[Courtesy of Klaus Weiss, kkw1 "at" bigpond.com, September 1998]
When Walter Extra designed his Extra 260 aerobatic monoplane, its success in competition assured that it would become a subject for R.C. modellers and would be manufactured in a variety of scales. There are quite a number of kit manufacturers producing the Extra these days, many of them in an ARF configuration.
The Extra 300S is a single seater with a slightly modified and lower wing seat than the Extra 260 version. The Ilsan Industrial Company, of Korea, has an excellent version of the Extra 300S in a 20% scale (sports scale) configuration and the kit is pre-built to a high stage, as well as being covered in a striking colour scheme. There are still a few fiddly steps required to finish the model completely, but they are very straightforward and should not present any problems to the average builder.
The box is quite large and depicts the colour scheme of the model which is inside. The wings, fuselage and tailplane are packaged in separate plastic bags, as is the hardware and ABS plastic parts. The instruction booklet explains the assembly steps quite well, and is written in Korean(?) with English translation below. The fuselage is balsa/ply construction and the wings are foam core/balsa sheeted, with balsa sheet tailplane. All the separate sections are pre-covered and trimmed, leaving very little for the builder to do in this area.
The workmanship is of high quality in the Ilsan kit, with the all important wings, fuselage and tailplane being straight and warp free. The covering on this kit was of a better quality than what is usually seen on ARF kits, but it would still be a good idea to iron the edges down (low heat works well) and even seal them with thinned epoxy at the same time you are fuel proofing the firewall, tank compartment and other exposed timber which may come into contact with fuel.
The hardware package is quite complete, containing an excellent pre stressed alloy landing gear, ABS cowl and wheel pants, engine mount, tank, spinner and screws, bolts, nuts etc. There is a parts list in the instruction booklet, so tick off the parts and take time to read it through before you start assembly. Assembly. I will gloss over the assembly, as it is fairly well illustrated and detailed in the instruction booklet.
Glue the die cut plywood servo tray and support into the fuselage. Assemble the die cut wing bolt plates and glue with epoxy. When the epoxy has cured, insert the blind nuts into each hole then epoxy the plate into fuselage, as shown in the directions. Wings. The wing halves are butt glued with epoxy and held in place with tape until cured. The servo well is lined with balsa and plywood sheeting and the servo rails glued in after that.
Re-inforce the wing joint with the supplied fibreglass cloth, using thinned epoxy. The front former is then epoxied in place. Align the wing on the fuselage, making sure it is centred, then mark a reference line on the wing and fuse to ensure it will be correctly re-aligned and glue on the rear wing bolt plate. Drill the holes for the front wing dowels and glue them in. Attach the wing and ensure it is still aligned with the reference mark, then drill a hole through the wing, using the wing bolt plate as a guide. Measure the alignment and if satisfied, finish the bolt holes. It really is as simple as that. Bolt the wing onto the fuselage and trim the ABS plastic fairing to fit onto the front and rear wing formers. This step is well described in the booklet. Couldn't be easier.
I used Robart hinges on the ailerons, and this was purely a personal choice. If you use the supplied hinges, make sure they are pinned for added security. Fitting the fin and stab is a piece of cake, but wait before you glue in the rudder and elevator halves. The tail wheel assembly needs to be fitted first. The supplied unit on my kit didn't fit too well, so I replaced it with a Dubro unit. Bend the tail wheel shaft as shown and then epoxy the rudder and hinges etc in place.
The engine mount is two piece and adjustable, so it allows a wide scope for a variety engines brands to be used. The blind nuts are already in place in the firewall, so it only requires the mounts to be bolted on. Its a good idea to use a thread locking compound when the mount is secured to the firewall. The firewall on my model had some right thrust built in (about 1 degree) so that should counteract the torque of the engine on the take-off. I am not a great fan of ABS plastic fittings on power planes. They invariably crack after some little time, and are not too resilient in the event of a hard landing (crash!!). I joined the plastic parts as detailed and then had a mould made for a fibreglass cowl. I must say however, that I have since seen a number of these Extras which have been flying for some time with no damage to the plastic cowls, so the glass unit is again, a personal choice.
The landing gear, canopy and control hook up are adequately outlined in the instructions. There is an option to use pull/pull on the rudder, and this is a great system, but my kit did not have this option supplied, so I used a pushrod system. Paint the wheel pants and cowl, maintaining the colour trim for effect, and get ready to test fly this baby. I installed the popular O.S. .46FX engine in the Extra, and only had to move the battery to get the recommended C.G. Invert the model when checking the balance, for a more stable indication.
I ran a few tanks full of fuel through the engine prior to the test flight, just to get it running perfectly, and it didn't miss a beat. Fuel used was Powermaster with 5% nitro.
This is the important part of any review and is usually the shortest, but if it flies well and performs all that is asked of it, what more is there to say. Do a pre-flight check of the model, making sure everything moves in the right direction and all is secure, then range check the radio with the engine running at high and low revs and top up the fuel. No more excuses.
The Extra was struggling through the long grass of the field, so the wheel pants were removed, which made things a little easier. Throttle up, standing behind the model to see how much rudder control is required to track straight, and away it goes. The model wanted to veer right slightly on initial acceleration, but as soon as the tail wheel came up, it tracked straight down the runway.
The Extra lifted off on its own accord after about 50m and a gentle climb out and left turn had it ready to set up the circuit. A few minor trim adjustments and three quarter throttle had the model flying almost hands off. The stick was pushed forward and the O.S. .46 came on song, screaming across the sky. High speed passes with rolls in the climb out looked terrific and the response to controls was very positive. The O.S. engine has sufficient power to pull this Extra around, and a bit to spare. Low speed stalls are straight ahead and the Extra just mushes along until flying speed builds up again. I always balance my models laterally, so that the wings will not tip it one way or the other, and this certainly helps when flying at low speed.
The Extra has a very good glide ratio, so explore this in case you have a dead stick landing. Landing is straightforward as you control the descent rate with throttle and elevator. Keep it in line with rudder and ailerons and fly it in slow. There is no need to come in hot, as the response is solid throughout the speed range. The Extra 300s can bounce on landing, due in part to the stiff undercarriage, so practise the landings until you can flare it in, just inches from the ground.
Aerobatics are what this model is about, and it is capable of a large range of manoeuvres, more than I can accomplish at any rate. Loops, spins, inverted, knife edge, split 's' etc are all easy to do with this model. Snap rolls are a breeze, particularly on high rates, and the Extra recovers as soon as you release the input.
In all, this model flies as though on rails and will handle any manoeuvre I can do, and more besides. It is easy to see why the Extra 300s is such a popular aeroplane, both in full size and versions. It is an aerobatic thoroughbred, yet can be flown docile enough for the novice pilot to feel comfortable. For the pilot who has graduated from a trainer, and wants a little extra (no pun intended), or the expert who wants a bit of fun, the quick building time of the Ilsan Extra 300s and its moderate cost, represents pretty good value.
The Extra 300s is distributed by Model Engines, 44 Downing St, Oakleigh, Victoria 3166. SPECIFICATIONS. EXTRA 300S SPORTS SCALE 20% AEROBATIC ARF. WINGSPAN: 1480mm (58.3") WING AREA: 596 sq.ins FUSELAGE: 1206mm (47.5") WEIGHT: 2.7kg-3.1kg (6lbs - 6.8lbs) ENGINE: .45 - .60 two stroke (.70 - .90 four stroke) RADIO: 4 channel (used- JR 388S 8 channel computer - 511 servos)