Kit contents:
Fuselage
2 tapered wing panels
1 center section
2mil coroplast sheet with fuselage doublers
4mil coroplast horizontal stabilizer and vertical fin
1 roll colored packing tape
firewall wood
control horns and pushrod wire
instruction sheets with patterns
WARNING
You can hurt
yourself, building this kit! Please use caution and follow proper safety
procedures when using the tools and the adhesives needed to assemble
this kit.
Powered models are
dangerous! All model airplanes present a certain amount of danger to the
operator and anyone in the vicinity. Please be careful when starting the
motors and use good safety practices when operating this model. Wear eye
protection.
We at JK Aerotech, have no control over how this
product is used. You, as the operator of this equipment assume full
responsibility during the building and flying of this model to operate
it in a safe manner. Do not start the engine with anyone, including
yourself, in line with a spinning prop or directly in front of a running
motor (I have seen props come off). Always keep hands and fingers out of
the spinning prop. Do not fly over people, or in populated areas. BE
CAREFUL!
By building and
flying this model you have agreed to take full responsibility for any
property damage and/or personal injury or death caused by this model.
Building and flying
should always be done with adult supervision.
First cut the tail sections out of the corrugated plastic
sheets. This material is very stringy and will not die cut cleanly so
carefully trim away with a razor blade or scissors.
TAIL
I generally start with the tail group. Find the approx. hinge
line by slipping the elevator into the fin (or just hold it up to the fin
and line the tab and slot up) and pick a rib that will allow the elevator
to move up and down without binding on the clearance hole in the fin.
Fuselage
We supply a chunk of plywood and a pattern for the firewall. The
pattern shows the centerline of the engine mount so I glue the pattern to
the wood and use a band saw to cut it out. Then use the pattern to line up
the motor mount position. This plane is sized for most usual .25 two
stroke engines so the firewall, mount, and engine combined will
position the prop and spinner to clear the front of the fuselage doubler.
If your motor is a little short, you can either add a little foam
to the front of the plane or trim the fuselage doublers off a little to
clear the spinner. If you add foam or take away foam from the front of the
nose, be careful not to change the thrust line of the engine.
After the fuse is shaped the way you want it, cut out the
fuse doublers and tape them to the sides of the fuse to get the canopy
line. If you line up the doublers on the wing cut outs, the top of the
doublers will define the front of the canopy. You will have to refer to
the drawings to approximate the back canopy line that runs from the back
edge of the doublers to the rear top of the rear deck. Mark the canopy and
use a sharp razor blade or snap blade knife to slice the canopy off. Take
several slices around the canopy line with each slice going a little
deeper and you will eventually get it to fall off. Set the canopy aside
for now and get your fuel tank out.
Note: the production doublers do not go up to meet at the back of the canopy as these do on the prototype.
FUEL TANK
The fuel tank is area laid out and cut in at this time. If you use our Du-Bro 4oz tank, you will need to cut a hole almost all the way through the nose of the plane just behind the firewall. I like to go in from the left side of the fuselage, at about the center line, and dig a pocket that fits the tank snugly with about a 3/8 inch of foam left behind the firewall for strength and cushion in case of a crash. I like to crowd the tank close to the left surface of the fuse to give me a little extra foam on the right side to make a slot for the throttle servo pushrod.
You will have to accommodate the lines coming from your particular tank and a good way to help everything slip into place is to make the pocket long enough so that there is a little space for the fuel and vent tubes at the front of the tank area. If you use the Du-Bro tank, The fuel and vent lines work real well if they exit just above the top edge of the motor mount (Ernst mount) with the fuel line exiting on the left side and the vent on the right and both bent sort of up and pointing away from the center line of the firewall. You can get creative here – this is just what worked on mine.
The picture below is of the same location only after the fuse is taped. The servo is installed when the fuse is taped but I thought I'd show how the throttle linkage and servo are hooked up.
You should now have a sanded fuselage with a firewall, tank,
and throttle linkage installed so the next step is to glue the fuselage
doublers on. These will cover each side of the fuselage from about the
back of the wing forward and will be long enough to make the side of a
cowl. If you miscalculate and get the engine a little to far back, it is
easy to trim the nose a little to make it fit.
