KING KOBRA RC54 FUSELAGE CONSTRUCTION

Before beginning the fuselage, give some thought to your engine installation. The following instructions show an angled installation with the nose gear bearing installed. The angle puts the engine muffler close to the fuselage and places the needle valve of the engine at an ideal level in relation to the fuel tank. We recommend this location unless you have some good reason for changing it.

On one of the prototypes the engine was mounted horizontally, which had the advantage of making it easy to run the tuned pipe under the wing. This horizontal position is only possible if you are using a retract gear and won't have the nose gear bearing in the way on the front of the firewall. A tuned pipe located on the side of the fuselage may require a nearly vertical or vertical position to work out properly, depending on what shape headers are available for your engine and pipe. For engine locations that put the needle valve above the recommended position it might be advisable to fit a fuel pump, such as the Perry Micro-Oscillating Pump, to minimize fuel level change effects and obtain optimum engine operation. However, the amount of variation from the ideal level is not very large so this may not be a problem. If a fuel pump is not used, a muffler or pipe pressure tap to the tank is recommended.
The photo shows a horizontally mounted engine with a Perry Micro Pump installed in the King Kobra. Note that the firewall had to be ground away a bit with a Dremel tool to clear the pump mounted on the back of the engine. Since the firewall is 3 laminations thick, this was no big deal, there was still plenty of wood left to do the job. However, other engines may be bulky enough to require more room in the rear. We suggest here an easy method of getting more clearance behind the engine by lengthening the cowling.
Optional Cowl Extension
The average .60 will not need this addition to the cowl. We show it here for your information should extra room be required.

Sand the gloss off and roughen the plastic in the areas where the Sig Epoxolite putty will be applied. (The putty will almost become an integral part of the plastic if this procedure is followed.) Glue a plywood ring - in this case it was one of 1/8" Lite Ply - to the front of the cowl. Fill the joint with Epoxolite and blend it into the lines of the cowl.




55.

Sand any rough edges of F-1A, F-lB and F-lC. Fit F-lA inside the cowling.



56.

Draw layout lines on F-1A ot the proper width for the mounts and engine to be used and at the angle chosen for mounting. Glue F-1A to the front of F-1B. Use the cowl to check for correct position. If they should happen to be warped (a congenital problem with plywood), clamp them together between two flat plates in a vise while the glue is setting up.
NOTE: Leave the cut-out for the nose gear bearing in F-1A on for retract versions.

57.

Glue F-1C to the back of F-1B with epoxy.

58.

Here's a handy way to fit the mounts to your engine. It temporarily turns them into a one piece mount.
  1. Layout guide lines on a piece of scrap 1/16" plywood of the proper width and height.
  2. Mark the top of the mounts on the sides so they can be accurately located.
  3. Glue them in place on the scrap scab.

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59.
  1. Bolt the spinner backplate to the motor. (This must be done to allow for differences in spinners. For example, the Goldberg spinner has a recessed backplate which requires the motor to be farther forward than a spinner without a recess. This is a good thing, giving more clearance behind the motor for fuel lines or pumps, and is one reason other than the pleasing shape - that we recommend the Goldberg for the King Kobra.
  2. Position the motor on the mounts so the spinner backplate will be 4-7/32" from the face of the firewall (or in this case, the face of the scrap back). It is handy to tack the motor in position with some spots of epoxy, brought up over the edge of engine to grip it good or put a strip of double-faced masking tape between the engine and the mounts. This will keep it from slipping during the next step.

60.

With a punch or sharpened piece of 1/8" wire, center punch the motor mounting holes. (Hint: If you are not used to doing this sort of job, don't try to punch and drill all 4 holes at once. Punch and drill only one hole. Then put the motor back on the mounts, secured by the first bolt. Punch and drill a 2nd hole, repeat the procedure, then a third hole, etc. With this process you are much less likely to make a drilling mistake that will ruin the mounts.) Drilling our mounts will not be a problem if a good quality highspeed drill bit is used, operated at neither too fast nor too slow a speed, lubricated and with moderate pressure.
Remove the scrap back from the engine mounts.

61.

