Mig 21 Instructions

Radio Controlled Rocket Glider Kits

Mig 21 Rocket Glider Kit

The Mig 21 RC Rocket glider kit. It comes with a plastic nose cone, 2.6" white tubing for the body and depron wing and full flying tail surfaces. Construction is slightly more complicated since you have to cut the slot in the tube for the wing after you join the two body tubes. You will need two 10 gram type servos, two 12"-18" servo extensions, a receiver, and a small 500mah single cell lipo battery. You will need a transmitter with delta or elevon mixing. Please refer to the notes on items needed for completion and flying, then read the instructions completely before starting assembly. The assembly photos are for general reference but may not include every step in the manual.

CG location for rocket flight: 7 3/4" forward from the TE of the wing or 6.75" from the LE of the wing, it should be the same point.

Welcome to the world of rocket boosted radio control gliders. This is not a model for a novice RC pilot, but anyone who is comfortable with RC flying of a medium speed model should be fine. Read through the instructions, look at the photos and be sure you understand the step before commiting to cutting or glue.

Mig 21 Rocket glider instructions

Identify all pieces, the kit should contain:

1 wing taped together

1 wing spar(carbon fiber)

2 pushrods

1 vertical stabilizer

2 horizontal stabilizers

1 tail pivot rod

1 tail pivot tube

1 tail pivot rataining ring

1 plastic strip for reinforcing ventral fin.

2 ez connectors

2 Body Tubes

Motor mount

1 Ventral

1 Spine/canopy piece

1 nose cone

Velcro(for battery and rx/bec attachment)

2 Rail buttons with t nuts/screws or 1 Launch lug

1 landing skid

3M blenderm tape

Lead weight

Spare depron

Notes before starting:

Reference to CA+ means foam safe CA+, normal CA+ will melt the foam! Normally you need to use accelerator to get the CA to set on the foam since there is nothing for it to soak into and activate.

You may use 220-320 grit sandpaper and a sanding block to slightly round the edges of the foam if you prefer that look. It will not markedly impact the flight performance either way. Be very careful and use a light touch, it is very easy to catch the foam on the edge of the paper and tear the foam. Do any sanding before assembly.

Epoxy is not needed in this model. Weight is critical and the model is designed for the thrust and flight loads. Weight in the rear end is bad and will require additional weight in the front of the model.

Assembly:

Unfold the wing and glue it using CA+ at the taped joint, make sure it is flat.
Glue the spar into the slot in the bottom of the wing using CA+ then tape over the spar and the center joint using the blenderm tape.
Join the two body tubes. Make sure the arrow mark on bottom of the forward tube lines up with the arrow mark on the bottom of the rear tube(rear tube has the coupler glue in and has the slot for the tail pre-cut), this will make sure the wing cutout lines are aligned. Use glue sparingly since you have to cut through the coupler for the wing slot.
Carefully cut out the wing slot on the lines marked. Lines are approx size. Make sure to check the wing thickness and don't cut the slot too oversized. Take your time and go slowly. It's easiest to do this using a piece of angle aluminum to help keep the line straight. Test fit the wing into the slot carefully. Sand or trim as needed for a good fit without dragging/damaging the foam.
Make sure the wing is centered in the body tube and glue using CA+ along the top and bottom on both sides. use CA+ and accellerator. You can squeeze the tube slightly as the glue sets to make sure it makes contact and doesn't have a gap.
Cut the pockets in the body tube on the underside to fit your servos. the approximate position is marked. Note the ez links go on the inboard side toward the body tube. Connect your servo extensions and route them into the body tube, make sure they go far enough forward to stick out of the end of the tube to connect to your receiver. Glue the servo to the bottom of the wing as far into the body tube as possible so that the pushrod will clear the stabilizer when it moves and the ez link won't rub on the body tube when installed. The servo wire should point forward toward the front of the model when you insert the servo into the tube to reduce the need for extra servo extension length.
Install the vertical tail. Sand the slot or tab slightly if needed so that it fits. Glue in place with CA+ and add a light fillet. Make sure the fin is straight and perpendicular to the wing, use the internal line on the inside rear of the body tube to help with alignment.
Glue in the pivot tube into the rear of the body tube, centered. reinforce with CA+ on inside and outside of the tube.
Shape and then glue the canopy/spine foam piece in place, it butts against the vertical stab.
Make a hole in the bottom of the rear of the body tube at the place indicated for the rail button and install it using the T nut. Don't tighten down really hard, just enough to secure it.
Install the forward rail button on the mark indicated in the same manner. Note the rail buttons are offset so that the rail will just barely clear the ventral on one side and the servo/stabilizer control horns on the other, check fit with your rail and check for clearance. Trim excess servo or vertical stab horn material if needed. once tail surfaces are installed.
Using a tool make two holes for the front skid and glue in place. Make sure the front skid isn't so far forward so that it doesn't interfere with the nose cone shoulder.
Shape and install the ventral even with the end of the body tube on the bottom. A piece of styrene strip included can be glued on the bottom of the ventral to protect it from landing damage.
Glue in the motor mount into the tail, in the slot in the fin tab as far forward as it can go. Center the tube left and right in the slot before gluing. Run a bead down the joint on each side using CA+.
Insert a pushrod into the third hole from the end in each control horn. The pushrod should go into the inboard side of the horn.
Slide the pivot rod through both surfaces and the body tube, make sure the control horns are pointing down. Once installed, slide the small aluminum tube over the end of the pivot rod and CAREFULLY put a small dot of CA+ on the end of the rod and little ring and set it with accellerator to lock it in place. Be careful that you don't get any on the moving surfaces. Make sure the surfaces are free to move.

