Notes on building a jig for the empenage:

If you plan to build your wings on the same jig, for an RV-6 the distance between the inside surfaces of the posts should be at least 108". For the RV-4 it should be at least 117". See the wingjig section for a few details on setting up the posts.

The empenage can be built on a free-standing jig with leveling feet if you are an apartment dweller. Make the feet on the supports at least 36" long.

Building the Horizontal Stabilizer Rear Spar

Written by:

David Barnhart

RV-6 SN 23744

barnhart@crl.com

With a few added notes by FKJ.

Parts Preparation

HS-606 Tip Ribs: Bend all flanges perpendicular to the web. Flute the ribs to straighten them.

HS-607 and HS-404 ribs: Bend the long flanges (not the aft-facing flange) perpedicular to the web. Flute ribs to straighten.

HS-608 and HS-405 ribs: Bend the long flanges and the aft-facing flange perpendicular to the web. Flute ribs to straighten.

Debeurr all edges. Round any sharp corners on the ends of the flanges.

HS-409: Use Scotchbrite or fine Emerycloth to remove any tooling marks from the HS-409’s. polish the edges so they are slightly rounded. File, sand, or polish the ends to remove the sharp corners. Be careful not to remove too much material from the end corners. ideally, the ends should each form a 1/2-inch diameter semi-circle.

Preparing the Jig:

This assumes that you have built a suitable jig as described in Van’s Construction Manual. In this step, you will draw lines on the surface of the jig’s horizontal crosspiece member. These lines are used later to accurately position and align assemblies. Drawing thin, straight, accurate lines will be made easier if you fasten a four-inch-wide strip of melamine to the top surface of the jig’s crosspiece. Melamine is typically Partical Board coated with a thin veneer of a white plastic-like substance.

Begin by drawing a straight line down the center of the Jig’s horizontal crosspiece. An easy way to draw this line is to use a carpetner’s chalk snapline, then overlay the chalk with a line drawn with a Sharpie pen.

At the center of the crosspiece, and exactly perpendicular to the spanwise centerline you just drew, draw a second line. This will be the ‘vertical’ centerline of the spar. The two HS-603 spar channels will join at this vertical centerline.

Draw four more lines on the jig exactly perpendicular to the spanwise centerline:

19-15/16 inches left of the vertical centerline

19-15/16 inches right of the vertical centerline

42-11/16 inches left of the vertical centerline

42-11/16 inches right of the vertical centerline

These four lines will be used later to locate the HS-412 and HS-413 hinge brackets.

Preparing the HS-603 Spar Channels and Fastening Them to the Jig

Locate and draw a line down the spanwise centerline of each HS-603, as shown in Van’s Construction Manual. The line should be on the same side of the HS-603 as the flanges. An easy way to locate the spanwise centerline is to use a center-finding rule.

File a small (1/8 inch) notch in the inboard end of each HS-603 at the centerline. Lay the HS-603 spar channels on the jig, flange side up. Butt the inboard ends together, aligning the centerlines of the HS-603’s with the spanwise centerline on the jig. The inboard ends of the HS-603’s should meet at the vertical centerline drawn on the jig.

NOTE: It is not important that the inboard ends butt perfectly. In fact if the inboard end of the HS-603 is not cut exactly perpendicular to its centerline, the two HS-603’s will not mate perfectly. This does not matter. What does matter is that the spanwise centerlines of the HS-603’s be exactly aligned over the spanwise centerline drawn on the jig crosspiece. Also insure that the overall length is as shown in the plans.

Drill a #40 hole in each HS-603 on its centerline approximately 3 inches in from the outboard end. Cleco the HS-603’s to the jig using this hole.

