Phil Chisholm tells us about his Weston UK MagnumR

By now, most will have heard of the aero-modelling phenomenon that is "The Magnum". It has become iconic in the field of extreme speed prop models. Weston UK have been distributing the ARTF version for a few years and have now standardised on the rather excellent West Eurotech .50 V1 which delivers not much short of 3hp at just over 21,000 rpm, but more on that later. An 8 x 10 prop sees this model reach speeds which are claimed to be in excess of 200mph, combined with very stable and predictable handling, it's no wonder that this rocket ship has been so popular with aero-modellers looking for something with such scorching performance.
		Specifications: Wingspan: 875mm Length: 1070mm Weight: 1.75kg

One hopes that with anything this popular, designers will continue to seek improvements and develop their creations in order to maintain their market, and the Magnum designers are no exception. Despite being the darling of the speed freaks, the Magnum hasn't been without it's niggles albeit quite minor ones, and one had always hoped that one day they would be addressed. In this case, it would appear that common sense has prevailed with a number of changes being implemented for the Magnum 'R', but how significant are they? In some instances this is a tricky article to write since it would be unfair to do the "Magnum 'R'" any justice without having flown it's predecessor, "The Magnum". I'm fortunate enough to have owned, albeit briefly, the former and got a few good flights out of it. If you read any of the on-line forums there tends to be a common theme amongst extreme speed prop enthusiasts, that being the sudden and catastrophic "arrivals" of their fast models more so than your average high-wing fun-fly. Indeed I managed to stuff my original Magnum, simply because it got very small very quickly and efforts to fly back into an area where I had a good sense of the models orientation were met with the inevitable. However, I was lucky in that the West Eurotech .50 V1 and tuned pipe survived their rapid meeting with terra-firma completely unscathed. To fly the Magnum as intended is essentially to fly a model without an undercarriage (although it is possible to fit one), and so dead stick landings are the order of the day unless you don't mind snapping a prop on every flight. Combine this with a really slippery wing design which does not develop huge amounts of drag-inducing lift, and you can appreciate that a particular landing technique needs to be adopted in order to bring the model back home in one piece. With a bit of speed in reserve, glide it back to the patch from an altitude higher than you'd perform an approach with any other model, and retain a flat or slightly nose down attitude and observe the rate of decent, flair and almost plop the model onto the deck with the tail just touching down as it approaches stall speed. It's a technique which takes a bit of getting used to but it isn't too difficult and so long as you have plenty of room you shouldn't go too far wrong. The original Magnum didn't really glide too well and there are plenty of people that have been critical, perhaps loosing sight of the intended purpose of this model and the inevitable short-coming of it's inherent wing design for anything but high speed. You can't really have your cake and eat it. On the original ARTF model, the wing retention mechanism had been a focus of critics, since it's an OK fit and is held in place with a couple of M4 screws and nuts into a former constructed of 3mm ply. If you catch the wing on a heavy, or less than flat landing then the former has a tenancy to break. Personally, I've never seen this as a huge problem, even though I've broken the former myself. At least the break is predictable, clean and easy to repair and helps prevent major wing damage. One of the things which catches your eye with the Magnum is the tail section with the very distinctive anhedral design. During construction of the original it becomes obvious that the slots cut for the tail halves are not cut for an anhedral installation and so pressure is brought to bare on the fuselage as the tail halves are almost wedged in place, much to Chinman's displeasure as one flight ended with the stabiliser separating itself from the fuselage on landing as the fuselage split. A bit of cyno and rocket powder sees a very effective and easy repair, but again it's another niggle that this excellent model really doesn't need. So, what about the Magnum 'R'? Are there any noticeable changes and is it any better? Well someone has been paying attention and listening to their customers, taking notes and have sounded the death knell for the Magnum. No longer is the Magnum that we've come to know and love available - it is no more.

