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Maximum fun, minimum cost
The story of a foam C130 Hercules build.

By Toni Reynaud

Part 3 – Flying the beast

With the model finished, one fine Saturday Andrew Gibbs and I took the Hercules to our club’s patch on Thorney Island. We did a low power test glide first over some longish tufted grass (just to be safe) and it was good.

After this we continued to the normal patch to do a proper flight. Our club magazine editor and scale flyer Bruce Smith was on hand and he was co-opted into wielding my camera. It’s not a proper video camera, but was good enough for this task. On the shout of ‘ready’, I ran and launched and away it went, steady as a rock. Andrew said it climbed well on about 2/3 power, so there's no problem there. He took it up fairly high and did some steep turns to check manoeuvrability, then a stall check where it fairly benignly dropped its left wing and recovered well, followed by some low passes for the camera. It is quite probable that the benign stall behaviour is partly to do with the washout I incorporated.

I took over then, and found it to be very docile and yet controllable. It was great! A time check said over five minutes, so in line with the flight plan I did one more circuit and landed at six minutes - dead easy. I think that the size of the model has some bearing on how well it handles – its extremely docile, yet it looks good.

Please click image for a larger version

Launching – a bit steep, but it got away. The RAF flew the Hercules from RAF Thorney Island between 1967 and 1975, so this may have been the first Hercules to fly here since then!

Please click image for a larger version

Low pass for the camera.

The six minutes or so of flying took 1.56Ahr (1,560mAhr) from the batteries, about half the capacity. This meant that the average current draw was about 16A, or 4A per motor, equating to about 175W - not a lot! Eight to ten minute flights will clearly be possible without overstressing the batteries. The following information gives an overview of the static performance of the power system.

Hercules power data
2 x 3S 1,500mAh LiPo, 12.48V off load
  RPM Voltage Current
Pitch speed
Full throttle Lots ! 10 50 500 ?
Climb throttle 10,000 11.1 18.5 202 41 mph
Average throttle ? 11.6 12 140 ?
Low throttle 8,500 11.7 6 70 34 mph

This table was generated from readings taken using fully charged LiPos with the wing balanced on my knee while taking phone calls about a computer problem and switching off the fluorescent lights so that the rev counter would work and drinking a cup of tea and photographing the underside of the fuselage - so I missed a couple of readings! However, the general spread of info is useful, I think. The model flies nicely at or between low to average throttle.

After taking the wings off, I noticed that the Velcro holding the power tray to the fuselage floor had pulled off. This must have happened at the landing of the test glide, so the CG for the test flight was probably at about the 18 - 20% position! It still handled well. By comparison, the full-size Hercules CG figures are 19 - 30% takeoff and 16 - 30% landing - quite a range. A foam block was later cut and glued inside the fuselage front to define and limit the forward position of the power tray.

The second flight was timed at about nine and a half minutes, and the charge quantity required for a full recharge was 2,300mAh or about 76% of capacity so in the interests of prolonging the battery life, the timer will in future be set at 8 minutes to land at 9 minutes.

All in all, this was a very successful and relatively low cost build of what started on not much more than a thought of “I want one of those!” The table below shows the modest expense incurred in building this airframe. I’ve left out the cost of the hardware items because they may well later do service in another model. It’s interesting to realise that the total airframe cost of £14 is about the cost of a single gallon of IC modeller’s glow fuel!

Item Source Purchase Cost
Foam Waste Nil
Paint B&Q £4.00
Lightweight Filler B&Q £6.50
Motor Wiring Stripped from 13 Amp household cable Nil
5 Minute Epoxy Cheap Shop £2.50
Brown Paper Cheap Shop £1.00
Total airframe cost £14.00

The model has attracted a lot of interest from fellow club members. It’s huge, and flies like a dream. I intend to continue flying it, possibly with another set of batteries, and just enjoy seeing the sight of a Hercules in the sky above Thorney Island again.

Hercules technical data
Span 1,800mm 71 inches
Length 1,380mm 54 inches
Flying weight
(2 x 1,500mAh 3S LiPo)
1,660g 3lb 10.5oz
Wing Area 0.34 sq m 530 sq in
Wing Load 49g/dm 15.9 oz/sq ft
Batteries 2 x 1,500mAh LiPo
Motors 4 x 7.2V Speed 400
Props 4 x Gunther 5 x 4.3
Max Power 490W
Power Loading (max power) 299W/kg 136W/lb
Average in flight power 175W, equivalent to 48W/lb
Control Ailerons, elevator and throttle


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