Iron Cross Mini Instructions

The Iron Cross Mini is smaller version of our Iron Cross kit. Based on a secret WW1 German rocket powered monoplane, It features a low mounted bird shaped wing with dihedral and scaloped trailing edges, a ww1 era styled vertical stabilizer, 18mm motor mount, 40mm white tubing for the body and 6mm depron wing and tail surfaces. Spars are pre-installed, elevons are pre-hinged, body tube is pre-slotted for the stabilizer and the rail button holes are pre-cut. You will need two 8-10 gram or lighter servos, two 3″-6″ lightweight servo extensions, a receiver, and a small 500mah single cell lipo battery or smaller. You will need a transmitter with delta wing/elevon mixing and a flap trim function or flight modes to pre-set boost and glide trims. Excellent cut vinyl decal sets are available HERE: in german or US marking styles. Make sure to select the SMALL version for this kit. Specs: 21″ length, 15″ wingspan, 5 oz rtf, for 18mm D-2.3T and C3.4T reloadable composite motors only.

CG location for rocket powered vertical flight: 8.25″ measured forward from the rear end of the main body tube assembly with motor and battery installed ready for flight.

Please refer to the General Information Link above then read the instructions completely before starting assembly. The assembly photos are for general reference but may not include every step in the instructions. If you want hardcopy to work from, all you have to do is click/drag/select and copy all of the text below, open word and paste with “keep original format” and it looks exactly like it does online then you can print it.

Unpacking your kit:

The kits are packed to protect them in shipping, but the contents are fragile so unpack carefully. Carefully cut the tape holding the tubes in the box, then unwrap/lightly cut the plastic wrap to free the tubes, the spar may be packed in the tubes and the baggie with the little parts and nose cone will be in the tubes as well. Carefully cut the tape holding the cardboard wing protector in the box and carefully remove it, don’t pull hard or bend it. Then carefully cut the tape holding the cardboard top piece to the bottom. There may be some sticky tape holding the cardboard to the bottom cardboard piece, carefully peel it being sure not to bend anything. Once the top cardboard is free you can see the foam wing/tail parts, there are little fragile pieces in here, so unwrap carefully. It may be best to use an exacto to lightly cut the plastic wrap and carefully remove it without cutting into the foam. Make sure everything is free before you remove the pieces to avoid breaking anything. Kits contain one or two scrap pieces for repairs if you damage anything in construction or flight, just cut and patch in a spare piece of the foam if needed using foam safe CA+.

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.

Orbital Transporter Mini Rocket glider instructions

Identify all pieces, the kit should contain:

1 wing taped together

1 Nose Cone

1 vertical stabilizer

2 control horns w/pushrods

3 2.75″ long foam strips for centering the motor tube.

1 Body Tube

Motor mount

Velcro(for battery and rx/bec attachment)

2 Rail buttons with t nuts/screws

Lead weight

Spare depron

Notes before starting:

Reference to glue, CA, or 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. Epoxy is not needed in this model. It is designed to be assembled ONLY with Bob Smith foam safe medium thick CA+ and accellerator or equivalent. 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. It is better to move the battery and rx forward or rearward slightly before permanently mounting the rx and battery with velcro than adding any nose or tail weight.

I think rounded flight surface edges look much nicer on this kit and helps performance slightly. If you decide to sand the edges, use a block and a VERY light touch and do small areas at a time to avoid the paper catching the foam and tearing it. I recommend 320 grit. Do any shaping of the wing and tail edges before assembly.

Assembly:

The wing will be unfolded and mounted on the bottom of the body tube.
Lightly sand the bottom fuselage wing line and apply a squiggle of glue about 1/2 wide to the body tube wing line, the wing joint, and 1/2″ on either side of the wing joint.
Lay the wing upside down onto the body tube making sure the rear of the wing is even with the rear pencil mark on the bottom of the tube and the front and rear alignment lines are in line with the taped wing joint. You want to be sure the wing makes full contact with the body tube and is set before you continue. The wingtips should be about 1″ from the table top on both sides, the actual dihedral isn’t super critical you just want it symmetric. Hold the wing down for several minutes till the glue is set.
Apply some glue into the wing/body tube joint on both sides to make sure is is secure, I squeeze a bit in every inch or so.
If not installed for you install the t-nuts and rail buttons into the pre punched holes in the long forward tube. The t-nut goes on the inside of the tube then slide on a washer, the collar and another washer on the outside and hold it in place with the machine screw
Test fit the vertical tail into the slot and make sure it fits. Glue into the slot using foam safe CA+ making sure the tail is perpendicular to the wing and is straight. You can correct any small offset when you glue the motor mount in place.
Glue the foam centering strips on the motor mount tube. You will glue two strips on either side and one on the bottom using the marks on the tube. For flight you will use a small amount of masking tape to friction fit the motor from falling out after burnout.
Test fit the motor mount, It will slide under the vertical stab tab. If you need to sand the tabs glued on the motor tube so that it fits under the vertical fin tab, do so carefully till it will insert fully and is recessed so the rear of the motor mount is even with the rear of the vertical stab tab. Make sure the vertical stab is still perpendicular and then glue the motor mount into the rear of the model.
Glue each control horn/pushrod in place on the bottom of the control surface using the pre made holes. The control horn holes should be pointing toward the front of the model and the pushrod should be closest to the center of the model and angle inward toward the center slightly. There is a left and right pushrod, see picture for clarity. Repeat on the other side.
Put some CA on the top of the control surface where the horn prongs stick through, this locks it in place

