Flat Foamie Series

EPP P-51D Build Instructions

This version dated June 28, 2021
The Latest Version is Available Online at http://www.racores.com/FlatFoamieP-51DInstructions.htm (click on the pictures to expand) We suggest that you read through the instructions once before starting building to become familiar with the sequence of steps and the flow of construction.

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Items required to build the plane:
A Hobby Knife and replacement blades or Snap Knife
A cork backed metal ruler, 18" recommended
CA Glue (regular or foam safe) and kicker
EPP Contact Glue (we recommend Beacon Foam-Tac)
A piece of fine sandpaper to roughen the pushrod pieces for gluing
Velcro for attaching the ESC, Rx and battery.
Optional: four .032" EZ-Connectors for your pushrod attachments

Kit Contents as it comes out of the box.
  1. Take the fuselage sheet and place it on the building surface so the fuselage is upright and the nose is towards the right. You may want to put a piece of plastic or wax paper under the sheet to avoid gluing it to the building surface. Smear glue on the 500mm long 3mm round carbon fiber rod and place it into the slot down the middle of the fuselage. Since the laser cuts a slight bevel in all cuts, this will place it in the larger part of the opening. Press the rod down so it is level with the top surface of the fuselage. Also glue in place the 200mm long 7mm flat carbon strip in the lower front slot, the 250mm long 7mm flat carbon strip at the bottom rear of the fuselage (careful not to glue it to the sheet) and the stick motor mount to the front of the fuselage. Doing this in the sheet helps hold all the edges in place so it dries flat and tight. Put the other 200mm long 7mm flat carbon strip and install it in the slot in the elevator. After about 10-15 minutes go back and press the foam together around each of these pieces.

  2. Set aside the fuselage sheet to dry. Remove the wing parts from the other foam sheets gently with an X-Acto blade around the edges where they are attached to the sheets and place them on a flat building surface. Keep the wings and ailerons together as pairs.

  3. Bevel both pieces of the Aileron hinge joints. Lay the piece top side down (important for painted kits) with the hinge edge slightly back from the edge of the work surface or table. You want to cut the foam to a point but not remove any of the top paint surface. Place a cork backed metal ruler on top of the piece the same distance from the edge as the thickness of the foam. Using a new X-Acto blade or snap knife, trim along the edge/ruler at a 45 degree angle the length of the edge. If the foam starts to drag and rip, change to a new blade.

  4. Continue cutting bevels in the aileron and wing control surfaces. On unpainted kits, be careful to make left and right ailerons and the matching surface on the wings. Again, lay the top painted surface on the table through this process.

  5. Our preferred method of hinging is glue hinges and that is what we will reference in these instructions. Feel free to substitute your favorite method but you might want to do a test hinge with some of the EPP scraps in the kit to see the benefits. Check out this YouTube video to see how easy it is to make the glue hinge. http://www.youtube.com/watch?v=q0uK8KlR-0I

  6. Holding the two pieces to be hinged together with the top paint inward and the points together, smear a thin coating of Foam-Tac glue on the points of the bevels you have just cut. The hinge is best when just a fine coating of glue is used and the glue overlaps the point of the bevel about 1/8" on either side. Use what you think it too little glue and you can always add more but since it stiffens overnight wait until the next day to adjust. With the wing and aileron coated, let them dry to the touch. Place the wing and aileron on the building surface with the hinge bevel points on the top (top paint up) and slide the two pieces into contact aligning the paint. "Squish" them together gently, but firmly. Flex the hinge to make sure it moves freely. If (well, WHEN really) you apply too much glue and the joint is too stiff, slice the hinge in a dotted line to free it up. If you free it up too much, you can always add a little smear of glue. After you do a few you will get a feel for it.

  7. Working in an area large enough that the entire wing of the plane can lay flat, take the two wing panels and test fit them making note of the surfaces that make contact and spread the contact glue on both sides thinly and let it dry. Slide the wings together top side towards the table and press firmly together on the flat surface so they align and attach.

  8. Coat the carbon fiber strips with Foam-Tac glue and insert them into the wing slots and compress the foam around the carbon fiber strips to make good contact. Work your way down the joint being careful to keep the wing flat on the building surface (this is why you protected it with plastic/wax paper). Set the wing aside to dry.

  9. Remove the parts carefully from the fuselage sheet. Using the previous method, cut bevels in the elevator and stab. DO NOT GLUE THE ELEVATOR/STAB HINGE AT THIS POINT. With the stab and elevator laying face side up, hold the fuselage over them and make note of the elevator horn slot. You want to cut the rear fuselage bevel so the point is on the side AWAY from the elevator horn. Cut the rudder bevel so it matches. The rudder can be hinged at this point.