DOUBLERS
Before gluing the doublers on, do two things. The first is to
use a blunt object and score the ribs on the inside of each doubler to
help them conform to the shape of the fuse, and the second is to locate
and cut a trap door on the side that you cut the tank in for access to the
tank later on (that would be the left side if you cut the tank in on the
left and you could skip this if you don’t care about tank access). Cut
the door on only three sides so that one of the ribs in the coroplast will
make a built in hinge.
Put
a bead of Goop around the edge of the fire wall just before sticking the
doublers on. (note: never use Goop on uncovered Styrofoam as it will melt,
use only on taped up foam)
Use
77 spray glue to stick the fuselage doublers on and be very careful to
line them up to the wing saddles on each side. Now you will see why you
scored the inside of the doublers. They should conform rather nicely to
the contour of the sanded fuse and if you let the contact cement dry well,
should mould themselves to the nose.
Since
the fuselage is sanded to shape, including the under wing scoop, you can
cut the scoop off now to allow the installation of the wing. The scoop
will be covered and re-attached later on after the wing is installed.
Note the strapping tape holding the edges of the doublers tight to the fuse.
Note: the blue line on the doubler is like the production version of the kit.
After
fitting the extra 2mil coroplast top and bottom, glue them on with spray
glue and a bead of Goop on the edge of the firewall. Use a hand tacker or
staple gun to staple through the coroplast into the edge of the firewall
all the way around. This will make the firewall very solid and able to
withstand unbelievable crash forces. If you don't have a staple gun, use
1/2 inch wire nails, upholstery tacks, or even thumbtacks. Just be
careful that you don't drive them through the fuel lines, if you have
already installed them.
Before
proceeding with the taping, spray another light coat of 77 spray glue over
the foam part of the fuselage and let it dry.
The
second major key to the strength of our planes is to wrap strapping tape
around the nose from the firewall back to the canopy. Do the same on the
under belly from the wing saddle to the firewall. Lay the strips side by
side and pull them hard enough to cinch the coroplast down tight to the
foam. I use long enough strips to go over the top and down the sides about
half way then turn it over and do the belly the same way. I like to do the
same thing with the wing saddle. Lay strips of strapping tape side by side
and cover the whole wing saddle and let the ends run up the side of the
doublers about an inch. Pull these tight as you put them on too.
When
strapping tape is wrapped radially around the nose and wing saddle, you
will make the nose of the plane virtually unable to crush or buckle. The
strength of this construction will be evident on the first ground plant.
TAPING THE FUSELAGE
Now we are ready to start covering the fuselage with the
colored packing tape. Curved and rounded surfaces, as found on Mig 3s and
most other war birds, can be a bit of a challenge to the first time foamy
builder. My first bit of advice is to relax and don't stress out about a
few wrinkles. We really don't care too much about how it looks because
these planes are designed to maximize fun, take extreme punishment, and
then throw away! Now, that having been said, with a little care, a few
tips, and experience at sticky-tape handling, you will be able to turn out
a reasonable looking product also. Check our web out for tips on taping,
painting and detailing the planes.
The place to start is at the wing saddle. You should already have strapping tape covering the saddle from side to side so now we want to cover it with color. Start at the trailing edge of the saddle and lay packing tape across the saddle letting the tape run up the side of the doublers an inch or so. Keep laying in strips of tape with about a 1/4 inch overlapping the preceding strip until the saddle is completely covered.
Note the strip of strapping tape along the side of the fuse...
After the saddle is covered side to side, you can cover the
fuselage. First lay a strip of strapping tape along each
side from the nose to the tail then start laying strips of colored packing
tape on the fuselage from front to back. I like to start on the bottom and
work up the sides. Overlap the preceding strip by about 1/4 to 1/2 inch
until the whole fuselage is covered. Use the tip outlined above to help
the tape conform to compound curves, unless you like lots of wrinkles. If
you make lots of slits to help the tape conform, it is sometimes good to
lay another strip of tape so that the previous slits are covered -- even
if it means overlapping the strips of tape an inch or more.
If your plane will use the doublers to make the cowl, it is a
good idea to let the tape run long enough to tape around the front of the
doubler to cover the inside of the engine compartment all the way back to
the firewall. After the fuselage and engine compartment is covered,
lay vertical strips of tape on the firewall, from top to bottom, to seal
it.