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. Use a servo arm at least 9/16” long and with holes small enough that there won’t be slop with the pushrod wire when installed. I use the hole furthest out on the servo arm, to maximize movement. On some servos there are a long two-ended servo arm, you can trim off one end if needed to get sufficient length. Zero out any trim settings on the transmitter. The model once the motor has burned out is nose heavy and flying wings lose pitch authority when nose heavy so you want as much up elevator travel for trim/flare as possible.

Connect a servo to each pushrod. If the pushrod is too tight, you can use twist an exacto knife in the servo arm hole to make it larger, but be careful and do not make it too large. Once connected, tape each servo in place so that the control surfaces are centered. Flip the model right side up and look at it from the rear. Moving the transmitter stick back(up elevator) should move both elevons up. Moving the transmitter stick to the right should move the right elevon up and the left elevon down. If you can’t get the servo reversing to give you the right polarity try swapping aileron/elevator inputs to the receiver or turning the servos over and swapping the servo arms to the other side of the output shaft. If that is correct, continue. Note, I mount the servos on the bottom of the wing which prevents them from interfering with the launch rail and I think this looks better and I have NEVER had any issue with servo damage landing since these models land so slow and are so light.
Flip the model upside down and supported. The servos may be attached to the model using double back servo mounting tape(not included) or by directly gluing the servo to the wing with CA+ or a small amount of epoxy. Double back servo tape can loosen over time and with exposure to heat, I prefer to glue the servo in place. With the radio still on, put a small amount of glue on the servo, being careful not to get any near the output shaft. And set it in place on the model keeping the control surface centered. Do the same to the other side. Make sure the glue is set before continuing. The servos should be mounted just next to the tape on the wing joint.
Flip the model back right side up. Make sure the control surfaces are centered, use trims if needed. Now measure the control surface movement. Full elevator movement should be 5/8” in each direction, aileron movement should be 1/4″ in either direction. 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 1/4” of up elevon during glide. You can also use flight modes to set individual elevator trim settings so that you get boost and glide elevator trim when you switch between flight modes. 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.
Depending on your servo wire length, you may need to attach a 3″-6″ lightweight servo extension to each servo. You just need to be able to route the wire to the front of the tube to attach it to the receiver. Use the lightest and shortest you can get away with.
Make a 1/8″ wide by 1/2″ long slot in the bottom of the wing/fuselage in the center and pass the wires through to the inside and toward the front. You can cut a small plug to fill the slot using the spare depron included in the kit and push it in place to hold the wires from moving.
Attach the servo wires to the receiver and make sure they are going the right direction.
Use the remaining velcro to attach the battery inside the nose shoulder at the bottom. You may want to wait to permanently mount the rx or battery till you have balanced the model, shifting these two around slightly will help avoid nose weight. You can remove the receiver case to save weight if needed to balance the model.
Use a black sharpie to add panel lines if desired
To apply the red and silver wing and tail stripes you’ll need to remove the stripes one at a time from the backing and transfer material and press them down onto the wing and pull and curve them so they follow the curved corners.
If you use the stickershock vinyl, once applied, use a hair dryer on hot to soften the vinyl and press it down into the foam and cardboard surfaces and it will adhere very well. Make sure not to warp the foam especially on the vertical stab.
I did not paint my nose cone but you can do so with any type of paint. See the general instruction tab on correct paints to use on foam.
Install the battery and insert a loaded rocket motor into the motor mount.
Support the model upside down at the balance point indicated for boost. Move the battery and receiver around to achieve the correct boost CG and secure them in place with the supplied velcro. If required, glue pieces of the included lead weight in the nose or tail as needed to balance it. 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 the model is nose heavy you may consider removing the receiver case which will save 3-4 grams.

Flying: See the General 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.