CLIPPED WING CUB RC47 WING CONSTRUCTION

IMPORTANT NOTE: The wing is basically constructed in three separate sections - a flat Center Section, a Right Wing Panel, and a Left Wing Panel. First you must construct the separate Right and Left Wing Panels by following all the instructions up the "Center Section" (12). Assemble each panel over its own full size plan.

10.

Wing Panels

a.

Remove carefully all wing ribs from the die-cut sheets.

b.

Pin all WA, WI, W2, W3, W4 and W5 ribs together into one group for block sanding. Put 1/4" sq. sticks in the spar slots to help hold alignment of the stack. Sand lightly where needed to smooth up the stack. Don't forget to run the sanding block along the trailing edges, as shown here, to make them all the same length. Check the overall rib length against the Wing plan.

c.

Unpin all of the ribs except the WA, WI, W2, W3, and W4s. Leave them stacked together and drill a 3/16" diameter hole vertically through the rib stack in the location for the 1/16" wire aileron push rod to pass through (refer to the bellcrank wing cross-section drawing).

d.

Pin the two 1/4" sq. Spruce Bottom Spars in place on the plan.

e.

Pin the 1/4" sq. balsa Bottom Rear Spar in place. Note that this spar is doubled in height between ribs WI to W4.

f.

Pin all of the wing ribs securely in place. Use a triangle to make sure that they are perpendicular to the board.

g.

Add the 1/4" square Spruce Top Spars. Glue all joints securely!

h.

Glue in the 1/16" Spar Webbing where indicated on the plan. A single piece of 1/16"x4-1/8"x30" balsa is provided for making these. Note that the webs should be installed with the grain running vertically.

i.

Four pieces of 3/16"x4"x1-1/2" balsa are provided for making the Spar Webs that go in rib bays W1-W2 and W2-W3. The grain direction of these webs is also vertical.

j.

Glue on the 1/8" x 7/8" balsa Leading Edge.




k.

When dry, unpin the wing from the board. Carefully sand the 1/8" Leading Edge flush with the bottom edges of the ribs.



l.

Glue on the 3/32"x3" balsa Bottom Leading Edge Sheeting. Be careful not to induce a twist or warp into the structure while pinning the sheeting in place.

m.

Pin the 3/32"x1-1/2" balsa Bottom Trailing Edge Sheeting and 3/32"x1-1/2" Bottom Aileron Sheeting in place on the plan.

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n. Pin wing panel back in place on the plan, at the same time gluing it to the Bottom Trailing Edge and Aileron Sheeting.

o.

Add small riblet W3A. Be careful about exact location. Extend a line off of the die-cut slit in ribs W4 and W5 for alignment.

p.

Add die-cut plywood riblet W5A and balsa riblets W4A and W4B. Again be careful of exact positioning.

q.

Cut to length and glue in place the 5/16"x1-1/8" balsa Tapered T.E. stock. Fill-In between the last two full length W4 ribs at the wingtip. Take down the top surface with a small sanding block until it's flush with the tops of the ribs.


r.

Glue on the 3/32"x1-1/2" balsa Top Trailing Edge Sheeting. Epoxy glue is recommended here for two reasons: First, it will have less tendancy to bow or warp the trailing edge, than would a water-base glue. Second, it gives you plenty of time to get the top sheeting pinned down securely, absolutely flat on the board.

s.

Add the 3/32"x1-1/2" balsa Top Aileron Sheeting. Check the location carefully with the aileron cross-section drawings.



t.

Glue gusset WG-1 in place against rib W3 and inside the trailing edge sheets.

u.

Carve and sand the 1/8" Leading Edge flush with the tops of the ribs.

v.

Glue and pin in place the 3/32"x3" balsa Top Leading Edge Sheeting. Also add the sheeting that goes over ribs W1 and W2 (cut from 3/32"x4"x36" stock).



w.

Cut to length and glue on all of the 3/32"x1/4" balsa Capstrips for the top of the wing.

x.

After the wing has thoroughly dried, unpin it from the board and install the die-cut plywood strut mounts FSM, RSM,and JSM on the bottom.

y.

Sheet over the bottom of ribs W1 and W2 with 3/32" x 4" balsa. Leave a gap in the sheeting where the die-cut ply Rear Dihedral Brace goes. It will be installed later.


z.

Add all of the bottom Capstrips.

