- Roberto Bonafede with his Bronze medal WC F5J
pictures of podium winners HERE
- 4th F5J WORLD CHALLENGE TRNAVA CUP 2019
1st Roberto Bonafede ITA, PRESTIGE 2PK
Vlastimil Vostřel won
preliminary rounds and got 2nd in the finals of this years F5J Loire Valley,
Contest Eurotour . Vlastimil flew his new Prestige 2PK from Samba Model.
- Jo Grini got 2nd place in
Czech Championship / Samba Cup 2019
- Sebastian Feigl flew his new Prestige 2PK to a perfect 7000p score in
preliminary rounds and 3rd place in the finals Burgau, Germany.
A few words from the producer Samba model
First of all thanks to Philip Kolb for constructing an exceptional model in the
F5J world. He was not influenced by various fads in the F5J world and used all
his knowledge, experience and best available software to construct the amazing
To this we added the full rohacell core to the design, the whole model is made
in heated aluminum molds to a very high temperature. This technology creates a
light, strong and stable platform for years of flying.
It is worth mentioning a few properties we have found very nice after flying
this model for a while.
In circling the model as expected did not have a need for extreme dihedral
joiners since the aerodynamic design and airfoil changes does that work in a
better way than increasing dihedral. It was first produced with 6 degree tip
joiners and then we added an 8 degree alternative. It has also been flown a lot
with 5 degree joiners with good success in low altitude thermalling at EC F3J
2019. There should be no need for extreme joiners though this is again a
Circling camber can be extreme (5-8 degrees) while still maintaining speed
during because of a new tail design that keeps the energy better (less drag).
This means high bank angle is possible and yet still keep the high lift in a
The large and newly designed rudder makes it possible to yank the model into any
thermal you find.
As you will find described in the designer Philip Kolb’s writeup the penetration
in all camber settings is very good because of the new tail design. Now you can
change camber at any point without loosing flying energy like we see in many
airfoils. The model now just speeds up to the desired speed/camber setting and
keeps that for a trip over the whole airfield thru lift and sink. Night and
early morning testing have shown sink values as good as 0,35-0,4m/s in distance
mode (1mm up along the whole trailing edge and measured by altimeter). That
means search mode for thermals is very efficient and a fantastic glide ratio.
Flying in full camber in the same conditions gives values in the range of
0,25-0,3m/s but less area is covered.
Landing the Prestige 2PK is easier than ever. No aileron setup is needed
(aileron goes to neutral when brakes applied). Only flaps and elevator
compensation. Still the model slows down to a crawl and pushing over is easy as
the new elevator keeps the energy well even with full flaps applied. The rudder
is also better and bigger and with the new high dihedral middle and aerodynamic
airfoil changes it corresponds well to rudder input and is not as much affected
by sidewind as earlier models. Though it should be said that the lightest layup
has very light tips and heavier tips (inertia) might be preferred if the landing
area have lots of sidewind and/or turbulence.
The nose is removable. It is made longer than needed and can be shortened ( max.
100 mm) according to engine weight and lipo. Install equipment and shorten nose
to fit preferred CG. The original nose has a diameter of 32 mm. It is designed
to fit cheap and reliable outrunners for lighter versions. Very soon we will
produce a nose cone with slimmer diameter of 30 mm.
The servos and receiver are located in the fuselage under the center wing
therefore there is enough space in the front for the motor, controller and lipo.
Battery size from very small and up to 2300mah can be used as much care is taken
to a very thin but almost square fuse in the front area.
The complete wire harness is built into the center panel and the central
connector is ready installed. Wire harness for fuselage is also delivered ready
Servo compartments in wing are laminated on all sides with carbon fabric, so a
very strong box has been created in which the IDS system from servorahmen.de can
be mounted. We recommend to install IDS for KST X10 mini, JRDS 181 or 189, Mks
6130 for flaps and MKS 6110HV in the tips. For fuselage are suitable servos size
like MKS 6110 HV
In the future will also produce a V tail version
Although it is a new model a few pilots had it before WCH F5J 2019 and only had
the chance to test for a short time.
So in the biggest F5J competitions of all times the pre contest 4th WCH World
F5J Challenge only 3 pilots flew with the Prestige 2 PK. All 3 was pilots were
in Flyoff out of 190 pilots. Robert Bonafede won the 4th World Challenge and
finished 3rd at the World Championship that followed.
Other pilots with the Prestige 2PK achieved a lot of podium positions in a lot
of other F5J competitions.
