ZODIAC CH 601 Series
Rudder Assembly Manual

This rudder assembly manual has been organized to help the first-time builder assemble the rudder tail kit.  The rudder kit requires an estimated 12 hours to assemble, and provides the builder with an excellent introduction to building the complete kit, covering most of the skills and techniques needed to assemble the rest of the aircraft kit (the rudder is basically a diminutive version of the wing).

INTRODUCTION

Building your own aircraft is probably going to be one of the most challenging and rewarding things you will do in your lifetime: imagine, you'll be flying in an aircraft that you have built yourself! Few people get the sensation and freedom of flying. Even fewer also get the reward of flying a plane that they've built themselves!

The most difficult part of the project will be getting started: Don't become overwhelmed. While it's true that an aircraft is a piece of complex machinery, it is also very simple, especially when building from a kit. It's normal that you may initially become overwhelmed and confused, but your initial fears and concerns will disappear as soon as the project starts coming together, and as you get a better understanding of the construction. The ZODIAC CH 601 is a well designed light aircraft - engineered specifically as a first-time kit project, using proven materials and simple processes and systems.

This RUDDER ASSEMBLY MANUAL has been prepared as a supplement to the complete and detailed Drawings and Manuals for the ZODIAC CH 601 series aircraft.

The ZODIAC CH 601 rudder assembly is the same for all ZODIAC CH 601 models.  The assembly process is very similar for the STOL CH 701 rudder.

Read first:
Required Tools
Using Your Tools
Before Starting

Blueprints:
6-T-0
6-T-4 (1)
6-T-4 (2)
6-T-4 (3)
6-T-5 (1)
6-T-5 (2)
6-T-5 (3)

Assembly Drawings:
T2
T4
T6
T8
T10
T12

GETTING STARTED

READING THE ASSEMBLY INSTRUCTIONS: The detailed Assembly Instructions have been prepared so that the complete airframe may be built from the parts supplied in the kit. The drawings are not to scale, and provided measurements are metric (millimeters). All the required references are provided in the Assembly Instructions, but often only once (this may require some cross-referencing). For rivet holes, do not count the "X"s shown on the drawing: Either the pitch (distance between holes) is specified, or the number of holes (rivets) is specified. Updates to the Assembly Instructions are published on the Zenith website (builder resources area).

WORKING TOLERANCES: When assembling the kit, the pre-formed parts fit together properly, but certain tolerances must be observed. Always follow the specified dimensions as closely as possible, but remember to be practical and use common sense (you're building a well-designed light aircraft, not a jet fighter). Follow these tolerances:

Contact Zenith Aircraft Company if tolerances exceed those specified above.

Edge Distance (e) = 3 X Rivet Diameter (d)

EDGE DISTANCE: When positioning rivets, you must provide proper "Edge Distance" (the distance from the rivet or rivet hole to the edge of the material) for structural strength: The edge distance should be about three times the rivet hole diameter, usually approx. 10 mm. (with two times the diameter the minimum acceptable edge distance):

Working with sheet metal: Handle sheet metal parts with care. Sheet metal skins can easily be damaged (bent or kinked) when handled. With larger skins, it is recommended that two people handle them (one on each end).

Be careful with sharp corners and sheet-metal edges. Be especially careful with children around sheet-metal corners at eye level (workbench height).

Always wear proper protection when working with power tools and around sharp sheet-metal parts.

Avoid scratching the material, but do not worry about light surface scratches. On spars and longerons, transverse scratches and nicks must be removed by filing and sanding lengthwise to remove scratches.

Don't throw away cut-offs - you may find a use for such parts at a later date, or you can use them as "practice" pieces.

DRAWING AND MARKING: Before drilling or positioning parts together, draw the position on the part(s) and hole marks. Use a felt-tip marker to draw or soft pencil. Use a straight edge to mark straight lines. To draw lines along a rib flange, it's often easier to simply use your hand (finger) as a reference, or you can use a simple "marking" tool.

