JC's Planes and Projects

Zagi 400X with Mega Brushless Motor

Specifications:

Wingspan: 48 inches

Length: short

Weight: ? oz

Transmitter: Futaba T6XA

Receiver: Hitec 555

Servos: Hitec HS-81 (Hobbico equivalent)

Power: Mega 16/15/5 brushless with Jeti JES 30-3P controller. Best batteries are 8-cell packs of Sanyo CP-1300 SCRs.

Prop: APC 7x5 E

Modifications: Spar on top of wing (done by mistake). Plastic painted with aluminum Rustoleum paint. Two finger holds under wing for easy launch, two-color poly tape wing covering.

I really enjoyed the convenience of my electric glider and wanted to delve deeper into the world of electric flight. I am an electrical engineer by training, so all the electric stuff like motors, speed controls, and batteries, were really appealing. I had seen several Zagis at our field and had a chance to fly one. I really was not impressed with the performance, but I knew that there were hop-up options available. Also, I had a vacation in Northern Michigan coming up and I thought it would be cool to have a plane that I could take along and quietly fly in a small area.

The Zagi is unconventional, but easy to build. I think that I spent 3-4 evenings on the assembly. I made the mistake of putting the spar at the top of the wing instead of the bottom. I later read on the web that some people do this intentionally for greater strength. If I had to do it over again, I would put it on the bottom. I really don't see the need for additional strength, and a bottom location would have allowed me to carve more foam out of the battery compartment so my CP1300 cell packs could lay flat.

I covered the Zagi with purple and white poly-tape. The bottom is solid purple and the top is as shown is the pictures above. If I were to do the top over again, I would have the tape stripes parallel the trailing edge to give an arrow shape in flight. The current design with its perpendicular strips can sometimes cause perception problems - but not often. For additional aesthetic value, I painted the black plastic components silver and applied some chrome Monokote trim sheet to the leading edges. A little TLC like this can really make your Zagi stand out from the rest.

I chose the in-wing location for the RX to avoid damage and leave the battery compartment open. This has worked very well. I am not a Z-bend fan, so I used solder links to attach the pushrods to the servos. Initially, the stock motor, prop, and ESC were used. My Zagi came with the black 1700 mah brick pack that was attached with Velcro. I also marked the balance points for my 8-cell KR600AE packs, as well as my 8-cell CP1300 SCR packs.

Flying the Zagi

The day for the test flight was a fairly calm summer morning. I had charged the stock 1700 pack as well as two 600 mah packs. The test flight was done with the lightest pack - the 600AE. The Zagi was thrown into the wind, the throttle advanced, and away it went. Roll trim was fine, but it had a distinct tendency to climb under power. I feed in down trim until it tracked straight at full power. The tendency to climb is due to a thrustline problem. The motor should be canted downward to decrease this tendency. I made this change when I changed motors. The Zagi proved an absolute joy to fly. The fun does not come from blazing speed or unlimited vertical. Instead, the Zagi challenges you to do fun maneuvers that you would not try with your scale ships. Maneuvers like 1-foot upright and inverted passes down the runway, or ground effect figure-8s well within the boundaries of the field, touch and go's, or climbing and chopping the power to search for a thermal. And let's not forget formation flying or combat with other Zagis!

The 600 mah cells were good for a little over five minutes of flight. The Zagi was very light and maneuverable with this pack. It could even thermal in good lift. The next flight was with the 1700AAU pack that came with the kit. Flight times of 12-15 minutes were possible with almost no effect on performance. The bad thing about the 1700AAU pack is that it takes my Simprop charger 40 minutes to charge it. This is not real practical at the field. The 600 mah packs take 15-20 minutes. The 1700 pack did give more thrust than the 600 packs due to less internal resistance.

I really enjoyed the first Zagi flying session, but I wanted more - more flight time and more performance. I fitted the Zagi with my CP 1300 SCR packs for next session and the difference was significant. The CP packs will charge at 5-amp and be done in less than twenty minutes. They have very low internal resistance and give a nice thrust boost over the 1700AAU packs. Flights of over 10 minutes were the norm with ample full-throttle application. The 600 mah packs were soon abandoned in favor of the 1700 and 1300 packs. I flew the Zagi in this configuration for several weeks before I blew the stock speed 400 motor. I don't know why it blew, it could have been that little rain shower that I got caught in (didn't see it coming), or maybe my inverted "landing" got some dirt in the motor, but it just slowed down and cooked one flight. Off to the hobby shop for an $8.00 replacement motor and I was up flying again.

I regularly visit the E-zone and tracked long threads on the new speed 400 sized Mega brushless motors from Czechoslovakia. These motors were supposed to be powerful and cheap. I ordered one from R/C Creations in Texas. I also got the adapter, a Jeti 3P controller, and as assortment of props. Upon arrival I was very happy with the quality of the motor. It is a precision piece of work with ball bearings at each end of the shaft. With no brushes it will theoretically last forever - which is much better than changing speed 400 motors after 50 flights.

Here is the Mega 16/15/5 installed in the Zagi. Shown is the APC 7x5 E prop.

The first test flights were with Aeronaut 6x5 and 6.5x4 propellers. The performance boost over the stock S400 motor was probably 20%. In addition to the performance boost, the duration increased. That's right, more thrust from less current! Efficiency will do that for you. I knew that my batteries could handle more current, since I figured that I was only pulling 10-amp with those props. The motor is rated to 20-amp, and the ESC can take 30-amp. Time to prop up! The beauty of the brushless motors is that you can prop them for the performance you want. I went to an APC 7x5E and have flown with that prop since. I figure that I am pulling 15-amp with that prop. It turns out that the 1700AAU pack handles that load OK, but the CP1300s REALLY shine at that current and really out-perform the AAUs.

Flying the Zagi with the Mega Brushless and the CP1300 cells is a blast. It can climb out at a 45-degree angle from launch. It is capable of sustained horizontal-8s, excellent vertical for hammerheads (go up at an angle - remember no rudder!), reverse Cuban-8s, and sustained large and small loop-after-loop. All this performance and I am still getting more duration than I get out of my OS 15 powered Wonder. Typically 8-10 minutes - and a lot of that is WOT! The speed is not too great, but fast enough to make low, low, passes down the runway a blast. Particularly interesting is the raspy prop noise that you get as you fly by low at full throttle. And get this…the motor barely gets warm!

The Zagi was my go-to airplane for the remainder of the 2002 flying season. Yeah, I have a stable of bigger, faster, and more powerful airplanes, but I kept on grabbing the Zagi. I think the reason is that I was not worried about stacking the Zagi, and I could push my flying envelope further because of it. If you want to get better, you have to try new things. The Zagi has made me a better pilot. It was also very convenient for sneaking in those after work flights at the field. As the sun starts setting earlier and earlier, there is no time for fussing around. I always kept the 1700AAU on the trickler during the week so that I could head to the field, fly with the 1700AAU pack and by the time I landed one of the CP1300s was ready to go. I could get in three flights before the sun got too low. And, of course, there is no clean up afterwards. Just throw it back in the car and head home.

With the advent of these new, small, high-efficiency, brushless motors, the practicality of electric flight has taken yet another leap forward. I believe that the majority of my future projects will be small electrics - just because they are so much fun!

Sneaking in some Zagi flying before the sun goes down. Nothing beats the convenience of electric!