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Andy Lennon's Robin in flight

Robin Kit

The STOL Robin represents years of engineering and design development by Andy Lennon. From the wing design to the calculated relationship between the horizontal tail and the flaps, the Robin is a masterpiece of model engineering. See what makes the Robin an exceptional STOL design.

Quite a different kit then conventinal designs For those modellers who recognize the internal structure of the STOL Robin here, may see where the FastFit system has changed the way the parts look, yet function exactly the same. The new system allows assembly parts to self-lock straight and true. Have you ever wanted to test the assembly process first before you use glue? This example shows how the builder can dry-fit parts to become familiar with the structure first, then go at it with complete understanding and confidence.

Note how large the receiver/battery compartment is. A lot of business is handled in this self-jigged cage that sets the whole fuselage straight and true.

Everything from the wing mount to the main gear plate - all loads and stresses are contained in this tight structural cage.

Lots of Fuel or Battery room Stressed skin construction

There is no internal structure from the wing back. The carefully laser-cut walls assemble in a unique method to produce a stressed skin fuselage. All the strength and none of the usual weight is the end result. This normally challenging method of construction is now reduced to a quick and easy assembly process that takes all of the worry out of the build.

Andy has provided modellers some additional information about his Robin, along with take-off and landing instructions. For your enjoyment, Andy’s notes to the builder from the Construction Manual:

The Robin is a versatile model airplane, with a wide speed range, that can take off and land in either of two modes, the conventional mode or the STOL mode (short take off and landing) made possible by several unique features which are described below. It is a "fun" airplane.

The Robin uses Slotted Flaps
The wings feature large slotted flaps that cover 65% of its trailing edge and when extended 40 degrees, virtually double the lift of that 65% of wing area. The wing's airfoil is the Eppler E197. It's aspect ratio (ratio of span to chord) is 6. It has low profile drag and a gentle stall at 20 degrees AOA out of ground effect. Its zero lift AOA is minus 2 degrees.
The Robin's Flaps extended Ahead of the ailerons, the E197 airfoil is modified to NASA development leading edge extensions and droop that do three things; the stall is delayed a further 9 degrees, aileron control at high angles of attack (AOA) is effective and there is no tip-stalling, important for STOL landings.

The fuselage, when the model is on its three wheels, is inclined upward 10 degrees. The wing is set at plus 2 degrees to the centreline and is therefore at 12 degrees angle of attack; moving forward the wing lift is close to the maximum, but below the stall. With flaps half extended and in ground effect, the stall is at 17 degrees. This permits the short take off.

Andy Lennon's Robin
The landing gear in conventional or "tail dragged". With all three wheels firmly on the ground, the model is directionally stable and is maneuvered by the steerable tail wheel, linked to the rudder control. With the tail wheel off the ground, however, the model is directionally unstable; this calls for careful rudder action to prevent the model from veering which it is prone to do!
OS .46AX, Such a nice engine The recommended power for the Robin is the OS MAX .46AX engine that turns the recommended APC 12X7 prop at 10,000 rpm. producing thrust estimated to equal the model's fuelled weight. This provides a steep climb. Minimum level flight speed, flaps fully extended, is 20 mph and 80 mph in full speed level flight; flaps up. For low drag, the engine is enclosed in a ducted cowling. The lower half of this cowl is easily removed and replaced for engine servicing, such as glow plug changes. A remote jack permits glow plug lighting safely away from the lethal prop. Engine cooling has not been a problem.
The Robin's clean design The horizontal tail is positioned low in the fuselage where it is in the prop's powerful slip stream. The elevators are 40% of the tail's area and when raised cause the tail wheel to rest firmly on the ground under slip stream pressure. To taxi, hold "up-elevator". which provides good steering and prevents "noseovers" should the main wheels meet an obstruction like long grass. The flaps, when extended create considerable turbulence. The large dorsal fin ahead of the vertical tail provides good directional control despite the turbulence.
Hitec Radio A 6 channel transmitter-receiver is recommended with a 3 position snap switch for flap control; up, 20 degrees down, and 40 degrees down.
The Robin has bags of control The ailerons have heavy differential (20 degrees up and 10 degrees down) and are top hinged with modified Frise features that eliminate adverse yaw. The model turns on ailerons alone without rudder input.

The Robin is spirally stable. Put in 20 degree bank and controls centred it will return to level flight on its own. It will fly inverted, but requires a healthy amount of down elevator (inverted down elevator is up-elevator).

The two modes of take off are conventional and STOL. In the conventional, the model is pointed upwind, flaps half extended, and the throttle slowly opened. As the model accelerates, the tail comes up and the directional instability raises it's ugly head. Torque and gyroscopic precession cause a swing to the left, calling for just the right amount of rudder. Over control results in a swing to the right and danger of a ground loop. This is not imaginary, it has happened! At 20 feet of altitude, raise the flaps, level off, and the plane is up and away.

Robin in a gentle to landing
For the preferred STOL stake off, point the model in the the wind, lower half flap, hold enough up elevator to keep the tail-wheel firmly on the ground and open the throttle wide. On a calm day, take off run is under 4 feet; on a day with wind of 10 to 15 mph, the take off is almost instantaneous followed by a steep climb. At 20 feet, raise the flaps, level off and the plane is away. Directional control on the ground is good and torque and gyroscopic precession are avoided.
Full flapsRobin in slow pass There are two types of landing, the low wind STOL landing and the high wind landing. On a low wind day, do not try to land flaps up. The glide is fast and flat; overshooting the landing area is probable. Instead throttle to idle, lower full flap; the added lift and drag permits steep approaches at relatively low speeds. There is little or no change in the model's attitude with flaps lowered fully, just a noticeable reduction in speed. The objective is to have all three wheels touch down simultaneously at a speed just above the stall, which is (flaps fully down and in ground effect) 14 degrees. At an AOA of 12 degrees, the plane is just below the stall. Ground run 4 feet. It's when the "no tip-stall" feature is so valuable. The wing area ahead of the flaps may be stalled but the two outer panels are still lifting with effective aileron control.

On a windy day, land flaps up with a bit of power. A model flying at 30 mph into a wind of 15 mph has a ground speed of 15 mph. Rather than a full stall landing, land on the main wheels first, closing the throttle to idle just before touchdown.

The Robin will spin but very reluctantly; the spin has to be forced by full up-elevator and full rudder offset. After 3 or 4 turns, the spin will convert to a fast spiral dive, speeds of well over 100 mph are possible - the model has low drag - so do not omit the mass balancing of the ailerons, elevators and rudder which will prevent "flutter" at high speeds. Enjoy the Robin and happy landings!

On a later note, Andy offered more information about landing with full flaps:

Lowering flaps while at altitude will create substantial downwash. The downwash will hit the horizontal tail and influence it's attitude. Pilots must be careful to note that while landing with full flaps, you will eventually come into ground effect. At that point, the downwash over the horizontal tail will be reduced due to the pressure from the ground. The Robin will pitch down slightly as the downwash pressure eases off the horizontal tail, so pilots should be ready for it when approaching with full flaps.

Wing Chord
11.45" (avg.)
19.56 oz./sq. ft.
OS .46AX / 900W Electric
Bisson #1000
APC 12X7
6 channel (computer not required.)
Fuelled Weight 112 oz

Questions about the Robin construction can be
found in the Robin FAQ
Andy Lennon's Robin: Big Kit!
Test Pilot trying to make off with big new airplane

Robin Manual For customers who Are looking for a copy of the Robin Construction Manual, you can download the PDF here.

Price does not include shipping or related shipping charges.

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