World Models Midget Mustang

Written by Maurice Ashby (dad) back in 2004 it's hard to believe that it's been nearly six years since the publication of our World Model's Midget Mustang review. Dad ended up building the aeroplane more by chance than anything, for originally, when the kit arrived in the office, I'd squirrelled it away with the intention of bagging it for myself. Why so keen? Well, a few years prior to this the Cambria Model Company had in its range a quarter scale Midget Mustang (traditional kit) that a clubmate had bought, built and invited me to fly. Powered by an O.S. 90 four-stroke I flew it, fell in love, and wanted one.

Alas, as is often the case, ongoing projects and restrictions on time prevented the indulgence and as the months rolled by my memory of the flight faded… That is, until a kit containing World Models' ¼ scale ARTF version of the same aeroplane arrived at the office looking for home. I had to have it and with the kit secreted safely in my shed I tried desperately to rearrange my building schedule to fit it in, but to no avail. Whilst it gradually became clear that I'd have to give my treasure away, it didn’t stop me from hatching a cunning plan, i.e. persuade father to review it, then steal the occasional go on a Sunday morning! Pure genius, it couldn't fail!

Now, fortunately, dad also knows a good aeroplane when he sees one and accepted the challenge with the enthusiasm I felt it so rightly deserved. The review was published a few months later and, in accordance with my dastardly plan, we both flew the model regularly in the weeks that followed. Finally, then, after about 18 months, swapsies were negotiated, a deal was struck and the Midget Mustang was finally mine! Now, at last, I could fly the thing like I stole it, which, in effect I had!

Since then and for reasons which I'll shortly describe, the MM has become my all-time favourite model. Truth is, I like it so much I recently bought myself another kit for fear that WM may one day attempt to devastate my life and remove it from the range. At time of writing however, it remains in production which, surely, has to be some sort of record by ARTF standards? Anyway, I'll let you read dad's original review, then catch up with you at the end to describe how she's fared over the last six years.

REVIEW BY MAURICE ASHBY
The (full-size) Midget Mustang was designed and built back in 1948 by the chief engineer of Piper Aircraft, Dave Long. An all-metal racer, the aeroplane made its public debut at the 1948 Cleveland National Air Races where ‘closed course’ midget racers (of the type) had to have a minimum weight of 500 lb, a minimum wing area of 66 sq. ft., fixed landing gear, a structure to withstand at least 6 g and a powerplant that was limited to ‘stock’ 190 cu. in. engines. The prototype Midget Mustang showed well in the competition, taking second place in the elimination heat and reaching the finals, where engine problems forced Long to retire. This didn’t daunt his faith in the project though, indeed he went on to build a prototype production version whilst making arrangements with Schweizer Aircraft to produce the design.
 
The Midget Mustang proved its early promise and became well known for its air racing successes in the late ‘40s and early ‘50s. In 1959 Robert Bushby purchased the rights to the design along with the tooling. Bushby began selling plans for the M-1 and as demand for the aeroplane increased, kits were also offered for sale. The kits are still available today and have improved so much that the aircraft can now be finished in less than 1,000 hours. Very few changes have been made to the Midget Mustang over the years, and it still retains its original racing appearance. Modifications by builders include larger engines, full IFR panels and additional fuel capacity. It’s an understandably popular choice and, as such, some 400 Mustangs (also known as the Long Midget) have been built around the world. The aircraft has been crowned Grand Champion at the International EAA Oshkosh Fly-in on no fewer than four occasions, and over its 50+ years it has acquired a reputation as being one of the best sport planes ever. Owners and pilots frequently claim it to be the most ‘fun to fly’ aircraft they’ve ever experienced and enthusiastically add that no current design can match it in terms of the thrill it provides and the performance it offers. So, the full-size certainly has pedigree but how does World Models’ offering shape up?
 
