09-08-2020, 08:33 AM
|
 |
Mad for modrocs
|
|
Join Date: May 2019
Location: Chapel Hill, NC
Posts: 71
|
|
Quote:
|
Originally Posted by olDave
Is there some reason that you are fixated on this particular planform? I mean, do you just like the looks, or did someone steer you onto this as being the "best" way to go? Not trying to be ugly here, just wondering why.
The fabled elliptical wing planform is a somewhat clumsy way to approximate an elliptical spanwise lift distribution to strive for minimum induced drag on a real aircraft. The same spanwise distribution can be achieved with a constant-chord wing planform by varying the airfoil section along the span, or can be quite closely approximated by using a trapezoidal planform with taper ratios of 0.10 to 0.30. Several ways to get there--
And all that theoretical aerodynamic stuff goes right out the window when you are working with model rocketry stuff at very very low Reynolds numbers. A flat plank (no airfoil at all) with a simple planform shape works just as well. Think in terms of insect wings.
|
I chose it primarily to reduce tip vortex drag, and because I've constantly encountered comments that the Spitfire's planform was an extremely efficient one for subsonic aircraft (yes, I realize that the Spitfire wing is actually made up of two slightly different ellipses, but I didn't want a carbon copy of it). And I admit I like the looks of a Spitfire-type wing and it's efficiency.
It's beginning to look like it's more trouble than it's worth though, and I may just abandon my shape and use a truly elliptical planform, or give in and use a plain rectangular planform with square tip chords, which all the online calculators appear to support.
__________________
“I would like to die on Mars. Just not on impact”. — Elon Musk
“Minds are like parachutes--they only function when open”. —Thomas Dewar
|