Alistair Potter's RC plane tips.
Frankenplane 2 – The "FOGEE"
AUW - 670 grams 23.6ozs with a 1000mah LiPo.
Drive - EMAX CF2822 1300KV 16A motor swinging a 9 x 3.8 prop.
This is a rebuild of my Smash Drone, but as a tractor airplane!
Both planes use the very versatile, simple and efficient Old Fogey wing. The Smash Drone is a great plane but it didn't translate too well in my version; I had a heavier tail boom and was using heavy foam board. To get it flying the way I liked it I had to reduce the wing's Angle of Incidence.
There was a balance issue as well. Even with 2x1000mah batteries in the front, I was still carrying extra dead weight. All Up Weight was just short of the kilogram – slightly over 35ozs – which must have been on the edge of that efficiency down slope where adding extra battery weight actually starts to eat into the overall flight time.
Carrying so much weigh it would never be as efficient as the Dollar Tree foam board versions. It was time for a bit of remodelling.
Here's what I did;
Turning the power pod around to make it a tractor plane was the first decision – and I carefully worked on balancing the plane before fixing the position of the front support for the swappable pod. That way I was able to avoid the need for any dead weight – right away I had a big weight reduction!
Because I didn't need the high fuselage to give the prop clearance over the tail boom I was able to reduce the fuselage depth, which reduced the weight even more.
The new AUW now stands at 670 grams 23.6ozs with a 1000mah battery. If you're used to building with Dollar Tree foam board this might still seem heavy, but the Old Fogey wing carries this weight easily.
This 'new' build weight is definitely better than the original 1020 grams 35ozs – that's a weight reduction of about a third!
Power now comes from an EMAX CF2822 1300KV 16A motor swinging a 9x3.8 prop. I also used some washers behind the motor mount to put in a couple of degrees of down and right thrust – which usually helps keep things stable over a wider speed range.
I've found the Old Fogey wing produces a tremendous amount of lift at anything over a crawl, so I kept the wing's Angle of Incidence fairly shallow (roughly the same as the donor plane). See my discussion on how and why I reduced the A of I in the Smash Drone article.
Internals are pretty much as they were. I reused the pod mounts – turning and repositioning them to fit the new layout.
A little trimming, folding and gluing tidied up the nose.
So how does it fly? Have a look here;
This video covers flying conditions from around 5–6mph initially to about 10–12mph near the end and still rising. It was very stable and well behaved. At times I just cut the power and coasted around for a few long lazy loops. It did lose height, but given the right conditions I think this plane would manage to fly as a slope–soarer. There's no slow motion in this video, just the headwind sometimes making it look like it. Being a 3–channel plane, it takes a little effort and planning to get it to roll, but looping is no problem. CG is at the apex of the wing fold.