Millions of paper airplane designs exist; every kid seems to know a different one. But by far the best paper airplane I have ever flown was taught to me by my dad, who learned it from his dad when he was a kid in the 60's. In fact, my grandpa invented this design (he was a draftsman, an airplane mechanic in WWII and the Korean War, and holds several patents). So I made this sound like my family's secret paper airplane legacy, but we've taught it to tons of people over the decades so it can hardly be called a secret. Now I'm going to teach it to you.
One more thing: This instructable is an entry in Paper Airplane Contest 3 (http://www.instructables.com/community/Paper-Airplane-Contest-3-Open/). <--- check it out !
Step 1: Materials needed....
That's it. This isn't one of those fancy cut-cut-tape-tape-fold-fold paper airplanes; this is pure old-fashioned paper folding.
If you are fanatical about your creases, you could also use the edge of a ruler to run along them, but your fingers should do well enough for most people.
Step 2: Construction - Step 1
Step 3: Construction - Step 2
Step 4: Construction - Step 3
Repeat with the upper left corner. [Pic. 2]
Everything should be lined up as close to perfectly as possible. Exactness counts.
Step 5: Construction - Step 4
Step 6: Construction - Step 5
Repeat the last fold in reverse with the upper left corner. A downward pointing triangle should be visible below the points of the last two folds [Pic. 2].
Take this triangle, and fold it straight upward, over the touching points of the last two folds [Pic. 3]
Step 7: Construction - Step 6
Fold the first wing down [Pic. 2]. It should be slightly at an angle from the keel of the plane body (the part formed by the reference crease), tapering toward the front of the plane. A good rule of thumb is that the keel should be a quarter inch tall at the snub nose, and 3/4's of an inch at the tail. I know this sounds confusing, just look at the fold marked in red in Pic. 3 and hopefully what I mean will be clear [Pic. 3].
Make an identical fold on the other side to make the other wing [Pic. 4].
Step 8: Construction - Finished
Now you can experiment with flying this resilient little guy, or you can continue reading this instructable to garner a few hints about achieving stable flight, a loop-de-loop, and a wingover maneuver (all requirements for the Paper Plane contest 3).
Step 9: Flying - stable flight
To throw it, use a standard paper airplane grip (I don't know how to explain it any simpler than that :-) [Pic. 2] and give it a gentle, level, throw.
Step 10: Flying - Loop-de-loop and Wingover
First I fold a set of flaps in series on both wings that are set at two angles (one shallow, one steeper) to get that nose up [Pic. 1]. Getting the angles of the flaps just right can take a few trys, so to aid you I've taken a picture to help show the angles that worked for me [Pic. 2]. With the flaps shown in profile it appears that the first (wider) flap is angled at 5-10 degrees, and the second (narrower) flap is angled 10-20 degrees from that, for a total of 15-30 degrees across both folds.
Secondly I put a medium-small paperclip about 2/3rds back on the plane body, to help balance out the heavy nose and allow for faster and better maneuvering [Pic. 2].
Loop-de-loop: For the loop, make the above mentioned folds, then grab the plane how you would normally and make a level throw as you would for straight flight, but with just slightly more force (gotta force that nose up). With proper force, planes made on heavy paper will achieve small loops and planes on lighter paper will achieve medium loops.
Wingover: I was surprised to find this out (I'd never tried a wingover before this contest) but to achieve a wingover with this plane you don't need to make any physical changes to the design or flaps from what you did to achieve the loop. Keep everything exactly as you did for the loop. To do a wingover, you just have to throw it differently. Instead of holding the plane upright (so the wings make a "Y" when viewed from behind), cock it slightly to the left such that the left wing is parallel with the floor (horizontal). Now throw the cocked plane straight ahead, level with the floor, and instead of performing a loop it will pull up and to the left until it stalls, turns around, dives, and then pulls out facing 180 degrees the other direction - the perfect wingover.
Hopefully this simple plane provides a bit of fun for some kid somewhere, just as it has for me over the years. And who knows, maybe it will win a contest for me too :-)