fly with the wind>Goliath
fly with the wind
osamu's rc flight
Goliath
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PRODUCT:
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Goliath
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MANUFACTURER:
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Sylvan Aircraft
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CONSTRUCTION:
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EPP foam wing reinforced by packing tape and covered by colored tape, balsa elevon covered by Oracover, Coroplast winglet
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FUNCTIONS:
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Elevon, Throttle
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WING SPAN:
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406 mm (16")
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WING AREA:
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5.5 dm2 (85.4 sq. in.)
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FLYING WEIGHT:
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110 g (3.9 oz)
(w. Poly Quest Twenty 2S400)
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RC GEAR:
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Castle Creations Berg Microstamp 4L receiver
2 x Model Craft 333 sub-micro servo (5.4g)
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DRIVE SYSTEM
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Feigao 12mm BL motor
Castle Creations Thunderbird 9 ESC
GWS 3x3 prop
Poly-Quest Twenty 2S400 or Thunder Power 2S730 Li-Poly pack
Previous setup:
GWS EDP-50XC motor
GWS 3x3 prop
Castle Creations Pixie 7P ESC
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"Are you David??"
building:
This is my first EPP flying wing. I joined two wing halves with 5 minutes epoxy and installed motor mount and radio gear. Then I gently sprayed 3M77 spray adhesive, reinforcced wing with packing tape and covered entire wing with colored tape: upper surface with yellow, under surface with red. I covered elevon with Oracover and hinged to wing with oracover. I glued Coroplast wingtips with 5 minutes epoxy.
I replaced kit-supplied pushrods with carbon rods to get solid control.
CG and control throw:
The building instruction recommends CG at about 3 1/2" from nose. I drilled three small holes at undersurface: 3.4"(86mm), 3.6" (92mm) and 3.8"(97mm) from nose.
Using these holes, I checked CG by suspending my Goliath upside-down with a small hook and fishing line. My Goliath was too much tailheavy. I should added about 20g (0.7oz) of lead at nose to locate CG at 3.6" (92mm) from nose. Someone on RC-Groups wrote 4" is OK so I decided to start with this CG location.
After several flights, it seemed to be noseheavy and it needed too much up elevon trim so I moved CG gradually aft. Now it is about 3.8"(97mm) from nose. I removed nose lead so the flying weight is now 110g (3.9oz). I also attached heatsink (shortened to 0.35"/9mm) to the motor.
I set elevon throw about 4mm (1/6") up/down and set 50% expo to both aileron and elevator.
flying:
I tossed my Goliath several times and added some up elevon trim. Then I grabbed the left wing leading edge with my left hand and gently open throttle with my right hand (we Japanese use mode II TX, elevator on left stick and throttle on right stick). At full throttle, I threw my Goliath like a frisbee, let him go straight to wind.
It is a small airplane but not so twitchy, rather stable for this small size.
strengths:
easy to build
highly durable, crash resistant
high speed and stable
able to fly moderate wind conditions
stock brushed motor produces plenty of thrust with 3x3 prop
inexpensive (kit including a motor, two props, packing tape and colored tape)
weaknesses:
None for design, construction or flying performance but if pressed I would say that this airplane flies so fast that you should first-fly your Goliath at large flying field. I first-flew my Goliath at about 500x1500 feet baseball field. Once properly trimmed, you may fly at smaller field.
conclusion:
Goliath flies so fast that it is a bit challenging for me but I do enjoy flying.
Great flyer.
overall rating:
AAAAa (four and a half of five)
trailing edge modification
After several flights, I decided to remove some EPP foam around the motor for noise reduction. Now my Goliath flies quietly PLUS he becomes more stable, control response is improved and it is possible to fly slower!!!
After this modification, the airflow to prop becomes more smooth, the prop efficiency might be increased, more thrust might be achieved and some drag generated by turbulence at trailing edge might be decreased.
last updated: Nov. 15, 2009
