Electric Elevator Trim

The electric elevator trim is a very popular option avalable from Van’s. If you want it, get the kit now as it is much easier to install while building the left elevator. Read the directions with it now so you will understand the differences. There are a couple of problems with it which will become apparent later. One is that the elevator skin is 0.016" thick but the access cover is 0.032"; if you install per the directions the cover will stick up by 0.016". If this bothers you (you could just bevel the skin edges) you can make a second doubler just like EET-601 but out of 0.016" material and cut out the inside the same size as the skin opening. Place this between the skin and the EET-601 to make the recess for the access cover be 0.032" deep. Also, some builders report that with the servo mounted as directed you cannot get full rear travel of it; the arm hits the access cover. The usual fix for this is to install spacers under the servo mount brackets to lift the servo up a little bit.

Alignment Notes:

The same alignments are important for the left elevator as for the right one.

Preliminary Parts Preparation

If you did not do the Preliminary Parts Preparation for parts on both elevators when you did the right side, go back to the Right Elevator section and follow the instructions for those and add the following:

E-605 left root rib: verify that the trailing edge flange bend line is perpendicular to the centerline of the rib; bend this flange farther so it makes an angle of 68 degrees with the rib body.

Making Stiffeners and Laying out the Skin

(read objective paragraph in construction manual)

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 yet.

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.

Lay out the centerlines and rivet positions on the stiffeners. Position them on the skin; hold down with tape. Drill them to the E-401 skin. Debur and dimple.

Building the Spar and Skeleton of the Right Elevator

(objective paragraph as in construction manual)

Alignment and Error Check:

Clamp the E-605 root rib, Wd-405 control horn, and tip rib assembly to the ends of the E-602 spar; clamp the E-606 rear spar to the end of the root rib. 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 main spar and longer tip rib; verify that the root rib and trailing edge spar wind up approximately in their proper places. (SK6-3 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 left 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).

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 aligned with the spar. Reassemble the control horn and root rib to the spar and match drill the six control horn holes into the rib.

Align the E-606 rear spar end with the trailing edge of the E-605 root rib and clamp; the E-606 and the main spar should be parallel to each other. Drill two #30 holes through the rear spar and the root rib flange. Mark an extension of the root rib flange edges onto the rear spar.

Lay a straightedge between the main and rear spars and bend either if necessary to make the flanges follow the skin line; the spars must be exactly parallel for this,which requires a shim under the outboard end of the rear spar, and the rear spar must be constantly checked to make sure it does not develop a twist. Remove the rear spar and trim the inboard end as marked previously.

Drill two #30 holes through the spar and the tip rib flange, then drill two #30 holes through the E-603 into the flange of the spar.

Position this assembly against the HS 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 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.

Cut out the trim tab skin from the elevator skin and set it aside.

Disassemble everything, debur, and prime.

Assembling the Skeleton

Rivet the reinforcing plates and nutplates to the spar.

Rivet the root rib to the spar.

Rivet the control horn to the spar and the root rib.

Rivet the tip rib assembly to the spar.

Finishing the Skin

Backrivet the skin stiffeners to the skin.

Finish trimming the skin tabs that close the elevator at the trim tab cutout to proper shape. Leave a 1/8" radius at the end of a slot for the leading edge end, and a 1/4" cutout along the bend line at the trailing edge end.

The tabs are bent as follows: Make a 1/4" radius cutout in the ends of the tabs at the trailing edge to prevent stresses caused by the tab bending; bend the top tab first, then bend the bottom tab so it fits inside the top tab (this keeps water from entering the elevator). A nice bend can be made by clamping a block of wood to the skin and bending the tab over it; see figure 6.19; this would be done after the next step, Complete the trailing edge bend.

Complete the trailing edge bend.

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.

Mark the approximate position of the center of the rod end bearing holes onto the outside of the skin; then mark the shape of the 2" wide cutout centered about a point that is 1/4" toward the root from the rod-end brearing holes centers (easier to insert and remove hinge bolts). Mark the position of the inside edge of the short tip rib on the skin and mark this cutout.

Hold the spar in postion on the horizontal stabilizer and mark and then drill the 9/16" trim cable hole in the spar 1" from the bottom and directly behind the 7/16" hole in the stabilizer rear spar. Mark the center of the trim tab cable hole onto the outside of the skin. Using this as a centering point, mark the 5/8" wide cutout onto the skin.

Trim the skin at the tip and root ribs but do not make the leading edge cutouts.

Final Assembly

Set up the root, center, and tip Elevator V-block jigs on a flat surface. Insure that the "V" of all three blocks is exactly vertical to avoid twist in the finished elevator.

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.

Determine the skin to skeleton rivet spacing and drill #40. Also drill two holes on top and bottom 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).

Mark a line on the counterweight skin that is an extension of the tip edge of the main skin.

Disassemble and debur. Countersink (or dimple) the new holes in the counterweight skin.

Dimple all the skin and skeleton holes except the ones on the tip rib assembly where the counterweight skin sits (do these also if you dimpled the counterweight skin) and the ones in the top side of the rear spar where the hinge for the trim tab will attach. Countersink the rear spar holes instead. Touch up with primer.

Trim the counterweight skin on the line drawn in the previous step.

E-608 Trim Cable Area Rib

Cleco the bottom edge skin to the skeleton. Put the E-608 trim cable area rib in place against the skin, adjust the flange bends as necessary, and clamp to the skeleton. Drill two #40 holes to attach the E-608 to the root rib and one #40 hole to attach the E-608 rib flange to the spar and control horn. Drill the #40 E-608 to skin attachment holes. Disassemble, debur, and dimple the skin to E-608 holes.