Prepare the HS-409 Flange Strips

Locate and draw the vertical centerline on each HS-409. Following the instructions in Van’s Construction Manual, mark and pilot-drill the rivet holes in the HS-409’s. Use a #40 drill bit, and be sure not to drill the holes shown on the plans for the fuselage attachment, HS-411’s, HS-412’s, HS-413’s hinge brackets, etc. Find the way the flange strips fit the best against the spar channels; the taper may be slightly different on the sides of the strips. Round off one edge of each HS-409 so it lays flush against the flanges of the HS-603’s (a belt sander with a coarse belt works well for this). Lay the HS-409’s in the spar, aligning the vertical centerlines of the HS-409’s with the inboard ends of the HS-603’s and vertical centerline drawn on the jig. Using a #30 drill bit, and the pilot holes as a guide, drill through the HS-409’s and HS-603’s. Insert a cleco in each hole, fastening the assembly to the jig.

Do not prime or rivet these parts yet.

Prepare the Hinge Brackets

Follow the instructions in Van’s Construction Manual to prepare the HS-411, 412, and 413 hinge brackets. This includes priming the HS-411’s, mounting the VA-146 bearing between the two HS-411’s and riveting these three parts together. Do not drill the mounting holes in the brackets. When drawing the centerlines on these hinge brackets as described in Van’s Construction Manual, be sure to do so with a high degree of accuracy. A carpenter’s square is very helpful for this process.

Aligning the HS-413 Hinge Brackets

Locate, drill #30, and cleco the inner HS-413 hinge brackets to the spar as described in Van’s Construction Manual. These brackets need to be clamped very securely to the spar or they will shift during drilling; drill right into the jig beam and install a cleco in every hole as you go. Use an adjustable carpenter’s square and the perpendicular lines previously drawn on the jig to help you arrive at spanwise alignment. Use the centerlines drawn on the HS-413’s and the spanwise centerline on the spar to help you arrive at the ‘vertical’ alignment.

Aligning the HS-411 Assembly and Inner HS-412, 413 Hinge Brackets

Using the technique shown in Van’s Construction Manual, locate and align the HS-411 assembly and the inner HS-412 and 413 brackets on the spar. The perpendicular lines drawn on the jig earlier will help you do this. An alternative to using the drilled bolt (described in Van’s Construction Manual), is the "Hinge Line Alignment Bushing" set, available as order number 10745 from Avery.

When everything is accurately aligned and clamped to the jig, drill #30 and cleco the parts. Drill out the mounting holes for the center hinge bracket HS-411 only to 3/16" (it mounts with bolts).

Mounting Remaining HS-412 and HS-413 Brackets

Use the technique described in Van’s Construction Manual using a rod-end and washer to locate and align the remaining HS-412 and HS-413 hinge brackets. Clamp the parts to the jig. Drill and cleco the parts to the jig.

Priming and Riveting

NOW (yes finally), remove all clecos. Alumiprep (and optionally alodine), and prime all parts (except the HS-411 assembly which was primed earlier). Rivet everything together.

By far the best way to rivet the parts together is by using the ‘Avery Tool’ instead of trying to squeeze the 1/8" rivets with a hand squeezer or using a rivet gun.

Drill the trim cable hole in the HS-603, making sure you do not cut into a flange strip. The spar is laterally symmetrical up to this point; whichever side you drill the hole in becomes the left side. Enlarge this hole sideways about 1/8" and right down to the flange strips. Bevel and smooth the edges of it on both sides.

Drive a nail into the melamine at each end of the jig crosspiece. The nails should be driven through the spanwise centerline drawn on the surface of the melamine. Connect a taught string between the two nails. You now have two spanwise centerlines perfectly aligned with each other: one drawn, the other in string.

Prepare the HS-602 front spar channels according to Van’s Construction Manual by marking their spanwise centerlines and creating the ‘tongue’ on the inboard ends. For now just cut off the flanges; no more than just enough material to make the tongues completely flat. Mount the HS-602 spar channels flange side down on the jig crosspiece, aligning the centerlines drawn on them with the centerlines on the jig.

