Design > Stunt design
Question on Imitation Flap Chord for Ted
jfv:
Ted:
I love your article on the Imitation, and have a question on the flap chord. In the article you mention that the flap chord on the Imitation was 17% at all stations. The plans for the Imitation that I have show a flap chord at the root of 19.5% and at the tip of 13.8%. My question is whether a tapered chord flap, as shown on the plans I have, has any significant difference, plus or minus, over a constant chord flap?
Thanks,
Jim V
Brett Buck:
--- Quote from: jfv on August 11, 2020, 09:40:31 AM ---Ted:
I love your article on the Imitation, and have a question on the flap chord. In the article you mention that the flap chord on the Imitation was 17% at all stations. The plans for the Imitation that I have show a flap chord at the root of 19.5% and at the tip of 13.8%. My question is whether a tapered chord flap, as shown on the plans I have, has any significant difference, plus or minus, over a constant chord flap?
--- End quote ---
Did you use the entire chord of the wing in the denominator, or just the fixed part?
Brett
jfv:
Entire chord.
Ted Fancher:
--- Quote from: jfv on August 11, 2020, 09:40:31 AM ---Ted:
I love your article on the Imitation, and have a question on the flap chord. In the article you mention that the flap chord on the Imitation was 17% at all stations. The plans for the Imitation that I have show a flap chord at the root of 19.5% and at the tip of 13.8%. My question is whether a tapered chord flap, as shown on the plans I have, has any significant difference, plus or minus, over a constant chord flap?
Thanks,
Jim V
--- End quote ---
Well, Jim V...this has proven quite embarrassing.
After digging out my article with all that data in it I can't find any way to dispute what you've brought up...even though measuring with calipers made our numbers a bit different the difference was infinitesimal in the "real world". I've tried to think up an excuse for the arithmetical goofs but failed miserably. Perhaps due to the fact that I wrote that stuff (especially the tables from which we both gleaned the data) 40+ years ago and my memory ain't remotely what it used to be! (maybe that "memory" disappeared early and that's my excuse???? y1 y1 y1...naw, didn't think you'd buy that.
FWIW, I still feel the resulting air frame as presented performed in the exemplary manner declared and the "concepts" of modest area/chord percentage of flaps, large % area tails and the aft CG those factors permit----while retaining exemplary stability and excellent maneuverability--are valid. Although I've had several pretty good airlplanes/designs during my competitive career the Imitation to this day brings back the fondest memories of a just plain perfect ship both for performance and ease of achieving that performance. If you're planning to build one I encourage you to do so; build it straight and at a reasonable weight and don't go nuts in search of the zero ounce stunter. The most flights I flew with the original were with a "heavier than most" four stroke in it that required I also add tail weight that brought its dry weight up to ~61-2 ounces dry and it never once failed to perform beautifully despite its modest wing area.
If I still had it I'd probably be flying more than once or twice a year.
Oi vey, you caused me a little embarrassment but I'll get over it. Thought it would be chicken S$#t to PM this response to you. Drop me another note when you get yours in the air and let me know how you like it.
Ted Fancher
jfv:
Thanks Ted. Actually, I'm putting my own design together with basically an Imitation wing layout, only slightly smaller. I like the looks of the Imitation flaps better than the constant chord flaps and that's why I asked. The Imitation is on my build list though.
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