Krakwing Build Notes

[[Krakwing Build Instructions]] [[Krakwing Board]] #rc

Build Notes

Cutting Wings

• Measured wing sides and discovered that the two edges were not parallel, with a parallelism tolerance of about 2°
• used Onshape sketcher to develop a set of dimensions to
• cut the foam to shape using the plans, mostly freehanded, with only a scale, sharpie, and calipers
  • In retrospect, should have printed a template
• The wings are mostly straight, but there were some gaps that needed to be filled and one wing is ~2-3 mm “in front” of the other Carefully measured sharpie lines drawn pseudo-freehand

Test fitting: Yes, I cut the wings out with my Takamura.

Gluing Wings to Fuselage

Use a slower-setting glue, like E6000.

Nose

• Nose/camera mount had non-manifold geometry
  • Fix: Isolate the half that had fine geometry
    • For some reason, mirroring the good half would still cause non-manifold geometry on the other half
  • Take that half, convert to high resolution STL mesh
  • extrude cut as little as possible to make the middle completely flat
  • then mirror that mesh
  • final product will be a mesh that is just slightly narrower than the original (0.08mm in my case) but had fully manifold geometry
• Printing was fine, I did it vertically, with tree supports holding up the camera mount and the top
  • Another option was to do it on its side, with one of the wing-facing sides on the build plate
    • While attractive due to needing less support, this would have led to awkward supports
• Also had to modify the mesh to accept proper M3 threaded inserts
  • The holes Daniel designed were a weird size between M4 and M3 even though he used normal M3 insert size for the motor mount
• While printing the modified heat insert version of the nose, I tore a hole in a brand new bed due to bad offsets
• After losing this brand new bed, I switched to powder coated steel and it is so much better, I should have always had a steel bed

Nose updates 3-29:

• I thought that the FC outputted 5v to camera, but it actually outputted BV to the camera, so I fried it.
  • Ordered new camera
  • Will have to wire the camera to the VTx onboard 5V BEC
• I wanted to change the VTx voltage Vv on the FC to 5v, but the VTx minimum V is 7
  • FC supports BV, 5V, or 6V to both the camera and VTx

    Paint

• One coat of Rustoleum Ultracover seemed not to melt the foam noticeably
  • This paint does have acetone
• Was a little uneven in the sunlight, but it worked out
• The paint (Rustic Orange) has a nice mellow burnt orange color
• Left the elevons unpainted
  • This really gives an orange sherbet vibe to the plane

Post-paint, pre-laminate

Foam Lamination

• Waited 24hrs from painting and that seemed to be enough time
• Sprayed the painted foam with one light coat of Super 77
  • Was not enough, the laminate would stick in some places but not in others, most importantly the corners
  • didn’t notice the foam being dissolved Super 77 is almost completely transparent
• Cut the laminate to shape
  • One piece for each piece of foam
• Using a Black & Decker nonstick clothes iron from Amazon
  • No water
  • setting 4 “blends” was too hot
  • setting it right above 3 (synthetics) to 3.5 seems to be right, will depress the foam only just slightly at 2-3psi
  • Tried two methods: pinning down corners and ironing from center out
    • With this film (I don’t know what it is, but I think it’s stationery laminate) the center-out method worked better: there were less wrinkles. Was not able to eliminate wrinkles entirely, however.
  • Cut off excess film, will cover the beveled edge with a small flap
• Overlapped foam from the top side to the bottom, i.e. left a flap on the top and ironed it over the bottom
• The laminate shrunk ever so slightly
  • It was enough to deform the slight reflex in the control surfaces, but this was to be expected because of how thin they are
• Cut off excess with a utility blade

  Attaching Elevons

• Used 3M standard packing tape
• cleaned the surfaces with 99% iso
• carefully attached elevon (the tape sticks to laminate, not foam) top surface first
  • Maximum deflection during sticking to ensure that the elevon has enough range of motion
• Bottom surface then taped, also at max deflection
• Cut the excess tape away from the edges

Wingtip Covers

• Used a sharpie to mark where the holes in the covers were on the foam
• had to expand the holes with a knife
• Used foaming gorilla glue and used tape to clamp the covers onto the wings
• I have previously noticed that Gorilla glue soaks into the foam, so I hope that these will actually adhere
• They seem to have adhered great with only small dots of Gorilla glue in a line spaced about 10mm apart

Here, the tape on wingtips is to clamp on the wingtip covers while the glue cures

Servos pt. 1

• I am personally soldering the servo wires onto the flight controller because the DuPont connectors are too tall for the plane and horizontal connectors wouldn’t fit in the avionics compartment
• Traced in the servo housings 5mm back from the main spar
• Cut the traced lines with a utility knife, going roughly the depth of the servo housing (~15mm)
• picked out the foam beads with pliers for big chunks and tweezers for individual beads
• Glued in the servo trays
  • Spread glue around the sides of the tray
    • One thin bead around the whole thing was a good amount: only got the slightest bit of foaming through the top
    • The sloppier side (I tried to smear this side) got a little glue that dripped underneath the tray, but no big deal. A thin bead around the bottom edge of the side was plenty.
  • Used small bottles to weigh down the trays overnight
  • They seem to have stuck great pre-flight

At this time, I have to think critically about where I will route the servo wires, because I plan to have some electronics out on the surface of the wings, so I’m going to continue the servo story in the next section.

Electronics Placement

I didn’t modify the avionics bay. I really thought I would have this project done in a weekend, and I didn’t want to wait for another to print. In retrospect, I definitely should have waited and modified the avionics bay.

Since I decided to buy different electronics than Daniel designed the plane for, they don’t really fit well in the avionics bay. I bought all of these right when the news outlets were crying “tariffs” and I really thought I would be hit hard if I tried to buy the Daniel-configured electronics from Aliexpress. So, I Amazon Primed slightly a different controller and VTx. The controller is smaller, but it doesn’t line up with the 3d printed holes. The VTx is bigger, so I will have to mount it on the wing. This is not a huge deal though, as I can use the empty space in the avionics compartment for the receiver and ESC.

Conclusion

It flies!