Since the Mig has the belly scoop cut off, you will have to
leave that area uncovered until the wing is on and the scoop is glued on.
At
this point you should have a fuselage that is completely taped up except
for the belly scoop area. The tail group should be dry and ready to
install now. I use a coat of 77-spray glue on the part of the tail that
slips into the fuselage. Now, you have to be fast so have the slot in the
fuse open (slice along the covered up slot and push the excess tape into
the slot) and ready to receive the tail group. Then, quickly spray a wet
coat of 77 glue on the parts of the tail that fit into the fuse. Before
the glue starts to set, slide the tail into the slot of the fuse. Make
sure the fin is straight and true with the centerline of the fuse and
squish the sides of the fuse onto the fin. If you are not careful, it is
easy to give your plane a permanent right or left turn by bending the back
of the fuse one way or the other. The goal here is to assemble the tail
group and fuse while the glue is still wet to allow a little slippage so
they can be aligned properly---good luck, work fast! Apply a strip of
packing tape under the fuse to close up the tail slot, then run a small
bead of Goop on either side of the fuse to stick and seal the horizontal
tail to fuse joint. Block the fuse and tail so they will cure in good
alignment.
You should now have a completed airframe ready for radio gear
and wing installation!
Before making the wings you need to prepare the wings for the ailerons. Most of our combat war birds have tapered wings. Tapered wings tend to get thin at the trailing edge towards the tip. Our aileron stock is 4 mil (about 1/8 inch thick) coroplast cut from the left over horizontal elevator material. So before you start prepping the wings, you will need to trim and sand the trailing edge. Make it a constant thickness, root to tip, that will approximately match the coroplast material. Usually the root is at about the right thickness. If it is thicker than the aileron stock, sand it down a little first. Then use a straight edge and mark a line from the root to the tip so that when the wing is trimmed, the trailing edge is a constant thickness. In effect you will be making the wing a little more tapered by maybe ¼ to 3/8 inch at the tip of the trailing edge. This is OK, we have sized the wing to take the trimming into account. For the ailerons to work efficiently and smoothly, the trailing edge has to match the thickness of the ailerons.
On this plane the top and bottom surface of the wing tip can
be gently thinned and rounded over. Sand the top and bottom surface of the
wing and the center section smooth with 100 to 150 grit sandpaper and dust
off thoroughly. This helps the tape to stick. We have included a center
section that has the dihedral cut into it. Check the dihedral for accuracy
before gluing the panels to the center.
Alternate method:
If you didn’t install spars – do this, if you did
then skip to the aileron section: After the strapping tape
"spars" are on, start at the trailing edge of the wing and lay
strips of strapping tape, edge to edge, span-wise across the
center section and out each wing panel about 10" from the center
joints until the wing center area is completely covered. Then do the same chord-wise
out about 6" from the center joints only overlap the tape about half
it's width. Do the same top and bottom. What we are after here a double
layer of strapping tape with one layer at 90° to the other one from the center of the wing out about 6
to10 inches from each wing joint.
After the strapping tape reinforcement is on, use the colored packing tape
and tape chord-wise from the center out to about 10" from each
wing joint. Overlap each successive strip of tape about 1". Do that
top and bottom and let the ends of the tape wrap around to leading or
trailing edge to the other surface about an inch. The main idea here is to
use lots of tape to beef up the center of the wing because the wing takes
the most stress from the joints to about 10" out the wing panel.
Now you are at the point where you have to decide if you want
a spar or stiffener in the wing besides the tape. We highly recommend a
spar with the type of stress that a fast .25 size engine can put on the
wings. We have found that Bamboo Shish kabob skewers work great for cheap
and plentiful spars. However,
you could stiffen the wing dramatically by epoxy-ing a couple layers of
1" wide fiberglass or carbon fiber tape across the top and bottom of
the wing from the center out at least 12 inches or to the wing tip if you
want. Sand a little trough to lay it in first so it blends with the
surface of the wing. If you use Skewers, balsa, spruce, carbon fiber rod,
etc., you will need to sand a groove top and bottom at the thickest part
of the airfoil. You can glue it in using 5 min epoxy, wood glue or
urethane glue. Check our web for tips on making spars and repairing wings
from the Tech section. The strapping tape used on the wing handles the
tension part of the stress very nicely. So make a spar if you want, or you
can use layers of strapping tape to stiffen the wing as follows. The only
problem with this is that the wing could start flexing in a hard turn with
a powerful engine plus, I think you can make a lighter wing using spars
and less tape.
