Andy Gower finds much to admire in Seagull’s 80” ARTF Chippy
The Chipmunk, I’ve always assumed, is very much a British aircraft, indeed the image of a Chipmunk was as British to me as the thought of a Spitfire doing a victory roll over the Kentish countryside in the summer of 1940. So, I was surprised to find that, in fact, the Chipmunk was both designed and first flown by de Havilland in Canada. Apparently, at the end of World War II de Havilland in the UK was keen to develop a new low-wing trainer to replace its aging Tiger Moth but was too busy developing new jet aircraft so the task was handed to the Canadian operation. Accordingly, the Chipmunk first flew in Canada in May 1946 and was in service later that year. Mind you, whilst production started overseas, the majority of Chipmunks (over 1000) were actually produced under licence in de Havilland’s UK factories for the RAF and other air forces.
The Chipmunk has always been a favourite R/C model and has been widely available to us in many forms and sizes over the years, from plans to ARTFs. The attractive look combined with generally great flying characteristics have made it a very popular model, not least because Chipmunks are usually well-mannered and behave like a low wing sports model, but are capable of a reasonable aerobatic performance, just like the full-size. It’s just what most club flyers are looking for and, as a bonus, you get a scale model without the cost and trouble of retracts. Can’t be bad!
When Seagull came out with its new ARTF, its 80-inch wingspan and striking yellow Royal Canadian Air Force colour scheme (there’s also an Army Air Corps camouflage scheme) was immediately appealing. These versions make a pleasant change from the most commonly seen red and white RAF livery. Anyway, to add to the attraction of the bright scheme Seagull has made a serious attempt to cater for electric flyers like myself and has duly provided a removable top hatch / canopy, removable battery tray and a clever electric motor mount. I was keen to have one.
On lifting the lid and eyeing the contents I was immediately impressed with the sprung oleo-style undercarriage legs that promised working landing lights on the spats. Better still, the model looked well-made and well covered with no apparent wrinkling on any of the Oracover surfaces. Alas, the downside was the pilot and his passenger and whilst not the usual Year Three schoolboy size we would normally expect – these seemed about the correct 1/5 scale – they just look wrong. In fact, they look as if they’ve just stepped out of a Tupperware F15! Incidentally, I’m off on hols to Vietnam shortly and will be on six Vietnam Airlines flights I will make it my mission to check the size of my pilots to see if they’re all the size of a European eight-year-old. If so, I will have cracked the mystery of why ARTF pilots tend to be too small!
Given how lovely the rest of the model was assembled, replacement pilots were needed and here realmodelpilots came to the rescue. A chat with Sean allowed me to sort out what sort of chaps I’d like in the cockpit, indeed not only did we discuss scale, size, headphones and microphones, I even got to choose the colour of their clothes. A few days later two superb pilots appeared and all for under £80! Mind you, I have to say, they look a bit sinister to the point that if they landed at my field I’d be checking to see if any Chipmunks had been stolen in the area or if a drug raid was imminent!
The assembly progressed very much along the lines of any ARTF from Seagull, which has a reputation for producing good quality but affordable aircraft. Having built several I can attestthat all have been good. Down to the nitty-gritty, then, and the wings went together well with ailerons and flaps easily installed with rather unusual flap hinges which seem to work perfectly well but have a habit of coming unhinged and, thus, require the addition of a small elastic band positioned clevis-style around the pin (see photo). One particularly important point to note is that not all the glass fibre horns are born equal, so it’s essential to make sure they’re paired correctly. Try extracting an epoxied horn from a control surface and you’ll only make the mistake once, I can assure you). The all-important undercarriage is a very straightforward affair to rig, although the instructions here are misleading in that they show removable axles to enable the spats to be slid over. In reality the axles are fixed and the leg has to be removed from the base via three grub screws. The spats, meanwhile, need re-drilling to ensure that the aperture for the leg base is totally covered. While we’re on the subject the LED landing lights on the spats are designed to run from a Y-lead of the main switch, although in hindsight I should really have them linked to the flaps.