OK, well maybe the Magnum isn't dead, but my one certainly is - may it rest in pieces - with no one to blame but myself. The perfect excuse to replace it with a brand new "Magnum R". A quick call to the nice guys at Weston UK and, behold, a new Magnum R is delivered the very next day. One of the things you notice on the outside of the box is a round badge which states "Premium Quality ARTF". A bold statement indeed as ARTF models have been the source of much discussion for a while in respect of model safety and just how well they are assembled. It has to be said, the quality is very evident in this kit. It's quite hard to make direct comparisons to the old model as some of the changes are pretty major. The outside of the model might look very familiar to the casual observer, but that is where the similarity stops. It is obvious that this isn't just a re-release of a model with a few tweaks, it is a complete redesign from the ground up. Thicker ply is utilised throughout but the completely redesigned fuselage with plenty of lightening holes makes for a lighter and stronger fuselage. The quality of the covering has also improved, and instead of the plain yellow covering of the old model there is a new metallic yellow covering, the quality of which becomes evident when you try to remove it from areas that require gluing. The de-rigueur carbon-fibre look-a-like decals are still there but now the canopy has also been finished with the same effect. The underside of the wing has also been decorated with a similar shape set of decals but with a chequer-board design to make orientation a little more obvious. One immediately obvious change in the design is in the shape of the wing. The design of the original Magnum wing was very flat with very little profile evident on the leading edge. This made the final glide to the patch more of a nose-down, un-powered flight/dash. The new wing still has a very slippery shape but now has a wing design which will at least encourage some lift. This should make the glide a little longer, we'll have to see. The wing retention system has been completely redesigned, with a single large plastic screw placed through the back of the wing and into a retained nut in the fuselage which has already been installed at the factory. The installation of the wing servo, ailerons and connecting rods are exactly the same of the original - a ply plate is secured with cynoacrylate around the hole allocated for the aileron servo which actuates two torque rods located near the trailing edge and are secured into each aileron with a small amount of epoxy. All aileron hinge tabs are secured by wicking thin cyno into them whilst in place. Nothing new in that. The tail with the familiar and distinctive anhedral design is now swept with the tail halves placed into pre-cut slots with the correct angle. This makes installation extremely fast and simple, with elevator hinges installed using the same method as for the ailerons. The tail fin simply stands in a pre-cut slot and secured with epoxy once the covering has been removed on the glued surfaces (same with the tail halves) which brings me back to quality of the covering. It's very strong and has some very elastic qualities which means it won't tear easily - the up shot of this is that you need a very, very, sharp blade and still need to apply a bit of pressure whilst taking great care to not cut into the balsa underneath. Once I'd marked the areas to be removed I peeled back the covering beyond where the cut needed to be made, taking great care not to stretch and distort the material, and cut it dead straight with scissors, after which I tacked it back in place with a small drop of cyno. The fuel tank is slightly larger than the earlier version and a small modification to the bulkhead former needs to be made to ensure that the fuel tank can be positioned as far forward as possible, otherwise it makes wing installation practically impossible - this is the only niggle in the entire installation process. Care needs to be taken when installing the fuel tank as it is very easy to introduce a pinch into the fuel tubing which will halt all efforts to bring the engine to life. The throttle servo is simply screwed directly into the mounting plate already installed in the fuselage and the engine mount is already installed, as is the tube for the throttle wire. This means that aside from bolting everything in place, threading the throttle wire through it's tube and attaching the appropriate linkages, there is nothing more regarding engine installation other than installing the tuned pipe as supplied with the West Eurotech .50V1 package. This leaves only the elevator servo and it's respective linkages and the flight battery installation. The elevator servo is first screwed to a ply-plate which is in turn installed into the fuselage, just behind the wing. It has it's own access hatch which is keyed at one end and I've secured it at the other with a screw and piece of colour coordinated tape. The elevator linkage is also unchanged from the original which connects to the servo and splits into two "snakes" with each exiting just under the tail halves. Once elevator control horns have been installed it is merely a case of connecting it all up. All in all, this is an incredibly fast installation and the hardware kit as supplied is very complete and of good quality metal components where it's needed. It's entirely possible to start assembly in the morning and go fly in the afternoon, but I would advise against rushing at it. Even if you took your time you could do it within one day or over the course of two or three evenings. As far as radio gear is concerned, I've decided to go for a PCM solution using the JR770S 7 channel receiver and three JR811 digital servos which are rated at 6Kg. That ought to be enough for these very small control surfaces. Receiver Installation is simply a matter of connecting everything up, wrapping the receiver in foam and wedging the whole thing, neatly, under the servo mounting plate in the fuselage. The aerial threads into a pre-installed plastic tube which exits neatly out of the tail. Linkages and radio need to be set in order to provide the manuals recommended 10mm travel for the elevator and 8mm for the aileron. I've also programmed my Graupner/JR MX-22 for about 50% exponential on both control surfaces which I imagined would allow very small precise changes around the centre of the stick without things getting too hectic. A 5 cell 1500mAh flight pack should provide plenty of oomph to the control surfaces and have some good duration whilst allowing for the slightly power-thirsty digital servos.