  1. Position the nose gear bearing on the face of the firewall and drill out the holes with a 7/64" bit to pass the bolts.
  2. Turn the firewall over and drill out the backs of the 7/64" nosegear bearing holes with a 9/64" bit to take the shanks of the 4-40 blind nuts. To complete the holes, take a modeling knife and round off the edges on the back of the firewall so that the rounded off part of the blind nut will fit down into the hole when it is pulled tight against the firewall.
Fit the cowl to the firewall next, before the engine mounts are permanently fastened to the firewall. This allows checking out the placement of the mounts in relation to the cowling. Take the carburetor off the engine and tape over the hole. Having it out of the way makes it easier to make the openings with proper fit.

62.

  1. Start the opening with a saw.
  2. The curved part is done by drilling a series of holes about 1/8" in diameter around the area to be removed, then cutting through the bits of plastic between with a knife.




63.

Try for a slightly undersized opening at first, then open it up slowly as you fit it to the engine. Go around the edge with an "apple peeling" motion, paring off a small amount of plastic at a time. Remember, it's easier to take off a dozen more chips than it is to put one back on.



64.

Sit the mounted engine in place. Put the cowl over it and add the spinner backplate. If the backplate is not centered on the cowl, shift the engine-mount unit as required to make the spinner center. Carefully remove the cowl and tack glue the engine mount in place. (We tack glue it partially so it won't move before removing the cowl. Drill through the mounting holes and install 6-32 blind nuts on the back of the firewall.

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65. Be sure and epoxy the blind nuts to the back of the firewall so they will not come out later when it may be necessary to take off the mounts. Work some under the nuts but don't get epoxy into the threads of the bolts. Pull the blind nut points tight into the wood with the bolts before the glue sets up. With the mounts and nose gear bracket in place, cut off the mounting bolts for both flush with the face of the blind nuts on the back of the firewall. This is to prevent any chance of the bolt ends puncturing the tank.

66.

Since the cowl is now finally placed, you can add the 3/8" sq. hardwood mounting blocks to the firewall whenever it is convenient. Shape the blocks to fit snugly against the cowl.



For a neater opening on the prototype, we saved the sawn out portion of the back of the cowl and glued a piece of it permanently onto the fuselage. This filled in the opening behind the engine and gave a more finished look to the installation.

67.

  1. Cut the front pieces of 1/2" triangular stock to size and glue on the fuselage sides



68.

Note the placement of the triangular stock at the front. The bottom stock is placed flush with the dotted line to allow space for the firewall.

69.

  1. Glue on pieces of 1/2" triangular stock on the back of the fuselage sides.
  2. Glue the stabilizer saddle FS in place.


70.

  1. Complete the bottom 1/2" triangular piece.
  2. Glue a piece of 1/8"x1/4" scrap at the back of the sides.


71. Mark the locations of the F-2 and F-3 formers on the 1/2" triangular stock.

72.

Fit the 1/16" plywood die cut doublers FD to the sides.

73.

  1. Glue FD in place.
  2. Mark the location of the bottom of F-3 on the doubler.
  3. Draw the datum line on the doubler.

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CAUTION: Epoxy or gap-filling cyanoacrylate glue is recommended for FD. Water base glues such as Sig Bond, Tite Bond, Elmer's, etc. may cause curling because of the large are a being glued. Spread a thin film of epoxy with a paddle. Don't use a large amount of epoxy glue - it will add weight to the model.

74.

Draw the tank floor top line. See full size plans for more tank floor directions.

75.

Look ahead to Picture 90. You will see pieces of 1/2" triangular stock being glued on the back of the firewall. These must be cut to fit against the 1/2" triangular stock on the fuselage sides. Do this now, on the sides, while it is easy, before they are joined together. Lay the pieces aside for use at Picture 90.



76.

Cut the fuselage sides from the sheet. Don't cut too close, leave a bit for sanding.

77.

  1. A small gap remains at the end of the front bottom triangular stock. Cut a small piece of 1/16" balsa sheet, thinned down to 1/32" thickness to fit in this gap.
  2. Glue it in place.

78.

Pin the two fuselage sides together, outside to outside, and match them by sanding as required to make them exact duplicates.

79.

  1. Turn the sides upside down on the top view plan.
  2. Note that the little end tab on the fuselage needs to be over the edge of the bulding board so that the rest of the fuselage top, from F-6 forward to F-3 will be on the board.
  3. Use some square iron or other weights at the rear where the fuselage can't be pinned down. The sides must be held firmly in place during the next steps.

