The Kougar was designed as an advanced aileron trainer for fliers who have had some flying time on an intermediate trainer such as the Sig Komander or Sig Kavalier. While it is very maneuverable and can do difficult FAI pattern maneuvers and even accomplish lomcevaks, the model has been carefully tailored to handle easily and not be touchy in the hands of novice fliers. A fully symmetrical wing section provides good inverted and outside stunting characteristics.
For use as a trainer, a .40 cu. in. engine is recommended. A .45 gives faster performance and would be good for pattern competition. One of the prototype models was powered by a .49 and the model is strong enough to handle this amount of power though this engine size is advisable only for advanced contest or sport fliers who wish to achieve high flying speed and steep angles of climb.

A Note About Balsa Wood
We do our best to put as good a grade of balsa in our kits as the supply situation permits. The world-wide increase in demand for balsa has made it impossible to obtain as high an average quality as used to be the case and this situation is getting worse.
Every piece of balsa supplied cannot be 100% perfect or kit prices would have to be greatly increased. Mineral stains or small knots do not seriously affect wood strength. Even with the very best grades of balsa, there is a natural tendency for some sticks or sheets to immediately bow upon being cut off from a perfectly square block because of builtin stresses. In most cases, these can be bowed back into alignment during building. True up the edges of bowed sheet by trimming, using a metal straight edge to cut against. Planking sheets, as used on the wing, need not be perfectly flat since they must be curved into place anyway during construction. The gluing of the plywood doublers and stringers to the fuselage sides while they are pinned to a flat surface should flatten out any warps in the side sheets.

Recommended Glues

The framework should be glued with Sig-Bond resin type glue. Areas subjected to unusual strain, exposed to fuel or oil, or including metal pieces, should be epoxied with Sig Epoxy Glue or Sig Kwik-Set 5 minute type epoxy. Some specific pieces have other recommendations. You will find these in the directions concerning the part.

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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. We occasionally get suggestions that our instruction books should be in exact step-by-step building sequence. But this would result in many sentences starting "While the glue is drying on the fuselage, move to the wing etc." and a lot of jumping back and forth between assemblies with no consistent pictorial progression.
Also, a preselected building sequence by our choice might not suit your workshop space and time allotments. Therefore, we feel the present system of covering main assemblies in a unit works out best for the majority of kit builders. So keep in mind that the numbering sequence used in these instructions were chosen as the best way of explaining the building of each major assembly and is not in tended to be followed in exact one-two-three fashion. Start on the wing at No.1 and after performing a step or two, flip over to the next main heading of "FUSELAGE CONSTRUCTION" and do a step or two there, then over to "TAIL ASSEMBLY" and so forth. You will, of course, arrive at points where you can go no farther until another component is available. For example, you need a completed wing before the fuselage can be completed. The way to understand these relationships is to read the instructions completely and study the photos before beginning to work.
Any reference to right or left refers to right or left as if seated in the cockpit.

You Can't Get Along Without a Good Sanding Block

An indispensable tool for proper construction is a large sanding block sized to take a full sheet of sandpaper. Use several wood screws along one edge to hold the sheet in place. Use the block to bring all parts and sticks to final, exact fit. We recommend 80-grit garnet paper for use on the block during general construction. You can switch to 100-grit, followed by 220 silicone paper for final finish 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 tight-places. We have an especially handy extra long sanding block made from a 40 inch piece of aluminum channel with sandpaper glued to it that is particularly useful for jobs like truing up the leading edge and trailing edge of the wing core.

Cutting Out Printed Parts

A jig saw is best for this job. Cut just outside the lines, leaving all of the black line on the part. When fitting the part into place in the model, use the sanding block to bring the edges to an exact fit. If a modeling knife is used to cut out the parts, don't cut too close to the lines -- leave some extra wood outside the line. True up and finish the edge with the sanding block.

Some Rules To Follow

Cut all long pieces of balsa first, followed by medium lengths before cutting up any full-length strips into short pieces. Remove die-cut 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. Leave parts in the sheets until needed in construction.
A piece of Celotex-type wallboard makes a handy building board, into which pins can easily be pushed. Lay the building board on a table with a flat and untwisted top. Pins can be pushed through all pieces in the kit without any lasting damage. The holes will fill up during sanding and doping. Be careful where you use a ball point pen for making marks. If not sanded off, these marks will bleed through many coats of dope and show on the finished model.

