3D Delta XL Instructions

This version dated May 8, 2021
The Latest Version is Available Online at http://www.racores.com/3DDeltaXLInstructions.html (click on the pictures to expand) We suggest that you read through the instructions once before starting to build 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 (Beacon Foam-Tac)
A piece of fine sandpaper to roughen the pushrod pieces for gluing.
Velcro for attaching the ESC, Rx and battery.
Optional: Three .032" EZ-Connectors for your pushrod attachments
  1. Remove the pieces from the sheets to assemble the subassemblies shown above. Glue the fuselage top (A1+ A2), the fuselage bottom (B1 + B2), and two sets of wing doublers (E1 + F1) and (E2 + F2). Glue the 500mm flat carbon fiber strips into the precut slot along the leading edge of E1/F1. Glue the two firewalls together crossgrain, matching the notches.


  2. If you are using the landing gear, attach the plywood to the front fuselage bottom (B1) matching the passthrough holes. Make sure it doesn't protrude above the top edge

  3. Grab the C1 and D1 main deck pieces of the wing and glue them together on the center seam, aligning the spar slot. Glue the 380mm flat carbon fiber spar into that slot.

  4. Once the glue sets, bevel the elevons (F3) and glue them in place. This is easier now than after the doublers are added to the wing. You'll want to use your cork-backed ruler to help make the 45 degree bevel cut from the top of each elevon - be sure that you cut the bevel on the long side closest to the slot for the elevon control horn. We suggest using FoamTac to make the hinge.

  5. Glue the 4 (E3) joiners into the front of the C1/D1 main deck so the small tabs stick up and down.

  6. When the fuselage is dry, cut the bevels for the rudder hinge (doesn't matter which side the hinge is on) making sure they match but don't glue the rudder hinge at this point. (just easier to cut the bevels unattached to the plane)

  7. Assemble the lite plywood leading edge jig.

  8. Raise the leading edge of the E1/F1 doublers on the jig. Glue the center joint together so that the center joint is touching the building surface in this configuration (doubler should have a slight angle in the middle). Glue the 120mm carbon fiber spar in the slot while the joint is still drying.

  9. Place scrap 9mm EPP under the main deck to raise it up and glue the tabs of the joiners into the corresponding slots in the E1/F1 doublers. Spread glue on the overlap section and adjust the deck so the center seams match. Put marks on the leading edge of the doubler at the 1/4, 1/2, and 3/4 marks for rib positioning.

  10. Gather the ribs (C2 & D2) from the 9mm sheet and sort them into two groups of 5. Glue the longest one along each side of the doubler center seam. Glue the two smallest ones along the edge of the doubler tips. Glue the medium ones into the center notch on the main deck and so it matches the 1/2 mark on the doubler leading edge. Finally glue the smaller ones of the two remaining into the outboard notches and the 3/4 marks. The final ribs glue into the center seam corner with the tip going to the 1/4 mark on the doubler. Let the glue dry.

  11. Spread glue on top of all the ribs and the leading edge as well as the top front of the main deck (do one wing half at a time) and then place the E2/F2 doubler in place using the joiner tabs for alignment. Do the same with the second E2/F2 doubler including the center doubler joint. Pin all the glue joints so they stay intact. Let the glue set before proceeding to the fuselage.

  12. Keeping the main deck supported with scrap foam, smear glue on the bottom edge of the fuselage top (A1/A2) and position it in the slots of the wing assembly. Note the tab at the back of the doubler is positioned against the doubler and the rear tab is against the rear of the main wing deck. Make sure the fuselage is perpendicular to the wing (you can use the square edge of the plywood horn sheet to verify it being vertical). This fuselage top glues onto the side of the main wing deck with the elevon hinges. The elevon bevels are on the bottom.