Fabricating the HS-610 and HS-614

The bottom view drawing labeled SECTION A-A’ is a little confusing in this area if you aren’t used to reading mechanical drawings. Look at the FRONT VIEW right above it and find the solid-double-dashed series of lines which have an arrow point and an A at one end and an arrow point and an A’ at the other. This tells you where you are standing on that view to see what you do on the drawing SECTION A-A’ drawing. Imagine yourself standing on the line and looking in the direction of the arrows. In this case on the left side of the drawings you are standing below the stabilizer looking up and seeing the bottom of the lower angle. On the right side of the drawing you are actually inside the spar but still looking up; you are seeing the bottom side of the top angle.

Fabricate the HS-610 and HS-614, but do not put the bends in yet. Note carefully which way you make your saw cut to remove the flanges from the angles at the ends; the tapered tongue starts out being the full width of the angle. Locate and drill the holes with a #40 drill bit. Note that four holes marked "Drill in assembly with fuselage" should not be drilled. Position the HS-610 and HS-614 on the spar channels, making sure you have them placed exactly as shown in the plans. Clamp them in place. Using a #30 drill and the #40 pilot holes as a guide, drill out the rivet holes inboard of where the bends will be; eight holes in the HS-610 and eight in the 614.

Remove the HS-610 and 614 from the jig and put the 6 degree bend in them.

Assembling the Front Spar

Support the HS-610 and 614 on a block several inches high, and cleco them to the HS-602 spar channels. Be sure to add a couple of extra clamps on each side of the bend in the HS-610 and 614 so that the spar channels will lay flush in the bend. Using a #30 drill bit and the #40 pilot holes as a guide, drill out the holes in the HS-610 and HS-614 outboard of the bends.

Drill the 5/8" diameter trim cable hole in the HS-602. Make sure you have revision 3 of the #3a drawing which shows this hole on the correct side (to the right of the centerline when the HS-614 larger angle is toward you and the flange of it is toward you).

The inboard four rivets on the HS610 and the inboard two rivets on the HS614 will be AN426 (flush) rivets with the flush head facing aft. Dimple these four holes in the HS602’s. Machine countersink the corresponding holes in the HS-610 and 614. If you have a 120-degree countersink bit, you’ll find the back side of the dimple (in the HS602) will fit better than if you countersink with a normal 100-degree countersink bit.

Prep and prime the HS602’s and HS-610 and 614. Rivet them together.

Jig Modifications

Mount a centerpost on your jig according to the instructions in Van’s Construction Manual. The surface of the centerpost facing the skeleton should be perfectly plumb (vertical).

Fabricate a pair of brackets shown in Figure 6.9 in Van’s Construction Manual, and mount them on the jig uprights in their approximate positions. Fabricate five brackets (also shown in Figure 6.9) and mount them on the jig crosspiece. These five brackets should be positioned so that when the rear spar is mounted on the jig, each bracket will fit between its associated HS411, 412, or 413 hingle bracket pair. It is EXTREMELY IMPORTANT that these five brackets are aligned perfectly. Run a string through their holes, making sure that the string passes through the exact center of the hole in each bracket. Make sure that the centerline of each bracket is aligned with the spanwise centerline drawn on the jig. An alternative to fabricating these five brackets is to ppurchase them ready-made for about $20 from Avery.

Assembling the Horizontal Stabilizer Skeleton

Mount the rear spar to the five brackets on the Jig’s crosspiece. Locate, drill, and cleco the HS-606, 608, and 405 ribs according to the plans and Van’s Construction Manual. Enlarge the forward tooling holes in the HS-606 ribs to accomodate the threaded rod on the brackets you mounted on the jig uprights in the previous step.

Place the front spar on the rear spar/rib assembly. Note that the plans show several dimensions you should use to get the distance between the front and rear spars correct at the tip and root, and to get the angle of the HS-405 ribs correct. Also note in section A-A’ that you have to notch the HS-604 ribs to clear the HS-614.

Make sure that the distance from the centerpost to the spanwise centerline of the rear spar is the same as it is to the front spar. Drill and cleco the front spar to the HS-606, 608, and 405 ribs. Locate drill, and cleco the HS-404 and 607 ribs.

