• Wing Span: 56 in (142 cm)
• Wing Area: 567 sq in (3658 cm²)
• Length: 49.5 in (126 cm)
• Weight: 5.5 lbs (2.5 kg)
• Engine: .20 - .40 2 - cycle
  (3.3 - 6.5cc 2 - cycle)
• 5 Servos required

The Hobbico Twinstar ARF comes very well packaged with the pre-built sub-assemblies neatly bundled and protected against damage. An excellent instruction book with many pictures per page detailing the building process is provided. As is the case with most ARFs, no plans are provided . The hardware package provided is surprisingly complete, including fuel tanks, spinners, wheels, and all mounting hardware.

The building proceeds very conventionally for an ARF. Assembly cannot be completed in an evening or two as is the case with some ARFs. There is simply too much to accomplish. Patience in the assembly of this model will result in a great looking plane.

Assembly begins with the wing; building the wing joiner, adding the ply wing root pieces, cutting out the aileron servo hole, etc. The engine nacelles were fuel-proofed at this time rather than later in the assembly process as called for in the instructions. The nacelles are easier to handle prior to being attached to the wing. AeroGloss clear Hot Fuel Proof Dope was used for the fuel-proofing. Also, glue was applied to all joints of all parts that could be accessed on the entire model.

A bit of sanding was required to allow the nacelles to slide onto the wing and firmly seat. Next the throttle servo holes were cut for each wing and the associated lite-ply servo mounting plate attached. Strings are installed to facilitate pulling the servo connectors through the wing. These are a real help later after the wing halves are joined. Often, gluing the wing halves together can be tricky due to the wings tendency to slip out of position due to dihedral or trying to align the halves using some sort of weight. Hobbico has solved this problem rather neatly by combining the wing hold-down ‘dowel’ in the wing root ends. As such, it provides for a nifty place to clamp the halves together during the wing joining process. Drilling the wing hold-down bolt holes and installing the blind-nuts is rather straight forward. It is rather clever the way they have you use o-rings on the underside of the wing bolts to keep them from coming out and getting lost.

One curious thing about mounting the tricycle landing gear is that the nose gear has a ‘flat’ ground into the main strut, whereas, the main gear do not. A Dremel tool was used to grind a ‘flat’ on each of the main gear pieces prior to installing the wheels and wheel collars.

Attaching the stabilizer was very straightforward. The only caution is to be sure to check the alignment frequently while the epoxy is setting. Attaching the fin caused some concern. The fin did not ‘bottom out’ on the stab. As a result, an additional 1/8" piece of balsa was glued to the bottom of the fin and sanded down until contact was made. If the fin is not seated on the stab, the only thing holding it to the plane is the tiny overlap, front & rear, of the fin and main deck. Again, check the fin alignment while the fin is drying.

The shrink-wrap that holds the pushrods together is not very trustworthy. The shrink-wrap was removed from each pushrod and un-waxed dental floss was wound around the metal rod inserted in the wooden pushrod. This was then saturated with thin CA.

The radio gear went in without problems since there is plenty of room. The control horns went in just as easily.

The Twinstar is powered by the recommended OS .25FP engines. Hobbico suggests that if .40 size engines are used, they should be bushing engines, i.e. the OS .40 FP or LA. Thee ball-bearing engines have too much power.

The new OS .25FP’s were broken in with a couple of tanks of fuel on the test stand before they were mounted on the plane. Next, getting the pushrods exactly the same for each engine was difficult since no two engines run the same. So, a Futaba 8UAF was used so that its mixing features could be used to balance the engines.

The decision was made to use the Throttle-Mixture feature of the 8UAF (TH-NDL) rather than the Y-harness that was suggested in the instructions. The right engine servo was plugged into channel 3, the throttle channel, and the left engine servo into channel 8. Using this setup allows adjustment of the right engine (master) first, then using the channel 8 knob, fine adjustments can be made to the left engine until the engines are synchronized. In addition, this setup allows the throttle-cut switch to kill both engines. This proved to work out very well. An hour synchronizing the engines at home instead of at the field in 90 degree heat.

On flight day, the engines were fired, idle adjusted, control surface directions double checked, and the TwinStar was taxied out. There was a good breeze blowing about 45° from the left as the take-off roll was started from right to left. As power was applied, the Twinstar accelerated rapidly and lifted off at a little over half throttle. It flies as if on rails. Rolls are very axial, stalls are straight ahead and recoveries are easy. Landings are straightforward as long as it is not floated in like a trainer. This plane slows down very quickly on final approach.

The Hobbico Twinstar ARF is a quality airplane and should provide a lot of enjoyment. It was chosen because a desire to try a twin, something that would look great, and yet be small enough to fit in the car trunk. The TwinStar met and exceeded all expectations. This airplane will do anything that the average modeler is capable of asking it to do, and then some. It is great for a first-time twin, and cannot be beat for stability. The TwinStar will be used as a test bed to experiment with using differential throttles, i.e. synchronizing the engines with the rudder for smother turns, and throttle out situations. These experiments will be the subject of future articles.