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Building Tips and technical articles. => 1/2 A building. => Topic started by: jim gilmore on May 04, 2015, 01:29:41 PM
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When looking at model airplanes. I know that the wingspan is actually from tip to tip.
But here is my question....on a model like the magician where the tips are almost half round and taper to a thinner profile than the actual wing ribs. do they really add as much to the wings span ?
Please realize I am not knocking anybody's kit or design.
My point is this would a 29" wing with a pair of 3/4 block style tips added 29" +1.5" = 30.5
Compared to a wing that seems to be 29.75"+4"=33.75".
How much difference would there be in the two examples give where the tips on the second example are mostly tapered and shaped. reducing area?
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Span means span, area means area. Tips that taper still add to the span, just less to the area.
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Without getting into too deep aeronautical engineering stuff, the tapered wingtips help reduce tip losses. A squared-off tip dumps (wastes) at lot of lift. Therefore, almost all real planes have either tapered tips or some sort of fence or device to reduce tip losses.
Area is area, regardless of the shape. A real aero engineer showed me an explanation of why with Spitfire-shaped wing, with its tips that taper to nothing, is the most effective use of wing area. But it's only slightly better than straight-tapered wings that approximate the ellipse.
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There was an article in the National Free Flight Journal many moons ago that showed a .7 tip to root chord ratio with 3 deg. washout was a VERY close approximation to the ideal ellipse. You can achieve this with proper layout of flaps at a specific flap deflection.