Where the fuselage is concerned the first stage is the electric motor installation and here, rather incredibly, the manual suggests an 8 to 9S LiPo set-up. That’s a bit excessive to my mind, indeed with a stated 10.5lb all-up weight (the actual is 13lb) I considered that a 6s set-up would be fine, especially as prop hanging is not normally associated with a Chipmunk. Anyway, with that in mind I opted to try a new motor, a J. Perkins EnErG 26cc (C5-30) brushless job offering 390KV. For this unit the specification showed that with a 17 x 10” it should produce about 1500 watts, equating to 150 watts per pound which, I considered, should be plenty of power. To this a matching EnErG 85 watt Opto ESC was coupled and, as I do with all 4S (and over) electric set-ups, a separate flight battery was used.
Now, one small problem with the motor is that the prop adapter grips the shaft using a tapered collet arrangement, which I don’t much like. I prefer the prop adapter to screw to the front of the motor, particularly so in this case as the motor shaft is only 6mm diameter, offering only minimal surface area for the tapered adapter to grip and, arguably, not enough when swinging a big prop. In the event my fears were well founded when my 17 x 10 flew off the front, even though I’d fully tightened the prop adapter nut. Sadly Perkins doesn’t offer a screw fitting prop adaptor, however I found that the E-flite Power 60 version fits perfectly, so that’s what I used. On the plus side, motor installation is one of the cleverest I’ve seen in an ARTF as the mount slides to the correct position no matter what length of motor is used. Just glue in place when the cowl has been positioned to check the correct spinner backplate clearance. Having done this, the mounting is braced with wooden quadrants. At the blunt end the tailplane, rudder and elevators all went on very easily and seemed to be in perfect alignment.
With this, the pilot and passenger were installed (having first checked my wallet!), and the canopy fixed / screwed to the top hatch which, itself, is secured to the fuselage using four M4 nylon screws. If I’m being honest I’d much prefer to see locator pegs and rear magnets used here as this not only looks much better (no visible fixings) it would be much quicker to take off and put back on. Moreover, the four small screws can easily be lost at the flying field.
The decals were slid in place with the usual soapy water spray to make positioning simple, although I opted to leave off the decal with the alluring lady on a playing card as I couldn’t see her on photos of the full-size aircraft. She’d be far more at home on a B17! Taking things just a little further I even sprayed the grey APC prop black and painted the yellow tips and whilst this particular Chippy should have its number on the cowl, as per full-size, that will have to wait. Now, one rather frustrating problem that I encountered (and I’m not alone) is that the aluminium wing tube is the tightest ‘fit’ ever. I tried several solutions, glass paper, PTFE spray, twisting the tube repeatedly and, after a while, lots of bad language! Which worked? Well, a combination of all helped but I still ended up with the second wing that wouldn’t quite reach the fuselage, stopping just 10mm short and doggedly refusing to go any further, no matter how much I swore. As a point of interest I have a friend in Suffolk who would take an engineering approach to this problem and spend the next three weeks in his loft whittling down the tube or easing out the hole. Valuing my remaining time on the planet, I, on the other hand, found a neat solution in the form of a pipe cutter. As a result the wing tube is now 10mm shorter and it took just five minutes to get that root rib sitting snuggly against the fuselage. My thinking was that if the wings clapped hands on the first flight, I would allow my friend the last laugh. Even so, the aluminium wing tube was still very tight and I will admit to developed RSI in my right wrist trying to reduce the size of it a little with emery paper.
Checking the C of G proved very straightforward, with the receiver battery and the ESC mounted on the motor box in the cowl (perfect for cooling) and the 6s 4500mAh flight battery pushed fully against the front bulkhead the model was just very slightly nose heavy at the recommended 130mm behind the leading edge, as per the manual. A quick test with a wattmeter indicated that the motor was producing just over 1400 watts with the 17 x 10” APC-E prop. As I’ve already mentioned, Chipmunks aren’t designed to perform extended vertical climbs so I surmised that this would be plenty of power.