  10. Insert the elevator through the slot at the rear of the fuselage with the point of the bevel towards the top. Position it in the rear part of the cutout. Slide the stab into the front piece of the slot and gently create the hinge joint using a minimum of glue. Let dry for a few moments.

  11. Spread Foam-Tac/UHU/Welders glue on the center section of the stab, top and bottom and position it in the slot so the elevator has the same clearance on either side. Find the two 40mm long pieces of 7mm flat carbon strips and glue them in place to center the front of the stab. Place the fuselage somewhere so the stab is supported with a 90 degree angle to the fuselage and let dry.

  12. Insert the wing into the wing slot and spread glue down the top and bottom of the center section. Center the front and back nubs in the opening and place the wing and fuselage so the joint is 90 degrees and let dry.

  13. Take the plywood aileron servo bellcrank (bowtie shaped) and glue it to the existing nylon 9 gram servo arm using small screws. Position/align the center hole of the plywood bellcrank concentric with the screw hole in the nylon servo arm.

  14. With the aileron servo bellcrank mounted as shown, install the 9 gram aileron servo in the precut hole in the front of the plane. Note that the servo output shaft is towards the rear and the flat side of the bellcrank is also. Tack glue the servo in place with your preferred method, I use Foam-Tac glue on the mounting ears but other people use low temperature hot glue.

  15. Glue the elevator horn and rudder horn in place with Foam-Tac glue. The elevator horn is the one with the flat part in the glue area to be positioned against the elevator spar. The elevator horn hangs below the elevator. Trim the front point of the horn so it doesn't extend into the bevel.

  16. Glue the aileron control horns into the precut slots in the top of the ailerons so they are flush with the bottom of the aileron slot and the holes are aligned over the hinge line. Glue in place with Foam-Tac glue along the entire length. These longer horns provide support to the control surfaces.

  17. Glue the elevator and rudder 5 gram servos in the precut servo holes. Some people prefer hot glue or you can use Foam-Tac glue. You want them firmly attached. Note that the servo on the elevator horn side is inserted from the bottom and the rudder servo is inserted from the top.

  18. Measure the carbon fiber pushrods to be 1/2" smaller than the distance from the servo arm screw to the surface hinge line at the control horn as shown in the pictures.

  19. Attach the Z-bend wires to each end of the carbon fiber pushrods using the small pieces of heatshrink tubing. Note that for the tail pushrods, be sure to slip the pushrod guides/stand offs on the rods before doing the second end. ***DO NOT GLUE AT THIS TIME***

  20. Install the pushrods into the aileron horns and then with the bellcrank loose, insert the adjustable ends into the outer hole, second from the front lobes. Pop the bellcrank back onto the servo and center it and adjust the ailerons so they are level. The rods/z-bends will slip under the heat shrink tubing to allow this adjustment but also hold it in place for gluing. With paper towel or plastic under the pushrods to avoid marring the paint, glue the wires to the carbon fiber rods with CA to hold this position.

  21. Poke the pushrod standoffs into the foam at 1/3rd intervals along the pushrod to keep it from flexing in flight and glue to the foam using Foam-Tac glue, being careful not to let it get on the plywood and bond to the pushrod.

  22. Install the motor and propeller into the stick mount and position the ESC on the front of the plane. Position the receiver also.

  23. The plane is now completely assembled. Route the servo wires through a slit in the foam to the receiver side of the fuselage (we recommend putting the electronics on the rudder servo side of the fuselage to avoid interfering with the elevator arm/pushrod) and connect the servos to the receiver and using Velcro, attach the receiver and ESC to the fuselage. Use tie wraps to gather the wires in a neat bundle. Put a long strip of Velcro on the opposite side below the wing in order be able to move the battery forward and back to fine tune your balance. The Velcro will stick best to the EPP if you rub some contact glue on the area you are attaching it to.

  24. The CG of the P-51D Mustang is 2.75" back from the leading edge of the wing at the fuselage. Adjust this by positioning the battery front and back on the fuselage as needed.

  25. Control throws are a matter of personal preference. Some people want lots of surface movement to do 3D maneuvers while other people like a more docile handling plane. You can add exponential to your controls to calm down the center portion of the travel. EPP is very durable and also easily repaired. Don't be afraid to challenge yourself and learn new things. Get out and enjoy flying.