WING CONSTRUCTION

1.

True up the edges of the fourteen 1/16"x3"x24" sheets of wing planking wood by trimming where necessary, using a metal straightedge as a guide. Use the large sanding block for final touch up of the edges.

2.

Tape seven sheets tightly together with strips of masking tape.

3.

Turn over and open up the joints, with the masking tape serving as a hinge. Put a bead of Sig Bond in each of the seams and close the joint.

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4. Lay the sheets flat. Scrape off the excess glue with a squeegee made from a balsa scrap. Finish glue cleanup with a damp rag. Weight down the sheets on a flat surface and allow to dry thoroughly.

5.

Sand the wing skins smooth with the sanding block.

6.

Cut one 7-sheet piece diagonally in two, with untaped side up, as shown by the dotted line marked "A" in the diagram below.
Cut the other 7-piece diagonally in two, with the untaped side up, in the opposite direction as shown by the dotted line marked "B". This provides 4 wing skins with the untaped, rougher glue seam on the outside surface of the wing. The smoother, taped side should be used against the foam wing for best adhesion of the skin to the foam. The rougher, outer glue seams can be sanded down partially with a sanding block before application of the skins and completed during final sanding of the skin on the wing.


7.

Sand any irregularities or cutting wire marks from the cores with the large sanding block.

8.

Hold the cores together at the center joint. If there is any mismatch in the airfoil shape, sand as required to make them fit smoothly together. Done this way, little matching will be required after planking.


THE SECRET OF A PERFECT FOAM WING
It's a simple matter of a FLAT table. Most tables are not flat, as can be seen by checking them with a good straightedge. If a foam core is covered on a bowed or twisted surface, then the wing will be bowed or twisted. And a table that checks out true but is flexible and will yield as you press on it will also spoil a wing. The ideal working surface is a sheet of plate glass. Or, it is possible to find a thick piece of plywood that is perfectly true.
Like balsa blocks, foam blocks sometimes have built-in internal stresses and the core bows slightly when cut out of the block. Skinning on a flat surface, in the sequence shown in the pictures, will correct minor bows.
Incidently, the washout in the Kougar wing is cut right into the foam core. The tip section is higher at the trailing edge compared to the center section trailing edge. The washout will take care of itself. No blocking up or other steps are required of the builder. Proceed with wing construction as if it were a standard wing.

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9.
  1. Sig Core Bond is recommended for applying the wing skins. This is a special adhesive, light and strong, that is ideal for use with foam. As experienced modelers have found, many foam wing glues contain very volatile solvents. When using these glues, if the wing skin is put on before the glue is absolutely dry, the still evaporating solvents are trapped in the assembly and quickly attack and destroy part of the foam core, ruining the wing. Sig Core Bond is much less likely to do this type of damage and is more forgiving of errors in assembly technique. So it is ideal for beginners at foam wing sheeting in addition to being a superior adhesive. Follow the directions on the can for a perfect wing sheeting job.
  2. Shorten the bristles of an ordinary 2" house paint brush to about 1-1/2". This stiffens the brush and makes it easier to spread the glue evenly.
  3. Apply a thin, even, full coverage coat of Core Bond to both sides of the foam cores. Avoid heavy spots. These are inclined to skin over, leaving wet spots underneath that could cause trouble after the wings are skinned. Stand the cores on end to dry. (The cores should be coated first because they take slightly longer to dry than the wing skins.)
  4. Coat the wing skins with Core Bond.
  5. Allow the cores and skins to dry completely. This generally takes about one hour. In conditions of high humidity it may take somewhat longer. It is best to join the parts soon after they are dry, since if they are allowed to lay around for a long period, they will not stick together as well as if joined soon after they are dry. In case of doubt as to whether the glue is dry or not, it is best to let it dry a little longer rather than join the parts while still partially wet.
CAUTION
Use only Sig Core Bond, Sig Kwik-Set, Sig Epoxy Glue or Sig-Bond Glue on the foam wing cores.

Model cement such as Sig-Ment, dope and fiberglass resin will attack and destroy foam. If you use any product other than those listed, test them on a scrap of foam before use on the wing.


10. Hold the trailing edge of the foam core in position just above the wing skin and lower the edge only onto the skin. Make sure it is properly aligned before contact is made because it cannot be removed and re-positioned after contact is made. Press down along the trailing edge to make sure it is making good contact and is flat against the table.

11.

Roll the core down onto the sheet with a rocking motion.

12.

Continue rolling the core onto the sheet until the leading edge is attached.


13.

Turn the core over and firmly rub down the wing skin sheeting with the flat of your hands to insure that the balsa skin is firmly attached to the core.

14.

Remove the waste wood around the edges by rough trimming. Save fine final trim for later.

15.

Repeat Step 10 on the opposite side of the cores.

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16. Repeat Step 11.

17.

Repeat Steps 12 and 13.

18.

Trim and sand the edges of the sheeted foam cores. While the regular sanding block can be used, note how useful an extra long block is for this purpose. (The one shown is made from a section of aluminum channel extrusion - with sandpaper glued on using sanding disc adhesive. This handy specialized glue is available at hardware stores and lumber yards.

19.

Glue on the 1/4"x3/4" leading edge, holding it in place with pins and strips of masking tape. Sig Bond glue is recommended.

20.

  1. Glue on the 1/4"x1/2" trailing edge in the same manner as the leading edge.
  2. Allow to dry.
21. Carve the leading and trailing edge roughly to contour.


22.

Sand to exact shape with the sanding block. A pencil line drawn down the center of the leading edge from root to tip will help get the shape true all along the wing.

23.

  1. Epoxy glue the anchor block to the grooved block.
  2. Cut out the balsa sheeting above the landing gear block slots in the foam core. The slots may be located by pressing on the sheeting or by use of the waste block from the foam core. Cut the holes in the sheeting out undersize at first so that the opening can be trimmed down carefully for an exact fit around the landing gear blocks.
  3. Excavate the foam out of the pre-cut cavity to accomodate the anchor block. The best way to cut foam is with a brand new, sharp modeling knife whittling blade. Or you can heat an old blade in a flame and hot cut the hole.
  4. Epoxy glue the landing gear blocks into the wing. Should there be any areas in the cavities which do not fit snugly against the blocks, fill these voids with a mixture of epoxy glue and scrap foam which has been crumbled into bits.



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24. Position the landing gear and drill a 5/32" diameter hole into the gear block and anchor block.
CAREFUL!
It is easy to slip and go clear through the wing.

Trim the edge of the hole so that the radius of the wire at the bend will fit down into it. The gear should fit into the block snugly, but not so tightly that it will jam in the block. You may want to remove it later for straightening after a hard landing. Place a nylon landing gear strap held on by No. 2 screws across the gear at each end to retain the gear in the groove.

25.

The angle already cut into the ends of the foam wing halves sets an approximately correct dihedral angle. To check it, set up the wing halves as shown in the drawing below, with each wing tip blocked up 1". Sand the wing ends (Photo 25) as required to make the center joint fit correctly together. Glue the halves together with Sig Epoxy Glue or Sig Kwik-Set Glue. Use plenty of glue where the balsa sheeting meets so that the joint between the two halves is completely filled. Be certain that the leading and trailing edges are lined up exactly so that no twist between the two halves is built into the wing. Mark center lines on the ends of each panel before joining and match the lines when joining. If you have the wing sitting on a true, flat surface, a further check on twist can be made by putting center marks on the tips also and measuring from them to the table as a second reference.




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Notes On Loops
A true wing will perform perfect loops. A twisted wing will loop obliquely. One wing half being heavier than the other may also affect loop tracking. Side mounted motor may make one side of the model heavier than the other. Put weight in opposite wing tip until balanced. Should your model snap roll out of the top of a loop, it may snap in the direction of any twist in the wing, but the real reason for it snapping is because of a stall. This is probably due to one or more of the following:
  • Airspeed too low.
  • C.G. too far back.
  • Pilot pulls too much elevator, a mistake aggravated by excessive elevator travel which makes the elevator more sensitive. Reduce travel of elevator and use more care in transmitter stick movement.
  • Not enough power, too high a wing loading for the available power or both.

26.

Cut out the wing tip blocks, using the pattern, at the end of these instructions, for the top view and the end of the sheeted wing for the side view. Glue the tip block on with Sig Bond, holding it in place with masking tape and/or pins. Carve and sand to shape. (If you wish to save weight by hollowing the tip, only tack glue it in place so that it can be removed for hollowing after it has been shaped. Use an X-acto "Y" router blade for hollowing.
27. Cut out the inset holes in the wing sheeting for the plywood tabs called PW.

28.

Epoxy the PW tabs in place, using a ruler to line them up with the wing top surface.


29.

Cut the ailerons to length. This should be done right on the model. Groove the ailerons and drill holes for the wire aileron horns. Epoxy the horns into the ailerons.

STOP!
In this picture sequence, the ailerons were covered with silk before they were permanently glued to the wing in Steps 31b. and c.
After completing the wing through Step 46, it was covered with silk and the edge of the silk lapped down onto the back of the wing in the crack between it and the aileron. If you are using plastic film covering, it is best to cover both the wing
and the ailerons separately before joining because of the necessity of ironing the edges. In this case, DO NOT glue the ailerons to the wing in 31b. and c. Leave them loose and proceed with Steps 32, 33, 34 and 35. SKIP 36,37 and 38 until later. Go on with Steps 39, 40, 41, 42 and 43. Now cover the ailerons and the wing, except for the small area involved in Steps 36, 37 and 38. Now glue the ailerons to the wing as directed in 31b. and c. and proceed with Steps 36, 37 and 38. Complete the job by covering the small area left in 36, 37 and 38 with film.

(You can also use this alternate sequence for covering with silk if you prefer.)

30.

Slot the ailerons and glue in the hinges.


31.

  1. Cut holes in the PW plywood tabs to pass the arms of the aileron horns.
  2. Slot the wing to take the hinges that were previously glued into the ailerons. Glue the hinges into the slots. Don't glue the brass bearing yet.
  3. After the glue on the hinges has set up, position the brass tube bearings and epoxy glue them into the corner formed by the back of the wing and the PW tabs. The brass bearings should not be forced against the back of the wing if they don't happen to be touching it. Let them assume the position they were placed in by the gluing in of the hinges. If there is a slight gap between the tubing and the wing, allow it to fill with epoxy glue.

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INSTALLING EASY HINGES
Using a No.11 X-Acto blade (or similar) cut a slot approximately 1/2" in depth and slightly wider than the hinge. After all slots have been cut, insert an Easy Hinge halfway into each slot in one of the pieces to be hinged. Then carefully slide the matching model part onto the other half of the hinges. You'll find it easiest to slide the part onto the hinges at an angle, one hinge at a time.
At this point the surface to be hinged is attached but not glued. Align the two surfaces and adjust the gap between them as required. For best control response, the gap should be as small as possible but big enough to allow the control surface to move to the maximum deflection that you will require. Place three or four drops of any brand of cyanoacrylate adhesive (thinnest variety) directly onto the Easy Hinge in the gap.
You will notice that the glue is quickly wicked into the slot as it penetrates both the wood and the hinge. Continue this process, gluing the same side of all of the hinges. Then turn the surfaces over and repeat the gluing process on the other side of each hinge. After the glue has cured, approximately three minutes, the joint can be flexed. You may notice a slight stiffness in the joint. This can be eliminated by flexing the surface to full deflection each direction a couple of dozen times. Don't worry about shortening the life of the hinge as they are almost indestructible.

AT THIS POINT YOU WILL NEED THE FUSELAGE COMPLETED THROUGH STEP 73.

32.

(NOTE: Picture 32 shows the fuselage bottom block in place on the fuselage but it is best NOT to have it installed when Step 32 is done. Access to the dowels is,much easier when it is not in the way.)
  1. Set the wing in the fuselage saddle. If it does not fit the saddle exactly, sand as required to make it fit.
  2. Hold the wing in position and mark the dowel holes in the wing by punching through the holes in F-2 with a 1/4" drill, a piece of tubing or a rod.
  3. Drill the holes in the wing out oversize - about 9/32" diameter - to allow some "wiggle" room during the final positioning and gluing in of the dowels. Dig out a little foam just behind the leading edge so the glue will form a "collar" to lock the dowel to the balsa.
  4. Put a piece of wax paper over the face of F-2 and insert the dowels through the paper into F-2.
  5. Coat the holes in the wing with Kwik-Set Glue and put enough extra glue in the holes to fill the gap between the oversize holes and the dowels. Don't overdo the amount of glue.
  6. Put the wing in place and secure it in position with masking tape. Hold the fuselage vertically to keep the glue from running out of the dowel holes. Allow the glue to set up firm, but not fully cure, just in case it may have stuck the wing to the fuselage in some leaky spot. Remove the wing. If the dowel holes are not completely filled with glue, fill them. If necessary, now that the dowels are set in place, you can cut away the wood around them to provide room for filling any remaining crack with glue.
33.
  1. Put the wing on the fuselage again with a piece of wax paper between it and the fuselage at the back.
  2. Epoxy the wing bolt anchor blocks in place against the fuselage sides.
34.
  1. Locate the positions of the wing bolt anchor blocks on the bottom of the wing. (Remember that the wing bolt holes are drilled at an angle so that the heads of the bolts will end up flush with the surface of the bottom of the wing.
  2. Drill a hole through the wing and on through the anchor blocks with a No.7 drill. (13/64" is the nearest inch size equivalent.)
  3. Run a 1/4-20 tap through the hole to cut threads in the wing bolt anchor blocks.
  4. Remove the wing and drill out the holes in the wing only with a 1/4" diameter drill to pass the nylon wing bolts.

