The MID-STAR 40 was designed for mid level R/C pilots who are looking for and easy-to-build sport plane. Its mid wing and light weight combine to make it a stable platform for novices moving up from their high wing trainer. Advanced pilots will find the MID-STAR 40 is capable of almost any trick "in the book", yet will slow down for soft gentle landings. It can be flown from pavement or grass, and it handles the wind well for such a light model.

Easy construction was a top priority for this design. The Lite-Ply fuselage virtually snaps together and results in a strong, lightweight structure. The wing has no leading edge sheeting, which helps speed construction. The simple, pre-cut balsa tail parts also save time. The model can be completely covered with iron-on film, with only a small amount of painting required.

One important decision that you will need to make before building is whether to use tricycle landing gear on your MID-STAR 40 or make it a taildragger. New pilots who are transitioning from a tri-geared trainer may want to stick with the tricycle setup, which generally helps to make takeoffs easier. The main advantage of choosing the optional taildragger version is that you will save considerable weight (no nose gear), resulting in increased performance. The tail dragger version handles very well on the ground - if you've always wanted to try a taildragger, this would definitely be a good one to start with.


Recommended Glues

There are so many different glues available today for model construction that it can be confusing to even the experienced modeler. To simplify matters, most glues can be classified as one of four basic types:
  1. Fast-drying cyanoacrylate adhesives ( abbreviated in these instructions as "CA") such as SIG CA, Hot Stuff, Jet, etc .....
  2. Easy-to-use water-base wood glues such as SIG-BOND (yellow) and SIG SUPER-WELD (white).
  3. Super strong two-part epoxy glues such as SIG KWIK-SET (5-minute cure) and SIG EPOXY (3-hour cure).
  4. Traditional solvent-base model cements such as SIG-MENT.
Each of these types has different characteristics and advantages. Often times, the choice of which type to use is strictly a matter of personal preference based on your prior experience with a previous model. However, because of the vast use of Lite-Ply and hardwoods in the MID-STAR 40, we have found that the CA glues seem to work the best for general construction. In fact, the construction sequence of the fuselage is designed with the use of CA glue in mind. Other glues could be used, but CA is recommended as our first choice because of its ability to penetrate an already assembled joint. In other words, the fuse parts can first be assembled dry (without glue), the alignment checked and adjusted, and then the glue can be applied to the joints. You should also have on hand some epoxy (both 5-minute and slow dry) and Sig-Bond because these glues are called out in several of the steps in this book.

Sig CA, like most brands of cyanoacrylates, comes in three viscosities - thin, medium and thick. An accelerator spray and debonder are also available and are described below.
  • Sig CA Thin - Watery in consistency, thin CA should only be used when the two parts to be joined are in perfect contact with zero gap. Capiliary action pulls this glue deep into the wood resulting in a very strong bond and it dries in just a few seconds. Thin CA can be used to tack assemblies together, but these joints should be glued again later with medium or thick CA. Thin CA is also necessary for installing EASY HINGES.
  • Sig CA Medium - Our medium thickness CA is excellent for almost any step during construction, and is particularly recommended for gluing the plywood fuselage parts. The extra thickness allows the glue to fill small gaps, but it dries a little slower than thin CA. If you want only one type of CA, use medium thickness.
  • Sig CA Slow - This thickest formula is good for filing large gaps and building up strong fillets at joints requiring extra strength. It also dries slow enough to allow you to apply it to one part and position it on another before it dries. (With thin and medium CA's, the parts must be in contact and positioned correctly before glue application.) This feature is useful when laminating large sheeted areas like a fuselage side and a fuselage doubler.
  • Sig Kwik-Shot Accellerator - Spraying accellerator on CA (any thickness) will cure it almost instantly. Although CA is fast, it's sometimes nice to speed it up even more.
  • Debonder - This can be used to separate parts, but you'll probably use it for unsticking your fingers more than anything else!

Some people have experienced allergic reactions when exposed to epoxy or cyanoacrylate glues. This is very rare. However, it is always important that such glues, and also paints, thinners, and solvents, be used with adequate ventilation to carry fumes away.