Do not block sand the wing panels yet!

11.

Wing Tips

a.

Glue die-cut balsa parts T-4, T-5, T-6 and W6 in place on the die-cut ply wingtip plate WTP.

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b. Study the Wingtip Alignment Drawing carefully in preparation for gluing the Tip Plate onto the end of the wing panel. Proper positioning of it against the W4 end rib is important for correct assembly of the rest of the wingtip parts in subsequent steps. First trial fit the Tip Plate assembly in place, noting that the tops of T-4 and T-5 should line up with the top of W4, not with the top of the capstrip. Also note that the front edge of WTP should be flush with the front of the 1/8" balsa Leading Edge. Use a straight edge to draw guidelines on the end rib to help line up the Tip Plate. Then glue it on.
c. Glue die-cut balsa parts T-l and T-2 in place. Note that they should line up with the top and bottom edges of W4, leaving room for the 3/32" balsa top and bottom sheeting to be added later. Since W4 was stack sanded with the rest of the full-length wing ribs, and T-1 and T-2 were not, it may be necessary to alter the curved sides of T-1 and T-2 to exactly the same curvature as W4, before gluing them on.

d.

Glue on part T-3.

e.

1/16"x3/4"x24" balsa strips are provided for laminating around the edges of the tip. Thanks to the large radius of the curve, it should not be necessary to soak the strips in water before laminating - thus Jet, Hot Stuff, or other cyanacrylate adhesives can be used. Carefully bend and glue the first strip to WTP. Add the other strips, one at a time, firmly gluing them to each other without gaps.

f.

When the laminated edge is dry, sand flush with the front of the wing panel and glue on the 3/8"x1" balsa Leading Edge Cap.

g.

Cut a small gusset, from scrap balsa, to go in the corner of the wingtip near the trailing edge. Glue on the top side of WTP only.

h.

Sheet the top and bottom of the Tip Leading Edge with 3/32" balsa.

i.

Capstrip the top and bottom of rib W6.
j. Carve and sand the wing Leading Edge Cap and the tip laminated edge to shape. Study the photos and drawings carefully for guidance. Do not sand the rest of the wing, especially the top and bottom sheeting or capstrips, at this time - it's best to wait until the center section is done!


12.

Center Section

Join the Right Wing Panel plan to the center Section/Left Wing Panel plan, along line X-Y. It is recommended that you have a building board at least 72" long for constructing the Center Section and joining the Wing Panels to it. Pin the plan to the board and cover the center section with waxed paper.

a.

Cut 3/32"x4" sheet balsa to cover the bottom of the Center Section. Pin in place on the plan, being careful not to let the ends of the sheeting extend past the side lines of the Center Section into the Wing Panel areas. Don't forget to cut the window opening! And leave a small gap in the sheeting where the ply Rear Dihedral Brace will be installed later.

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b. Cut to length a 1/4"x3/8" balsa stick and glue it onto the front edge of the bottom sheeting.

c.

Pin all the 1/4" sq. balsa bottom spars, the two center WA ribs, and the WSP pieces in place. After you get these parts squared up with each other, glue all the joints. When dry, sand the tops of the WSP pieces down flush with the tops of the ribs.

d.

Glue the 1/4"x7/8"x16" ply Front Dihedral Brace onto the front of the ribs and the 1/4"x3/8" stick. Use 5-minute epoxy. Make sure the Brace is centered spanwise so that it will extend an equal distance into the Right and Left Wing Panels.




e.

In preparation for gluing the wing panels to the center section, first trial fit them without glue over the Front Dihedral Brace. Do this with the center section still pinned to the board. The panels should slide on smoothly until they are snug up against the center section bottom sheeting. The wingtips should be blocked up 1/2" at the last W4 rib for scale dihedral. Make any slight alterations where necessary to allow the wing panels to fit properly to the center section. When satisfied that the panels fit, glue them to the center section one at a time. Use slow-drying epoxy glue to allow yourself plenty of alignment time. Follow these steps:
  1. First coat the back side of the Front Dihedral Brace with glue.
  2. Use a wire to thoroughly coat with glue the surface of the 3/16" spar webs that the brace will bond to inside the wing panel.
  3. Run a small bead of glue along the edge of the center section bottom sheeting.
  4. Then slide the wing panel in place and pin securely.
  5. Coat the adjoining WA rib with glue and pin it tightly against the panel's WI rib.
  6. Attach the opposite wing panel using the same procedure. Then let the entire wing assembly dry before continuing.
f. Glue in all 1/4" sq. balsa top spars.


g.

