Fun formula for design

LAST EDITED ON Dec-18-03 AT 07:06 PM (CST)
 
Just to get a feel for the intermediate size stunt model areas, I plotted up a bunch of different successful designs, and darned if they didn't fall in a pretty good order! For a model of average wing loading FOR ITS SIZE, the formula is:

Wing area = 186 + (940 x displacement)

so for a .15, Area = 186 + ( 940 x .15 ) = 327 sq.in.

+10% for a light model, and -10% for a heavy one. Simple, no?

The models used went from the Pinto to LA Heat with some popular .35, .40, and .60 models in-between.

The ARF Flite Streak surrounds this line when you go from a .19 on one side to a .25 on the other.

Larry-

This is a neat idea and could have answered several questions posted here recently - at least within the ballpark. It is interesting that you chose a straight line as the best fit curve for your data, but since we most often run detuned engines, a theoretically based choice of curve shape might be futile anyway, especially as power varies as the cube of the speed. I wonder though whether the areas aren't a bit low for larger, newer engines, especially for high-reving, low-pitched .25's, which probably fall outside your 10% margin. In your opinion, whould it be useful to set different equations for "modern" or perhaps Schnurle types run fast vs. "old" and/or flapped vs. unflapped - or is that just too much fuss? I'd enjoy reading your comments on assumptions you made concerning the various designs and engines.

SK

Basically, I took the data I could easily find on RSM and Brodak's sites, and plotted the wing area against the probable engine choice.

For more modern, higher performance models, you would, indeed come up with a different line. I was surprised to see it so linear, I figured I would at least need log paper to get something sort of straight. It does curve sharply downward at the low end, and in fact, I did a whole new chart for .010 (Heydon's Lil Bit) through .06 size models (Baby Pathfinder and Meek's P-51)and got a completely different formula:

Area = 53 + ( 3450 x displacement )

Rather a different slope to the curve, nearly 3 times as steep!

The small models are not as highly developed as the big ones, so the data is pretty unlikely to represent optimized models. Garbage in, garbage out