Models I
The famous American two seat light sport plane sport scale model. Original
was produced in 1938-47, more than 14.000 planes.
Built and flown by Alois Raffaj. Great Planes kit electric conversion.
| Dimensions |
| Span |
2 285 mm |
| Wing area |
72,5 dm2 |
| Empty weight (estimation) |
4 000 g |
| Flying weight |
6 000 g / 24 x 1900 |
| Wing loading |
83 g/dm2 |
| Drive |
| Motor |
MEGA S7 |
| Gear |
belt gear 2,4:1, self designed |
| Prop |
Bambula 16 x 8 |
Building remarks
Model is of classic design, some parts are overdimesioned and the used balsa is
often very heavy. Plane is covered with the "Cub" yellow Solartex imitating the
original covering perfectly, but is a little bit heavier. Because of quite
complicated wing mounting it is not possible insert the battery under the wing.
That's why a battery box is made of 2mm ply and placed between the fire wall and
gear bulkhead. The hatch is on the bottom. After the crash the firewall and main
bulkhead were remade from sandwich ply-balsa-ply to reach less weight and
original thickness. The gear mounting plate was lighten by two holes (this saved
30 g).
The motor controller is JETI JES60. The receiver is supplied from the 4 Twicell
1600 mAh pack. Model is controlled with the FC-18 transmitter.
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Flying
Model has enough power for basic aerobatics. Flying characteristics are
realistic, "Piper like". Model has unbeliveable low minimal speed. When slowing
down its reaction is also slowing down. Flying time with Sanyo 1900mAh NiCd is
between 5,5 and 7,5 minutes, with Sanyo 3000mAh NiMh between 8 and 10 minutes.
When the Great Planes floats were used the flying weight reached 7,2 kg and
weight loading 99 g/dm2. The electric Piper has enough power for
raise of water. Because of greater drag more throttle is necessary.
What to improve next time?
1. Many heavy parts could be replaced and up to 500g could be saved.
2. Motor is running on its limit and good cooling is necessary. Some bigger
motor (MEGA L) or bigger LRK (MEGA Magic RC 41) could be tested
3. The aerotowing hinge is planned to be built in (probably the 18 x
8 prop will run better in this case). I think aerotowing the gliders of
3-3,5 kg is possible.
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The American golden years sport plane sport scale model.
Built and flown by
.
Inspired by
this picture
of
model published on
E-Zone. Model was bulit from TrueScale(USA) plan, drawn by Frank
Mizer.
| Dimensions |
| Span |
1650 mm |
| Wing area |
34 dm2 |
| Empty weight |
1 715 g |
| Flying weight |
2 380 g / 10 x CP1700 |
| Wing loading |
70 g/dm2 |
| Pohonná jednotka |
| Motor |
AXI 2820/10 |
| Prop |
APC E 11 x 5,5 |
Building remarks
Model is of classic design, except the main spar made from carbon tube.
It is covered with Solartex what is fantastic material for working with but is
of higher weight. Execpt the basic functions also flaps and high emissions LED
lights are controlled. The lights are controlled and supplied via the module
produced by the Czech company BEL. This module plus 4 standard servos are
suplied from the TMM40 controller with BEC. The lights can be switched on via
separate switch and also with full flaps. Model is controlled by the FC-16
transmitter.
Flying
Despite the model is little bit heavier than expected the current drive seems to
be of enough power. The flying time is up to 6 minutes with careful throttle
control, what means the average current is about 15A. Using higher capacity
cells will bring longer flying time.
What to improve next time?
1. The landing gear is very hard. It could be better to have softer
gear or design with adjustable strength.
2. Wheel pants and motor cowl - these parts were made from balsa. Moulded
GFK parts will be lighter and more durable.
3. Flap hinges - they are made same way as ailerons hinged on the wing
top side. Next time I will make flaps with rotating axis below the wing.
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American racer sport scale model
Designed and buldt by P.Doubrava, current owner
.
Original plane was designed and built in 1928 - 1932 by Wernon Payne and was
named Knight Twister. With 33kW engine it was successful pylon racer.
During 1971 the modified Knight Twister with Lycoming O-290-D2 engine of 100kW
started it's another successful pylion race career - new world record of 309.53
km/h in its category in 1984.
| Dimensions |
| Span |
1 300 mm |
| Area |
53 dm2 |
Flying weight
|
2 500 g / 12 x 1700SCR |
| Wing loading |
47 g/dm2 |
| Drive |
| Motor |
AC MEGA Magic RC 41 |
| Prop |
Aeronaut folding 15 x 8 |
| Flying time |
5-7 minut |
Building remarks
The base is a foam last covered with 1.5mm balsa. Wing with symetrical airfoil
has a D-form. Upper wing is fixed to pylon of wood and balsa, the interwing
struts are from 6mm light balsa. The tailfeathers are made of 4 mm balsa sheet,
Landing gear is made of 3 mm piano wire, with aditional reinforcement. Wheels
are light. Tailwheel is controled from rudder. Ailerons are controled by one
servo, all servos are of standart size.
Výkony
Original cell pack Sanyo 1700 was about 4 years old with some cells renewed.
Calm flying without lot of aerobatics the flying time is about 6 minutes. With
more aerobatics the flying time is about 4-5 minutes.
Now the GP 3300 Nimh pushed cells are used - the flying time is about 8-10 min.
The throttle matters, the plane is flying also below half throttle very
realistically.Model is able to start on half throttle, with full throttle it is
overpowered. Full throttle is used for vertical maneuvres only. The minimal
speed is very low. Also behavior on minimal speed is very nice.
What to improve next time?
1. Make bigger ailerons or ailerons on both wings - rolls could be then faster.
2. Landing gear is too weak. The piano wire shall be of larger diameter or fully
redesigned.
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