Convert a 1958 Mechanix Illustrated plan to electric
I have been flying traditional RC for 10 years and have a Mini IFO for after work fun. This is my first try in converting a slimer free flight to electric.
I have Burnelli Blended Wing Body Free Flight Model airplane plans from a 1958 Mechanix Illustrated that I want to convert to electric.
The wingspan is 51"
Overall Length is 31"
Over all area (fuse+wing panels)
499 1/8 sq inches
The Fuse itself has an area of 246 sq inches
The plans call for a pair of "O.K.Cub .099" engines.
What size motors do I need, what size battery pack am I going to need, and what size servo's would be good?
Are retracts practicle on a 51" electric?
This should be an interesting "floater", has anyone else flown a BWB with any sucess?
Bit of a SWAG, but two geared S400 6V motors, around 8 or 9" props, eight cells. The Graupner gearboxes are good quality and match up to their "Slim Props" well, while "Mini Olympus" are cheap and cheerful, need care in setting up but work fine at less cost. Wired in parallel, each motor would "see" all 8 cells, and current draw is 2 X what each motor draws on its own - that suggests a 30A rated ESC would be a good buy to give a little flex.
Servos - Hitec HS81 or thereabouts in size would do fine. Small RX, no need for a RX pack as the BEC on those small ESCs would do fine.
Sounds like you've been doing this long enough to build a decent, light and straight airframe. Watch out that the structure has wood where needed, it's an old design and there's no point in adding weight. The amount of "mounting" for a Speed 400 motor is almost laughably little compared to what's needed to hold down a small glow engine.
Covering - you'd want to go as light as you can. Litespan is great, or Fibrafilm. Monokote is not, at these sizes.
Retracts - possible, but only if you really must. At this, it would have to be the Robart mini units, or I understand Spring-Air do smaller units now. Be inclined to either go with fixed, or even more so, forget the gear and handlaunch at this scale. Anything but tarmac and smooth landings will give you grief, plus the weight increase is not good on this small a model.
Fascinating project, would love to hear how you get on.
Quick tip - go check out MARCEE - Minnesota electric only group's pages, has a lot of info on small multi electric motor models.
Another good spot - have a scoot around: http://members.aol.com/kmyersefo/index.htm#TOP and Keith Shaw's articles, all good stuff.
Thanks for all the great information.
The following link is another Burnelli flying in the North East, I think Pennsylvania. But he showed off at Old Rhinebeck classic model day.
It's a slimer, but a beauty just the same.
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