For the first flight I opted for the 9x7 APC prop out of the selection that I'd ordered with the model. The 8x10 is the "bad boy" and so I figured it would best to leave it at home, at least for now. The prop needs to be installed so that it is vertical at the start of the compression stroke. That way, once the motor has stopped, the wind force will keep the prop pressed in that position and keep it out of the way on touch-down. The West Eurotech 50 V1 is a fantastic piece of kit. It's a very reliable starter and setting it to run on the ground is a doddle. Since I figured that this fast model would mean there is a tenancy to lean-out the engine during a high-speed dive I decided to leave the engine with a setting a little on the rich side. Running the engine on the ground with a "spot on" lean-ish setting could easily make it run too lean in flight which could lead to engine damage. Once I'd found the ideal setting on the ground I then turned the mixture setting out (rich) a couple of clicks. Once the engine is setup then a quick test of the PCM safety settings (throttle back and hold) sees us ready for launch (you can't really call it a "take-off"). The St Albans Model Aero Club was the venue for the maiden flight, which is perhaps the oldest Aero RC club in the country. A very enthusiast group of guys they are too, although anyone would be nervous when being asked to chuck an animal like this. John Serlin kindly volunteered his services to that end. The safest way I've found to hand-launch any Magnum is definitely with two hands, one placed firmly around the fuselage just around the front of the wing, with the other hand supporting the tail and a finger placed across the flat section at the back where the aerial exists. Rather than chucking the model, pushing the model away on the tail seems to be quite effective, and at full throttle the Magnum 'R' gets into it's stride very quickly. In fact it's gets into it's stride so quickly, you really need to be climbing steeply in order to prevent it getting away from you too quickly. One thing that you notice very quickly is the effect that different model speeds have on its handling. At high speed the aileron gets very sensitive and it will perform incredibly fast and axial rolls. I'd left the ailerons with 100% travel and 50% exponential, but for me I think that even this is a little too agile for the first flights. Conversely, the faster you go the less effective the elevator, so don't get too aggressive with the dive angle or you find that you simply run out of elevator and it will all end in tears - leave plenty of height for loops until you're utterly familiar with the characteristics of the elevator at different speeds. The same goes for using the elevator in a turn - the turning radius will increase dramatically with speed so take care with the last turn before the return leg of your circuit or the model will end up behind the flightline. The way I tend to turn this model involves climbing at around 30-35 degrees and then execute the turn into a dive in the opposite direction. The initial climb helps to scrub off any excess speed which makes the elevator that bit more effective. Another way is to simply come all the way over the top and perform a half-roll once heading on it's new course. Once you've got the model pointing in the intended direction it tracks straight and true and flies on the proverbial rails. The first circuit ended with myself apply one click of up elevator trim with one or two click of left trim. About four minutes of flight and I decided it was time to land as that engine can go through some fuel at a fair rate. Attempts to cut the throttle on the final approach failed and a stuttering and almost-stalling motor were still spinning the prop. Even so, as the Magnum came in a healthy flair was still required to point that one practically runs out of elevator right before touch down. Having the prop still spinning made it hard to gauge just how effective that new wing is during the final glide but it did seem much more docile than the old version. Everything survived the first flight, including the prop, and after a post-flight check the model was pronounced as still being in tip-top shape.

