Weather finally improved enough for me to maiden my first FMS Alpha jet cheap foamie rc conversion. My first attempt at converting a light foamy jet as opposed to the several+ Lidl foamies I've built. Flight went extremely well but a bit of a handful! Still needed a bit of trimming or maybe CG change and I'd be interested to hear opinions on what might have been wrong, (apart from my lack of piloting skills). My 1st thought was tail heavy, but as you'll see on the video it might have actually been nose heavy? Research says nose heavy? It was a bit of challenge to fly but came home in one piece and It'll be interesting to see if my CG change will make much difference next flight.
Blisteringly good maiden for My FMS Alpha RC Build, but could be better maybe?
- Thread starter Bonzofly
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- fms alpha rc build
Thanks. Definitely needed more expo and smaller throws. I moved CG about 10mm futher back, though we have yet another named storm this weekend so it might be a while before I get a chance to test fly again. It's all part of the fun sorting out these rc conversions though!
Michael9865
Elite member
I have used and had good results with this cg calculator before. https://www.ecalc.ch/
Hi Michael, It's a useful site and I have that bookmarked already and have used it before. This is my 1st ever swept wing RC conversion, so beyond my previous experience. I did a few calculations, but was hoping I might learn some advice from someone who'd built one. I've seen a couple of suggestions on other forums.
quorneng
Master member
It turned to the right on the first launch. Not that surprising from the motor torque. You added some left trim but it sounded like quite a bit!
On the second flight it tended to turn left. Too much left trim? You noted the sudden un commanded roll but it was at the top of a slow climbing turn. Classic wing stall and when a swept wing stalls it tends to result in a dramatic roll as well as pitch down.
Less left trim and some left motor thrust angle and it should fly well enough. With its fighter jet fuselage the motor is a long way ahead of the CofP so it won't take much left thrust to neutralise the effect of motor torque.
That's what I would do.
On the second flight it tended to turn left. Too much left trim? You noted the sudden un commanded roll but it was at the top of a slow climbing turn. Classic wing stall and when a swept wing stalls it tends to result in a dramatic roll as well as pitch down.
Less left trim and some left motor thrust angle and it should fly well enough. With its fighter jet fuselage the motor is a long way ahead of the CofP so it won't take much left thrust to neutralise the effect of motor torque.
That's what I would do.
Hi quorneng thank you for your fine detailed analysis , the roll was interesting for sure! And comments about thrust etc. Needs a few more test flights, smaller throws, more expo and I have moved CG futher back, so I'll see how it goes next time and if necessary then maybe change motor thrust. It was my first venture into trying a swept wing rc conversion and to be honest it went far better than I could have hoped for. It'll be interesting to see how my next flight test goes. Watch this space!