SMALL IS BEAUTIFUL, BUT...
Fundamentally I’m a small model enthusiast. I consider a model to be ‘large’ when it won’t go into my Astra hatchback in one piece! Of course, this also restricts the engine sizes I’m accustomed to, the largest being a .60 (wow!). So, when our editor (and my No. 2 son), Graham, said that he had a Midget Mustang ARTF kit looking for a builder, I fully expected something of modest proportions. As such I agreed to do it, and only then thought to ask what engine size it was designed for. “Don’t worry,” came the reply, “I’ve got that too, it’s an ASP 91 four-stroke.” Gulp! Can this really my kind of model? I don’t mind telling you I had my reservations. Determined to keep an open mind I cast my doubts aside and awaited its arrival. Sure enough, when it turned up I opened the box and was able to confirm that this is indeed a fairly large aeroplane, and not just by my standards, me-thinks.
 
Poring over the contents I have to say I was very impressed with the construction and covering of the model. Likewise, the fittings looked to be of very good quality. Assembly instructions are adequate, presented in the form of detailed sketches with limited written notes.
 

NITTY GRITTY
Right then, down to the nitty gritty. The first job on the ARTF assembly line involved cutting away the covering on each wing half to reveal slots for the undercarriage wire and, likewise, the location / fixing points of the aileron cover plates (one servo for each aileron). The ailerons themselves are factory-fitted and were very free moving, which makes a nice change from some ARTFs I’ve built in the past. Self-tapping screws secure the aileron servos to balsa blocks, these, in turn, being glued to the aforementioned cover plates. I must admit to being slightly concerned at fixing the servos to balsa, albeit fairly hard balsa, so I ran some cyano into the drilled fixing holes to harden things up a little. The cover plates were then screwed into the wing using four self-tappers, with just the servo output arm protruding through a pre-cut slot in the plate. A nice touch here is that a length of nylon line is pre-installed in each wing half to allow you to pull the servo leads through to the root section. Connecting the aileron pushrods is simple too. Supplied finished and bent to the exact lengths, they fit perfectly.
 
LANDING GEAR
Very straightforward: all one has to do is install the pre-bent undercarriage leg into the channelled mounting block located in each wing panel and secure with nylon straps and self-tappers. The fibreglass spats were fitted next, and after drilling a hole in the appropriate spot for the axle, plywood blocks were epoxied to the inside of the moulding; one to locate the axle end, the other for securing the spat to the undercarriage leg - again, with a nylon strap and self-tappers. The wheels are from fairly lightweight hard foam and are of good quality, located on the axle with a collet each side. With this, all that remained to complete the wing was to join the two panels, using a ply brace, in the usual manner.
 
At this stage I was surprised to discover that World Models don’t supply a white adhesive strip to cover the join, as is common on other ARTFs. Needless to say, a strip of Solartrim was employed for the purpose.
 
TAIL FEATHERS
The tailplane and fin were epoxy glued into their respective slots, having first removed a portion of covering film to achieve a good wood-to-wood bond. As with the ailerons, you’ll find that the elevator and rudder hinges are factory-fitted and free-moving. The steerable tail wheel is also a nice detail, well made, and screwed to the underside of the fuselage with the steering arm glued into the rudder.
 
UP FRONT
A quality fuel tank slips neatly into the fuselage and protrudes through the engine mount bulkhead positioning the fuel tubing within the cowl for easy access or replacement. Captive nuts are fitted to the engine bulkhead allowing the engine mount to be secured either inverted, upright or sideways, without affecting the thrust angles. I chose to mount the ASP .91 sidewinder fashion - a good move as the cylinder head is almost concealed by the side cheek of the cowling; it also makes engine operation easier. Nearly there now, indeed with all the major components in place, the servos and linkages could be installed.
 
To be honest, there’s not much comment required here, everything fits and is secured using common practice. Pushrods are supplied to the exact length, though you will have to add the wire ends using a combination of epoxy and heat-shrink tubing.
 


COWLING & CANOPY
The cowling is a really beautiful fibreglass item, in fact it seemed a shame to have to cut holes in it! Having to hack away at such a work of art could be a bit daunting, with the ever-present possibility of making a mistake and ruining the thing. However, World Models thoughtfully include a clear plastic half cowl that’s simply slipped over the mounted engine in order to establish the cylinder head and needle valve positions. When happy these are easily transferred to the main item.
 
