Flat Foamie Series
EPP Spitfire Build Instructions
The Latest Version is Available Online at http://www.racores.com/FlatFoamieSpitfireInstructions.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
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 (Foam-Tac, UHU por or Welders)
A piece of fine sandpaper to roughen the pushrod pieces for gluing
Optional: four .032” EZ-Connectors for your pushrod attachments
1. Remove the parts from the 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. When you separate the wing pieces, keep the wings and ailerons together as pairs.
2. Bevel both pieces of all the hinge joints. Lay the stabilizer 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 stabilizer 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. Cut the elevator in the same manner. Cut bevels in the elevator counterbalances to prevent binding.
3. Continue cutting bevels in the aileron and wing control surfaces being 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. Do not cut the bevels in the fuselage or rudder at this time.
4. 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
5. Holding the two pieces to be hinged together with the top paint inward, smear a thin coating of Foam-Tac/UHU/Welders glue on the points of the bevels you have just cut. Start with the elevator and stabilizer. 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. With the stab and elevator coated, let them dry to the touch. Place the stab and elevator on the building surface with the hinge bevel points on the top (top paint up) and slide the two pieces into contact. “Squish” them together gently, but firmly. Flex the hinge to make sure it moves freely. This joint will strengthen overnight. Continue with the hinging of the ailerons.
6. Once all the elevator and ailerons have been hinged, it is time to do the main assembly. Working in an area large enough that the entire outline 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.
7. Insert the carbon fiber strip into the wing slot and while lightly compressing the foam around the carbon fiber strip, wick CA into the joint and use kicker to make it seal. 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). Once you have applied glue to one side, flip the wing over and apply glue to the other side also to firmly attach the wing support.
10. Attach the rear horizontal fuselage piece to the rear of the wing in the same manner.
11. Take the stab/elevator assembly and making note of the wing hinge line (we consider the side with the smooth joint the top and the side with the bevel to be the bottom), attach it to the rear fuselage piece in the same way with the hinge facing the same side as the wing (both up or both down).
12. There is a small piece of flat carbon strip in the kit which can be optionally used to further reinforce the nose of the plane. Just cut the carbon in half and cut slices into the nose area as shown and CA in place.
15. Once your paint is dry, remove the fuselage halves from the foam sheet and bevel the rudder hinge joint. Check the elevator horn slot position. You want the point of the rudder hinge bevel on the side opposite the elevator horn slot. This allows your rudder horn and servo to be on the side opposite the elevator servo. Make sure that you bevel the same sides of the rear fuselage and rudder. Do not hinge the rudder at this time.
16. Place the plane outline subassembly with the smooth hinge joint/top paint surface down on the building surface so the V bevel is facing up. Find the fuselage bottom and test fit it into the notches on the outline. Smear glue on the two pieces and attach the fuselage bottom in place making sure it stands perpendicular to the horizontal surface.
17. Find the two thin (3mm) wedge shaped EPP tail stiffeners. These are glued to the bottom of the fuselage at a 45 degree angle to form a triangle cross-section with the fuselage bottom and horizontal outline that is even with the rear fuselage bevel. This will prevent the tail from twisting in flight, so it is important to complete this step flat on the building board to maintain the alignment.
18. The large end of the wedge should face the front/wing end. Dry fit the wedge in place so you have an idea of where the glue should be spread and attach one of the thin wedge shaped pieces to each side of the rear fuselage. This is a good place to take a break and let all the glue strengthen.
19. Take the plywood aileron servo bellcrank (bowtie shaped) and glue it to the existing nylon servo arm using CA. Rough the surface of the nylon servo arm with sandpaper first. Position/align the center hole of the plywood bellcrank concentric with the screw hole in the nylon servo arm. If you are using the 9 gram HXT900 servo included in our completer kit you will find alignment holes in the bellcrank that either the .032” z-bend rods or #1 screws can be used to align the bellcrank. We have cut the center hole to be snug on the servo arm and attach under the arm.
20. 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.
21. Using a small piece of the flat carbon fiber, cut a slit in and reinforce the area over the top of the aileron servo cutout in the top fuselage. Extend the piece beyond the cutout to reinforce it in the case of hard nose in landings.
23. Insert 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 CA along the entire length. These longer horns provide support to the control surfaces.
24. Put the elevator and rudder servos in the precut servo holes just behind the wing spar. Glue the servos in place. CA can be used, some people prefer hot glue or you can use contact glue. You want them firmly attached.
25. Find the materials for the pushrods and bend adjustment angles into half of the z-bend wires. I do these bends with a set of rounded needle nose pliers but V shaped bends are just as good. Following this method you will probably never need to do any adjustments that way.
27. Insert the shorter pushrods into the anti-differential bellcrank on the aileron servo. Note that the pointed lobes on the bellcrank face forward. This bellcrank provides a perpendicular connection from the servo pivot to the control horn giving the same up and down throw to the ailerons. Without it the angle would cause mechanical differential. Cut the pushrods 1/4”-1/2” back from the aileron hinge line with the bellcrank centered.
28. Remove the pushrods from the plane and use heat shrink tubing to attach two of the remaining straight z-bend wires to the cut ends. Do not glue the wires in place. This will allow us to do the fine adjustments of the pushrod lengths. You should end up with pushrods that look like this.
29. 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.
31. Locate the elevator horn and glue the horn in place using Foam-Tac or CA so the holes are aligned over the hinge.
34. When the tail pushrods are completed and installed, poke and glue (Foam-Tac) the standoffs into the foam at 1/3rd distances from the ends. Adjust the depth of the standoffs to hold the pushrods as straight as possible from end to end.
35. Using the short carbon fiber cutoff pieces from making the aileron pushrods, cut diagonal slots in the foam between the rear fuselage and front of the stabilizer long enough to insert these pieces and glue them in place using CA glue. This helps prevent the stabilizer from skewing with full elevator deflection.
36. 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 CA, being careful not to let it run up the plywood and bond to the pushrod.
38. The plane is now completely assembled. Route the servo wires through a slit in the foam to the receiver side of the fuselage and connect the servos to the receiver and using Velcro, attach the receiver and ESC to the fuselage. Put a long strip of Velcro on the opposite side below the wing spar 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.
39. Use tie wraps to gather the wires in a neat bundle.
40. The CG of the plane is on the carbon wing spar to 1/4” behind it.
41. 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.
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