First things first I think I should introduce myself, having never appeared within the pages of this hallowed magazine before. I am not completely new to the hobby having learnt to fly in my early teens, but after quite a long lay off due to various commitments I saw the error of my ways and took my debit card to the nearest model shop without passing go, whilst rejoining my old club (Tyldesley Model Flying Club). When a fellow club member and RCM&E Glider Columnist, Andy Ellison, asked me if I fancied writing a review for the Blackhorse SU31, I didn't have to think for too long before saying yes when I realised a free model was on offer.
Before the kit arrived I decided to have a quick look on the Internet to see if there were any threads discussing any problems that had been encountered with the model. I am glad to report that I was pleasantly surprised with what I read. It appeared as though there are a few 40-sized SU31 on the market from various large well-known manufacturers which all bare striking resemblances to each other. Differing only in the colour schemes applied. This led me to believe that they are all being built in the same factory, but probably to slightly different prices with the Blackhorse SU31 being considerably cheaper than the rest.
So what's in the box…?
Your hard earned pennies buy you; two wing halves, with ailerons pre-installed and pinned, a fuselage with canopy and pilot pre installed, a belly pan with a clever spring catch, horizontal and vertical stabilisers with the elevator and rudder pre-installed and pinned, good quality fibre glass spats and cowl, with an excellent colour match to the red Oracover, and various other standard modelling paraphernalia such as fuel tank, engine mount, control horns etc. Not bad for just over seventy quid is it? And you don't even have to stick the transfers on!
Taking a cursory look over the fuselage and wings everything seemed in good order, nice and straight and well put together. Although the Oracover had sagged quit a lot on the review model. Nothing an hour or so in front of the TV with a covering iron couldn't sort out though. A point to note at this stage is that the nice red and black diamonds on the fuselage are actually transfers and not trim so a little care with the iron is required at this stage. Further inspection of the fuselage revealed that the metal control rods for the rudder and elevator were already pre-installed and only required the covering over the exits at the rear of the fuselage to be cut away before gently pushing them through. The bulkhead comes pre-painted in a grey prima, although there is a distinct lack of any markings that are often seen on the bulkheads of ARTF's to act as a centring reference whilst mounting the engine.
Putting it together…
Before rushing in with the scalpel and glue I decided to sit down and read the instructions, which took all of two minutes. To say they leave a lot to be desired is a bit of an understatement. Although they appear, at first glance, to be sufficient, on reading they are a little disjointed and rely heavily on the pictures. To be fair though they do the job and you are getting a 40-size SU31 for £74 remember.
Having put a couple of ARTF's together since my return to the hobby I decided to ditch the instructions and only refer to them if completely desperate. If you've put a couple of ARTF's together yourself the degree of prefabrication with which the model arrives should have you in the air, rolling and looping, with just a couple of nights work.
I am not going to go into great detail about every aspect of the build process as the model is practically built when it is removed from the box, and I am assuming that you are not a beginner who wants to learn with a Sukhoi SU31. You're not are you?
I decided to tackle the wing first, as there didn't seem to be too much to do here since the ailerons were pre-installed. The aileron servos sit behind the hatch covers and are screwed into hard wood blocks. Twenty minutes work saw both aileron servos installed with the leads fed through the wings, helped along with a length of cotton that had already been run through the wing halves at the factory. Due to the position of the aileron servos it is necessary to attach extensions leads, and I found that 300mm did the job just fine. The next task was to install the horns and control rods on each half of the wing. I opted not to use the plastic retainers that come with the kit, relying on a Z-bend instead. Although going against my better judgement I did use the plastic clevises supplied. Normally these would be binned and replaced with metal throughout, but I didn't have any in stock at the time and I was keen to see what the model flew like ASAP. I have since acquired some and will be retrofitting them soon. At this stage only forty minutes had passed and the wing was almost finished bar the joining of two halves, but this is where I ran into some difficulty. Talking the wing brace and dry fitting it into the box in the wing, it soon became apparent when the wing halves were brought together that there was something amiss. Not only was there a gap of approximately 10mm between the two halves, but also there was quite a twist somewhere that saw one leading edge pointing skywards when the other was horizontal. Inspecting both wing halves I could only come to the conclusion that the fault lay with the wing-joining box. Confronting the extra length of the wing brace first, I simply chopped of 5mm from each side and did a quick check of my handy work with another dry fit. To tackle the twist I simply applied liberal amounts of epoxy to both halves and the wing brace, and whilst everything was setting I held it in the correct position with a couple of spring clamps on the trailing and leading edges of the wing. It wasn't any ideal situation but the wing appeared to come out straight, and I didn't fancy having to chopping into my new toy with a scalpel. To finish the wing off Blackhorse supply you with a strip of yellow tape to cover the wing join and tidy things up.
