building and designing a rc plane frm scratch


by kevjcarvalho
Tags: building, designing, plane, scratch
mugaliens
mugaliens is offline
#19
Dec14-09, 10:41 PM
P: 594
Quote Quote by FredGarvin View Post
Ugh. I have read those "airfoils for dummys" articles. They are horrible. Pretty pictures and graphs without a whole lot of substance.
I wouldn't design a full-scale, human-rated airplane using them, naturally! But they work just fine for scale-model balsa R/C's.

Also, it may interest you to know that I ran the dimensions of a B-52 (weight, sweep, chord, airfoils, etc.) through those "horrible" models, and the results in terms of stall speed were only 3 knots off actual. I did the same for several full-scale aircraft and achieved similar results.

So while the graphs aren't "pretty," they're pretty accurate, and certainly good enough for R/C model use.

ETA: Yes, I adjusted for the different Reynold's regimes.

AND:

Quote Quote by Cyrus View Post
I'm curious as to where you got these rules of thumb from!
WAG! My favorite flying aircraft was a Falcon 56 I built with the lower dihedryl option. That's about what it's ratios were, perhaps 1:20 for the vert stab.

Going back to the old RC modeler articles, they included formulas for calculating all of that based on overall weights, wing moments (CP vs CG, also airfoil moments), etc. Good resources - I have yet to find anything as good out there on there Internet!


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