Sig Mfg. Co., Inc...401-7 South Front Street....Montezuma, Iowa 50171

Introduction by Bruce Tharpe

People often ask me what the inspiration was for the Wonder. Well, did you ever see the Flying Sub from "Voyage to the Bottom of the Sea"? As a kid, I thought that was just about the coolest flying machine ever conceived. No, the Wonder doesn't look exactly like the Flying Sub, but it had to be somewhere in the back of my mind when I was doodling the first Wonder years ago. I suppose there's a bit of old-time control line combat influence in the design as well.

The design presented here actually evolved from many years of "Wonder-Type" designs, starting with 1/2A versions back in the early 1980s. There have been swept wings, straight wings, single tails, twin tails, and tripple tails. The basic idea has never changed, however. I wanted dirt-simple models that featured a shoulder wing (for easy hand launches) with a large stabilizer butted up against the trailing edge. Many people call them flying wings, but technically, they're not. Actually the extended tail simplifies hooking up the ailerons and elevator, and provides a smoother pitch response than most true flying wings.


The main goal was always to create a smooth-flying, aileron-and-elevator-controlled aerobatic ship. The design in this box is definately the best of the Wonder bunch!

The Sig Wonder kit has been engineered to provide the builder with four optional versions as shown above. The basic structure of each version is identical - the dfifferences are cosmetic. There's no perceptible difference in the flying qualities of one over another, so pick the version that "turns you on" the most.
If you're feeling creative, go ahead and mix fins from one version with ailerons from another and a canopy from a third to create your own, personal version. All of the decals are provided, so you can intermix those as well.
Incidentally, if you get a chance to see a rerun of "Voyage to the Bottom of the Sea", be sure to check it out. Somehow the stories seem dumber than they were so many years ago, but the Flying Sub is still pretty cool.


The recommended engine range for the Wonder is .09 to .19 cu. in. There is a tremendous variety of engines available in this range. Remember that weight is the mortal enemy of small models like this Wonder, and as you go up in power you also wind up increasing the weight. That's not to say than an .09 powered Wonder performs as well as a ,19 powered Wonder, but the difference is probably less than you would expect. Most modellers will be completely satisified with a good .15 in the nose. The real power lovers who enjoy ballistics over aerodynamics will have to install a .19. Anything bigger is not recommended by Sig.

Use only those propellers recommended in the instructions supplied with your engine. And use a muffler! A loud engine may cost you (and possibly your club) the use of your flying field if it annoys a non-flying neighbour. Use the muffler that came with the engine or one of the many after-market mufflers that are available.


The Sig Wonder uses only two flight controls: ailerons and elevator (there is no rudder). Throttle control is optional but is highly recommended. Standard size servos can be used (see plan), but do yourself a favour and buy some mini or micro servos that are compatible with your radio system. The smaller servos will be much easier to install in the Wonder and will save some weight, too. A small, flat 225 maH to 300 maH battery pack is a must. Be certain your radio system frequency is approved for use in R/C model aircraft.


There are 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: Fast cyanoacrylate adhesives (abbreviated as CA) such as Sig CA, easy to use water-based wood glues such as Sig-Bond (yellow) and Sig Super-Weld (white), super strong (but heavier) two-part epoxy glues such as Sig Kwik-Set (5 minute cure) and Sig Epoxy (3 hour cure), and 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 experience with previous models. CA is recommended as our first choice because of it's ability to penetrate an already assembled joint. In other words, parts can 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 these instructions.

Sig CA, like mose brands of cyanoacrylates, come in three viscosities- thin, medium, and thick. Odorless CA is generally more expensive, but it is ideal for people who can't tolerate the fumes of normal CA. An accellerator spray and debonder are also available and are described below.
  • Sig CA Thin- Watery consistency, thin CA should only be used when the two parts to be joined are in perfect contact with zero gap. Capilliary 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 Plus- Our medium thickness CA is excellent for almost any step during construction. The extra thickness allows the glue to fill small gaps, but it does dry a little slower than a thin CA.
  • Sig CA Slow- This thickest formula is good for filling 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. 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!


CAUTION: 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.


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 finish 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 or around a hardwood dowel for working in tight places.


