This Extra 300S kit project was originally started as a glow powered installation about 4 years ago. I had purchased a OS 46 and a scale muffler to suite, but have decided to go with an electric conversion for a number of reasons. This image below was the sum total I had completed after a move, and sat like this in my garage for a few years this way.
I first made the minor fuse conversions needed for electric, including a hatch to have easy access to the battery without needing to remove the wing.
I shopped around for a power plant and settled on this Turnigy 5055-580 . Should drive a 14 x 8" using a 5cell 5000ma lipo for 1475w. When choosing an electric you could use less powerful options but with this motor I can cruse on 70% throttle with power to spare. This keeps the strain out of things with a motor running 'cool' within it's max draw capability.
I finished the covering and starting the fitting process. I did have some issues getting the cowl paint to match the mono coat film used, I found that the paint needed white undercoat applied.
I fitted my JR 36mhz gear into this airframe, seems to go well and no interference. I have since found the benefits of FrSky 2.4G Modules and will be installing this into the extra soon.
A HK pilot installed and canopy is attached. Some paint tinting was needed to get close to the Monocoat Blue iron-on film. The Pilot had to be reduced in height and a new ply base made and affixed to him. Painting the cowl and wheel spats in a few days, next images are the assembled plane less possibly the spinner.
Finished! After starting this 4 years ago and having a break off RC it's finally done.
Now does it fly? Motor is smooth running, prop balance great, power awesome (ran her up in my lounge room to scare the cat) . The CoG worked out nose heavy, so I added 34g to the tail and it now balances CoG. Flying weight is 3.37kg, a touch heavier than the specs for 40 size Glow @ 2.6kg but has twice the thrust. It could use some stickers to liven her up a bit, guess seeing as the tests are finished I should do that.
The Flight Test
I'm extremely happy with the initial test flights, just a small prop/shaft/spinner balance issue that I've resolved already.
The heavier than standard weight is no issue, plane flies straight and landing is not too fast at all. The 1500w power is AWESOME, she flies on 70% or less most of the time which is plenty. Under full throttle she pulls like a bitch on heat and swinging the 14x8" prop has a real nice look as well. It has a truly ghostly sound on glide with the air running through the wind milling prop and stall is predictable but not overly aggressive. The CoG was perfect, trim changes are minimal and mainly due to torque and thrust of the 1500w driving the 14x8 when you hit full juice. The 5000ma x 5cell lipo is up to the task, and although I have not exhausted the battery in flight yet, that's the point of having 5000ma, so you can keep the battery within it's capacity to prolong it's life. I expect to get in excess of 8-10 min flying time for normal flights landing well within capacity. The test flight was about 5 mins duration and no power drop was experienced in performance. My advice to others thinking of a glow to electric conversion, go to it, you won't look back.
As a comparison I built another Great Planes Extra 300 for my son, but this time a identical prefab
kit with an OS 46AX and a scale muffler. Flight comparisons with both planes have proved the electric version out
performs it hands down in speed and climb. Estimates from those watching put performance of the 1500w at full power more like a 90 size glow motor but with none of the noise or oil.
What would I change to the specifications and power train selection at this point??
NOTHING!
I just need to fly it more, hell I love it so much I'm thinking big electric motors might become my passion over glow engines in 40 sized planes ;)
Thanks to HK for making it affordable.
Perhaps next a DH 98 Mosquito powered by 2x 1000/1500w motors swinging scale sized 3 blades ;)
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