One of the disappointing things about the Twinstar II was its power. It always took a while to gain speed and spent a fair amount of time at high throttle settings to fly fast enough to have energy to get over-the-top. As the stock Speed 400 motors got older, things only got worse. Only one thing to do – upgrade!

After reviewing several message threads on E-Zone and other RC sites I decided to go with some relatively small brushless motors and ESCs with a capacity of about 50% higher than the motors’ max amperage. The choice was a pair of Turnigy 2209, 26 turn 1130kV, 15amp motors from Hobby City and 25 amp speed controllers. The motors fit in the stock motor mounts and with just a little foam excavation, the ESCs fit right behind them in the nacelle. I used bamboo skewers to form a rack for the ESCs so they wouldn’t “get away” in flight.

After a false start with the stock power and servo connector that came with the kit, I decided to wire heavier duty connectors to the power cords instead. When I had gotten things to where I originally thought I needed them I discovered the wattage produced through the old connectors and with the 8 cell 2000mAH NiMH battery was pathetic. Rather than experiment with some of the components to see what might be holding things back, I replaced several things at once. I added a 2.4 gHz receiver for my new Spectrum 7c radio, a homemade battery cable that split into two to power both motors from one battery and reprogrammed the ESCs for a lipo battery. In this case, a 11.1 volt 2100 mAH model. Lastly, off went the 5.5X4.5 props and on went a pair of 7X6s.

All together, the changes made a big difference. I went from a paltry 65 watts to over 275! My sense is that the resistance of the new props and the added voltage of the higher capacity battery were the main contributors to the increase.

The test flight was perfect. At about 3/4 throttle, I could feel more pull than the stock motors ever gave. With that I gave it a toss and it climbed away with no sink or wobble. A couple of clicks of trim was all it needed. The brushless Twinstar II climbed effortlessly and rolled and looped with ease. I had found that it had been a little sloppy in turns so I took the lazy man’s way out and mixed some rudder with the ailerons. That also made a noticeable difference.

On the forth flight with the new motors, one of the prop-saver style prop collets that came with the motors came off right at launch. Low speed and asymmetric thrust spelled crash and so I picked up the now separated nose separately from the rest of the plane. This is where the Elapor foam really stands out. I ran the nose under some hot water to inflate some of the foam beads that had collapsed in the crash and let it dry. A little CA and the nose was back on. I remounted the servos with hot glue and it looked like new. Before flying it again, I ditched the cheap collets and got some better ones at a LHS.

In subsequent flights I’ve discovered half throttle is fine for takeoff. A gentle toss results in a smooth, straight-ahead trajectory with solid control. Aerobatics, while not scale are easy and crisp. As before the Twinstar II glides forever so power can come to idle on the turn to base.

fShare

Tweet