CORROSION PROTECTION: The aircraft has been designed to minimize exposure to corrosion problems. In the usual environment, no additional corrosion protection is required. However, you may want to add corrosion protection, especially if you will operate or store the aircraft near salt water and/or in a polluted industrial area. To add corrosion protection, the internal structure must be primed with Zinc-Chromate (Zn-Cr) primer. This must be applied before parts are riveted together. In the kit, pre-riveted parts, such as the wing spars, have been primed at the factory. NOTICE: If using Zinc-Chromate primer, follow the primer manufacturer's directions.

Questions or problems as you're building? Think your question or problem through. Often the answer and solution is very obvious and logical. If you can't solve it yourself, feel free to contact Zenith Aircraft Company with your questions. Remember, it's best that you submit technical questions on paper: draw us a sketch of your problem, and FAX or mail it to us for a prompt response, or call or email us.

You will need all the kit parts that make up the rudder tail section: You will notice that the parts are conveniently labeled for easy identification. The first three numbers indicate the page number on which the part appears in the Drawings and the last number is the specific part number as it appears on the Drawing:

For example, the part labeled 6-T-4-1 is the first part detailed on Page 6-T-4 of the Drawings.

Rudder Kit Parts:

• See Assembly Drawing T2

Drawings: Only two pages of the actual Drawings are needed to assemble the rudder: (6-T-0), 6-T-4 and 6-T-5, and the rudder assembly is briefly outlined on Page 22 of the Construction Manual. The relevant pages have been reproduced from the Drawings for this manual:

Drawings List:

6-T-0
6-T-4 (1)
6-T-4 (2)
6-T-4 (3)
6-T-5 (1)
6-T-5 (2)
6-T-5 (3)

Inspect all the parts that make up the rudder section. Notice that you can verify all part dimensions and specifications against those shown in the Drawings (the drawings are actual blueprints and not just assembly drawings). Make sure the parts are in good shape, dry and clean (remove tape, labels, etc.).

HANDLE THE PARTS WITH CARE, ESPECIALLY PRE-FORMED SKINS.

Positioning the Doubler Angles (6-T-4-5) inside the SPAR (6-T-4-4)

• See Assembly Drawing T4 and Drawing 6-T-4 (1)

Once positioned properly, drill the marked hole (at top of doubler) through into the SPAR (#30 drill). Repeat with other doubler. After drilling, place a Cleco in the hole to clamp the assembly together. Using small clamp or vise, clamp the Doublers firmly to the SPAR about 50mm up from the bottom of the SPAR so that the Doublers are firmly positioned in place.

HINT ON DRILLING: When drilling through an existing hole, avoid enlarging that hole. If you find this to be a problem, consider under-sizing your first hole, and then re-drilling it to proper size later. Also, don't press too hard with the drill (this will minimize drill ‘travel’) and prevent the part underneath from bending under the drill's pressure.

Next, the bottom of the doublers must be trimmed to clear RR#1, as you'll notice RR#1 is angled up 27-degrees (SEE DRAWING 6-T-4 (1)): Mark about 10 mm. up from the bottom of the doublers, and trim off the angle on one side with sheet-metal snips. Repeat this for the other Doubler (remember that there is a left & right Doubler).

Installing Rear Rib 1 (RR#1) to the Spar (SPAR)

• See Assembly Drawing T6

NOTICE: When drawing a rivet position line across a rib flange, draw the line straight so that it is parallel to the flange radius (and not necessarily the flange edge).

Center RR#1 to the SPAR and position RR#1 so that you can see the drawn line on the SPAR through the drilled holes in RR#1. When positioning RR#1 to the SPAR, the SPAR Doublers should extend only to (and not into) the bottom radius of RR#1.

HINT: Keep drill bits SHARP. The drill bit is probably dull if you find you have to press too hard with your drill: sharpen or replace the bit.

Positioning RR#3 and RR#4 to the SPAR

• See Assembly Drawing T6

RR#4: Then measure up 970 mm. (from bottom of SPAR assembly) and draw a straight line (perpendicular to center of SPAR) where RR#4 will be positioned, mark the 3 rivet holes, and then drill through.

