I had always liked the look of the Václav Vojtíšek 'Sting' (http://www.hyperlink.cz/vvmodel/). Regrettably though, I saw my first Sting in the flesh after I had already committed funds to two entirely different moulded racing gliders and I never did get round to actually buying one. It did remain on my mental 'must have' list though and my desire was re-kindled when rumours of a 'New Sting' began to appear on the internet.
After a trawl for information I discovered that Roman Vojtech (http://www.lomcovak.cz) had been test piloting the New Sting for some two years. As the original Sting had only surfaced publicly as recently as the Portugal 2000 Viking Race, I was curious as to what was so different about this 'new' version. Roman was kind enough to send me a three view drawing and an explanation. This basically intimated that there is in effect no 'old' Sting, merely now three different models. The Sting, touted as a F3F specific machine especially suited to high wind conditions (reviewed by Mark Passingham in QFI No. 54). This version, the New Sting, larger and more of an all round model suitable for either F3F or F3B work, and then the Big Sting, a prototype model currently under test by Roman, aimed chiefly at F3B.
The New Sting itself is already proven on the International F3B Circuit. The Czech F3B team had utilised them to good effect at the 2001 World F3B Championships at Chrudim in the Czech Republic and the planform is said to launch extremely well. As the New Sting sits in the middle of the expanding VV Model 'Sting' range, it is fairly safe to assume that they too feel the New Sting is an intermediary for the two classes.
This entirely new model may be produced from its own set of moulds but outwardly the planform is almost identical to the original Sting. Were it not for the fact that it says 'New Sting' across the centre section, one could have trouble telling them apart unless they were sitting side by side. In this scenario it would become obvious that the New Sting is quite a bit bigger that the original at 3.00m span and some 1.46m length. Less obvious would be the different wing section, a modified HN354 which incidentally is the same as the NYX F3B reviewed here back in July '02, the increased centre panel dihedral, the wing mounting (now 3 x 3mm bolts), the revised tail mounting (2 x 3mm bolts) and the few areas of niggly work which have been pre done at the factory such as the Nicad installation hole, the pre fitted ball joints and the factory installed control horns.
Then, a chance happening. Soarhigh, the UK importer of all good things moulded, circulated a stock list with greatly reduced prices. On it was one only 'New Sting' (the UK's first). Full carbon wing, Red and White and considerably less than the original Ł600+ asking price. Kerr-ching! New Sting serial number 17 was in the post the very same day.
I've always had good service from Soarhigh and this time was no exception. The model arrived by courier, extremely well packaged with its own bubble wrap wing and tail covers and bucket loads of polystyrene chips for the bin men to play with. A small accessory pack contained servo covers, wing joiners (with one spare), clevices, control links, simple instructions, set up notes, some diagrams for servo installations, and the aforementioned 3-view drawing.
This was my first experience with a full carbon wing and the increases in rigidity over my existing glass moulded models was marked. The surface finish is like a mirror. No pin holing or blemishes anywhere on the model. The fuselage is really stiff and the heavy glass nose cone slips on with just the right amount of friction. The fuselage seams are the same as the original Sting and run along the sides instead of the more normal top and bottom. This simplifies construction and makes the tail and wing mountings very strong indeed. The rear fuselage appears to be predominantly Aramid although localised Carbon reinforcement can be seen at strategic points throughout. More noticeably around the pre-installed, adjustable tow hook.
The tail is a very solid, rigid fabrication and quite large. I can find no outward differences between it and the original Sting tail. It maintains the modified HN273 section and is dimensionally identical according to the drawing.
The HN 354 wing section (http://www.habebert.de/profile/hn354.pdf) is worthy of a more detailed examination. The true profile, with 7.88% thickness and 1.93% camber, is thinner than the original HN1038 wing and this one is stated as being a modified version which in applications of this kind usually means that it is thinned somewhat further still.
