Trading from premises in deepest, darkest Kent, Weston UK have been supplying to an ever-hungry R/C market for many years. As well as offering the traditional model shop services of off-the-shelf kits, engines, R/C equipment and accessories, Weston have also developed a manufacturing side to their business. This includes highly tuned two- and four-stroke engines (sold under the banner ‘West’ and ‘Tuned by West’) alongside a number of ARTF kits – from Hype and Cougar to the ballistic Minishark and Magnum. The engines in question are tuned to run on Weston’s own fuel, Pro Synth, which is a fully synthetic brew. Designed to withstand the demands of 3D freestyle aerobatics, the 72” (1828mm) wingspan Obsession is an addition to their ARTF range that’s been available for a while now. From looks alone I was sure that the model would prove to be a hidden treasure, and I was keen to get started.
The kit arrived well packaged against any courier mishandling, indeed removing this revealed a colourful and nicely printed box featuring flying shots and specifications. All well and good, but what mattered was what lurked within! Here, then, I was greeted by plastic bags containing all the major airframe components, and wasted no time in extracting these bits for a closer look. The Profilm covering was slightly slack in places due to temperature changes during shipping, but this is the norm for many ARTFs so I wasn’t worried – the problem was easily cured using a heat gun and covering iron. Hidden underneath is an airframe of good quality, lightweight construction – essential for 3D freestyle flying. A comprehensive hardware pack and step-by-step instruction manual complete the picture and after a thorough study of the latter I was ready to get building.
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But my Obsession hadn’t arrived alone, she’d been accompanied on her journey by a large box full of various Weston bits and bobs, the most prominent being a Tuned by West Magnum 180 four-stroke, sporting a different head and carburation system to deal with the stresses of 3D freestyle flying. Nice. Incidentally, all the glues used during the build were also from Weston’s large range of adhesives, and I’m happy to report they worked very well.
On with the build, then, which proved to be very straightforward, save a couple of niggly bits that needed addressing. The instruction manual is superb, with excellent photo illustrations plus technical data and set-up advice. In keeping with the best traditions of RCM&E reviews I followed this to the letter.
The first task is to hinge all the surfaces using the supplied, large, Robart pin hinges, high quality items that offer maximum movement for 3D manoeuvres. A few drops of 1-hour epoxy into the pre-drilled holes soon have the hinges securely fixed. The fuselage-mounted servos are sited in the wing seating area in conventional fashion, yet instead of a long pushrod the elevators use a closed-loop system. Generally regarded as a plus point it’s good to see, although the geometry of the system can be somewhat fiddly to get correct whilst avoiding the six closed-loop wires (each elevator is actuated by a pair of wires, plus two more for the rudder) getting tangled. Once set up and working properly this arrangement provides a smooth, fast, linear movement, but if it sounds like too much trouble then two elevator servos could easily be fitted to the rear of the fuselage and connected conventionally using short pushrods. My servos of choice were two Hitec 625 MG Super Torque jobs for the elevator, a Hitec 5955 Titanium MG for the rudder and two Hitec 645 MG Ultra Torque items for each aileron. These all proved to be entirely capable of dealing with the loads imposed by 3D freestyle flying, and are also available from Weston UK.
With servos and linkages sorted it was time to get on with installing the West-tuned Magnum180, which was supplied with pre-drilled nylon ‘T’-shape engine mounts. The firewall is pre-drilled with two sets of mounting holes, one for two-stroke engines, the other for four-strokes. By the way, the four-stroke holes are at a slight angle to ensure the central location of any tuned pipe that may be used. And the use of such a pipe is well worth considering, given that there’s a pipe tunnel already built into the fuselage underside. I chose to use the standard exhaust, though, which meant a straightforward engine and fuel tank installation; 45 minutes and the job was done, topped off with a 16 x 8” APC prop.
The undercarriage is a simple bolt-on affair, its slightly swept back appearance adding much to the visual appearance of the model. The battery can be positioned in two different places to suit your C of G needs. In this respect I chose to secure it in the rearward location (classed in the manual as the ‘expert’ position) just behind the canopy. With the pack cable-tied to the appropriate former the centre of gravity comes out at 7.9” (200mm) behind the wing leading edge. Finished and ready to fly the final task was to stick the Obsession on the scales, where a reading of 11 lb (5kg) was displayed – about right for a 1.8m span ready to fly model.
Dodging the April showers I packed the Obsession into the car and set off for the field, having arranged a rendezvous with photographer Ben Dean. Starting the engine was a breeze. Prime it well, apply the starter and sure enough it would fire up every time. I ran a tank of Pro Synth 10% through the beast to make sure it was run-in properly, and whilst this was taking place (with the model properly restrained) I performed the usual range checks. Finally, with another sprinkling of integrity checks complete, we were ready to go.
Re-fuelled and with the engine purring happily, I lined the Obsession into wind. Opening the throttle wide she responded immediately, surging forward and leaping airborne within 8ft! From the outset it was clear that the 16 x 8” APC prop was a perfect match for the engine. A pull to vertical confirmed that power certainly wasn’t a problem, as the model just kept going! Levelled out at the top of the climb, I decided to try the stall. A real non-event this one, with the model just descending in parachute-type fashion.
Before wringing her out I chose to try some smooth aerobatics and was surprised how well she tracked, giving that self-assured ‘locked in’ feel. Cuban eights, rolling loops and one-roll circles are effortless manoeuvres for the Obsession. Another thing that surprised me was the complete absence of knife coupling – testament to the design. With this in mind I have no doubt that the aeroplane could be used in entry-level F3A with some success.
With a flick of the rate switches it was time to check the 3D envelope and in doing so I instantly detected that the ailerons needed more exponential than had been stated in the instructions. The first 3D manoeuvre I tried was the trusty blender, for if anything was going to fail it would do so here. With sticks to the appropriate corners, the Obsession span up and then flattened out beautifully, the model’s low inertia resulting in a slow, graceful descent which, using a little power, I turned into an inverted harrier that continued for the length of the strip. The model exhibited no wing rock at all during this latter stage and felt stable throughout. Rolling harriers are exceedingly good, and this is true for both directions.
One manoeuvre at which this model really excels is the knife-edge spin. Starting off slowly, she soon ends up spinning at very high speed around the wing whilst falling with her nose pretty much on the horizon. Prop-hanging is okay, but the slightly narrow ailerons have to work at inducing a torque roll. Interestingly, not much aileron is needed to hold the model against the torque in a stationary hover. She’ll prop-hang at around half throttle and will pull out with authority when punched to full. After around 12 minutes and with a question mark hanging over the fuel reserves, I decided to land. Here, as expected, the model just breezed in with no trouble, settling down nicely into a 3-pointer.
There’s no doubt that Weston’s Obsession Freestyle is an extremely capable machine at both smooth, F3A-style aerobatics and all-out 3D freestyle. This being the case I’m genuinely surprised that it hasn’t been more successful in the marketplace. Considering the relatively low cost of the airframe (£239.95), it’s an attractive proposition for anyone who can’t afford a full-blown 2m aerobat, and should also be a consideration for those who can! In a nutshell it’s a well built aircraft that can do the book, and I can’t find any reason not to recommend it. Available direct from Weston UK, a number of deals are available to suit different kit / engine / exhaust combinations; check out www.westonuk.co.uk for more info.
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