Friday, July 25, 2008
FlyItYourself F-22 from Nitroplanes
I got this plane to keep my Su-47 company. I already had the excellent Sapac F-22, so the bar for the Nitroplanes one to beat was pretty high. It's considerably smaller than the Sapac one, and made out of a completely different kind of foam. The foam seems to be CA glue resistant, and very tough, highly resistant to dings and damage. It's close to the indestructable EPP foam used on some models, but maybe not exactly the same. It's definitely not regular expanded polystyrene foam, but something better. The tail surfaces seem to be made of a different material, maybe sheet depron. Every single part is included...glue, a decent screwdriver, two 55mm fans with 4300kv inrunner motors, two 18a ESCs, three servos, a 2200 3s lipo battery, and a decent balancing charger for the battery. You can also get it with a transmitter and receiver included. Everything is installed, too. Construction is dead simple, but I will give you a few tips...
The ailerons and elevators are linked by pushrods. Make sure there is zero slop in the system. Make washers out of the spare control horns included, if you need to take up any slack. Make sure all of the nuts on the EZ connectors are CAed or locktited for safety. Make sure you turn your radio on and center the servos before you put the horns on, as they are hard to access once you have glued the wings on. There was a little bendiness in my ailerons due to the pushrods themselves flexing, but this has not proved to be an issue in flight. I added a strip of carbon fiber to the bottom of each stab, as they felt a little floppy, but I don't know if that's really needed...it just made me feel better. A couple of cocktail sticks would do the same job, if you don't have any carbon fiber around. I moved the nosegear steering to the inner hole of the servo and the outer hole of the steering arm to reduce the sensitivity of the nosegear. Both main gear legs have the shock-absorption coil going the same way, so one goes forward and one goes back, this works perfectly. Only three screws are provided for the main gear mounting for each side, three screws is plenty, even though there are four holes. I changed out the provided bullet connectors on the ESC and battery to Deans connectors, to make it compatable with the rest of my fleet. The bullet connectors came off with a touch of my soldering iron and went into my scrapbox for future use on something else. I used only five minute epoxy for construction. The provided contact cement works, but I don't like the stuff, and it takes too long to dry. The whole assembly of the plane took about an hour.
I used a Spektrum radio with an AR7100 RX, which may be overkill, but I had it on hand. You need to set up your radio for Delta mixing...if you cannot get the surfaces moving in the right direction, try switching the two servos into the opposite ports on the receiver...instead of left on aileron and right on elevator channels, plug the right into aileron and the left into elevator, and everything should work fine. I used the control throws shown in the manual, and used a bit of expo, which I highly recommend for the first flights. I ran the motors up slowly for the first time, to make sure the fans were balanced and to get them "bedded in" properly. There were no issues there, and they really howl. I mean, LOT of power. There are neat little blow-in doors on the bottom made out of flexible plastic, to get extra air to the fans at full throttle...they are very clever and work perfectly.
So...off to the field...
First takeoff took about 75 feet of pavement, then she was up and climbing at a 45 degree angle. She needed down trim...I flew a couple of circuits to get some altitude, then reached for the elevator trim...and switched off my transmitter instead. I did not realize that is what had happened...I thought the radio link was lost somehow. The motors stopped, there was no control, and she settled into a nice turning glide and landed in a tree with no damage. Stable airplane. Got her back down and tried again, this time without turning off the transmitter, and she flies beautifully. Quite fast, at least 70mph, with excellent vertical, great roll rate, very aerobatic. Not a difficult plane to fly, but fast and small and silver, it keeps you on your toes. Landings are dead easy, just keep a little power on and fly her down to the runway. The gear system is excellent, capable of taking some pretty rough landings. I have not tried her without the gear yet...while I think the hand-launch would be very easy, I am afraid of the landing, as the bottoms of the intakes are made of sheet plastic, I am afraid of damaging them, my grass is pretty rough.
I'm very pleased with this bird, it has exceeded all my expectations, particularly in the air. I feel no need to upgrade the motor system at all, the performance is more than adequate to me. The plane is very tough, very easy to assemble, looks good, is very inexpensive for what it is. Particularly exceptional is the performance...if you are used to EDF jets that just sort of fly around, this will be a big change for you, because this thing really FLIES. It's certainly not for beginners, but intermediate pilots will have no problem at all.