As for the canopy? Once again, a very nicely moulded item that’s held to the fuselage by seven self-tapping screws. It’s the first time I’ve tried this method of fixing and I much prefer it as it allows you to remove the canopy at any time to add a bit more cockpit detail, clean the screen, or whatever! Incidentally, while we’re on the subject, the pilot supplied in the kit is nowhere near the same scale as the model. Consequently I’ve recently bought a 1/4-scale chap from Pete’s Pilots, who I’ll fit at the earliest opportunity. Well, that about wraps it up assembly wise and I think you’ll agree, she looks great!
 
INTO THE BLUE
As is often the case with our unpredictable weather, the first couple of trips to the flying site proved a little too windy for a test flight. Being thus grounded wasn’t a total loss though, as it gave me a chance to get to know the four-stroke. I’ve never operated a four-stroke before so it was the ideal opportunity to hone my starting technique and run a few tanks of fuel through her. A week or so later the perfect morning presented itself and, with Graham elected to do the test flight (he needs the fixed-wing practice after flying all those whirly things) we, rather excitedly, headed off to our local strip.
 
With the engine on song and slightly rich, he lined her up and slowly opened the tap, increasing speed until the tail lifted. At just over half throttle, she was airborne and climbing gently, with power still being fed in. I stood close by to put some trim in should it be needed, but after only a few clicks of up she was flying hands-off.
 
In case the engine stopped prematurely the model was kept at a safe height for the first few flights, ensuring every chance of getting her down safely onto our mown strip and preserving those lovely spats. With the control throws and C of G ‘as per’, everything seemed perfect; all the basic manoeuvres - loops, rolls, inverted etc. - were performed with ease, and with very forgiving stall characteristics she can be floated in for a three-point touch-down.
 
I’ve since flown the Mustang myself and find it a lovely aeroplane to fly. It has no nasty vices, well harmonised controls, and bags of power for large graceful aerobatics. In short, it’s a peach!
 

SIX YEARS ON...
Well, that's what dad thought of it and for my part it would be fair to say that I’ve flown this model a great deal since getting my grubby mitts on it, my flight log showing that in this last year alone it’s clocked up a conservative seven hours in the air. As such, I know the model like the back of my hand, am entirely comfortable with its characteristics and, thus, fly it in all seasons and in all weather. In effect it’s my hack, the model I reach for when I’m looking for enjoyable, reliable, R/C flight.

Perhaps the best way to explain the MM’s qualities and foibles is to describe an average flight. First however, a few words about the engine: You’ll recall that dad fitted an ASP 91 four-stroke back in 2004, an engine that’s been ultra reliable, easy to start and a genuine pleasure to own. Short of adjusting the tappets a few years ago I’ve done nothing to it but tweak the needle valve one or two clicks either way and change the glow plug. It starts instantly and (touch wood) has never stopped in the air. I’d recommend it to anyone, and indeed have on numerous occasions.

GROUND HANDLING
Love this model as I do, taxiing is not one of its strong points and whilst rudder control is both positive and effective, on anything other than very short grass the model has a tendency to tip forwards. As such, I tend to carry her to the strip.

Taking off is a delight with this aeroplane, positive and progressive application of power throwing enough air over the elevator to keep the tail down and as speed increases. Holding the line with right rudder and easing off some elevator sees the tail lift, after which a gentle reapplication sees the model rise gently into the air for a beautiful scale departure. My model rarely leaves the ground with full power applied, it’s just not necessary.

Once in the circuit you’ll find all controls beautifully harmonised and positive. This is an aeroplane that goes where you point it and holds station well. It’s responsive yet not twitchy, powerful but not excessively so. What’s more, handling is delightful and it has no vices. It will stall, but you have to push it quite hard and even then you’ll only detect a gentle drop of the wing which is so very easy to control. These characteristics give the model a broad speed range, though you mustn’t automatically assume that because it’s a racer it’s fast. Don’t get me wrong, it doesn’t hang about but it’s no bullet either.

