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04/05 JDC: Jedi Star Fighter

Patric McGrath's Jedi Star Fighter, 04/05 Jet Design Contest entry

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Introduction


Weight:540g (19 oz)
Length:102 cm (40 in)
Wingspan:53.34 cm (21 in)
Wing Area:23 dm2 (357 sq. in.)
Wing Loading:23.3 g/dm2 (7.66 oz/sq. ft.)
Fan:(2x) K & P 44 Microfan
Motor:(2x) KP 02
ESC:CC Pixie 20P
Battery:3S 2600 Li Poly

I have wondered for some time if the Star Wars Jet of Obi Wan Kenobi would fly. I was heartened by Alfredo Delgardos model which was fairly small and powered by a GWS geared motor & tractor prop.

I wanted to build a slightly larger one which could carry two small ducted fans, and thus be more scale like. I know of no one else who has built this model with microfans. The advent of this contest gave me the incentive to try and be the first.

Construction

Construction had to be simple, light and inexpensive. A white styrofoam semi profile structure would fit this bill. I obtained a plastic model and took the scale dimensions from it. Planform and profile view were measured and drawn out on white butchers paper. The styrofoam boxes in which broccolli are shipped to the grocery markets are made of small cell 1” thick styrofoam with large smooth panels in the sides and bottom. The markets usually are happy to give them away. I got four.

The shapes of the wing plan and profile were marked out with felt tip, and cut out accurately with a band saw. A fine hand saw would do as well. The two wing halves were shaped with an elliptical leading edge on the top only,and a trailing edge tapered up from the bottom to the thickness of the elevons. The wing halves were placed flat together to enable the shaping on each side to be as identical as possible. When satisfied the wing halves were then butted together on the centerline and glued with RPA.

The fuse top profile was sanded as necessary to fit and glued in place. The fuselage side pieces were cut out from meat tray foam. The black skin was peeled off and these were glued in place with aliphatic wood glue. The tail fin was made from some scrap EPP foam as I anticipated it getting more attention from Terra Firma. This was cut to fit and glued on with RPA. The under keel was shaped to a streamline at the back then also glued in place with RPA.

The elevons were made from scrap 3/8” styrofoam. Chamfered on the front edges and tapered to 1/16” at the trailing edges. Each elevon was stiffened with fibre re-enforced packaging tape on both sides, and a balsa root rib, to carry the forces of the elevon horns. This completed the basic airframe.

The motors were wrapped in a Styrofoam sheet which was taped with 2” packing tape on one side. The other side was sanded at one edge to an half elipse, before wrapping the prepared foam around the fan shroud to give the proper intake profile. The tailcone was cut from a Styrofoam cup and fitted over the remaining end of the fan shroud. These small modifications add 1 oz thrust to each fan. The fans used are K & P 44 Microfans, which in modified form are said to give a total 6 oz thrust.

A hole was cut thru the lower keel and a shaped block of hard balsa was glued in, protruding just enough to pass thru the foam of the fan ducts and glue to the plastic shroud. The fans were then glued in place with RPA. The wires were soldered to the ESC, which was bonded to the outside of the keel with 3M77 glue where it was in the airflow for cooling.

The Jeti 20 RX was cut into the side of the keel well forward, with the servos cut in back of the RX. For lightness and simplicity the pushrods were aluminum tubing with metal clevises at both ends. At this point the model was put on the CG machine and the 3S 2600 Li Poly pack was moved around until the model balanced with the CG at the 15% MAC point. The pack was then marked around with a black marker and the hole cut out right through the wing.

A slice was then cut off the removed plug and glued back in the top surface of the wing. The Battery pack fits tightly in from the bottom and is held in place by strapping tape for flight. The TX and controls were set up, and that completes the model, except for painting and decorating.

Flying

Flying was a complete non event. It flew first time(unpainted) needing only 1/3 down trim and couple of clicks left wing down. Four trimming flights were completed in slightly gusty conditions . It sat in the air with a typical nose high attitude peculiar to extreme sweep back deltas. Didn’t achieve a stall, just a sort of downward mush. Excellent for landings as it just lifted its nose and flopped on the ground. It also warned right before stalling by waggling its wings in a slight Dutch Roll. Didn’t attempt any speed runs on these first flights, but I am encouraged enough to paint and decorate the model now.

Conclusion

In conclusion, considering the simplicity and low cost of this model, and particularly the ability to build it quickly (before the enthusiam wears off) I count this one as a success. Flying photos to follow , hopefully before the end of May 1st, U.S.A.Time., and weather permitting.

Discussion

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Old May 08, 2005, 12:08 AM
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May 02, 2005, 04:24 PM #19
Ed Waldrep
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Join Date: Jan 1997
Location: Las Vegas, NV
Posts: 3,515 Sweet. A Star Wars universe vehicle that actually flies, and all without repulsorlift technology!
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Old May 08, 2005, 12:14 AM
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May 02, 2005, 04:27 AM #12
GRE99
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Join Date: Apr 2005
Posts: 19 Fantastic job! My son and I are avid Star Wars fans and love the fact you chose this suject to build. If it flies as good as it looks I hope you win.Tell me you made plans and drawings please. May I be the first to beg for a copy so i can build one for my sons 7th birthday. Please please please.
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Old May 08, 2005, 12:16 AM
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May 02, 2005, 04:48 AM #13
U812
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Way to go Patrick! Very nice.

Steve
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Old May 08, 2005, 12:17 AM
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May 02, 2005, 05:10 AM #14
AirX
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Join Date: Nov 1999
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Posts: 4,564 Hey that is pretty neat looking, and great timing too with the new movie opening soon.

Cheers,

Eric B.
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Old May 08, 2005, 12:18 AM
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May 02, 2005, 08:36 AM #15
stumax
a dingo's got my plane!




Join Date: Aug 2002
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Posts: 2,025 Excellent stuff, Patrick!!! But where are the usual "photo accessories"?

Stu.

ps. how 'bout flying this week? Wed?
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Old May 14, 2005, 08:55 PM
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Neat model !!!!

Patrick, definetely your model is very realistic, nice and clean lines and powerful!!!! The force be with you

Cheers.

Alfredo Rubio
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Old May 14, 2005, 09:07 PM
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guadalajara, jalisco, mexico
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Guadalajara Star Wars Fan Club in Mexico

Patrick, You make me to remember how this model was born, first as a free flight model to use in the class with special education kids, sponsored by the Guadalajara SW fan club, 2 kids could flew it, Marco and Rogelio, later the guys from the club gave a present, toys to the kids in the kid´s day... since that day I was a teacher, after 6 years, we still using planes with this kids, they learn playing

The boys of the Club send to you his best wish, and the happy for the Episode lll

Cheers

Alfredo Rubio
President of Rehabilitacion Integral Macel, A. C.
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Old May 15, 2005, 02:40 AM
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Posts: 4,920 Great job Patrick!
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Old May 21, 2005, 10:26 PM
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Dimensioned Drawing of the JSF styrofoam parts is now up on

http://www.rcgroups.com/forums/showt...=3#post3784098

Cheers. Patrick.
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