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.

Simprop Zaunkönig

The Simprop "Zaunkönig" ("wren", small bird) is a small biplane design from way back (30 years?). At the time it must have been the smallest commercially available RC kit. It was powered by a small cox engine, and with the RC gear of the time the weight resulted in a model that's fast and challenging to fly.

First flight on 05/05/2018.
Wingspan  410mm
Weight 290g
Motor 1000 RPM/Volt
Prop APC 7x4 SF
Battery 3S, 800mAh LiPo

Found a kit on ebay, and created my own CNC-cut duplicate from that.

Some of the parts:

Assembly (and sanding) required:

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.

Eindecker Model IV

Roughly 100 years ago, most airplanes had at least two wings. Biplanes. Anthony Fokker went against this trend. Based on his experience flying radio control airplanes, he was well aware of the "Ugly Stick" type of model airplane. So he created a full-size ugly stick, which became known as the Fokker Eindecker. Most people are aware of the Model III: Round engine in the front, machine gun that could fire through the propeller arc, wing-warping for roll control.

My model is about the lesser known Model IV variant of the Fokker Eindecker: Upright cylinder engine, ailerons. The cylinder block in front of the pilot provided a certain amount of protection from incoming fire, but unfortunately prevented mounting a machine gun, so the Model IV was mostly used as a reconnaissance plane. For this reason, Manfred von Richthofen had little use for the airplane. Nor had his brother, Lothar. But his girlfriend, the Baroness von Kräsch, loved the plane, which is why my model includes a replica of her in the control position.

Today, there is no surviving example of the Fokker Eindecker Model IV, mostly because I made it all up. My model is actually an 80% sized copy of the Balsa USA Eindecker 40 model which I had built several years ago. That one used an OS Max 40, this one uses an OS FS 26.

Futaba 9C Throttle Lock

To get a "Throttle Lock" for electric motors on the Futaba 9C while not in a heli mode:

• Select one of the programmable mixes
• SW: E, Posi: Down
• Mix: On
• Mas: Thro, Slv: Thro
• Link, Trim: Leave Off
• Offset: 0% (Throttle stick to idle, then hold rotary for 1sec)
• Rate 'down': +100%, 'up': -100%

Similarly for the T8FG:

• Offset Y at -100
• Rate -100 for both directions

"Throttle Hold" for RC boat or car

The Futaba T8 has a "smart" throttle hold option, meaning: The throttle hold will only engage when the throttle stick is close to the low position. Makes sense for an airplane or helicopter that uses a range of idle-to-full throttle. Does not help with a car or boat where you want reverse/stop/forward.

For a boat I wanted the throttle hold to hold the throttle output at 50%, but the built-in throttle hold function would only engage after moving the throttle stick near the full reverse position.

Fix: Use throttle curves.
Curve 1: usual 0..100% linear curve.
Curve 2: Always at 50%, with switch "SF" to engage, the same one I otherwise use for throttle hold.

Speedy Bee

Built from plans provided by KCRC member.

First flight around July 1, 2012.

Engine is OS FS-26.

Flies well, very not-speedy. Can fly inverted without dropping, loop in no space at all.

Is overall a bit flimsy because I decided to build it as suggested on plan with removable tail section, rubber-banded wing etc. Landing gear is very narrow, need to turn slowly on taxi to keep wingtips above ground.

Extra 3.25

First heard about the design as a Model Airplane News plan, designed by Rich Uravitch. Then found the Lanier kit version on EBay, got it for Christmas in 2010 together with a used OS FS 26. Unclear how old that engine is. It looks a bit more gummed up than my other 10-year old OS 26.

The Lanier kit has very nice laser-cut pieces which I wanted to preserve, since it's getting harder to find nice kits. So this plane was built by copying the pieces of the kit.

Everything came together quickly until it was time to assemble the middle section for which the kit provides a vacuum formed clear plastic part. Created a plaster mold, but failed to duplicate it because it was hard to get a suitably large sheet of clear plastic. Ordered a canopy from Tower for a 60-sized cup that appeared similar, but that piece arrived broken. So ended up creating the center section from scratch out of balsa.

The kit also includes a cowling which I didn't want to remove from the kit, either. Tried to copy it in fiberglass, which turned into a big mess. Then ordered a replacement fiberglass cowling from Fiberglass Specialities, but have not put it on because it's much easier to reach the engine without a cowling. The only part on this plane that came from the kit is the aluminum landing gear.

The kit suggests a weight of 3.5 to 4.5 lbs, but my plane came out just under 3 lbs! It appeared front-heavy, had to move the receiver battery into the back of the fuse to balance. Servos are 3 normal sized ones and a small one for throttle. One servo with bell-cranks for ailerons, no "flap" mixing option.

Wingspan	120 cm
Length	87 cm
Area	23.4 dm2
Weight	1330 g
Loading	56.8 g/dm2
Airfoil	Semi-Symmetrical
Engine	OS FS 26
Tank	120 cc

First flight was on the 2012/03/12. Engine runs fine, solid put-put-put, no screamer. The plane has a tank that only uses a third of the front section, and I don't know how long it will run, but after 4 minutes it's still 3/4 full.The plane feels very light and can fly quite slow. very easy to fly, like a trainer except maybe a faster roll rate.