Engines, Propellers, And Mufflers

There is a tremendous variety of engines available in the size range specified for the MID-STAR 40. Both 2-stroke and 4-stroke engines work equally well in this model, so choose your favourite type, keeping in mind the type or performance that you wish the model to have.

Recommended Engine Range: .30 - .40 2-Stroke
.40 - .50 4-Stroke

If you want maximum aerobatic capability and vertical performance, use an engine towards the upper end of the recommended size range. If the MID-STAR 40 is your first move up from a trainer, engine sizes from the bottom of the range may suit you better. Engines at the bottom of the range will still put the MID-STAR 40 through most aerobatic maneuvers.

Use only propellers recommended in the instructions supplied with your engine. If you use a very high-power engine in your model (such as a schneurle-ported 2-stroke .40), it's recommended that you opt for a propeller with a relatively large diameter and low-pitch. This will give you loads of pulling power during maneuvers without a lot of excess speed. If you build the tricycle-gear version and fly off grass, the prop diameter should be kept at 11" or less. If you fly off a hard-surface, you can use up to a 12" dia. prop.


There is no one type of muffler that is best suited to the MID-STAR 40. It all depends on the particular engine that you have selected. If you have a 2-stroke engine, use the muffler that was supplied with it or one of the many aftermarket mufflers that are available. As with any mid-wing model, its a good idea to install a commercially-available exhaust diverter to keep the engine exhaust from hitting directly on the leading edge of the wing. Most 4-stroke engines don't require a muffler because of their low noise production. Angle the exhaust stack on your 4-stroke engine up and away from the model.

Radio Requirements

A four-channel radio system is required for the MID-STAR 40 to operate the ailerons, elevator, rudder, and throttle. The fuselage is spacious enough that any common brand of radio equipment with standard size servos and battery pack can be used. Be certain that your radio system's frequency is approved for use in R/C nodel aircraft.

You Can't Get Along Without A Good Sanding Block

An assortment of different size sanding blocks are indispensable tools for model construction. A good general purpose block can be made by wrapping a 9"x11" sheet of sandpaper around a piece of hardwood or plywood. Use three screws along one edge to hold the overlapped ends of the sandpaper. Put 80-grit paper on the block during general construction. Switch to 220 grit paper for final sanding just before covering.

In addition to the large block, there are places where a smaller one is handy. Also, a sandpaper "file" can be made by gluing sandpaper to a flat spruce stick for working in tight places.

About The Building Sequence

The quickest and most efficient way to complete a model is to work on several pieces at the same time. While the glue is drying on one section, you can start on or proceed with another part. Work can even go forward on several sections of the same assembly at the same time, such as the front and rear sections of the fuselage.

Keep in mind that the number sequence used in these instructions was chosen as the best way to explain the building of each major component and is not intended to be followed in exact one-two-three fashion. Start on the wing at No.1 and after doing as many steps as is convenient, flip over to "FUSELAGE CONSTRUCTION" and do a step or two there, then back to "WING CONSTRUCTION" and so forth. You will, of course, arrive at points where you can go no farther until another component is available. Plan ahead, read the instructions completely and study the full size plans before beginning construction.

Refer To "The Basics Of Radio Control"

"The Basics of Radio Control" booklet has been included with this kit as a reference for installing the engine, fuel tank, and radio in the MID-STAR 40. It also contains very important information on preparing the model for flight. Modellers of all experience levels are encouraged to read this book and follow its guidelines for success.

Die-Cut Balsa Sheets
33/32"x3"x9" W-1 Wing Ribs 43/32"x3"x 18" W-2 Wing Ribs
Sheet Balsa
21/16"x1-1/4"x30" Top Trailing Edge Sheeting 21/16"x1-1/2"x30" Bottom Trailing Edge Sheeting 21/16"x3"x30" Wing Center Sheeting, Top and Bottom 183/32"x3"x1-3/16" Shear Webs (3 bundles of 6)
11/4"x4"x6" Hatch
Stick Balsa
63/16"x3/16"x30" Front Spars, Rear Spars 21/4"x1/4"x30" Trailing Edges 25/16"x5/16"x30" Leading Edges 11/4"x1"x3-5/8" Nose Brace
21/4"x1"x4-3/16" Stab Tips 11/2"x30" traingle Braces for F-1, Wing Hold Down Blocks, Landing Gear Bolck and Fin (optional)
Special Shaped Balsa
13/16"x2-1/2"x9" Pre-Cut Rudder 13/16"x4"x8-1/2" Pre-Cut Fin 21/4"x2'x9-1/2" Pre-Cut Elevators 11/4"x5"x18" Pre-Cut Stabilizer
21/4"x1"x30" Ailerons (tapered, with rounded edge) 21/4"x1/4"x18" Fuselage Stringers (beveled edges)