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. Crocked 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 their correct position.

When pinning or 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 the die-cut parts in the sheets until needed for construction. Then remove pieces from the sheets carefully. If difficulty is encounted, do not force the part from the sheet. Use a modeling knife to cut it free.

The die-cut balsa and plywood can be identified using the plans and the "Key to Die-Cut Parts" below. 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". Sort the different sizes of sticks and sheets into individual piles to avoid confusion during building.



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. 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 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" an do a step or two or three, then back to "Wing Construction" and so forth. You will 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.

Die-Cut Balsa
41/16"x3"x18" Wing Ribs 23/32"x4"x18" Fuselage Side, Fuselage Doubler 11/8"x4"x18" fins, Wing Block Pads (WBP)
Printed Balsa
11/4"x2"x12" Canopy, Wing Dowel Supports (WDS)
Sheet Balsa
21/16"x1"x36" Trailing Edge Sheeting 11/16"x3"x18" Wing Center Sheeting 21/16"x3"x36" Leading Edge Sheeting 11/8"x3"x18" Fuselage Bottom
21/8"x4"x10" Sheets for Optional Fins 23/16"x4"x12" Stabilizer and Elevator 21/4"x3"x3" Fuselage Top, Cowl Bottom
Stick Balsa
31/16"x1/4"x36" Capstrips 11/4"x1/4"x36" Leading Edge 51/4" Traingle x12" Corner Braces, Skid Sides 11/2" Triangle x6" Cowl Filler
Block Balsa
21"x1-1/2"x9" Wingtips
Special Cut Balsa
13/16"x3/8"x36" Tapered Trailing Edge 23/16"x1-1/4"x12" Tapered Ailerons 43/16"x1"x3" Cowl Sides
Pre-Cut Plywood
13/32"x2-3/4"x6" Birch Ply F-1, Aileron Servo Mounts (ASM) 11/8"x2-3/4"x9" Lite-Ply Formers, HP, Hatch Lip, Spinner Ring
Sawn Plywood
11/16"x7/8"x2-1/2" Birch Ply Wing Hold-Down Plate
11/8"x1/8"x9" Spruce Fin Stiffener 21/8"x1/4"x36" Spruce Wing Spars 11/8"x5/16"x12" Spruce Skid 23/16" dia. x1-1/2" Birch Wing Dowels
21/4"x1/2"x1-1/2" Basswood Wing Hold-Down Blocks
Formed Wire Parts
14-40x8" L.H. Aileron Torque Rod (with brass bearing) 14-40x8" R.H. Aileron Torque Rod (with brass bearing)
14"x20" Decal DKM-266A (for Standard Version) 14"x20" Decal DKM-266B (for Russian Version) 14"x20" Decal DKM-266C (for Angel Version) 14"x20" Decal DKM-266D (for Patriot Version)
138"x50" Full-Size Printed Plan 120 pg. Photo Illustrated Instruction Book
2Small Glass-Filled Engine Mounts 2#2x3/8" Flat Head Wood Screws (for hatch) 2#2x1/2" Sheet Metal Screws (for control horn) 46-32x5/8" Socket Head Mounting Blocks (for engine mounts)
210-32x1" Nylon Wing Bolts 46-32 Blind Nuts (for engine mounts) 12-56 Solder Link (for throttle) 32-56 Nylon RC Links (2/aileron, 1/elevator)
32-56x10" Threaded Rods (2/aileron, 1/elevator) 24-40 Nylon Aileron Connectors 1Nylon Control Horn (for elevator) 1130" o.d.x12" Nylon Tubing (for throttle pushrod)
11/16" dia.x12" Steel Cable (for throttle pushrod) 73/4"x1" Easy Hinges 1Pushrod Connector Package



The Wonder wing is designed to be built in one piece, flat on the building board (no dihedral or washout). Pin or tape the wing plan to your building board and protect the plan by covering it with wax paper or plastic wrap.


  1. Pin the 1/8"x1/4"x36" spruce lower wing spar over the plans. Instead of pushing pins right through the spruce (which could cause it to split), cross two pins over the spar to hold it in place.
  2. Glue the 16 die-cut balsa wing ribs to the lower wing spar. Each wing rib should be vertical and the alignment tab at the trailing edge should be pinned firmly to the building board.


