the small triangular cutoff at the root end. Trim the skin at these cutouts and along the tip and root rib marks.

1. Set up the root and tip Elevator V-block jigs on a flat surface (the center V-block is not needed for the right elevator). Insure that the "V" of both blocks is exactly vertical to avoid twist in the finished elevator.
2. Place the skin and skeleton together in the V-blocks; clamp the skeleton firmly to the skin, insuring that the inside edge of the short tip rib is exactly perpendicular to the spar. Cleco the counterweight skin in place to the tip ribs. Note that the counterweight skin ends go under the main skin.
3. Determine the skin to skeleton rivet spacing and drill #40. Also drill two holes on both sides through only the skin and counterweight skin as shown in drawing 4a (where it shows CS4-4 rivets; with these directions you will use AN426AD3-3.5 rivets instead and impress your friends).
4. Mark a line on the counterweight skin that is an extension of the tip edge of the main skin.
5. Disassemble and debur. Countersink the new holes in the counterweight skin. Trim the counterweight skin on the line drawn in the previous step. Dimple all the skin and skeleton holes except the ones in the tip rib assembly where the counterweight skin sits. Touch up with primer applied thinly with a q-tip to avoid upsetting the countersink/dimple depth.
6. Rivet the counterweight skin to the main skin with only the four AN426AD3-3.5 rivets mentioned above.
7. Put the skeleton back into the skin in the V-blocks and rivet together. Be sure to check that the rivet size is correct for each section by actually measuring them.
8. Complete the leading edge bend of the E-601 skin. Dimensions are given in the Elevator Leading Edge Detail of drawing 5a. See procedure R-9 for the technique. Be careful to avoid having the skin bend sharply at the front edge of the spar flange. A heavy length of pipe 1/2" to 3/4" seems to do the best job, and duct tape holds the skin to it quite well. When marking for the rivets remember the 2" wide cutouts at the bearing access locations.
9. Make the initial bearing access cutouts in the leading edge; they should be 2" wide on the bottom side and up just enough on the top side to allow the rod end bearing to be put in; the rest of the top side should be just wide enough to clear the horizontal stabilizer brackets. The opening should go about halfway back from the leading edge to the flange of the spar. The openings shown in the plans are larger than they need to be and slightly increase drag.
10. Install the rod end bearings in the spar and install the completed elevator on the horizontal stabilizer with bolts through the HS-412 and HS-413 hinge brackets. Check the spacing from elevator to horizontal stabilizer as shown in drawing 5a. Then verify that the elevator will go up by about 30 degrees and down by 25 degrees before hitting the stabilizer skin. If necessary, turn the rod end bearings in or out to obtain the proper spacing, then lock the bearings down with the nuts. Secure the elevator with the counterbalance arm aligned with the horizontal stabilizer end. Drill the bearing bolt hole in the Wd405 control horn using the HS-411 bearing as a template.
11. Hold the pouring of the counterweight lead until the left elevator is done.

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