Positioning RR#2 (6-T-4-7) to the SPAR

RR#2 is positioned approx. 340 mm. from the bottom of the SPAR assembly. Draw four hole marks along line, evenly spaced (that will provide the required Edge Distance on the RR#2 rib flange). Drill the marked holes through the SPAR assembly.

Positioning the Nose Rib (6-T-4-1)

• See Assembly Drawing T8

The Nose Rib is positioned 20 mm. above the positioning holes for RR#3, as shown on Drawing 6-T-5.

Draw a straight line on SPAR 610 mm. from bottom of SPAR assembly (or 20 mm. above RR#3), and draw 4 hole marks, evenly spaced. Drill the holes through the SPAR assembly.

Draw a center line along the short Nose Rib flange, and center the Nose Rib across the drilled holes on the SPAR. Notice that the Nose Rib flanges face DOWN when positioned on SPAR.

Line the Nose Rib (NR) on the SPAR so that you can see the drawn center line on the NR flange through the drilled SPAR holes. Drill through SPAR HOLES into the Nose Rib, and Cleco in position. Drill all 4 holes.

Drilling the Doublers (6-T-4-5)

Pitch = 40, except top three holes where Pitch = 20. Notice that there are already some drilled holes along the Doublers (from positioning the ribs). Space the new holes evenly (approx. pitch 40), and remember to provide proper edge distance at both the top and bottom of the Doublers.

Cleco the Doublers back into the SPAR, and drill the marked holes through both the Doubler and SPAR. Remember to use additional Clecos as you drill (every 3 or 4 holes).

Cleco RR#1 back onto the SPAR assembly. Notice that the Doublers extend beyond the bottom of the SPAR.

Mark and drill a hole in the bottom of the RR#1 flange into the Doubler (approx. 20 mm. from the next hole above). Repeat on other side.

Installing RR#2 (6-T-4-7)

Draw a straight center line along RR#2 rib flange (remember to use the radius of the flange as the reference).

Position RR#2 in the SPAR assembly, properly centered (as shown on Drawing 6-T-5). Remember to line the rib in the SPAR so that you can see the drawn center line on the rib flange through the drilled SPAR holes. Notice rib flanges must face up.

Drill through the 4 SPAR holes into RR#2 (use Clecos).

HINT: Extend a length of 2X2 beam over the edge of your table, placing the SPAR on the 2X2, sandwiching RR#2 between the SPAR and 2X2.

Installing RR#3 (6-T-4-8) - SAME AS RR#2 instructions

Draw a straight center line along RR#3 rib flange (remember to use the radius of the flange as the reference).

Position RR#3 in the SPAR assembly, properly centered (as shown on Drawing 6-T-5). Remember to line the rib in the SPAR so that you can see the drawn center line on the rib flange through the drilled SPAR holes. Position rib according to Drawing 6-T-5.

Drill through the 4 SPAR holes into RR#3 (use Clecos).

Installing RR#4 (6-T-4-9) - SAME AS RR#2 & 3

• See Assembly Drawing T6

Draw a straight center line along RR#4 rib flange (remember to use the radius of the flange as the reference).

Position RR#4 in the SPAR assembly, properly centered (as shown on Drawing 6-T-5). Remember to line the rib in the SPAR so that you can see the drawn center line on the rib flange through the drilled SPAR holes.

Drill through the 3 SPAR holes into RR#4 (use Clecos).

HINT ON DRILLING: Do not press TOO HARD on the material when drilling, so that you don't dent or stretch the material when drilling. You may find that when drilling into a flange, you can bend the flange if you press down too hard with your drill. If you find that you have to press hard, your drill bit probably needs to be sharpened (or replaced).

Installing the Tip Rib (6-T-4-2)

• See Assembly Drawing T8 & T10

The small Angle Strip Support (.025 x 35 mm x 75 mm - no part number provided in the Drawings) attaches the Tip Rib (TR) to the SPAR section, as shown on the Drawing.

Mark and drill 4 holes on the short side of the angle strip support (2 rows x 2, edge distance approx. 10 mm.).

