Stuka Stunt Main Forum · 9 of 9 known posts recovered
The main thing is, if you're just starting out, don't be too jealous of those flapped planes - have fun first, and learn!
Oversimplifying, flapless stunters are easier to
trim, and flapped ones have more lift in maneuvers and
much less tendency to "wind-up." They generally
fly "smoother" too, and handle wind better.
I have only flown one flapped plane, the Twister.
I thought it flew better than anything else I
had previously flow. But I made the mistake
one dead calm day of flying into my own
wake turbulence, and the plane was history.
In the words of Homer Simpson, DOH!
One main conclusion is smaller flaps allow sharper corners while rounds are easier to groove with larger flaps.
A well trimmed well designed non flapped plane i.e. Flite Streak is capable of performing a good 420-450 point pattern but is not capable of performing an expert 520-560 point pattern.
I wouldn't be so sure about that.
It is true that a single Expert, on one hand flying his own PA model, on the other flying a nicely-powered ARF Flite Streak, Primary Force or SIG SkyRay, will not equal the performance of the former, the differential is a lot closer than you seem to think.
What is really interesting to me is that as one takes this same thought to the ranks of Advanced fliers, in a great many cases the differential would be zero, dropping to Intermediate the simple model will easily out-perform the flapper, and no one who really qualifies for Beginner should ever handicap himself with a flapped Stunt model.
Dan
Dan
Camber flaps can increase lift by around 50%. Using this extra lift incures an induced drag penalty. If you don't uses the extra lift, there is a reduction in profile drag. Flaps do move the centre of lift more rearward but this is not too serious for C/L because the flap is tied to elevator so at low AOA, the flap is near zero and centre of lift is near that of a symetrical section. At high AOA, flap extended, the centre of lift is forward, approaching the wing aerodynamic centre as for a cambered section, again not too different than an unflapped wing.
So centre of lift and therefore pitching moment is not very different than for an unflapped wing or at least not as different as would be the case with independant controls. That said, there is some centre of lift and pitching differences so a larger tailplane and rearward CG is required to maintain the same CG to centre of lift distance and static margin (stability).
Comparing models that have been designed with this in mind, the flapped model will pull tighter loops. In practice, comparisons are confused because there are other variables. It is not a simple matter of just adding flaps.
Flaps can allow a thinner section to be used to reduce drag while maintaining the same lift. Roughly, we might reduce the section by 30%.
Total drag might be reduced by 10%. The increase in speed could not be expected to be more than 5%. That's a pretty rough off the cuff estimate though.
Regards,
Ken
They enable an airplane to turn tighter for a given wing loading than it would without flaps.
They enable an airplane to have less response to turbulence than it would without flaps, because they enable it to have a higher wing loading for a given turn radius.
They provide direct lift control, which improves the airplane's dynamic response, making it easier to fly accurately than an airplane without flaps.
They require less angle of attack for a given turn radius than does an airplane without flaps, so the airplane points in the direction it's going. When properly trimmed, an airplane can give the illusion of flying a path closer to the prescibed maneuver than it's actually flying."
Somebody pointed out that the last statement was dumb, so I rambled on:
"Saying that the airplane points in the direction it's going is at least an oversimplification. For a given wing loading and loop radius and reasonable airfoils, an airplane with flaps will have less body angle of attack than an airplane without. Phil's Giles has less wing loading than most flapped planes, so I can't say that it operates at less angle of attack than my flapped plane. The angle of attack of a flapped plane of a given wing loading flying a given loop radius can be tweaked by adjusting the flap-elevator ratio, though, so it may be easier to trim to achieve the illusion I mentioned above. A flapped airplane can do a loop at a negative angle of attack if you have sufficient ratio of flap to elevator and enough aspect ratio."