In a bid to
find something a little more exciting to fly, hopefully be highly manoeuvrable, attractive, and
even more importantly, durable, Mike Pirie and myself independently came to the conclusion that
the Multiplex Twin-Jet might provide the answer.
We both acquired the newest version of the kit, which comes with a pair of speed 480's instead of the earlier 400's, and moulded from a radically different type of foam. Arguably, for the £69.99 price tag, it seems reasonably good value for money, but when you open the box there ain't a lot of bits in there &&&. only 6 moulded components, a length of balsa, plastic battery well, bag of bits and a sheet of stickers. However, the motors came complete with Gunther props and power cables.
In an attempt to convince the wife that I hadn't been "done", I laid everything out, added the servos, speed controller, battery pack, and even threw in the soldering iron before inviting her to "view" my latest project. "All this for under £70?" &&.. I think she was impressed, but suggested I contact my doctor on account of looking so flushed!
This new foam is great stuff, it's cyano friendly! The instructions point out that neither white glue nor epoxy work on this material, so we both used Zap-a-Gap...instant bonding! If you had all the electronics to hand, it would be possible to build the TJ, apply the stickers and have it flying the same day. Fantastic! We of course opted for the OTT route.
At Mike's suggestion both sets of motors were run-in underwater, and he went one stage further, by fitting one speed controller on each motor so that differential thrust could be applied using the rudder control on his Tx. A model with such jet like appearance deserved a fancy paint job, so the stickers were discarded, and both planes finished in a full size colour scheme. Once again, the foam surface proved very tolerant with a variety of paints.
Most definitely the easiest and quickest construction job I've come across, but a minor couple of niggles are worth mentioning. After sanding off all the dimples and mould lines in preparation for painting, I found the recommended elevon hinging tape wouldn't stick worth a bugger! Fortunately the paint bonded well and the tape sticks fine to that. The moulded in battery ramp/support was a little on the short side, requiring a 1.5 in. extension &. no big deal! Another head scratcher involved the motor thrust lines. The instructions state that the 480's are simply glued in flush with the rear edge of the cowl, but there was a moulded lip half way back, which coincided with the length of the shorter 400 motor, so we figured that dropping the 480's straight in would result in the thrust line being way out of whack. These were sanded off prior to fitting the motors.
Now the fun bit! I initially had glitching problems (resulting in repairs), traced to a faulty on-board electronic mixer, essential for elevon control with non-computerised Tx's. A replacement mixer, a splash of Zap, a lick of paint and all was well!
Neither of us had used the supplied Gunther props, fitting Irvine 5 x 5's instead. These carbon props were much more rigid and by all accounts much less noisy in operation, but may have led to the initial difficulties with hand launching the TJ. Using the launch technique recommended in the manual, both models tended to wallow around for a few seconds until the props unstalled themselves. We've now got this sorted out, and speed builds up quickly for a very impressive climb out. Another surprise was the amount of down trim required to achieve level flight at any throttle setting-in my case 9 clicks difference from the launch setting-rumours are that Multiplex haven't got the trailing edge reflex quite right?
Sounds a bit of a handful during the first 10 seconds of the flight, but in reality it is very easy to cope with, and once up to speed, she's a pussy cat to fly. The Twin-Jet is so agile that it encourages you to throw it about. On full rates we reckon on 3 x 360 degree rolls per second, loops from level flight, but does require a fair dollop of down elevator for the inverted stuff. Being a sensible sort of chap, I reduced the aileron throws so that they were more in tune with my reaction times. Power off for landing (still using the flying trim settings) proved drama free, with approach and flair out perfectly controllable for a gentle touch down. Not surprising really, with a flying weight of 42 ozs (mine was a little heavier &.. typical Robertson paint job!) giving a wing loading of around 14 oz/sq.in. It's no floater, but doesn't qualify for the "brick" category either!
Our attempts to fly in formation were a barrel of laughs & no danger of a collision! By and large we couldn't get close enough to each other, except for a (lucky) couple of side by side low passes followed by a presentable synchronised 360 deg. roll. I can honestly say that this was the best fun I'd had with another consenting adult without being arrested for it!
Mike's one ESC per motor is showing some potential. Stall turns without a rudder are tricky, but by shutting down the inboard motor and giving the outer full throttle, the tail flicks over nicely. Another interesting possibility using the same principal, but as of yet untried, would be knife-edge passes &&.. dare you Mike!
If you decide to go for one of these little crackers, you won't be disappointed. Pure fun from a lump of attractively formed foam, with typical flight times of around 10 minutes from an 8 cell 2400 mAh Nicad pack, significantly longer if Nimh's are used, and as easy to fly as any trainer on reduced rates. Yup, I'm well impressed!