Die-Cut Poplar Plywood (Lite-Ply)
21/8"x5-1/4"x43-1/2" Fuselage Sides 21/8"x5-1/4"x24" Fuselage Doubler, Servo Rail Supports, Wing Tip Brace 11/8"x4-1/2"x43-1/2" FBR, FTR, BP, CF-1, CF-2, Stab Support, Stab Tip Template 11/8"x6"x32" F-2 thru F-6, F-2D, F-3S, F-4S, Wing Tips, Hatch Plates, Dual Tool, RCG-1, RCG-2
11/8"x18"x4-1/2" FBF, Tank Floor
Die-Cut Birch Plywood
13/32"x6"x9" F-1, Dihedral Brace, Hatch Tongue
Sawn Birch Plywood
21/16"x3/4"x1-1/2" Wing Hold-Down Plates 11/4"x1-1/2"x3-1/4" Landing Gear Mount
43/16"x3/8"x30" Spruce Main Wing Spars 11/4" dia.x2-1/2" Birch Wing Hold-Down Dowel, Canopy Hold-Down 21/4"x1/4"x2" Basswood Grooved Torque Rod Blocks 21/4"x7/8"x2" Basswood Wing Hold-Down Blocks
13/8"x3/8"x12" Basswood Servo Rails, Canopy Hold-Down Block
Formed Wire Parts
11/16" dia.x4-1/2" Tailwheel Wire 13/32" dia.x4" Elevator Joiner 15/32" dia.x12-1/2" Nose Gear Strut 14-40 x5" Threaded Rod, L.H. Aileron Torque Rod (with 1/8"o.d.x1-1/2" Brass Bearing)
14-40 x5" Threaded Rod, R.H. Aileron Torque Rod (with 1/8"o.d.x1-1/2" Brass Bearing)
Formed Plastic Parts
1.040 Clear Plastic Canopy 1.030 ABS Plastic Canopy Base
2Glass Filled Engine Mounts 1.090 Aluminum Landing Gear 11"x24" Fiberglass Tape (foe wing center and tailwheel wire) 26-3/4"x27" 3-Color Decal
1Full Size Printed Plan 1Photo Illustrated Instruction Booklet 1"The Basics Of Radio Control" Booklet
4#2 x1/2" Sheet Metal Screws (for control horns) 24-40 x3/8" Flat Head Mounting Bolts (for hatch) 14-40 x 3/8" Mounting Bolt (for canopy hold-down) 84-40 x1/2" Mounting Bolts (for nose gear bearing and landing gear)
46-32 x3/4" Mounting Bolts (for engine mounts) 28-32 x1-3/8" Mounting Bolts (for wheel axles) 21/4-20 x1" Nylon Wing Bolts 1#4 Flat Washer (for canopy hold-dowm)
104-40 Blind Nuts (for nose gear bearing, landing gear, and hatch) 46-32 Blind Nuts (for engine mounts) 48-32 Hex Nuts (for wheel axles) 14-40 Brass Threaded Insert (for canopy hold-down)
2Solder Link (for throttle and nose wheel) 12-56 Threaded Coupler (for throttle pushrod) 52-56 Nylon R/C Links (2/aileron, 1/rudder, 1/elevator, 1/throttle) 62-56 x 10" Threaded Rods (2/aileron, 1/rudder, 2/elevator)
1Set of 2 Nylon Aileron Connectors 15/32" Nylon Nose Gear Bearing 15/32" Nylon Steering Arm (w/brass insert and set screw) 2Nylon Control Horns (1/rudder, 1/elevator)
1Pushrod Connector Assembly (for steering arm) 2.190 o.d. x24" Nylon Outer Tubing (for rudder and elevator pushrods) 2.130" o.d. x30" Nylon Inner Tubing (for rudder and elevator pushrods) 2.130" o.d. x15" Nylon Inner Tubing (for throttle and nose wheel pushrods)
21/16" dia. x15" Steel Cable (for throttle and nose wheel pushrods) 153/4"x1" Easy Hinges


Notes Before Beginning Construction

Any references to right or left refers to your right or left as if you were seated in the cockpit.

