Twin Boom Pusher

RCsean Twin Boom Pusher

A classic diy RC plane design, easy to build, fly and versatile.  This version includes 3d printed fuselage frame, boom mounts, and landing gear.  Photos below are from my initial prototype (with up-swept wings) and the improved version 2 with a stiffer frame and including rudder and flaps.  Free plans and stl files of version 2 parts available on Thingaverse.


Example with up-swept wings: helps stabilize roll axis (version 1)

 Example with flat wings for improved roll responsiveness, with flap and rudder servos (version 2)

Wing detaches with rubber bands and a single servo wire connection.  Print files include wall mount to hang your work of art and make room on the work bench.


Easy flying, stable, and with no bad stall tendencies due to the light wing loading and stable pusher prop configuration.  With landing gear in use, both motor and prop are very well protected meaning little danger to others in case of a crash while also protecting the motor and prop during landings.

Specs:
Width: 56"
Length: 40"
Weight: ~600g (~800g with 2200mAh 3s battery)
Center of Gravity: 1.5-2" behind wind leading edge
Flying Time: 13-15 min

Electronics:
Battery: 1800-2200+ mAh
Motor: 50-60g motor, 1250kv (Sunnysky X2212, FlightTest B/C, or similar)
ESC: 30A
Prop: 8x4.5(1250kv)-10x4.5 (980kv)
Servos: 3-7 9g, (flaps and rudder optional)
Receiver: 4+ channel

Materials:
Foam Board (DTF, 2 sheets + 1 sheet of MPF- optional)
∅6mm rod (CF or wood), 1M
∅5mm rod (CF or wood), 1M
Colored packaging tape
Standard foamboard build materials (as used in FlightTest.com or Experimental Airlines)

Videos:



Assembly Guidelines:
Plane is built in two pieces, only requiring one servo wire connection to mate wing and fuselage along with a few rubber bands.  Optional landing gear is easily attached or swapped out: skiis (60g, great for winter in northern areas) or wheels (coming soon).

[version 1 photos]

Wing Assembly: Receiver mounted to wing





Fuselage Assembly:







All Strapped in & ready to fly

ESC servo wire passed through wing
[Version 2 photos]
Receiver built into the wing:
Single motor servo wire extension to connect with ESC from fuselage assembly:
 Vertical Stabilizer



Build Instructions, if you want to build this or something similar:

1) Watch the Armin wing build method on YouTube.  Couldn't say it any better.

2) Review and/or print out plans (D size, or multiple 8x11" pages)
 - Wing Assembly (shows one side of the wing, fold over to make "mirror image" of the other side)
 - Fuselage Assembly

3)  Watch assembly video.  Steps and tips used for the version2 build.

4)  Decide on configuration
 - Flaps (as shown in version 2 photos)
 - Wing tips: slice angle wedge through wing ~6" from edge, ~1/4" wide on top, angling down.  Lift up ~1" (same on both sides), glue and tape.



Notes after initial flights:

After many flights with the version 2 design, there are several things that I may change whenever I get around to a 3rd version.
Rudders: the rudder size is not nearly large enough to turn the plane on the ground, and only has a subtle turn in the air.  To make it worthwhile with the added complexity,  double the rudder size (full height and longer).
Flaps: Fun to have dedicated flats, though if you don't come in steep enough the plane gets a bit squirley (in yaw axis) upon landing if going super slow (no bad tip stalls at least).  Longer booms or larger rudder may also help with low speed yaw control (fine in normal fight w/o flaps).
Horizontal Stabilizer angle: The stabilizer has about a degree of upward angle.  At half-full power this does result in a slight increase in elevation.  While not always desirable, it did help me land when the elevator servo horn detached from the servo (I didn't use a screw to hold it on) - easily landed with no damage.  So I think I'd keep it as-is (and is somewhat dependent on exact battery placement).
GoPro:  I added a gopro session to the 2nd version (good prices on the original, used).   Need the longer nose option if not using a gopro, or heavier battery, etc.
Flat Wing: very nimble, however requires frequent minor corrections during flight to stay level.  I may consider wing dihedral or electronic stabilization in a next build.
Aerobatics:  while the plane can do rolls and flips, it is not the most graceful. Flips are somewhat sluggish with the weight of the battery forward and the motor backward.  Rolls seem a bit awkward, not sure exactly why (perhaps the dual rudders?).  The dual motor sport is much more aerobatic if that's what you're after.  However the pusher design is very nimble in turns and great for FPV cruising.
Landing Gear:  I am slowly working on landing gear, but as of April, it is still snowy here so sticking with skiis for now.  Plane flies great w/o any landing gear, just makes fpv a bit more challenging with the hand launch (1/2-3/4 throttle, toss, increase throttle with minor up elevator).  Upon landing, I have found either the prop or motor mount can occasionally get damaged (never had a problem when using landing gear).  May look into folding props for next build.







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