Finally, my only negative comment on the assembly of the model at the field is that the wings are attached by a pair of M4 steel bolts which could easily be lost at the field. Anyway… The test flight took place on a calm day with a slight 3 to 4 mph wind and broken sunshine. She looked splendid sitting on the freshly cut grass strip while Ed. Graham took the ground shots before the maiden flight. In the event she took off with a strong torque swing to the left to the point that a fair amount of rudder was needed to keep her tracking straight and true. In the climb-out a few clicks of right aileron and about four clicks of up elevator were fed in to keep her level and, thankfully, it was apparent that the 6S set-up was delivering plenty of power. Actually, I’d describe the power as near perfect, with scale-like passes being achieved at just one third throttle. Taking her up higher, half and full flap gave no perceptible pitch change. She did feel slightly stodgy mind, even though flying on high rates so the 30% Expo needed cutting down for the second flight. However, she felt nervous and when slowed for landing and applying slight elevator, she stuck her nose in the air and threatened stall.
The next few landings were mixed, all bouncy with an even a bigger bounce on full flap. She just didn’t fly and land how a Chipmunk should. With this, the great and the good of the club gathered and pondered. Hands were inserted under the wings and on the wingtips and the majority agreed that the C of G was too far back. Then, just to check that she really wasn’t behaving properly, the ‘top’ flyers had a go with her and most of the landings were ‘interesting’, indeed one such would have set a new Olympic high-jump record. These were flown with the Expo down to 15% and slightly increased throws on elevator and rudder. Anyway, I was relieved to see that it wasn’t just me.
Now, as it happens, in the period between receiving the kit and flying it, Seagull had decided to alter the recommended C of G position, the new dimension being 100mm behind the root leading edge, some 30mm further forward than originally suggested. With this information to hand the consensus was to bring the C of G 20mm forward to 110mm. This revised balance point was accomplished by adding 325grams of lead to the nose (that’s 11.5oz for those who aren’t bilingual).
On the next flying session, with about 6 to 8 mph of wind, take-offs were achieved with an initial dose of full elevator to stop her nosing over and then a great deal of right rudder to keep her straight. She lifted off cleanly whereupon a few clicks of up elevator were needed to compensate for the extra nose weight. This time she felt much better and had lost that sense that she was waiting to bite you if let her. Gentle flying was the order of the day and a full flap landing was achieved with just enough throttle being fed in to overcome those large flaps hanging down. She touched down beautifully with not the hint of a bounce. Taxiing was a little tricky as, once again, full elevator was needed to stop her nosing over. To help here a little extra rudder and elevator were added to help with the ground handling but I was more than happy for she was now flying beautifully. Aileron and elevator response seems perfect to the point that lovely scale rolls and large loops can be flown with confidence. A little rudder input helps in the turns but that’s absolutely to be expected and a big part of the Chippy flight experience. Sorties of about eight minutes seem to be the norm for the 4500mAh packs which are left with a good 1300mA (about 30%) on landing.
This is a well-made, good looking aeroplane that will have a wide appeal. The thought-out electric set up option makes a real change from some ARTFs on the market and although I’m a fervent electric man, I would have to admit that this one would be great with a four-stroke up front. The negatives are, as usual, the pilots plus, the wing tube and top hatch fixing. At 80 inch wingspan Seagull’s Chipmunk has real presence in the air and just looks spot on. It’s also a pure joy to fly (once the C of G is sorted) and at a price which is pretty reasonable for a model of this quality and size. This is not a first low wing trainer and much more for the intermediate flyer but I think that this adds to the appeal as she needs to be flown. The only downside I can see is that the yellow version is so pretty that it’s not likely to be the only one in the club for very long. My advice is to try and persuade your clubmates that the Army Air Corps camouflage version looks even better!
Name: DHC-1 Chipmunk
Model type: ARTF scale trainer
Manufactured by: Seagull Models
UK distributor: J. Perkins Distribution – www.jperkins.com
RRP: £349.99 Wingspan: 80” (2032mm)
Fuselage length: 57.2” (1452mm)
Wing area: 937.8 sq. in.
All-up weight: 13lbs
Wing loading: 31oz/sq. ft.
Rec’d engine: 20cc petrol
Rec’d motor / LiPo: 2000W brushless outrunner; 8 – 9S LiPo
Power system used: EnErG 26cc (C5-30) 370KV brushless motor; EnErG 85W Opto ESC. 17 x 10” APC-E propeller
Functions (servos): Aileron (2); flap (2); elevator (1); rudder (1); throttle (via ESC)
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