Add a 1/4"x 3/8" balsa stick on top of the Front Dihedral Brace, along the front of the WA ribs. Carve the excess down flush with the tops of the ribs.

h.

Fill in between the WA ribs, where the wing bolts will go through, with 5/16"x1-1/8" Tapered T.E. Stock. Carve or sand down flush with the tops of the ribs.

i.

Glue on the 3/32"x2"x6-1/4" plywood Center Section T.E. Top Sheet.

j.

Cover the top of the Center Section with 3/32"x4" sheet balsa. When dry, unpin the wing from the plan.

k.

Working through the opening you left in the bottom wing sheeting, use a razor saw to slot the WA,WI, and W2 ribs just in front of the rear spruce spars to accept the die-cut plywood Rear Dihedral Brace



l.

Epoxy the Brace to the spars. Glue 3/32" sheet balsa in the gaps in the bottom sheeting.

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m. Carve and sand the trailing edges round. Carefully block sand the entire wing until all joints are smooth and even. Use as large a block as possible to avoid sanding down anyone area too much.

13.

Cutting Out The Ailerons

a.

Locate the 1/4" sq. balsa Bottom Spar under the Top and Bottom Aileron Sheeting. Draw guidelines on both sheets about 1/32" behind the spar. Use a straight edge and a sharp knife to cut through the Aileron Sheeting along the guidelines. Make sure you are not cutting into the spar.

b.

Take an X-Acto razor saw and pry the crimped metal backing off of the blade with a screwdriver. Insert the saw blade into the slits just cut in the Aileron Sheeting and saw through each of the ribs of the aileron.

c.

Saw through the trailing edge and carefully remove the aileron.

d.

Trim and sand the back of the wing cutout until all ribs and planking are flush with the back of the balsa spar.




e.

Trim the aileron front in line with the rib angled die-cut slits. Use a sanding block to straighten the aileron front and ends.

f.

Glue 1/4"x1-1/2" balsa into the wing cutout and to the front of the aileron. Trim and sand these pieces to wing contour.

g.

With a razor saw, cut the base off one of the long nylon control horns that are supplied. Drill some random glue anchor holes in the top area of the horn.

h.

Inlet the bottom leading edge of the aileron to allow the nylon horn to be slid in place alongside the plywood riblet W5A. Refer to the aileron cross-section drawing to see how far in the horn should be installed. Hold the horn in position and drill a small pilot hole (for a #2x3/8" sheet metal screw) through one of the glue anchor holes and into the ply rib. Screw and epoxy the horn securely in place.




i.

Fill in behind the horn, on the bottom of the aileron, with 3/32" sheet balsa. Sand flush. This will give you somewhere to attach the covering material. If you wish to cover the ailerons before hinging, do it now.

j.

Cut slots in the aileron leading edge and the wing cutout to accept the nylon hinges. Use 4 hinges per aileronl Check the fit and movement of the aileron by dry fitting it into the wing first without any glue on the hinges. If there is any mismatch or binding, alter the slots as necessary to correct. Epoxy the hinges in. Repeat these steps to complete the other aileron.

14.

Mating The Wing To The Fuselage

a.

Epoxy the 3/8"x1-1/2"x5-3/8" basswood Wing Bolt Block in place. Brace it to the lite-ply Cabin Bulkhead with 1" triangular balsa. Let dry.

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b. Set the wing on the fuselage, sliding it forward as far as possible. Mark and drill a 5/32"x5/16" hole in the wing's Front Dihedral Brace for the Cabin Wires to go through. The wing should then slide all the way forward with the trailing edge dropping down in front of the T.E Crosspiece. If necessary, adjust the hole slightly with a rat-tail file to eliminate any binding that keeps the wing from setting flat on the cabin.

c.

Tape or pin the wing in correct alignment with the fuselage measure from the wingtip to the back end of the fuselage. Determine the correct spots on the top of the wing to drill through and hit the Wing Bolt Block in the desired locations for the nylon bolts. Drill through the wing and Wing Bolt Block at the same time with a No.7 drill. Take the wing off and tap the Block with a 1/4-20 tap. Enlarge the holes in the wing to 1/4" diameter to pass the nylon bolts.

d.