80.

Glue the first piece of 1/8" sheet balsa bottom planking in place to hold the fuselage rear together.

Skip former F-6 until later. Because triangular stock by nature is not perfectly accurate, it may be necessary to sand the former corners to fit properly against the angle.

81.

Glue F-5 in place using pins and tape.



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82. Continue forward gluing F-4.

83.

Add F-3.

84.

Prepare F-2 in advance, using the pattern, with dowel holes drilled and doubler installed. For fixed gear airplanes, cut out an access hole to the nose for inserting the battery if balancing requires this.




85.

Unpin the fuselage from the board and tilt it forward on the front portion between F-3 and the firewall. Glue F-2 between the sides. Since the front is stiffer and harder to bend, we switched to tack gluing temporary cross pieces to hold the sides in place during this operation.

86.

Remove the sides from the board and glue the F-l firewall assembly in place. Cover the blind nut holes with tape to keep glue out.

87.

Fit F-6 between the sides and glue it in place. Since it will key the front of the stabilizer, make certain that the top of F-6 lines up with the printed edge lines on the fuselage sides.




88.

Cut FTB from 1/4"x5/8" trailing edge scrap. Add FTB just to the rear of F-4. The edges of FTB must be beveled to fit against the triangular stock.



89.

Complete the bottom planking up to the rear of the wing opening.

90.

Glue the previously cut triangular stock to the firewall.

91.

Glue the tank florr into the fuselage but for retracts, do not glue the floor in permanently until the nose gear unit is fitted. Read the suggestions on the plans.

HINT: We put a drill bit of the same diameter as the inside of the tubing into the end of the tube and used it as a handle for bending. Back it out a small amount at a time, adding a bit to the bend each time you move out. The result is the nice kinkless bend seen in the picture.

92.

Cut a notch in F-2 to pass the tank bubble.

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93. Bend the tubes of the tank so they point directly forward. Drill holes in the firewall to pass them.
If you have trouble bending tubing try K&S 1/8" Soft Brass Fuel Tubing.




94.

Put a scrap wood block on each side of the nose to hold the tank in place.

95.

Retain the tank with a scrap ply bar tack-glued across the back. It can be pulled off when the tank needs to be removed.

96.

When a 12 oz. Sullivan RST tank is used, a complete piece of top triangular bracing can be used as shown here in this Kougar picture. You will have to cut away part of it for the 14 oz. tank to pass the tubes. Make certain now, before the compartment is closed in, that the tank can be installed and replaced from the wing opening without trouble. Fix anything in the way. Hold a piece of sheet on the top to make certain there is no hangup on it. This is a good time to oilproof the compartment. Put in properly, you will seldom have any need to take out the tank and it is not difficult to do so when necessary.




For the fixed gear version, the bottom block is installed in the same way as the following Kougar pictures 98, 99 and 100. The 7/8" tank hole shown is for a 12 oz. RST tank when the entire tank cap is brought through the firewall.

Newer Sullivan tanks require a larger 15/16" hole. Other brand tanks may require a different opening.







97.

Complete the nose pushrods before putting on the bottom nose block.

98.

Fit the 3/4"x3" bottom block between F-1 and F-2.

99.

Hollow the bottom block out to make room for the battery in the nose if required for balance.

100.

Glue the block on and shape it.

101.

Sand fuselage top level and smooth.

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102. Glue pieces of 1/8" sheet to the fuselage top. (Do Step 43 before this one)

103.

  1. Position the top & canopy on the fuselage.
  2. Outline the position of the plastic fuselage top and canopy on the top of the fuselage with pencil. (Read note below.)
  3. Carve to shape.






NOTE: The plastic top has a tendency to "suck in" along the bottom after molding. Plan the next steps to correct this by spreading the sides out slightly to a pleasing contour as the gluing rails are installed. (The canopy does not have this problem.) Also, look ahead to pictures of former FT which must be worked, into the assembly at the same time.

104.

Final shaping of the nose is best done with the cowl in place, sanding both fuselage and cowl to blend smoothly together. Be sure and use fine sandpaper to remove any scratches left in the cowl after shaping.