* Attention. According to many pilots flying the Prestige 2PK it is very
We wish everyone who purchases Prestige 2PK many great experiences and sporting
SAMBA MODEL TEAM
Standard color scheme is the
back - Some words from designer Philip Kolb
After almost 10 years there is a new
2010 Philip Kolb set off with the fineworx team to develop and build a new F3J
plane with the latest available technology in aerodynamics, materials and
building techniques. Those days no efforts were spared to create and find new
ways of production, using the best materials available at that time. Due to
that, PRESTIGE was not commercially available. The approach to build that glider
did not reflect any reasonable economically based solution.
Nevertheless the PRESTIGE was probably the best allround thermal sailplane
during that period of time and could excel in an astonishing wide range of
wingloading. The glider performed marvellously from 1300gr to 5000gr flying
weight (A 5kg version could win the XC-soaring competition in Montague 2014,
although it was designed as an F3J plane).
Even nowadays, the almost 10 years old PRESTIGE would still perform as good as
any of the modern F3J ships.
Fortunately by now, all the “latest and greatest technologies” from 9 years back
(in-mould inflated fuselages, rohacell-core surfaces and wings, high modulus
spread carbon technology…) found their way into model airsports and are well
established and available for reasonable cost.
So why not taking PRESTIGE to the next level?
As F5J gained so much popularity over F3J out of various reasons during the last
couple of years,
instantly was meant to be designed for this new class.
Wing area 79,3dm2 - Elevator area 7,3dm2 - Total FAI
86,63dm2 ( apx 1040g F5J 2019)
Fundamentals of the
Since there is no towing in F5J, the structural
challenge is significantly less than in F3J and the design parameters quite
obviously are different. There is no need to design a light, stiff and strong
spar. This by itself lowers the structural weight of the glider. As well the
wings don’t need to be as thick as on an F3J glider out of the same reason –
there is no need for a very strong spar to take the occurring high g-loads. In
line with this, low flying weights and the resulting low Reynolds numbers call
for the use of very thin airfoils.
Nevertheless, an F5J glider due to the rule set can be exposed to flying
conditions from absolutely calm air to wind speeds up to 12m/s. For being
competitive even in high wind conditions there is a definite need to be able to
vary the wingloading of the glider no matter how sophisticated the aerodynamic
design of the glider is.
Therefore great care was taken to optimize the design of PRESTIGE-2PK to perform
over the whole range of possible flying conditions. Great emphasis was put on
the fact that PRESTIGE-2PK actually can handle a lot of ballast very well. To
achieve this goal the airfoils of the wing - even as they are very thin – need
to be able to provide a high maximum lift coefficient. To achieve this goal a
high (but not super high) aspect ratio wing showed best results, leaving
sufficiently wide chords to optimize the airfoils for both, the low speed (low
wingloading) case as well as the high speed (high wingloading) case. In the end
the Aspect ratio came out to be 19.2 at 3.9m wingspan. To reduce induced drag
with this fixed span the planform was optimized to be as elliptical as
reasonably possible. It thereby features a relatively high taper ratio (this
measure even helps to lower the weight and inertia in the outboard area of the
wing and thereby achieve better manoeuvrability), which in return was
counteracted by using a considerable amount of washout twist in the outboard
wing panel to achieve docile stall characteristics and a minimal turn radius for
Like with any modern modelglider-design the wing features optimized airfoils
along its span, taking the local Reynolds numbers into account. For the
PRESTIGE-2PK 7 different airfoils were developed and optimized along the span.
One criterion was to determine the optimal flap chord. On the one hand
substantial laminar flow which should not be tripped by the hingeline or the gap
between wing and flap should be achieved. On the other hand positive flap
deflections should result in minimal curvature change on the upper side of the
wing when cambering up the airfoil. The former calls for relatively narrow flap
chords and definitely has advantages when flying at higher speeds while the
latter shows advantages when putting more emphasis on very low flying speeds.
In the end 28% flapchord reflected a very wide optimum solution for
PRESTIGE-2PK. The wing-planform thereby was developed to maintain the 28% chord
depth of the flaps and ailerons all along the span.
To enhance performance, modern airfoils used at low Reynolds numbers (like on
almost all F3K, F3J and F5J aircraft) feature a so called “kink”, which means,
that the lower side and the upper side of the airfoil are not continuous and
smooth at the same time. This allows for a wider envelope of flap angles to be
used - especially positive flap angles to camber up the airfoil - because this
measure results in a less steep and abrupt pressure recovery on the aft upper
side of the airfoil.