Mark the locations for the 1/4" Dowels that go in former F5 (see cross-section F5). With the wing in place on the fuselage, drill 1/4" diameter holes completely through both F5 and the wing's Front Dihedral Brace at the same time. Remove the wing and epoxy the dowels in place in F5. Wipe any excess glue from the wing side of F5.



e.

1-3/4"x2-1/4"x2-1/2" balsa blocks are supplied for making the Cabin Blocks. Study the Front, Top, and Side views of the Cabin Blocks on the fuselage plans. Trim the blocks supplied roughly to match these three viewpoints. Leave them slightly oversize. Then glue them in place on the front of former F5. Sand and trim to match the contour of the wing.

15.

Wing Struts

Assembly of the wing struts requires the completed wing and fuselage.

a.

Locate the two 1/16"x1/2"x2" aluminum strips supplied for the Fuse Strut Fittings. Round all four corners of the strips with a file or grinder, and drill three holes through each with a #33 drill bit (see plan for exact locations). Draw a line across the middle of each strip. clamp it in a vise up to the line, and bend it to the angle shown.

b.

Mount the finished Fuse Strut Fittings in place on the bottom of the fuselage with 4-40 x 3/8" mounting bolts and blind nuts. Epoxy the blind nuts on the inside of the fuselage.

c.

Two pieces of 1/16"x1-3/16" (tapered) x 2" aluminum are supplied for making the Lower Strut Fittings. On each piece, round the corners of the narrow end and drill a #33 hole in the location shown on the plan. Also drill several random glue anchor holes along the sides where the spruce struts will be glued on.




d.

Mark the four notched 1/4"x1/2" spruce struts as to which two are Front and which two are Rear - there is a difference in length (see plan). Taper the fuselage end of each Rear Strut so it will fit onto the brass Lower Fitting along with the Front Strut. Epoxy one Front and one Rear Strut onto each of the aluminum Lower Strut Fittings - make two identical assemblies. Work directly over the Wing Strut plan to insure that the angle between the struts will be correct.

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(NOTE: At this point, there is no "right" or "left" difference between the two wing strut assemblies, as is called for on the plan.)

e.

Four pieces of 1/16"x1/2"x2-1/4" aluminum are provided for making the Upper Strut Fittings. Drill, shape, and bend these pieces as shown on the plan to make two #1 and two #2 Upper Strut Fittings. (The difference between the finished right and left wing strut assemblies will be in these Upper Strut Fittings. That's why they are called #1 and #2 on the plan - notice that the slant of their bend lines go in opposite directions.)

f.

Bolt the wing in place on the fuselage. Fasten the wing strut assemblies in position, one on each side of the fuse, by bolting the Lower Strut Fittings to the Fuse Strut Fittings. Make sure you have the shorter front strut of each assembly facing the front of the airplane. Trial fit, without glue, the finished Upper Strut Fittings into the notches in the spruce Struts as follows:
RIGHT WING STRUT ASSEMBLY - A #2 Upper Strut Fitting goes in the Front Spruce Strut
A #1 Upper Strut Fitting goes in the Rear Spruce Strut
LEFT WING STRUT ASSEMBLY - A #1 Upper Strut Fitting goes in the Front Spruce Strut
A #2 Upper Strut Fitting goes in the Rear Spruce Strut

Check that the Upper Fittings mate smoothly to their ply mounting inserts (FSM and RSM) that are built into the wing. If they don't, double check to see that you've got the correct Upper Fitting in the correct strut. You may also have to readjust the bend angles of the Upper Fittings and/or Fuse Fittings slightly to get a good fit. When satisfied, take the struts off the model and epoxy the Upper Fittings into their proper notches.

g.

When dry, bolt the strut assemblies back on the model. Hold the Upper Fittings up against the bottom of the wing and mark the locations for the 4-40 mounting bolts onto the ply mounting insert FSM and RSM. Take the struts back off. Drill holes through the ply inserts and epoxy 4-40 blind nuts in from the inside (you'll have to make a small opening in the front spar webbing to get the front blind nuts in).

h.

Carve and sand the edges of the struts round. See cross-section on strut plan.

i.

Reinforce the ends of the spruce struts over the brass fittings with a layer of fiberglass cloth and epoxy glue. Also cover the areas in the center of each strut where the jury struts will go. When dry, sand smooth.

j.

