Graupner Klemm 25

The original Klemm 25 was first available in 1928 as a light two-seat touring and training aircraft. My model is based on a Graupner Klemm 25 kit from a lucky EBay find, which then became a Corona Summer of 2020 project. Built as per instructions, except replacing the vacuum formed part for the cockpit with strip-planked wood. Fuse is covered with cloth/epoxy, wings and rear with 'Nelson light fab'. All coloring is Tamiya paint, both glass and rattle can. Filled the cowling from the kit with plaster, then vacuum-formed a copy to have replacement part. Pilot is 3D printed.

Wingspan	130 cm
Weight	830 g w/o Battery
Battery	3S 2200 mAh Lipo, 185 g
Motor	Speed 400, gear

Full-throttle current draw is 10 Amp, 120 Watt. First flight in June 2020. Motor's gearbox is quite loud. Barely climbs at full throttle, but can fly nice slow circles at 1/3rd throttle. Uses about 100 mAh of battery capacity per minute flight time. Makes for enchanted early morning or late evening flights in zero wind. Very convenient that whole plane fits into car, no need to remove wings etc. Only downer are the water-slide decals. As applied from the kit, the transparent backing shows up shiny/silvery. Tried to 'melt' them into the paint by dabbing with vinegar as well as acetone. The latter helped a little, but masking and then spraying the numbers would have been way better.

Graupner BO 209 Monsun

The original Bölkow BO 209 "Monsun" was built around 1970, with almost exactly 100 copies being manufactured. As long as I can remember, Graupner always had at least on model in their catalog, from a small free-flight, rubber-powered variant to larger R/C types.
This model is based on a plan of the older 1973 Graupner kit for a 40-sized model.While the kit included foam-core wings, the rebuild has traditional ribs-and-spars balsa wings.

Wingspan	1.5m
Length	1m
Weight	2180g (kit used to be 2700g)
Motor	AXI 2816/12 V2, kV 760
Battery	4S 3000mAh LiPo
Prop	12x8
Max current	40 Amp

First flight: Evening of April 1, 2018.

Initial cockpit detail.

Special challenge in the rebuild were the bubble canopy and the motor cowling, which were vacuum formed. Above is example of the wooden cowling plug used to pull the cowling.

Graupner Chico

Built from plans, but with electric motor, removable wing, hatch on nose for battery replacement.

Weight	830 g
Prop	9 x 5
Battery	3 cell LiPo 2200 mAh
Max Current	18 Amp

First flight on Sept. 22, 2017. Roll rate with mostly original aileron setup is a little underwhelming, and slight tendency to pull down with increased power. But generally easy to fly, floats nicely, very gentle stall.

Most important: Terminally cute 70s look.

Graupner Mosquito

Graupner offered the Mosquito kit from about 1975 on. At the time, it was one of the first electric (under-)powered gliders, also usable as a pure glider, or with a 0.8 to 1.5 ccm Cox motor.

What's somewhat special about it is the sleek nose section, accomplished by moving the electric motor back from the front, using an extension to the prop.

Built from plan in about 6 months. Total weight in the original glider version was 1100g. With 'Jumbo 540 F G6' motor, 6:1 gear and NiCd battery, it was around 1600g.

Wingspan	2500 mm
Length	1100 mm
Wings Area	44 dm2
Tail Area	7.5 dm2
Weight	1300 g
Motor	MVVS 2.5 1350
Prop	9 x 5, folding
Battery	3S LiPo, 2200 mAh

First flight June 3, 2017. Very slow, majestic, low sink rate, flat glide. Typically flights of about 15 minutes require motor run time of only about 3 minutes, leaving the LiPo 80% charged.

Graupner Bugsier

Very slow progress, but progress nevertheless over the holidays on Graupner Bugsier.

Graupner Cherry Rebuild

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.

Graupner Amateur

Built by using parts from an original kit found on EBay.

Wingspan	110 cm
Area	18dm2
Weight	650g
Motor	Atlas AM2312/26
Prop	9x6
Battery	3cell LiPo, 2200 mAh

Started building just before Christmas 2013, first flight on 1st of March 2014.
Compared to the original, built as tail-dragger and with electric motor. Hood and front window are held by magnets, removed to access battery. Completed weight matches what original estimated for the free-flight configuration, without radio!

Flying it couldn't be better in no-wind conditions. Current draw is up to 10Amp, but plane still slightly climbs at 1/3 power, so full throttle is rarely necessary.

I happened to have grey Monokote around, so I tried to cover it as shown on the kit's box art. I'm surprised how pleasant the color combination turned out. The lettering and "Graupner" logo were cut from Monokote based on copies from the plans.

Dandy E205

This is not about a high-performance sailplane but about building something that you knew about maybe 30 years ago...

Graupner used to have a glider kit called "Dandy". I found a new-old-stock Dandy kit offered on eBay, but it went for what I considered way too much. So I decided to build something similar to the Dandy, and luckily found the web site http://www.koralpe.biz/dandy.html which has nice pictures of the original kit and a plane built from it.

I had also read about the Eppler 205 airfoil, both good and bad, so I decided to try that.

Finally, the "glider" should have an electric motor because using a high-start is somewhat cumbersome. The motor and prop combination was determined by trying various things in online motor calculators and by comparing with off-the-shelf models of similar wingspan, weight and type.

Wingspan	170cm
Length	105cm
Airfoil	E205
Stab	E193, 50 x 11cm
Wing Area	39.1 dm2
Weight	1156g
Wing Loading	29.6g/dm2
Decal Font	Optima Extra Black
Motor	Turnigy C3530-1100, Kv1075, 73g, 15A Max, later MVVS 10 2/1120
Prop	9x5 Folding Prop
Speed Controller	25A max
Battery	2200mAh 3S LiPo

The center of gravity came out somewhat too far in the back unless two batteries are packed into the front of the plane. The total weight of about 1.2kg includes the two batteries and radio gear. The original plane had a slightly smaller wingspan, weight of 1.0kg, and a wing loading of 16-29g/dm2.

First flight was on the morning of August 28, 2011. Two brief flights before breakfast. It flies nicely! I was surprised how slow. Current draw is 13A at full power, and about 5A when cruising around.

--

17 July 2016: Axis of Turnigy snapped off (!) during climbout. Managed to land ok, but prop vanished in the woods.
Replaced with MVVS 10 2/1120. On summer evenings using about 400 mAh for 10 minute flight.