However
you decide to do it, run three or four strips of strapping tape from wing
center to each tip, top and bottom. Dihedral wings are hard to do in one
length so I start across the center section and pull to each tip. Use a
slight stretch on the tape. If the wing panels are bowed up or down, pull
harder on one side to correct the bow.
After applying the strapping tape to the wings, it is time to prepare the ailerons. Cut the ailerons from the elevator sheet. make the ailerons about 1/2 to 5/8 wide and make them a little longer than the wing panel because we will trim them to the curve of the wing tip after they are installed. The width of the ailerons is just right if you slice the coroplast so that two complete ribs remain with half a rib left on each side.
First make a mark on the wing so that the inboard edge of the
aileron will have about ¼ inch of clearance between it and the fuselage.
The wing will have a dihedral in it already so we will work with one panel
at a time. Put a weight on the panel to hold it flat on the table. Lay the
aileron on the table next to the trailing edge with about 1/8” gap
between it and the edge of the wing. Cut three small pieces of colored
packing tape about ½” by 1”
and stick them across the 1/8” gap with one on each end and one in the
middle to help hold the gap constant. Now pull off a strip of packing tape
the length of the aileron and lay over the aileron and wing, lining up the
edge of the tape with the back edge of the aileron.
Tip: when laying a long piece of packing tape
down along a wing or other flat surface, stick one end and smooth it down
evenly working from the stuck end toward the end you are holding. Slide
your hand along the surface while holding the other end off the taped
surface, keeping a little tension on it. This will minimize trapped air
bubbles and wrinkles. If you get a little bubble, use a pin and poke the
bubble in the center and push the air out.
Now you will want to cover the bottom of the aileron with tape so pull off another piece of packing tape the length of the aileron stick it on - lining up the edge of the tape with the edge of the aileron. So now you will have the aileron folded back over the wing with a strip of tape stuck to the aileron with a lot of the tape left hanging off the back edge of the wing.
I like to use my thumb and slide it back and forth over the back edge while sort of rolling my thumb over the edge a little bit more on each pass. This will crease the tape and roll it over the edge smoothly and evenly, lessening the chance of wrinkles. Roll the tape over the edge so it will stick to the sticky tape in the 1/8th inch gap then use your thumb and roll the rest of the tape around the bottom edge onto the bottom of the wing.
Take off the temporary masking tape and fold the aileron out
flat. If you did this right, the hinge should be flat across the top
surface and the bottom tape should go up to the top tape in the 1/8th
inch gap and stick solidly to it making an airtight and very strong hinge
line. Finish the hinge off by flipping the wing over and sliding a blunt
object, such as the back edge of a table knife, along the hinge line to
make sure the top and bottom tape are firmly stuck together. Now attach
the other aileron the same way and then you are ready to finish the wing.
When covering wings with packing tape, always follow this simple taping convention: Always start at the back and work forward overlapping about 1/4". This way the tape edges will flow with the wind instead of pointing into the wind. Another good idea is to always start with the bottom of the wing so that the finished wing always has the top tape wrapping over the bottom surface. It just looks a little neater.
With dihedral type wings, it is always easier to tape from the middle out
to the tip. Start at the trailing edge and lay the regular 2" packing
tape across the wing from the middle to tip. Let the center over lap the
far seam about 1". Let the tape run long, leave the ends stuck to the
table until the surface is covered, then with a razor blade trim to about
an inch long and fold around the wing tips before covering the opposite
side (this gets a little difficult when taping the bottom of a dihedral
wing so I lay the wing upside down on the edge of a table with half the
wing hanging off the table, then work on the half that is supported by the
table).
TIP: when trying to tape around a compound curved surface
like wing tips with packing tape it will tend to bunch and pucker. Before
pulling the ends over the wing tip, slice the edge that is hanging over
about every ½", then starting at the back, working forward, smooth
each little flap of tape over the round edge. The little flaps will
overlap each preceding flap and the curve will be much smoother.
Close up of the Z bends, notice they are bent away from the center of the servo because if you don't they will bind on the servo housing when turned.
