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Rotor Build Part 5: Conclusion
Posted by J.S. Decker on May 9, 2008, 19:27
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This is the final part of the Rotor build log. I have not included much detail on finishing, but I have also included a couple a photos from taken while finishing the fuse and LE’s of the wing and stab.
- Root to Fuse Fit: Tape the root of the wing, use pencil glued to a piece of wood mark the outline of the fuse on the wing root, and sand the wing root match the sides of the fuse.
- Root Felt: Create the outline of the root airfoil and carry through tube onto a piece of paper tack glued to the root with a light dusting of 3M77 spray adhesive for each side by rubbing transfer using a piece of white paper and a pencil. Cut the outline out of the paper with scissors and an Exacto knife, apply the outline to the felt with 3M77 spray adhesive, and cut out the felt. Set the felt aside, until the torque tubes are installed in the wings.
Some folks use washers as spacer between the wings and fuse. I like to use felt, the felt holds the wing from the fuse to prevent binding and seals the gap for a cleaner aerodynamic intersection.
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| Wing tracing. |
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| Wing root felt pieces cut to size. |
- Finishing: For the fuselage and canopy, tape over the wing rod holes, canopy and any other opening, lightly wet sand the fuse with 320 or 400 grit paper, fill the obvious low and rough spots with a finishing filler, wet sand the filler out, prime the fuse, wet sand, fill, wet sand prime again as necessary, and apply a final finish coat of paint. Lately I’ve been using a polyester resin finishing filler, like “Icing”, and Duplilcolor rattle can primer and paint.
For finishing wing and stab LE’s, I’ve been filling taping off the LE’s, filling with finishing filler, wet sanding, and coloring the LE with a Sharpie permanent ink pen.
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| Wing LE taped off prior to being filled with polyester finishing filler. |
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| Wing LE filled with polyester finishing filler. |
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| Wing LE sanded out and ready to colored with a Sharpie pen. |
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| Stab LE filled with polyester finishing filler. Ready to be colored with a Sharpie pen. |
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| Stab leading edge colored with a black Sharpie pen. |
- Torque Tubes: Sand outside surface of the torque tube and the inside surface of the wing tube. Install the torque into the mono-block, hold the felt the fuse, and use a piece of tape to mark where the depth that the torque tube should be glued into the wing. This is a critical measurement, but if your measurement is going to be off, you want the amount the torque tube sticks out of the wing to too much than not enough, because you can trim the torque on the disk sander if you need to. I’ve always got the measurement correct using a piece of tape to mark it.
Pull the torque tube out of the fuse can wrap a tape flag around the torque tube on the other side of the marking tape, and then remove the marking tape. This flag will be the depth gauge you use to insert the torque tube into the wing tube.
Use an adhesive to glue the torque tube into the wing tube up to the tape depth gauge. You can use epoxy, golf club shaft epoxy is good, or a sleeve retaining compound like Loctite 680.
Apply the felt to the wing root after gluing the torque tube in place. Typically I use felt with an adhesive backing, but regular felt can be applied with spray adhesive.
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| Torque tubes. The lower one has the position marked for depth flag. The top one has the depth flap attached to the tube. |
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| Torque tubes with depth flags just prior to being roughened and installed in the wing with Loctite 680. |
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| Dowel with sandpaper flapper that is used to roughen the inside of the brass tubes installed in the wing. |
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| Torque tubes installed and felt applied. |
- Control Linkage: Mount 2-56 ball links to the servos, drill the shank out for a 4-40, thread the shank 4-40, and connect the servos to the driver arms with 4-40 all thread. I use the 2-56 ball links on the servos because they are easier to mount to the arms and it is easy to drill and thread the shank for 4-40 all thread. I have found the pushrods for the Rotor to be short enough that the all thread does not need to be reinforced.
- Radio Bits: Wrap the battery in foam, inserts battery into the nose, and fix the receiver to the top of the nose section with Velcro to keep it out of the way when inserting and removing ballast.
- Switch and Charge Jack: A small bracket is built from precured CF and power switch and charging jack are mounted in the bracket. I use precured CF because I have it and totally for bling value. The bracket is secured in the fuse with Velcro for convenience.
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| Completed installation, the switch and charging jack in visible on the left. |
- Balance: Balance at 26% for the first flight (typically the CG should between 25 and 30 percent MAC).
- Incidence: Set the wing 1.5 degree positive relative to the stab.
- Throws: Set the aileron throw to 15 degrees and the elevator throw to 10 degrees. I typically use -60 percent exponential on ailerons and -50 percent exponential on elevator with my Multiplex mc 4000.
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| Plenty of throw available with the balllinks installed in the inner most hole, which is at a 10mm radius. |
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| All done! |
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| Comparison of the Ultron and Rotor. |
Rotor Build Part 1: Preassembly and Component Weights
Rotor Build Part 2: Pitcheron/Wingeron Hardware Installation
Rotor Build Part 3: Fin and Stab Installation
Rotor Build Part 4: Internal Bits
Rotor Build Part 5: Conclusion
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