The overall accuracy of the model is very good. An audible 'pop' as the tip panel joiners are removed from their housing is testament to the fit of the parts. Perhaps a little too tight with cold winter fingers though. The fairing around the wing centre section does flow neatly to the fuselage, and in turn the rear end of the fuselage tails to a point with tidy access holes through the sides for attachment of the ball joints. The pre-installed pushrods for the ruddervators are from aluminium tubing which is quite common on these type of models. The inner nose moulding is from heavy glass too and separately bonded into place just fore of the access to the two cavernous ballast tubes. Each of these holds 11 Lead slugs for a total ballast capacity of a massive 60oz. This inner cone is of the 'boat hull' type and you must remove a portion to suit your choice of servos and receiver.
As is usual with high quality moulded models, finishing is more of a simple fitting out exercise. I always try to tackle the awkward jobs first to get them out of the way and so I undertook the make up of the wiring loom and the installation of the wing servos. Manufacture and installation of the wiring looms has been tackled for you by some moulded model manufacturers but VV model leave this to the builders discretion.
A recess is moulded into the underside of the wing in the centre panel to take one half of a commercial 9 pin D type connector. This fits very neatly when in place, the corresponding half being allowed to float free within the fuselage wing seat area. The fuselage wiring is a tight fit between the ballast tubes if you use normal extension leads as I did, but there is lots of room under and around the ruddervator servos to pass them to the receiver. Appropriate use of 'ribbon' cable would certainly improve the situation. I chose to use Volz Micro Maxx servos for flaps and Volz Wing Maxx XP servos for the Ailerons. Firstly though, a job for the dremel with the routing of the servo bay panels just inside the clearly marked lines.
The flap servos are a relatively simple installation. The flaps are bottom hinged and top driven. Linkage outlet shrouds are neatly moulded into the wing with the linkage running diagonally up through the wing to drive the brass horns. There is however no room for a large servo arm and the supplied linkages are basic. I considered not using them in favour of some proper ball links but in practice found that I really didn't have the room to spare. A simple 2mm metal clevice with lock nut is used at the flap end. The servo being glued or screwed into position dependant on its mountings.
The aileron servo installation is a much more complicated affair and proved to be the worst part of the installation. Again, all the linkage is internal to the wing, save for where it exits to drive the horn. The ailerons are top hinged and bottom driven. The geometry necessitates the fabrication of a mounting platform for the servo to raise it off the surface of the top wing skin with only a 7mm long arm pointing back towards the top skin of the wing. Very fiddly and quite time consuming.
In the review of the original Sting, Mark had come up against the same problem and chose to mount the Aileron servos in the same way as the Flaps utilising a bent linkage. I explored this but decided to keep the linkage straight and follow the instructions.
The platforms were eventually made and the servos were installed tight up against the underside wing skin. The Aileron throw with this short arm is more than adequate, but my flap throw was a little less than I desired. One could not help wondering if the pre-installed horns could have been set a little lower at the factory. In the event it was not proven to be cause for concern as you will soon read.
Onto the fuselage now and an area of the inner nose cone was removed to take two of the new Multiplex micro Digi Speed servos. Very fast at only 0.06 seconds/40ş on 6 volts. A standard Futaba 8 channel receiver, heavy duty switch, 6v 1100mah AA nicad and checker were installed with just 4oz of lead to position the cg at the recommended 100mm from the LE. The front end of the V tail pushrods were cut to length and a short 2mm rod glued into place with JB weld epoxy and then crimped for redundancy.
With the control throws, Flap/Aileron mixes, Camber, Reflex, Snap Flap and CROW set as recommended on the instruction sheet and all linkages adjusted for perfect centres (note - not sub-trimmed into place please!), the New Sting was ready for its first flight.
The very next day dawned warm, dry and sunny with 25mph North Westerlies blowing straight up a local slope not 15 minutes from my front door. How many times does that happen eh? I was on the slope by 9:00am with lift as good as it gets on this hill.
With the final checks made there was nothing left to do except commit aviation!
The model sat rock steady from the throw and quickly climbed out to 100 feet above the lip. Penetration was good but needed a beep or two of digital down to get the ship moving forward happily. A gentle left arc started to creep in and was easily corrected with an imperceptibly small rudder adjustment.