  1. Glue the 1/8"x1/4"x36" spruce upper wing spar to the wing ribs.
  2. Find the 3/16"x3/8"x36" special-cut balsa trailing edge. By looking at its ends you will see that it is not symmetrical. Rather, it is a 3/16"x3/8" balsa stick that has been tapered on its top surface from 3/16" at the front to 1/6" at the rear. For the best fit, make sure the trailing edge is positioned properly in the wing rib notches as shown in the diagram. Glue the trailing edge to the wing ribs being careful not to glue the trailing edge to the alignment tabs.
  3. Add the 1/4"sq.x36" balsa leading edge to the front of the ribs.


The leading edge sheeting must be cut to its correct 2-3/4" width from the 1/16"x3"x36" sheets provided in the kit. Use a long straightedge and a sharp modelling knife to trim the sheets. To help make the sheeting fit against the leading edge, hold the knife at a 15 or 20 degree angle while cutting the front edge of the sheeting, as shown in the photo.


Glue the leading edge sheeting to the leading edge using a bottle of thin CA with a long applicator tube. Apply slow CA to the tops of the wing ribs and the upper spar, then push the sheeting into place with your hands. You may have to use accelerator spray on small sections at a time until the sheeting is completely glued in place.

NOTE: Harder sheeting may need to be wetted before bending it into place, to prevent cracking. Warm water sponged onto the outer surface will cause the sheeting to swell, allowing it to conform easily to the rib contour.

...we don't just give you 2-3/4" sheeting in the kit?
Internal stresses can cause a sheet of balsa to bow, even when cut from a perfectly straight plank. Experienced modelers know that the only way to ensure a straight sheet of balsa is to cut the edges themselves, just before gluing it in place on the model. Trimming the edges is an easy step that will help you build a true wing.


  1. Add the 1/16"x1"x36" balsa trailing edge sheeting.
  2. Sheet the upper center section of the wing using pieces cut from the 1/16"x3"x18" balsa provided in the kit. Sig-Bond (yellow wood glue) is recommended for the edges of the sheeting because it's easier to sand than CA.
  3. Glue the 1/16"x1/4" balsa capstrips to the upper edge of the remaining wing ribs and allow to dry.


6. Unpin the wing from the building board. Carefully cut away the alignment tabs on all of the wing ribs.


  1. Use a jigsaw or a sharp modeling knife to cut the two wing dowel supports (WDS) from the 1/4" printed balsa sheet. Saw just outside the lines, then true up the edges with a sanding block, leaving the complete black line on the parts.
  2. Glue the wing dowel supports to the two center ribs as shown on the plans.


  1. Turn the wing over and pin it to your building board. The wing is now rightside up. Mark the top of the wing for identification in latter steps. Use a piece of scrap stick wood to support the trailing edge. It's very important to keep the support stick straight and aligned with the trailing edge - you don't want to build in any warps now. Pin the support stick to the board and pin the wing to the support stick to hold everything firmly in place.
  2. Glue on the bottom leading edge sheeting, the bottom trailing edge sheeting, and the bottom capstrips. Hold off on the bottom center sheeting; it will be installed later.


When dry, unpin the wing from the building board. If you have been using thin or medium CA glue during construction, now is the time to go back over every joint with 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. A long aplicator tube will help you reach inside the leading edge sheeting.


Now you can glue on the 1/16" balsa bottom center sheeting.


  1. Carve and sand the wing leading edge to shape. For best stall characteristics, you want a nicely rounded leading edge as shown on the plans. Use a long sanding block to make certain the curvature is consistent along the entire length of the wing.
  2. If necessary, touch up the trailing edge with a sanding block so that it's flat and straight.
  3. Cut off and sand the spars, leading edge, trailing edge and sheeting at both ends of the wing flush with the end ribs
  4. Give the wing a final sanding over it's entire surface with a long sanding block. Sand just enough to remove any prominent high spots or bumps. Be careful! Excessive sanding may disturb the airfoil shape.


