Had flown a Graupner Cherry II when it first came out. Was comparably heavy back then with NiCd batteries and somewhat under-powered.
Recently found one on EBay, which had a fiberglass fuse compared to the soft plastic fuse of my earlier one. Unfortunately, crashed on the first landing. Reason was probably that I had the airlerons mixed to both move down to slow the plane for landing. While the plane did slow down, it also suddenly rolled over and fell out of the sky.
Decided to build up a Cherry look-a-like as a purely wooden construction. Used the one remaining wing from the crash as a template. Compared a scanned copy of the airfoil with others in Profili, found a good match in the Eppler E211. The wing is fully sheeted, with a slight undercamber. To build the wing, the bottom sheeting was placed onto standoffs with a contour matching the underside of the ribs; ribs and spars were added, then the top sheeting.
| Wingspan | 2.2m |
|---|---|
| Length | 1.02m |
| Wing Area | 35.5dm2 |
| Weight | 1.250 kg (with battery) |
| Airfoil | E211 |
| Motor | MVVS 3.5/1200 |
| Battery | 3cell LiPo, 2500mAh |
| Prop | 10x6 Aeronaut CAM |
| Max Current | About 30 Amp |
First flight was in January 2015. Rapid vertical climbout on full throttle. Can easily take off on half throttle. Slows down nicely when just gliding around. Now pulling ailerons 'up' for landing instead of 'down' to avoid tip-stalls. Still needs long approach because of flat glide path.
What would have been nice: Rudder control for better looking tight circles, and inner wing flaps for landing.
Still, fun airplane and the MVVS motor turned out to be terrific: Easy to mount in comparably tight glider noses, amazing climbout. Example for flying it one summer morning: About 2 minutes of motor runtime resulted in 18+ minutes of flying!
On another summer morning, achieved a 28 minute flight with 4 minutes of motor runtime. Still having trouble spotting thermals "right then" when flying thought them, but at the end of a flight it's pretty obvious when there must have been some. KCRC Model-of-the-month in August 2016.
Posts
No comments:
Post a Comment