PRESTIGE 2PK F5J FAI Light, V-Tail, Carbon/White
F5J FAI version , RTF weight 1040g-1140g (36.5-40oz), stiffness spar – 12%
This may be the lightest 2PK do to the lack of paint.
- Includes Protective Cover
Does not include IDS parts or ballast
We do not recommend putting any significant amount of ballast in FAI light versions. Max 3-4 oz.
From Flight Comp-
The Prestige 2PK is truly a step up in design and performance from Samba. It is on par or better than current F5J designs. We have extensive flight time on this model and were the first to test it in the USA. Most impressive is the slow speed turning ( thermalling ) performance. It gives you extreme confidence down low when turning in lift.
Penetration is good and it signals lift exceptionally well. The Rudder is very effective. The model is very stable and easy to fly even when drastic changes to the CG are made. The massive flaps are very good and it can be slowed down to a crawl in the landing circle.
Camber settings recommended from Samba are very good and work well. CG setting around 108 makes for a very very stable model. 112 seems to be good all around and 116 makes the model extremely responsive but a bit more of a handful to fly. Adjust the CG to your style of flying. Adjust the throws and mix's to suit your style of flying. However we do recommend sticking with Samba's camber recommendations.
Scroll all the way down for build videos and flight testing
Our throws/settings to date-
Ailerons +- 16mm, no differential
Flap/Ailerons Mix +- 7mm, no differential
Aileron/Rudder Mix 50%
Rudder Travel 40mm each way
Elevator Travel 20mm up, down 2mm from hitting boom.
CG- 108-112mm from LE
Camber settings-see Samba's settings
Samba's Recommended Camber settings-
Elevator measured from trailing edge to boom
|ail-flap mix up/down
Thermal 2 and 3 for circling
|measured from boom
Elevator measured from trailing edge to boom
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 PRESTIGE 2PK.
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 personal preference.
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 tight thermal. 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 made.
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.
Some words from designer Philip Kolb-
After almost 10 years there is a new . In 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 wing loading. 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.
Fundamentals of the design:
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 thermalling.
Like with any modern model glider-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% flap chord 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 choice though.
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 thermal.
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 half span 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 possible.
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
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