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...Femto 400 from full-sized plans in Aviation Modeller International.......

....................Inflight views............,

..Top and bottom views of the completed plane..

Femto 400 electric fun fly


.Span is 33inches, root chord 14 inches, tip chord 12-1/2 inches.
Length overall 28 inches..
GP motor and 1:1.7 gear box.
Futaba R-144H receiver:
Jeti JEC 30 BEC..
8x500 Sanyos.
APC 9x4 e-prop.
2 S-133 servos, 1 HS-81.
Weight 20 oz.
Wing loading 7-1/8 oz/ft^2.
Covered with Japanese tissue (40 years old!) and sprayed with 2-3 coats of clear polyurethane. Probably not a good idea. The covering was VERY brittle!
Used dental floss for the pull-pull rudder and elevator cables.
Don't do that!
c.g. came out at or past the aft limit.
Flights went OK.. at least the first one. Very sensitive on the elevator, at lo-rate. Way too much elevator area! Ailerons are too large. Lots of adverse yaw.
The surface control horns on the plans are too short. Hi-rates pulls the surfaces way too far off neutral. A very low lo-rate setting is needed for good control in flight.
Electrical tape is not a good motor fastener. Heat softens and stretches it, the motor twists on the motor. Traditional #64 gum bands work best.
The dental floss stretched on the second flight, when pulling up elevator after a spin..

.012 braided control line wire replaces the dental floss. Subsequent flights went well, demonstrating the oversize of the control surfaces. Way too much deflection and drag..
The recovered plane uses clear dope instead of the polyurethane on the tissue. An APC 8x4 e-prop works well. The motor is cooler after running than with the 9x4 e-prop.
It's a good park flyer if there's no trees (or kids) close by.

..Femto 400-2...

The next plane lost a few parts under construction:
All the capstrips went, 2 ribs and riblets- spacing changed for 6 ribs from 8;
Full depth shear webs changed to 1/16"x1/4" sticks, diagonally (and crossed) between the main ribs.
1/16"x1/8" vertical stiffeners at each main spar notch on the ribs and riblets.

Femto 400, second version
The tail surfaces are 3/32" stock instead of 1/8" stock.
Elevator has 1/2" less chord, ailerons 1/4" less chord.
Finished weight less equipment is 4-1/3 oz.
Covered with the 40 year old Jap tissue, and dope. Thc covering is much less brittle than the polyurethane finish.
Control horns sized to match the horns on the servos (CS-21s).
Hinges are dental floss, in the old-timey "figure 8" configuration..
Femto 2 stats:
2 Cirrus 21BB servos, 1 Expert 300
Weight RTF: 19 oz.
Wing area : 389 in^2
loading : 6.39 oz/ft^2
Femto 400, second version

Both Femtos...

both Femtos

..Electrified Gentle Lady..

..Vee-tail camera plane..

..Inverted Vee-tail camera plane..

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.e-mail to: Paul J. Burke