Closed Quarter Aerial Robotics (CQAR)
Figure 1: CQAR prototype
Beginners should estimate about 30 hours to complete construction after ordering everything from the parts list. It might be a good idea to order extra CF rods and mylar because they are very easy to melt when heat shrinking. This web page provides the reader with a step-by-step process on how to construct the CQAR prototype from scratch. It should be noted that if time is a major constraint (or if working with more than one person), the fuselage (steps 1-10) and the tail (steps 11-17) can be done simultaneously.
Step 1:
Cut 2" off the 1mm carbon fiber rod to make it 46". Now, bend the rod into an oval as shown in the picture below. It is important to make sure that the oval remains in a perfect plane when binding it with CA. (Hint: Bend rod in an oval on a large flat surface and place some books on top to restrain it's natural tendency to straighten.) Slightly overlap the ends of the rod, tack them with a little CA, wind a couple loops of kevlar thread around it, and CA the joint. It is not important to bend the rod into an exact oval - that will be taken care of in the next step (See Figure 2).
Step 2:
Hammer 2 nails 7" apart into your building board. Loop Kevlar thread around the nails, and knot it. Spot CA the knot to secure it. Repeat 2 times for a total of 3 loops. Now squish the CF hoop into an oval and slide one of your loops over the center with your joint at the center of the trailing edge. Slide the other two loops over the ends and position them 4.25" from the center. After checking that your wing is symmetrical, spot CA the loops to the CF rod. The oval should look like the picture below:
Step 3:
Hammer another nail that is 15.75" from the first. Make a 1/2" loop around one nail (I prefer the bowline1, 2). Run the Kevlar to the other nail and make another half inch loop to go around that nail. This important thing is to make sure the thread is tight between the 2 nails (see Figure 3). Repeat this exhausting step once more for a total of 2 loops. These are the threads that will pull the wing into the dihedral.
Step 4:
Cut 4 pieces of 3/16" long 0.8 mm CF rod. Position them 7.75" out from the center of the wing and use a glue stick to fasten them to the airfoil (it is not critical as to which way the hooks are facing as the airfoil can be flipped over before it is attached to the fuselage). After the glue has dried, wrap and CA the 4 joints. Note: This is a very meticulous step and it is a good idea to wait a good half hour for the CA to dry completely before trying to wrap the the 4 joints with Kevlar thread. These are the hooks for the dihedral thread constructed in the previous step.
Step 5:
Cut lengths of 2.2 mm CF tube 1 3/32" and 19/32" long for the wing pylons. Use the remainder of the tube as the fuselage. Note: It is important not to cut the fuselage to the length shown on the plans because you might need that extra length later when determining the CG. Attach the shorter wing pylon 6" from the tail end of the fuselage tube. Measure your wing chord and position the longer wing pylon exactly this distance from the rear pylon. CA the joints and when they have dried, remove them from the board and wrap and CA the joints.
Step 6:
Position the fuselage with the wing pylons facing vertical. CA the wing on top of the wing pylons with the joint at the trailing edge and the dihedral hooks facing downward towards the fuselage. Note: Do not wrap and CA the joints yet.
Step 7:
Measure the distance between the top of the wing pylons and cut a length of 0.8 mm CF rod to go between them. CA a 1/2" length of 0.8 mm CF rod 2 5/16" back from the leading edge to the rod that is to go between the wing pylons and then wrap and CA the joint. This will be the plane's center of gravity. CA the assembled CG rod to the wing pylons. After it has dried, wrap and CA the joints. The finished frame should look something like the picture below:
Step 8:
Cut out a rectangle of RA microlite so that it's about .5" bigger then the oval wing. Tape the microlite with the shiny surface facing down on the building board. Touch the top, bottom and outside edges of the wing (not the CG rod) with a gluestick. Lay the wing down on the RA microlite with the fuselage up. Remove the tape from the microlite and push the extra microlite over the bottom of the CF rod, moving around the outside of the wing until the covering is firmly attached to the rod. Let it dry for 24 hours.
Step 9:
Cut the excess microlite off with a sharp hobby knife, getting as close as you can to the CF rod. Then, put the dihedral into the wing by putting one loop over one of the hooks and place the other end of the loop around the hook that is diagonal to it. Repeat this for the second dihedral thread. After checking that the dihedral is symmetrical (both wingtips are the same distance off the ground), CA the point where the threads cross.
Step 10:
The last step in building the fuselage and wing is to heat-shrink the RA microlite with a sealing iron. Note: If you touch the CF rods with the iron, they will melt!!! If you ordered the sealing iron from my parts list, I recommend setting it to 385 degrees Fahrenheit. 2 degrees more and it will melt the covering; 2 degrees less and it won't shrink at all. Try it out on a test sheet first.
Step 11:
The next step is to build the tail. I cut out the elevator shape from the plans and taped it to a 1/16" piece of contest grade balsa. I traced around the cut out shape and in the 1/16" gap between the control surface with pen and pressed very lightly with my sharpened brass tubes over the lightening holes to mark their outline on the balsa. Then, when I removed the cutout of the elevaotor, the shape was traced on the balsa along with indentations for the locations of the lightening holes. The next step is to totally remove the holes using the copper tubes by either pressing firmly with a twisting motion or to just position the tube over the indentation and hit it firmly and quickly with a hammer. This usually does the trick if the tube is sharp enough.
