Extra 300L

Identical ARF Planes: Black Horse "Matrix" / Graupner "Leki"

Table of Contents [Toc]

Specifications
The Final Plane
Comparison
Construction

Specifications [Toc] [Top]

Manufacturer:	Black Horse Model, Vietnam
Wingspan:	160 cm
Length:	140 cm (incl. spinner)
Weight:	approx. 3.3 kg
Engine:	"Matrix": Magnum XL-91RFS four-stroke engine "Leki": O.S. MAX FS-91S II-P four-stroke engine with pump system
Propeller:	"Matrix": APC 14x6" "Leki": APC 14x7"
Controls:	Engine, Elevator, Ailerons, Rudder
Description:	Both ARF aircraft models are manufactured by Black Horse Model in Vietnam, and are identical in construction and realization. Wing and fuselage are completely built from wood. While the genuine Black Horse Extra 300L "Matrix" has a two-color trim scheme, the Graupner Extra 300L "Leki" is entirely covered in red. The main difference between both model kits are slightly higher-quality small parts shipped with the Graupner kit, e.g., screws and control horns. Note that the Graupner "Leki" is no longer manufactured.
Pros:	i) Profiled and completely balsa sheeted fin and horizontal stabilizer, resulting in very warp-resistant structures. ii) Rather thick symmetrical wing profile allows for decent approaches without critical low-speed behavior. iii) Supplied wheel pants contribute to overall appealing look. iv) Decent and neutral flight characteristics, well-suited for aerobatics. v) Kits are usually reasonably priced.
Cons:	i) Aluminium landing gear is quite weak. Even minimal bumping during landing causes gear distortion. I've replaced the supplied landing gear with a suitable carbon fibre composite (CFC) variant: I've mounted a 20cc-sized CFC landing gear (ID: HK320-135) from hobbyking.com, which perfectly suits in size. It is a very recommended replacement part for any 1.6 m aerobatic sports plane. ii) The supplied metric metal screws are of cheap quality. I replaced the landing gear and engine mounting screws with quality versions, which are nicely threaded.
Notes:	i) The color scheme of the Black Horse Extra 300L "Matrix" is more convenient during aerobatics, since top and bottom views differ a lot more. ii) Replaced supplied red plastic spinner with polished aluminium spinner. iii) Added yellow foil stripes to the nose section of the wing in order to have better visibility during landing. On our small model airplane aerodrome, landing procedures could include blinding sun light and dark trees as background, so increased contrast is welcome, especially for rather heavy or fast planes.

The Final Plane [Toc] [Top]

May 2010: The completed Extra 300L "Matrix"* from Black Horse Model.*	Right side view showing the individual servo for each elevator control surface.
Top view of the "Matrix". It is noted, that the vertical and horizontal stabilizers are profiled and completely balsa sheeted. Hence, they are quite warp resistant.	Left side view showing the large control surfaces.
Bottom view with blue-striped design of the Extra 300L "Matrix" from Black Horse Model.
April 2011: Extra 300L "Matrix" with yellow foil stripes at the nose section of the wing in order to have better visibility during landing on our tiny airstrip.	The yellow foil stripes at the nose section of the wing are especially helpful if you encounter blinding sun light and dark trees as background during landing procedures.
May 2011: Most recent picture of the Extra 300L "Matrix" with polished aluminium spinner, new perfectly fitting 20cc-sized CFC landing gear from hobbyking.com, and new O.S. muffler (spare part of O.S. MAX FS-91S). The original Magnum muffler was damaged due to excessive thermal and mechanical stress (heat combined with vibrations). Therefore, changed muffler installation to get increased airflow for replacement muffler.

Comparison [Toc] [Top]

The boxes with two Extra 300L: Black Horse Model "Matrix"* and Graupner "Leki".*	Inside the two boxes.
The two manuals. The one from Black Horse Model features a much more beautiful cover, but the content is essentially identical.	Top view of two identical fuselages: "Matrix" at top, "Leki" at bottom.
Front view of two identical fuselages: "Matrix" at right, "Leki" at left.	Another front view: "Matrix" at right, "Leki" at left.
Side view of "Matrix" at top, "Leki" at bottom.	Bottom view of "Matrix" at top, "Leki" at bottom.
The inside of the fuselage: "Matrix" at right, "Leki" at left.

Construction [Toc] [Top]

The completely installed Magnum XL-91RFS four-stroke engine with fuel filter.	The Magnum XL-91RFS drives a 14x6" propeller.
Top view of the engine compartment.	Bottom view of the engine compartment.
Engine compartment showing muffler with attached silicon exhaust deflector.	The silicon exhaust deflector is secured with a small cord in order not to lose it during flight.
Note that the above displayed muffler installation has been changed in spring 2011, because it exhibited excessive thermal and mechanical stress on the aluminium muffler. Since the engine is based on a pressurized tank system, any damage in the exhaust section causes flucutating fuel pressure, hence reduced engine reliability during operation, especially within aerobatics. By employing a new muffler, the integrity of the fuel supply could be re-established. The altered muffler installation using a new O.S. muffler (spare part of O.S. MAX FS-91S) is shown above in the plane section.
After some flights, the steel throttle arm of the Magnum XL-91RFS four-stroke engine came a little bit loose from the aluminium rotor. This issue was ultimately caused by engine vibrations, and as a consequence, had detrimental effects on a reliable and stable idle run. I had to re-tighten it using pressure and glue, and I also applied some thread lock compound to the low speed needle valve to prevent it from unwanted alterations. Basically, I consider this story as one of the subtle but important differences between a high-quality O.S. engine and an economically priced chinese derivative. Nevertheless, working around the aforementioned issues still lets you enjoyably perform R/C modeling with a cost-effective chinese engine.

Last updated: 2011/07/23

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