400mm wingspan with spiroid winglets. ( www.aviationpartners.com/future.html) Flat glides in the hallway hit the floor at 30 feet, or 6:1 glide slope. The hallway is only three feet (900mm) wide, so it is a testament to how straight these planes can fly that they find the floor at all. I tried a bit of twisterons (twisteron.usu.edu) on the wings but need a lot of testing to see any effect. They aren’t true twisterons, only reverse camber near the wingtips.
The spiroids are made by first cutting slightly longer winglets (about 65mm or 2-1/2 inches). Where the winglet meets the wing, cut in halfway from the back. Cut off the triangle made from the rear tip to the cut. Cut off the front parallel, so there is a strip about 8mm (5/16 inch) in width that is attached to the front of the wing. Wrap this in tape, as it is several layers of paper, and make the tape wrap extend about 10mm (3/8 ich). Now fold the strips over the wing. Take a pencil and roll up the strip parallel to the fold all the way to the fold. Remove the pencil and tape the strip to the bottom of the wing. Only the extra tape should be taped down, so each spiroid is the same length. The front of the spiroid is vertical, and spirals around to be horizontal.