Howard Fink — My Paper Airplanes

January 29, 2013

Another C Wing

Filed under: Uncategorized — @ 11:36 am

big-c-wing

The previous plane was made from legal size paper, 8-1/2 x 14 inches.  This plane is made from 11 x 14-1/4 inches paper, or a scaled-up size from 8-1/2 x 11 inches letter-size sheets.  The folding technique is the tapered wing style.  In tapered wing folding, you fold in half each way to start, then fold over the two front triangular corners and cut them off with a scissors.  Flip and rotate the pieces and place them to match the remaining triangles on the forward section of the sheet.  A small piece of tape at the center of the sheet to hold everything in place, then fold over the very forward tip about an eighth inch, or 3mm.  Keep folding over and over until you reach the long fold that will be the leading edge of the wing.  Run a strip of tape along the trailing edge of the fold to keep it closed.  Press down hard on the fold to flatten it.  The wing is now thick in the center and thin at the ends.

Cut out a barnaby shape from one side.  Take this cutout and mark the other side.  If you attempt to fold the plane is half, the center fold will crack.  This extra thickness in the center keeps the plane stiff in flight.  Fold in the ends about an inch and a half, and then fold over.  Unfold to make the C wing ends.

c_closeup

I like to take a snip about a quarter of the way in at the end of the wing to give the trailing edge more room for camber.  Finish off the barnaby as usual; just be careful to balance the folds of the tail.  I usually run strips of tape where the fuselage curves, to give it extra stiffness:  a strip of tape along the keel will also help.

This flies much better than the yellow-pad legal-size plane.  Capable of tight turns, adjustable to wide turns, very sensitive in roll (be careful balancing the plane, the control forces do not scale linearly with speed, so only small adjustments).  It should be fine indoors and out, but looks to be happiest out-of-doors.

January 12, 2013

C Wing airplane

Filed under: Uncategorized — @ 9:54 pm

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960023622_1996039477.pdf is a 1995 paper in which a genetic algorithm was set to design an airplane wing of fixed lift and span, minimizing drag.  The result after 120 iterations was the C wing.

c_wing

c_wing_front

This uses a legal-size sheet of 16-pound paper. ( 8-1/2″ x 14″ or 216mm x 355.6mm and 60 grams per square meter).  The full sheet of paper is 4.6 grams, or about 4 grams for the completed airplane.  The rolled leading edge taped flat and folded is enough structure to keep the upper horizontal surface of the C wingtips relatively flat. The fold needs to be refreshed to remain horizontal.   This plane flies quite well, with a L/D of 6 or more.  No flutter when flying in circles or in glides.  The original Barnaby glider had a full wingtip fold instead of a winglet.  Who would have thought in 1908 a second fold would be a breakthrough in aerodynamics in 1995?

A small cut about a quarter of the way in on the initial folds that create the vertical wing panels allows the trailing edge of the wings more camber, which improves the L/D to 7.  In addition, this provides more adjustment of the wing loading, which must be equal in order to fly in circles and return at the same altitude.

January 11, 2013

Double Box Tail Paper Airplane

Filed under: Uncategorized — @ 1:01 am

boxtail

http://www.synergyaircraft.com/ describes a new concept in aircraft:  the double box tail.  I looked at the test flights of the model, and thought the Barnaby platform could be so modified.  Starting with a legal size sheet of paper it was possible to make a double box tail aircraft.   The winglets are an extension of the wing and have two folds.  The upper surfaces are single thickness (no leading edge thickening with rolled up paper like the wing) and are stiffened by a longitudinal fold for the elevator effect.  They are cut at an angle to meet the upper rear edge of the winglets.   A bit of tape top and bottom attaches the tails to the winglets. This version has too much surface area, which results in a high sink rate, but it flies in circles and returns to the hand.  The upper surfaces are truly tails, with the rear edges deflected up like an elevator.

boxtail-top

boxtail-front

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