Backrivet the E608 rib to the skin.

Skin to Skeleton Attachment

Rivet the counterweight skin to the main skin with only the four AN426AD3-3.5 rivets mentioned above. Joggle the spar so the skin will not have a bump where the counterweight skin joins it.

Put the skeleton back into the skin in the V-blocks and rivet only the bottom skin.

Enlarge the E-608 rib to skeleton holes to #30 carefully (use strong clamping) to avoid distorting the skin. Rivet the rib to the skeleton.

Rivet the top side of the skin to the skeleton except along the area where the trim tab attaches; this will be done later together with the trim tab hinge.

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. Make sure that the side of the skin which goes outside is overbent slightly right at its edge so there will be no gap when the rivets are put in place.

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.

Make the 5/8" wide trim cable cutout in the leading edge extending only about halfway from the center toward the spar flanges.

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 Wd-405 control horn using the HS-411 bearing as a template.

Alignment Notes:

None of the alignments of the trim tab are particularly critical or difficult to achieve; however, keep in mind that the closer the trim tab conforms to the extension of the shape of the elevator the better performance will be.

Fabricating the Skin

Bend a piece of posterboard (thin cardboard) in the middle, using the trailing edge of the elevator to shape the bend. Cut it to a size about two inches larger than the trim tab.

Mark it to the exact shape of the trim tab opening in the elevator as follows:

Mark lines on the elevator that are extensions of the trim tab opening, far enough so that they will be visible past the edges of the cardboard.

Position the cardboard over the opening. Lay a long sraightedge along the trailing edge to align the rear edge of the cardboard with the elevator edge and tape the cardboard to the elevator.

Mark the exact shape of the trim tab opening on the cardboard using the marks on the elevator as a guide.

Subtract 3/16" from the leading edges and from the outboard edge (the hinge allowance and the gap to the elevator edge) and mark these lines to cut.

Cut out the trim tab pattern and tape it in place on the elevator to verify its shape. Cut out two triangles of posterboard that are the same size as the opening at the large end of the trim tab. Remove the pattern and cut out two more triangles that are the same size as the end of the elevator that corresponds to the small end of the trim tab. Tape these triangles to the pattern in the proper positions. Cut off the large end of the triangles so they are 1/2" short of the leading edge of the trim tab pattern.

Lay this pattern onto the outside of the trim tab skin and mark it onto the skin. Cut out the skin, leaving a 1/8" radius on the inside corners.

Using the pattern less the triangles mark the bend lines at the ends of the trim tab. Cut out a radius from the triangles along the bend line for about 3/16" and round the corners.

Bend the top end tabs down 90 degrees with a hand seamer. Bend the bottom edge tabs up in such a way that they will fit inside the top edge tabs when the trim tab is closed. (The top is bent first because it is more difficult to make a perfect tab when the other one is in the way. The top tab is the one that has to look nice.)

Complete the trailing edge bend.

If the above method of making the end bends does not work for you, lay the trim tab on the bench (with the trailing edge bend alreay done), insert one of the wedges from the elevator V-blocks in it even with where the end bend is to start, lay another wedge on top, and put a clamp on the whole thing. You can then beat the end tabs down with a mallet.

Attaching the Spar and Hinge

Clamp the trim tab spar to the inside of the upper side of the skin with the flange edge even with the skin edge. Verify that the lower flange of the spar is flush with the lower skin; if not, bend the lower flange as necessary.

Drill with #40 the lower skin to the spar.

Make the trim tab control horn using drawing 5a.

Note: Some RV’s have developed a crack in the skin adjacent to the control horn. To prevent this, make a doubler out of a piece of the 0.032 skin left over from the horizontal stabilizer. This doubler goes underneath the control arm and turns the corner to continue along the spar for about two inches. Drill and pop rivet this to the spar, then continue on. This fix is not presently shown in the plans, but was described in the June ‘95 RV-Ator.

Drill with #30 the holes that hold the end tabs closed and the control horn on. See drawing 5a.

Clamp the hinge in place under the upper flange of the spar and drill the upper skin to the spar and hinge with #40.

Disassemble. Countersink the holes in the spar. Deburr. Dimple the skin.

Prime all parts.

Rivet the lower skin to the spar.

Cleco the upper skin to the spar and hinge. Clamp the other side of the hinge to the elevator. Verify that the trailing edges of the trim tab and elevator form a straight line. Remove from the elevator and rivet the upper skin to the spar and hinge.

Rivet the ends and control horn.

Bend up the leading edge of the lower skin just enough so that when the trim tab pivots down the skin clears the lower edge of the elevator.

Clamp and/or tape the hinge to the underside of the elevator rear spar flange. Verify that the trailing edge of the trim tab and the elevator form a straight line.

Drill through the elevator holes into the hinge.

Remove the elevator by pulling out the hinge pin; deburr the holes.

Rivet the trim tab hinge to the elevator.

Trim the end of the hinge even with the trim tab and elevator edges. Cut the hinge pin about 3/4" longer than the hinge and round the ends slightly.

Put the hinge pin back into the hinge. If it does not go in easily, realign any parts of the hinge that may have been distorted by the riveting operation.

Bend one end of the pin over 90 degrees so as to leave a "foot" about 1/2" long. Captivate the hinge pin by drilling a hole in the elevator for running safety wire through it and around the "foot".

Make the opening in the elevator bottom skin for the trim cable as shown in drawing #5a. It should be centered on a line through the trim tab control arm and the trim cable hole in the elevator spar. The Wd-415 nut/plate and the trim cable shown there is not in the empenage kit; it comes with the fuselage if you get the manual trim option.

lfelevtr.doc 3/13/96