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NOTE:
If you are in a hurry to get the model built and aren't interested in a perfect bottom line contour between the wing and fuselage, ignore Steps 35 and 36. Look ahead to Step 37 for an explanation of a simplified wing bolt hole reinforcement.


35.

Cut out inserts for the 1/16" plywood PB squares and drill 1/4" diameter holes through them from the other side of the wing. Epoxy glue PB in place.

36.

  1. Cut and notch pieces of 1/4" shaped trailing edge stock to fit over the brass tubing bearing of the aileron horns.
  2. With a tooth pick, coat the inside end of the tubing with vaseline to prevent any glue that may accidently be squeezed onto it from sticking the horn movement. It is only necessary to grease the very end and a small section of the wire. Do not grease the whole tubing -- it should be epoxied to the shaped piece.
  3. Epoxy the shaped 1/4" trailing edge stock in place.


37.

Cut pieces WS from 1/8" sheet and glue in place.



SIMPLIFICATION NOTE:
If you skipped the inset pieces PB in Steps 35 and 36, use the pattern called WSS to cut substitute pieces from scrap 1/16" plywood. Glue these WSS pieces over the holes directly on top of the balsa skin without cutting any inset. Drill through them from the opposite side of the wing. If plywood pieces WSS are substituted, remember that they cannot be shaped to contour as are the balsa WS pieces done in the next step.

38.

  1. Protect the bottom of the fuselage from the sanding block with a piece of light cardboard that will slide back and forth as the wing is shaped.
  2. Sand the 1/4" trailing edge stock and the pieces WS to form a smooth connection contour with the bottom line of the fuselage.

39.

  1. Put a piece of wax paper between the wing and fuselage (which now has the bottom front block installed and shaped) at the front.
  2. Shape a piece of scrap balsa block to fit down into half of the cavity. Make a matching block for the other half.

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40.

Carve the blocks roughly to shape so that the contour of the fuselage bottom block is carried on to the wing.

41.

  1. Glue the blocks to the wing and fine sand the shape as shown.
  2. Fill any small remaining gaps with Sig Epoxolite or a mixture of Sig Kwik-Set glue and micro-balloons or talcum powder.
42.
  1. Cut a cavity in the wing for the servo. Size will depend on the servo and/or mount. Look ahead in the book for further ideas on the requirements for this hole.
  2. Cut strips of 2" fiberglass tape for both sides of the wing center joint.



43. We use regular Sig Epoxy Glue (not Kwik-Set Glue) for applying the fiberglass tape, since it is thinner and easier to spread out smoothly. It will be even easier to spread if you warm the mixing container by setting it in hot water for a few minutes to raise the temperature of the glue. But work quickly, for the glue will set up much faster than normally when warmed.
  1. Coat the wing center with glue.
  2. Lay the tape on 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 made from a scrap of balsa. Scrape over the tape several times with the squeegee paddle to smooth the tape and remove excess glue.
44. Glue hardwood mounts for the servo into the cavity. Coat the entire inside of the cavity with epoxy glue to prevent the foam from being damaged by fuel or dope.

45.

The plastic servo mount in the photo is for a Logictrol servo. Use No. 2 screws to fasten it to the hardwood mounts. For more radio equipment installation instructions look ahead.

46.

  1. Screw the nylon connectors supplied in the kit onto the threaded aileron horns.
  2. Hook the servo to the aileron horns with the rods and HC links.
  3. A servo connector can be used at the other end instead of a "Z" bend, if desired. The SIGSH184 connector is shown here but is not furnished in the kit.