I recently bought a Sony U20 and nearly lost it on it's second flight due sending up the Slow Stick in too much wind. So I started looking for a replacement plane. I wanted very low wing loading and fairly low drag. This turned out to be pretty elusive and I ended up finally just building my own.

I wanted to make the tail a little more rugged, so I cut some balsa and spruce pieces and covered them with Oracover. I glued them directly onto the fuselage using Gorilla Glue. A substantial improvement in stiffness for a mild cost in weight.

For the wing, I got creative and took a page from the SPAD guys. I took four pieces of 2'x1' Zepron 1/8" foam, taped each pair of them them together end-to-end, then I took a chunk of balsa 1"x1"x36" and glued it firmly in place about 33% away from what will be the leading edge on one of the taped pairs. Once this was dry, I sanded down the two top edges, and ran a big piece of clear packing tape along leading edge and then taped the other pair edge on, ran gorilla glue across the top of the spar, and then flipped the second pair over the top. I waited for the glue to dry and then I cut off the excess off of the bottom panels, and taped the back end of the top and bottom panels together.

This made a good, solid flat-bottom wing that's 48"x12". It's very stiff - 1"x1" balsa is a bit over the top, and thus results in essentially no flex at all. I added ailerons to the wings using more spare balsa and Oracover. Not counting glue-drying time nor time to build and attach the ailerons, it took about 15 minutes to make the wing.

Wing area: 4 sq.ft.
AUW (w/o camera): 20.5oz.
Wing loading: ~5oz/sq.ft.


PJS 800E motor
CC Phoenix 25 ESC
3S TP2100 lipoly battery
HS-81 servo (elevator), 2xHS-55 servos (ailerons)

I maidened it this morning, and I was pleased. It didn't need any trim. It glides extremely well and can float down to a walking speed landing using the flaps. It is pretty responsive and I could do very slow Cuban-8's with it. The angle-of-attack of the wing versus the motor is off a bit... I need to lower the leading edge a bit. But overall I was very pleased. More noticeably than anything it glided noticeably better than a regular Slow Stick wing.

This afternoon I decided to fly it in winds to see how it did. According to Wunderground.Com's nearby weather station, it was blowing around 15mph. It flew well, although it got pushed around a fair bit. Not as bad as a SS wing would have, but not dramatically better. On the plus side, the wing had no problems with flex and the motor was definitely faster than the wind and I was able to do pretty fast fly-bys straight into the wind to see how the 'airframe' held up. I didn't see any flexing on the surfaces anywhere, although the linkage to the elevator was flexing a bit. The plane got pushed around, but it felt 'solid'.

For the less windy days, I just need to hook up the rudder and then I can use the stock SS wing as well. So I will have any easy changeable choice between the lower-drag Zepron wing and the higher-drag SS wing depending on the weather.

Very cool!!

Nice looking plane, glad it flies well, now try it with a camera

ash

Nice looking plane, what size prop using are you using with that motor. Do you know how many amps you're drawing?

Jags

Thanks. I did grab some photos right after work. I had the camera positioned too horizontal - so the wing is in the way more than it should be. I'll work on a camera mount tonight.

It's a 10x4.5 APC. As I recall at max throttle it's around 18A.

Always nice to see another original AP platform. Looks like a good quality build. Looking forward to seeing your U20 mount.

Originally Posted by Radiofly

Always nice to see another original AP platform. Looks like a good quality build.

Thanks

Looking forward to seeing your U20 mount.

Yeah. Me too. I'm sitting here staring at a pile of balsa waiting for inspiration to strike.