The art of flying the Magnum is in keeping it close enough to be able to observe the model whilst retaining a safe distance from the flight line. It's easier said than done and if you're not used to something this fast then it can take a while to settle into a pattern, but once you do it's a real hoot. Personally, for me, every Magnum flight starts with considerable nerves which eventually settle down and confidence starts to build and continues right throughout the flight until it's time to land, whereupon the nerves start to return again - after landing you're right back where you started with jangling nerves, what a buzz! If you're still a bag of nerves before launch and you're not focused before the flight then abort until later. You need your wits about you and you need to be very aware of what is going on around you. Flying on the quietest days at your local club field is a very good idea, and being the only model in the sky during your first flights is optimal. It is very helpful to have someone "spot" for you and generally give you that extra set of eyes that you need. It's diminutive size makes the model so much faster than it really is, and lets face it, when it's stationary it looks like it's doing 200 mph. All in all the Magnum R is a hugely enjoyable model to fly, very simplistic in construction and makes for a very tidy installation. Coupled with the extremely pleasing visual aesthetics which get a lot of interest from anyone around at the time, it's a very good package. If purchased with the highly recommended West Eurotech .50 V1 it's hard to beat - to point that this is a model which has almost created a market for itself. I don't think I could fly one of these every weekend, but it's an extremely easy model to transport and prep which holds a lot of attraction for me and keeps me coming back for more.

 

Article by Phil Chisholm for Bumpy Green Model Aerodrome
July 2004

Comment by Keith Appleton on 20040905084054. Rating 3

THE DECALS ON THE FUSELAGE CAME OFF MINE ON THE BENCH! WARNING: MINE WAS FITTED WITH AN OS4X46, I FLEW IT LAST JANUARY ON A VERY ICY & COLD DAY. VERY FAST, IT FLEW WELL, BUT AFTER A SHORT WHILE ON THE 2ND FLIGHT, ELEVATOR CONTROL WAS LOST. WHEN THE WRECKAGE WAS EXAMINED, THE "SNAKES" TO THE ELEVATOR WERE BROKEN OFF & FOUND TO BE EXTREMELY BRITTLE - EASILY SNAPPED INTO NEAT QUARTER INCH SEGMENTS WITH LITTLE FINGER PRESSURE. HAS ANYONE ELSE HAD THIS PROBLEM?

Comment by Phil Chisholm on 20040905215218. Rating 5

Update - Ive now had a good two dozen flights on the MagnumR and have progressed through to using the 8x8 prop. It becomes a different beast all over again with a huge grin-factor. It makes some really interesting noises when its moving flat out - it almost seems to whistle. Another thing you notice as you get more familiar with it, flight duration gets less and less as you keep the throttle nailed more often. Ill try and get a part II article together as there is much to explore with different props and pipe lengths. This thing just keeps getting better..

Comment by Phil Chisholm on 20040906114031. Rating 5

All my flying with the MagnumR has been from April onwards, in warm(ish) weather. I have not lost a single decal yet, although the chequer-pattern underneath is starting to peel on one corner - nothing serious. I would imagine that cold weather would effect adhesion and would also make many different types of plastic quite brittle, particularly if the model was left in a cold garrage overnight. Certainly a point worth noting!

Comment by Carl Owen on 20050315101213. Rating 4

The plastic controll rod ends are not great, four broke when I was assembling the model, they seem to big to click into the servos. Mine were all changed to metal ones. Also the defaulf engin setting on the west 50 needed adjusting, my engine wouldn't start until I had three turns on the low speed needle! Other than that I now flys great!

Comment by Darren on 20050908141806. Rating 5

MAGNUM R : Ive fitted the magnum with a rossi 53 and it makes it fly like a rocket, the disavantage is it doesen,t like low revs which makes it a bit hairy on landing as it could cut at any point, apart from that the engine makes the plane alot of fun, one thing which needs to be done on fitting the elevater horns to the controll rods is make shore u use maximun elevater otherwise there is a good chance u wont be able to turn as u will need a lot of up elevater to bring her round. all in all this is the most exciting aircraft i have ever owned 5*

Comment by Steven Elliott on 20050920203322. Rating 3

my recent purchase of a Magnum r Kit with the west 50v1 engine was one of the best purchases I have made in a long time. The kit went together well and the first flights were totally mind blowing. I initially have fitted the APC 9x7 prop and even this is fast enough for me for the moment or until such times as i have overcome the initial nerves. One comment about the model was the CG which the instructions say 120mm -130mm. This is what i used initially but didn,t like the flying caracteristics so it is now at 145mm which seems to be much better and the glide is very flat and predictable with no tendency to run out of elevator control for the final flair-out. Excellent model and I would give this one 10 out of 10 for sheer performance.

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