Carl Goldberg Falcon 56 MKII Conversion

I built the Falcon about twenty years ago and outfitted it with an OS .40 engine and flew it quite a bit. I had great times out in a big field by myself until the field sprouted houses and the Falcon went into the closet for other activities. When I got back into RC a few years ago, I threatened to dust off the Falcon and fly some more, but the equipment was so old and I really didn't want to mess with that engine again so I got the bright idea to electrify it! Well, I'm sorry to say that I have had less than stellar results so far... The electrics are expensive and it uses a much larger battery than the little park flyers. The airplane structure was built for glow power and is kind of heavy. Adding the big battery and motor didn't help. Anyway, the first flight (electric maiden) found the airplane doing more grass cutting than sky carving. Nearly 1/3 up elevator was required for level flight. Also, there was a strange noise about a minute or so into the flight, which turned out to be a loose motor. I lost three of the four bolts that secure the motor to its mount in the air! That was a close call. I had forgotten the loc-tite. Well, it was back to the shop for the old bird to increase the wing incidence and find some new bolts for the motor. With that all straightened out it was time for the second "maiden”. After performing a complete system's check and a range check it was time to see what it could do. The change I made to the wing mount helped a slight bit but it still wasn't right. I soon had another, much more serious problem. The radio was very slow to respond and then after a quick decision to bring it back in, the radio gave out completely just as I entered my last turn before my final approach. The airplane went in from about 100 feet at about 2/3 throttle. The damage wasn't all that bad actually. The wing popped off with only a split in the covering, and the tail separated from the fuselage pretty cleanly. The fuselage was a little munched at the nose, but the big problem was that the Lipo battery suffered an internal short due to the trauma of the crash and began to burn; billowing out white smoke. It took several minutes just to be able to remove it from the airplane. It left the inside quite charred and destroyed the speed control. Take a look at the pictures below. I was able to remove and replace the bad wood and broken bulkheads and rebuild it. I also added three degrees of incidence to the wing and shortened the nose about 3/8" and added a neat air-scoop to help with cooling.


My determination of the cause of the crash is that I used too large of a battery for the speed control’s circuit that powers the receiver and it was not able to get the power it needed to run the servos. This also greatly reduced its range. The circuit is temperature dependant so it was fine when it was cool on the ground, but when it was flying and working hard, it over heated. I have since bought a new Spektrum DX7 radio and have installed their AR7000 receiver for mid size airplanes and will be using a separate battery to power the radio. That should eliminate that problem. I hope to re-maiden (third times the charm) next month and hope to post the results and new pictures. Wish me luck. This is a sweet old bird and deserves to be up punching holes in the sky again.

 

Specs are as follows:

Below are some photos: