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1970 Diamond Ring photo taken by my Lower Richland High School
 Science Club students
The Gotha Eclipse Stik

Mission

This build project ia about designing and building an FPV/UAV plane to  photograph the 2017 Total Solar Eclipse over South Carolina... higher up in clear air. The vehicle must carry 16 oz of cameras, fly smoothly in totality for 2m 30s, and complete a round trip flight for 40 minutes. We are going for a loitering slow flyer.


Starting Point

Doug and I were looking for an experimental plane, mainly the Gemini II, but at our age a ground zero build up was out of the question.

We choose an off the shelf ARF, the 83" Giant Easy Stik from Value Hobby in Addison, Illinois. Their inexpensive balsa/ply kits are nicely produced, and unlike most China kits, this plane comes with quality hardware, accessories, and color manuals without the overseas shipping rates. We have never had a problem with their planes and we like the owner as he gives advice on upgrades, etc

We have three of these models so we are taking parts from the kits to build a super "GOTHA" plane. Both the wing and fuselage are being extended and substantially built up.

Prototype model... Twin engine, 159.25" wingspan, wing area over 2639 sq in, wing and fuselage strengthening rebuild, motoring, power selection, propping, and endurance flight profiling follows Spike Webb's [Bearospace.com] Gemini II modeling and design ideas. We are going for a loitering slow flyer that can house heavy cameras and gimbals... and later a tow plane.

Below is a side view looking down the wing's D cell. Doug's playing with positioning on the wing and angle of attack for the nacelle.

 

Doug, our wingman, starts by modeling a nacelle on the wing for holding a big, honking battery and ESC using foam from Dollar Tree. This a bottom wing view which shows we are mounting the nacelle high on top of the wing.

He plans to engineer a storage cavity between the ribs.  His dilemma is an added 1/2" stiffening tube in the D cell for the leading spar, AND a 1" tube down the center of the ribs. He will be closing off the D cell segments and pumping in a new CRC, minimal expanding, closed cell structural foam.

 

 

Fuselage Views







The fuselage [Top] is how one kit  came shipped several months ago, but Value Hobby decided to ship the next kit in a smaller box, split in 2 as in the Middle photo. This was a windfall for us as we were having to add a 12" mid-section to off-set the extreme extension of the wing. And the adjoining structural pieces are heavy duty.

The Bottom shot shows where we have started the process to re-glue all the joints first, before starting to add the structural
 reinforcement including a 1/2" tubing going from the mid-section to the tippy tail.
 
In the 10 minute video below we show one how we did some more serious design and configuration work using MotoCalc 8, CgCalc*, and Realflight 7.5 where we end up modifying the model physics of the RF stock Big Stik, and then fly our new Gotha Eclipse Stik around the block...

* Daniel T. Prosser dtprosser@gatech.edu School of Aerospace Engineering Georgia Institute of Technology

CgCalc Excel 2007 Free Download



Phase 1 Complete... Conclusions:

  No fuselage elongation needed... Both the RealFlight stock and lengthened models flew/handled similarly and successfully.

The nacelle cavity can not handle the battery weight and size... going into the fuselage instead... looking at a hatch for the ESC there.

Final design data for this craft is as follows:
 
With MotoCalc 8 we set the power plant and plane specs (below)


 

We selected the power statics (below)  and the in-flight characteristics we wanted   Here, there is an option to reduce the throttle to see what affect it would have on flight time and handling.

   
On the left we specify the various weights and x,y locations on the plane... a 2D plot is created.

Finally, (below) is a detailed list of data stats about the plane... In the video above, we then flew the physics model of this set-up in RealFlight 7.5


 
 
Phase 2 - Gotha Build Modifications

includes wing, fuselage, rf front end, and power mod details...

 


Wheelspan Design Consideration
Most larger planes have a general design ratio wheelspan to match it's wingspan, so using the Cub on the left we are needing a main gear between 30 - 40 inches... [Ever tried to purchase one this large?]

Since we had multiple Giant Easy Stiks, we fabricated a big 35" main gear using two stock 1/4" AL  main gears... Showing 4" foam tires we may upgrade to the 1/3 Cub balloon tires later.

Total weight 775 grams.
 
   
 

Here are two views of the 1/4" AL lamination  backplate that goes inside the main gear compartment.


          

Below is a layout of the main gear compartment to be built
like a Cajun Brick Outhouse... strong.

 

We have a steerable nose gear for the fuse firewall, where we will be adding a 8.5" Camera compartment.

 

In the two photos below the nacelles are glued and bolted in using the outside two
 super-ribs spliced into the wing. The nacelle cavity will have a hatch coverand the motor boxes
 hanging aft of the leading edge will hold the motor and ESC/UBEC. After covering the boxes we will
 cut out the rearmost triangular holes to enhance air flow from the cowling mouths... thus
keeping the motors and ESC cool.
 



The starboard nacelle cavity will house a Lemon telemetry module and mounted beneath this cavity will be a
2000 millwatt amplifier  which will feature a 6 dBi monopole. The telemetry transmitter receives and
 transmits data packets from our Spectrum DX8
and the Sunhans amplifier is bi-directional
with gain on both transmit and receive.


 

Below is our 2.4 Ghz Yagi 12dBi and hanging on the bottom of the tripod is a 10 dBi Yagi... this will be connected via
 an amp to our DX8 or Dx6i Spectrum Transmitters. The lettering on the beam states that when vertically
 polarized [as in the photo] the 12dBi has a 45 degree vertical beamwidth and a  38 degree horizontal beamwidth.
With the same orientation the 10dBi yagi has a  51 degree vertical beamwidth and a 45 degree  horizontal beamwidth.
Both antennae have a modest 16dBi F/B ratio indicating larger sidelobes to pickup the plane in close.



 


At this stage we are discussing permanently joining these two inner wing quarters and temporarily
 affixing the two outer  wing quarters giving us a three piece wing... OR permanently joining wing
 quarters 1-2  and 3-4 giving us a two piece wing with the middle being in the fuselage where
 we would adjoin the two wing halves temporarily for flying.

Our decision is to build this as a 6' center wing with two 4' removeable dihedral wings.



 
The RF Receiver Front End

This dual receiver test board helps us with 6 tests including short and long range checking for
 the three receivers on board, the integration of a monopole on the Lemon diversity and
telemetry modules, the failsafe setups, and a combination of failure scenarios,
 as well as a buddy box handoff test.

The Blue RCD3022 Redundant duel backup box supplies power to the two receivers,
and this blue box is powered by a dual backup power/battery system [described later].
 
 
 Phase 3 - Coming this Winter...  Integration Bench Testing

Well we decided that due to the complexity of the triple redundant RF system, we needed
to fly the subsystems in a test plane first so we have the Phantom FX-61... should be ready
to fly inJanuary with a moderate number of enhancements.

 

Testing of TS832 600mw 32 Channel Video Subsystem in FX-61

 
 




More coming...

 
 
Phase 4 - Coming this early Spring...  Maiden Flight
 
Phase 5 - Coming Spring...  Long Range - High Altitude Test Flights
 
Phase 6 - Coming Summer 2016...  Solar Photo Stabilization and Inner Corona Capture Test Flights
   
The Zeta Dolphin Jet Project

1M EDF/Pusher EPO Jet Combo

Fly it without wheels - Stay off asphalt...

PNP build about 1 Hr... Upgrades 2 Hrs

The In-Box 55mm EDF/Motor @ 4600 Kw

The 64mm EDF/Motor @ 4600 Kw Solution

Final Evaluation

The good, the bad and the ugly...

 
 
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