Install 4-40 blind nuts in the ply Jury Strut Mount inserts (JSM) that are built into the wing. Epoxy the blind nuts in the exact locations shown on the plan.

k.

Four pieces of 3/16" o.d. x 7" long brass tubing are provided for making the Front and Rear Jury Struts. There are patterns and instructions on the plan to use as a guide for bending them to shape. A regular hand pliers works best for flattening and bending the ends of the tubing. Try to bend them exactly along the lines drawn, but don't make the bends too sharp or the tubing could crack.

l.

Bolt the top ends of the finished Front and Rear Jury Struts to the wing. Swing the bottom ends in position to line up with the spruce struts. (Be careful not to bow the spruce struts out of shape - make the brass jury struts meet the spruce!) Mark and drill the holes for the 4-40 flat head bolts that secure the bottom ends to the spruce struts. Countersink the holes so that the heads of the bolts are flush with the bottom of the spruce struts.



m.

Cut to length, flatten and drill the ends of the two 4" long pieces of brass tubing provided for the Bottom Jury Struts. Due to small differences between models, it's impossible to give you a useable pattern for these pieces. You'll have to tailor them to fit on your own model.

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n. Make a final assembly of all the strut pieces to the model. During the assembly epoxy the flat head bolts into the spruce struts; epoxy together the lower ends of the Jury Struts where they overlap; and epoxy on the 4-40 hex nuts that hold them all together. Let dry before taking off the model.

16.

Attaching The Tail Surfaces

If you've precovered the stabilizer, remove the covering material from the bottom center area where it will contact the fuselage.

a.

With the wings mounted to the fuselage, pin the hinged stab/elevator assembly in place. Note that the fuse will need to be trimmed slightly under the elevator joiner to permit adequate movement of the elevators. Carefully align the stab with the wings from the top and front views. Mark the location of the fuse on the top and bottom of the stab center section. Remove the stab and apply epoxy glue. Slow drying epoxy (not 5-minute) is recommended to allow adequate time to get the stab in exact alignment before the glue hardens. Pin the stab back in place using the markings to get it in approximate alignment. Before the glue hardens, recheck the alignment carefully by measurement and shift the stab position slightly if necessary.


b.

Epoxy the hinged fin/rudder assembly in place, installing the bottom hinge into the rear of the fuselage at the same time. Align carefully.

c.

Glue the die-cut 1/8" balsa Tail Fairings in place. They should be flush with the fuselage sides at the stab leading edge and touching the fin at the back.

FINISHING

17.

Radio Installation

It's best to mount all your radio equipment and pushrods before covering and painting, while you still have easy access inside the model. Once the initial installation has been made and all the bugs are worked out, you can take the radio system back out while the painting is being done.

In spite of some of the things you may have heard or read, putting a radio in your 1/4-scale Cub need not be much different than for a smaller model. This section describes the control system installations that have worked best in our prototype Cubs and that we recommend. Except for the use of some "heavy-duty" parts, you'll find that the installation is pretty straight forward. As with any size model, the QUALITY of the installation more than anything else will determine how well it flys the model.

Always double check all control hookups! Locate the source of any binding, rubbing, or sticking and eliminate it.

No radio gear or servo mounting materials are supplied in this kit. Any other parts called for in the instructions that we do not furnish are marked with an (*).

Elevator And Rudder Hookup

The elevator and rudder are each actuated by one "heavy-duty" servo. Almost every radio manufacturer produces heavy-duty servos specifically designed to handle the increased control surface weights and air loads of 1/4-scale models. Standard size servos (35 oz./in. torque or less) are not recommended for the elevator or rudder of the Cub. If in doubt about the ability of the servos you have to handle the job, consult the manufacturer of the radio gear.

The most convenient method of installing servos in the fuselage is on the plastic mounts (*) that are offered by most radio manufacturer for their equipment. These are screwed to hardwood mounting rails (*) that are epoxied across the inside of the cabin area. Mount your servos anywhere between formers F5 and F6. Further instructions on the use of servo trays are usually included with them.

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A long nylon control horn is supplied for the elevator. Install it on the bottom of the left elevator with #2x3/4" sheet metal screws. Once installed, cut off the excess ends of the screws flush with the top of the nylon retainer plate.

