Multiplex Merlin

Multiplex Merlin

 

 

Some time ago Multiplex released a cute little chuck glider called Fox. At under a tenner it was a fab toy, and a cracking candidate for a two channel radio conversion, the result being a very neat little sloper as many old slope hacks found out.

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Anyway, I'm sure Multiplex felt they missed the boat on that one, and probably vowed not to get caught again, so here we are with their latest cool tool, the Merlin. With design cues from it's Foxy progenitor, and more than a passing resemblance to the Easy Glider, all sweeping lines and upturned tips it is, tres cool non?

Upon opening the box, which is also a tote-tastic Elapor carry case, it' all business. Teutonic engineering excellence in fact. Exquisitely moulded components, concise multi-language instructions with a series of superb illustrations detailing each step in a crystal clear fashion. For a laugh I think I might build it in French….

However, do you ever get that feeling of foreboding when building a new 'un?

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A tiny pair of wings, and a significant pile of plastic, wires, tubes, rods, etc. My thoughts were telling me 'over-engineered' and 'heavy'. Don't get me wrong, some of the constructional elements are absolute genius, but I simply questioned whether they were really necessary on a sub-metre span model, particularly with it's leanings towards being a glider, and the need for a light airframe.

MAGIC TOGETHER

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The build itself starts with the fuselage, preparing the elevator and rudder servos for their ultimate locations, then adding a selection of stiffeners in the form of 1.5mm glass fibre rod. These are cyanoed in place, but take care. The foam doesn't really absorb the glue and a little goes a long way as I found – generally speaking, all over my fingers – sticking me to the airframe, then my fingers to the bench , and then the whole ensemble to my jeans whilst trying to wipe it all off!!! Ahem! Not a good start for a pristine review model huh…?

Luckily wiping the cyano off doesn't seem to leave a crust on the foam. Bonus! So, suitably chastened I continued. With the wing retaining plate added and the fuselage halves joined, much like an Airfix kit, the next step is to add the motor mount which also forms the nose of the aircraft. I was a little concerned at gluing this in place, so used double sided tape instead – much easier to remove if the need should ever arise.

The Multiplex 'tuning set' was supplied with the model for review, and gives a soup-to-nuts solution if you don't already have a suitable motor and ESC to hand. Two sizes of folding propeller blade (7×4 or 8×5), come with the set, allowing the user to tune the performance for duration or power. In the event I threw the biggest blades on for max performance, although this obviously affects current draw and duration at 7.5A. The ESC is the Multiplex Multicont BL20 S-BEC, and is supplied pre-wired to suit their own 450mAh 3S Li-Po. With the Himax C2212-1180 you're good for 8.5amps max draw for 15 seconds, a bit near the knuckle for my liking with the larger blades, but we'll see how we get on. A very simple fit and forget solution nevertheless. The only snag during installation appears to be the proximity of the motor wires to the rotating can of the motor. There's very little clearance in that tiny fuselage. In the event, I removed a little extra foam and taped them in place with a few strips of Blenderm to keep them out of harms way.

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Attention quickly turns to the wing and tail plane halves. Some serious thought has been given to all aspects of this, but I can't help but think it a bit overkill. A system of interlocking spar box and clasp mate the wings to the retaining plate in the fuselage. Spars are carbon blades, glued with cyano into closely mating channels in the wings. Utter genius, but sheer engineering indulgence! Why not a small carbon rod joiner and a friction fit through the fuselage, a la Easy Star?
Regardless, it works, and I amused myself attaching and detaching the wings during a coffee break! Should the plastic clasps fracture however, then you'll be stuck… 

Multiplex Nano S servos are a perfect fit in the designated aileron servo spaces, with wires running back to the fuselage via moulded channels. I've never used Multiplex micro's before, and note that the servo leads are usefully long and no extensions leads are necessary, although the resultant pile of electrical spaghetti in the fuselage requires a little planning to create a tidy installation, i.e. stuff it all down the tail boom…
A fairly typical problem in tiny airframes such as this.