With the wing put safely to one side it was time to confront the fuselage. The plywood servo tray is pre-installed and the elevator, rudder and throttle servos sit line abreast. A quick flick with the scalpel and waft of the covering iron meant that all of the excess covering around the stabiliser slots and control rod exits were removed. Next I decided to mount the undercarriage so that model had something to sit on whilst I aligned the horizontal stabiliser with the wing. The undercarriage comes in two pieces and is fastened to the fuselage with four bolts retained with blind nuts. The wheels and spats were next, and required a little more thought. The wheels are held on a partially threaded bar, kept in position with two collets. Part of the thread passes through the undercarriage leg and two nuts hold the threaded bar and wheel spat in place, with the other end of the bar protruding through opposite side of the spat. Although not mentioned in the instructions I decided to strengthen the spat around each hole that I had drilled with a small square of light ply.
With the undercarriage and wheels in place the horizontal and vertical stabiliser were added next. There really is nothing to write home about here. Just make sure that the horizontal stabiliser is correctly aligned with the wing and be careful not to score the balsa when removing the excess film before gluing. Common sense really. The pre-installed control rods really aided the building process, leaving only the engine to mount and cowl to cut.
Supplied with the kit were four screws to mount the engine but I opted to use nuts and bolts instead to mount my chosen engine, an OS 46FX that I had managed to pick up second hand for seventy pounds with a Kyosho Cap 232 attached. Looking at the model my gut reaction was that maybe it would benefit a larger engine, but as luck would have it this proved not to be the case. Once the engine had been fitted to the mount it was time to attach it to the bulkhead. As I previously mentioned there were no guidelines pre marked on the bulk head, but with the large opening of the cowl I don't think you would notice if you were out by a couple of millimetres out either way. The way in which I approached it was to simply find the centre of the bulkhead and then align the centre of the prop shaft with this. In other words I did it by eye. Not the most scientific way but it seemed to work for me.
The tank was fitted, and taking a tip from one of the threads that I had read on the Internet I removed the foam that had been attached behind the bulkhead thus allowing the tank provided to fit without preventing the wing from sitting in place correctly.
All that was left for me to do now was to mount the cowl, and I must confess that I chickened out when it came to cutting it and took it around to Andy's. An hour or so later the cowl was mounted with two screws on either side as shown in the instructions. When fitting the cowl it became obvious that it appeared a little oversized compared to the model, but when in position and with a little careful coaxing it looked the part. The battery was fitted underneath the fuel tank to achieve a centre of gravity in the middle of the recommend range.
The best bit…
This is, of course, the part of the review that we all read first and quite frankly the most important in my view. There's no point in having an easy to build flying house brick is there?