Step 12:
Now cut out the elevator shape with a sharp hobby knife, including the 1/16" gap that separates the elevator and control surface as well as the 1/16" slots for the rubber band hinges (so you now have 2 pieces). Fit the 2 separate pieces back together, except with a 1/16" piece of balsa wood between them. Once they are aligned with the piece of balsa in the middle, put a piece of tape there to hold them together. Now cut out a piece of RA microlite in the exact shape of the elevator and use a gluestick to attach it to the side without the tape. Turn the elevator over, remove the tape, and cover that side with a piece of RA microlite that is a little larger than the actual size of the elevator. Wrap the overlapping piece of microlite around the edges of the elevator.
Repeat steps 11 & 12 with a 1/32" piece of contest grade balsa for the rudder.Step 14:
Cut out the hole for the actuator using the 13/32" brass tube, centering it exactly in the middle of the balsa spacer. Now cut through the microlite to reseparate the control surface and remove the temporary balsa spacer. Finally, trim an extra 1/16" around the cutout for the actuator on the control surface. Again, you should have 2 separate pieces as shown in the figure below.
Cut 2 pieces of rubber band (supplied with the RFFS-100 receiver) to fit in the hinge spaces and long enough so the 1/16" gap remains. Apply CA only on the very tips of the rubber band and position it in the slot. Note: A common error is to apply to much CA on the rubber band making the hinge too stiff to deflect the full 45 degrees in each direction.Step 16:
CA the actuator to the elevator/rudder (not the control surface) with the actuator leads coming through the cutout as shown in the picture below. It is important to make sure that the actuator is centered on the elevator plane before CA'ing in place.
Use the blue wire supplied in the receiver package to install the magnets. First, put a drop of CA between 2 of the 4 magnets to hold them in place (repeat this for the other 2 magets). Then, strip a length of blue wire long enough to wrap once around the circumference of the magnet. Wrap the stripped wire around the magnet and CA the wire in place. Bend the wire to position the magnet so that it is in the center of the actuator coil, with the cylindrical axis of the magnet parallel with the plane's fuselage. Once you are certain the magnet is in the center of the coil, stick the other end of the blue wire through the control surface to hold it in place. After again making sure the magnet is centered, CA the blue wire to the control surface. Note: At this point, you should test the control surfaces to make sure they are getting the full deflection before you glue them to each other or the fuselage.
You now want to glue the rudder and elevator together making sure they are at a 90 degree angle to one another as shown in the picture below. Note: You do not want the flat end of the rudder hanging over the elevator because it will prevent deflection in the upward direction.
Finally you want to attach the tail to the end of the fuselage as shown in the picture below. Again, make sure you do not position the tail so that the elevator's control surface is obstructed. The piece of balsa that sits under the elevator is used to protect the tail when landing. Build this piece using 2 1/32" cross laminated balsa to the dimensions shown on the plan.
The next step is to construct the landing gear for the CQAR prototype. The landing gear consists of 2 plastic wheels (or balsa if you wish to go lighter), 2 pieces of 1/2" piano wire, and 2 pieces of 0.8mm CF rod. The 0.8mm CF rods are arranged in an inverted "V" right in front of the leading edge pylon and are wrapped with Kevlar and CA'd to the fuselage as seen in the figure below. Bend the piano wire at an angle of approximately 130 degrees and slide one end through the center of the wheel. Making sure the other end of the piano wire is parallel with the inverted "V" of the 0.8mm CF rod, wrap and CA them together. Repeat this process for the other wheel.
 Step 20: Landing gear |
 Step 20: Wheel fastened to piano wire |
The receiver is mounted on cross-laminated 1/32" balsa and is stuck onto its mount with a strip of double-sided foam tape. The Dynamics Unlimited actuator leads are not long enough to reach the position shown on the plan, so I stretched them (leaving a little slack in the lead) as far as they would go. The leads to the actuators are specially made so that you can just plug them into the receiver (no soldering is necessary). However, the leads that go to the battery and motor should be soldered. For the battery leads, I soldered a female JST connector to the receiver for easy attachment/removal of the battery (I kept this JST connector at its original length). I soldered two regular wires for the motor leads (the lighter the wire the better!). These wires I kept extra long because I wasn't sure where the motor would be positioned just yet to balance the CG. The antenna is a 15" piece of .33mm guitar string. I had my antenna positioned so that it first went towards the front of the fuselage, wrapped around the top of the airfoil and stuck it through the front end of the elevator balsa. Once everything was secure, I CA'd the antenna in place.Step 22:
The motor, propeller, gearbox and battery are the last thing to be mounted onto the CQAR prototype. They have to be positioned precisely so that the CG is balanced. I recommend first building the motor and gearbox mount. To construct the gearbox, you first want to slide the pinion gear onto the motor shaft (it is a press fit so no glue is needed). Likewise, the spur gear and two ball bearings have to pressed onto the prop shaft. Then follow these steps:
 Step 24: Gear drive plans (click to get actual size printout) |
 
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Once the motor mount is finished, I recommend gently placing it, along with the battery, on the end of the fuselage to get a good estimate of where these components should be placed to balance the CG. Once the position is known, mount the battery onto the fuselage using two-sheet cross-laminated 1/32" balsa and some magnets. CA 4 magnets onto the battery and 4 to the balsa mount in a rectangular shape and make sure they line up. To ensure they lined up correctly, I glued 4 magnets to the battery, placed the other 4 on top of the magnets that were already on the battery, then glued the battery mount to the batteries. Once the glue has dried, you should be able to remove the battery mount from the battery by just detaching the magnets.Step 24:
There are two things to be accomplished when attaching the motor mount to the fuselage: (1) make sure the propeller shaft is parallel to the fuselage or at a slight downward angle (2 degrees or less) (2) the plane is balanced about the CG.Step 25:
The final step is to glue the male JST connector to the battery leads. Since the female connector was kept at its original length, this one will have to be shortened.