Electric R/C Flight
By Heather Mardon
Part 3: Converting an IC Kit
Hi,
Rather than plough into brushless motors this month I’ve decided to cover the conversion of an IC model kit to electric power. Don’t worry we’ll get to the brushless motors in a month or two.
There are several factors to consider when doing a glo – ‘E’ conversion. Obviously some kits convert better than others, the objective was to find a model where most of the original parts could be used to save on time and money. For this exercise I settled on the Airsail ‘Volksplane" model. The reasons for choosing this kit were as follows.
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After weighing all the kit parts I came up with an estimated empty weight of about 1kg (35oz). Remember the ‘empty’ weight is the value without the motor, batteries and speed controller. Once these figures were estimated I was able to feed the numbers into my trusty Motocalc software to see if the motor I had in mind was up to job.
I was planning to use a motor/gearbox combination called an ‘ND10’. This is a Speed 600 sized motor but has Neodym magnets and exposed replaceable brushes. It also incorporates an all metal 2.3:1 gearbox.
The optimum setup seemed to be 9 x CP2400SCR cells driving an APC 11 x 7 prop. According to the predictions this should draw about 24amps and turn the prop at about 7300rpm full throttle. The thrust to weight ratio was about 0.62 : 1, seems like it should fly!
On to the Building
This is not a review of this kit so I’m only going to go over the area’s were I deviated from the plan.
Motor Mount
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Obviously the supplied glow motor mount was of no use so Ian went to work and came up with this little number made of lite ply and epoxied to the firewall (After some large holes were made in it) |
Tail Feathers
Wing
This was built almost stock, the only deviation was to replaced the standard servo/push rod/bellcrank assembly with individual Aileron servos using Hitec HS-81’s installed into a reinforced rib. (Yes there was a picture once…….)
Under Carriage
Radio Installation and Access Hatch
Covering
This was with a product called Oz Cover (No prizes for guessing its origin) which is an iron on clear film. We used two different weights, the standard one on the wings and the ‘Lite’ product on the fus/tail. It has no backing to remove and needs a very high iron heat (the ‘lite’ needs a bit less). Once ironed on a heat gun can be used to take out wrinkles. After that it’s ready to be painted with enamels.
Flying
The model was completed ready for test flying at 2am on a Saturday morning in preparation of attending the North Shore Model Aero club electric flyin on Sunday the 24th of Feb. Final all up weight ready to fly was 1705g (61oz) , this was bang on the box weight for the glow version! The maiden flight went well and showed no shortage of power with a couple of loops thrown in to see what it could do. The first landing approach was a goody so Ian touched it down sweetly.
Since then we’ve had another 3 or 4 flights on it. Average duration is about 8min so all in all a worthwhile project and a pleasant easy to fly airplane.
That’s all for this month, next month I’’ll have event reports from NSMAC and maybe the Hamilton electric day as well.