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Sep 05, 2017, 10:40 AM
What could possibly go wrong?
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Possible Trainer 60 flaps


Hi, just a couple of ideas for possible flaps to add to my RCM Trainer 60. This was to be used in a PM then I reaslied I can't attach pictures to those. First image is a simple modification to my existing wing - split the ailerons into two sections, the inboard being shorter span and will be the flaps. I'd add an extra servo in each wing panel to control them, for a 4-servo wing, meaning I can run them as separate flaps, or together with the ailerons to restore the original aileron surface aera.
2nd versions, B, I'd only use if I were building a whole new wing for the trainer, which is actually a possibility. If I had a workshop area set up and ready to go it'd be so much easier to take on more of these projects, but as it is that's a little hard. Anyway, ideally I'd like more area for the flap surfaces, this is one way I can think of to do that. I'd also take the opportunity to mount the flaps' servos inboard in the wing centre section and drive them with torque rods. The main reason for that is to keep as much mass as possible inboard in the fuselage area, rather than out in the wing panels. I've read that you want as littlle mass out there as possible, I won't bother going into the reasons here but it should be obvious at least as far as angular momentum.

In the next image, version C is a possible improvement on A, which I could do relatively easily on the existing wing. The problems I see are lack of effective area for the flaps, so they're more like air brakes than a lifting surface, and loss of area for the ailerons. StayQuiet did mention that he saw a lack of roll rate with his ailerons and had to increase their throws, so I thought this way would restore some area. But I don't know if it's just asking for other problems. Firstly, it increases the overall chord of the wing and reduces aspect ratio. My wing already has extra span (one more rib/bay each panel for a 6" total increase), so this might wind up with about the original A.R., but even more area. That's probably OK in itself, if anything it's got higher loading than most high-wing trainers so I wouldn't mind if it had to end up reduced. I'm more worried about the taper altering the characteristics of the wing into something undesirable. I don't know how to predict what'll happen, I just hope it's nothing bad.

If I did do this I'd prefer to have the sevos inboard as I mentioned, in the reinforced, fully-sheeted centre section, which is pretty strong already. The more important alteration would be to drive the flaps using torque rods instead of pushrods like the ailerons.
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Sep 05, 2017, 11:29 AM
AndyKunz's Avatar
Yes, you'd need to make a whole new wing. I suggest keeping it simple and just splitting the aileron. I prefer doing that to either B or C.

The construction will be much simpler if there is a common hinge line for the whole span. It will be a stronger wing, too, less likely to cause flutter.

Andy
Sep 05, 2017, 12:17 PM
What could possibly go wrong?
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Originally Posted by AndyKunz View Post
Yes, you'd need to make a whole new wing. I suggest keeping it simple and just splitting the aileron. I prefer doing that to either B or C.

The construction will be much simpler if there is a common hinge line for the whole span. It will be a stronger wing, too, less likely to cause flutter.

Andy
Hmm, yes a common hinge line certainly would be an advantage, I hadn't thought of it in those terms. So I guess the advantage of extra area for version C isn't enough to offset the effort and possibility of problems. Those problems as I see them are to do with what I've read about loading, and where and how the wing stalls. It's too unknown for me to just go ahead with it. C at least means the wing structure doesn't have to be touched, but this is a known design and a good one, I don't really want to mess with it. I'm having success and fun with it after investing a lot of time into it, so the sort of mod's I should be considering wouldn't alter the formula too much.

That said, I'm wondering about fully cowling the engine, and I've got a larger Saito that would normally fit right onto the same engine mounts, but the FA-82B's carby doesn't clear the firewall. I'm hoping to get the same engine mount and drill it for the other engine so it's a straight bolt-in swap, then correct the CG. As I continue to improve my flying I'm starting to wish for extra power for certain maneuvers, and I'd love to clean up that nose so that with more power and prop pitch it goes *fast!!* I just think that would be fun. But that little FA-56 on it now does a fantastic job. I thought the power might be marginal but it's not, I guess it's probably more the mid-RPM torque available than overall HP. I'm rarely at full throttle, and it can accelerate well from any position. For example, yesterday I decided to abort a touch-and-go and I found myself just a metre off the ground with the model at almost 45 degrees. I was worried it might not work out, but I pushed the stick to WOT and up she climbed, no problem. Got out of trouble quick smart. That engine has great response, thanks to some good tuning advice I've been given, and spins up beautifully, almost as fast as you can work the stick. I can do a large-radius Immelman and it doesn't struggle at the top, even without a dive to build up speed first. Where I'd really like some more is so I can use a little vertical climb sometimes, not so reliant on momentum.

But, never get the idea that this model, or engine, lacks for anything. For a high winged trainer it's terrific and I love it. All these ideas are definitely for after the "training" stage, never forgetting that you should always be learning, as with anything. The same engine's earmarked for my Venture 60, and maybe that will satisfy me, but I think I'll always want to fly this one too. It's too much fun to stop flying it!


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