In the past few months the weather has been less than favourable for us modellers residing in the suburbs of sunny Manchester, but for once I arrived at the flying field and actually had to contemplate the use of sun cream. It really couldn't have been better for the first flight of my nice shinny new toy. With the aileron servo wires hooked up to the Y-lead it wasn't long before the wings were on thanks to the nifty wing bolts that can be tightened with fingers alone (these will come into their own in the winter months when you want to get your model in and out of the car quickly). With a full tank of fuel I fired up the 46, gave it a lean check and carried the model out to the runway. Applying full throttle it soon became apparent that either the spats had to go or bigger wheels needed to be installed, as they were snagging on the short grass causing the models nose to tip forward. Once in the air it needed six clicks of left aileron, making me wonder if there had been a bigger problem with the wing joining than I had first suspected, but apart from that everything seemed fine. With Andy on the camera it was now time for a few low passes, and stall turns to get some good flying shots for the magazine. These completed I landed to refuel so I could have a proper twiddle of the sticks. The landing was much easier than I was expecting. My initial feeling, looking at the vast opening of the cowl was that this was going to act like a large airbrake, leaving the model prone to tip stalling at landing speeds, but with the motor at idle and a shallow sweeping landing approach no problems were encountered. Once on the ground however those spats were trying there hardest to tip the model forward so full up elevator was required and there was no chance of taxing. I think I will opt to remove them altogether.
I gave the model a quick check over, especially those plastic clevises, then refuelled and took off again. With the flying shots over I could now concentrate on how the model handled in the air. Taking the model through a series of inside loops everything seemed fine, although I was conscious that it seemed a little twitchy on the ailerons as I tried to make small corrections. Trying a rolling circuit the disparity between the role rate and the elevator throw became apparent. It just looked a little messy and felt unbalanced. I landed and altered the aileron throws but left the elevator alone. I also dialled in 30% expo on all of the controls apart from the rudder. The rudder had the maximum throw rate that I could achieve. I think that it is important to point out that you need to be careful with the elevator throw. With the elevator providing 50% of the tailplane area too much and you will find yourself flicking, and stalling the tailplane when full up is applied.
Taking off again the controls felt a lot more harmonised and I could really start to test how it flew. When I was initially considering what engine to put in the SU31 I was a little concerned that the recommend 46 would not be sufficient, but large loops can be held without any problems. Although when the nose is pointed vertical the speed soon drops of thanks, I think in part, to the large cowl opening. Taking advantage of all of the space in the cowl it would be easily possible to shoe horn a larger engine in if that was your sort of thing, but I personally think it would fly great on a 50-sized 2-stroke or 70-sized 4-stroke, but don't expect too many 3-D manoeuvres. The name of the game with the SU31 is old school high-energy aerobatics, with loops, rolls, avalanches, Lomcovacs knife edge, etc being the order of the day. I still had one niggling problem in my head though. Why did I need to apply so much left aileron to stop it rolling all the time? The answer to this came whilst applying the rudder on the ground during a pre flight check. Every time I applied right rudder and then released it would not centre. Taking the wing off it became clear that the rudder control rod was rubbing on the wing bolt, and because of the way that it was preinstalled simply moving the servo would not solve this without causing undue strain on the control rod and stalling the servo. Luckily due to the length of the wing bolts supplied approximately 1.5cm could be removed from the end, clearing the control rod.
Conclusion
I have to admit that if I had glanced at the Blackhorse SU31 in the model shop I don't think I would have given it another look. I had pre-conceived ideas before the model arrived that it may not be of great quality due to the price, or it would be difficult to land due to the high drag of the cowl, although both these have proven to be completely unfounded. The model arrives with a high degree of prefabrication and is of an excellent quality. The flight characteristics are great as long as you realise that it isn't and out and out 3D machine, but as a little word of warning if it does go dead stick don't mess around as much as I did because that cowl does become a very effective airbrake without that fan spinning around in front of it.
In short if you've ever fancied the look of a Sukhoi, but have heard many of the horror stories that are often told about them in the local model shop, forget all that and get yourself a Blackhorse Sukhoi SU31. It will only set you back just over £70 and will make a great addition to your hanger.
Datafile
Name: SukhoiSU31
Model type: Semi Scale Aerobatic
Manufactured by: Blackhorse
RRP: £74
Wingspan: 55 Inches
Length: 49 Inches