McB JN-4 Jenny

Plane McB JN-4 Jenny 1.4

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Build Plan (PDF, AI, etc.)
This is now my fourth iteration of plans for a Curtiss Jenny. Built from 4 sheets of DTFB, plans have been modified from the originals for easier and more durable construction.

It's built from 4 sheets of DTFB, true to scale in appearance and flight characteristics, and can be built without the need for any specialty laser cut parts. For those with 3D printer access, there is an stl file for the (later, more powerful) Hispano-Suiza engine.

I would classify this as an intermediate build and an intermediate flight experience.
There are now two versions of the plans, a long fuselage and a short fuselage.

The Long Fuselage is more scale accurate but must be built with extra attention paid to keeping the tail light. On the prototype I used white gorilla glue for assembly and carbon fiber pushrods for the rudder and elevator. Unpainted, with all the cowling decorations and a 3S 2200 battery at the firewall the CG is near its aft limit. I didn't have a 3300 3s to test, but the math says it should pull the CG forward enough to balance just a little nose-heavy.
The Short Fuselage can be built with hot glue and typical FT construction and stay in CG. Do try to keep the tail light though. Every little bit helps.

The Jenny has a lot of wing area for its weight, which makes it a very slow-flyer for the size. She wants a relatively calm day where she won't get thrown all over the sky by gusty winds. I moved to a fold-over style lower wing to improve strength and handling in wind but kept the upper wing under-cambered to save weight and foam. Power comes from a Turnigy 2826 1000kv motor turning a 9x4.7 slow-fly prop on a 3s 2200mah lipo.

Flight characteristics are much improved for this version. There is now enough down-thrust that you can power out of trouble without dragging the plane into an uncontrolled vertical climb, and there is plenty of power on 3s to outperform anything a real Jenny could manage. Turns are still a little lethargic and best made mostly with rudder and just a little aileron to tweak the bank angle, just like the real thing. Adverse yaw is very palpable if you don't have differential. I love to goof around with barnstorming aerobatics; forward slips, side slips, stall turns, spins, and low passes are the Jenny's bread and butter and quite satisfying when done right. Loops are possible, but visibly load up the long, slim wings. I haven't tried a barrell roll yet; I'm not that good of a pilot, and the roll rate is slow enough you'd probably get bored and go home before the ol' girl was even inverted.

SPECIFICATIONS:
Wingspan: 52"
Length: 30.5 or 32"
Wing Area: 518 in2
Approx flying weight with 2200MAH 3S: ~30oz
CG: 2" from Leading Edge of top wing
Wing Loading: ~8.3 oz/ft2
Wing Cube Loading: 4.4
Approx. Stall Speed: 14 MPH
Approximate Max Speed: 35 MPH
Motor: 2826 1000KV
Prop: 9x4.5 SF
ESC: 10 amp,
Servos: 4, 9g servos.
Substitute as necessary.

Pushrods: .047" music wire or 1.8mm CF tube
Landing gear wire: 3/32" music wire.

Throws
Aileron: 18º up 5º down
Elevator: 20º
Rudder: 20º

The thread discussing the genesis of the original is here: https://forum.flitetest.com/index.php?threads/foam-board-jenny.13126/
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Tench745
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Latest updates

  1. JN-4 Version 1.4

    Updated plans for the McB Jenny. ATTENTION: There are now two sets of plans. The Long Fuselage...
  2. V 1.3

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Good looking plans. Thank you for sharing.