Pushrod Assembly

Materials are supplied for building fiberglass pushrods to link the elevator and rudder servos to their control horns. Make the control surface ends of the pushrods first.

Put a 90 bend in the unthreaded end of the 4-40x8" threaded rod. Drill a 3/32" diameter hole 2" from the end of the fiberglass pushrod tube. Slide the 4-40 rod into the tube, sticking the 90 bend through the hole.

Sand a flat spot on one side of the 3/16"x2-1/2" dowel until it can be squeezed into the tube alongside the 4-40 rod. When you get the fit right, final assemble the parts into the tubes with epoxy glue. It should not be necessary to put any bends in the 4-40 wires of either the elevator or rudder pushrod to get them to feed through the fuselage and hook up to the control horns. It's a pretty straight shot if your servos are positioned side by side as shown in a previous photo. However you may have to trim out a portion of the diagonal 5/16" sq. main frame balsa under the stab to clear the elevator pushrod wire.

Assemble the servo ends of both pushrods in the same fashion, only use 1/16" dia. x 8" music wire and solder links instead of the 4-40 size hardware. After you've got the 1/16" wires and dowels epoxied into the tubes, feed the pushrods back into the fuselage and hook up to the control surfaces. Center the 4-40 links on the threads at the tail end. Then measure and cut off the 1/16" wires at the front, to the length which will allow the solder links to reach the servo arms. Protect the servos with a rag while soldering the links onto the ends of the wires.

Your elevator and rudder pushrods should now be complete and operating freely. Fill in around the 4-40 pushrod wires where they exit the fuselage with scrap sheet balsa, glued in flush with the stringers.

Brace the pushrods in the middle (near former F9) with 1/4" sq. scrap balsa to eliminate any possibility of in-flight vibration or bowing problems. Criss-cross pieces of 1/4" sq. stick on all four sides of each push rod. Glue them to the 5/16" sq. main frame balsa. Have the braces touching the pushrods, but not creating a bind.




Throttle Hookup

Either a standard or heavy-duty servo can be used for the throttle control on a .60 to .90 glow engine. A flexible steel cable pushrod with nylon outer tubing (*, such as SIGSH559) is best for hookup of the throttle servo to the carburetor. Follow the assembly instructions on the pushrod package.


Battery Pack

Due to the larger than normal battery drain from using heavy-duty servos, a 1000 mah receiver battery pack (*) is recommended. Wrap the battery pack in foam rubber (*, such as SIGRF240) held on with rubber bands or masking tape, to protect it from engine vibration. Secure it as far forward as possible in the nose under the fuel tank.

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Receiver

The receiver should also be wrapped in foam rubber and stowed as far forward as possible. Make certain that it is somehow fastened in place so it will not move around during flight. A 36" long piece of large (3/16" o.d. approx.) nylon tubing is provided for making an internal antenna mount. Glue the tube in a bottom corner of the fuselage, from the cabin area back to the tail, and slide the antenna wire into it.

Switch

The receiver on/off switch may be mounted wherever it is convenient. Some servo trays have a slot along the front for holding the switch. Then run a short length of music wire (*) from the switch to the outside of the model.

Aileron Hookup


One heavy-duty servo, such as recommended for the elevator and rudder, can safely operate both ailerons at the same time from the center of the wing through the use of 90 aileron bellcranks. The full size wing plan shows the servo mounting, bellcranks, and pushrods in place in the wing. The importance of making the installation operate perfectly smooth and friction free can't be over emphasized. A heavy-duty 1/4-scale servo is more than strong enough to handle the flight loads of both ailerons if its power isn't being robbed by a balky bellcrank installation. There is no room for sloppiness or mismatched assembly. With a little patience and forethought, your installation can be dependable and trouble free.

Two pieces of 3/32"x2-1/2"x4-1/8" plywood are provided for the bellcrank mounts. Do not glue them into the wing at this time! First assemble the bellcranks onto the ply mounts as shown here. Locate the holes for the music wire pivots according to the wing plan drawing.

Be sure to make a right and a left bellcrank assembly. Sand the balsa spacer blocks down until the bellcranks and washers just fit between the ply pieces with a minimum of clearance. Do not sand the blocks too small and put a bind in the bellcrank movement. Epoxy the spacer blocks and top ply supports to the ply mounts. Slip the bellcranks and washers in place and epoxy the music wire pivots to the ply pieces. Make sure the bellcranks operate freely up to this point.