We covered the fuselage at this point with Koverall and doped it several times so that these jobs did not have to be done with the plastic top installed and in the way. You may want to do some plastic film covering at this point.

105.

  1. Trim the front rail at an angle to fit against the front of the top.
  2. Pin on the 1/8" sq. side gluing rails, using the lines as a general guide, with the angle of the pins inward. Sit the top in place and see if the spread of the sides of the top is about right. If not, re-pin the rails and try again.




106.

Bevel the edges of FT to fit inside of the back of the plastic top. This operation must be done in conjunction with the gluing rail installation. When everything is fitted, FT can be glued in permanently.

Sig-Ment may be used to fasten on the fuselage top. Don't put on large blobs - they may melt the plastic. Work quickly or the Sig-Ment will get too dry and not stick properly. "Super" cyanoacrylate glues are handy for attaching the top. Put it in place and run the glue under the seam between the plastic and the gluing rail. Or use slo-set glue, put on the rail before adding the top.

107.

Taper the gluing rails for the canopy so that it fits against them snugly. The canopy must be trimmed down slightly to fit properly against the fuselage top. Both the back and bottom can be trimmed to get this accomplished. Do not install the canopy permanently until it is painted and the fuselage is completed and painted or covered. See the canopy painting section for information on glues and paints to use.

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Optional Wing Fillet






On the original prototypes, a small wing fillet of Sig Epoxolite was installed. The main purpose of this was to make a good seal at the wingfuselage joint. It was put on after the model was covered with Koverall and clear doped. On models with plastic film covering, fillet first. In this case it will be easier to cover the model if the putty is trimmed off flush with the fuselage side rather than given a fillet shape.

Here is the procedure for making an Epoxolite fillet:
  1. Mask off the side of the fuselage-where the Epoxolite will be applied. It need not be a very wide strip - about 1/8" was used on the prototypes.
  2. Tape a strip of wax paper on top of the wing on each side where the fuselage will touch the wing.
  3. Apply a bead of Sig Epoxolite to the fuselage side bottoms.
  4. Put the wing on and bolt in place. This will cause the putty to squeeze out from under the fuselage onto the wax paper protective strips on the wing.
  5. Spread the excess putty onto the 1/8" strip of exposed fuselage side and start a rudimentary fillet shape.
  6. After the Epoxolite has gotten partly stiffened, shape the fillet further using a wetted finger or tool of the desired shape.
  7. Allow the Epoxolite to set up.
  8. As soon as it is hard, but not fully cured, remove the wing.
  9. Trim off the excessthat squeezed into the inside of the fuselage and even the outside edge of the fillet.
  10. Smooth the outside edge of the fillet and shape the fillet with a round tool covered with coarse sandpaper - 60 or 80 garnet. If you use fine paper it will clog up too rapidly. Be careful not to sand through the masking tape protecting the fuselage, but sand down to it so that the tape can be peeled off, leaving a clean edge on the fillet.
  11. After the fillet has cured (24 hours), fine sand it and feather the edge formed by the masking tape into the fuselage side.
Don't get carried away with this idea, it can get heavy. Keep the fillet small. This same procedure can be used just to seal the wing-fuselage joint without an external fillet. No tape on fuselage necessary in this case, just trim off excess Epoxolite flush with the fuselage before it cures completely

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TAIL SURFACES

NOTE: The design of the stabilizer-fuselage joint includes a simple method of insuring proper incidence alignment of the tail. Make sure you understand it before proceeding. Study the pictures and drawings. The 1/4" sq. main frame of the stabilizer in the center at front and back is left exposed in order that it can be mounted directly on the fuselage. The front 1/4" sq. main frame area sits on the top of F-6. The rear 1/4" sq. main frame area sits on the top of the tab at the end of fuselage side. The result is a keying of the fuselage and stab together with zero incidence.

108.

Build the 114" sq. balsa main frame of the horizontal stabilizer directly on the plan.
(The grey toned area of the drawing indicates the main frame outline.)

109.

Note that the tip pieces of 1/4" sq. are inset to allow space for later installation of rib S-6.

110.

Cut a piece of 1/4" sq. to fit in the center joint of the leading edge.

111.

Glue in place.




112.

Mark the locations of all ribs, front and back, on the 1/4" sq. main frame.


113.

