1/13/2024 0 Comments Helicopter airfoilI've been thinking of using a flat-bottomed airfoil for a super simple trainer - I know they get bad press but how bad can it be?Ī trainer? Most all of the commercial "trainers" kitted since 1955 have a flat bottomed airfoil. Originally you wrote, "Flat-bottomed Airfoils - how bad? So do yourself and everyone else a favour and fine tune the CG to a point where the model is stable but still nicely mannered. But what happens is that the model becomes so speed to pitch sensitive that even good pilots hate flying it and beginners are stumped by this "thing" that seems to be possesed. It DOES have everything to do with the fact that a lot of folks automatically figure that if having the CG a little forward is good for stability then putting it WAAAAY forward is just right for a beginner. Such a reaction has very little or nothing to do with the actual airfoil. And really all that is needed is to set the CG to where the model has a nicely balanced tendency to lift the nose in a dive without it over reacting. A model that wants to lift the nose strongly due to a buildup of speed in a dive will soon get a bad rap for wanting to "balloon" all the time. A strongly stable model seems like a good idea at first but as noted beginners tend to be sloppy on the dives and climbs. One thing I would suggest is after the prototype model is done tune the CG location to produce a nice solid positive pitch stability but don't make it TOO strongly stable. So sure, go ahead and use such an airfoil with a clear conscience. But that's just what a beginner needs to avoid the model speeding up a lot when they inevitably dive coming out of turns or during turns. Such an airfoil will produce buckets of drag when you try to fly it fast. But on a primary trainer I can't imagine anything that would be much better. Sure, the airfoil you're talking about is rather dismal due to drag for some uses. The needs of a trainer, competition sailplane, racing model and world class pattern model are all different.
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