Rest assured there’s nothing harsh about this aeroplane, in fact, once you’re in the groove it’ll make your flying smooth and accurate. For my part, flowing manoeuvres look best, a gentle transition between each really displaying the model to it’s full potential. Meanwhile, power from the ASP provides vertical performance enough to pull lovely large loops and gorgeous reversals with ballsy, prolonged 45° up-lines.

AEROBATICS

Aerobatically, it’s a peach of thing. A touch of down elevator is required for inverted flight where you’ll find the model almost as stable as right side up. This is an aeroplane that inspires confidence to the point that fin scraping, low level inverted passes become second nature. Trust me, it encourages you to show off, which is exactly what I was doing that day I reduced my inverted pass to wagon rut height and dragged the fin along the deck… this before skidding to an inverted arrival that damaged… wait for it… absolutely nothing!

What else will she do? Well, she’ll fly a beautifully controllable scale-looking flick roll, performs a similarly comfortable spin with a recovery that’s dead easy to anticipate, and will track around a bunt with the best of ‘em. Look at that deep fuselage and you’ll not be surprised to hear that knife-edge flight is pretty good too, though you will need all the available power and be prepared to add down elevator and a tad of aileron to hold the line. I’ve never bothered, but you could, of course, compensate here with a little Tx mixing.

Barrel rolls? Beautiful… and barrelly! Square loops? Square! Derry turns? A delight and nicely crisp, too. Oh, and when it comes to flying a stall turn all I can say is super! I have to gently steer my Mustang with rudder during the ascent (still not perfectly trimmed, I guess), but once up there a bootful of rudder sees her turn tail and perform the nicest of manoeuvres, with just a hint of tail wag on the way down.

GETTING DOWN
I was having a conversation with a clubmate the other day and we both agreed that taking off and landing were our favourite manoeuvres. Performed well, and with the right aeroplane (World Models’ Midget Mustang!) I can happily spend all day just doing circuits and bumps. Suffice to say, this model handles itself as well during the landing phase as at any other time, indeed given the benign stall and slow speed characteristics you can bring her in with complete confidence for a gentle three-pointer.

Now, it’s a fact that landings aren’t everyone’s cup of tea, although you will need to be both confident and proficient to get this one down gracefully and without damaging the spats. Bleeding the speed off is key here for the MM’s a slippery ship that doesn’t suit tight landing strips. Run into the rough at speed and you risk the relatively light gauge u/c wire springing back and allowing the rear of the spat to punch a hole in the wing covering. In order to get her into tight spaces, then, you need to be totally aware of the aeroplane’s stall speed, and proficient at bleeding off speed on finals. Get these two sorted and you’ll have her totally under control, allowing graceful arrivals time after time. Mind you, don’t get too hung up over the spats, after six years of regular flying (and soft landing) I’ve only recently replaced the spats with a new set.

In terms of the airframe’s durability, I’d have to say it’s good. Due mainly to the fact that we didn’t fuel proof the engine bay, I did suffer a loose firewall late last year, which was quickly and easily re-secured, but that aside there’s little but good news to report.

World Models’ Midget Mustang has been the perfect Sunday morning semi-scale aerobat that suits me down to the ground in almost every respect. As I’m sure you’ve gathered, it comes very highly recommended and, given my comments about landing, would suit anyone who confidently flies a traditional low-wing aerobat.

DATAFILE
Model type: ARTF Semi-scale aerobat 
Manufactured by: World Models (China)
UK distributor: Steve Webb Models, 01928 735225, www.servoshop.co.uk 
RRP: £171 (as at Nov 2009)
Wingspan: 60''
Wing area: 668 sq. in.
All-up weight: 7.5 lb
Wing loading: 25.9 oz / sq. ft.
Control functions: Aileron, elevator, rudder, throttle
Rec’d engine: .60 two-stroke, .90 four-stroke
Engine used: ASP .91 four-stroke
Propeller: Master 13 x 8''
Plug used: O.S. type ‘F’



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