  1. Tack glue a temporary scrap balsa cross brace across the top of the 1/4" sq. stabilizer main frame on each side.

114.

Remove the frame from the board and glue piece STB in place. (See cross section drawing)




115.

Place scrap 1/4" sq. standoff pieces on the plan in eight different locations, as shown by the arrows.

116.

Return the main frame to the board, this time pinning it on top of the standoff pieces.

117.

Bevel the rib fronts to fit the taper of the leading edge. Glue the ribs into the main frame.

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118.

Remove the assembly from the plan. Turn it over. Glue the 1/8"x318" spar in place on each half.











119.

Remove the temporary cross pieces and complete the spars.

120.

Cut 1/8" scrap pieces. Glue in place. (Provides gluing area for sheeting around the keying gap.)

121.

Carve and sand the leading and trailing edges to contour.

122.

Smooth the stabilizer with a sanding block

123.

Glue 3/32"x3" to the top of the stabilizer frame.

124.

Glue the 3/32"x 3" sheet on the bottom, leaving the keying gap exposed. (There is no gap on the top.)

125.

Continue sheeting the stabilizer doing both sides as you go.

126.

Leave the front keying gap exposed and unplanked. (On the bottom only.)




127.

Glue the 5/16"x5/8"x3-1/4" blocks on the tips of the stabilizer.

128.

Carve and sand to contour.

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129.

Shape the elevator stock in the same manner as previously shown for the aileron stock.

We are asked why so many parts are used for the sheet tail when it would be easier to make it with a single grain direction. The reason is to provide a stiffer and more warp·resistant tail. The different grain direction of the parts makes the finished surface stronger. It only takes a few minutes longer to glue the parts together and it is worth it.


130.

Cut out the tail parts. Fit them together using the sanding block. Glue and pin them down on wax paper. (R·2 is cut from 5/16"x2"x12" sheet. R-1 is glued in last.. Not shown in the pictures.)



131.

Sand off the printed lines and round the leading edge of the fin. Properly sanded, the fin will be nearer 1/4" than 5/16" thick.

132.

Carve and sand the rudder to the cross-section shown above.

Put the wing on the fuselage and check to see if the stabilizer lines up with it when pinned in place on the fuselage. Make sure the stabilizer saddle in the fuselage does not prevent the 1/4" sq. main frame keying gaps from sitting down firmly on the fuselage. Sand the saddle down if it does. If any modifications must be made for side-to-side alignment, be careful not to change the incidence of the tail by disturbing the relationship between the top of F-6 and the back of the fuselage sides. This same caution goes for any changes necessary in the wing saddle necessary to line up the wing.

133.

Draw guide lines for the fin.

134.

  1. Fit the fin and rudder to the fuselage.
  2. Make certain the rudder has enough clearance so as not to rub on the stabilizer at full movement of the controls.
  3. Cut a slot just in front of the stab to pass the rudder pushrod.

If desired, you can add a nylon pushrod guide (not furnished). The elevator pushrod exits through the openings in the fuselage rear. Open it up as required to pass the pushrod. The pushrod wire may be bent slightly if it tends to rub on the fuselage.



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135. Inset a scrap of 1/16" plywood into the elevator and rudder on the opposite side from the control horn. This will prevent the horn from pulling through the wood when subjected to unusual strain. The control horns should be installed before covering, then removed until the covering is completed.

The stabilizer, elevator, fin and rudder should be covered andlor filled before permanently gluing in the hinges. To insure that the tail parts are solidly glued to the fuselage, cut out the covering material in the mating areas to expose bare wood. Puncture a series of 1/16" holes with a pointed wire in the tail and the fuselage top where they make contact. Have the holes at a slight angle to each other. When the epoxy glue is worked into these holes and sets up it will act like small nails, holding the parts together. The stabilizer saddle on the fuselage may not fit up perfectly against the stab because to make it do so might disturb the necessary seating of the main frame mounting gaps to the fuselage. If tl\e epoxy glue does not fill the stab-fuselage joint completely, complete sealing the seam with a mixture of epoxy and micro-balloons.

136.

  1. Cut the tail blocks to shape, using the top and side view patterns.
  2. Sit the block in place on the fuselage and against the fin and trace the shape of the plastic top on the front of it.

137.