Decide now which type of wingtip you plan to use, then cut or trace the top view of the wingtip from the plan. Transfer the shape of the wingtip to the tops of the 1"x1-1/2"x9" balsa block wingtips using the paper outline as a guide. Rough cut the blocks to shape with a bandsaw or a jigsaw.


  1. Glue the wingtips to the end ribs. If one of the blocks happens to be heavier than the other, glue the heavy one to the left end of the wing to help offset the weight of the engine's muffler, which is generally on the right side. Sig-Bond is again recommended for easy sanding.
  2. When dry, carve and sand the wingtips to shape. If you are building the "Standard" Wonder, see the separate instructions for "Carving Vortex Wingtips". If you are building another version, start by carving and sanding the blocks to match the airfoil contour, then round off the corners.
  3. Reinforce the thin trailing edge of each wingtip by soaking it with several drops of thin CA.


14. Locate the 1/16"x7/8"x2-1/2" plywood wing hold-down plate, then round off the top edges and the corners with a sanding block. Glue the wing hold-down plate to the top of the wing so that it's centered left to right and overhangs the trailing edge 3/16".

Carving Vortex Wingtips

The down-turned vortex wingtips used on the Standard version of the Wonder were chosen more for their looks than any kind of aerodynamic reason.
Theoretically this type of wingtip is very efficient, but on a model of this size it really makes little difference.
They are easier to carve and sand than they appear, so give 'em a try!

1. Cut out the top view of the wing tips (see step 12 above). Draw a line on the inside surface of each tip, 11/16" from the bottom.

2. Glue the wingtip to the end rib so that it's flush with the bottom of the airfoil and the drawn line passes through the exact center of the trailing edge. When dry, us the WT wingtip plate (cut from plans) to mark the shape of the trailing edge on each wingtip.
3. Carve and sand the wingtip blocks to match the contour of the entire upper surface and back to the spar on the lower surface.

4. Rough carve the concave portion of the tips using an X-Acto #162 router blade.

5. Finish sand the concave portion with a large dowel wrapped with 80-grit sandpaper.

6. The rest of the block can now be carved and sanded pretty much like a normal, rounded wingtip. Be sure to strengthen the trailing edge area of each wingtip by soaking then with thin CA. Smooth things up with a hand-held piece of 150-grit sandpaper.

...there's no dihedral brace or sheer webs in the wing?

All of the spars and sheeting in the Wonder wing run the full span of the wing, from tip to tip. Since there is no center wing joint, there's no need for a dihedral brace or reinforcing fiberglass tape. The center sheeting is more than adequate to absorb the aerodynamic loads at the center of the wing.
None of the Wonder prototypes ever used, or needed, shear webbing. The low-aspect-ratio, 15%-thick wing simply doesn't need the extra strength or weight of shear webs, and you don't need the extra work of installing them!


  1. Draw a line on the trailing edge at the exact center of the wing, then two more lines spaced 1/2" on either side of the center. The second two lines indicate where to position the inner end of the torque rod brass bearings, which should now be glued in place. Make certain the torque rod assemblies are centered vertically on the wing trailing edge and be careful not to get any glue in the bearings.
  2. When dry, fill the small gaps above and below the torque rods with more glue or balsa filler and sand it smooth.
  3. Cut clearance notches in the wing trailing edge for the inner end of the torque rods.


  1. Two pieces of 3/16"x1-1/4"x12" tapered balsa are provided for making the ailerons. Choose an aileron pattern, cut it from the plans, trace the outline onto both pieces of tapered balsa, then cut the ailerons to shape.
  2. Carefully block sand the top and bottom surface of each aileron equally so that the leading edge remains 3/16" thick and the trailing edge is a constant 1/16" or less. You'll need to steepen the angle of the sanding block as you approach the aileron tip to make the trailing edge a constant thickness. This sounds tricky, but it won't take more than a few passes of an 80-grit sanding block.


  1. Draw a hinge line centered on the leading edge of each aileron. Use a sanding block to bevel the front of the ailerons using the hinge line as a guide.
  2. Position the ailerons on the back of the wing, leaving a 1/32" gap between the ends of the aileron and the wingtips. Mark the locations for the torque rods, then slot and drill the ailerons to receive the torque rod wires.