After
the servo is cut in and you are certain of it's placement, slide it out
for a second, coat the edges of the foam pocket with silicone and slide it
back in place. Wipe the excess off and be careful not to get it on the
fuselage or wing where more tape would go. If you smear it on the wing or
fuse, wipe it off with mineral spirits.
The
radio gear will be mounted under the canopy so bore a 1/2 hole through the
fuse to route the aileron servo from the wing saddle to the canopy area.
Temporarily
tape the wing onto the fuse and install the engine. The tail group should
be glued in place and the aileron servo should be done. Balance the plane
upside down on pointed pegs at the center of gravity, Balance
the plane upside down at the center of gravity, which is 2-1/4" from the leading edge of the wing,
when measured at the fuselage. With the plane set at the balance point, tape the
rest of the radio gear, i.e. battery, receiver, and elevator servo, in the
place where they will fit nicely and maintain the balance of the aircraft.
On .25 powered planes, the balance comes out just about right if you put
the gear in the approximate locations shown in these instructions
The rough placement is a starting point and can be shifted fore or aft a bit. Use the battery and radio gear to adjust the balance point and add a little weight if necessary. The elevator servo could be cut into the side of the fuse but I like everything under the canopy. Try to make everything accessible from the canopy area. When you have determined the best positions for the servos and radio, turn the plane over, then, keeping them in about the same linier place, mark a line around them and use a knife to cut the pockets in the foam. Use a gouge to dig the pockets out and be sure to keep the fit as snug as possible. Find a convenient place for the switch. Make a hole for it or cover it with tape and use a piece of piano wire to operate it. Leave the charge cord accessible also. After the pockets are cut, if necessary, bore a hole from pocket to pocket to route wires through for a neat looking job. A 3/8" diameter tube sharpened on one end or a spade drill works great.
Servo
installation
Thread
the wires through the holes and hook up the plugs. Now is a good time to
center each of the servos and make sure of the control wire lengths.
Before sliding the servos in for the final time, coat the pocket sides
with silicone sealer. This will hold the servo in place and the silicone
is not too impossible to remove. Try not to get silicone on the plane
because tape will not stick to it! If you do, wipe it off with mineral
spirits (paint thinner). Tip: wrap the servo with tape so the silicone can
be easily peeled off if you take the servo out. If you mount your servos
externally, tape over the servos leaving the shank sticking out. I must
stress again to make the servos fit snugly. If you want them to fit flush
with the surface you are imbedding them in, you will have to create a
pocket that is sort-of two stepped to clear the mounting flanges on the
servos. This will allow the servo to sink further in and will keep the
control arm as close to the fuselage or the canopy floor as possible.
Another great idea is this: If you intend to do a lot foamie plane flying,
just cut off the servo mounting flanges and sand the bumps smooth. This
will allow the servo to slide down into a nice, neat, straight-sided
pocket. Of-course you won’t ever be able to screw the servo down again,
but if you’re really into foamies, you won’t ever need to!!!
WING
INSTALLATION
After
the radio gear is planned out and aileron servo is working properly and
not binding on anything, you can glue the wing on. I recommend using GOOP
or E6000 (industrial version). One of the reasons we use so many layers of
tape on the wing saddle and center of the wing is to keep the glue from
attacking the foam. Put a dab on the wing saddle at the front and rear. Be
sure the wing is centered and square with the fuse, then slide a bead of
Goop along both sides where the wing and fuselage meet. Let that
cure.
While
the wing is curing, the canopy can be taped up and fit. Since the radio
gear is installed, you will probably need to carve out some clearance for
servos and other gear so the canopy will fit. Cover it and set it aside as
it will be the last thing to install just before flying.
If your servo hangs through the wing, you will have to carve a little clearance into the inside of the scoop before sticking it on.
FINISHING
Now it is time to install the wing scoop. Use spray glue and
stick it into position under the wing. Dust a little 77 glue on the scoop
and after it dries, tape it up using your screwdriver to smooth it into
the corners and stick it to the wing. I run tape from the back of the fuse
over the front of the scoop to smooth everything in.
You
can decorate it with different tapes or decals. If you have a computer and
a drawing program, make up some red stars and stick them on the wings and
fuse with spray glue then tape over them with clear tape.