Put the fuselage top in place and cut the rear of the block to fit against it.

138.

Carve and sand the block to a rounded contour to match the shape of the plastic fuselage top.




It is suggested that the blocks not be glued on until the fuselage and tail have been covered, the tail mounted and the plastic top permanently installed.

PUSHRODS

By the time most fliers get to a .60 powered airplane like the King Kobra, they have developed their own personal ideas about their favorite types of pushrods. Normally we include balsa pushrods for the elevator and rudder in kits and have had good results with them. But some builders worry about balsa pushrods in a very fast and aerobatic airplane. Others like nylon tubing pushrods or hardwood dowels. Therefore, rather than put in (and have to charge for) a pushrod that some of the builders would not use, we are furnishing none, leaving the choice to the individual buyer.

In the prototype King Kobras we used the Sig SH-654 Graphite Pushrods, a arrow-shaft type made from the new high-tech carbon material that is finding so many uses in modeling. It is recommended for those who want to use the ultimate variety rod. SIGSH559 Flexible Cable pushrods were used for the nose wheel and throttle.

RETRACTS

Because the King Kobra is a compact aircraft there is not a lot of wasted space in which to loose a retract unit. But that's better than having room to spare and the extra drag that goes with it. We designed the model first and found a way of fitting the gear into it, which seems to be a better approach than designing an airplane around a retract gear, particularly since the majority of King Kobras will be built by sport fliers.

The Spring Air 200 Series Retract Gear was selected for the King Kobra because it was ideally suited to the space available. The units were fitted in without having to compromise the concept of the model. They have proven to be both reliable and durable. You may use either the No. 201outfit with double coil main gears, or the No. 202 with single coil main gears. The shock coils are the only difference between them. We used single coil.

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Those who look closely may notice that we happen to have 100 series units in the wing because they were on hand at the time we were building. For all practical purposes they are identical in mounting and usage to the 200 series. You must, however, have a 200 series nose unit (No. 205) with single arm steering that comes in the No. 201 or No. 202 outfit, for best results in the nose.

Though the pictures are only of Spring Air equipment, they still should be useful in providing guidance for mounting other types of retracts.

Full size drawings on the plan show the amount of space available for the nose units. Make certain that both the mounting and nose gear steering methods of the units you select will adapt to the King Kobra before buying them. There should be no space problem in the wing for most any kind of retract units.

The kit does not include any parts or materials required for retract installation.

139.

The wing mounting plates are cut from 3/16" plywood. 4-40 blind nuts are epoxied on the backside.
NOTE: The wing core has a slot cut out for the fixed gear grooved mounting block. In most retract installations this slot will have to be enlarged further during installation. If you find that your gear does not require all or part of this slot, glue scrap foam in it.

140.

A small sanding tool is handy for making openings in the core for the retracts. This one is made from scrap plywood.

141.

Drill 3/16" holes through the mounting plate and out the other side of the core. Epoxy the plate to the foam. Cut dowels of the proper length to go completely through the wing to the opposite surface. Epoxy them in place.




142.

Excavate the foam as required to pass the retract unit and wheel.

143.

Line the sides of the wheel wells with balsa wood. Wet it to make it easier to bend in place.

144.

After sheeting the foam cores, cut out the openings for the wheel and retract unit.

145.

Cut the nose unit mounting place from 3/32" ply (not lite ply) and glue it to the bottom of the tank floor.




SUGGESTION: As supplied, the nose gear has the coil located farther from the unit than is required for this installation. Before beginning, shorten the top of the gear so that the coil will be as close to the unit as possible without interfering with the retracting motion. Careful! Don't take off too much, check as you go. (It's easy to work the units by hand once you get the knack of catching the sliding brass bar with a thumbnail on each side and pushing away from the cylinder.) Don't bend the wheel axle into the gear until you are certain of your airplane ground angle. Set it up on the bench to be certain.

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146.
  1. Brace the mounting plate to the sides with triangular stock through the mounting plate and tank floor.
NOTE:
There is not much room for the Spring Air steering arm in the nose. In the installation shown in the following pictures the situation was carried to the extreme by mounting the nose unit slight off center to the left of the fuselage center line so that the wheel would retract into the exact center of the wing. This turned out to put the steering arm through the bottom fuselage block. The problem was avoided by first trimming down the plastic end of the steering arm to give more clearance. Next, the left side balsa bottom block was tack glued on, carved to shape and removed. The outer surface was covered with fiberglass cloth and resin. A router was used to remove all of the balsa from the block in the area of the steering arm movement right down to the inside surface of the fiberglass outer shell. This got the arm clear, but with only about 1/16" to spare - but a miss is as good as a mile.

