With my SSE project nearing completion, I cleared off some bench space and kicked off my next build, a Sig Hog Bipe. I will build it as a “fantasy scale” early Army Air Corps plane with the blue fuselage and yellow wings color scheme. I am also thinking about some sort of custom cowl instead of the traditional Sig style open nose.
Of course I am planning an electric conversion. Sig calls for 6.5 – 7.5 lb all up weight and a 0.60 sized glow motor. For electric motor sizing, I’ll round up to an even 8 lbs and plan on 150 watts per lb, which will put me right at 1200 watts. I want to keep with 6S batteries (22.2v), which will then need to draw about 54 amps.
I like to have the motor on had when I start the build, so I can use the motor mount as a template to drill mounting holes in the firewall before assembling the firewall into the fuselage. I am leaning towards a Cobra C-4130-12 motor. Their site includes a prop chart which lists about 1120 watts with a 13×6.5 prop and just a tick under 1200 watts with a 13×8. The 13×8 prop (drawing 54 amps), is just a bit over the 52 amp continuous limit for this motor, so as long as I am not flying max throttle all the time, I should be in a safe zone.
Battery capacity may be an issue though. I am hoping to use the same batteries here as my SSE. For the SSE, I want to keep to 4000 mAh maximum in order to keep to a reasonable weight. But 4000 mAh may not give me enough flying time for a heavier plane drawing higher current. As always, there are trade-offs with electric set ups, and I need to digest on this a bit before I make my final selection.
Since I have not finalized motor selection, I will get started on the wing panels now. Given my slow build rate, by the time I am done there, I will have settled on a motor and have it in hand. I will be back traveling again this week, so I won’t even be able to start until the week after, though.