Trial fit the ailerons to the torque rods. Once they fit, temporarily tape the ailerons in place and sand the wingtips and ailerons in place and sand the wingtips and ailerons as necessary to blend smoothly together.


Basic Fuselage Assembly


  1. Glue together the two die-cut 3/32" plywood F-1 pieces using Kwik-Set epoxy or slow CA. Use a heavy weight of some kind to hold the two pieces perfectly flat while drying.
  2. Mark the vertical centerline and thrust line on the F-1 assembly using the cross-section on the plan as a guide.
  3. Determine the spacing that will be necessary between the two glass-filled engine mounts to fit your engine, then position the mounts on F-1 accordingly. Mark the location of the four mounting holes and drill them out with a 3/16" drill bit.


Lightly hammer four 6-32 blind nuts into the back of F-1. Bolt the engine mounts to the front of F-1, using 6-32x5/8" socket-head bolts to align the blind nuts (see note below). Apply medium or slow CA around the edges of the blind nuts to hold them in place.
NOTE: The shank of the 6-32 blind nuts may extend too far through F-1 and interfere with the back of the engine mounts. To avoid any interference, drill a 3/16" dia. relief partially through the back of the mounts at each hole.


  1. Position your engine on the mounts so that the rear face of the spinner backplate is between 2-3/4" and 3" from F-1. Mark through the engine mounting holes with a pencil, then remove the mounts from F-1.
  2. Drill and tap the mounts for the engine bolts (not included).


22. Re-install the engine mounts, bolt the engine in place, then install the pushrod connector (included in your kit) on your engine's carburettor control arm. Locate and mark the best spot on the firewall for the throttle pushrod to exit and line up with the pushrod connector. Now you can remove the engine and mounts, and drill at the mark with a 9/64" drill bit.


  1. Hold the two 3/32" die-cut balsa fuselage sides together and sand the edges lightly until they are a perfect match.
  2. Mark the positions of the three formers on the fuselage-sides. Marking the right-hand fuselage side is easy. Place it over the "Typical Radio and Engine Installation" drawing on the plan and use the small guidelines to mark the balsa. Now you can use the right-hand fuselage side to transfer identical markings to the inner surface of the left-hand fuselage sides.


  1. Glue the 3/32" die-cut balsa fuselage doublers to the fuselage sides.
  2. Glue a piece of 1/4" balsa triangle along the bottom of each fuselage side. Notice that the aft end of the triangle piece should end at the rear face of former F-4.
  3. Tack glue the 1/8" die-cut lite-ply formers F-3 and F-4 in place on one of the fuselage sides using a triangle to make certain they are square with the side.


While holding the second fuselage side in place on the formers, check the alignment of the fuselage over the top view on the plan. When satisfied, glue both fuselage sides firmly to F-3 and F-4.


  1. Tape former F-1 in place on the front of the fuselage, and again check the alignment over the top view on the plans. Notice that the correct amount of downthrust (4 deg.) is built in automatically by lining up the front face of F-1 with the front edge of the fuselage sides. There should be no side thrust when viewed from above. When satisfied, glue F-1 to the fuselage sides from the front and back with thin CA.
  2. Trim the 1/4" triangle stock flush with the front of F-1.
  3. Cut two braces for F-1 from 1/4" balsa triangle stock and notch them as necessary to clear the blind nuts on the back of F-1. Apply slow CA to the braces and press them firmly in place.
  4. It may be necessary to redrill the hole for the throttle pushrod through a triangle brace that was installed. Use a 9/64" drill bit.


Carefully position a straightedge so that it's lined up with the rear face of F-4 on the outside of the fuselage. Use a sharp knife to cut through about half the thickness of each fuselage side. Now the back end of the fuselage can be literally "cracked" into position. If it happens to snap off completely, that's okay; it can be re-attached in the next step.


Firmly pin the fuselage upside down over the top view on the plan so that it can't move. Now you can hit the cracked joint on each side with a bit of CA to hold the rear fuselage in alignment.


29. Cut the 1/8"x3"x18" balsa fuselage bottom into four pieces as shown in the diagram. With the fuselage still pinned to the plan, glue on the bottom pieces in the order shown. Notice the grain direction of each piece, and be sure to just tack glue to the hatch - it will be removed later.