Due to the unstable boundary layer conditions at low Reynolds numbers this steep
and abrupt pressure recovery on the aft part of the airfoils upper side can
cause significantly higher drag as a result of large laminar separation bubbles
and thereby a loss of performance especially when circling slow at steep bank
angles – which is mandatory in F5J!
For the PRESTIGE-2PK the kink in the airfoils is developed like follows:
The wing airfoils have no continuous smooth surface on bottom and top at the
same time. When the lower surface is clean, the wing is in a configuration
optimized for low lift coefficients, thus for fast flying (f.e. fast cruise when
heading towards a thermal through sink or under motor power when climbing at the
same time is not desired). After using 2 degrees of camber flap out of this
configuration, the upper side of the airfoils is continuous and smooth.
The configuration chosen by samba model to be
moulded is exactly in between the configurations for a smooth upper and lower
surface. So when adjusting the trailing edge to the inbuilt fitting close to the
fuselage intersection, the trailing edge flaps are like shown with the black
curve in the sketch below.
The inbuilt configuration to align all surfaces
when installing the aircraft can be used to setup all camber offsets for the
individual flight modes and as a separate flight mode as well. It reflects a
very efficient setting when cruising against not too strong headwinds (like f.e.
when turning back to the airfield from a downwind thermal). When there is a need
to push through sink, the “lower-side-clean-configuration” will be the better
As an F5J aircraft most likely will spend most of
its airborne time in circling flight, a great amount of work went into
optimizing the aircraft for these flight modes. In general - 2 camber presets
should be installed for covering almost all required airspeeds for different
thermalling conditions. As the airfoils are designed to perform well over a wide
range of angles of attack, setting the “right” camber (flap angle) is not
supercritical. Nevertheless it is recommended to use “elevator to camber mix” (snapflap)
to minimize drag over a wide envelope without the need of lots of different
camber presets and thereby minimizing the pilots’ workload.
The 2 thermal modes, which should be pre-installed are shown in the graphic
below. Nowadays they are usually named “Thermal-1” and “Thermal-2” because most
of the transmitters use these names as presets. “Thermal-1” mode is set to +3
degrees of additional camber measured from the factory inbuilt camber. It is
used in more active (turbulent) air when airspeed is crucial. “Thermal-2” mode
is set to +5 degrees of additional camber measured from the factory inbuilt
camber and is used when steep and tight circling is required to “core” a narrow
The tail configuration of the PRESTIGE-2PK is a
derivative of the original PRESTIGE. The sizing of the tails and the development
of the tail airfoils were undertaken by following aspects of docile handling and
reducing drag at the same time. Six non symmetrical airfoils were developed
along the halfspan of the horizontal tail plane and similar to the wings’
airfoils were optimized according to the local Reynolds numbers at each spanwise
position. The airfoils for the horizontal tail plane are in fact slightly
different from the ones used on the first PRESTIGE. Now that stabilizer and
elevator are built in solidcore-technology (on the PRESTIGE the stabilizer part
was still built in hollow moulded technique), the airfoils on the horizontal
tail plane could get thinner considering the very low Reynolds numbers and to
save weight on the rear part of the fuselage to keep the inertia as low as
To achieve very precise pitch control a hinged elevator was chosen, but as an
F5J-planes’ elevator is pulled up very often, a relatively wide elevator chord
was used. This kind of combines the positive aspects of an all moving horizontal
tailplane and a hinged elevator – low drag on the one hand side, precise control
on the other. As mentioned, the elevator of an F5J-plane sees major up
deflections while pulling tight thermal turns, therefore the airfoils for the
horizontal tailplane were especially designed to produce low drag for exactly
this configuration. The customer just needs to understand, that for this
elevator tailplane very precise high resolution servos and a slop free linkage
are mandatory to reach the actual precision this elevator can deliver.
Different from the horizontal tail plane, the vertical tail plane needs to
deliver substantial lift force to counteract and damp sideslip motions. The
sizing of the vertical tail plane as well as the sections therefore primarily
were chosen to achieve very good yaw damping. Thereby the symmetrical airfoils
of the vertical tailplane cannot be extremely thin in order to still provide
large maximum lift coefficients. The thickness of the seven vertical tailplane
airfoils thereby vary from 7% to 5.3%. They are very similar to the ones used on
the first PRESTIGE as there was not much room for further optimization.
All in all I really do hope that the new PRESTIGE-2PK will perform well in F5J
and make lots of F5J pilots happy with its performance and handling-qualities
and meet its design purposes to be a worthy successor of the PRESTIGE, as this
is still the nicest plane to fly I’ve ever flown.
Philip Kolb, May 2019
© Copyright 2019