The model showed pace and covered ground easily without ballast. Flat flying comes first and some extensive wing wagging proved the differential to be wrong. My JR3810 is easy to programme in flight and I soon had it nearer the mark. The elevators felt a little sluggish for me at the suggested throw. I increased the rate substantially and kept doing so whilst looping tightly until it got silly. The circles were down to 30 feet diameter before the first signs of an incipient flick began to manifest themselves. It never became more than a wag though. No screwing out either, which rewarded the time I'd spent lateral balancing. The stall produced an easily recovered dropped wing and the spin was flat and predictable. It was quickly becoming apparent that this big model was very well behaved.
The roll rate was good at one per second. The Rudder control was more than adequate and surprisingly neutral for a V tail. I hooked a couple of slope thermals during this test flight and climbed away easily in both with proper co-ordinated flat turns. Experimenting with the camber served only to do as expected and slow the model down whilst minimising the sink rate to make the best of the warm bubbles. Conversely, 1mm of reflex got the model moving forward again without that 'sinky' feeling experienced with other wing sections. Soon I was around 500 feet high behind the hill and well positioned for a CG check dive. Pushing the nose down to about 60 degrees the model rapidly picked up speed. A very slight zoom commenced indicating a manageable forward CG. The noise increased with airspeed too but nothing more than any typical hollow mouldie. I held the nose down and as it passed us the model must have been knocking on for 100mph. Lots of energy for a series of big loops, Cubans and even some point rolls. The aileron response was crisp and stopping the bigger wing in exact positions made me look much better at this flying lark that I actually am. Inverted required a little down confirming the forward CG, and switching in the reflex helped here. I took the model up a little and positioned myself for a F3F run. With a short push the model again picked up speed quickly and entered my imaginary course. The turns proved tight with quite a good 'ping' to them. It held its line between the turns very well too, going only where it was pointed. A further run with the snap-flap inactive proved that the mix does indeed help to tighten the course, but I reduced the movements a little as I was beginning to lose some speed.
Landing now and the model initially pitched down under CROW with excessive elevator compensation, but the roll response remained good enough to pick up any errant wing. The model slows very rapidly and even with the seemingly low throws, the flaps are very effective. I tried a couple of approaches to get the line right before committing myself to finals and the very small landing zone.
Hitting the Crow out of the back turn and holding the nose high had the model parachuting down with the wings remaining level. Tucking the vulnerable bits in before it hit the floor produced a minimal forward slide.
Over this day and the next few outings, the New Sting was campaigned in many varying lift conditions on many different slopes. Low hills, high mountains, turbulence in the compression layer, scratchy thermally days, ballistic 45mph days, big landing zones, small landing zones, steep 'lipped' slopes and gently rolling 'big wing' hills. Every time I learnt something new about the model. Especially that better height gain can be achieved by leaving the camber mix well alone until you are actually in lift good enough for it to be of use. That just half ballast transforms this ever quicker machine yet again, shifting the energy retention from very good to exemplary. That when ballasted, wider turns are rewarded with better energy on the out, although it will still ping extremely tightly if required to do, and that no matter what I tried to do to upset her she remained 'grippy' throughout and held her track better than any other glider I own.
With almost 15 hours on her at the time of writing, the New Sting has been flown almost every weekend for the last three months and she has not had an easy ride. There is still no sign though of the abuse she has taken at my hands. The spar lines remain invisible on the wing skins and aside from a few chin scratches she's as pretty as the day she first flew. The fits are a little easier now as you would expect and I feel that the set up is pretty much optimised, for me at least. I would have very much liked to have raced the New Sting in competitive F3F before concluding the review, but the weather gods have deemed it not to be so. I will however be campaigning her when the F3F winter league gets underway. Though as an insight as to what could be in store, at the time of my test flights and initial jottings for the review, the New Sting was being campaigned by members of the Czech teams at the controversial 2002 Viking Race in Donovaly, Slovakia. The Czech 2nd team took top honours and New Stings placed 2nd, 4th, 8th and 9th overall. Václav Vojtíšek himself took the 2nd spot with his own modified New Sting (experimental tip panels) and Roman Vojtech campaigned the prototypical Big Sting to a commendable 12th place. Proof indeed that the New Sting comes from a highly pedigreed stable.
The New Sting is available from Soarhigh in the UK. Contact Gary Taylor on 01343 820542, or 07919 248181 after 5pm. Alternatively e-mail Gary on gary@solo27.fsnet.co.uk Expect to pay around Ł625 for one.
Andy Ellison