To build good flying models, you need a good straight building board. Crooked models don't fly well! The building board can be a table, a workbench, a reject "door core" from the lumber yard, or whatever - as long as it is perfectly flat and untwisted. Cover the top surface of the building board with a piece of celotex-type wall board or foam board, into which pins can be easily pushed. Don't hesitate to use plenty of pins during assembly to hold drying parts in correct position.

When pinning and gluing parts directly over the full-size plans, cover the plan with wax paper or plastic kitchen wrap to prevent gluing the parts to the plans.

Don't use a ball point pen for making marks on the model during construction. If not sanded off, these ink marks will show through the model's final finish. Use a pencil instead of a pen.

Leave all die-cut parts in the sheets until needed in construction. Then remove the pieces from the sheets carefully. If difficulty is encountered, do not force the part from the sheet - use a modeling knife to cut it free.

The die-cut balsa and plywood parts can be identified using the plans and the "Key To Die-Cut Parts" above. Mark the identification numbers on the corresponding parts before removing them from the die-cut sheets.

All of the other parts can be identified by the "Complete Kit Parts List" above. Sort the different sizes of sticks and sheets into individual piles to avoid confusion during building.


Before beginning wing construction, carefully splice together the Left Wing Panel plans so that the "X" and "Y" indicators meet. Use a straightedge to double check the alignment of the plans before taping them at the seam. Tape or pin the plans to your building board and protect them with a layer of waxed paper. Build each wing half separately.


  1. Pin the 3/16"x3/8"x30" spruce main wing spar in place on the plan. Be careful not to place pins where they will interfere with wing ribs which will be added later.
  2. Pin the 1/16"x1-1/2"x30" balsa bottom trailing edge sheeting in place.
  3. Use about three wing ribs to accurately position the 3/16" sq. x30" balsa rear spar, then pin the spar in place.


  1. Glue eight W-2 wing ribs to the spars and trailing edge sheeting.
  2. Place scraps of 1/16" balsa near the main spar to accurately space the W-1 wing ribs up from the building board. (The spacing is required for the center sheeting to be added later.)
  3. Use the dihedral guage side of the die-cut Dual Tool to set the root W-1 rib at the proper dihedral angle before gluing it in place. Add the two remaining W-1 ribs.


  1. Glue the 1/4" sq. x 30" balsa trailing edge to the top of the T.E. sheeting and the ends of the wing ribs.
  2. Remove the pins in the bottom T.E. sheeting and re-pin the back of the wing through the trailing edge stick that you just installed.
  3. Add the 1/16"x1-1/4"x30" top trailing edge sheeting. For this step it is recommended that you use Sig-Bond (alphatic resin) along the back edge of the sheeting that glues to the trailing edge. That will make the joint easier to sand when you reach step 11. Use thin CA to tack the front edge of the sheeting to the wing ribs.



Install a pre-cut 3/32"x3"x1-3/16" balsa shear web in each rib bay except the one between the two most inboard W-1 ribs (where the dihedral brace will be installed later.) Notice that the wood grain is vertical for maximum strength. Trial fit each web before gluing, sanding the ends as necessary to make them fit snugly between the ribs at either side. The bottom of the shear webs should be centered on the bottom main wing spar; the top of the shear webs should be centered on the notch for the top main wing spar.

NOTE: The shear web to be installed between the second and third W-1 wing ribs will need to be shortened significantly to fit.


  1. Trial fit the 3/16" x 3/8" x 30" spruce top main wing spar. If any of the shear webs are too tall, they should be trimmed to allow the spar to sit all the way down in the rib notches. When satisfied with the fit, glue the spar in place. Check the inboard W-1 rib again with the Dual Tool to be sure it is still at the correct angle.
  2. Glue the 5/16" sq. x 30" balsa leading edge to the front of the ribs.
  3. Glue the 3/16" sq. x 30" balsa top forward spar in the rib notches.