Draw a straight perpendicular line across the inside of the Tip Rib 50 mm. from the rib leading edge, and position the short drilled end of the Angle Strip Support in the Tip Rib, lining the radius of the Angle Strip Support to the drawn 50 mm. line.

Drill through the 4 holes into the Tip Rib, and Cleco in place.

Position the Tip Rib and Angle Strip Support assembly to the SPAR, by placing the Angle Strip Support inside the SPAR top, as shown on Drawing 6-T-5. Notice that the Tip Rib is positioned on top of the SPAR (leaving a slight clearance).

Mark 4 holes (2 rows x 2, edge distance approx. 10 mm.) on SPAR TOP, and drill (drilling through both the SPAR and Angle Strip Support). Cleco in place.

Draw center lines across all the rib flanges. These lines will be used later when positioning the skins over the ribs.

You have now completed the rudder ‘skeleton’ (internal structure). You must now take the assembly apart (remove Clecos) and de-burr all the parts (drilled holes, and material edges). If applying corrosion protection, apply after de-burring.

Cleco the parts back together again, and rivet together. Remember to read Section 4 of this manual on riveting. You may find that the holes don't match up together exactly (the rivet may not want to fit in the hole) -- if this happens, simply re-drill the holes lightly.

HINT: To de-burr hard-to-reach place (where it's difficult to access both sides with a large drill bit, use a flat file to file away any burrs.

POSITIONING THE RUDDER SKINS: IMPORTANT NOTE

• See Assembly Drawing T12

Remember to use the 3/4" wedge each time you place the rudder flat on your workbench, especially when drilling the rudder skins to the skeleton assembly, as this determines how symmetrical your rudder will be.

HANDLE THE PRE-FORMED SKINS WITH CARE. When working along the trailing edge of the pre-formed rear rudder skin, do not squeeze trailing edge, as this may force a permanent ‘kink’ in the material. If applying pressure, apply over large area so not to damage skin.

Installing the rear rudder skin (6-T-5-2) to the Rudder skeleton assembly.

• See Assembly Drawing T10 & T12

Place the rudder skeleton assembly inside the pre-formed rear rudder skin (lay flat on workbench), as shown on Drawing 6-T-5, working on one side only.

NOTICE: Handle skins with care - they are fragile and may dent with improper handling. Handle formed skins by the radius (placing hands inside radius at both ends, and lifting).

NOTICE: The pre-formed skins are purposely supplied over-sized (when applicable), and may require trimming of edges with hand snips.

The open skin edges are positioned just inside the radius of the SPAR, and the top are positioned just inside the radius of the Tip Rip (top of the rudder assembly). Mark the rib flange locations (center) along the outside edge of the skin, and then extend the lines to the rear (trailing edge) of the skin. Also mark the trailing edge end of the ribs on the skin.

See Drawing 6-T-5 (Assembly Drawing T10) for the angle positioning of the ribs:

• RR#3 and RR#4 are positioned 90^o to the SPAR (or skin edge)

• Tip Rib follows the shape of the skin (90^o to the Trailing Edge)

• RR#1 angles 63^o (90^o - 27^o) from the SPAR (or 1217 mm. from top of the rear skin trailing edge).

• RR#2 is positioned to meet RR#1 at the end (with slight clearance of 1 or 2 mm.).

Now that the rib position (rivet) lines have been marked on the skin, and that the bottom of the skin has been trimmed for size, mark the rib rivet holes on the skin, as shown on Drawing 6-T-5:

• Tip Rib: Pitch = 40

• RR#3 & 4: Pitch = 70

• RR#1 & 2: Pitch = 40

For the two end ribs (RR#1 and the Tip Rib), mark the position (rivet) lines about 8 mm. from the skin edge.

For the first hole by the spar, keep an edge distance of about 35 mm. from the skin edge (for proper edge distance on rib flanges)

For the first hole by the trailing edge, measure in about 10 mm. from the marked rib ends (for proper edge distance from rib ends).

Drill the marked rib holes on the skin.

Position the rudder skeleton assembly inside the drilled skin again, making sure it is properly positioned, and held firmly in place.

