Graupner is one of the biggest names in the world of R/C aircraft and when they bring a trainer to the marketplace it has to be worth a look. Being a club instructor gives me the opportunity to fly plenty of different trainers so I was interested to see what the curiously named Taxi Cup II had to offer.
In truth the Taxi Cup is a Graupner classic not often seen flying in the UK, and it has a whole family of brothers and sisters from a tiny electric version to a huge 26cc petrol glider tug.
This is the mid-range 0.40 size trainer, although my first sight of the model was courtesy of the Tower Hobbies website video where the ‘Cup is shown flying knife-edge quite happily up the strip. This somewhat confused me as to the models identity. Just what is the Taxi Cup II, a trainer or an aerobat?Article continues below…
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One of the largest Graupner suppliers in the UK is Motors and Rotors, who also distribute the Super Tigre engine range, so it was no surprise that my Taxi Cup arrived with Super Tigre GS40 motor, a Graupner 12 x 5 prop and a silicon exhaust deflector. Incidentally, these items are sold by Motors and Rotors as a package deal.
The instructions come in the form of two books and at first I went for the one with the pictures. After browsing the pictures for several minutes I realised the text was in German. The other book contains the translated English text but without pictures, this was a little disappointing especially when you consider that the model is aimed at beginners who may find this dual instruction arrangement confusing.
The English text made sense to me, but the technical level was a bit much for my 12 year old son. I just don’t understand why Graupner choose this method especially as the kit will sell in large English speaking markets, not least the U.S. Anyhow, gripe aside the quality of the parts in the box did look very good and the pieces were neatly wrapped in individual polythene bags.Article continues below…
WING AND FEATHERS
The build started in the normal way by joining the wings with a hefty wooden brace and one-hour epoxy. The mating of the parts was perfect and just required a simple aileron servo installation, easily achieved by adding a liteply plate over the waiting hole in the wing.
The instructions suggested using a cool-ish soldering iron to cut away the film around the hole and, indeed, this turned out to be a great way of removing the excess film as the heat from the iron sealed the edges at the same time. The holes for the four big wing bolts were cleared in the same way though it does leave ugly wounds requiring a lick of paint on the inside to tidy them up. With this, a wing servo was duly installed, although I had to remove some material from the hole in order to get the servo to fit correctly and leave enough room for the cable exit. Since the ailerons themselves were already glued and pinned, the wing was completed very quickly.
Youll be pleased to note that the general fit of the wing with the fuselage was good, although I did remove a couple of millimetres from the windshield which clashes with the leading edge. Other than that the alignment was perfect and required no ‘fettling’ to square it up.Article continues below…
To the back end now where, after removing the film from the mounting slots at the rear of the fuselage, I glued in the tailplane and likewise the fin. Once again the control surfaces were already pinned and glued, straight from the box.
Whilst the Taxi Cup is supplied with the engine mount installed, you will still need to gauge the distance of the prop driver from the firewall so that the propeller doesnt clash with the cowl. Fortunately, the instructions help here with a few useful measurements and dimensions. Having assembled the Super Tigre 40 with carb and silencer, I decided to fit the cowl at this time and duly cut the hole for the cylinder head, needle valve and silencer. Unfortunately, however, aligning the painted strips on the side of the cowl with those on the fuselage resulted in an unsightly gap at the top of the cowl. What a shame to have to spoil the lines of such a good looking model just to match up a paint stripe! In the end I chose to close the gap aligning the stripes on one side only hoping that the cooling holes for the cylinder head would draw the eye away from the mismatch.
Continuing with the aesthetic improvements, it was time to fit the spatted undercarriage. I’m not so sure that spats on a trainer are a good idea, but you can always leave them off if youre still bouncing those landings. Mind you, they do enhance the appearance of the model and are pretty robust and well finished. Two individual aluminum undercarriage legs are bolted to the fuselage and the spats aligned with the ground before final tightening.Article continues below…
At the back end its not uncommon to find a tail wheel thats been supplied as an afterthought by the manufacturer. However, as Im sure you know, the word ‘overlooked’ is not to be found in the German vocabulary, so youll find a very tidy and fairly robust tail wheel unit included with the kit.
PUSH ‘N’ PULL
The tail control surfaces are driven by steel pushrods mounted inside aluminium covered plastic tubes. To say they were stiff in operation was a bit of an understatement, the suspected cause being burrs on the ends of the metal outer tubes. Filing these back helped a little but the movement was still far from silky smooth, so I lubricated the rods with silicon spray which, as luck would have it, vastly improved matters.
The elevator is split either side of the huge rudder and so requires two pushrods. Mounting the rudder horn first, followed by the two elevator dittos, I noticed a clash of horns when the snakes were run to their ‘natural’ positions. As a result I ended up cutting down the one for the rudder so that it cleared, this in preference to bending the outer ends of the snakes. Its still rather congested back there though.
Mounting the three servos inside the fuselage should have been routine but the gaps in the tray were too small and needed enlarging. Having got them installed youll note that the rudder pushrod is connected via a right angle bend and swing keeper whilst the elevator pushrods are unified via a three-hole bar, the respective rods being secured with grub screws. Incidentally, the grub screws are not very deeply threaded and, as a result, two of these stripped before tightening securely. Oh dear. After drilling deeper pushrod holes, opening out the threads and inserting a helicoil insert (a bit like a spring that fills the hole) I eventually got the parts together.
All this messing about was making me feel like a novice myself so in an effort to restore esteem I managed to fit the throttle linkage without problems and re-tightened all the engine mount bolts. In fitting the prop and spinner to the motor I promptly split the whole prop driver assembly!
I know what you’re thinking, but it really did break with very little encouragement from me and my tiny 3″ electrical spanner! On close examination I found the cast aluminium prop driver appeared to be dull and speckled suggesting an occluded casting. Dave Wilshere at Motors and Rotors had a good chuckle and sent me a new one soon enough.
The fuel tank is 12oz in capacity giving plenty of flying time. This tank was mounted directly behind the front bulkhead and positioned with a piece of piano wire pushrod threaded through the lug at the rear of the tank.
The receiver battery is mounted beneath the tank and wrapped in foam with the receiver itself located under the windows. I added a switch to the side of the fuselage instead of the method stated in the instructions which suggests mounting the switch on the servo tray internally and operating it with a piece of piano wire through the fuselage side. The aerial lead was passed out of the fuselage just behind the wing and rubber banded to the fin. Finally, she was finished off with the excellent decals supplied in the kit and one of those lovely Super Tigre stickers that come with the engines.
That takes care of the the build take a look at Part Two for my flight report.