Perhaps you should consider not being so picky as we were about the wheel being centered and instead put the unit in the center, letting wheel retract slightly off center. This will give a bit more space for the steering arm, though it probably still is worth-while to put the cloth and resin on the outside of the bottom block so it can be completely hollowed out for clearance without having to worry about cutting through the side and spoiling the block.

147.

Epoxy 4-40 blind nuts on the top of the tank floor. The mounting bolts for the unit must be trimmed off flush with the floor so as not to damage the tank.
See Suggestion (1.) on the full size plan before deciding on tank floor installation. This more recent method provides 1/8" more mounting space, which gets the steering arm higher and farther from the fuselage side.

148.

Cut out F-2 to pass the wheel. This hole could be cut out before the fuselage is assembled if you plan ahead. If not, a Dremel grinder is a help.




149.

As previously mentioned, the Spring Air steering arm has minimum clearance on the inside of the nose block. Therefore the arm must be located flush against the unit to get it up as high as possible. To do so you will probably have to grind away a bit of the frame so the set screw will not drag on it during full movement of the steering arm.

150.

  1. The triangular stock must be whittled away to clear the steering pushrod.
  2. Mount the cable pushrod tubing on a scrap balsa standoff. We used silicone cement to glue pushrod tubing in place. Its flexibility avoids binding problems that a rigid epoxy gluing job can sometimes cause.

151.

The complete nose gear steering installation should be completed and tested with the servos operating before proceeding.




152.

Cut the balsa bottom block supplied in the kit in half. Fit the halves onto each side with the required opening in the middle. Tack glue them in place.

153.

Carve and sand the bottom blocks to contour. Cut through the tack gluing and remove the blocks. Now is the time to coat the outside of the left block with fiberglass cloth and resin. Carve out the inside of the blocks to pass the pushrod and provide space for maneuvering the unit into and out of the fuselage. (Do not build the unit in so that it cannot be removed.) The hole you see is just large enough with the hOllowing inside to allow the unit to be pulled to the back and out the wheel hole.

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154.

Put the wing on and mark the area needed for the wheel well.











155.

Enlarge the marks by 1/8" all around.

156.

Saw out the hole.

157.

Line the hole with 1/8" plywood.

158.

Cap the top of the well with 1/8" ply. This cap should match the level the tank floor so that the well is closed off from the inside of the fuselage when the wing is mounted.

159.

We made the wing fairing on the retract gear Kobra from sheet rather than blocks because of the well being in the way. This piece is inset into the sheet wood of the wing at the back.

160.

Trace the outline of the fuelage on a piece of 1/8" scrap.

161.

Draw an inner line inside by the thickness of the sheet used. We used soft 1/8", but 3/32" would bend easier.

162.

  1. With wax paper between to prevent sticking, glue the scrap former to the wing.
  2. Add a scrap side former as shown.




163.

Soak the sheet wood in water until it is pliable and bend it into place.

164.

This shows the air tank and control valve installation in one King Kobra. The servo for the valve was put on the wall of the fuselage just ahead of F-3.

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165.

Here's a handy spot for the air charging connection. It is just ahead of F-2, next to the wheel.





Below:
The radio installation in the King Kobra. The receiver and battery have been wrapped in Sig Foam Rubber.


A simple method of securing the tuned pipe using brass strap and the wing screws. This installation has easy access to the screws, but the pipe is at a slight angle to the slip stream. An offset bracket and use of hex head screws will provide a parallel position.


NOSE GEAR INSTALLATION

The wheel collar suggested as optional for the nose gear is not furnished. File or grind a notch in the collar so it will fit down on the coil farther. The collar permits altering the height of the nose gear slightly if desired. Don't try to make large adjustments in nose wheel height with the wheel collar because the landing gear is more easily bent on a hard landing if the coil spring is located very far below the nylon nosewheel bracket. Large adjustments should be made by changing the wheel size.