Drill holes through the pre-drilled skin into the rudder ribs (again, align the center line of the rib flange so that you can see it through the drilled skin holes).

When drilling near the trailing edge, be careful not to press too hard (do not drill right into the other side of the rudder).

For the TIP RIB and RR#1, don't use a center line on the rib flange: Position the skin edge just inside (below) the rib radius for a nice finish.

Turn rudder over on other side, and drill skin holes through to the ribs (just like the first side). Keep the CLECOS in the first side (raise the rudder on several straight 2X4 beams to provide clearance for the CLECOS).

NOTICE: Do not drill the skin to the SPAR yet, only to the ribs.

Installing the Nose Skin (6-T-5-1) to the Rudder assembly

• See Assembly Drawing T12

Keeping the rear skin Clecoed in position, place the nose skin in position on the rudder skeleton assembly (with the Nose Rib and Tip Rib in position), as shown on Drawing 6-T-5.

For positioning purposes, slid the Nose Skin in between the Rear Skin and the Spar, this is a helpful construction method to hold the Skin in place. After the skin is drilled, it is riveted to overlap on top of the Rear Skin.

Notice that the pre-formed Nose Skin is supplied slightly oversized, and may require some trimming to provide a nice finish.

NOTE: When positioning the Nose Skin make sure that the radius (leading edge) of the skin is positioned directly across the leading edge (most forward) part of the ribs.

As for the rear skin, draw the position of the two ribs (NR & TR) on the Nose Skin. Notice that the Nose Rib is set at 90-degrees to the SPAR, and that the Tip Rib angle is already set (by the rear skin).

Mark a single hole for the Tip Rib on the skin, just beyond the crimped area on the Tip Rib, and mark 5 holes on the skin for the Nose Rib (pitch 40, avoiding crimped areas).

Mark both sides of the Nose Skin, and drill the marked holes in the Nose Skin (both sides).

Drill through Nose Skin holes into the Nose Rib and Cleco. Repeat on the opposite side of the rudder.

Drilling the Rudder Skins to the SPAR

Draw a straight line on the skins along the center of the SPAR flange. Locate END HOLES (top and bottom of nose skin and rear skin) and then mark holes every 40 mm. (pitch = 40) between end holes, as shown on Drawing 6-T-5. At the bottom of the rudder, add a hole into RR#1 (beyond the end of the SPAR). By the Nose Rib, where the Nose Skin overlaps the Rear Skin, mark a hole on each side of the Nose Skin edge.

IMPORTANT: When drilling the skins to the SPAR, it is critical that the assembly is straight and flat (using 3/4-inch wedge at the rudder bottom trailing edge), as these holes will determine that the rudder assembly is straight (and without a "twist"). Closing the rudder assembly "boxes" the assembly together, giving it its strength and rigidity.

The Nose Skin overlaps the Rear Skin: The edges of the oversized Nose Skin may need to be trimmed to provide an edge distance of about 10 mm. beyond the rivet line (trim before riveting).

Draw a line inside the Nose Skin along the top of the Tip Rib.

Remove the Nose Skin, and trim off the excess material (with hand snips) and file the trimmed edge.

Riveting the Skins to the Rudder Assembly

Congratulations! You've now completed the rudder tail section, which is a significant section of your own aircraft!

Attaching the Rudder to the Fuselage

To attach the rudder section to the aircraft fuselage, the Upper Bearings (6-T-4-2) and bottom Rudder Tail Horn (6-T-5-3) must be finished, positioned, and drilled into position. It's best to install these parts later when you're ready to attach the rudder to the fuselage, as this will guarantee a perfect match to the rear fuselage.

Adobe PDF documents: Download actual rudder photo assembly guides (low resolution):

• Rudder Assembly, Section 6T4 (15 pages)
• Rudder Assembly, Section 6T5 (14 pages)
• Drawing: 6T4 and 6T5

• Rudder Starter Kit
• Factory Workshops
• Contact Zenith Aircraft Company

Copyright © 1992 - 1997 by Zenith Aircraft Company.  The above material is strictly for educational purposes.  
Actual drawings and manuals may vary from this online published material.