Howard Fink — My Paper Airplanes Paper Airplanes

The tapered wings mentioned in the spiroid posts lends itself perfectly to blended winglets.  http://www.airportjournals.com/Photos/0212/X/0212004_2.jpg

The lack of sharp corners and thin tapered wings reduces both induced and parasitic drag.  This plane stays up.

First flight test:  I was able to fly figure-eights and have the plane return to my hand.  “Wow!  Good job!” from a passerby.  Launches into the wind gain about twenty to thirty feet of altitude; the plane  holds the wind well, flies steady and straight into the wind  and flies very fast downwind.  Plane recovers nicely from building hits.  Dihedral should be a little more than in the picture above.

I’ve tried two versions of the blended winglet:  taper in front and taper in back, and the taper in back, straight-up front flies better.

Here is a version integrated into the design.  I triangulate the front end, taper fold the leading edge, and leave about an inch and a half for the winglet.  This is cut on the bias, so the front cut meets the wing at the halfway point of the width of the winglet.  The rear cut is parallel.  Roll this up and the tip of the winglet is attached at the front, and the rear remains attached, creating a spiral.  I added launching gear (retractable) for overhand throws and display.

With a traditional barnaby,

the paper is folded in half both ways to establish the keel and the leading edge.  The winglet is just as thick as the leading edge.    The paper for the spiroid is folded on a diagonal, corner to opposite corner, then trimmed for symmetry (a diamond).  The leading edge is folded up from a wide corner, so the narrow corners become the wingtips.  There is only one or two thicknesses of paper there.  A ribbon curl, tape to hold the tip to the wing, a diagonal cut, and a spiroid.    It is not completely there, as the true spiroid has a slightly more complex shape.

The proper shape for a spiroid.   I apologize for the out-of-focus.

The photo below is tricky.   The narrow part is at the rear, the wider part at the inside, attached to the wing with a sharp fold up. 

Figure from patent, Spiroid-Tipped Wing, # 5,102,068 issued to Louis B. Gratzer, April 7, 1992.

The plane was made using a traditional fold of half in each direction.  Unfolded, I folded in the corners at the front, cut them off, and tucked them in when folding up the leading edge, to get the weight up front.  The wing is thick in the center and thin at the ends.  The wingtips were rolled up on a pencil and a tab was taped to the wing.  Then the cylinders formed were trimmed into a spiral.    Spiroids.

The flight test was quite successful.  After some adjustments for trim, it was clear the plane flew with great authority, righting itself quickly, with long glides to a landing.    My sense is the spiroids are riding the vortices shed at the wingtips.

Spiroids

Spiroid Winglets, which look like a large loop of rigid ribbon material attached to each wingtip, cut fuel consumption by 6% – 10% in cruise flight. Initial flight tests of the Aviation Partners Spiroid concept on a GII reportedly reduced cruise fuel consumption by more than 10%. Stay tuned for more developments on this promising technology.

http://www.aviationpartners.com/future.html