...there's a hatch way be there?
If you've looked ahead in these instructions or at the plans, you have already seen that a servo will probably have to be located in this area and possibly the battery and switch too.


Remove the fuselage from the building board and fill the scored areas on the fuselage sides with medium or slow CA. Trim and sand all of the bottom pieces flush with the fuselage sides. Use a long sanding block to round off the bottom corners of the fuselage aft of F-4.


  1. Remove the hatch and glue in two die-cut 1/8" lite-ply hatch plates (HP).
  2. Slide the die-cut 1/8" lite-ply hatch lip (HL) into place on the fuselage bottom. Put a drop or two of slow CA on the exposed part of the hatch lip, then put the balsa hatch back into place. The idea here is to glue the hatch lip only to the balsa hatch.


  1. With the hatch still in place, use the plans as a guide to carefully mark the location of the two hold-down screws. Drill completely through the hatch and the hatch plates at the marks with a 1/16" drill bit.
  2. Remove the hatch, then redrill the hatch holes with a 3/32" drill bit. The holes can be countersunk for the flat-head wood screws using a sharp 1/4" drill bit. Strengthen the countersunk area with a few drops of thin CA.
  3. Re-glue the hatch lip firmly to the hatch.


  1. Carefully drill at the two dimples in F-2 with a 1/8" drill bit, followed by a 3/16" drill bit. Use a chunk of hardwood behind the former to keep the wood from splintering as you drill through.
  2. Glue F-2 into position as shown on the plans.

Mounting the Wing to the Fuselage

NOTE: The wing must be finished through step 14 before proceeding.


Position the wing on the fuselage and check its alignment as shown in the diagram. When staisfied, firmly tape and pin the wing in place.


Drill two holes into the wing for the wing dowels. The easiest way to do this is to run a long 3/16" drill bit along the top edge of F-1, through the holes in F-2, and into the wing. If you don't have a long drill bit, you can turn a shorter one by hand to get the holes started then finish off the holes after removing the wing.


  1. Remove the wing and insert the two 3/16"dia.x1-1/2" wing dowels into F-2 from the aft side so that they extend in front of F-2 about 1/16". Slide the wing into place to check that it seats properly on the fuselage. If not, slowly enlarge the holes in the wing until it does seat properly. Again remove the wing, leaving the dowels in place in F-2.
  2. Apply several drops of Kwik-Set epoxy to the holes in the wing. Slide the wing back into its proper position on the fuselage until the epoxy is dry. Be careful not to glue the wing dowels to F-2. When dry, remove the wing and fill any gaps around the dowels with another application glue.


  1. Glue the two 1/4"x1/2"x1-1/2" basswood wing hold-down blocks into the notches in the fuselage doublers.
  2. Add the die-cut 1/8" balsa wing block pads (WBP) to the top of the basswood blocks.
  3. Carefully sand the balsa wing block pads to match the contour of the wing saddle area.


  1. Fit the wing in place on the fuselage and check its alignment one last time. When you are satisfied that it's aligned correctly, tape or pin the wing so that it can't move.
  2. Carefully mark the drill locations for the wing bolts using the plan as a guide. Drill through the wing and the wing hold-down blocks at the same time with a 5/32"dia. drill bit. Keep the drill perpendicular to the top surface of the wing so the heads of the nylon bolts will seat flush against the plywood plate.


  1. Remove the wing and tap the wing hold-down blocks with a 10-32 tap. You can apply a few drops of thin CA to the holes to strengthen the threads.
  2. Redrill the holes in the wing with a 3/16" drill bit to pass the nylon wing bolts.

Finishing The Fuselage


Now is a good time to prepare your fuel tank for installation. The 4oz slant tank from Sullivan (not included) fits well and should sit as high in the fuselage as possible. The fuel lines from this tank exit the fuselage at the joint between F-1 and the balsa top. You can prepare F-1 for the fuel lines by sanding or filing semi-circles into the top edge. If you plan on using a different type of fuel tank, drill holes in F-1 as necessary for the routing of the lines.