A 36" long piece of small (1/8" o.d. approx.) nylon tubing is provided. Cut it into two 18" long pieces and slide these into the holes you drilled into the wing ribs during the wing panel construction. Slide the 1/16" dia. music wire pushrods inside the.nylon tubes. Check for any binding that may be caused by slight misalignment of the holes. Then epoxy the nylon tube to all the ribs except for the W1s and WAs in the center section.

Pull the 1/16" pushrod wires out and make a "Z" bend in the end of each. Trial fit them and the bellcrank assemblies in the wing to check that the "Z" bends don't bind on the bellcranks.

Bend the 4-40 x 8" threaded rods to the shape shown in the wing cross-section drawing. Trial fit them into the control system and check again for binding. Fasten the enthreaded ends of the rods to the bellcranks with a "Z" bend, or by bending 90 and soldering on a small washer (*). Only after you've got the entire aileron control linkage assembled and operating freely should you glue the ply bellcrank mount platforms to the wing ribs.

The aileron servo can be mounted in the center section and linked to the 1/16" pushrod wires several ways. You may have your own favorite method. The following two photos show different installations which vary only in the brand of servo used and the positioning of it in the center section window.


The first photo shows a Kraft KPS-20H servo mounted vertically into the window from the bottom of the wing. The photo was taken looking through the top window and is the same installation that is drawn on Plate 3 of the full size plans. The second photo shows an Airtronics 94554 servo flat mounted onto a piece of plywood that was glued into the window opening. In both installations, the right and left 1/16" pushrod wires have been spliced together with a piece of 1/16" i.d. brass tubing (*). Then a 1/16" spur wire (*) must be bent to link the pushrods to the servo arm. Wrap and solder the spur wire onto the pushrods. You'll probably find that the holes in the two center WA wing ribs will need to be oblonged slightly to allow the pushrods to flex with the rotary motion of the servo without binding.

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Optional Aileron Hookup

(* No materials are supplied for this option.)
Some 1/4-scale flyers prefer to use two separate servos to operate the ailerons. We have tried this method (see photo) and can recommend it if you want to go to the expense of buying an extra servo. It's actually easier to hook up than the one servolbellcrank method. Mount the servos in the same rib bays where the bellcranks would be. Build a removable hatch between the ribs so you can get at the servos when necessary. Use long extension cords and a "Y" junction cord to link the servos to the receiver. Consult your radio manufacturer about the need and availability of "chokes" to eliminate any possible radio interference from the long extension wires.


18.

Tips On Tanks

A 16 oz. rectangular plastic clunk tank is recommended for use with most all .60 to .90 cu. in. glow engines. Refer to the engine manufacturer's instructions for any special notes they may have on fuel tank or pump/pressure requirements for your particular engine.

The simplest, most trouble free, tank set-up to use with a fully cowled in engine is normal suction feed, without any pump or crankcase pressure. If you can run your engine on suction, assemble the fuel tank hardware as shown in the photo. There are 3 tubes installed through the rubber stopper - 1 for fuel feed, and 2 for vents. Both vent tubes should curve upwards inside the tank. The clunk line on the fuel feed tube must swing freely without hitting the back of the tank. (If your tank, as supplied, does not come with silicone tubing for the internal fuel feed line, substitute a piece of Sig Heat-Proof Silicone Tubing, SIGSH290 Large. With it installed, the tank can be left in the fuselage indefinitely since this line will not harden or deteriorate when immersed in raw fuel.)

With an inverted engine installation, the tank will be correctly located for proper fuel draw and idle characteristics if it is mounted onto the bottom of the ply Nose Joiner. Simply glue four J-Bolts (SIGSH123, not supplied) into the bottom of the NoseJoiner, and use rubber bands hooked between them to hold the tank in place, as shown.




Drill holes through the firewall large enough to pass the fuel lines through. Once the tank is installed permanently, after painting the model, seal the holes in the firewall against leakage of the exhaust oil into the fuselage with silicone rubber sealer. Run fuel tubing from both vents downward and out the bottom of the cowl at the back. Connect the fuel feed line to the carburetor. To refuel, simply pump fuel into either of the vent lines until it runs out the other. Then plug one of the vents with a short 4-40 bolt to keep the fuel from siphoning out. It's not necessary to remove the feed line from the carb to refuel.