  13. When the glue has set enough, smear glue on the fuselage bottom (B1/B2) and matching the tabs to the slots, join it to the assembly. Again make sure the fuselage is perpendicular to the wing. When this is set up enough to handle you can hinge the rudder to the fuselage rear, matching the top edge. Also take the firewall and glue it into the notches on the nose, noticing that there are 15mm notches for the vertical and 18mm notches to match the front of the wing. Make sure this is straight to the center axis. You don't want any thrust offset.

  14. Regularly go back and press the fuselage halves together to get a good glue joint to the wing. When the firewall has dried, glue two gussets to the each fuselage corner and the firewall on each quadrant to provide additional firewall support. Be aware the gussets aren't symmetrical. One straight side is 3mm larger to match the firewall.

  15. The airframe is now complete. If you are going to paint it, this is the time to avoid getting any on the electronics. If you do paint it, use very light coats as EPP is a sponge and you can add a lot of weight very quickly. This is also a good time to go over all the joints and make sure the glue is solid. Also check both sides of all the spars as sometimes putting a spar into the slot can wipe the glue off as it slides in and the bottom has less glue. Once you are done with any gluing and painting, continue on with the electronics installation.

  16. Find the plywood control horn sheet and remove the 3 horns. Notice that one of them is taller than the other two. This is for the 15mm thick rudder. I recommend you install this one first to avoid it being installed in the wrong slot. I find spreading glue on both sides of the horns and squeezing some into the horn slots gives a strong attachment. The front ear of the horn should match the hinge joint so the pushrod holes line up over the hinge for optimum geometry. Install the other horns in the same manner. All horns mount on the top surface with the Rudder horn installed on the opposite side from the bevel.

  17. Install the servos in the precut holes so the wires exit towards the front. Install the rudder servo on the side with the rudder control horn installed.

  18. Screw the motor onto the firewall with the supplied screws so the motor mounts with the wires on the side of the fuselage bottom opposite the servo wires.

  19. Attach the servo extension to the ESC and shrink the provided heatshrink over the connectors to secure them. Run the servo extension down the bottom of the fuselage and pass it through the cable hole in the fuselage so it is on the same side as the servo connectors. This will put the battery connector on the side opposite the Rx allowing for more velcro to adjust the CG by moving the battery front to back.

  20. Find the single sided servo arms in the packages of servo accessories

  21. Measure the 3 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. Be aware that the elevon and rudder pushrods are different lengths.

  22. Attach the z-bend wires to the two ends using the small pieces of heatshrink tubing. The z-bend wires and heatshrink are in the small parts baggie. Shrink the heatshrink in place to hold the wires but DO NOT GLUE THEM AT THIS TIME.

  23. Put the z-bends of the pushrods through the top hole on the horns and then through the outer holes on the servo arms. Attach the servo arm on the elevon servo and adjust it so it is aligned straight across, perpendicular to the fuselage. Now adjust the control surface so it is level by sliding the wires under the heatshrink tubing. Continue for the other elevon and rudder pushrods. Once you have everything perfectly aligned, glue the wires to the carbon fiber using cyanoacrylate glue being careful to not glue them to the plywood horns.

  24. Plug all the controls into your receiver of choice and bind to a fresh model with a delta wing mode selected on your transmitter using an appropriate flight battery. Make sure all your trims are centered and no subtrims are set. Verify all the servos are moving in the correct direction and reverse as needed. Move the servo arms so they are as perpendicular to the fuselage as possible (servos are always half a spline off) and adjust it to be perfect using the subtrim settings on your transmitter. As you finish each control, put the servo screw in place. Bolt a prop to the motor and while holding the model at a safe distance, blip the throttle to see if the motor is turning the correct way (pulling the plane forward) and if it is backwards, swap any two ESC/motor wires to reverse it. Adjust the control throws and exponential as you like. Unplug the flight battery and turn off the transmitter. Your plane is now set up. Using velcro and cable ties, neaten up the wires. I put a longer piece of velcro for the battery on the ESC side of the fuselage so you can move the battery front to back for balance. The CG of the plane is where the KF wing doubler meets the fuselage.


  25. Go Fly!!