  1. The 1/4"x3"x3" balsa fuselage top can be shaped at the aft end to match the contour of the wing leading edge. Glue the fuselage top in place so that the aft end fits snugly against the wing.
  2. Trim and sand the fuselage top flush with the sides and F-1, then round off the side corners with a sanding block.
  3. Finish drilling the fuel line holes through the balsa.



  1. The balsa cowl is made of several parts that are basically built up around the engine. Install the engine mounts and your engine with the spinner that you intend to use. Cover any openings in the engine (carb, exhaust) with tape to protect it from dust.
  2. Begin the cowl construction by gluing the 1/4"x3"x3" balsa cowl bottom to the front of F-1 so that it's flush with the fuselage bottom. Sig-Bond is recommended for all of the cowl parts because it will be easier to sand later.
  3. Add two of the 3/16" pre-cut balsa cowl sides leaving about 1/16" between them and the engine mounts. Depending on the width of your engine, the cowl sides may or may not blend into the spinner backplate. If not, cut off the front end of the two remaining cowl sides and glue them in front of the engine mounts.


Remove the engine and the mounts, then fill the bottom inside corners of the cowling with pieces of 1/2" or 1/4" balsa triangular stock. Taper the triangular stock towards the rear so it doesn't interfere with the engine mounts.


Bolt the engine back in place and carefully sand the front edge of the cowl with a narrow sanding stick. Sand until the gap between the cowl and the spinner backplate is about 5/32".

...the Wonder cowl is made of balsa instead of plastic?
Answer: Flexibility. The Wonder uses lots of different engines which all have different lengths, which all require something of a custom cowl. Besides, a balsa cowl allows you to cover the fuselage right up to the spinner ring with no seams. Actually, you can leave the cowl off with no adverse effects on flight performance - it just won't look as good!


  1. Glue the die-cut 1/8" lite-ply spinner ring to the front of the cowl, making certain it is aligned with the spinner backplate. Notice that the spinner ring is cut oversize to allow for a bit of sanding.
  2. Prepare the spinner backplate for the cowl sanding process by protecting the edge with tape.
  3. Carve and sand the cowl to blend in smoothly with the spinner at the front and the fuselage at the rear. Now's a good time to round off the bottom corners of the fuselage (forward of F-4) as well. Do the rough sanding with 80-grit sandpaper, then smooth it down with some 150-grit.


The landing skid is constructed by gluing two 1/2" lengths of 1/4" balsa triangle stock to the sides of the 1/8"x5/16"x12" spruce skid. Sand the spruce round on the bottom and shape the ends as shown on the plans.

...there's no landing gear on this design?
Answer: Well, let's look at the pros and cons of going with a skid instead of wheels on the Wonder. On the positive side, without landing gear the Wonder is lighter, simpler, costs less, flies faster, performs better, and simply looks sleeker. The negative is you can't land on concrete (technically you can, but it's certainly not recommended!). Even if it had wheels, the Wonder would still require a hand launch because there's no ground steering without a rudder. So find a field and have at it!




  1. Make the stabilizer by edge gluing two 3/16"x4"x12" balsa sheets (Sig-Bond is recommended). When dry, block sand the joint until it's smooth.
  2. The stabilizer must be accurately cut to it's proper width of 11-1/4". Start by drawing a centerline and two edge lines, each spaced 5-5/8" from the centerline. If you don't have an accurate 90 deg. square, you can use the plans as a guide. Use a sharp knife to make the cuts on each edge.


Cut the elevator from the stabilizer using the elevator shape of your choice. Bevel the leading edge of the elevator, sand the trailing edge round, and trim each tip about 1/16" to clear the fins.


If you are building the Russian, the Angel, or the Patriot, you need to hand cut the fins from the two sheets of 1/8"x4"x10" balsa. Edge glue the sheets, then cut the fins out using the pattern of your choice. Add the 1/8" sq. spruce stiffeners, sand the sides smooth, and round all the edges.


  1. To make the two fins for the Standard version, simply glue together the die-cut 1/8" balsa fin pieces together as shown on the plan.
  2. Add a piece of 1/8" sq. spruce to the bottom of each fin to act as a stiffener. When dry, sand the fins smooth on each side and round all of the edges.