Tailplane halves continue in much the same vein, mating with an ABS joiner/clasp. All very clever!
The tail plane joiner keys into a bellcrank, which rotates in a plastic housing, mounted in the fin. It's slop free but limits the total amount of elevator travel quite markedly. Very nicely made though!

So, I'm about two hours and three cups of tea into the build, and she's not far from being finished. All that remains is to add the rudder pushrod outer and hook up the control runs to complete the airframe. A nice sheet of stickers is supplied, one of which covers the elevator servo. The instructions detail using some of the sticker backing material to form a hatch. A bit of an afterthought after this thermoplastic engineering masterclass!

With the decals applied she's very pretty but the canopy really does need a lick of paint to complete the effect. My first attempt with marker pen wasn't too durable, but a rethink with a little Acrylic paint and a flick of the airbrush made a much better job.

I dug out an old Jeti Rex 5 receiver and hooked up all the controls, setting throws as per the very detailed instructions. The receiver found a home in the tail boom, leaving acres of space for the Li-Po and ESC, a bit of a luxury given the diminutive size of the model, but affording a useful way of tuning the C of G later.

So we've moved from box to flying in double quick time, now it's time to find out if my concerns about the models weight will be borne out.

ABRACADABRA
But first I had to charge the Li-Po. In their infinite wisdom Multiplex have quite cleverly used one of their green six-pin servo plugs for mating battery to ESC. The only problem is you need a further female half of the plug and socket to make a charge lead. After scratching around the workshop I brutally hacked one out of an old glider wing. Half an hour later the electrons were flowing quite nicely twixt charger and batt.

I don't generally enjoy flying new toys in front of all my club mates, but presented with an unusually calm and warm September afternoon I had no excuses. In the event there was no drama. A quick check of the controls, and a cursory spin-up of the motor confirmed that all was well, so the model was unceremoniously lobbed into gainful employment! And away she went, purring like a kitten. Well, homesick angel would be more apt. How such a tiny brushless outrunner can yank a model heavenwards so deftly I have no idea. I'm loving it though!

Controls were smooth with plenty of bite, and the model gave a pleasing whistle in a dive, just like a big moulded ship in fact. She was zooming with speed on the glide, so a swift landing and a jiggle of the battery rearwards was called for. After two or three bites at the cherry, the C of G was sorted, with much less trim change from power on, to gliding. The only bug-bear with the whole flying thing has been the curse of all foamies, a dirty bottom after a few flights from a grass patch. A scrub with a little kitchen cleaner and then a bit of cross weave tape cured that!

With the 450mAh Multiplex Li-Po freshly charged, the climb performance is in the 'continuous vertical' category for the first few 'moonshots'. The power then levels off a little, giving several minutes of useful motor run for a mixture of aerobatics, gliding and thermal hunting, touch and goes off the grass, beer can skittles, washing line limbo or any other silliness you can dream up.  

WIZARD?
Trouble is, I can't really pigeon hole this cute little toy, so it goes everywhere with me like an obedient pet! The craziest thing is that I needed to program spoilers to get it down. To land, I simply line her up, then thumb the spoilers (ailerons) out. No elevator trim appears to be necessary. A giant invisible hand just reaches up and grabs her.

If I'm honest, she's not the sort of model that would ordinarily entice me to splash the cash, but having flown her time and again I've got to concede that there's room for her in my heart. In fact, she's been sat on the back seat of my car all week, for a 'just in case' flying opportunity. She's that sort of toy. Completely unpretentious. Watch out, you may find yourself exiting the local model shop with a kit unwittingly tucked under your arm…you have been warned!

DATAFILE
Name: Merlin
Model type: Mini hotliner,
Street price: £53
Wingspan: 31”
Length: 24”
Wing area: 175 sq. in.
Functions (servos): Ailerons (2), elevator (1), rudder (1)
Power system: 50-100 watt outrunner, 10-18 amp ESC, 8×5 folding prop
Battery req’d: 3S 450mAh Li-Po

 

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