Remove the clecos, drill and prime everything, then rivet the skeleton together, except for the HS-404 ribs. Do not rivet the HS-404 and HS-405 ribs to the front spar at this time. The HS-404 will later be removed to make it easier to rivet the skin on.

Skinning the Horizontal Stabilizer

Make three simple wood clamps as shown in Van’s Construction Manual. Duct tape may work beter than foam weather strip to line the cutout.

Place the left skin on the left side of the skeleton. Clamp the skin to the skeleton. Shift the skin laterally until the proper overhang at the trailing edge is achieved.

Clamp the skin to the skeleton very tightly using the wooden clamps and several C-clamps. Remove the clamps from one side only. Peel the skin up on that side and using a Sharpie felt pen, trace the pattern of the ribs and spars on the backside of the still-clamped-down side of the skin. Mark the location of each flute. Mark the locations of the HS-411, 412, and 413 hinge brackets. Reclamp the skin back down, remove the clamps from the other side, and repeat the procedure.

Remove the clamps, and remove the skin from the skeleton. Lay the skin on the bench. Mark rivet lines on the backside of the skin. The rivet lines should be 1/4 inch from the edge of the flange of each rib/spar.

Mark the rivet spacing, being mindful of the positions of the flutes and hinge brackets. Do not locate a rivet over a flute, or directly in line with a hinge bracket.

Now draw a line down the flange of each rib/spar 1/4 inch from the edge of the flange.

Using a #41 drill, backdrill the rivet holes through the skin from the back side.

Place the skin back on the skeleton. When you have the skin correctly aligned, you should be able to see the rivet line drawn on the rib/spar flanges through the rivet holes in the skin. Clamp the skin in place. Using a #40 drill and the #41 pilot holes as guides, drill through the skin into the ribs and spars. Put a cleco in each hole as you drill it.

Mark the outline of the notch you made in the HS-604 ribs onto the skin. Remove the skin from the skeleton. Deburr the holes. (Scotchbrite should be sufficient to deburr the holes in the skin.) Cut out the area you marked that corresponds to the notch in the HS-604. Use the Avery Tool to dimple all the holes in the skin. Use a hand squeezer to dimple the holes in the skeleton. Prime the backside of the skin.

Place the skin back on the skeleton for the last time, clecoing it down. Remove the clecos from one side, and rivet the skin to the skeleton on the clecoed side.

Now for the other side. Starting at the tip, rivet the skin to the front spar. Two holes on each side of the hole you are working on should contain clecos. The remaining rivet holes should not be clamped dow, so that you can peel the skin back to get your arm in there and buck the rivets.

Rivet your way inboard untill you are about 2/3 the way to the HS-608/607 rib. Then alternate between riveting the skin to the front spar and riveting it to the aft end of the tip rib. When riveting the skin to the tip rib, start at the junction with the front spar, and work aft (down).

After you have finished all the rivets between the tip and the HS-608/607 rib, finish the rivets in the tip rib forward of the front spar. You may find it difficult to get a rivet squeezer in position to squeeze the last one or two rivets at the leading edge. There are a couple of techiques you can use. You can grind the jaws of a pair of Vise-Grips smooth and use it a a rivet squeezer. If you have a pneumatic rivet squeezer or Avery’s new hand squeezer, you can gat a ‘no-hole’yoke for it.

Go back to riveting the skin to the front spar. When you get about 1/3 the way to the root rib, alternate between installing a rivet in the front spar and the HS-405 rib. When riveting the skin to the HS-405, start at the junction with the front spar, and work aft (down).

After riveting the skin to the entire front spar, rivet the skin to the HS-607 rib. This is why you left out the HS-404 rib: so you could get in there with your hand to buck the rivets on the HS-607 rib.

Rivet the HS-404 rib to the front spar. Using a hand squeezer, rivet the skin to the root rib and rear spar.

Now that you’ve done the left skin, repeat this process for the right skin.

horzstab.doc

9/13/95