Stephen
Senior Heliman
Location: Hong Kong
| Hi folks,
Though I had been moving as many 3DNTs as I can get, it was until yesterday that I had the first flight on my own 3DNT. Let me tell you, to see is to believe, but to fly it myself is so much more fun!!!
Despite of my flu and uncontrolable work schedule, I managed to steal an hour 2 weeks ago to start up the flight ready 3DNT and on 4 tries, I couldn't lift it off. First 3 goes resulted in the 3DNT lying on its side with stripped cyclic servo gears and the fourth time even a boom strike.
What happened was that the 3DNT was placed on a granite floor and it developed some kind of resonance at 800~900 head speed to an extent that it vibrates badly and jumped off the skid and tried to destroy itself. Rapid exchange of email with Jan Henseleit confirmed that I should either lift off as soon as the vibration develops or try lifting off on softer ground. I had not experience with lifting off the 3DNT at all much less at 900rpm and did not want to risk loosing tail control altogether so I had my machinist made a set of cross members for the skid and retried yesterday on grass land.
There were still visible vibration during the 800~900rpm range but the heli did not jump off the skid anymore. I had my Webra 91 filthy rich as it was new, governor set to 1,300 normal, 1,500 idle up 1 and 1,650 idle up 2 with +/- 11 degree pitch in both idle modes. No exponential or dual rate any where.
First impression after lift off was that the helicopter was amazingly smooth, just sitted there waiting on control inputs and not jerky or touchy at all at 1,300rpm. Given the amazing stability, I though I might just try lifting off at 900 rpm as Jan suggested. I sat down the heli, waited till it spooled down and spooled up again, just as the vibration started, I push the collective up. The Webra with the rich mixture complained loudly but the 3DNT lifted off without the slightest hesitation and the tail was locked in real nice. So solid ground or not, with or without skid cross members, lack of experience on my part caused my earlier problems which will not repeated itself again.
After a couple of tanks, I leaned out the Webra by a tinny winny little bit and go into idle up one. Did some loops and rolls and smooth circuits because of the state of the engine, by the end of the thrid tank and a couple full pitch climb outs, I was tic-tocing up and down at 1,500 rpm. I must say this is something that I had never imagined before. If I have anything less than 1,750rpm on another helicopter, I would not even attempt such a move. What I experienced was that the 3DNT did the tic-toc at 1,500 rpm just like my VisionX at 1,900rpm but without the jerkyness and the noise.
I have not gotten into idle up 2 yet and will try after another gallon or so. But so far, I am more than impressed, I am actually amazed. The 3DNT is not really a day to day machine for me but I am quite sure that in between email responses, my Fury and VisionX and zillion other little things, I will take it up for a tank or 2 whenever I can, it is so graceful that to me, the 3DNT will do what soft music do to most others, get me relaxed!!!
Needless to say, not too many people got their emails replied to yesterday :-)
Now that I have some experience on the moving flybar system under my belt, I will start up my Webra 145 equipped Rocket in the near future.
Lastly, time your flights!!!! There is no way to install a visible header tank or visually check on fuel level. Also, paint your canopy as bright as possible and DON'T use black for the windscree area. Use a contrasting bright color.
My 3DNT set up:
-Latest generation 3DNT right hand rotation kit (ex-factory 11/02)
-Webra 91AAR clockwise rotating engine (clockwise one-way start shaft from Henseleit used)
-Hatori 700 pipe at 450mm
-GY601 w/S9251 gyro
-S9206 on the cyclic, going to change to 9350
-710mm Modelsport 3D Competition Pro main blades
-102mm Modelsport tail blades (this is not recommended but I cannot refuse the temptation)
-Weston UK 5% nitro 7% oil competition fuel
-GV1 governor
Stephen |
I've just bought the OS91 that Jan recommends and I'm going to give that a go to see if it is any better. I had no confidence in the Webra as it keeps stopping - usually on lift off after flying round for a bit and then taking a minutes rest. The engine isn't running hot. It has stopped twice in flight. I think it is getting too rich in the mid-range but playing with the needles brings vibrations. Too much fiddling and not enough flying was getting me down. Hopefully the OS will be less troublesome even if it is less powerful. I'm sure it'll be enough for me for now.