NOTE: Remove any pins from the structure that are located under the area where the top center sheeting will be installed (in the next step). Otherwise, you may find it difficult to remove your wing from the board later!


Pieces for the top center sheeting should be cut from the 1/16" x 3" x 30" balsa provided in the kit. Again, Sig Bond is recommended for the front and rear edges of the sheeting to make it easier to sand the joints smooth. Also use Sig-Bond on the center W-1 rib. The sheeting can be glued to the ribs on each end using CA.


When the glue has dried, unpin the wing half from the board and install the 3/16" sq. x30" balsa bottom forward spar.
IMPORTANT: If you have been using thin or medium CA glue during construction, now is the time to go back over every joint using medium or thick CA. Don't be stingy here - the integrity of your wing depends upon strong glue joints. Glue each side of each joint. Make certain the shear webs are bonded to the spars AND the wing ribs on each side. Double check the L.E. stick and the T.E. sheeting for complete bonding to the ribs.


Install the bottom center sheeting except in the area between the bottom forward spar and the bottom main wing spar. Cut pieces for the sheeting from the 1/16"x3" balsa that you used earlier.


Cut off and sand the spars. L.E., T.E., and sheeting at both ends of the wing flush with the end ribs.


Sand the leading edge to a round cross-section as shown in the diagram below.

NOTE: The L.E. notches in the ribs were intentionally made slightly oversize so the ribs could be sabded down to the leading edge.



Carefully carve the top of the trailing edge to match the slope of the to T.E. sheeting using an X-Acto #26 whittling blade. Wrap the top of the blade with masking tape (to protect sheeting), leaving about 1/2" exposed at the base. Use the masked portion to guide the blade at the correct angle. Final sand the T.E. so that the back edge of the wing is about 1/4" thick (same as the ailerons).


  1. Glue the die-cut Lite-Ply wingtip brace (WTB) onto the die-cut Lite-Ply wingtip. When dry, sand off the rounded ends of the wingtip brace as shown in the diagram.
  2. Glue the wingtip assembly to the outer end of the wing panel. Notice that the wingtip cants slightly upwards (when viewed from the rear).
  3. Add scraps of balsa to the top and bottom of the rear edge of the wingtip. Carefully sand the balsa to blend into the wing trailing edge.


  1. Sand the top center sheeting smooth. (The bottom center sheeting is sanded in step 22.)
  2. Position the die-cut Lite-Ply rib cutout guide #1 (RCG-1) on the inboard W-1 wing rib. The top of RCG-1 should be flush with the top of the center sheeting, and the notches at the rear should fit around the main wing spars. Trace the notches for the wing hold-down dowel and the canopy hold-down block with a sharp pencil.
  3. Remove the guide, then measure and mark the cutout area on the top center sheeting using the dimension shown in the photo. Using a modeling knife, carefully cut out the outline area. Also cut the slot for the wing-hold down dowel, but do not cut into the leading edge.
  4. Position the die-cut Lite-Ply rib cutout guide #2 (RCG-2) on the inboard W-1 wing rib. The bottom edge of RCG-2 should be flush with the bottom surface of the wing sheeting. Trace around RCG-2.
  5. Remove the guide, then measure and mark the cutout area on the bottom center sheeting as shown in the photo. Cut out the outlined area with a modeling knife. This step accomplishes two things. First it clears an area for the aileron servo; and second, it provides an open area between the main wing spars for the dihedral brace.


Set this wing panel aside, and repeat steps 1 through 13 to build the opposite wing half.


Joining The Wing Panels


  1. Trial fit the two wing halves with the dihedral brace installed between the main wing spars. Be certain that the dihedral brace is not preventing the panels from making solid contact with each other at the center. If necessary, trim or sand the dihedral brace for a snug fit.
  2. Glue the dihedral brace into ONE of the wing panels. Make certain that it is positioned accurately between the main wing spars.
  3. Use slow CA or epoxy (either 5-minute or slow-dry) to join the two wing panels. Apply glue to the end ribs and the exposed edges of the dihedral brace, then carefully slide the other wing panel into place. Before the glue dries, make certain that the leading and trailing edges of each panel are aligned. The dihedral angle of 1 deg. per wing panel will be automatically built in by the dihedral brace. If you want to check the angle, place the wing on a table so that one wing panel sits flat, and the other is raised. The distance from the table to the bottom of the outmost wing rib should be 1"; although a variation of up to 1/4" either way is acceptable. The most important thing is to have a solid joint at the wing center with no gaps.


  1. When dry double check through the servo opening and center sheeting opening on the bottom that the dihedral brace is glued solidly to the main wing spars and the W-1 wing ribs.
  2. Glue the die-cut Lie-Ply backplate (BP) into the aft end of the servo opening. When dry, trim BP flush with the bottom center sheeting.


  1. The aileron torque rods have been pre-bent so that the threaded portion leans rearward slightly inside the fuselage (see the W-1 wing rib cross-section on the plans). That small angle will provide your MID-STAR 40 with a bit of differential movement (more up that down) in the ailerons, which makes for smoother rolling characteristics. Prepare the torque rods for installation by roughening the brass bearings with sandpaper, then wiping them clean.
  2. Locate the 1/4" sq. x2" basswood grooved torque rod blocks and cut a notch in each of them as shown in the photo.
  3. Glue the torque rods into the blocks being very careful not to get any glue in the brass bearings. The outer end of the bearings should be even with the outer end of the blocks.


  1. Glue the torque rod/block assemblies in place on the wing T.E., again being very careful not to get any glue in the bearings.
  2. Notch the balsa trailing edge just forward of the notches in the torque rod blocks to allow full movement of the torque rods.
  3. Sand the top of the basswood blocks to match the slope of the trailing edge sheeting. A small sanding block is handy for this step.


Glue the 1/16"x3/4"x1-1/2" plywood wing hold-down plates to the top of the wing, even with the back of the torque rod blocks.
NOTE: Complete the steps in "Mounting The Wing To The Fuselage" before proceeding.

Finishing The Wing


The canopy hold-down block is a 3/4" long piece of basswood cut from the 3/8" sq. x12" stick supplied in the kit. Glue the block firmly in place, then sand it as necessary to make it flush with the top of the wing.


21. Finish off the bottom center sheeting, again using 1/16" balsa.


Give the wing a final sanding with a long sanding block. Sand just enough to take off any prominent high spots or bumps. Excessive sanding may distort the airfoil shape. Any dents or gouges in the wood can be filled with a lightweight wood filler.


The 1" wide fiberglass tape can be applied to the wing center joint (top and bottom) using one of the following methods.

Remove the tape from the servo cutout area after the glue is dry.

  1. Coat the wing center joint with slow-drying epoxy glue.
  2. Lay the tape on the top of the glue
  3. Holding one end of the tape so it won't slip, "squeegee" the glue through the tape with a small paddle of scrap balsa. Scrape over the tape several times with the paddle to smooth the tape and remove any excess glue.
  4. When dry, sand lightly to remove any rough spots. Try not to sand into the fiberglass tape itself.

  1. Cut the tape to length, then lightly spray one side with a spray adhesive (such as 3M "77").
  2. Position the tape on the wing center joint.
  3. Soak the tape with CA. The spray adhesive simply holds the tape in place - it won't affect the strength of the CA. A second coat of CA will help to fill in the weave of the fiberglass, resulting in a smoother surface. Rub the second coat with your finger (protected with plastic wrap - keep it moving!) to smooth out the glue. Use a fan to keep the CA fumes away from your face.
  4. When dry, sand lightly to remove any rough spots. Try not to sand into the fiberglass tape itself.



The leading edge of each aileron is pre-shaped, but they need to be sanded lightly to a smooth, round contour. Position the ailerons on the back of the wing, leaving a 1/32" gap between the inboard ends of the ailerons and the outboard ends of the torque rod blocks. Mark the locations for the torque rods, then slot and drill the aileron leading edges to receive the torque rod wires.


Trial fit the ailerons to the torque rods. Once they fit, temperarily tape the ailerons in place and sand their outboard ends to match the curve of the wingtips. The outer edge of the ailerons and the scrap balsa on the T.E. of the wingtips should be rounded off so that they blend together perfectly.