Chipsair 2

Update of the first Chipsair that crashed due to unknown reasons.

Just lost it while spinning, maybe because the battery voltage dropped too far while tossing it around. Hence this one has a voltage display...

Update was build in very similar way to the first Chipsair but possibly a little stronger: Extra thin ply in the elevator, added bracing in the aft of the fuselage.

Wingspan	1.58 m
Wing Area	36.34 dm2
Tail	50 cm
Tail Area	6 dm2
Weight	2012 g
Wing Loading	55 g/dm2
Length	1.1 m
Airfoil	Eppler E197
Engine	OS MAX 46 LA (blue)

First flight on December 22, 2011, where I noticed at the field that the aileron hinges where actually not glued in, yet! So for the first flight scotch tape held them in place, and I tried to avoid aileron use to keep them attached to the wing.

The pictures also still show the push-pins on the windshield because I'm not sure if the glue is 100% dry.

This might have been the last plane where I could use the Pacer ZAP hinge glue that seems to become unobtainable.

Overall it flies GREAT. Plenty power, plenty authority from aileron and elevator, which I had worried about. Very nice and slow landings, while on the other hand endless loops and quite some vertical performance.

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.

Robbe "Geier" Flying Wing

Built from the long out-of-production Robbe "Geier" kit, which I found on eBay. Used the ribs etc. from the kit as patterns to cut pieces from balsa stock. Built-up fuselage instead of using plastic pod from kit, also using the transmitter's electronic V-tail mixing instead of the mechanical mixer from the kit.

Wingspan	1.5m
Area	46dm2
Weight	925g
Wing Loading	20g/dm2
Engine	OS-15

Flies slowly, but can also go fast, very easy to handle. Motor runs for about 5 minutes. Typical flight time is 8 minutes unless it catches a thermal. Lands in grass. Not a great glider, but fun to race around the sky. When up high and only a black silhouette, it looks just like a bird.

KCRC Model-of-the-Month August 2010.

Chipsair Wackeltest

A scratch-built airplane for testing the OS 'Wankel' rotary engine.

Wingspan	150cm
Wing Area	34.5dm2
Airfoil	Eppler 197
Elevator	6.25dm2
Stabilizer	3dm2
Weight	1700g
Wing Loading	49g/dm2

A basic high-wing design with a slight old-timer look. Building started with the wing, using the E-197 outline printed with Profili. The rest was designed ad-hoc based on which pieces of wood happened to be available and what 'looked about right' with maybe a little inspiration from the DeHavilland Beaver to get the stabilizer outline and some 'round' windows on the side. Details of the front were determined after the rest of the plane was already covered to locate the engine such that the CG would be at 25% of the wing cord.

To reduce stress on the wankel engine, full-throttle runs are limited. In addition, the oil content of the fuel is raised by adding 2oz castor oil per gallon.

The plane flies great, like a trainer, but with more than enough power for vertical climb-out after takeoff. Most of the time I fly at 1/3 throttle. At full throttle it can flip and roll like crazy. On landings, it bounces easily if still at 'floating' speed.

KCRC Model-of-the-Month July 2010.

List of Things

Things to try, buy, finish, ... in no particular order

• "Windspiel" that powers LEDs just for fun
• Steam Engine
• Steam Boat
• Elektric Jet
• P-40
• Auto Gyro
• Float plane
• Segelboot: http://www.victor-model.com, Soling 1 Meter, www.servocity.com for servo gearboxes, http://sourceforge.net/projects/sailcut/
• Oldtimer "Graubele Schulgleiter"
• 40,30,20,17,15 switched dipole
• 2-mot: B-25, DC-3
• Variometer, altimeter, http://www.wingedshadow.com Thermal Scout

Done:

• Traxxas Slash
• Linear Amplifier, abt. 500W
• Marklin "Ticket To Ride" game

Steam is Alive!

There is still stuff out there for steam engines!

http://www.toysteam.net/ has basic Wilesco and Jensen engines as well as Krick boat kits.

Put-Put engines might be the simplest steam engine to build at home, see http://sciencetoymaker.org/boat/makeBoat4_07.htm

Align TRex 600 OS 50 Engine Problem

After running great for month, the engine started to have a rough idle. Otherwise it seemed OK, especially it was not running hot. Eventually, though, it quit in flight. It has never been quite right since then: Rough idle, and when using the governor, the engine RPM seemed to oscillate around the target RPM.

After trying this and that, including taking it apart, eventually even getting a new engine for comparison, reasons for the problems seem to include:

• Rust on bearings. Unclear how that happened because I'm using after-run oil. It is because of the oil?
• Play in throttle serve

New engine in comparison idles down to a low put-put that I don't remember ever achieving with the original engine. Either I've gotten better at adjusting engines, or the previous one always had some imperfection?

---

Good entry about OS 50 Engine rebuild, everything except for removing the crank and bearings:

http://www.helituning.com/index.php/maintenance/engines/os50/237-os-50-hyper-max-engine-internals.html

Yes, be careful with the piston ring. It does snap easily when taking it off the piston, especially when it's brittle from having been in the engine a long time. On the other hand, a new piston ring goes on quite easily, snapping right into place.