The basic construction is now complete.

Radio Installation

Note: Your radio needs to be configured for Delta mixing, this means that the servo arms will move the same direction during elevator stick movement and opposite for aileron stick movement. Connect your servos to the receiver one in the aileron connection and one on the elevator connection and apply power. Remove the servo arms from the servos. Use a servo arm at least 9/16” long. I use the hole furthest out on the servo arm, to maximize movement. Install the ez links on the outermost hole in the servo arm from the inside of the arm, you may need to enlarge the servo arm hole so that the ez link rotates freely. Zero out any trim settings on the transmitter. Slide the servo arms onto the servos. so that they point down toward the ground.

Flip the model right side up and look at it from the rear. Moving the transmitter stick back(up elevator) move both servo arms toward the rear of the model. Moving the transmitter stick to the right should move the right servo arm toward the rear and the left servo arm toward the front. If you can’t get the servo reversing to give you the right polarity try swapping aileron/elevator inputs to the receiver. Once correct, continue.
Once the servos are centered, route the pushrods into the ez links, center the control surfaces and tighten down the ez link screws, if you cannot reach the screws fully, make a mark with a pen on each side of the ez link on the pushrod to mark the location then remove the servo horn and tighten down the ez link screw and reinstall the servo horn. Note the ez link is closest to the body tube to make sure the pushrod clears the control surface when moving. Make sure that the pushrods don't interfere with the stabilizers. If necessary bend the wires or trim the inboard edge of the control surface for clearance.
Flip the model back right side up. Make sure the control surfaces are centered, use trims if needed or adjust with the ez connectors. Now measure the control surface movement. Since the model will be nose heavy, extra elevon movement helps to give sufficient authority during glide.
If you have a flap/elevator mix you can program up elevator to a switch setting. The model needs approximately 3/4" of up elevon during glide and may need some down/roll trim for boost depending on how you built your model. If you can’t set the up elevator trim to a switch on your radio you’ll have to manually put in boost and glide trim which is hard to do while flying the model.
Use the included Velcro to attach the receiver 1.5" from the front of the body tube on the top(or enough to allow the wires to clear the shoulder of the nose cone). This allows you to be able to remove and replace the receiver if needed for repairs or for removing the servo wires. I attached the battery inside nose cone on the shoulder.
Insert your heaviest loaded rocket motor into the motor mount
Support the model upside down at the balance point indicated for boost. I use two pencils with the eraser pointed up and held in place with a small hand vice. Place the model upside down on the pencil erasers on the balance point indicated in the kit spec sheet. Use the included lead weight to balance it either in the nose or tail as needed. Do not try to fly the model with it balancing it behind this point. The adage is, a nose heavy model flies poorly, a tail heavy model flies once
If you paint the model, make sure you test it on scrap foam first.
If you are going to paint the model, you can mask off the servos. Make sure no paint will get on the servo output arm. Make sure to test the paint on a scrap piece first to ensure it won’t melt the foam. I use Model Master(testors) or testors small rattle cans for painting directly on the foam.
Use a black sharpie to add panel lines if desired, I ran a fine line sharpie into all the panel lines in the nose cone and it really sets it off.
I used vinyl trim for the canopy and tail markings, it helps to use a hot hair dryer to heat the decals and then push them down into the paint to make sure they adhere well.
Re-install the receiver and battery

Flying: See the Instruction/Information link at the top for flying instructions. Be ready on the first few flights to keep the model straight till you have the trims set perfectly for boost and glide.